REGISTER  |  SIGN IN
United States Patent6351773
Fijolek , ; et al.February 26, 2002
Title
Methods for restricting access of network devices to subscription services in a data-over-cable system
Abstract
Methods for providing restricted access for a network device such as a cable modem or customer premise equipment on a data-over-cable system. An unknown or new network device is assigned a restricted network address such as a restricted Internet Protocol address. The restricted network address allows the network device to access less than all of the available features on the data-over-cable system. A connection timer is started on the data-over-cable system for a restricted connection to the network device. The connection timer restricts access to the data-over-cable system over a timed interval. A restricted connection is created between the data-over-cable system and the network device including the temporary restricted network address and the connection timer, thereby providing restricted access to the data-over-cable system over a timed interval. The methods may allow a data-over-cable system to provide restricted connections to unknown or new network devices without a long delay, yet provide security to the data-over-cable system.
Inventors:Fijolek; John G. (Naperville, IL), Gun; Levent  (Lake Forest, IL), Lee; Ronald B.  (Northbrook, IL), Robinson; Philip T.  (Barrington, IL)
Assignee:3Com Corporation (Santa Clara, CA)
Appl. No.:217534
Filed:December 21, 1998
Current U.S. Class:709/228 709/222 
Current International Class:G06F 11/00 (20060101)
Field of Search:709/201,220,222,224,228,227 713/201 370/19,10
U.S. Patent Documents
4644533February 1987Braff et al.
4881263November 1989Herbison et al.
5014234May 1991Edwards, Jr.
5138712August 1992Corbin
5442749August 1995Northcutt et al.
5489897February 1996Inoue
5598410January 1997Stone
5610910March 1997Focsaneanu et al.
5623601April 1997Vu
5678041October 1997Baker et al.
5710885January 1998Bondi
5761602June 1998Wagner et al.
5778181July 1998Hidary et al.
5790198August 1998Roop et al.
5790548August 1998Sistanizadeh et al.
5790677August 1998Fox et al.
5790806August 1998Koperda
5799086August 1998Sudia
5805804September 1998Laursen et al.
5809252September 1998Beighe et al.
5812819September 1998Rodwin et al.
5818845October 1998Moura et al.
5819028October 1998Manghirmalani et al.
5819042October 1998Hansen
5828655October 1998Moura et al.
5828666October 1998Focsaneanu et al.
5835720November 1998Nelson et al.
5835727November 1998Wong et al.
5841777November 1998Cohen
5848233December 1998Radia et al.
5852721December 1998Dillon et al.
5854901December 1998Cole et al.
5859852January 1999Moura et al.
5864679January 1999Kanai et al.
5870134February 1999Laubach et al.
5872523February 1999Dellaverson et al.
5884024March 1999Lim et al.
5903558May 1999Jones et al.
5913037June 1999Spofford et al.
5922049July 1998Radia et al.
5922051July 1999Sidey
5943604August 1999Chen et al.
5954797September 1999Sidey
5958007September 1999Lee et al.
5974453October 1999Anderson et al.
5991292November 1999Focsaneanu et al.
5991306November 1999Burns et al.
5996076November 1999Rowney et al.
6003077December 1999Bawden et al.
6005851December 1999Craddock et al.
6006264December 1999Colby et al.
6009103December 1999Woundy
6012088January 2000Li et al.
6013107January 2000Blackshear et al.
6014545January 2000Wu et al.
6018767January 2000Fijolek et al.
6031841February 2000Woundy
6041041March 2000Ramanathan et al.
6049546April 2000Ramakrishnan
6049826April 2000Beser
6052724April 2000Willie et al.
6058421May 2000Fijolek et al.
6065049May 2000Beser
6070242May 2000Wong et al.
6070246May 2000Beser
6073178June 2000Wong et al.
6075787June 2000Bobeck et al.
6091709July 2000Harrison et al.
6094431July 2000Yamato et al.
6130880October 2000Naudus et al.
6137793October 2000Gorman et al.
6157965December 2000Mohammed et al.
6170061January 2001Beser
6185624February 2001Fijolek et al.
6189102February 2001Beser
6208656March 2001Hrastar et al.
6223222April 2001Fijolek et al.
6240464May 2001Fijolek et al.
6269099July 2001Borella et al.
6923659July 1999Curry et al.
Other References
"A Solution for the Priority Queue Problem of Deadline-Ordered Service Disciplines," N.R. Figueira, IEEE International Conference on Computer Communications and Networks, Sep. 22-25, 1997, pp. 320-325. .
Kyees, P.J. et al., ADSL: A New Twisted-Pair Access to the Information Highway, IEEE Communications Magazine, vol. 33, Issue 4, Apr. 1995, pp. 52-60. .
Huang, Yin-Hwa et al., Design of an MPEG-Based Set-Top Box for Video on Demand Services, Acoustics, Speech, and Signal Processing, 1995, ICASSP-95., 1995 International Conference, vol. 4, ISBN: 0-7803-2431-5, May 9-12, 1995, pp. 2655-2658..~
Primary Examiner: Sheikh; Ayaz
Assistant Examiner: Dinh; Khanh Quang
Attorney, Agent or Firm:McDonnell Boehnen Hulbert & Berghoff Lesavich; Stephen
Claims

We claim:
1. In a data-over-cable system including a plurality of network devices, a method of restricting access for a network device, comprising the following steps:
receiving a connection request from a first network device on a second network device on the data-over cable system for a subscription service on the data-over-cable system;
determining from the second network device, whether information about the first network device is available on the data-over-cable system, and if not,
assigning a temporary restricted network address for a restricted connection to the first network device on the data-over-cable system from pre-determined list of restricted network addresses, wherein the temporary network address from the pre-determined list of restricted network addresses provides restricted access to subscription services on the data-over-cable system;
starting a connection timer on the data-over-cable system for a restricted connection to the first network device, wherein the connection timer restricts access to subscription services on the data-over-cable system over a timed interval; and
creating a restricted connection between the data-over-cable system and the first network device including the temporary restricted network address and the connection timer, thereby providing restricted access to subscription services the data-over-cable system.

2. A computer readable medium having stored therein instructions for causing a central processing unit to execute the method of claim 1.

3. The method of claim 1 wherein the first network device is any of a cable modem or customer premise equipment.

4. The method of claim 1 wherein the second network device is a cable modem termination system.

5. The method of claim 1 wherein the second network device is any of a Dynamic Host Configuration Protocol Server or a Remote Authentication Dial In User Service server.

6. The method of claim 1 wherein temporary restricted network address is an Internet Protocol address.

7. The method of claim 1 wherein the step of assigning a temporary restricted network address includes assigning a temporary Internet Protocol address obtained from a Dynamic Host Configuration Protocol server.

8. The method of claim 1 wherein the step of determining from the second network device, whether information about the first network device is available on the data-over-cable system, includes determining with information from a database associated with the second network device, whether information about the first network device is available on the data-over-cable system, wherein the database includes information about network devices that subscribe to services offered on the data-over-cable system.

9. The method of claim 1 wherein the step of determining from the second network device, whether information about the first network device is available on the data-over-cable system, includes determining whether a Medium Access Protocol address for the first network device is available on the data-over-cable system.

10. The method of claim 1 wherein the step of starting a connection timer includes starting a connection timer for a network port for a limited amount of time, wherein the network port is used to connect the first network device to a subscription service on the data-over-cable system on a restricted connection.

11. The method of claim 1, further comprising:
determining from the second network device, whether information about the first network device is available on the data-over-cable system, and if so,
assigning an unrestricted network address for an unrestricted connection to the first network device on the data-over-cable system from a list of unrestricted network addresses; and
creating an unrestricted connection to a subscription service between the data-over-cable system and the first network device including the unrestricted network address, thereby providing unrestricted access to a subscription service on the data-over-cable system.

12. In a data-over-cable system including a plurality of network devices, a method of changing access for a network device, comprising the following steps:
creating a restricted connection between a first network device and the data-over-cable system including a restricted network address from a pre-determined list of restricted network addresses providing restricted access to a subscription service the data-over-cable system, and a connection timer restricting access to the subscription service on data-over-cable system over a timed interval, thereby providing restricted access to the subscription service to the data-over-cable system over a timed interval;
obtaining information from the first network device on a second network device to uniquely identify the first network device on the data-over-cable system;
saving the information in a database associated with the second network device; and
changing the restricted connection to the subscription service between the first network device and the data-over-cable system to an unrestricted connection to the subscription service between the first network device and the data-over-cable system by:
terminating the restricted connection to the subscription service between the first network device and the data-over-cable system from the second network device;
receiving a new connection request from the first network device on the second network device to the subscription service on the data-over cable system;
validating information about the first network device using information from the database associated with the second network device; and
creating an unrestricted connection for the subscription service between the first network device and the data-over-cable system using information from the database.

13. A computer readable medium having stored therein instructions for causing processing unit to execute the method of claim 12.

14. The method of claim 12 further comprising changing the restricted network address to an unrestricted network address.

15. The method of claim 12 wherein the step of obtaining information from the first network device includes obtaining information with Simple Network Management Protocol messages.

16. The method of claim 12 wherein the Simple Network Management Protocol messages includes information parameters from a Simple Network Management Protocol management information base for a data-over-cable system.

17. The method of claim 12 wherein the step of changing the restricted connection to the subscription service between the first network device and the data-over-cable system includes applying information saved in the database associated with the second network device to the restricted connection, thereby creating an unrestricted connection to the subscription service between the first network device and the data-over-cable system.

18. In a data-over-cable system including a plurality of network devices, a method of restricting access for a network device, comprising the following steps:
receiving a connection request from a cable modem on a cable modem termination system on the data-over cable system for a subscription service on the data-over-cable system;
determining from the cable modem termination system, whether information about the cable modem is available on the data-over-cable system, and if not,
assigning a temporary restricted Internet Protocol address for a connection to the cable modem on the data-over-cable system from pre-determined list of restricted Internet Protocol addresses, wherein the temporary Internet Protocol address from the pre-determined list of restricted Internet Protocol addresses provides restricted access to the subscription service on the data-over-cable system;
starting a connection timer on the data-over-cable system for a restricted connection to the subscription service for the cable modem, wherein the connection timer restricts access to the subscription service on the data-over-cable system over a timed interval; and
creating a restricted connection between the data-over-cable system and the cable modem including the temporary restricted Internet Protocol address and the connection timer, thereby providing restricted access to the subscription service on the data-over-cable system over a timed interval.

19. A computer readable medium having stored therein instructions for causing a central processing unit to execute the method of claim 18.
Description
FIELD OF INVENTION

The present invention relates to communications in computer networks. More specifically, it relates to methods for restricting access of network devices to subscription services in a data-over-cable system.

BACKGROUND OF THE INVENTION

Cable television networks such as those provided by Comcast Cable Communications, Inc., of Philadelphia, Pa., Cox Communications of Atlanta, Ga., Tele-Communications, Inc., of Englewood Colo., Time-Warner Cable, of Marietta Ga., Continental Cablevision, Inc., of Boston Mass., and others provide cable television services to a large number of subscribers over a large geographical area. The cable television networks typically are interconnected by cables such as coaxial cables or a Hybrid Fiber/Coaxial ("HFC") cable system which have data rates of about 10 Mega-bits-per-second ("Mbps") to about 30+ Mbps.

The Internet, a world-wide-network of interconnected computers, provides multi-media content including audio, video, graphics and text that typically requires a large bandwidth for downloading and viewing. Most Internet Service Providers ("ISPs") allow customers to connect to the Internet via a serial telephone line from a Public Switched Telephone Network ("PSTN") at data rates including 14,400 bps, 28,800 bps, 33,600 bps, 56,000 bps and others that are much slower than the about 10
Mbps to about 30+ Mbps available on a coaxial cable or HFC cable system on a cable television network.

With the explosive growth of the Internet, many customers have desired to use the larger bandwidth of a cable television network to connect to the Internet and other computer networks.

Cable modems, such as those provided by 3Com Corporation, of Santa Clara, Calif., Motorola Corporation, of Arlington Heights, Ill., Hewlett-Packard Co., of Palo Alto, Calif., Bay Networks, of Santa Clara, Calif., Scientific-Atlanta, of Norcross, Ga. and others offer customers higher-speed connectivity to the Internet, an intranet, Local Area Networks ("LANs") and other computer networks via cable television networks. These cable modems currently support a data connection to the Internet and other computer networks via a cable television network with a data rate of up to about 30+ Mbps, which is a much larger data rate than can be supported by a modem used over a serial telephone line.

However, many cable television networks provide only unidirectional cable systems, supporting only a "downstream" cable data path. A downstream data path is the flow of data from a cable system "headend" to a customer. A cable system headend is a central location in the cable television network that is responsible for sending cable signals in the downstream direction. A return data path via a telephone network (i.e., a "telephony return"), such as a public switched telephone network provided by AT&T, GTE, Sprint, MCI and others, is typically used for an "upstream" data path. An upstream data path is the flow of data from the customer back to the cable system headend. A cable television system with an upstream connection to a telephony network is called a "data-over-cable system with telephony return."

An exemplary data-over-cable system with telephony return includes customer premise equipment (e.g., a customer computer), a cable modem, a cable modem termination system, a cable television network, a public switched telephone network, a telephony remote access concentrator and a data network (e.g., the Internet). The cable modem termination system and the telephony remote access concentrator together are called a "telephony return termination system."

The cable modem termination system receives data packets from the data network and transmits them downstream via the cable television network to a cable modem attached to the customer premise equipment. The customer premise equipment sends response data packets to the cable modem, which sends response data packets upstream via public switched telephone network to the telephony remote access concentrator, which sends the response data packets back to the appropriate host on the data network.

In a two-way cable system without telephony return, the customer premise equipment sends response data packets to the cable modem, which sends the data packets upstream via the cable television network to the cable modem termination system. The cable modem termination system sends the data packets to appropriate hosts on the data network. The cable modem termination system sends the response data packets back to the appropriate cable modem.

As a cable modem is initialized in a data-over-cable system, it registers with a cable modem termination system to allow the cable modem to receive data over a cable television connection and from a data network (e.g., the Internet or an Intranet). The cable modem forwards configuration information it receives in a configuration file during initialization to the cable modem termination system as part of a registration request message. A cable modem also helps initialize and register any attached customer premise equipment with the cable modem termination system.

A cable modem termination system in a data-over-cable system typically manages connections to tens of thousands of cable modems. Most of the cable modems are attached to host customer premise equipment such as a customer computer. To send and receive data to and from a computer network like the Internet or an intranet, a cable modem and customer premise equipment and other network devices have a network address dynamically assigned on the data-over-cable system. Many data-over-cable systems use a Dynamic Host Configuration Protocol ("DHCP") as a standard messaging protocol to dynamically allocate network addresses such as Internet Protocol ("IP") addresses. As is known in the art, the Dynamic Host Configuration Protocol is a protocol for passing configuration information to network devices on a network. The Internet Protocol is an addressing protocol designed to route traffic within a network or between networks.

Since the cable modem termination system typically manages connections to tens of thousands of cable modems and customer premise equipment, the cable modem termination system provides access to subscription services for the data-over-cable system as well as access to a subscription data network such as the Internet. The are several problems associated with providing access to subscription services in both the data-over-cable system and the data network for tens of thousand of cable modems and customer premise equipment. If the cable modem termination system does not provide security checks, a rogue cable modem could comprise the security of the cable plant and/or connections to the data network.

One solution is to store information about known cable modems that subscribe to a data-over-cable system in one or more cable modem termination system databases. When an individual cable modem requests a connection, the cable modem termination system is able to determine if the individual cable modem is authorized to access the data-over-cable system using the stored information from the databases. However, such a solution cannot be used for new subscribers, or existing subscribers who connect a new type of cable modem to the data-over-cable system, without updating the databases first. Requiring a database update for one or more databases associated with the cable modem termination system may prevent a new user from accessing the data-over-cable system without a delay, and may also prevent an existing subscriber from using a new cable modem without a delay. The delays may lead to user frustration.

Thus, it is desirable to allow a cable modem termination system to provide restricted access to subscription services for a data-over-cable system. The restricted access should not prevent new subscribers or existing subscribers with a new type of cable modem from accessing subscription services on the data-over-cable system without a long delay.

SUMMARY OF THE INVENTION

In accordance with preferred embodiments of the present invention, some of the problems associated with restricting access to subscription services a data-over-cable system are overcome. One aspect of the invention includes a method for restricting access to subscription services in a data-over-cable system. The method includes receiving a connection request from a first network device on a second network device on a data-over cable system for a subscription service on the data-over-cable system. It is determined from the second network device, whether information about the first network device is available on the data-over-cable system. If not, a temporary restricted network address is assigned for a restricted connection to the first network device on the data-over-cable system from pre-determined list of restricted network addresses. The temporary network address from the pre-determined list of restricted network addresses provides restricted access to subscription services the data-over-cable system. A connection timer on the data-over-cable system for a restricted connection to the first network device is started. The connection timer restricts access to subscription services the data-over-cable system over a timed interval. A restricted connection is created between the data-over-cable system and the first network device including the temporary restricted network address and connection timer, thereby providing restricted access to the data-over-cable system over a timed interval.

The method may allow a cable modem termination system to provide restricted access for new or unknown cable modems or customer premise equipment, to subscription services on a data-over-cable system. However, other network devices could also be used to provide and obtain restricted access on a data-over-cable system, and the present invention is not limited to cable modem termination systems, cable modems, or customer premise equipment. The restricted access to subscription services to subscription services is provided without a long delay, and limits a new or unknown cable modem to a temporary network address for a limited amount of time. Thus, restricted access may also be provided without compromising the security of the data-over-cable system or the connections to the data network (e.g., the Internet).

The foregoing and other features and advantages of a preferred embodiment of the present invention will be more readily apparent from the following detailed description, which proceeds with references to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention are described with reference to the following drawings, wherein:

FIG. 1 is a block diagram illustrating a cable modem system with telephony return;

FIG. 2 is a block diagram illustrating a protocol stack for a cable modem;

FIG. 3 is a block diagram illustrating a Telephony Channel Descriptor message structure;

FIG. 4 is a block diagram illustrating a Termination System Information message structure;

FIG. 5 is a flow diagram illustrating a method for addressing hosts in a cable modem system;

FIG. 6 is a block diagram illustrating a Dynamic Host Configuration Protocol message structure;

FIGS. 7A and 7B are a flow diagram illustrating a method for discovering hosts in a cable modem system;

FIG. 8 is a block diagram illustrating a data-over-cable system for the method illustrated in FIGS. 7A and 7B;

FIG. 9 is a block diagram illustrating the message flow of the method illustrated in FIGS. 7A and 7B;

FIGS. 10A and 10B are a flow diagram illustrating a method for resolving host addresses in a data-over-cable system;

FIG. 11 is a flow diagram illustrating a method for resolving discovered host addresses; and

FIG. 12 is a block diagram illustrating the message flow of the method illustrated in FIG. 10;

FIGS. 13A and 13B are a flow diagram illustrating a method for obtaining addresses for customer premise equipment;

FIGS. 14A and 14B are a flow diagram illustrating a method for resolving addresses for customer premise equipment;

FIGS. 15A and 15B are a flow diagram illustrating a method for addressing network host interfaces from customer premise equipment;

FIGS. 16A and 16B are a flow diagram illustrating a method for resolving network host interfaces from customer premise equipment;

FIG. 17 is a block diagram illustrating a message flow for the methods in FIGS. 15A, 15B, and 16A and 16B;

FIG. 18 is a flow diagram illustrating a method for restricting access to network devices in a data-over-cable system;

FIG. 19 is a flow diagram illustrating a method for changing access for a network device in a data-over-cable system; and

FIG. 20 is a flow diagram illustrating a method for changing access for a network device in a data-over-cable system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Exemplary Data-over-cable System

FIG. 1 is a block diagram illustrating an exemplary data-over-cable system 10. Most cable providers known in the art predominately provide uni-directional cable systems, supporting only a "downstream" data path. A downstream data path is the flow of data from a cable television network "headend" to customer premise equipment (e.g., a customer's personal computer). A cable television network headend is a central location that is responsible for sending cable signals in a downstream direction. A return path via a telephony network ("telephony return") is typically used for an "upstream" data path in uni-directional cable systems. An upstream data path is the flow of data from customer premise equipment back to the cable television network headend.

However, data-over-cable system 10 of the present invention may also provide a bi-directional data path (i.e., both downstream and upstream) without telephony return as is also illustrated in FIG. 1 and the present invention is not limited to a data-over-cable system with telephony return. In a data-over cable system without telephony return, customer premise equipment or a cable modem has an upstream connection to the cable modem termination system via a cable television connection, a wireless connection, a satellite connection, or a connection via other technologies to send data upstream to the cable modem termination system.

Data-over-cable system 10 includes a Cable Modem Termination System ("CMTS") 12 connected to a cable television network 14, hereinafter cable network 14. FIG. 1 illustrates one CMTS 12. However, data-over-cable system 10 can include multiple CMTS 12. Cable network 14 includes cable television networks such as those provided by Comcast Cable Communications, Inc., of Philadelphia, Pa., Cox Communications, or Atlanta, Ga., Tele-Communications, Inc., of Englewood Color., Time-Warner Cable, of Marietta, Ga., Continental Cablevision, Inc., of Boston, Mass., and others. The cable network 14 is connected to a Cable Modem ("CM") 16 with a downstream cable connection. The CM 16 is any cable modem such as those provided by 3Com Corporation of Santa Clara, Calif., Motorola Corporation of Arlington Heights, Ill., Hewlett-Packard Co. of Palo Alto, Calif., Bay Networks of Santa Clara, Calif., Scientific-Atlanta, of Norcross, Ga. and others. FIG. 1 illustrates one CM 16. However, in a typical data-over-cable system, tens or hundreds of thousands of the CM 16 are connected to the CMTS 12.

The CM 16 is connected to Customer Premise Equipment ("CPE") 18 such as a personal computer system via a Cable Modem-to-CPE Interface ("CMCI") 20. In one preferred embodiment of the present invention, the CM 16 is connected to a Public Switched Telephone Network ("PSTN") 22 with an upstream telephony connection. The PSTN 22 includes those public switched telephone networks provided by AT&T, Regional Bell Operating Companies (e.g., Ameritech, U.S. West, Bell Atlantic, Southern Bell Communications, Bell South, NYNEX, and Pacific Telesis Group), GTE, Sprint, MCI and others. The upstream telephony connection is any of a standard telephone line connection, Integrated Services Digital Network ("ISDN") connection, Asymmetric Digital Subscriber Line ("ADSL") connection, or other telephony connection. The PSTN 22 is connected to a Telephony Remote Access Concentrator ("TRAC")

In another preferred embodiment of the present invention, a data-over cable system without telephony return, the CM 16 has an upstream connection to the CMTS 12 via a cable television connection, a wireless connection, a satellite connection, or a connection via other technologies to send data upstream outside of the telephony return path. An upstream cable television connection via cable network 14 is illustrated in FIG. 1.

FIG. 1 illustrates a telephony modem integral to the CM 16. In another embodiment of the present invention, the telephony modem is a separate modem unit external to the CM 16 used specifically for connecting with the PSTN 22. A separate telephony modem includes a connection to the CM 16 for exchanging data. In yet another embodiment of the present invention, the CM 16 includes functionality to connect only to the cable network 14 and receives downstream signals from the cable network
14 and sends upstream signals to the cable network 14 without telephony return. The present invention is not limited to cable modems used with telephony return.

In one preferred embodiment of the present invention of the telephony return, the TRAC 26 is a Total Control Telephony Hub by 3Com Corporation of Santa Clara, Calif.. An exemplary TRAC 26 is described in U.S. Pat. No. 5,528,595, granted to Dale M. Walsh et al., and incorporated herein by reference. However, the TRAC 26 could also be used including those by Lucent Technologies of Murray Hill, N.J., Livingston Enterprises, Inc. of Pleasanton, Calif., Ascend Communications of Alameda, Calif. and others.

The CMTS 12 and the TRAC 24 may be at a "headend" of cable system 10, or the TRAC 24 may be located elsewhere and have routing associations to the CMTS 12. The CMTS 12 and the TRAC 24 together are called a "Telephony Return Termination System" ("TRTS") 26. The

TRTS 26 is illustrated by a dashed box in FIG. 1. The CMTS 12 and the TRAC 24 make up the TRTS 26 whether or not they are located at the headend of cable network 14. The TRAC 24 may be located in a different geographic location from the CMTS
12. Content severs, operations servers, administrative servers and maintenance servers used in data-over-cable system 10 (not shown in FIG. 1) may also be in different locations. Access points to the data-over-cable system 10 are connected to one or more CMTS 12, or cable headend access points. Such configurations may be "one-to-one", "one-to-many," or "many-to-many," and may be interconnected to other Local Area Networks ("LANs") or Wide Area Networks ("WANs").

The TRAC 24 is connected to a data network 28 (e.g., the Internet, an intranet or other LAN) by a TRAC-Network System Interface 30 ("TRAC-NSI"). The CMTS 12 is connected to data network 28 by a CMTS-Network System Interface ("CMTS-NSI") 32. The present invention is not limited to data-over-cable system 10 illustrated in FIG. 1, and more or fewer components, connections and interfaces could also be used. The present invention may also be used in a data-over-cable system 10 with or without telephony return.

Network Device Protocol Stack

FIG. 2 is a block diagram illustrating a protocol stack 36 for network devices in data-over-cable system 10. FIG. 2 illustrates the downstream and upstream protocols used, for example, in the CM 16. As is known in the art, the Open System Interconnection ("OSI") model is used to describe computer networks. The OSI model consists of seven layers including from lowest-to-highest, a physical, data-link, network, transport, session, presentation and application layer. The physical layer transmits bits over a communication link. The data link layer transmits error free frames of data. The network layer transmits and routes data packets.

For downstream data transmission, network devices including the CM 16 are connected to cable network 14 in a physical layer 38 via a Radio Frequency ("RF") Interface 40. In a preferred embodiment of the present invention, RF Interface 40 has an operation frequency range of 50 Mega-Hertz ("MHz") to 1 Giga-Hertz ("GHz") and a channel bandwidth of 6 MHz. However, other operation frequencies may also be used and the invention is not limited to these frequencies. The RF interface 40 uses a signal modulation method of Quadrature Amplitude Modulation ("QAM"). As is known in the art, QAM is used as a means of encoding digital information over radio, wire, or fiber optic transmission links. QAM is a combination of amplitude and phase modulation and is an extension of multiphase phase-shift-keying. QAM can have any number of discrete digital levels typically including 4, 16, 64 or 256 levels. In one embodiment of the present invention, QAM-64 is used in the RF interface 40. However, other operating frequencies modulation methods could also be used. For more information on the RF interface 40 see the Institute of Electrical and Electronic Engineers ("IEEE") standard 802.14 for cable modems incorporated herein by reference. IEEE standards can be found on the World Wide Web at the Universal Resource Locator ("URL") "www.ieee.org." However, other RF interfaces 40 could also be used and the present invention is not limited to IEEE 802.14 (e.g., RF interfaces from Multimedia Cable Network Systems ("MCNS") and others could also be used).

Above the RF interface 40 in a data-link layer 42 is a Medium Access Control ("MAC") layer 44. As is known in the art, the MAC layer 44 controls access to a transmission medium via physical layer 38. For more information on the MAC layer protocol 44 see IEEE 802.14 for cable modems. However, other MAC layer protocols 44 could also be used and the present invention is not limited to IEEE 802.14 MAC layer protocols (e.g., MCNS MAC layer protocols and others could also be used).

Above the MAC layer 44 is an optional link security protocol stack 46. The link security protocol stack 46 prevents unauthorized users from making a data connection from cable network 14. The RF interface 40 and the MAC layer 44 can also be used for an upstream connection in a data-over-cable system 10 without telephony return.

For upstream data transmission with telephony return, the CM 16 is connected to the PSTN 22 in physical layer 38 via modem interface 48. The International Telecommunications Union-Telecommunication Standardization Sector ("ITU-T", formerly known as the CCITT) defines standards for communication devices identified by "V.xx" series where "xx" is an identifying number. ITU-T standards can be found on the World Wide Web at the URL "www.itu.ch."

In one embodiment of the present invention, ITU-T V.34 is used as modem interface 48.

As is known in the art, ITU-T V.34 is commonly used in the data link layer for modem communications and currently allows data rates as high as 33,600 bits-per-second ("bps"). For more information see the ITU-T V.34 standard. However, other modem interfaces or other telephony interfaces could also be used. For example, Asymmetric Digital Subscribe Link ("ADSL") or Integrated Services Digital Network ("ISDN") telephony interface could also be used in place of the modem interface 48.

Above modem interface 48 in data link layer 42 is Point-to-Point Protocol ("PPP") layer 50, hereinafter PPP 50. As is known in the art, PPP is used to encapsulate network layer datagrams over a serial communications link. For more information on PPP see Internet

Engineering Task Force ("IETF") Request for Comments ("RFC"), RFC-1661, RFC-1662 and RFC-1663, incorporated herein by reference. Information for IETF RFCs can be found on the World Wide Web at URLs "ds.internic.net" or "www.ietf.org."

Above both the downstream and upstream protocol layers in a network layer 52 is an Internet Protocol ("IP") layer 54. IP layer 54, hereinafter IP 54, roughly corresponds to OSI layer 3, the network layer, but is typically not defined as part of the OSI model. As is known in the art, IP 54 is a routing protocol designed to route traffic within a network or between networks. For more information on IP 54 see RFC-791 incorporated herein by reference.

Internet Control Message Protocol ("ICMP") layer 56 is used for network management. The main functions of ICMP layer 56, hereinafter ICMP 56, include error reporting, reachability testing (e.g., "pinging") congestion control, route-change notification, performance, subnet addressing and others. Since IP 54 is an unacknowledged protocol, datagrams may be discarded and ICMP 56 is used for error reporting. For more information on ICMP 56 see, RFC-792, incorporated herein by reference.

Above IP 54 and ICMP 56 is a transport layer 58 with a User Datagram Protocol layer 60 ("UDP"). UDP layer 60, hereinafter UDP 60, roughly corresponds to OSI layer 4, the transport layer, but is typically not defined as part of the OSI model. As is known in the art, UDP 60 provides a connectionless mode of communications with datagrams. For more information on UDP 60 see RFC-768, incorporated herein by reference.

Above the network layer are a Simple Network Management Protocol ("SNMP") layer 62, Trivial File Transfer Protocol ("TFTP") layer 64, Dynamic Host Configuration Protocol ("DHCP") layer 66 and a UDP manager 68. SNMP layer 62 is used to support network management functions. For more information on SNMP layer 62 see RFC-1157, incorporated herein by reference. TFTP layer 64 is a file transfer protocol used to download files and configuration information. For more information on TFTP layer 64
see RFC-1350 incorporated herein by reference. The DHCP layer 66 is a protocol for passing configuration information to hosts on an IP 54 network. For more information on the DHCP layer 66 see RFC-1541 and RFC-2131, incorporated herein by reference. UDP manager 68 distinguishes and routes packets to an appropriate service (e.g., a virtual tunnel). More or few protocol layers could also be used with data-over-cable system 10.

The CM 16 supports transmission and reception of IP 54 datagrams as specified by RFC-791. The CMTS 12 and the TRAC 24 may also perform filtering of IP 54 datagrams. The CM 16 is also configurable for IP 54 datagram filtering to restrict the CM
16 and the CPE 18 to the use of only their assigned IP 54 addresses. The CM 16 is configurable for IP 54 datagram UDP 60 port filtering (i.e., deep filtering).

The CM 16 forwards IP 54 datagrams destined to an IP 54 unicast address across the cable network 14 or the PSTN 22. Some routers have security features intended to filter out invalid users who alter or masquerade packets as if sent from a valid user. Since routing policy is under the control of network operators, such filtering is a vendor specific implementation. For example, dedicated interfaces (i.e., Frame Relay) may exist between the TRAC 24 and/or the CMTS 12 which preclude filtering, or various forms of virtual tunneling and reverse virtual tunneling could be used to virtually source upstream packets from the CM 16. For more information on virtual tunneling, see Level 2 Tunneling Protocol ("L2TP") or Point-to-Point Tunneling Protocol ("PPTP") in IETF draft documents incorporated herein by reference by Kory Hamzeh, et. al (IETF draft documents are precursors to IETF RFCs and are works in progress).

The CM 16 also forwards IP 54 datagrams destined to an IP 54 multicast address across the cable network 14 or the PSTN 22. The CM 16 is configurable to keep IP 54 multicast routing tables and to use group membership protocols. The CM 16 is also capable of IP 54 tunneling upstream through the telephony path. A CM 16 that wants to send a multicast packet across a virtual tunnel will prepend another IP 54 header, set the destination address in the new header to be the unicast address of the CMTS
12 at the other end of the tunnel, and set the IP 54 protocol field to be four, which means the next protocol is IP 54.

The CMTS 12 at the other end of the virtual tunnel receives the packet, strips off the encapsulating IP 54 header, and forwards the packet as appropriate. A broadcast IP 54 capability is dependent upon the configuration of the direct linkage, if any, between the TRAC 24 and the CMTS 12. The CMTS 12, the CM 16, and the TRAC 24 are capable of routing IP 54 datagrams destined to an IP 54 broadcast address which is across the cable network 14 or the PSTN 22 if so configured. The CM 16 is configurable for IP 54 broadcast datagram filtering.

An operating environment for devices of the present invention includes a processing system with at least one high speed Central Processing Unit ("CPU") and a memory system. In accordance with the practices of persons skilled in the art of computer programming, the present invention is described below with reference to acts and symbolic representations of operations or instructions that are performed by the processing system, unless indicated otherwise. Such acts and operations or instructions are sometimes referred to as being "computer-executed", or "CPU executed."

It will be appreciated that the acts and symbolically represented operations include the manipulation of electrical signals by the CPU. An electrical system with data bits causes a resulting transformation or reduction of the electrical signal representation, and the maintenance of data bits at memory locations in the memory system to thereby reconfigure or otherwise alter the CPU's operation, as well as other processing of signals. The memory locations where data bits are maintained are physical locations that have particular electrical, magnetic, optical, or organic properties corresponding to the data bits.

The data bits may also be maintained on a computer readable medium including magnetic disks, optical disks, organic disks, and any other volatile or non-volatile mass storage system readable by the CPU. The computer readable medium includes cooperating or interconnected computer readable media, which exist exclusively on the processing system or is distributed among multiple interconnected processing systems that may be local or remote to the processing system.

Initialization of a Cable Modem with Telephony Return

When the CM 16 is initially powered on, if telephony return is being used, the CM 16 will receive a Telephony Channel Descriptor ("TCD") from the CMTS 12 that is used to provide dialing and access instructions on downstream channels via cable network 14. Information in the TCD is used by the CM 16 to connect to the TRAC 24. The TCD is transmitted as a MAC management message with a management type value of TRI_TCD at a periodic interval (e.g., every 2 seconds). To provide for flexibility, the TCD message parameters are encoded in a Type/Length/Value ("TLV") form. However, other encoding techniques could also be used. FIG. 3 is a block diagram illustrating a TCD message structure 70 with MAC 44 management header 72 and Service Provider Descriptor(s) ("SPD") 74 encoded in TLV format. SPDs 74 are compound TLV encodings that define telephony physical-layer characteristics that are used by CM 16 to initiate a telephone call. The SPD 74 is a TLV-encoded data structure that contains sets of dialing and access parameters for CM 16 with telephony return. The SPD 74 is contained within TCD message 70. There may be multiple SPD 74 encodings within a single TCD message 70. There is at least one SPD 74 in TCD message 70. The SPD 74
parameters are encoded as SPD-TLV tuples. The SPD 74 contains the parameters shown in Table 1 and may contain optional vendor specific parameters. However, more or fewer parameters could also be used in the SPD 74.

TABLE 1 SPD 74 Parameter Description Factory Default Flag Boolean value, if TRUE (1), indicates a SPD which should be used by the CM 16. Service Provider Name This parameter includes the name of a service provider. Format is standard ASCII string composed of numbers and letters. Telephone Numbers These parameters contain telephone numbers that the CM 16 uses to initiate a telephony modem link during a login process. Connections are attempted in ascending numeric order (i.e., Phone Number 1, Phone Number 2 . . .). The SPD contains a valid telephony dial string as the primary dial string (Phone Number 1), secondary dial-strings are optional. Format is ASCII string(s) composed of: any sequence of numbers, pound "#" and star "*" keys and comma character "," used to indicate a two second pause in dialing. Connection Threshold The number of sequential connection failures before indicating connection failure. A dial attempt that does not result in an answer and connection after no more than ten rings is considered a failure. The default value is one. Login User Name This contains a user name the CM 16 will use an authentication protocol over the telephone link during the initialization procedure. Format is a monolithic sequence of alphanumeric characters in an ASCII string composed of numbers and letters. Login Password This contains a password that CM 16 will use during authentication over a telephone link during the initialization procedure. Format is a monolithic sequence of alphanumeric characters in an ASCII string composed of numbers and letters. DHCP Authenticate Boolean value, reserved to indicate that the CM 16 uses a specific indicated DHCP 66 Server (see next parameter) for a DHCP
66 Client and BOOTP Relay Process when TRUE (one). The default is FALSE (zero) which allows any DHCP 66 Server. DHCP Server IP 54 address value of a DHCP 66 Server the CM 16 uses for DHCP 66 Client and BOOTP Relay Process. If this attribute is present and DHCP 66 Authenticate attribute is TRUE (1). The default value is integer zero. RADIUS Realm The realm name is a string that defines a Remote Authentication Dial In User Service ("RADIUS") server domain. Format is a monolithic sequence of alphanumeric characters in an ASCII string composed of numbers and letters. PPP Authentication This parameter instructs the telephone modem which authentication procedure to perform over the telephone link. Demand Dial Timer This parameter indicates time (in seconds) of inactive networking time that will be allowed to elapse before hanging up a telephone connection at CM 16. If this optional parameter is not present, or set to zero, then the demand dial feature is not activated. The default value is zero. Vendor Specific Extensions Optional vendor specific extensions.

A Termination System Information ("TSI") message is transmitted by the CMTS 12 at periodic intervals (e.g., every 2 seconds) to report the CMTS 12 information to the CM 165 whether or not telephony return is used. The TSI message is transmitted as a MAC 44 management message. The TSI provides a CMTS 12 boot record in a downstream channel to the CM 16 via cable network 14. Information in the TSI is used by the CM 16 to obtain information about the status of the CMTS 12. The TSI message has a MAC 44 management type value of TRI_TSI.

FIG. 4 is a block diagram of a TSI message structure 76. TSI message structure 76 includes a MAC 44 management header 78, a downstream channel IP address 80, a registration IP address 82, a CMTS 12 boot time 84, a downstream channel identifier
86, an epoch time 88 and vendor specific TLV encoded data 90.

A description of the fields of TSI message 76 are shown in Table 2. However, more or fewer fields could also be used in TSI message 76.

TABLE 2 TSI 76 Parameter Description Downstream Channel This field contains an IP 54 address of IP Address 80 the CMTS 12 available on the downstream channel this message arrived on. Registration IP Address 82 This field contains an IP 54
address the CM 16 sends its registration request messages to. This address MAY be the same as the Downstream Channel IP 54 address. CMTS Boot Time 84 Specifies an absolute-time of a CMTS 12 recorded epoch. The clock setting for this epoch uses the current clock time with an unspecified accuracy. Time is represented as a 32 bit binary number. Downstream Channel ID 86 A downstream channel on which this message has been transmitted. This identifier is arbitrarily chosen by CMTS 12 and is unique within the MAC 44 layer. Epoch 88 An integer value that is incremented each time the CMTS 12 is either re- initialized or performs address or routing table flush. Vendor Specific Extensions 90 Optional vendor extensions may be added as TLV encoded data.

If telephony returns are being used, after receiving TCD 70 message and TSI message 76, CM 16 continues to establish access to data network 28 (and resources on the network) by first dialing into the TRAC 24 and establishing a telephony PPP 50
session. Upon the completion of a successful PPP 50 connection, the CM 16 performs PPP 50 Link Control Protocol ("LCP") negotiation with the TRAC 24. Once LCP negotiation is complete, the CM 16 requests Internet Protocol Control Protocol ("IPCP") address negotiation. For more information on IPCP see RFC-1332 incorporated herein by reference. During IPCP negotiation, the CM 16 negotiates an IP 54 address with the TRAC 24 for sending IP 54 data packet responses back to data network 28 via the TRAC 24, via PPP 50.

When the CM 16 has established an IP 54 link to TRAC 24, it begins "upstream" communications to the CMTS 12 via the DHCP layer 66 to complete a virtual data connection by attempting to discover network host interfaces available on the CMTS 12
(e.g., IP 54 host interfaces for a virtual IP 54 connection). The virtual data connection allows the CM 16 to receive data from data network 28 via the CMTS 12 and cable network 14, and send return data to data network 28 via TRAC 24 and PSTN 22. The CM 16 first determines an address of a host interface (e.g., an IP 54 interface) associated with on the CMTS 12 that can be used by data network 28 to send data to the CM 16. However, the CM 16 has only a downstream connection from the CMTS 12 and has to obtain a connection address to the data network 28 using an upstream connection to the TRAC 24.

Addressing Network Host Interfaces in the Data-over-cable System Via the Cable Modem

FIG. 5 is a flow diagram illustrating a method 92 for addressing network host interfaces in a data-over-cable system with telephony return via a cable modem. Method 92 allows a cable modem to establish a virtual data connection to a data network. In method 92, multiple network devices are connected to a first network with a downstream connection of a first connection type, and connected to a second network with an upstream connection of a second connection type. The first and second networks are connected to a third network with a third connection type.

At Step 94, a selection input is received on a first network device from the first network over the downstream connection. The selection input includes a first connection address allowing the first network device to communicate with the first network via upstream connection to the second network. At Step 96, a first message of a first type for a first protocol is created on the first network device having the first connection address from the selection input in a first message field. The first message is used to request a network host interface address on the first network. The first connection address allows the first network device to have the first message with the first message type forwarded to network host interfaces available on the first network via the upstream connection to the second network.

At Step 98, the first network device sends the first message over the upstream connection to the second network. The second network uses the first address field in the first message to forward the first message to one or more network host interfaces available on first network at Step 100. Network host interfaces available on the first network that can provide the services requested in first message send a second message with a second message type with a second connection address in a second message field to the first network at Step 102. The second connection address allows the first network device to receive data packets from the third network via a network host interface available on the first network. The first network forwards one or more second messages on the downstream connection to the first network device at Step 104.

The first network device selects a second connection address from one of the second messages from one of the one or more network host interfaces available on the first network at Step 106 and establishes a virtual connection from the third network to the first network device using the second connection address for the selected network host interface.

The virtual connection includes receiving data on the first network host interface on the first network from the third network and sending the data over the downstream connection to the first network device. The first network device sends data responses back to the third network over the upstream connection to the second network, which forwards the data to the appropriate destination on the third network.

In one preferred embodiment of the present invention, the data-over-cable system is the data-over-cable system 10, with telephony return. In such an embodiment, the first network device is the CM 16, the first network is the cable network 14, and the downstream connection is a cable television connection. The second network is the PSTN 22, the upstream connection is a telephony connection, the third network is data network 28 (e.g., the Internet or an intranet) and the third type of connection is an IP 54 connection. The first and second connection addresses are IP 54 addresses. However, the present invention is not limited to the network components and addresses described. Method 92 allows the CM 16 to determine an IP 54 network host interface address available on the CMTS 12 to receive IP 54 data packets from data network 28, thereby establishing a virtual IP 54 connection with data network 28.

After addressing network host interfaces using Method 92, an exemplary data path through cable system 10 is illustrated in Table 3. However other data paths could also be used and the present invention is not limited to the data paths shown in Table 3. For example, the CM 16 may send data upstream back through cable network 14 (e.g., the CM 16 to cable network 14 to the CMTS 12) and not use the PSTN 22, the TRAC 24 or the telephony return upstream path.

TABLE 3 1. An IP 54 datagram from data network 28 destined for the CM 16 arrives on the CMTS-NSI 32 and enters the CMTS 12. 2. CMTS 12 encodes the IP 54 datagram in a cable data frame, passes it to MAC 44 and transmits it "downstream" to RF interface 40 on the CM 16 via cable network 14. 3. CM 16 recognizes the encoded IP 54 datagram in MAC layer 44 received via RF interface 40. 4. CM 16 responds to the cable data frame and encapsulates a response IP 54 datagram in a PPP 50 frame and transmits it "upstream" with modem interface 48 via the PSTN 22 to TRAC 24. 5. TRAC 24 decodes the IP 54 datagram and forwards it via TRAC-NSI 30 to a destination on data network 28.

Dynamic Network Host Configuration on Data-over-cable System

As was illustrated in FIG. 2, the CM 16 includes a Dynamic Host Configuration Protocol ("DHCP") layer 66, hereinafter the DHCP 66. The DHCP 66 is used to provide configuration parameters to hosts on a network (e.g., an IP 54 network). The DHCP
66 consists of two components: a protocol for delivering host-specific configuration parameters from a DHCP 66 server to a host and a mechanism for allocation of network host addresses to hosts. The DHCP 66 is built on a client-server model, where designated the DHCP 66 servers allocate network host addresses and deliver configuration parameters to dynamically configured network host clients.

FIG. 6 is a block diagram illustrating an exemplary DHCP 66 message structure 108. The format of the DHCP 66 messages is based on the format of BOOTstrap Protocol ("BOOTP") messages described in RFC-951 and RFC-1542, incorporated herein by reference. From a network host client's point of view, the DHCP 66 is an extension of the BOOTP mechanism. This behavior allows existing BOOTP clients to interpret with the DHCP 66 servers without requiring any change to network host the clients' BOOTP initialization software. The DHCP 66 provides persistent storage of network parameters for network host clients.

To capture BOOTP relay agent behavior described as part of the BOOTP specification and to allow interoperability of existing BOOTP clients with the DHCP 66 servers, the DHCP 66 uses a BOOTP message format. Using BOOTP relaying agents eliminates the necessity of having a DHCP 66 server on each physical network segment.

DHCP 66 message structure 108 includes an operation code field 110 ("op"), a hardware address type field 112 ("htype"), a hardware address length field 114 ("hlen"), a number of hops field 116 ("hops"), a transaction identifier field 118 ("xid"), a seconds elapsed time field 120 ("secs"), a flags field 122 ("flags"), a client IP address field 124 ("ciaddr"), a your IP address field 126 ("yiaddr"), a server IP address field 128 ("siaddr"), a gateway/relay agent IP address field 130 ("giaddr"), a client hardware address field 132 ("chaddr"), an optional server name field 134 ("sname"), a boot file name 136 ("file") and an optional parameters field 138 ("options"). Descriptions for an exemplary DHCP 66 message 108 fields are shown in Table 4.

TABLE 4 DCHP 66 Parameter Description OP 110 Message op code/message type. 1 BOOTREQUEST, 2 = BOOTREPLY. HTYPE 112 Hardware address type (e.g., `1` = 10 Mps Ethernet). HLEN 114 Hardware address length (e.g. `6` for 10 Mbps Ethernet). HOPS 116 Client sets to zero, optionally used by relay-agents when booting via a relay- agent. XID 118 Transaction ID, a random number chosen by the client, used by the client and server to associate messages and responses between a client and a server. SECS 120 Filled in by client, seconds elapsed since client started trying to boot. FLAGS 122 Flags including a BROADCAST bit. CIADDR 124 Client IP address; filled in by client in DHCPREQUEST if verifying previously allocated configuration parameters. YIADDR 126 `Your` (client) IP address. SIADDR 128 IP 54 address of next server to use in bootstrap; returned in DHCPOFFER, DHCPACK and DHCPNAK by server. GIADDR 130 Gateway relay agent IP 54 address, used in booting via a relay-agent. CHADDR Client hardware address (e.g., MAC 132 layer 44 address). SNAME 134 Optional server host name, null terminated string. FILE 136 Boot file name, terminated by a null string. OPTIONS Optional parameters. 138

The DHCP 66 message structure shown in FIG. 6 is used to discover IP 54 and other network host interfaces in data-over-cable system 10. A network host client (e.g., the CM 16) uses the DHCP 66 to acquire or verify an IP 54 address and network parameters whenever the network parameters may have changed. Table 5 illustrates a typical use of the DHCP 66 protocol to discover a network host interface from a network host client.

TABLE 5 1. A network host client broadcasts a DHCPDISCOVER message on its local physical subnet. The DHCPDISCOVER message may include options that suggest values for a network host interface address. BOOTP relay agents may pass the message on to DHCP 66 servers not on the same physical subnet. 2. DHCP servers may respond with a DHCPOFFER message that includes an available network address in the `yiaddr` field (and other configuration parameters in DHCP 66 options) from a network host interface. DHCP 66 servers unicasts the DHCPOFFER message to the network host client (using the DHCP/BOOTP relay agent if necessary) if possible, or may broadcast the message to a broadcast address (preferably 255.255.255.255) on the client's subnet.
3. The network host client receives one or more DHCPOFFER messages from one or more DHCP 66 servers. The network host client may choose to wait for multiple responses. 4. The network host client chooses one DHCP 66 server with an associated network host interface from which to request configuration parameters, based on the configuration parameters offered in the DHCPOFFER messages.

Discovering Network Host Interfaces in the Data-over-cable System

The DHCP 66 discovery process illustrated in table 5 will not work in data-over-cable system 10. In an exemplary preferred embodiment of the present invention with telephony return, the CM 16 discovers network host interfaces via TRAC 24 and the PSTN 22 on an upstream connection. In another exemplary preferred embodiment of the present invention without telephony return, the CM 16 discovers network host interfaces via the CMTS 12 or an upstream connection.

The DHCP 66 addressing process shown in Table 5 was not originally intended to discover network host interfaces in data-over-cable system 10. The CMTS 12 has the DHCP 66 servers associated with network host interfaces (e.g., IP interfaces), but in one preferred embodiment of the present invention with telephony return, the CM 16 only has as downstream connection from the CMTS 12. the CM 16 has an upstream connection to TRAC 24, which has a DHCP 66 layer. However, TRAC 24 does not have the DHCP 66 servers, or direct access to network host interfaces (e.g., IP 54 interfaces) on the CMTS 12.

FIGS. 7A and 7B are a flow diagram illustrating a Method 140 for discovering network host interfaces in data-over-cable system 10. When the CM 16 has established an IP 54 link to TRAC 24, via PPP 50, it begins communications with the CMTS 12 via the DHCP 66 to complete a virtual IP 54 connection with data network 28. However, to discover what IP 54 host interfaces might be available on the CMTS 12, the CM 16 has to communicate with the CMTS 12 via the PSTN 22 and TRAC 24 since the CM 16 only has a "downstream" cable channel from the CMTS 12 in a data-over-cable system with telephony return.

At Step 142 in FIG. 7A, after receiving a TSI message 76 from the CMTS 12 on a downstream connection, the CM 16 generates a DHCP discover ("DHCPDISCOVER") message and sends it upstream via the PSTN 22 to TRAC 22 to discover what IP 54 interfaces are available on the CMTS 12. The fields of the DHCP 66 discover message are set as illustrated in Table 6. However, other field settings may also be used.

TABLE 6 DHCP 66 Parameter Description OP 110 Set to BOOTREQUEST. HTYPE 112 Set to network type (e.g., one for 10 Mbps Ethernet). HLEN 114 Set to network length (e.g., six for 10 Mbps Ethernet) HOPS 116 Set to zero. FLAGS 122 Set BROADCAST bit to zero. CIADDR 124 If the CM 16 has previously been assigned an IP 54 address, the IP 54 address is placed in this field. If the CM 16 has previously been assigned an IP 54 address by the DHCP 66, and also has been assigned an address via IPCP, the CM 16 places the DHCP 66 IP 54 address in this field. GIADDR 130 CM 16 places the Downstream Channel IP 54 address 80 of the CMTS 12 obtained in TSI message 76 on a cable downstream channel in this field. CHADDR 132 CM 16 places its
48-bit MAC 44 LAN address in this field.

The DHCPDISCOVER message is used to "discover" the existence of one or more IP 54 host interfaces available on the CMTS 12. The DHCP 66 giaddr-field 130 (FIG. 6) includes the downstream channel IP address 80 of the CMTS 12 obtained in TSI message 76 (e.g., the first message field from Step 96 of Method 92). Using the downstream channel IP address 80 of the CMTS 12 obtained in TSI message 76 allows the DHCPDISCOVER message to be forwarded by TRAC 24 to the DHCP 66 servers (i.e., protocol servers) associated with network host interfaces available on the CMTS 12. If the DHCP 66 giaddr-field 130 (FIG. 6) in a DHCP message from a DHCP 66 client is non-zero, the DHCP 66 server sends any return messages to a DHCP 66 server port on a DHCP 66
relaying agent (e.g., the CMTS 12) whose address appears in the DHCP 66 giaddr-field 130.

In a typical DHCP 66 discovery process, the DHCP 66 giaddr-field 130 is set to zero. However, in one preferred embodiment of the present invention, the DHCP 66 giaddr-field 130 contains the IP address 80 of the CMTS 12. If the DHCP 66
giaddr-field 130 is zero, the DHCP 66 client is on the same subnet as the DHCP 66 server, and the DHCP 66 server sends any return messages to either the DHCP 66 client's network address, if that address was supplied in the DHCP 66 ciaddr-field 124 (FIG.
6), or to a client's hardware address (e.g., MAC address 44) specified in the DHCP 66 chaddr-field 132 (FIG. 6) or to a local subnet broadcast address (e.g., 255.255.255.255).

At Step 144, a DHCP 66 layer on TRAC 24 broadcasts the DHCPDISCOVER message on its local network leaving the DHCP 66 giaddr-field 130 intact since it already contains a non-zero value. TRAC's 24 local network includes connections to one or more DHCP 66 proxies (i.e., network host interface proxies). The DHCP 66 proxies accept the DHCP 66 messages originally from the CM 16 destined for DHCP 66 servers connected to network host interfaces available on the CMTS 12 since TRAC 24 has no direct access to DCHP 66 servers associated with network host interfaces available on the CMTS 12. The DHCP 66 proxies are not used in a typical the DHCP 66 discovery process known on the art.

One or more DHCP 66 proxies on TRAC's 24 local network recognizes the DHCPDISCOVER message and forwards it to one or more DHCP 66 servers associated with network host interfaces (e.g., IP 54 interfaces) available on the CMTS 12 at Step 146. Since the DHCP 66 giaddr-field 130 (FIG. 6) in the DHCPDISCOVER message sent by the CM 16 is already non-zero (i.e., contains the downstream IP address of the CMTS 12), the DHCP 66 proxies also leave the DHCP 66 giaddr-field 130 intact.

One or more DHCP 66 servers for network host interfaces (e.g., IP 54 interfaces) available on the CMTS 12 receive the DHCPDISCOVER message and generate a DHCP 66 offer message ("DHCPOFFER") at Step 148. The DHCP 66 offer message is an offer of configuration parameters sent from network host interfaces to the DHCP 66 servers and back to a network host client (e.g., the CM 16) in response to a DHCPDISCOVER message. The DHCP 66 offer message is sent with the message fields set as illustrated in Table 7. However, other field settings can also be used. The DHCP 66 yiaddr-field 126 (e.g., second message field from Step 102 of Method 92) contains an IP 54 address for a network host interface available on the CMTS 12 and used for receiving data packets from data network 28.

TABLE 7 DHCP 66 Parameter Description FLAGS 122 BROADCAST bit set to zero. YIADDR 126 IP 54 address from a network host interface to allow the CM 16 to receive data from data network 28 via a network host interface available on the CMTS
12. SIADDR 128 An IP 54 address for a TFTP 64 server to download configuration information for an interface host. CHADDR 132 MAC 44 address of the CM 16. SNAME 134 Optional DHCP 66 server identifier with an interface host. FILE 136 ATFTP 64
configuration file name for the CM 16.

DHCP 66 servers send the DHCPOFFER message to the address specified in the DHCP 66 giaddr-field 130 (i.e., the CMTS 12) from the DHCPDISCOVER message if associated network host interfaces (e.g., IP 54 interfaces) can offer the requested service (e.g., IP 54 service) to the CM 16. The DHCPDISOVER message DHCP 66 giaddr-field 130 contains a downstream channel IP address 80 of the CMTS 12 that was received by the CM 16 in TSI message 76. This allows the CMTS 12 to receive the DHCPOFFER messages from the DHCP 66 servers and send them to the CM 16 via a downstream channel on cable network 14.

At Step 150 in FIG. 7B, the CMTS 12 receives one or more DHCPOFFER messages from one or more DHCP 66 servers associated with the network host interfaces (e.g., IP 54 interfaces). THE CMTS 12 examines the DHCP 66 yiaddr-field 126 and DHCP 66
chaddr-field 132 in the DHCPOFFER messages and sends the DHCPOFFER messages to the CM 16 via cable network 14. The DHCP 66 yiaddr-field 126 contains an IP 54 address for a network host IP 54 interface available on the CMTS 12 and used for receiving IP
54 data packets from data network 28. The DHCP 66 chaddr-field 132 contains the MAC 44 layer address for the CM 16 on a downstream cable channel from the CMTS 12 via cable network 14. The CMTS 12 knows the location of the CM 16 since it sent the CM 16
a MAC 44 layer address in one or more initialization messages (e.g., TSI message 76).

If a BROADCAST bit in flags-field 124 is set to one, the CMTS 12 sends the DHCPOFFER messages to a broadcast IP 54 address (e.g., 255.255.255.255) instead of the address specified in the DHCP 66 yiaddr-field 126. The DHCP 66 chaddr-field 132 is still used to determine that MAC 44 layer address. If the BROADCAST bit in the DHCP 66 flags-field 122 is set, the CMTS 12 does not update internal address or routing tables based upon the DHCP 66 yiaddr-field 126 and the DHCP 66 chaddr-field 132 pair when a broadcast message is sent.

At Step 152, the CM 16 receives one or more DHCPOFFER messages from the CMTS 12 via cable network 14 on a downstream connection. At Step 154, the CM 16 selects an offer for IP 54 service from one of the network host interfaces (e.g., an IP interfaces 54) available on the CMTS 12 that responded to the DHCPDISOVER message sent at Step 142 in FIG. 7A and establishes a virtual IP 54 connection. The selected DHCPOFFER message contains a network host interface address (e.g., IP 54 address) in the DHCP 66 yiaddr-field 126 (FIG. 6). A CM 16 acknowledges the selected network host interface with DHCP 66 message sequence explained below.

After selecting and acknowledging a network host interface, the CM 16 has discovered an IP 54 interface address available on the CMTS 12 for completing a virtual IP 54 connection with data network 28. Acknowledging a network host interface is explained below. The virtual IP 54 connection allows IP 54 data from data network 28 to be sent to the CMTS 12 which forwards the IP 54 packets to the CM 16 on a downstream channel via cable network 14. The CM 16 sends response IP 54 packets back to data network 28 via the PSTN 22 and TRAC 24 if telephony return is used. The CM sends response IP packets back to the data network 28 via the CMTS 12 is a two-way cable network is used.

FIG. 8 is a block diagram illustrating an exemplary data-over-cable system 156 for the method illustrated in FIGS. 7A and 7B. Data-over-cable system 156 includes the DHCP 66 proxies ("P") 158, the DHCP 66 servers 160 and associated Network Host Interfaces ("NHI") 162 available on the CMTS 12. Multiple DHCP 66 proxies 158, the DHCP 66 servers ("S") 160 and network host interfaces 162 are illustrated as single boxes in FIG. 8. FIG. 8 also illustrates the DHCP 66 proxies 158 separate from TRAC
24. In one embodiment of the present invention, TRAC 24 includes integral DHCP 66 proxy functionality and no separate DHCP 66 proxies 158 are used. In such an embodiment, TRAC 24 forwards the DHCP 66 messages using the DHCP 66 giaddr-field 130 to the DHCP 66 servers 160 available on the CMTS 12.

FIG. 9 is a block diagram illustrating a message flow 162 of Method 140 (FIGS. 7A and 7B).

Message flow 162 includes the DHCP proxies 158 and the DHCP servers 160 illustrated in FIG. 8 Steps 142, 144, 146, 148, 150 and 154 of Method 140 (FIGS. 7A and 7B) are illustrated in FIG. 9. In one embodiment of the present invention, the DHCP proxies 158 are not separate entities, but are included in TRAC 24. In such an embodiment, the DHCP proxy services are provided directly by TRAC 24.

Resolving Addresses for Network Host Interfaces

Since the CM 16 receives multiple the DHCPOFFER messages (Step 152FIG. 7B) the CM 16 resolves and acknowledges one offer from a selected network host interface. FIGS. 10A and 10B are a flow diagram illustrating a Method 166 for resolving and acknowledging host addresses in a data-over-cable system. Method 166 includes a first network device that is connected to a first network with a downstream connection of a first connection type, and connected to a second network with an upstream connection of a second connection type. The first and second networks are connected to a third network with a third connection type. In one embodiment of the present invention, the first network device is the CM 16, the first network is cable network
14, the second network is the PSTN 22 and the third network is data network 28 (e.g., the Internet). The downstream connection is a cable television connection, the upstream connection is a telephony connection, and the third connection is an IP connection. However, the upstream connection and the data stream connection can both be cable television connections.

Turning to FIG. 10A, one or more first messages are received on the first network device from the first network on the downstream connection at Step 168. The one or more first messages are offers from one or more network host interfaces available on the first network to provide the first network device a connection to the third network. The first network device selects one of the network host interfaces using message fields in one of the one or more first messages at Step 170. The first network device creates a second message with a second message type to accept the offered services from a selected network host interface at Step 172. The second message includes a connection address for the first network in a first message field and an identifier to identify the selected network host interface in a second message field.

The first network device sends the second message over the upstream connection to the second network at Step 174. The second network uses the first message field in the second message to forward the second message to the one or more network host interfaces available on first network at Step 176.

A network host interface available on the first network identified in second message field in the second message from the first network device recognizes an identifier for the network host interface at Step 178 in FIG. 10B. The selected network host interface sends a third message with a third message type to the first network at Step 180. The third message is an acknowledgment for the first network device that the selected network host interface received the second message from the first network device. The first network stores a connection address for the selected network interface in one or more tables on the first network at Step 182. The first network will forward data from the third network to the first network device when it is received on the selected network host interface using the connection address in the one or more routing tables. The first network forwards the third message to the first network device on the downstream connection at Step 184. The first network device receives the third message at Step 186. The first network and the first network device have the necessary addresses for a virtual connection that allows data to be sent from the third network to a network host interface on the first network, and from the first network over the downstream connection to the first network device. Method 166 accomplishes resolving network interface hosts addresses from a cable modem in a data-over-cable with or without telephony return.

Method 166 of the present invention is used in data-over-cable system 10 with telephony return. However, the present invention is not limited to data-over-cable system 10 with telephony return and can be used in data-over-cable system 10 without telephony return by using an upstream cable channel instead of an upstream telephony channel.

FIGS. 11A and 11B are a flow diagram illustrating a Method 188 for resolving discovered host addresses in data-over-cable system 10 with telephony return. At Step 190 in FIG. 11A, the CM 16 receives one or more DHCPOFFER messages from one or more DHCP 66 servers 160 associated with one or more network host interfaces 162 (e.g., at Step 168 in Method 166). The one or more DHCPOFFER messages include the DHCP 66 fields set as illustrated in Table 7 above. However, other field settings could also be used. At Step 192, the CM 16 selects one of the DHCPOFFER messages (see also, Step 170 in Method 166). At Step 194, the CM 16 creates a DHCP 66 request message ("DHCPREQUEST") message to request the services offered by a network host interface
168 selected at Step 192. The fields of the DHCP request message are set as illustrated in Table 8. However, other field settings may also be used.

TABLE 8 DHCP 66 Parameter Description OP 110 Set to BOOTREQUEST. HTYPE 112 Set to network type (e.g., one for 10 Mbps Ethernet). HLEN 114 Set to network length (e.g., six for 10 Mbps Ethernet) HOPS 116 Set to zero. FLAGS 122 Set BROADCAST bit to zero. CIADDR 124 If the CM 16 has previously been assigned an IP address, the IP address is placed in this field. If the CM 16 has previously been assigned an IP address by the DHCP 66, and also has been assigned an address via IPCP, the CM 16 places the DHCP 66 IP 54 address in this field. YIADDR 126 IP 54 address sent from the selected network interface host in DCHPOFFER message GIADDR 130 CM 16 places the Downstream Channel IP 54 address 80 the CMTS 12 obtained in TSI message 76 on a cable downstream channel in this field. CHADDR 132 CM 16 places its 48-bit MAC 44 LAN address in this field. SNAME 134 DHCP 66 server identifier for the selected network interface host

The DHCPREQUEST message is used to "request" services from the selected IP 54 host interface 162 available on the CMTS 12 using a DHCP 66 server 160 associated with the selected network host interface 162. The DHCP 66 giaddr-field 130 (FIG. 6) includes the downstream channel IP address 80 for the CMTS 12 obtained in TSI message 76 (e.g., the first message-field from Step 172 of Method 166). Putting the downstream channel IP address 80 obtained in TSI message 76 allows the DHCPREQUEST message to be forwarded by TRAC 24 to DCHP 66 servers 160 associated with network host interfaces 162 available on the CMTS 12. The DHCP 66 giaddr-field 126 contains an identifier (e.g., second message field, Step 172 in Method 166) the DHCP 66 sname-field 134
contains a DHCP 66 server identifier 160 associated with the selected network host interface.

If the DHCP 66 giaddr-field 130 in a DHCP 66 message from a DHCP 66 client is non-zero, a DHCP 66 server 160 sends any return messages to a DHCP 66 server port on a DHCP 66 relaying agent (e.g., the CMTS 12) whose address appears in DHCP 66
giaddr-field 130. If DHCP 66 giaddr-field 130 is zero, the DHCP 66 client is on the same subnet as the DHCP 66 server, and the DHCP 66 server sends any return messages to either the DHCP 66 client's network address, if that address was supplied in the DHCP 66 ciaddr-field 124, or to the client's hardware address specified in the DHCP 66 chaddr-field 132 or to the local subnet broadcast address.

Returning to FIG. 11A at Step 196, the CM 16 sends the DHCPREQUEST message on the upstream connection to TRAC 24 via the PSTN 22. At Step 198, a DHCP 66 layer on TRAC 24 broadcasts the DHCPREQUEST message on its local network leaving DHCP 66
giaddr-field 130 intact since it already contains a non-zero value. TRAC's 24 local network includes connections to one or more DHCP 66 proxies 158. The DHCP 66 proxies 158 accept DHCP 66 messages originally from the CM 16 destined for the DHCP 66
servers 160 associated with network host interfaces 168 available on the CMTS 12. In another embodiment of the present invention, TRAC 24 provides the DHCP 66 proxy functionality, and no separate DHCP 66 proxies are used.

The one or more DHCP 66 proxies 158 on TRAC's 24 local network message forwards the DHCPOFFER to one or more of the DHCP 66 servers 160 associated with network host interfaces 162 (e.g., IP 54 interfaces) available on the CMTS 12 at Step 200 in FIG. 11B. Since DHCP 66 giaddr-field 130 in the DHCPDISCOVER message sent by the CM 16 is already non-zero (i.e., contains the downstream IP address of the CMTS 12), the DHCP 66 proxies leave 158 the DHCP 66 giaddr-field 130 intact.

One or more DHCP 66 servers 160 for the selected network host interfaces 162 (e.g., IP 54 interface) available on the CMTS 12 receives the DHCPOFFER message at Step 202. A selected the DHCP 66 server 160 recognizes a DHCP 66 server identifier in the DHCP 66 sname-field 134 or the IP 54 address that was sent in the DCHPOFFER message in the DHCP 66 yiaddr-field 126 from the DHCPREQUST message as being for the selected DHCP 66 server 160.

The selected DHCP 66 server 160 associated with network host interface 162 selected by the CM 16 in the DHCPREQUEST message creates and sends a DCHP 66 acknowledgment message ("DHCPACK") to the CMTS 12 at Step 204. The DHCPACK message is sent with the message fields set as illustrated in Table 9. However, other field settings can also be used. The DHCP 66 yiaddr-field again contains the IP 54 address for the selected network host interface available on the CMTS 12 for receiving data packets from data network 28.

TABLE 9 DHCP 66 Parameter Description FLAGS 122 Set a BROADCAST bit to zero. YIADDR 126 IP 54 address for the selected network host interface to allow the CM 16 to receive data from data network 28. SIADDR 128 An IP 54 address for a TFTP
64 server to download configuration information for an interface host. CHADDR 132 MAC 44 address of the CM 16. SNAME 134 DHCP 66 server identifier associated with the selected network host interface. FILE 136 A configuration file name for an network interface host.

The selected DHCP 66 server 160 sends the DHCACK message to the address specified in the DHCP 66 giaddr-field 130 from the DHCPREQUEST message to the CM 16 to verify the selected network host interface (e.g., IP 54 interface) will offer the requested service (e.g., IP 54 service).

At Step 206, the CMTS 12 receives the DHCPACK message from the selected DHCP 66 server 160 associated with the selected network host interface 162 IP 54 address(e.g., IP 54 interface). The CMTS 12 examines the DHCP 66 yiaddr-field 126 and the DHCP 66 chaddr-field 132 in the DHCPACK message. The DHCP 66 yiaddr-field 126 contains an IP 54 address for a network host IP 54 interface available on the CMTS 12 and used for receiving IP 54 data packets from data network 28 for the CM 16. The DHCP
66 chaddr-field 132 contains the MAC 44 layer address for the CM 16 on a downstream cable channel from the CMTS 12 via cable network 14.

CMTS 12 updates an Address Resolution Protocol ("ARP") table and other routing tables on the CMTS 12 to reflect the addresses in the DHCP 66 yiaddr-field 126 and the DHCP 66 chaddr-field 132 at Step 208. As is known in the art, ARP allows a gateway such as the CMTS 12 to forward any datagrams from a data network such as data network 28 it receives for hosts such as the CM 16. (For more information on ARP, see RFC-826, incorporated herein by reference).

CMTS 12 stores a pair of network address values in the ARP table, the IP 54 address of the selected network host interface from the DHCP 66 yiaddr-field 126 and a Network Point of Attachment ("NPA") address. In a preferred embodiment of the present invention, The NPA address is a MAC 44 layer address for the CM 16 via a downstream cable channel. The IP/NPA address pair are stored in local routing tables with the IP/NPA addresses of hosts (e.g., the CMs 16) that are attached to cable network 14.

At Step 210, the CMTS 12 sends the DHCPACK message to the CM 16 via cable network 14. At Step 212, the CM 16 receives the DHCPACK message, and along with the CMTS 12 has addresses for a "virtual connection" between data network 28 and the CM 16. When data packets arrive on the IP 54 address for the selected CM 16 they are sent to the CMTS 12 and the CMTS 12 forwards them using a NPA (i.e., a MAC 44 address) from the routing tables on a downstream channel via cable network 14 to the CM 16.

If a BROADCAST bit in flags field 124 is set to one in the DHCPACK, the CMTS 12 sends the DHCPACK messages to a broadcast IP 54 address (e.g., 255.255.255.255). The DHCP 66 chaddr-field 132 is still used to determine a MAC 44 layer address. If the BROADCAST bit in flags field 122 is set, the CMTS 12 does not update the ARP table or offer routing tables based upon the DHCP 66 yiaddr-field 126 and the DHCP 66 chaddr-field 132 pair when a broadcast message is sent.

FIG. 12 is a block diagram illustrating the message flow 214 of the Method 188 illustrated in FIGS. 11A and 11B. Message flow 214 includes the DHCP proxies 158 and the DHCP servers 160 illustrated in FIG. 8. Method Steps 194, 196, 198, 204,
208, 210and 212 of Method 188 (FIGS. 11A and 11B) are illustrated in FIG. 12. In one embodiment of the present invention, the DHCP proxies 158 are not separate entities, but are included in TRAC 24. In such an embodiment, the DHCP proxy services are provided directly by TRAC 24.

After Method 188, the CMTS 12 has a valid IP/MAC address pair in one or more address routing tables including an ARP table to forward IP 54 data packets from data network 28 to the CM 16, thereby creating a virtual IP 54 data path to/from the CM
16 as was illustrated in Method 92 (FIG. 5) and Table 3. the CM 16 has necessary parameters to proceed to the next phase of initialization, a downloading of a configuration file via TFTP 64. Once the CM 16 has received the configuration file and has been initialized, it registers with the CMTS 12 with a registration message and is ready to receive data from data network 14. Use of the registration message will be explained below.

In the event that the CM 16 is not compatible with the configuration of the network host interface 162 received in the DHCPACK message, the CM 16 may generate a DHCP 66 decline message ("DHCPDECLINE") and transmit it to TRAC 24 via the PSTN 22. A DHCP 66 layer in TRAC 24 forwards the DHCPDECLINE message to the CMTS 12. Upon seeing a DHCPDECLINE message, the CMTS 12 flushes its ARP tables and routing tables to remove the now invalid IP/MAC pairing. The CM 16 may also send the DHCPDECLINE message to the CMTS 12 on an upstream cable channel. The CMTS 12 will then forward the DHCPDECLINE message to the appropriate DHCP 66 server 160. If an IP 54 address for a network host interface is returned in a DHCPACK that is different from the IP 54
address sent by the CM 16 in the DCHCPREQUEST message, the CM 16 uses the IP 54 address it receives in the DHCPACK message as the IP 54 address of the selected network host interface for receiving data from data network 28.

One preferred embodiment of the present invention is described with respect to, but is not limited to a data-over-cable-system with telephony return. Method 188 can also be used with a cable modem that has a two-way connection (i.e., upstream and downstream) to cable network 14 and the CMTS 12. In a data-over-cable-system without telephony return, the CM 16 would broadcast the DHCPREQUEST message to one or more DHCP 66 servers 160 associated with one or more network host interfaces 162
associated with the CMTS 12 using an upstream cable connection on the data network 14 including the IP 54 address of the CMTS 12 in the DHCP 66 giaddr-field 130. Method 188 accomplishes resolving addresses for network interface hosts from a cable modem in a data-over-cable with or without telephony return, and without extensions to the existing DHCP protocol.

CPE Initialization in a Data-over-cable System

The CPE 18 also uses the DHCP 66 to generate requests to obtain IP 54 addresses to allow CPE 18 to also receive data from data network 28 via the CM 16. In a preferred embodiment of the present invention, the CM 16 functions as a standard BOOTP relay agent/DHCP Proxy 158 to facilitate CPE's 18 access to the DHCP 66 server 160. FIGS. 13A and 13B are a flow diagram illustrating a Method 216 for obtaining addresses for customer premise equipment such as the CPE 18. The CM 16 and the CMTS 12 use information from Method 214 to construct IP 54 routing and ARP table entries for network host interfaces 162 providing data to the CMCI 20 and to CPE 18.

Method 216 in FIGS. 13A and 13B includes a data-over-cable system with telephony return. A first network device with a second network device is used for connecting the first network device to a first network with a downstream connection of a first connection type, and for connecting to a second network with an upstream connection of a second connection type. The first and second networks are connected to a third network with a third connection type.

In one embodiment of the present invention, data-over-cable system with telephony return is data-over-cable system 10 with the first network device is the CPE 18 and the second network device is the CM 16. The first network is the cable television network 14, the downstream connection is a cable television connection, the second network is the PSTN 22, the upstream connection is a telephony connection, the third network is data network 28 (e.g., the Internet or an intranet) and the third type of connection is an IP 54 connection. However, the present invention is not limited to the network components described and other network components may also be used. A data-over-cable system without telephony return can also be used (e.g., a system with a two-way cable channel. Method 216 allows CPE 18 to determine an IP 54 network host interface address available on the CMTS 12 to receive IP 54 data packets from the data network 54, thereby establishing a virtual IP 54 connection with data network 28 via the CM 16.

Returning to FIG. 13A at Step 218, a first message of a first type (e.g., a DHCP 66 discover message) with a first message field for a first connection is created on the first network device. The first message is used to discover a network host interface address on the first network to allow a virtual connection to the third network.

At Step 220, the first network device sends the first message to the second network device. The second network device checks the first message field at Step 222. If the first message field is zero, the second network device puts its own network connection address into the first message field at Step 224. The second network device connection address allows the messages from network host interfaces on the first network to return messages to the second network device attached to the first network device. If the first message field is non-zero, the second network device does not alter the first message field since there could be a relay agent attached to the first network device that may set the first connection address field.

At Step 226, the second network device forwards the first message to a connection address over the upstream connection to the second network. In one embodiment of the present invention, the connection address is an IP broadcast address (e.g.,
255.255.255.255). However, other connection addresses can also be used.

The second network uses the first connection address in the first message field in the first message to forward the first message to one or more network host interfaces (e.g., IP 54 network host interfaces 162) available on first network at Step
228. One or more network host interfaces available on the first network that can provide the services requested in first message send a second message with a second message type with a second connection address in a second message field to the first network at Step 230 in FIG. 13B. The second connection address allows the first network device to receive data packets from the third network via a network host interface on the first network. The first network forwards the one or more second messages on the downstream connection to the second network device at Step 232. The second network device forwards the one or more second messages to the first network device at Step 234. The first network device selects one of the one or more network host interfaces on the first network using the one or more second messages at Step 236. This allows a virtual connection to be established between the third network and the first network device via the selected network host interface on the first network and the second network device.

FIGS. 14A and 14B are a flow diagram illustrating a Method 240 for resolving addresses for the network host interface selected by a first network device to create a virtual connection to the third network. Turning to FIG. 14A, at Step 240 one or more second messages are received with a second message type on the first network device from the second network device from the first network on a downstream connection at Step 242. The one or more second messages are offers from one or more protocol servers associated with one or more network host interfaces available on the first network to provide the first network device a connection to the third network. The first network device selects one of the network host interfaces using one of the one or more second messages at Step 244. The first network device creates a third message with a third message type to accept the offered services from the selected network host interface at Step 246. The third message includes a connection address for the first network in a first message field and an identifier to identify the selected network host interface in a second message field. to At Step 248, first network device equipment sends the third message to the second network device.

The second network device sends the third message over the upstream connection to the second network at Step 250. The second network uses the first message field in the third message to forward the third message to the one or more network host interfaces available on first network at Step 252.

A network host interface available on the first network identified in second message field in the third message from the first network device recognizes an identifier for the selected network host interface at Step 254 in FIG. 14B. The selected network host interface sends a fourth message with a fourth message type to the first network at Step 256. The fourth message is an acknowledgment for the first network device that the selected network host interface received the third message. The fourth message includes a second connection address in a third message field. The second connection address is a connection address for the selected network host interface. The first network stores the connection address for the selected network interface from the third message in one or more routing tables (e.g., an ARP table) on the first network at Step 258. The first network will forward data from the third network to the first network device via the second network device when it is received on the selected network host interface using the connection address from the third message field. The first network forwards the fourth message to the second network device on the downstream connection at Step 260. The second network device receives the fourth message and stores the connection address from the third message field for the selected network interface in one or more routing tables on the second network device at Step 262. The connection address for the selected network interface allows the second network device to forward data from the third network sent by the selected network interface to the customer premise equipment. At Step 264, the second network device forward the fourth message to the first network device. At Step 266, the first network device establishes a virtual connection between the third network and the first network device.

After Step 266, the first network, the second network device and the first network device have the necessary connection addresses for a virtual connection that allows data to be sent from the third network to a network host interface on the first network, and from the first network over the downstream connection to the second network and then to the first network device. In one embodiment of the present invention, Method 240 accomplishes resolving network interface hosts addresses from customer premise equipment with a cable modem in a data-over-cable with telephony return without extensions to the existing DHCP protocol.

Methods 216 and 240 of the present invention are used in data-over-cable system 10 with telephony return with the CM 16 and CPE 18. However, the present invention is not limited to data-over-cable system 10 with telephony return and can be used in data-over-cable system 10 without telephony return by using an upstream cable channel instead of an upstream telephony channel.

FIGS. 15A and 15B are a flow diagram illustrating a Method 268 for addressing network host interfaces 162 from CPE 18. At Step 270 in FIG. 15A, the CPE 18 generates a DHCPDISCOVER message broadcasts the DHCPDISCOVER message on its local network with the fields set as illustrated in Table 6 above with addresses for CPE 18 instead of the CM 16. However, more or fewer field could also be set in the DHCPDISCOVER message. he CM 16 receives the DHCPDISCOVER as a standard BOOTP relay agent at Step
272. The DHCPDISCOVER message has a MAC 44 layer address for CPE 18 in the DHCP 66 chaddr-field 132, which the CM 16 stores in one or more routing tables. As a BOOTP relay agent, the CM 16 checks the DHCP 66 giaddr-field 130 (FIG. 6) at Step 274. If the DHCP 66 giaddr-field 130 is set to zero, the CM 16 put its own IP 54 address into the DHCP 66 giaddr-field 130 at Step 276.

If the DHCP 66 giaddr-field 130 is non-zero, the CM 16 does not alter the DHCP 66 giaddr-field 130 since there could be another BOOTP relay agent attached to CPE 18 which may have already set the DHCP 66 giaddr-field 130. Any BOOTP relay agent attached to CPE 18 would have also have acquired its IP 54 address using a DCHP 66 discovery process (e.g., FIG. 12).

Returning to FIG. 15A, at Step 278, the CM 16 broadcasts the DHCPDISCOVER message to a broadcast address via the PSTN 22 to the TRAC 24. In one embodiment of the present invention, the broadcast address is an IP 54 broadcast address (e.g.,
255.255.255.255). At Step 280, one or more DHCP 66 proxies 158 associated with TRAC 24, recognize the DHCPDISOVER message, and forward it to one or more DHCP 66 servers 160 associated with one or more network host interfaces 162 available on the CMTS
12. Since the DHCP 66 giaddr-field 130 is already non-zero, the DHCP proxies 160 leave the DHCP 66 giaddr-field 130 intact. In another embodiment of the present invention, TRAC 24 includes DCHP 66 proxy 158 functionality and no separate DHCP 66 proxies
158 are used. In yet another embodiment of the present invention, the CM 16 broadcasts the DHCPDISCOVER message to the CMTS 12 on an upstream cable channel.

At Step 282 in FIG. 15B, the one or more DHCP servers 160 receive the DHCPDISCOVER message from one or more DHCP proxies, and generate one or more DHCPOFFER messages to offer connection services for one or more network host interfaces 162
associated with the CMTS 12 with fields set as illustrated in Table 7. The one or more DHCP servers 160 send the one or more DHCPOFFER messages to the address specified in the DHCP 66 giaddr-field 130 (e.g., the CM 16 or a BOOTP relay agent on CPE 18), which is an IP 54 address already contained in an ARP or other routing table in the CMTS 12. Since the CMTS 12 also functions as a relay agent for the one or more DHCP servers 160, the one or more DHCPOFFER messages are received on the CMTS 12 at Step
284.

The CMTS 12 examines the DHCP 66 yiaddr-field 126 and the DHCP 66 giaddr-field 130 in the DHCPOFFER messages, and sends the DHCPOFFER messages down cable network 14 to IP 54 address specified in the giaddr-field 130. The MAC 44 address for the CM 16 is obtained through a look-up of the hardware address associated with the DHCP 66 chaddr-field 130 (e.g., using ARP). If the BROADCAST bit in the DHCP 66 flags-field 122 is set to one, the CMTS 12 sends the DHCPOFFER message to a broadcast IP 54
address (e.g., 255.255.255.255), instead of the address specified in the DHCP 66 yiaddr-field 126. the CMTS 12 does not update its ARP or other routing tables based upon the broadcast DCHP 66 yiaddr-field 126 DHCP 66 chaddr-field 132 address pair.

Returning to FIG. 15B, the CM 16 receives the one or more DHCPOFFER messages and forwards them to CPE 18 at Step 286. the CM 16 uses the MAC 44 address specified determined by the DHCP 66 chaddr-field 132 look-up in its routing tables (e.g., ARP table) to find the address of CPE 18 even if the BROADCAST bit in the DHCP 66 flags-field 122 is set. At Step 290, CPE 18 receives the one or more DHCPOFFER messages from the CM 16. At Step 292, CPE 18 selects one of the DHCPOFFER messages to allow a virtual connection to be established between data network 28 and CPE 18. Method 266 accomplishes addressing network interface hosts from CPE 18 in data-over-cable system 10 without extensions to the existing DHCP protocol.

FIGS. 16A and 16B are a flow diagram illustrating a Method 294 for resolving network host interfaces from CPE 18. At Step 296, CPE 18 receives the one or more DHCPOFFER messages from one or more DHCP 66 servers 160 associated with one or more network host interfaces available on the CMTS 12. At Step 298, CPE 18 chooses one offer of services from a selected network host interface 162. At Step 300, the CPE 18 generates a DHCPREQUEST message with fields set as illustrated in Table 8 above with addresses for CPE 18 instead of the CM 16. However, more or fewer fields could also be set. At Step 302, CPE 18 sends the DHCPREQUEST message to the CM 16. At Step 304, the CM 16 forwards the message to TRAC 24 via the PSTN 22 (or to the CMTS 12 via an upstream cable channel if a two-way cable system is being used).

At Step 306, a DHCP 66 layer on TRAC 24 broadcasts the DHCPREQUEST message on its local network leaving the DHCP 66 giaddr-field 130 intact since it already contains a non-zero value. TRAC's 24 local network includes connections to one or more DHCP 66 proxies. The DHCP 66 proxies 158 accept the DHCP 66 messages originally from the CPE 18 destined for the DHCP 66 servers 160 associated with network host interfaces 162 associated with the CMTS 12. In another embodiment of the present invention, TRAC 24 provides the DHCP 66 proxy functionality, and no separate DHCP 66 proxies 158 are used.

One or more DHCP 66 proxies 158 on TRAC's 24 local network recognize the DHCPOFFER message and forward it to one or more of the DHCP 66 servers 160 associated with network host interfaces 162 (e.g., IP 54 interfaces) associated with the on the CMTS 12 at Step 308 in FIG. 16B. Since the DHCP 66 giaddr-field 130 in the DHCPDISCOVER message sent by CPE 18 is already non-zero, (i.e., set by the CM 16 the DHCP 66 proxies leave the DHCP 66 giaddr-field 130 intact.

One or more DHCP 66 servers 160 for the selected network host interfaces 162 (e.g., IP 54 interface) associated with the CMTS 12 receive the DHCPOFFER message at Step 310. A selected the DHCP 66 server 160 recognizes a DHCP 66 serv