Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-04-23
2002-04-09
Horabik, Michael (Department: 2664)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S457000, C709S222000
Reexamination Certificate
active
06370147
ABSTRACT:
FIELD OF INVENTION
The present invention relates to communications in computer networks. More specifically, it relates to a method addressing of passive network hosts in a 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 30+ Mbps.
The Internet, a world-wide-network of interconnected computers, provides multi-media content including audio, video, graphics and text that 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 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 30+ Mbps which is a much larger data rate than can be supported by a modem used over a serial telephone line.
However, most cable television networks provide only unidirectional cable systems, supporting only a “downstream” 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, such as a public switched telephone network provided by AT&T and others, (i.e., a “telephony return”) 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.
When a cable modem used in the data-over-cable system with telephony return is initialized, a connection is made to both the cable modem termination system via the cable network and to the telephony remote access concentrator via the public switched telephone network. As a cable modem is initialized, it will initialize one or more downstream channels (i.e., downstream connections) to the cable modem termination system via the cable network or the telephony remote access concentrator via the public switched telephone network.
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.
Many data-over-cable systems in the prior art use a Dynamic Host Configuration Protocol (“DHCP”) as a standard messaging protocol to allocate network addresses such as Internet Protocol (“IP”) addresses. The network addresses are allocated to network devices such as cable modems, customer premise equipment (e.g., customer computers) and other network devices that have a Dynamic Host Configuration Protocol stack. As is known in the art, Dynamic Host Configuration Protocol is a protocol for passing configuration information such as network addresses to network devices on a network. IP is an addressing protocol designed to route traffic within a network or between networks.
There are several problems with using Dynamic Host Configuration Protocol to obtain a network address in a data-over-cable system. Many passive network devices (e.g., a printer, facsimile machine, customer computer, etc.) used in a data-over-cable system do not have a Dynamic Host Configuration Protocol stack. As a result, such devices are not able to obtain a network address (e.g., an IP address) via Dynamic Host Configuration Protocol. This limits the type of network devices that can be used in a data-over-cable system. Dynamic Host Configuration Protocol could be extended or modified to handle non-Dynamic Host Configuration Protocol network devices. However, this may not be desirable for Dynamic Host Configuration Protocol, which was originally designed for a specific purpose. In addition, Dynamic Host Configuration Protocol extensions would require upgrading existing network devices (e.g., cable modems, cable modem termination systems, etc.) and Dynamic Host Configuration Protocol servers including these on a large number of third party platforms. This would take a considerable amount of time and be very expensive to implement. It is desirable to use passive network devices without a Dynamic Host Configuration Protocol stack in a data-over-cable system.
SUMMARY OF THE INVENTION
In accordance with preferred embodiments of the present invention, some of the problems associated with allocating network addresses to passive network devices in a data-over-cable system are overcome. A method for addressing passive network devices in a data-over-cable system is provided. A passive network device is a network device such as a printer, facsimile machine, customer computer or other passive network device that does not have a Dynamic Host Configuration Protocol stack. The method allows passive network devices be used in a data-over-cable system.
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 proceed with references to the accompanying drawings.
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3Com Corporation
Duong Frank
Horabik Michael
McDonnell & Boehnen Hulbert & Berghoff
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