Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1998-12-21
2003-12-02
Kizou, Hassan (Department: 2662)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S389000, C370S401000, C375S222000, C709S218000
Reexamination Certificate
active
06657991
ABSTRACT:
FIELD OF INVENTION
The present invention relates to communications in computer networks. More specifically, it relates to a method and system for provisioning network addresses 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 uni-directional 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.
As was just described, many data-over-cable systems dynamically assign a network address, such as an Internet Protocol address, for a network device, such as a cable modem or customer premise equipment, with the Dynamic Host Configuration Protocol from a network address pool. When a cable modem or customer premise equipment is disconnected from the data-over-cable system, the dynamically assigned network addresses are returned to the network address pool for use by other network devices.
There are several problems associated with dynamically allocating network addresses to network devices. One problem is that certain types of cable modems are designed to be “always-on devices” with their own “permanent” Internet Protocol addresses (e.g., have an “indefinite” Internet Protocol lease time). The “always-on” cable modems are typically used for services such as Voice over Internet Protocol (“VoIP”) that typically require instant access to a data-over-cable system. In effect, each “always-on” cable modem necessitates that a data-over-cable system reserve one network address, such as an Internet Protocol address, for each cable modem connected to the data-over-cable system, and at least one more network address for customer premise equipment or other network devices that are connected to the cable modems. This may severely deplete the available pool of network addresses and prevent cable modems that are not “always-on” from using the data-over-cable system.
Another problem is that for “always-on” cable modems, a data-over-cable system needs to maintain a pool of Internet Protocol addresses typically at least twice the number of cable modems connected to the data-over-cable system. In many instances, this number may be as high as three, four, five or more times the number of always-on cable modems since many always-on cable modems are typically connected to multiple network devices, which in turn require their own network addresses on the data-over-cable system. For example, one cable modem may service multiple customer devices (e.g., 5-10 customer computers) on a
Akgun Ali
Beser Nurettin B.
Fijolek John G.
Sangston Steven W.
3Com Corporation
Kizou Hassan
McDonnell & Boehnen Hulbert & Berghoff
Tsegaye Saba
LandOfFree
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