Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
2000-09-28
2004-07-20
Patel, Ajit (Department: 2664)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S486000, C375S222000
Reexamination Certificate
active
06765925
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to data transmission networks and, more particularly, the invention relates to maintaining and/or transferring user/configuration state data when changing a network device between data transmission systems.
BACKGROUND OF THE INVENTION
FIG. 1
schematically shows a well known network arrangement for connecting various types of computer systems (e.g., personal computers and Internet appliances) with the Internet. Such arrangement includes a computer system that communicates with the Internet via an Internet Service Provider (“ISP”). To provide the data connection to the ISP, the computer is coupled with a modem that modulates and demodulates its communications with the ISP.
There are a variety of different types of modem technologies currently available. One widely used and inexpensive type of modem, known as a “telephone modem,” connects with the ISP via the public switched telephone network (i.e., via the telephone system). Currently available telephone modems commonly operate at maximum speeds of about 53-56 kilobits per second (Kbps).
Although relatively inexpensive and easy to use, telephone modems do not provide enough bandwidth for many users. Accordingly, other types of modems have been developed to provide bandwidths that are multiple times larger than those provided by telephone modems. One such type of modem, known as a “cable modem,” typically provides speeds in the megabits per second (Mbps) range. As the name suggests, instead of using the telephone system, cable modems communicate with an ISP through the cable network commonly used for television transmission (i.e., transmission systems commonly referred to as providing “cable TV”).
Cable modems communicate with a head end base unit (typically controlled by a cable operator that acts as an ISP) that provides the computer system with a connection to the Internet. Among other functions, the head end base unit (known as a cable modem termination system and referred to herein as a “CMTS”) includes the logic for controlling the connection with the cable modem. For example, the CMTS includes memory for storing state information that defines the various parameters of the cable modem connection, and logic for applying the state information to the connection. Exemplary state information (discussed below) may include the type of service a computer system is to receive from the ISP (e.g., premium service for enhanced functionality, or basic service for a simple connection to the Internet), security data, maximum bandwidth permitted for use by the computer system, and policy data.
Among other things, state information may be considered to be information that relates to the state of a given cable connection. Specifically, when joining the cable network, there are a number of steps that a cable modem must execute to establish a steady state connection (see, for example, the well known DOCSIS standard, noted below). Namely, in addition to establishing physical communication (e.g., conventional executing synchronization and ranging operations), a cable modem must execute a registration process, and retrieve configuration information. These processes may include authentication, as well as the initialization of security associations. Various class of service information also may be provided to the cable modem and/or the CMTS based upon the service agreements that the user has with the ISP. All of this information is part of the state information associated with the cable modem. In addition, during operation, a cable modem can perform additional operations that may add, delete or change its state information. For example, a given cable modem may establish a flow with a specific Quality of Service to execute an particular application, such as voice-over-IP.
Cable network systems are broadband systems and thus, allow multiple channels to co-exist on a single system. Accordingly, one CMTS can communicate with multiple cable modems simultaneously. To that end, current CMTSs often include a plurality of channels that each can be used by one or more cable modems. When data traffic on one channel becomes too heavy, the CMTS can cause one or more cable modems using such channel to use a different channel. To that end, the CMTS transmits a channel change message to such modems. In response, the receiving cable modems begin using the different channel. All state information relating to such cable modems (i.e., state information relating to their coupled computer system) thus is maintained by the single CMTS. For additional information relating to cable modems and their interaction with a CMTS, see, “Data-Over-Cable Service Interface Specifications, Radio Frequency Interface Specification,” which is a cooperative effort under the direction of Cable Television Laboratories, Inc., with a copyright of 1999 and 2000 and document control number SP-RF1v1.1-104-000407, the disclosure of which is incorporated herein, in its entirety, by reference. This specification is commonly referred to in the art by the acronym “DOCSIS.”
There are instances, however, where it would be desirable to move one or more cable modems to one or more different channels on a different CMTS. For example, all channels on a single CMTS may be full, while another CMTS may have some available channels. One problem with changing to a channel on another CMTS, however, is that such a change loses state information for the changed cable modem.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, an apparatus and method of maintaining state information for a network device changing from a first channel (in communication with a first base unit) to a second channel (in communication with a second base unit) communicates with at least one of the first base unit and an intermediate network device to ascertain the state information. Once the state information is ascertained, it is applied to the communication of the network device with the second base unit. Both the first and second base units are independently operable network devices in a data transmission network.
In some embodiments, the state information is ascertained by receiving a message with the state information from the first network device. In other embodiments, the state information is ascertained by receiving a message with the state information from an intermediate device. In still other embodiments, the state information is ascertained by retrieving the state information from a memory device that is accessible by the second base unit.
The transmission network may be a wireless network, a cable system, or other type of broadband network. When a cable system (e.g., a DOCSIS system), the base units are cable modem termination systems. The state information may relate to use of the second channel by the network device. Among others things, the state information may relate to at least one of bandwidth, quality of service, throughput, security, service level agreements, and policy data. In illustrative embodiments, the second base unit communicates with the one of the first base unit and the intermediate network device, and applies the state information. In addition, the second base unit may determine that it is to communicate with the network device via the second channel. Moreover, the state data may be applied by transmitting a message having the state information to the network device.
In accordance with other aspects of the invention, a system for maintaining state information relating to a network device changing from a first channel to a second channel includes a first base unit, a second base unit, and a state module capable of obtaining the state information for the second base unit. The first base unit has a first interface to the first channel, while the second base unit has a second interface to the second channel. The first base unit also includes the state information, while the first and second base units are independently operable. Among other locations, the state module may exist as a separate entity, or may be embedded in either of the
Sawyer Wilson
Ulm John M.
Bromberg & Sunstein LLP
Patel Ajit
LandOfFree
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