Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
2000-02-11
2004-03-30
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S230000
Reexamination Certificate
active
06714516
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to telecommunications networks. More particularly, but not by way of any limitation, the present invention relates to a congestion control mechanism for use with an access multiplexer disposed in an access network portion of a telecommunications network, wherein the access multiplexer receives message flows from the network and a plurality of users.
2. Description of Related Art
The remote access market is undergoing a major metamorphosis. Three factors serve as catalysts for change. The first is the growing number of users, for example, small office/home office (SOHO) users, demanding high performance Internet and remote access for multimedia. The second factor is the Telecommunications Reform Act, which is fostering broader competition through deregulation. The third and final factor is congestion in the Public Switched Telephone Network (PSTN), originally designed and developed for voice-only traffic.
There have been several important advances in telecommunications technology that enable high rates of throughput in carrier networks backbone connections. For example, by implementing Asynchronous Transfer Mode (ATM) networking technology over a Synchronous Optical Network (SONET)/Synchronous Digital Hierarchy (SDH) physical layer, carrier networks can achieve data rates of up to several hundred megabits per second (Mbps). However, efforts to meet the bandwidth demand for remote access are beset by the limitations of the existing twisted-pair copper cable infrastructure provided between a carrier's central office (CO) and a subscriber's remote site, typically referred to as the local loop. In the telecommunications art, these limitations are sometimes collectively described as the “last-mile” problem.
Current advances in technology are making it possible to get more bandwidth from the existing twisted-pair copper cable infrastructure. One of these developments is the Digital Subscriber Line (DSL) technology which utilizes the local loop telephone wiring already installed to virtually every home and business in the world, but does not depend on the rest of the PSTN infrastructure.
DSL is a modem technology for converting existing twisted-pair telephone lines into access paths for multimedia and high-speed data communications. Some versions of this technology are asymmetric, with different data rates in the downstream and upstream directions (to and from the subscriber, respectively). Others are symmetric, providing the same data rate both upstream and downstream. Regardless of the version, DSL technology provides three distinct advantages: (i) separation of voice and data communications, (ii) ability to implement the technology incrementally and inexpensively, and (iii) effective utilization of the open market place created by local loop deregulation.
An Asymmetric Digital Subscriber Line (ADSL) circuit connects an ADSL modem on each end of a twisted-pair telephone line, creating three information channels—a high speed downstream channel, a medium speed duplex channel, and depending on the implementation of the ADSL architecture, a Plain Old Telephone Service (POTS ) or an Integrated Services Digital Network (ISDN) channel. The POTS/ISDN channel is split off from the digital modem by filters, thus guaranteeing uninterrupted POTS/ISDN connectivity, even if ADSL fails. The high speed channel ranges from 1.5 to 6.1 Mbps of throughput, while duplex rates range from 16 to 640 kilobits per second (Kbps).
With the deployment of DSL technologies for remote access, it is now possible to establish end-to-end broadband connectivity over packet-switched networks such as ATM networks. As is well known, one of the characteristics of ATM networks is that they are connection-oriented, that is, before two end systems can communicate they need to establish a connection between them. However, unlike circuit-switched networks (e.g., the Public Switched Telephone Network or PSTN), the connection between the two end points does not consume a fixed bandwidth. Instead, bandwidth is allocated statistically, so that a large number of connections can share the bandwidth of individual links in the network. Since these connections are not dedicated bandwidth channels, they are typically referred to as “virtual channel connections” (VCCs) or “virtual circuits” (VCs).
VCCs between two ATM endpoints can be established in one of two ways. In the provisioning method, the virtual circuits are permanently configured and left in place until the subscribers want them to be removed. Accordingly, such circuits are known as permanent virtual circuits (PVCs). Typically, no special signaling protocol is necessary to handle control signaling (e.g., set-up and tear-down) of the PVCs. On the other hand, virtual circuits can also be established on demand and such circuits are called switched virtual circuits (SVCs). These SVCs are created and destroyed dynamically as needed and, accordingly, require a signaling protocol for exchanging messages necessary to set up and tear down SVC connections. Such a protocol, known as Service Specific Connection Oriented Protocol (SSCOP) has been specified in the ATM Adaptation Layer (AAL) for effectuating the Broadband ISDN (B-ISDN) signaling architecture in ATM networks. The SSCOP is defined by the ITU as ITU-T Recommendation Q.2110 and is incorporated by reference herein.
The SSCOP provides connection control and governs the message transmission process between a receiver and a transmitter disposed in an SVC. In the context of the ADSL technology, an access multiplexer—which is provided as a node that concentrates a plurality of ADSL lines from users (i.e., customer premises equipment or CPE) and is coupled to the carrier network via a Point of Presence (POP) switch—operates as an SSCOP receiver for traffic emanating from the users as well as the network itself.
Those skilled in the art should appreciate that the access multiplexer node can experience heavy amounts of signaling traffic from the users, the network, or both, and, accordingly, its resources (i.e., processor resources, buffer availability, etc.) may become overloaded. Although the SSCOP provides a flow control mechanism by way of a credit window that is granted by the receiver to the transmitter, there are certain deficiencies and drawbacks associated therewith.
First, the SSCOP Recommendation does not specify how the credit window needs to be managed by the receiver when the receiver experiences traffic overload, i.e., congestion. While the receiver can update a message sequence indicator that is transmitted back to the transmitter to indicate the highest number of messages it can accept, the Recommendation provides that the updating procedure is implementation-specific and not subject to standardization. Accordingly, there is a need to address the issue of credit window management in the context of congestion in a receiver.
Second, the SSCOP treats every call or user equivalently without taking into account whether some users/calls use up the resources more rapidly than others. In other words, some users may be sending message packets fast enough to tie up the resources unfairly. Accordingly, the resources of a receiver may be overloaded due to an imbalance of the loading itself, and the SSCOP does have any precautions against such unequal use patterns.
Based on the foregoing, it should be apparent that in order to address these and other problems of the state of the art set forth above, what is needed is a congestion control solution for use with receivers operating a communication protocol such as the SSCOP that advantageously offers a mechanism for throttling message flows from transmitters based on the overload conditions. It would be of further advantage to provide a congestion control method that is capable of isolating malfunctioning users by restricting their credit window sizes. The present invention provides such a solution.
SUMMARY OF THE INVENTION
Accordingly, the present invention advantageously provides a
Alcatel
Danamraj & Youst P.C.
Hoersten Craig A.
Hsu Alpus H.
Sewell V. Lawrence
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