Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-09-11
2001-03-20
Olms, Douglas W. (Department: 2661)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S400000
Reexamination Certificate
active
06205149
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
The present invention is generally related to telecommunications networks, and more particularly to implementing Quality of Service (“QoS”) processing control within such networks.
Devices such as bridges and routers are employed to move data units between end-stations in a telecommunications network. The data units may represent various types of traffic including voice, video and computer data. Because some traffic may be associated with real time communication, processing of certain data units may be particularly time critical. For example, processing delay or loss of data units associated with a real time voice or video transmission could significantly degrade the quality of such communication. However, delays in exchange of some types of computer data may not significantly affect the quality of such communication. It may also be desirable to prioritize traffic within a given type of communication.
One method for prioritizing data units in a telecommunications network is with QoS parameters. Each data unit within the telecommunications network includes a header portion and a data portion. The header portion includes information for handling the data unit such as Source Address and Destination Address information. The header may also include a QoS priority indicator. It is known to insert QoS information in the transport layer of the header. Devices which receive and retransmit data units within the telecommunications network then examine the QoS portion of the header of such data units and assign priority accordingly. However, QoS has not yet been implemented in an effective manner.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention, Quality of Service (“QoS”) variables for data units of at least one predetermined protocol Type are stored in a cache memory. For data units in a one way connection (“flow”) with identified Source Address and Destination Address, thirteen bytes selected out of the Internet Protocol (“IP”) header are employed as at least a portion of a key to perform a cache lookup to obtain at least one QoS variable. The QoS variable is employed to prioritize the data unit for processing.
Enhanced performance is provided for data units of a specified protocol type that are associated with a flow. Both routing and QoS information can be loaded into the cache. Such routing and QoS information can then be retrieved by executing a single cache lookup.
Token buckets may be employed to facilitate QoS implementation. A token bucket is associated with at least one flow. Tokens are then added to the token bucket at specified time intervals. A counter is employed to track token count, and the rate at which tokens are added indicates a rate limit for frames that can be scheduled through the token bucket. The token count indicates the number of bytes that can be sent through the bucket, thereby defining a transmission rate limit.
In order to further facilitate smooth operation the bridge/router can implement a Random Early Drop (“RED”) procedure. Logic circuits generate a “congested ports” bitmask to indicate which output ports are deemed to be close to overflowing. For each output port which is indicated to be congested, the logic circuits configure a “RED shift value.” The RED shift value is the length in bits of a bitmask that is ANDed with a random number to yield a result, N, that indicates a number of frames to be queued. The Nth frame is intentionally dropped. Hence, a relatively small number of packets are dropped such that end-stations recognize the situation and respond by transmitting at a lower rate, thereby relieving congestion and reducing the chance that output queues will overflow.
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Flanders John A.
Giacobbe Paul J.
Lemaire Thomas A.
Lipschutz David
Ready David C.
3Com Corporation
Olms Douglas W.
Pizarro Ricardo M.
Weingarten, Schurgin Gagnebin & Hayes LLP
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