Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-02-16
2003-09-09
Ton, Dang (Department: 2666)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S465000
Reexamination Certificate
active
06618382
ABSTRACT:
FIELD OF THE INVENTION
The present invention is in the field of communication networks. In particular, the method and apparatus of one embodiment of the present invention is related to an auto-early packet discard mechanism for automatically enabling Asynchronous Transfer Mode (ATM) Adaption Layer 5 (AAL5) early packet discard on an ATM network.
BACKGROUND
Early Packet Discard (EPD) is used to increase bandwidth utilization in Internet Protocol (IP) networks. Current mechanisms for implementing EPD in ATM networks rely on a static configuration of altogether enabling or, disabling EPD.
FIG. 1
a
illustrates a static EPD configuration
10
where the, EPD is altogether turned on or off for a given network connection. The static EPD is implemented in ATM networks by detecting an End-Of-Frame (EOF) cell of an AAL5 packet by using the Payload Type Indicator (PTI) field of the ATM cell header. A single bit indicates if the cell is the EOF. A Start-Of-Frame (SOF) is inferred to be the next cell following the EOF cell.
FIG. 1
b
illustrates an exemplary network diagram. Network communication equipment
12
such as an ATM switch is used by a core service provider
11
that sells the use of a virtual connection (VC)
14
to his customers
15
. In the illustrated embodiment, customer
15
may include an access service provider
16
, who then sells the connection
14
to an end user
18
. In the alternative, the core service provider
11
may act as an access service provider, in which case the customer
15
may be the end user
18
.
In cases of multiple network hierarchy as illustrated in
FIG. 1
b
, a service provider
11
may sell a connection to a second service provider
16
, and therefore may not know the type of traffic that is going to be run across the connection
14
. For example, the second service provider
16
may be selling the connection to an end user
18
using a voice application. For voice application, data types are not packet based but are encapsulated into single cells for transmission one cell at a time. This is in contrast to applications carrying a frame-based protocol, such as Internet Protocol (IP) traffic which encapsulates traffic onto ATM cells using what is referred to as the Asynchronous Transfer Mode (ATM) Adaption Layer 5 (AAL5). More specifically, AAL5 segments data packets into cells at the source of the ATM layer link, passes the cells to the ATM network for transmission and reassembles the cells back into data packets at the destination. When packets are converted into cells, multiple ATM cells are generated per packet, in which case only the last cell identifies the end of the data packet.
One disadvantage is that the service provider
11
does not know which data protocol is to be applied to the connection
14
. Further, if a cell is to be discarded, it is more efficient to discard all of the cells belonging to that data packet at the point of discard (the original service provider
11
) and free up the bandwidth downstream of that point within the service provider
11
's network for other customer applications.
Given the currently available technology, a service provider must statically turn on the EPD feature of the communication equipment
12
to have the extra efficiency of the network bandwidth. However, if the EPD feature is turned on, but the end user
18
does not use frame-based traffic, and instead uses another type of traffic service, a discard of the first cell of the data packet responsive to any single cell discard leads to loss of connectivity of the data being transmitted. This is because the EPD feature continues to look for the indication to stop discarding by waiting for an EOF. Such indication never occurs since only AAL5 traffic uses the EOF indication bit in the ATM header. Thus, in order to take advantage of the EPD feature, a service provider is required to reconfigure a connection to turn EPD off every time the end user changes. However, in many cases the service provider may not know that the end user has changed, and thus the traffic protocol has changed. In these cases, it is not feasible for the service provider to apply the EPD feature to the communication equipment
12
.
BRIEF SUMMARY OF THE INVENTION
A method for automatically enabling early packet discard mode on a cell switching network is disclosed. The method includes the steps of counting every non-end of the frame data cell that arrives on a network connection, comparing the number of non-end of the frame data cell to a predetermined threshold value to determine whether the traffic arriving on the network connection is a frame based traffic and enabling early packet discard if the traffic is frame based.
This amendment does not add new matter and is supported in the specification.
Other features and advantages of the invention will be apparent from the detailed description and drawings provided herein.
REFERENCES:
patent: 5764641 (1998-06-01), Lin
patent: 6282171 (2001-08-01), Adams et al.
patent: 6345037 (2002-02-01), St-Denis et al.
Y. Li and S. Elby. TCP/IP Performance and Behavior Over an ATM Network. 1996 IEEE. pp. 1-9.*
H. Chiou and Z. Tsai. Performance of ATM Switches with Age Priority Packet Discarding under the ON-OFF Source Model. 1998 IEEE. pp. 931-938.*
M. Casoni. Early Packet Discard with Diverse Management Policies for EOM Cells. 1997 IEEE. pp. 33-37.*
Nathan Harwell, TCP Over ATM, Internet Web Site, Nov. 5, 1998, 5, http://ils.unc.edu/atm/.
Bergen Christopher D.
Divivier Robert J.
Blakeey, Sokoloff, Taylor & Zafman LLP
Cisco Technology Inc.
Ton Dang
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