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Mechanism for Priority Traffic Handling on Single-Queue Network Adapters

IP.com Disclosure Number: IPCOM000114502D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 2 page(s) / 90K

Publishing Venue

IBM

Related People

Bisdikian, C: AUTHOR [+4]

Abstract

Disclosed is a traffic scheduling mechanism for allowing current internetworking devices, e.g., bridges, based on network adapters with single-priority transmission queues, "single-queue(s)" for short, to handle multi-priority traffic without hardware changes to the adapters. The disclosed mechanism protects the customer investment on single-queue network adapters that are currently widely installed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Mechanism for Priority Traffic Handling on Single-Queue Network Adapters

      Disclosed is a traffic scheduling mechanism for allowing
current internetworking devices, e.g., bridges, based on network
adapters with single-priority transmission queues, "single-queue(s)"
for short, to handle multi-priority traffic without hardware changes
to the adapters.  The disclosed mechanism protects the customer
investment on single-queue network adapters that are currently widely
installed.

      As multimedia applications become more pervasive, demands on
the current networks become higher.  One way to deal with this
problem on, say, token-ring networks is to have bridges that are able
to handle traffic streams of different priority levels, with each
priority level utilizing its own separate transmission queue.  In
such a multi-queue/priority bridge, the multimedia traffic is
assigned a high priority due to its strict delay constraints.

      Unfortunately, most of today's token-ring bridges cannot handle
properly priority traffic because they are based on single-queue
token-ring adapters that do not differentiate between traffic streams
of different priority level.  In the latter adapters, frames are
stored in the adapter memory as soon as they become ready for
transmission.  Since the adapter memory is large, 64Kbytes or even
more, a large number of low priority frames may be in the adapter
memory, i.e., the transmission queue, by the time a high priority
frame arrives.  This high priority frame will wait a critically long
time before it is allowed transmission into the network.  Therefore,
such bridges cannot be part of networks when multimedia applications
are deployed.

      Replacing single-queue network adapters with multi-queue
adapters is an expensive and demanding solution.  The disclosed
mechanism allows the proper handling of traffic streams of different
priority levels on a single-queue network adapter with minimal
effort.  For ease of presentation two priority levels are assumed,
the high and the low priority levels.  In the disclosed mechanism,
the priority traffic is "captured"  prior to its admission to the
adapter memory.  Hence, the low priority and the high priori...