Browse Prior Art Database

Method for Universal MAC Frame Encoding

IP.com Disclosure Number: IPCOM000109103D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 5 page(s) / 246K

Publishing Venue

IBM

Related People

Tantawy, AN: AUTHOR [+2]

Abstract

This article describes a method for universal encoding of MAC frames. The scheme is based on a frame format that captures all the control information encoded in existing MAC frames while providing for future expansion. The implementation of such a scheme is very useful in high-speed networking environments and in remote bridging applications.

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Method for Universal MAC Frame Encoding

       This article describes a method for universal encoding of
MAC frames.  The scheme is based on a frame format that captures all
the control information encoded in existing MAC frames while
providing for future expansion.  The implementation of such a scheme
is very useful in high-speed networking environments and in remote
bridging applications.

      Network interconnection devices, especially bridges, attached
to various heterogeneous networks (LANs or MANs) need to process and
relay MAC frames received from each of these networks.
Unfortunately, there exists today a number of MAC protocols that
require completely different encoding and formatting of data in their
respective MAC frames (or MAC Protocol Data Units).  Frame format
conversion is necessary when a frame is to be relayed between
different networks.  In case of multicasting, multiple conversions
are necessary.  This places a considerable burden on the bridge.  The
problem is twofold:
1. Every receiving port has to be able to convert the frame into the
format of any other network attached to the bridge.  This means that
N times (N-1) converters are needed in a bridge attached to N
different networks.
2. Every port has to process frame headers in the format used by the
attached network.  This means that N different processing systems are
required in a bridge attached to N different networks.

      In high-speed networks these problems are even more severe.
The processing of headers and trailers needs to be handled by special
hardware, if gigabit speeds are to be met.  Moreover, format
conversion has to be done by special hardware chips for the same
reason.  The simple solutions suggested above and currently practiced
become unwieldy in such situations.  A new method is clearly needed
and this method should be adapted to VLSI implementation.

      A similar but slightly different problem appears in Remote
Bridging applications (1,2).  The two "halves" of a remote bridge
need to exchange MAC frames relayed between them.  A receiving half
remote bridge must understand the format of the received MAC frame.
Multiport remote bridges face the same challenge but worsened by the
fact that every half bridge has to understand a number of MAC frame
formats.  Last, but not least, half bridges made by different
manufacturers cannot communicate with each other in the current
environment.  Standardization is needed in order to allow
interoperability among various equipment in a multi-vendor
environment and we believe that the proposed scheme can be the basis
for such a standard.
THE NORMALIZED DATA UNIT

      In order to solve the problems mentioned above, we suggest the
use of a universal format for MAC frames.  To be useful, such a
format should have the following characteristics:
1. All information in all current MAC frame formats should be fully
encodable in the universal format.
2. Extension to accommodate...