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Architecture to Implement the Segmentation Function for Asynchronous Transfer Mode

IP.com Disclosure Number: IPCOM000110500D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 3 page(s) / 106K

Publishing Venue

IBM

Related People

Patel, BV: AUTHOR [+3]

Abstract

Disclosed is an apparatus to perform the segmentation of out-going AAL PDUs (ATM Adaptation Layer Protocol Data Units) into ATM (Asynchronous Transfer Mode) cells conforming to SAR (Segmentation And Reassembly) sublayer specifications defined by the ATM standards [*].

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

Architecture to Implement the Segmentation Function for Asynchronous Transfer Mode

       Disclosed is an apparatus to perform the segmentation of
out-going AAL PDUs (ATM Adaptation Layer Protocol Data Units) into
ATM (Asynchronous Transfer Mode) cells conforming to SAR
(Segmentation And Reassembly) sublayer specifications defined by the
ATM standards [*].

      A format for segmentation and reassembly of AAL messages into
ATM cells is defined in the segmentation and reassembly (SAR)
sublayer of ATM, as shown in Fig. 1.  According to this format, in
addition to the ATM header, each ATM cell carries 44 bytes of data
and 2 bytes of segment header and segment trailer each.  There are
four possible segment types indicating which part of the AAL frame is
being carried in a segment: (1) Beginning of Message (BOM), (2)
Continuation of Message (COM), (3) End of Message (EOM), and (4)
Single Segment Message (SSM).  The sequence number ranges between 0
and 15 and cycles through to number consecutive segments of a packet;
the value is incremented relative to the previous value for a
particular VCI/MID value.  The MID (Multiplexing ID) is the
identifier used in combination with the VCI (Virtual Circuit ID) for
reassembly of the packets.  For connection-oriented service (e.g.,
AAL 3), each connection itself represents segments arriving in the
order of transmission, and therefore, all cells transferred using a
VCI must arrive in order.  Since cells are not multiplexed for
connection-oriented service, only the VCI is used for connection and
reassembly.  For conn...