Browse Prior Art Database

Connectionless Server using Source Routing and ATM

IP.com Disclosure Number: IPCOM000109104D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 4 page(s) / 163K

Publishing Venue

IBM

Related People

Le Boudec, J: AUTHOR [+3]

Abstract

Disclosed are two approaches which enhance the CCITT method for supporting a global connectionless data service (*).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 42% of the total text.

Connectionless Server using Source Routing and ATM

       Disclosed are two approaches which enhance the CCITT
method for supporting a global connectionless data service (*).

      The example shown in the figure illustrates the proposal.  The
user terminals participating in the service are connected to a
network of CLSFs (Connectionless Service Functions).  Every terminal
has at least one dedicated ATM (Asynchronous Transfer Mode)
connection to one CLSF. The CLSFs themselves are also connected
together by means of ATM connections.  In the figure, the identities
of these ATM connections are indicated.  So far, this is identical to
the CCITT approach.

      The first approach is called full source routing (FSR) because
the source user includes in its message the full route to the
destination user.  For that aim, a routing database is introduced,
which contains the following information:
1.   Access information:  User address (e.g., E. 164 address)
together with the identities of the CLSFs that can provide
connectivity to that user and the identities of the ATM connections
between that user and the corresponding CLSFs.
2.   Network information:  Identities and characteristics of the ATM
connections interconnecting the CLSFs.
Based on these two kinds of information, the routing database is able
to compute the route between any pair of user terminals.

      The procedure used for communication between two user terminals
is as follows.  Assume that the sending terminal T1 has a message to
the partner terminal T2.  Before sending the message, terminal T1 has
to determine a possible route to destination terminal T2.  This is
done by accessing the routing database and asking for this route.
The result of the routing database query is a list of connection
identities describing the route from the source user through
(possibly multiple) intermediate CLSFs to the destination user.  In
the example shown in the figure, the list obtained by T1 for reaching
T2 is "aO i1 b1".  As mentioned before, this route is calculated by
the routing database based on the information stored in it.

      The first element of the list, a0, identifies the ATM
connection terminal T1 should use for transferring the cells to CLSF
A.  The remaining elements, i1 and b1, build the routing information
that terminal T1 adds to the beginning of its connectionless message.
The resulting message is then segmented.  Since the routing
information is added to the beginning message, it is contained in the
BOM (Begin Of Message) segment.  All resulting segments are then sent
to CLSF A using the ATM connection AO.

      The functions activated by the CLSF upon reception of a segment
from the ATM layer are as follows:
1.   Receiving a BOM segment:
      When the CLSF receives a segment of the BOM type, it uses the
first element of the routing information to determine the outgoing
ATM connection over which the message has to be transmitte...