Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!MIRSA.INRIA.FR!Christian.Huitema
From: Christian.Huitema@MIRSA.INRIA.FR (Christian Huitema)
Newsgroups: comp.protocols.iso
Subject: Re: What is Multilink Protocol?
Message-ID: <8907250831.AA27338@jerry.inria.fr>
Date: 25 Jul 89 08:31:54 GMT
References: <8907211330.AA00452@xuucp.ch.apollo.com>
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A multilink protocol has been used betwen the Transpac nodes from the
beginning. At that time (75), the max speed one could get was 72kbps on
a 48khz "primary group" (analog). The multilink protocol allowed them
to go for higher throughputs by grouping several such links on the
heavily charged arteries, and to obtain better security of operation:
if one link broke, the packets would be resent on the other links of
the group, without loosing the virtual circuits.

Indeed, this kind of protocol is much less useful today, with the
generalisation of digital telephony: the equivalent of an analog
"primary group" is a T1 link, and the network is more reliable.
However, there still are cases where one has only the choice between 64
kbps and full T1, and would like to use 256 kbps only; and have
networks ever been reliable enough?

Christian Huitema
PS.
The multilink procedure referred to in X.25 1984 should not be confused
with a multilink procedure analysed by Guy Pujolle and Otto Spaniol 10
years ago (numerous publications). They had the idea of splitting a
high speed and long delay link into several subchannels in order to
control it more efficiently.