Re: Multiplexing algorithms for transport connections

Andy Malis (malis@OAKLAND.BBN.COM)
Mon, 26 Sep 88 13:09:19 -0400


For IP over DDN Standard X.25, the most efficient (in terms of
PSN and network resources) algorithm is to multiplex all
datagrams to the same network-level destination over the same
X.25 VC, requesting the largest packet size (up to 1024 octets)
supported by your host. This is the ONLY algorithm allowed by
the old End-to-End, which is still in use on the MILNET. This
also most closely emulates the network transport of AHIP (1822)
messages, except that the window size is 7 rather than 8.

If you are on a network running the new End-to-End (the ARPANET),
your host is allowed to open more than one Standard connection to
other hosts. You may wish to have your host measure the average
utilization of its host access line, and if it has a combination
of low access line utilization and a long queue of datagrams to a
particular destination host, then open a second VC to that host.
Note that opening multiple VCs to a destination host only wastes
resources in the PSN, network, and presumably the host, if both
of the above conditions do not apply.

The maximum number of VCs that any host may open at any one time
is configured by the network administration, so opening multiple
VCs to one destination may make it harder for your host to open
VCs to other destinations without having to clear previously
open VCs.

Also note that the PSN clears Standard X.25 VCs that have been
idle for a period of time. This period is also configurable by
the network administration.

Andy Malis
BBNCC PSN Development

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