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From: tcp-ip@ucbvax.ARPA
Newsgroups: fa.tcp-ip
Subject: Re: MILNET/ARPANET performance
Message-ID: <7600@ucbvax.ARPA>
Date: Thu, 30-May-85 13:58:29 EDT
Article-I.D.: ucbvax.7600
Posted: Thu May 30 13:58:29 1985
Date-Received: Fri, 31-May-85 04:13:40 EDT
Sender: daemon@ucbvax.ARPA
Organization: University of California at Berkeley
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From: ljs@bbnccv


The 8 message limit in the Arpanet and Milnet is a major problem for
gateways.  Often in our daily statistics I have seen ARPANET (or MILNET)
gateways dropping a high percentage of packets received (20%-30%) at fairly low
throughputs (50-70 packets per second), while other gateways on faster
and non-blocking networks can pass 200 packets per second with
no dropping at all.  A quick look at the daily ARPANET log often shows 
that the ARPANET (or MILNET) IMPs were blocking their interfaces during
this period.

This says that the processing power of the LSI-11 gateway is not the problem,
at least up to 200 packets per second.  Lack of buffers in the LSI-11 is
a problem, however, since short periods of interface blocking could be
smoothed over by a greater buffering capacity.  There is a project underway
to provide more buffers for the LSI-11.  We are developing a new multiprocessor
gateway which will provide even more buffers and processing
power, in addition to a new interior routing algorithm and a better algorithm
to distribute EGP information internally.  This project is being funded by
DARPA, and to my knowledge the DDN PMO has made no commitment to switch.

The new end-to-end algorithm in the IMPs will improve the situation
considerably, since the IMP will no longer block the entire interface
just because one connection is blocked.  

In addition, there are plans to put EGP in all of the mailbridges (after
the memory upgrade).  This should reduce the EGP-related problems that
MILNET sites have been seeing.

Linda Seamonson