Re: "... and statistics" (Re: [Phil Dykstra: more interesting numbers] )

Mike Muuss (mike@BRL.ARPA)
Thu, 14 Apr 88 20:40:31 EDT

The BRL Gateway mentioned in Phil's message is a DEC PDP-11/70 running
the BRL-GATEWAY software under the LOS operating system. It has
3 InterLan Ethernet interfaces, one ProNet-10 ring interface, one
ProNet-80 ring interface, and two ACC LH/DH-11 1822 interfaces, one
running to MILNET IMP 29 via a 480,000 bps ECU link, and the other
directly to BRLNET IMP #1. This is BRL-GATEWAY #1; gateway #2 is
similar, with a substitution of a Hyperchannel for the ProNet-80,
and only 1 Ethernet. The remaining 6-7 gateways on our campus are
much simpler (typically a ProNet-10, an LH/DH, and an ethernet), and
are built on smaller processors (11/24, 11/34, 11/44).

The rates mentioned were average rates, intended merely to give folks
some impression of the levels of inter-building traffic on our campus.
We have measured 200 packets/sec as the maximum switching rate of our
gateways, when link-limiting is not a factor (ie, using Ethernet or
ProNet on both sides of the gateway when testing). This is a round-trip
measure, ie, each packet traverses an interface in the gateway 4 times
(we use FLOODPING for this statistic). Many would prefer to claim this
as a peak rate of 400 packets/sec (2 interface traversals per "packet",
counting the ping responses as a second packet) -- we would say "400
monodes/sec" in this case.

This is not an attempt to put down the work of others, merely to report
on behavior of older gateways at BRL. Clearly, the new commercial gateways
have performance several times higher than this, and clearly, it is not
a sensible idea to consider the purchase of PDP-11/70 systems for use
as gateways. However, it makes a nice retirement job for our old friends,
the 11/70s.

Also, note that our campus is "traffic rich", with two Cray computers
(a Cray X-M/P48 and a Cray-2) that talk TCP/IP, and with 6 Alliant FX/8
super-minis, along with over 100 other machines, many of which exchange
high resolution 24-bit-deep color graphics images over the network on a
regular basis.


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