🚀 go-pugleaf

We have both Suns and a microVAX which are not as yet on the same Ethernet
network. I have cross posted the article below in the hope of gaining useful
information.

					Bernard Wilson

In article <17590@megaron.cs.arizona.edu>, leonard@cs.arizona.edu (Aaron Leonard) writes:
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I have no wish to start a holy war here.

BUT it is my simple observation that Suns are poor neighbors to have
on an Ethernet.  (Another way of putting this might be: VAXclusters
are too delicate to coexist happily with lusty, rambunctious Suns.)

I have never seen proof of the oft-repeated rumor that Suns "cheat" on
the 9.6 ms Ethernet retransmit time.  I do know, however, that if you
are running a Local Area VAXcluster that shares a large, variegated
Ethernet with Suns, you should be wary of the following aspects of
reality:

1. A few Suns running NFS can swamp the Ethernet very quickly.  I don't
want to get into the technical details here, but due to some rather
fast-and-loose design decisions in NFS, you will find that colliding
NFS traffic will produce a degenerate situation in a hurry.

2. Sloppy TCP/IP code residing on Suns can cause frequent network 
meltdowns.  Specifically, Suns are notorious for behaving poorly when
confronted by IP broadcast addresses different from what they expect.
More precisely, just a handful of Suns which use the 0's broadcast
and which run RIP (which alas seems to be the default), will generate
feedback loops quite capable of destroying the network, when confronted
by address queries for the 1's broadcast.  (Note: Suns are not the only
machines which exhibit this problem, merely the most virulent.)

On my campus, we have experienced frequent network meltdowns, typically
associated with Suns and their allies caught in a feedback loop of some
sort.  Such events were frequently highlighted by members of Local Area
VAXclusters undergoing "voluntary" CLUEXIT bugchecks when they found that
they couldn't maintain SCS contact with eachother. 

We have lessened the frequency and severity of these tragic occasions via
the following techniques:

1. Put Suns behind IP routers whenever possible.  In other words, get them
OFF of the same Ethernet from your VAXen (and from each other.)

2. Increase the RECNXINTERVAL SYSGEN param on your NI VAXcluster nodes
to something like 120 seconds.   This makes them better able to weather
broadcast storms without committing hara kiri.

I do not intend to raise the issue of the morality of the Suns' behavior,
but only to stress the need for proper prophylaxis when your "share
needles with them" as it were. 

Aaron
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