Kevin Newman wrote:
>I saw this once upon a time on a classic machine.  We also determined that
>the
>problem was due to the traffic on the subnet where the HP was.  We ended up
>putting a "filtering" router in front of the HP so that only requests for
>the HP
>got to the box.  It worked very well!

One problem that we dealt with recently concerned the HP 3000 network
code's handling of undeliverable packets.

We have an application that uses NetIPC's "deferred connection" mode, in
which a server with a listening socket has the option of accepting or
rejecting the connection before it is actually established. We use this
for IP filtering, so that a server connection request from an
unauthorized network can be refused.

It appears that this can cause problems if the HP 3000 has no route to
the connecting client's destination AND the application uses nowait I/O
on the connection socket. The expected action in this case is for the
network code to return a "destination unreachable" error to the server
program. However, what actually happens is that the new "bad" connection
simply hangs, as does the listening socket. Further connection requests
on the listening socket are ignored. The only way out is to abort and
restart the server. Unfortunately, this sometimes appears to cause a
system crash when the network code tries to tear down the half-open
connection.

I did not investigate the effects of using blocking I/O.

The workaround here was to put in a default route. The default route
points to a router with a functioning bit-bucket, where the undeliverable
packet is disposed of without causing any damage. This may explain why a
packet filter improved the reliability of the 3000.

-- Bruce


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