Re: IP Background

[Mabry Tyson <TYSON@warbucks.ai.sri.com>]

IP Background is NOT the culprit.  IP Background is the guy that checks on
connections to keep them active in case a packet was lost going either way.
That is, if you have a TCP connection between host A and host B, they usually
keep in synch by sending ACK packets for packets received.  If one of those
ACK packets gets lost, the host who should have received the ACK packet will
continue to wait for it.  IP Background will wake up once a minute and
send check for connections that might be out of synch.  If so, it will send
a packet out asking for a new ACK (or something like that).  (Don't take what
I said about the way the connections work as gospel -- I'm not an expert.)

Namespace service is usually done over CHAOS, not IP.

Do you have *lots* of IP Background entries in the Timer Queue?  If you
do, that is your problem.  I believe you should only have one.  I did
have a situation a couple of times on our secondary name server/mailer
host that we started having SMTP connection problems and wound up with
>50 IP Background Timer Queue entries.  That completely degraded the
machine.  Most of the SMTP processes were in LMFS Lock state.  GC was
always inhibited (I think this was 7.0, but I'm not sure) so it wasn't
long before the machine crashed with no swap space.  That has happened
twice (but not recently) and I never really figured out the cause except
that maybe the machine accepted more SMTP connections than it could handle
and went into a tail spin.