Re: Network problems.

On Mon 20 Jan, 1997, Piete Brooks <Piete.Brooks@???> wrote:
>> However, I don't really have a clue as to what a sensible setting
>> for a small system should be. The 5 was copied from smail.
>
>My understanding is that even on a busy system, a setting of 1 (or is that 0)
>should be sufficient if all is going well.
>SYS_RECV's tend to imply that there is a network problem, or you are under
>attack !

(that's SYN_RCVD)

A busy system can require a large number, as it must have a large
enough backlog queue for the number of SYN+ACKs that are in transit
from the server back to the client, along with space for incoming
SYN requests from new clients attempting connections. (You can of
course work out the optimal number, from the number of connections
per second and the typical rtts to clients.)

right now I note that our own mail machines aren't that busy,
but this is probably because the USA hasn't yet woken up. It only
takes a small loss of routing somewhere in the USA for a big
problem to appear, though.

>I suspect upping the dafault does little harm (may not do much good,
>as it is just a request to the O/S, and many (older) kernels have "5"
>compiled in).

there are patches to increase this for SunOS 4. I recommend people
with busy servers do this (especially useful for web servers, but
also rather handy for busy mail systems).

[Solaris 2 users can use the ndd tunables to increase the default
beyond 32 if they need to; Irix 6 users won't need to do anything.]

-- jrg.