Subject: Re: ip reassembly time exceeded?
To: None <current-users@NetBSD.ORG>
From: Christoph Badura <>
List: current-users
Date: 01/28/1997 03:11:00
dennis@jnx.COM (Dennis Ferguson) writes:
>Here's the top 10 IP packet sizes as measured from a backbone router

>Size (bytes)  Probability (%)
>    40           44.8
>   552            9.2

>I'd conclude two things:

>(2) 296 is so frequently occurring that I wouldn't want to bet the problem
>    is entirely the fault of the Microsoft software, as one would assume
>    they would have had plenty of opportunity to notice by now and fix it
>    (I'm pretty sure the 552 in second place is microsoft's preferred number,
>    so there may be a lot of those machines out there).

The 552 being in second place has most likely nothing to do with
microsoft.  Some BSDish TCP/IP stack default to a 512 byte maximum
segment size for non-local traffic.  To qoute from /sys/netinet/tcp.h:

 * Default maximum segment size for TCP.
 * With an IP MSS of 576, this is 536,
 * but 512 is probably more convenient.
 * This should be defined as MIN(512, IP_MSS - sizeof (struct tcpiphdr)).
#define TCP_MSS 512

Interestingly enough, this used to be 536 bytes in 4.3BSD.
Christoph Badura

You don't need to quote my .signature.  Everyone has seen it by now.
Besides, it doesn't add anything to the current thread.