[ih] UDP Length Field?

[Joseph Touch]

> On Nov 28, 2020, at 9:44 PM, Wayne Hathaway via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> I worked for a few years for Auspex Systems, which made network-attached storage systems using NFS, which uses UDP.  I don't know the reasoning behind including a length field, but note that the NFS header within the UDP datagram is variable length.  I noticed that by using the UDP length field, I could do a significant optimization when reading incoming datagrams.
> 
> For example, if the UDP length was 8284 bytes, it was a very good guess that the arriving packet had an NFS header of 92 bytes and a data field of 8192 bytes. 

The same information would have been available in the IP header, e.g., if IHL=5 (typically), then if IPlength were 8304, you’d have the same hint.

Esp. given that UDP packets where (UDPlen != (IPlen - 4*IHL)) are more recent (Teredo extensions starting 2008, UDP options starting 2015) than when Auspex went defunct (2003).

Joe