Re: UDP checksum behaviourin a life of stream

Hi Govinda,

I don't think any assumptions can be made about how the UDP checksum 
is enabled/disabled by the applications.

FYI, one of the test scenarios from ROHC3095 interop testing (years 
ago) involved UDP checksums being enabled/disabled mid-flow, and 
whether compressor implementations would convey this info correctly to 
the decompressors at the other end.

Regards,
vick

On Thu, 15 May 2008, govinda reddy m wrote:

> Dear All,
> We know that if UDP checksum flag is disabled, its value is constantly zero
> and could be ompressed away.
> If enabled, its value depends on the payload, which for compression purposes
> is equivalent to it changing randomly with every packet.
>
> My question is:Will we need to examine UDP checksum for every packet in a
> flow to enable or disable UDP checksum flag?
>                      Why i am asking is, in my implementation while doing
> heuristics process to find "Profile" and some fields "Behaviour", we are
> examining for the first three packets only in the flow,
>                      anf for the third packet we check the non-zero value
> of UDP checksum and enable if if is non-zero, otherwise by default it will
> be disabled.
>                      After that we are never examining the UDP checksum.
>
>                      So my doubt, is it true that for some packets UDP
> checksum will be calculated and inserted by source for a while and insert
> zero for another while in the same flow?
>
> -- 
> Cheers
> Govinda Reddy M
>