Re: [TICTOC] UDP checksum

On Jan 21, 2011, at 3:27 PM, Stewart Bryant wrote:

> Presumably this is a v6 discussion. I can't see any point in using the c/s in v4.
> 
> WRT v6 there is a movement to make this optional (the debate is happening in 6lowlan, and I think that we should be pushing to turn it off for PTP.
> 
> The worst that can happen is that we receive a corrupt pkt and either junk it, or put it in the timing servo whereupon it gets rejected as an outlier.
> 

I think you are referring to this 

which is (will be shortly) in 6man

http://tools.ietf.org/html/draft-eubanks-chimento-6man-01

This is for the case where there is an "inner" packet with a header and checksum, so that the "outer" packet doesn't need protection.

Regards
Marshall

> - Stewart
> 
> 
> 
> On 20/01/2011 23:52, Shahram Davari wrote:
>> Hi Manav,
>> 
>> The minimum requirement is to do UDP checksum incremental update on transmission. If full update is done then UDP checksum must be verified on reception as well.
>> 
>> Thx
>> Shahram
>> 
>> -----Original Message-----
>> From: Bhatia, Manav (Manav) [mailto:manav.bhatia@alcatel-lucent.com]
>> Sent: Thursday, January 20, 2011 3:33 PM
>> To: Shahram Davari; tictoc@ietf.org
>> Subject: RE: UDP checksum
>> 
>> Hi Shahram,
>> 
>> It may be ok as long as the HWs are incrementally recalculating it. However, if its being done afresh then we have an issue. I don't see how the HW behavior can be mandated in a spec.
>> 
>> Cheers, Manav
>> 
>>> -----Original Message-----
>>> From: Shahram Davari [mailto:davari@broadcom.com]
>>> Sent: Friday, January 21, 2011 4.59 AM
>>> To: Bhatia, Manav (Manav); tictoc@ietf.org
>>> Subject: RE: UDP checksum
>>> 
>>> Hi Manav,
>>> 
>>> UDP checksum is usually not verified before updating the CF.
>>> After CF update it is incrementally recalculated. The end
>>> host will then verify the checksum for correctness.
>>> 
>>> Regards,
>>> Shahram
>>> 
>>> -----Original Message-----
>>> From: tictoc-bounces@ietf.org
>>> [mailto:tictoc-bounces@ietf.org] On Behalf Of Bhatia, Manav (Manav)
>>> Sent: Thursday, January 20, 2011 3:16 PM
>>> To: tictoc@ietf.org
>>> Subject: [TICTOC] UDP checksum
>>> 
>>> Hi,
>>> 
>>> Are the LSRs acting as TCs expected to verify the checksum
>>> before they update the correction field? If no, then there is
>>> no point in these LSRs in updating the UDP checksum as they
>>> will "correct" the checksum when its recomputed after
>>> modifying the CF field. In this case wouldn't it make more
>>> sense to just update the checksum at the MPLS terminating point?
>>> 
>>> I also think that updating the UDP checksum may be redundant
>>> as the LSRs are anyways verifying the outer ethernet checksum
>>> before accepting any packets. Any thoughts here?
>>> 
>>> Cheers, Manav
>>> 
>>> --
>>> Manav Bhatia,
>>> IP Division, Alcatel-Lucent,
>>> Bangalore - India
>>> 
>>> 
>>> _______________________________________________
>>> TICTOC mailing list
>>> TICTOC@ietf.org
>>> https://www.ietf.org/mailman/listinfo/tictoc
>>> 
>>> 
>>> 
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> 
> 
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