Michel, The standard only allows the TCs to reset the checksum to 0 when transporting PTP over UDP/IPv4.
My original question was wrt IPv6 - I find correcting the checksum onerous when devices are adding the residence time in the correctionField in HW and I think we should do away with this because if a fresh checksum is being computed then it defeats the whole purpose of having a checksum in the first place. Assume an LSR receives a corrupted MPLS packet. We now change the CF and will end up updating the checksum based on the contents of the corrupted packet. Cheers, Manav > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of michel ouellette > Sent: Saturday, January 22, 2011 3.04 AM > To: [email protected] > Subject: Re: [TICTOC] UDP checksum > > > > PTP GM and OC are allowed to set the UDP checksum to 0 > (according to the standard - UDP/IPv4 encap). In such case no > action on the updating the UDP checksum would be required by > the TCs. The TC itself can also set the UDP checksum to 0 > (according to the standard any intermediate node can do so). > > This would also apply to the case where you have TCs > interconnected by two BCs. > > > > - Michel > > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Stewart Bryant > Sent: January 21, 2011 03:27 PM > To: [email protected] > Subject: Re: [TICTOC] UDP checksum > > 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. > > - 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:[email protected]] > > Sent: Thursday, January 20, 2011 3:33 PM > > To: Shahram Davari; [email protected] > > 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:[email protected]] > >> Sent: Friday, January 21, 2011 4.59 AM > >> To: Bhatia, Manav (Manav); [email protected] > >> 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: [email protected] > >> [mailto:[email protected]] On Behalf Of Bhatia, Manav (Manav) > >> Sent: Thursday, January 20, 2011 3:16 PM > >> To: [email protected] > >> 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 > >> [email protected] > >> https://www.ietf.org/mailman/listinfo/tictoc > >> > >> > >> > > _______________________________________________ > > TICTOC mailing list > > [email protected] > > https://www.ietf.org/mailman/listinfo/tictoc > > > > > -- > For corporate legal information go to: > > http://www.cisco.com/web/about/doing_business/legal/cri/index.html > > > _______________________________________________ > TICTOC mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/tictoc > _______________________________________________ > TICTOC mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/tictoc > _______________________________________________ TICTOC mailing list [email protected] https://www.ietf.org/mailman/listinfo/tictoc
