Fred, advocating removing the interior protocol checksum across header and payload (and reconstituting/recomputing it afterwards) violates end-to-endidness and weakens the reliability guarantee. Bad idea. From a checksum perspective, you'd do better saying 'use UDP lite with a minimal check just across its own headers and pseudo-header' to decrease the computational overhead - that should be a fixed value.
Using a UDP (or lite) port to indicate what is being done here with a particular weird encap, as well as the original ports on the interior packet, is something that this approach is stuck with, I think. Lloyd Wood http://sat-net.com/L.Wood ________________________________________ From: Fred Baker [[email protected]] Sent: 27 April 2010 10:55 To: Lars Eggert Cc: [email protected]; [email protected]; [email protected]; tsvwg list; Wood L Dr (Electronic Eng); Michael Welzl Subject: Re: UDP encaps for SCTP and SCCP >From my perspective, I would prefer to run a native encapsulation rather than >host it in UDP. If one wants a UDP encapsulation, I have no opinion on which >of the choices to make, but I would suggest a characteristic you want to have. >There is no point having UDP ports *and* SCTP/DCCP ports, and no point in >having a UDP checksum *and* an SCTP checksum. I would recommend removing the >duplicated functions from the interior protocol and relying on UDP's >counterpart, even if it is inferior, as it will be more readily deployed. On Apr 27, 2010, at 10:42 AM, Michael Welzl wrote: > Hi, > > Okay, I herewith speak up: yes I want to see UDP encapsulation for both these > protocols > (but right now I'm not sure which one). > > Both SCTP and DCCP are useful - if there was no consensus on that, ever, these > groups would never have been formed, and the protocols would never have > been developed. > > Now, they are not used much (on the Internet involving NATs); at least > DCCP isn't. That's a problem. UDP encapsulation is a way to try to > solve this problem - and saying that we shouldn't do this because the > protocols aren't used is a bit stupid, isn't it? > > To repeat this more clearly and bluntly: > > tool X isn't working well => noone uses it. > So let's not fix tool X because noone uses it anyway. > Hmmm... > > Cheers, > Michael > > > On Apr 27, 2010, at 9:47 AM, Lars Eggert wrote: > >> Hi, >> >> please keep this discussion focused on which approach we should follow for >> UDP-encapsulating DCCP and SCTP. >> >> I'm happy Lloyd posted his views. I'm hoping other community members will >> speak up as well. If I were asked to characterize current consensus, I'd >> probably say "disinterest for either approach." (Which would be fine, but >> doesn't quite match the earlier feeling I got from the community, i.e., that >> we do want UDP encaps for these protocols.) >> >> Lars > http://www.ipinc.net/IPv4.GIF
