A follow-up note in the thread pointed out that STIR/SHAKEN has large SIP messages. This particular issue may solve itself as companies deploy STIR/SHAKEN and talk with their vendors...
> On Oct 2, 2019, at 10:35 AM, Fred Baker <[email protected]> wrote: > > So I'm reading NANOG and finding a certain thread interesting in this > context. Look in the archive (or if you follow it, just look at your archive) > for the subject line "Spectrum (Charter) Fragmented UDP". > >> On Oct 1, 2019, at 4:57 PM, Suresh Krishnan <[email protected]> wrote: >> >> Hi all, >> The text changes in version -16 of this draft for the resolution of Alissa >> Cooper’s DISCUSS position resulted in lively discussion on the mailing list. >> The authors have made another revision of the draft (version -17) to address >> the comments raised during this discussion. If you believe that any of your >> substantive points have not been addressed please respond to this mail >> stating what they are. As the responsible AD, I believe that the draft is >> ready to move forward and be approved, and I would like to do so by end of >> day on October 8th 2019 in the absence of any actionable objections. >> >> Thanks >> Suresh > > The point made this morning is that telephones have horrible TCP > implementations: > >> From: Phil Lavin <[email protected]> >> Subject: RE: Spectrum (Charter) Fragmented UDP >> Date: October 2, 2019 at 8:59:42 AM EDT >> To: Saku Ytti <[email protected]> >> Cc: "[email protected]" <[email protected]> >> >>> While we can say this should just work, the reality is, it's not very >>> reliably true and I would not build product or business on the assumption >>> that it works well. >> >> Yup. Understood. We can't get away from sending multi-packet messages. We >> try our best to keep SIP messages as small as possible though sometimes >> certain optional features required by customers push it beyond their MTU. >> We're also starting to see decreasing MTUs as customers deploy various >> SD-WAN solutions and it's tough to keep up with these when you're already >> teetering on the edge of what used to be considered a fairly common minimum >> MTU value. >> >> We can, of course, get away from using UDP. We can and do run SIP over TCP >> and indeed over TLS on TCP though the stateful nature of TCP often makes >> this undesirable. We see a lot of SIP phone implementations that do not >> handle TCP connection failures very well and result in a loss of calls for a >> period of minutes if this happens, as they take a while to notice the >> connection has dropped and should be re-established. Pros and cons of each. >> >> If anyone has any specific information about Spectrum CPE changes or indeed >> any contacts who may be able to interrogate this internally within Spectrum >> that would be appreciated. > > What we are saying in this draft is that such things ought not to be. Do we > have practical advice in context? "Fix your TCP and use it"? _______________________________________________ Int-area mailing list [email protected] https://www.ietf.org/mailman/listinfo/int-area
