Alex, From my experience a lot of proxies add generic parameters to Via headers, so this is likely an implementation issue on the UAS side.
For instance here is the VIA header with custom parameters from Skype For Business SIP INVITE: Via: SIP/2.0/TLS 192.168.245.34:50087;received= 38.98.149.84;branch=z9hG4bKFBE678A7.146D3C0CCAD739BF;*branche* *d=FALSE;ms-internal-info="dakSf00jMdrBoMlJQoTVSCsnH8DGdU* *c7iwCgVW-geOnqEMPG0UiGq7HgAA"*;rport=50087 Regards, _____________ Roman Shpount On Fri, Sep 30, 2016 at 12:39 PM, Alex Balashov <abalas...@evaristesys.com> wrote: > Hi, > > I have a proxy implementation that adds a custom parameter to Via that is > not within the commonly seen subset of "maddr", "ttl", "received", or > "branch". It adds a parameter called "i", whose value is alphanumeric > (think hex nibbles). > > I can't find any prose in RFC 3261 to explicitly support the idea that > arbitrary parameters are acceptable, but the ABNF appears to allow for it: > > Via = ( "Via" / "v" ) HCOLON via-parm *(COMMA via-parm) > via-parm = sent-protocol LWS sent-by *( SEMI via-params ) > via-params = via-ttl / via-maddr > / via-received / via-branch > / via-extension > via-ttl = "ttl" EQUAL ttl > via-maddr = "maddr" EQUAL host > via-received = "received" EQUAL (IPv4address / IPv6address) > via-branch = "branch" EQUAL token > via-extension = generic-param > > generic-param = token [ EQUAL gen-value ] > gen-value = token / host / quoted-string > > Moreover, RFC 3261 § 20.42 does say: > > A Via header field value can also contain parameters such > as "maddr", "ttl", "received", and "branch", whose meaning > and use are described in other sections. > > In my reading of this, the turn of phrase "such as" is chosen very > deliberately. But I could be wrong. > > So, the question is, would something like 'i=d3adb33f' be acceptable for a > proxy to stamp on its own Via header? It sounds like it should be. Yet, I'm > dealing with a UAS that doesn't like it—more specifically, it fails to > parse the Via if it contains an alphanumeric value, although it copes fine > with a strictly numeric one. The result is that responses from the UAS > don't contain the proxy's Via header, leading it to barf on processing them. > > Thanks! > > -- Alex > > -- > Alex Balashov | Principal | Evariste Systems LLC > > Tel: +1-706-510-6800 (direct) / +1-800-250-5920 (toll-free) > Web: http://www.evaristesys.com/, http://www.csrpswitch.com/ > _______________________________________________ > Sip-implementors mailing list > Sip-implementors@lists.cs.columbia.edu > https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
