[SIP Beyond VoIP] Sylk does not use maddr in the 200 OK that is reply to NOTIFY request

Iñaki Baz Castillo ibc at aliax.net
Wed Jan 30 23:48:17 CET 2013

2013/1/30 Record Route <recordroute at gmail.com>:
> Sylk seems to be not using the maddr ip in the Contact header of 200OK, Then
> this results in, further NOTIFY messages are sent by Sylk to clients
> directly, not to my sip proxy.
> I guess, a fix needs to be applied, what should I do?

Your SIP proxy should add a Record-Route to *every* NOTIFY request as
the RFC 3265 states:


3.2.3. Proxy NOTIFY Behavior

   Proxies need no additional behavior beyond that described in SIP [1]
   to support NOTIFY.  If a proxy wishes to see all of the SUBSCRIBE and
   NOTIFY requests for a given dialog, it MUST record-route the initial
   SUBSCRIBE and any dialog-establishing NOTIFY requests.  Such proxies
   SHOULD also record-route all other SUBSCRIBE and NOTIFY requests.

Using "maddr" is discouraged by RFC 3261 (which is 11 years old !!!):

     The maddr field has been used as a simple form of loose source
     routing.  It allows a URI to specify a proxy that must be
     traversed en-route to the destination.  Continuing to use the
     maddr parameter this way is strongly discouraged (the
     mechanisms that enable it are deprecated).  Implementations
     should instead use the Route mechanism described in this
     document, establishing a pre-existing route set if necessary
     (see Section  This provides a full URI to describe
     the node to be traversed.

Iñaki Baz Castillo
<ibc at aliax.net>

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