Re: [sipcore] Open issues in draft-ietf-sipcore-sip-websocket-09

[Iñaki Baz Castillo <[e-mail]>]

2013/6/19 Avasarala, Ranjit (NSN - IN/Bangalore) <[e-mail]>:
> Hi Inaki
>
> Usually contact header contains the address on which the callee can reach caller. But when a SIP message is sent in websocket, what is the use of putting contact header?


As said in my previous mail, that is just in case the client is a SIP
WebSocket Client but not a SIP WebSocket Server. Anyhow, the Contact
header MUST be added anyway as it can contain parameters other than
just the UA's address and transport. And it must be added in an INVITE
so the remote peer can create the "dialog target" and use its URI
value as Request-URI for in-dialog requests.

Those are SIP rules, they must be respected.


> Should Contact header contain browser's address, since SIP UA is anyway part of browser and the callee cannot anyway reach SIP UA directly.

Please take a look to the appendix B.1 of the draft:



B.1.  SIP WebSocket Client Considerations

   The JavaScript stack in web browsers does not have the ability to
   discover the local transport address used for originating WebSocket
   connections.  A SIP WebSocket client running in such an environment
   can construct a domain name consisting of a random token followed by
   the ".invalid" top-level domain name, as stated in [RFC2606], and
   uses it within its Via and Contact headers.

      The Contact URI provided by SIP UAs requesting (and receiving)
      Outbound support is not used for routing requests to those UAs,
      thus it is safe to set a random domain in the Contact URI
      hostport.


Clear? :)

--
Iñaki Baz Castillo
<[e-mail]>