[SIPForum-discussion] Query related to Basic SIP call

XIAO Xiaohong Xiaohong.Xiao at alcatel-sbell.com.cn
Thu Jan 14 01:35:06 UTC 2010

The Via header field tells other elements where to send the response, the Contact header field tells other elements where to send
   future requests.
So  180 ringing response is sent back to the address in Via header of Invite.


From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Tomasz Zieleniewski
Sent: 2010年1月14日 5:01
To: gaurav ahuja
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] Query related to Basic SIP call


Contact Header is mandatory in INVITE request too.

Kind regards,
- Tomasz Zieleniewski
ICT Backyard - http://ictbackyard.com

2010/1/13 gaurav ahuja <gaurav.ahuja123 at gmail.com>

	Hi All,
	As per RFC 3261, 
	Via, To, From, C-seq, Call-id, Max-Forwards are the only mandatory headers in an Invite request
	But we still add Contact Header  to know the actual address of UAC
	Suppose, in an Invite request there is no contact header, 
	so when Proxy receives 180 ringing response, how it will forward that response to UAC  who initiated the Invite.
	Thanks in advance

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