Example SIP messages
The following example SIP INVITE request message was sent by PhoneA to PhoneB. The first nine lines are the SIP headers. The SDP profile starts with v=0 and the media part of the session profile is the last line, starting with m=.
INVITE sip:PhoneB@172.20.120.30 SIP/2.0
Via: SIP/2.0/UDP 10.31.101.50:5060
From: PhoneA <sip:PhoneA@10.31.101.20>
To: PhoneB <sip:PhoneB@172.20.120.30>
Call-ID: 314159@10.31.101.20
CSeq: 1 INVITE
Contact: sip:PhoneA@10.31.101.20
Content-Type: application/sdp
Content-Length: 124
v=0
o=PhoneA 5462346 332134 IN IP4 10.31.101.20
s=Let's Talk
t=0 0
c=IN IP4 10.31.101.20
m=audio 49170 RTP 0 3
The following example shows a possible 200 OK SIP response message in response to the previous INVITE request message. The response includes 200 OK which indicates success, followed by an echo of the original SIP INVITE request followed by PhoneB’s SDP profile.
SIP/2.0 200 OK
Via: SIP/2.0/UDP 10.31.101.50:5060
From: PhoneA <sip:PhoneA@10.31.101.20>
To: PhoneB <sip:PhoneB@172.20.120.30>
Call-ID: 314159@10.31.101.20
CSeq: 1 INVITE
Contact: sip:PhoneB@10.31.101.30
Content-Type: application/sdp
Content-Length: 107
v=0
o=PhoneB 124333 67895 IN IP4 172.20.120.30
s=Hello!
t=0 0
c=IN IP4 172.20.120.30
m=audio 3456 RTP 0
SIP can support multiple media streams for a single SIP session. Each media steam will have its own c= and m= lines in the body of the message. For example, the following message includes three media streams:
INVITE sip:PhoneB@172.20.120.30 SIP/2.0
Via: SIP/2.0/UDP 10.31.101.20:5060
From: PhoneA <sip:PhoneA@10.31.101.20>
To: PhoneB <sip:PhoneB@172.20.120.30>
Call-ID: 314159@10.31.101.20
CSeq: 1 INVITE
Contact: sip:PhoneA@10.31.101.20
Content-Type: application/sdp
Content-Length: 124
v=0
o=PhoneA 5462346 332134 IN IP4 10.31.101.20
s=Let's Talk
t=0 0
c=IN IP4 10.31.101.20
m=audio 49170 RTP 0 3
c=IN IP4 10.31.101.20
m=audio 49172 RTP 0 3
c=IN IP4 10.31.101.20
m=audio 49174 RTP 0 3