SIP CSeq

INVITE sip:bob@biloxi.com SIP/2.0
Via: SIP/2.0/UDP pc33.atlanta.com:5060;branch=z9hG4bK776asdhds
To: Bob <sip:bob@biloxi.com>
From: Alice <sip:alice@atlanta.com>;tag=1928301774
Call-ID: a84b4c76e66710
CSeq: 314159 INVITE
Contact: <sip:alice@pc33.atlanta.com>
Content-Type: application/sdp
Content-Length: 142
(Alice’s SDP not shown)

Command Sequence (CSeq) Number

Initialized at start of call (1 in this example)
Incremented for each subsequent request
Used to distinguish a retransmission from a new request

Followed by the request type (i.e., SIP method)

Transcript

[slide133] The command sequence number.