According to RFC 3665 section 3.8 and RFC 3261 section 9, there is only one via header in CANCEL message (message F11, F13 at page 72 of RFC 3665). But when I ran the similar scenario(through one proxy), I got two via header in CANCEL message such as following: CANCEL sip:UA12@node11.under.test.com;transport=udp SIP/2.0 Record-Route: <sip:192.0.50.50;lr=on;ftag=11380> Via: SIP/2.0/UDP ss.under.test.com;branch=z9hG4bKd068.25909417.0 Via: SIP/2.0/UDP node.under.test.com:5060;received=192.0.10.10;branch=z9hG4bKPUA4295483 Max-Forwards: 69 From: UA11 <sip:UA11@under.test.com>;tag=11380 To: <sip:UA12@under.test.com> Call-ID: 11380(a)tom.example.com CSeq: 4 CANCEL Content-Length: 0 P-hint: usrloc applied How can I remove the 2nd via header? Thank you Fangyu Ling