RFC 3581: An Extension to the Session Initiation Protocol (SIP) for Symmetric Response Routing

Publisher

IETF / RFC Editor

URL

https://www.rfc-editor.org/rfc/rfc3581.html

Published

2003-08-01

Updated

unknown

Accessed

2026-09-25

HTTP status

200

License

IETF Trust Legal Provisions (BCP 78); no-redistribution; short excerpts and locators only

Source notes citing this source

• An RFC 3581 client may add an empty 'rport' parameter to the top Via header to signal that it supports symmetric response routing. in context
• When a request carries rport, the server must set rport to the request's source port. It then sends responses to the IP in 'received' and the port in 'rport', so the responses follow the NAT binding the request created. in context

Cite this source record

APA

WarmTransfer. (2003, August 1). RFC 3581: An Extension to the Session Initiation Protocol (SIP) for Symmetric Response Routing. WarmTransfer. https://warmtransfer.net/knowledge/sources/rfc-3581-rport

BibTeX

@misc{warmtransfer-rfc-3581-rport,
  title  = {RFC 3581: An Extension to the Session Initiation Protocol (SIP) for Symmetric Response Routing},
  author = {{WarmTransfer}},
  year   = {2003},
  url    = {https://warmtransfer.net/knowledge/sources/rfc-3581-rport},
  note   = {IETF / RFC Editor, accessed 2026-09-25}
}