With rport, the server records the request's source port in rport and source IP in received, and sends the UDP response to that address and port from the address and port the request arrived on.
Checked 2026-10-02
- Vendor
- not restricted
- Product
- not restricted
- Subsystem
- SIP NAT traversal
- Deployment
- any
- Region
- not restricted
- Release range
- RFC 3581, current as of 2026-10-02
- Checked
- 2026-10-02
Sources
- RFC 3581: An Extension to the Session Initiation Protocol (SIP) for Symmetric Response Routing — IETF / RFC Editor · tier 1 standards and regulators · Section 4 Server Behavior
Cite this note
APA
WarmTransfer. (2026, October 2). Troubleshooting SIP 408 Request Timeout and calls that get no response: source note sip-408-timeout-troubleshooting-rfc3581-rport-symmetric. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-408-timeout-troubleshooting-rfc3581-rport-symmetric
BibTeX
@misc{warmtransfer-claim-sip-408-timeout-troubleshooting-rfc3581-rport-symmetric,
title = {Troubleshooting SIP 408 Request Timeout and calls that get no response: source note sip-408-timeout-troubleshooting-rfc3581-rport-symmetric},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-408-timeout-troubleshooting-rfc3581-rport-symmetric},
note = {Source note sip-408-timeout-troubleshooting-rfc3581-rport-symmetric, checked 2026-10-02}
}