The Kamailio sl module adds a signature to the to-tag of local stateless replies to INVITE so that the matching ACKs can be filtered instead of forwarded downstream, and after a timeout all ACKs are let through.

Checked 2026-09-24

Vendor
Kamailio project
Product
Kamailio
Subsystem
sl
Deployment
self-hosted
Region
not restricted
Release range
6.1.x
Checked
2026-09-24

Sources

Cite this note

APA

WarmTransfer. (2026, September 24). Kamailio and OpenSIPS SIP proxies: source note kamailio-sip-proxy-sl-ack-filtering. WarmTransfer. https://warmtransfer.net/knowledge/claims/kamailio-sip-proxy-sl-ack-filtering

BibTeX

@misc{warmtransfer-claim-kamailio-sip-proxy-sl-ack-filtering,
  title  = {Kamailio and OpenSIPS SIP proxies: source note kamailio-sip-proxy-sl-ack-filtering},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/claims/kamailio-sip-proxy-sl-ack-filtering},
  note   = {Source note kamailio-sip-proxy-sl-ack-filtering, checked 2026-09-24}
}

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