Because MSS clamping rewrites only TCP SYN options, it cannot stop a SIP-over-UDP INVITE larger than the tunnel MTU from being fragmented; it helps SIP only after signalling moves to TCP or TLS.
inferred · Checked 2026-10-02
- Vendor
- not restricted
- Product
- not restricted
- Subsystem
- TCP MSS clamping
- Deployment
- on-premises
- Region
- not restricted
- Release range
- current as of 2026-10-02
- Status
- inferred
- Checked
- 2026-10-02
Sources
- Resolve IPv4 Fragmentation, MTU, MSS, and PMTUD Issues with GRE and IPsec — Cisco Systems · tier 2 current vendor documentation · ip tcp adjust-mss section
Cite this note
APA
WarmTransfer. (2026, October 2). Troubleshooting failed calls caused by large SIP messages over UDP: source note sip-fragmentation-troubleshooting-adjust-mss-no-udp-help. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-fragmentation-troubleshooting-adjust-mss-no-udp-help
BibTeX
@misc{warmtransfer-claim-sip-fragmentation-troubleshooting-adjust-mss-no-udp-help,
title = {Troubleshooting failed calls caused by large SIP messages over UDP: source note sip-fragmentation-troubleshooting-adjust-mss-no-udp-help},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-fragmentation-troubleshooting-adjust-mss-no-udp-help},
note = {Source note sip-fragmentation-troubleshooting-adjust-mss-no-udp-help, checked 2026-10-02}
}