In Asterisk res_pjsip the [system] option disable_tcp_switch defaults to yes, so Asterisk does not automatically switch large outgoing requests from UDP to TCP unless configured to.
Checked 2026-10-02
- Vendor
- Sangoma
- Product
- Asterisk
- Subsystem
- res_pjsip
- Deployment
- on-premises
- Region
- not restricted
- Release range
- master branch as of 2026-10-02
- Checked
- 2026-10-02
Sources
- configs/samples/pjsip.conf.sample (asterisk/asterisk, master branch) — Sangoma / Asterisk project · tier 3 vendor-maintained repositories · [system] section, disable_tcp_switch comment block
Cite this note
APA
WarmTransfer. (2026, October 2). Troubleshooting failed calls caused by large SIP messages over UDP: source note sip-fragmentation-troubleshooting-asterisk-no-tcp-switch-dflt. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-fragmentation-troubleshooting-asterisk-no-tcp-switch-dflt
BibTeX
@misc{warmtransfer-claim-sip-fragmentation-troubleshooting-asterisk-no-tcp-switch-dflt,
title = {Troubleshooting failed calls caused by large SIP messages over UDP: source note sip-fragmentation-troubleshooting-asterisk-no-tcp-switch-dflt},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-fragmentation-troubleshooting-asterisk-no-tcp-switch-dflt},
note = {Source note sip-fragmentation-troubleshooting-asterisk-no-tcp-switch-dflt, checked 2026-10-02}
}