Source note · Calls that drop after about 30 seconds

Microsoft recommends using only the Contact header, not Record-Route, when no proxy SBC is in use. Record-Route is needed when a proxy SBC with Local Media Optimization must stay in the path, and if both headers are used their values must be identical.

Checked 2026-09-25

Vendor: Microsoft
Product: Teams Phone Direct Routing
Subsystem: SBC configuration
Deployment: multi-tenant
Region: not restricted
Release range: current as of 2026-09-25
Checked: 2026-09-25

Sources

Teams Phone System Direct Routing: SIP protocol — Microsoft · tier 2 current vendor documentation · Section 'Contact and Record-Route headers considerations'

Cite this note

APA

WarmTransfer. (2026, September 25). Calls that drop after about 30 seconds: source note sip-calls-drop-30-seconds-msdr-contact-only. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-calls-drop-30-seconds-msdr-contact-only

BibTeX

@misc{warmtransfer-claim-sip-calls-drop-30-seconds-msdr-contact-only,
  title  = {Calls that drop after about 30 seconds: source note sip-calls-drop-30-seconds-msdr-contact-only},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/claims/sip-calls-drop-30-seconds-msdr-contact-only},
  note   = {Source note sip-calls-drop-30-seconds-msdr-contact-only, checked 2026-09-25}
}

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