Source note · Expressway business-to-business calling
RFC 3263 specifies that when no SRV records exist, the client does an A or AAAA lookup of the domain and uses the transport's default port (5060, or 5061 for TLS).
Checked 2026-09-25
- Vendor
- IETF
- Product
- SIP
- Subsystem
- server location
- Deployment
- on-premises, multi-tenant
- Region
- not restricted
- Release range
- RFC 3263
- Checked
- 2026-09-25
Sources
- RFC 3263: Session Initiation Protocol (SIP): Locating SIP Servers — IETF / RFC Editor · tier 1 standards and regulators · Section 4.2 Determining Port and IP Address
Cite this note
APA
WarmTransfer. (2026, September 25). Expressway business-to-business calling: source note expressway-b2b-calling-rfc3263-a-fallback. WarmTransfer. https://warmtransfer.net/knowledge/claims/expressway-b2b-calling-rfc3263-a-fallback
BibTeX
@misc{warmtransfer-claim-expressway-b2b-calling-rfc3263-a-fallback,
title = {Expressway business-to-business calling: source note expressway-b2b-calling-rfc3263-a-fallback},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/expressway-b2b-calling-rfc3263-a-fallback},
note = {Source note expressway-b2b-calling-rfc3263-a-fallback, checked 2026-09-25}
}