RFC 5390: Requirements for Management of Overload in the Session Initiation Protocol

Publisher

IETF / RFC Editor

URL

https://www.rfc-editor.org/rfc/rfc5390.html

Published

2008-12-01

Updated

unknown

Accessed

2026-09-25

HTTP status

200

License

IETF Trust Legal Provisions (BCP 78); no-redistribution; short excerpts and locators only

Source notes citing this source

• RFC 5390 notes that the cases in which a server should send 503 are ambiguous and that implementations send 503 for many reasons, only some of which are actual overload. in context
• In SIP, 503 Service Unavailable means the server is temporarily unable to process the request because of temporary overloading or maintenance of the server. in context
• A SIP client (proxy or UAC) that receives a 503 SHOULD attempt to forward the request to an alternate server. in context
• Because proxies are told not to relay 503 upstream and Teams reports whether a 503 came from Microsoft (540998) or the SBC (560503), the first troubleshooting step for a 503 is to find which hop generated it before blaming the far-end carrier. inferred in context
• RFC 3261 allows proxies to refuse the connection or drop the request instead of responding with 503. in context
• RFC 3261 tells proxies not to forward 503 responses upstream, at SHOULD NOT strength. in context
• After a 503, the client SHOULD NOT forward any other requests to that server for the duration given in the Retry-After header field, if one is present. in context

Cite this source record

APA

WarmTransfer. (2008, December 1). RFC 5390: Requirements for Management of Overload in the Session Initiation Protocol. WarmTransfer. https://warmtransfer.net/knowledge/sources/rfc-5390-sip-overload-requirements

BibTeX

@misc{warmtransfer-rfc-5390-sip-overload-requirements,
  title  = {RFC 5390: Requirements for Management of Overload in the Session Initiation Protocol},
  author = {{WarmTransfer}},
  year   = {2008},
  url    = {https://warmtransfer.net/knowledge/sources/rfc-5390-sip-overload-requirements},
  note   = {IETF / RFC Editor, accessed 2026-09-25}
}