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rfc-6432

Carrying Q.850 Codes in Reason Header Fields in SIP (Session Initiation Protocol) Responses

R. Jesske, L. Liess
date2011-11 streamIETF wgnon working group statusPROPOSED STANDARD pages4 canonicalhttps://www.rfc-editor.org/rfc/rfc6432 doi10.17487/RFC6432
Although the use of the SIP (Session Initiation Protocol) Reason header field in responses is considered in general in RFC 3326, its use is not specified for any particular response code. Nonetheless, existing deployments have been using Reason header fields to carry failure-related Q.850 cause codes in SIP responses to INVITE requests that have been gatewayed to Public Switched Telephone Network (PSTN) systems. This document normatively describes the use of the Reason header field in carrying Q.850 cause codes in SIP responses. [STANDARDS-TRACK]

Extracted elements (5)

design-rationale §3

The Reason header field is not needed in 100 (Trying) responses because they are transmitted hop by hop, not end to end. This exclusion explains why only the 100 response is carved out from the general allowance.

sip, voip

interoperability-note §3

SIP responses with Reason header fields carrying values other than Q.850 cause codes are outside the scope of this document. This specification only normatively addresses Q.850 cause codes in the Reason header field.

sip, voip

normative-requirement §3 MAY

Any SIP response message, with the exception of a 100 (Trying), MAY contain a Reason header field with a Q.850 cause code.

sip, voip

protocol-element §1

The Reason header field, originally defined in RFC 3326, is extended by this document to be usable in SIP responses carrying Q.850 PSTN cause codes from INVITE requests gatewayed to PSTN systems.

sip, voip

security-consideration §4 RECOMMENDED

A wrong Q.850 cause code in the Reason header field could cause unintended behavior, such as an announcement system playing incorrect information. It is RECOMMENDED that the Reason header field be protected by a suitable integrity mechanism such as TLS or IPsec.

sip, security, voip, tls, ipsec