SIP Header Fields

IANA Approved Header Fields

The following header fields are officially approved by IANA and thus listed in sip-parameters. The list is complete as of 2007-06-15.

• Accept

• Accept-Contact (short: a)

• Accept-Encoding

• Accept-Language

• Accept-Resource-Priority

• Alert-Info

• Allow

• Allow-Events (short: u)

• Authentication-Info

• Authorization

• Call-ID (short: i)

• Call-Info

• Contact (short: m)

• Content-Disposition

• Content-Encoding (short: e)

• Content-Language

• Content-Length (short: l)

• Content-Type (short: c)

• CSeq

• Date

• Encryption (deprecated)

• Error-Info

• Event (short: o)

• Expires

• From (short: f)

• Hide (deprecated)

• History-Info

• Identity (short: y)

• Identity-Info (short: n)

• In-Reply-To

• Join

• Max-Forwards

• MIME-Version

• Min-Expires

• Min-SE

• Organization

• P-Access-Network-Info

• P-Answer-State

• P-Asserted-Identity

• P-Associated-URI

• P-Called-Party-ID

• P-Charging-Function-Addresses

• P-Charging-Vector

• P-DCS-Trace-Party-ID

• P-DCS-OSPS

• P-DCS-Billing-Info

• P-DCS-LAES

• P-DCS-Redirect

• P-Media-Authorization

• P-Preferred-Identity

• P-User-Database

• P-Visited-Network-ID

• Path

• Priority

• Privacy

• Proxy-Authenticate

• Proxy-Authorization

• Proxy-Require

• RAck

• Reason

• Record-Route

• Refer-Sub

• Refer-To (short: r)

• Referred-By (short: b)

• Reject-Contact (short: j)

• Replaces

• Reply-To

• Request-Disposition (short: d)

• Require

• Resource-Priority

• Response-Key (deprecated)

• Retry-After

• Route

• RSeq

• Security-Client

• Security-Server

• Security-Verify

• Server

• Service-Route

• Session-Expires (short: x)

• SIP-ETag

• SIP-If-Match

• Subject (short: s)

• Subscription-State

• Supported (short: k)

• Target-Dialog

• Timestamp

• To (short: t)

• Unsupported

• User-Agent

• Via (short: v)

• Warning

• WWW-Authenticate

RFC 3261 contains two tables showing a summary of the usage of the various header fields. These tables are extended by various other RFCs that introduce new header fields, methods, and status codes. The page Table 2 contains a compilation of all of these.

Inofficial Header Fields

Some header fields that were proposed one way or another didn't make it into RFCs and thus are not official. Here are some that may be encountered in the wild

• Remote-Party-ID

• P-RTP-Stats