RFC 3611, "RTP Control Protocol Extended Reports (RTCP XR)", November 2003

Errata ID: 3795
Status: Verified
Type: Technical
Publication Format(s) : TEXT
Reported By: Stephen James
Date Reported: 2013-11-11
Verifier Name: Ben Campbell
Date Verified: 2015-07-22

Section 5.1 says:

rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF

It should say:

rtcp-xr-attrib = "a=" "rtcp-xr" [ ":" xr-format *(SP xr-format)] CRLF

Notes:

The ABNF for the attribute is causing some interoperability issues.
The text as written shows that the colon is required while the parameters are optional.
This leaves the format: "a=rtcp-xr:" the required format. Vendors are using "a=rtcp-xr" which strictly violates the ABNF above. Moving the ':' into the optional part seems correct.

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