RFC 7913, "P-Access-Network-Info ABNF Update", June 2016Source of RFC: IETF - NON WORKING GROUP
Errata ID: 6678
Publication Format(s) : TEXT
Reported By: Dinoop Paloli
Date Reported: 2021-09-06
Throughout the document, when it says:
It should say:
As per the Introduction section,
"As the P-Access-Network-Info header field is mainly used in networks
defined by the 3rd-Generation Partnership Project (3GPP), where new
values following the 'generic-param' rule have been defined
[TS.3GPP.24.229], the update is not considered to cause issues with
backward compatibility. "
This is not true and there is backward compatibility issue due to change in ABNF form of extension-access-info from gen-value to generic-param
As per the old RFC the following header was valid,
P-Access-Network-Info: 3GPP-UTRAN-TDD; utran-cell-id-3gpp=23456789ABCDE; "a=c";
See the parameter "a=c" which was allowed as part of "gen-value = token / host / quoted-string"
But generic-param has to be in the form
generic-param = token [ EQUAL gen-value ]
due to this a simple quoted string become invalid.
This causes backward compatibility of new SIP stacks and old networks.