RFC 3261 defines the Require header of a request to contain a list of SIP extensions that are required to properly process the request. RFC 3261 requires a SIP UA to examine the Require header of each incoming request, and if contains an extension name that the phone does not implement (including if it does not recognize the extension name), the UA is required to reject the request with a 420 Extension Not Implemented response.
This may seem academic, but proper processing of Require is important in various situations: It allows the other party to detect and compensate for non-implementation of extensions, it allows for more graceful failure when a call requires an extension to process successfully, and it is an integral part of sipX's authorization scheme(*).
It appears that the Polycom phone does not process the Require field at all. The interopability test described at
http://interop.pingtel.com/#Require shows that the phone does not reject requests with "Require: merde".
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(*) INVITEs with "Replaces: xxxx" and "Require: replaces" do not require authorization.
Bug
Closed
Major
Polycom phone does not properly process "Require" header
frame 44:
INVITE sip:202@10.1.1.41 SIP/2.0
From: "206"<sip:206@victoria.pingtel.com>;tag=94bf30f0-a0101b9-13c4-1fd4-1cd45e91-1fd4
To: <sip:*63202@victoria.pingtel.com>
Call-Id: 94bf0488-a0101b9-13c4-1fd4-6d5c3028-1fd4@victoria.pingtel.com
Cseq: 1 INVITE
Supported: replaces
User-Agent: LG-Nortel LIP 6830 v1.2.38sp SN/00405A187C1A
Contact: <sip:206@10.1.1.185:5060>
Require: merde
frame 50:
SIP/2.0 200 OK
From: "206" <sip:206@victoria.pingtel.com>;tag=94bf30f0-a0101b9-13c4-1fd4-1cd45e91-1fd4
To: <sip:*63202@victoria.pingtel.com>;tag=C70E298B-531CEE64
CSeq: 1 INVITE
Call-ID: 94bf0488-a0101b9-13c4-1fd4-6d5c3028-1fd4@victoria.pingtel.com
Contact: <sip:202@10.1.1.41>
User-Agent: PolycomSoundPointIP-SPIP_301-UA/2.2.2.0084
A correct response (420) is shown by an old Pingtel Xpressa phone:
frame 150:
INVITE sip:203@10.1.20.215;LINEID=02a6e739b83cee7cafa833b315d14789 SIP/2.0
From: "206"<sip:206@victoria.pingtel.com>;tag=94bf47e8-a0101b9-13c4-1ffc-69f68c8d-1ffc
To: <sip:*63203@victoria.pingtel.com>
Call-Id: 94bf0630-a0101b9-13c4-1ffc-f071fb4-1ffc@victoria.pingtel.com
Cseq: 1 INVITE
Supported: replaces
User-Agent: LG-Nortel LIP 6830 v1.2.38sp SN/00405A187C1A
Contact: <sip:206@10.1.1.185:5060>
Content-Type: application/sdp
Content-Length: 295
Require: merde
frame 151:
SIP/2.0 420 Bad Extension
From: "206"<sip:206@victoria.pingtel.com>;tag=94bf47e8-a0101b9-13c4-1ffc-69f68c8d-1ffc
To: <sip:*63203@victoria.pingtel.com>
Call-Id: 94bf0630-a0101b9-13c4-1ffc-f071fb4-1ffc@victoria.pingtel.com
Cseq: 1 INVITE
Unsupported: merde