Hi
I believe that the following paragraph from the H.323 Annex E may be understood differently by different people:
E.2.3.5 Session field The session field shall be present in all payloads. The Session value shall contain the CRV from the Q.931 messages. Specifically, the call reference flag shall be included as the most significant bit of the CallReferenceValue. This restricts the actual CRV to the range of 0 through 32767, inclusive.
I think this means that the Annex E session field is different (in the Flag bit) for Setup and Connect messages of the same call. (Exactly like CRV is). I agree that the alternation of the 16th bit of the Annex E session field in the messages of the same session (call) moving in different directions is required, but I do not think that the described behavior is obvious from the field's name and its description.
If there is agreement on the fact that the messages belonging to the same call but moving in opposite directions shall have different values of the 16th bit of the Annex E session field, that probably we need to state this explicitly in the E.2.3.5. I agree that this is ALMOST what is written their, but we all know how ambiguous may be the CRV-like field description.
Sasha
Alexander(Sasha) Ruditsky RADVision Ltd. 24 Raul Wallenberg St. Tel Aviv 69719 Israel
Tel: +972-3-645-5220 Fax: +972-3-645-6464 Direct: +972-3-645-5273 sasha@radvision.rad.co.il
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Sasha,
As you stated, the flag bit in the session field of Annex E/H.323 messages shall be set to the same value as the CRV in the Q.931 message found in the payload.
Would you like to propose clarifying text? I'll put it into the IG for review in Portland.
Paul
----- Original Message ----- From: "Sasha Ruditsky" sasha@TLV.RADVISION.COM To: ITU-SG16@mailbag.cps.intel.com Sent: Sunday, July 02, 2000 12:01 PM Subject: Annex E Question.
Hi
I believe that the following paragraph from the H.323 Annex E may be understood differently by different people:
E.2.3.5 Session field The session field shall be present in all payloads. The Session value shall contain the CRV from the Q.931 messages. Specifically, the call reference flag shall be included as the most significant bit of the CallReferenceValue. This restricts the actual CRV to the range of 0 through 32767, inclusive.
I think this means that the Annex E session field is different (in the Flag bit) for Setup and Connect messages of the same call. (Exactly like CRV is). I agree that the alternation of the 16th bit of the Annex E session
field
in the messages of the same session (call) moving in different
directions
is required, but I do not think that the described behavior is obvious from the
field's
name and its description.
If there is agreement on the fact that the messages belonging to the
same
call but moving in opposite directions shall have different values of
the
16th bit of the Annex E session field, that probably we need to state this explicitly in the E.2.3.5. I agree that this is ALMOST what is written their, but we all know how ambiguous may be the CRV-like field description.
Sasha
Alexander(Sasha) Ruditsky RADVision Ltd. 24 Raul Wallenberg St. Tel Aviv 69719 Israel
Tel: +972-3-645-5220 Fax: +972-3-645-6464 Direct: +972-3-645-5273 sasha@radvision.rad.co.il
For help on this mail list, send "HELP ITU-SG16" in a message to listserv@mailbag.intel.com
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I'm not sure if anyone still does it, but some switches used to use one-byte CRVs. A note about mapping 8 bit CRVs to 16 bit CRVs might be useful.
For example, "If the CRV in the Q.931 message is only 8 bits, the CRV Flag is mapped to the 16th bit of the Session Field and bits 1-7 of the original CRV are mapped to bits 1-7 of the Session Field. The remaining bits are set to zero."
But perhaps this is already present.
Chip
At 02:41 AM 7/3/00 -0400, Paul E. Jones wrote:
Sasha,
As you stated, the flag bit in the session field of Annex E/H.323 messages shall be set to the same value as the CRV in the Q.931 message found in the payload.
Would you like to propose clarifying text? I'll put it into the IG for review in Portland.
Paul
----- Original Message ----- From: "Sasha Ruditsky" sasha@TLV.RADVISION.COM To: ITU-SG16@mailbag.cps.intel.com Sent: Sunday, July 02, 2000 12:01 PM Subject: Annex E Question.
Hi
I believe that the following paragraph from the H.323 Annex E may be understood differently by different people:
E.2.3.5 Session field The session field shall be present in all payloads. The Session value shall contain the CRV from the Q.931 messages. Specifically, the call reference flag shall be included as the most significant bit of the CallReferenceValue. This restricts the actual CRV to the range of 0 through 32767, inclusive.
I think this means that the Annex E session field is different (in the Flag bit) for Setup and Connect messages of the same call. (Exactly like CRV is). I agree that the alternation of the 16th bit of the Annex E session
field
in the messages of the same session (call) moving in different
directions
is required, but I do not think that the described behavior is obvious from the
field's
name and its description.
If there is agreement on the fact that the messages belonging to the
same
call but moving in opposite directions shall have different values of
the
16th bit of the Annex E session field, that probably we need to state this explicitly in the E.2.3.5. I agree that this is ALMOST what is written their, but we all know how ambiguous may be the CRV-like field description.
Sasha
Alexander(Sasha) Ruditsky RADVision Ltd. 24 Raul Wallenberg St. Tel Aviv 69719 Israel
Tel: +972-3-645-5220 Fax: +972-3-645-6464 Direct: +972-3-645-5273 sasha@radvision.rad.co.il
For help on this mail list, send "HELP ITU-SG16" in a message to listserv@mailbag.intel.comFor help on this mail list, send "HELP ITU-SG16" in a message to listserv@mailbag.intel.com
------------------------------------------------------------------- Chip Sharp CTO Consulting Engineering Cisco Systems Reality - Love it or Change it. http://www.netaid.org -------------------------------------------------------------------
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participants (3)
-
Chip Sharp -
Paul E. Jones -
Sasha Ruditsky