Remarks on H.450.x and H.225.0

Orit Levin orit at RADVISION.COM
Mon Dec 1 10:59:59 EST 1997

Hello, Editors!

We are working know on the Supplementary Services stuff and came across some pitfalls in the last (Geneva) versions of the above protocols. It would be helpful to fix them before Geneva. I am listing them below:

1. H.450.2 Clause 10.5
<<FACILITY message containing a callTransferInitiate invoke APDU and conferenceGoal = "invite">> is mentioned here. There is no conferenceGoal in FACILITY message. Possibly this mistake derives from the SETUP message, mentioned later in the same clause, which indeed has conferenceGoal field.

2. H.225.0 Annex H - ASN.1
InfoRequestResponse ::= SEQUENCE --(IRR)
        nonStandardData NonStandardParameter OPTIONAL,
        perCallInfo             SEQUENCE OF SEQUENCE
                originator              BOOLEAN,
        } OPTIONAL,

The field "originator" is no longer OPTIONAL (the way it was defined in V.1), which makes the situation NOT backward compatible. Was there any reason for that change, or it just a mistake? In any case, because of the ASN.1 encoding rules, this situation highly undesirable.

3. H.225.0 Annex H - ASN.1
All ,but UI-UUIE, XXX-UUIE messages have callIdentifier field. We propose to add this field for UI-UUIE message as well ("for future sake"):
        protocolIdentifier      ProtocolIdentifier,
        callIdentifier          CallIdentifier


4. H.450.2 Clause
This clause is talking about Call Transferring in case of GK Call Routed model and both Q.931 Signaling and H.245 protocol are "routed" by the GK. According to H.323V.2 GK's Call Routed model where Q.931 Signaling is routed by the GK, but H.245 messages flow directly is legal and more efficient. It seems that the clause above doesn't cover this case. In order to provide a working solution for this case, an additional OPTIOANAL field "h245Address" should be added to Facility-UUIE message as follows:

H.225.0: Add "h245Address" field to the Facility message:

Facility-UUIE ::= SEQUENCE
        protocolIdentifier              ProtocolIdentifier,
        alternativeAddress              TransportAddress OPTIONAL,
        alternativeAliasAddress SEQUENCE OF AliasAddress OPTIONAL,
        conferenceID                    ConferenceIdentifier OPTIONAL,
        reason                          FacilityReason,
        callIdentifier                  CallIdentifier,
        destExtraCallInfo               SEQUENCE OF AliasAddress OPTIONAL,
        remoteExtensionAddress          AliasAddress OPTIONAL,
        tokens                          SEQUENCE OF ClearToken OPTIONAL,
        cryptoTokens                    SEQUENCE OF CryptoH323Token OPTIONAL,
        conferences                     SEQUENCE OF ConferenceList OPTIONAL,
        h245Address                     TransportAddress OPTIONAL



Orit Levin
RADVision Inc.                          E Mail: orit at
575 Corporate Dr., Suite 420            Tel:    201-529-4300 ext. 230
Mahwah, NJ 07430                        Fax:    201-529-3516

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