version

Rosen, Brian Brian.Rosen at MARCONI.COM
Fri Apr 27 10:50:55 EDT 2001


Frank,

below is the full text what H.245 Section B.3.1 says about the encryptionSync field:

        The encryptionSync field shall be used by the master when acknowledging the opening of a channel by a slave. It is used to provide the encryption key value and the synchronization point at which the key should be used. For H.323, the syncFlag shall be set to the RTP dynamic payload number which matches the key.

H.235 Section 8.5 describes the use and purpose of encryptionSync:

        During the protocol exchange that establishes the logical channel, the encryption key shall be passed from the master to the slave (regardless of who initiated the OpenLogicalChannel). For media channels opened by an endpoint (other than the master), the master shall return the initial encryption key and the initial synchronization point in the OpenLogicalChannelAck (in the encryptionSync field). For media channels opened by the master, the OpenLogicalChannel shall include the initial encryption key and the synchronization point in the encryptionSync field.

My understanding is that encryptionSync is part of the OLC-Ack message. As such, encryptionSync implicitly acknowledges the OpenLogicalChannel, although of course actually the OpenLogicalChannelAck is intended to explicitly acknowledge the OpenLogicalChannel. Thus, I do not really see an error.

Does this answer your question? Do you see need for further clarification of either passage?

Kind Regards

Martin Euchner.
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        -----Ursprüngliche Nachricht-----
        Von:    Frank Derks [SMTP:frank.derks at PHILIPS.COM]
        Gesendet am:    Freitag, 27. April 2001 10:44
        An:     ITU-SG16 at mailbag.cps.INTEL.COM
        Betreff:        B.3.1/H.245v8 - Error in the description of the encryptionSync field

        B.3.1/H.245 describes the use of fields in the openLogicalChannel
        message. The text about the encryptionSync field looks like a
        literal copy of the corresponding text for the OpenLogicalChannelAck
        message. This would not seem to be correct, because it talks
        about the acknowledgement of the opening of a channel by the
        slave. Shouldn't the text read:

        "The encryptionSync field is (shall?) used by the master to provide
        the ebcryption key value and the synchronization point at which the
        key should be used. ....."

        Regards,

        Frank

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