H225.0 RAS/AnnexG related queries

[Krishna Kr Banka]

Hi ..!!
I have a few queries regarding H.225.0 RAS/AnnexG:
1. AnnexGCommonInfo does not contain Protocol Identifier. Why is it not
required for AnnexG messages?
    Keeping in view, the possible future versions of AnnexG; how shall a
Border Element, on receiving a PDU from some other Border Element know the
version of protocol being used by the sender of the PDU? Also, how does the
sender ascertain which version of protocol the receiver understands? e.g. if
an element is added in version 3 of the protocol, and the recepient can
handle upto version 7, how can it be ascertained that the peer entity would
understand the information sent/received?

2. Why is Sequence Number from 0 to 65535 for AnnexG, while for RAS its from
1 to 65535 (ASN.1 Message Syntax)?
    Also, in section 7.17 (Message Not Understood) of H.225.0 it is
mentioned that RequestSeqNum shall be zero if the message cannot be decoded;
PDU encoding shall fail in such a case.

Regards
Krishna