Empty list of alternate GKs

Discussion in 'VOIP' started by Zeljko, May 13, 2004.

  1. Zeljko

    Zeljko Guest

    Hi everybody,

    It is written in H.323 specs that GK can return empty list of alternate
    gatekeepers in RCF. When this happens endpoint or gateway must clear
    list of alternate GKs received in prior RCFs.

    RegistrationConfirm ::= SEQUENCE --(RCF)
    {
    requestSeqNum RequestSeqNum,
    ....
    alternateGatekeeper SEQUENCE OF AlternateGK OPTIONAL,
    timeToLive TimeToLive OPTIONAL,
    ....
    genericData SEQUENCE OF GenericData OPTIONAL}

    AlternateGK ::= SEQUENCE {
    rasAddress TransportAddress,
    gatekeeperIdentifier GatekeeperIdentifier OPTIONAL,
    needToRegister BOOLEAN,
    priority INTEGER(0..127),
    ...}

    When I see above structures I really don't have a clue how will GK
    indicate empty list?

    Thanks in advance.

    Best regards,
    Zeljko
     
    Zeljko, May 13, 2004
    #1
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  2. Zeljko wrote:
    > Hi everybody,
    >
    > It is written in H.323 specs that GK can return empty list of alternate
    > gatekeepers in RCF. When this happens endpoint or gateway must clear
    > list of alternate GKs received in prior RCFs.
    >
    > RegistrationConfirm ::= SEQUENCE --(RCF)
    > {
    > requestSeqNum RequestSeqNum,
    > ...
    > alternateGatekeeper SEQUENCE OF AlternateGK OPTIONAL,
    > timeToLive TimeToLive OPTIONAL,
    > ...
    > genericData SEQUENCE OF GenericData OPTIONAL}
    >
    > AlternateGK ::= SEQUENCE {
    > rasAddress TransportAddress,
    > gatekeeperIdentifier GatekeeperIdentifier OPTIONAL,
    > needToRegister BOOLEAN,
    > priority INTEGER(0..127),
    > ...}
    >
    > When I see above structures I really don't have a clue how will GK
    > indicate empty list?

    There are 2 ways at least:
    1. Optional alternateGatekeeper's list is not included in RCF.
    2. This list is present but empty (with no elements).
    The second case signals our GK knows about alternate GKs feature but
    don't want to show anything. The first case can mean the same or can
    indicate our GK is not supporting alt GKs feature at all. Anyway all
    alternative GKs known via prior RCFs from the same GK should been
    forgotten (but does the standart realy said MUST? :) ).

    --

    WBR,
    Roman Nikitchenko, http://smartgate.wtelecom.net
    _,,,_|\_/|_,,,_
     
    Roman Nikitchenko, May 13, 2004
    #2
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  3. Zeljko

    Zeljko Guest

    Roman Nikitchenko <> wrote in message news:<c7vrfk$2vik$>...
    > Zeljko wrote:
    > > Hi everybody,
    > >
    > > It is written in H.323 specs that GK can return empty list of alternate
    > > gatekeepers in RCF. When this happens endpoint or gateway must clear
    > > list of alternate GKs received in prior RCFs.
    > >
    > > RegistrationConfirm ::= SEQUENCE --(RCF)
    > > {
    > > requestSeqNum RequestSeqNum,
    > > ...
    > > alternateGatekeeper SEQUENCE OF AlternateGK OPTIONAL,
    > > timeToLive TimeToLive OPTIONAL,
    > > ...
    > > genericData SEQUENCE OF GenericData OPTIONAL}
    > >
    > > AlternateGK ::= SEQUENCE {
    > > rasAddress TransportAddress,
    > > gatekeeperIdentifier GatekeeperIdentifier OPTIONAL,
    > > needToRegister BOOLEAN,
    > > priority INTEGER(0..127),
    > > ...}
    > >
    > > When I see above structures I really don't have a clue how will GK
    > > indicate empty list?

    > There are 2 ways at least:
    > 1. Optional alternateGatekeeper's list is not included in RCF.
    > 2. This list is present but empty (with no elements).
    > The second case signals our GK knows about alternate GKs feature but
    > don't want to show anything. The first case can mean the same or can
    > indicate our GK is not supporting alt GKs feature at all. Anyway all
    > alternative GKs known via prior RCFs from the same GK should been
    > forgotten (but does the standart realy said MUST? :) ).


    Hi Roman,

    Thanks for your reply. Basically H.323 specs are pretty unclear in many
    statements. Regarding this "MUST", I MUST :))) say it depends from where
    you are:

    "If the Gatekeeper wishes to clear the endpoint's list of Alternate
    Gatekeepers, such as when the Gatekeeper is reconfigured to not use
    Alternate Gatekeepers, it shall return an empty list of Alternate
    Gatekeepers to the endpoint in the RCF message."

    Your first way is not correct as no return is not return with empty list.
    When you don't receive alt GK list that means no update of stored list,
    while empty list "MUST" :)) clear stored alternate GKs.

    Can you be more explicit in describing how to recognize this empty list
    at reception???

    Thanks in advance.

    Best regards,
    Zeljko
     
    Zeljko, May 14, 2004
    #3
  4. (Zeljko) wrote in
    news::

    > Can you be more explicit in describing how to recognize this empty
    > list at reception???


    The alternateGatekeeper member is available but has length (size?) 0.

    This all depends greatly on the way your ASN.1 decoder is implemented...

    --
    Andreas
     
    Andreas Sikkema, May 14, 2004
    #4
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