H.225- CRV

Chris Wayman Purvis cwp at ISDN-COMMS.CO.UK
Tue Jan 16 05:16:08 EST 2001


Paul,

I disagree.  CRV is surely unique per connection.
One may be well advised to keep it more unique than that, because in
gatekeepered environments you're liable to end up with problems if you're not
careful because of your note 1 - but if I receive Q.931 messages on separate
TCP connections giving the same CRV I shouldn't expect them to refer to the
same call.  I argue that this is rooted in the principal of TransportAddress
throughout the H.323 standards including the SAPI (IP port number) as well as
actual address.

Regards,
Chris

"Paul E. Jones" wrote:
>
> Archana,
>
> (a) is closer to the way things actually work.
>
> Essentially, you can use whatever values you wish so long as you never place
> two calls to the same endpoint using the same CRV value.  So, whether two
> calls to an endpoint use the same TCP connection or different connections,
> the CRV must be unique.
>
> You should also consider the possibility that an endpoint may have two call
> signaling addresses.  How would you know if this were the case?  The safest
> thing to do is never have two calls with the same CRV at the same time.
> However, if you know that the destination endpoints are unique, you could
> re-use the CRV value.. at least when a Gatekeeper is not being used.
>
> There are also so other properties of CRVs:
>   1) The CRV sent in an ARQ to place a call shall be the same as the
>      CRV in the resulting Setup message
>   2) The CRV sent in an ARQ to accept a call should *not* be taken
>      from the incoming Setup message-- it should be locally generated so
>      that it is a unique between the endpoint and the GK
>
> Paul
>
> ----- Original Message -----
> From: "Nehru, Archana" <archie at trillium.com>
> To: "'Paul E. Jones'" <paulej at PACKETIZER.COM>
> Cc: <ITU-SG16 at mailbag.cps.intel.com>
> Sent: Monday, January 15, 2001 10:28 PM
> Subject: H.225- CRV
>
> > hi all,
> >
> > I have a question about H.323 -CRV values. Q.931 specs says that a CRV
> value
> > should be unique per D-channel layer 2 logical link.
> >
> > In H.225 context, does the above mean that:
> >
> > a) CRV values should be unique across all outgoing H.225 calls that have
> the
> > same "destination" IP address ?
> >
> > b) CRV value only needs to be unique across all H.225 connections using
> the
> > same TCP connection? In other words, if an endpoint A makes two
> simultaneous
> > calls to endpoint B, then the same CRV can be used on both the calls, as
> > long as they use different TCP connections?
> >
> > I would appreciate any help on this.
> >
> > Regards
> > Archana
> >
> >
> >
>
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--
Dr Chris Purvis -- Development Manager
ISDN Communications Ltd, The Stable Block, Ronans, Chavey Down Road
Winkfield Row, Berkshire.  RG42 6LY  ENGLAND
Phone: +44 1344 899 007
Fax:   +44 1344 899 001

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