Implementation of H450.1 and H450-2

Mikael Grehn mikael at ENVILOGG.SE
Tue Dec 12 07:53:59 EST 2000


This logic was borrowed from the way that we open bi-directional T.120
channels, I believe.  Either endpoint may signal the opening of a T.120
channel, but only one side provides the LCN.  Is this same logic not


----- Original Message -----
From: "Sasha Ruditsky" <sasha at>
To: <ITU-SG16 at>
Cc: "Orit Levin" <orit at>; <paulej at PACKETIZER.COM>
Sent: Monday, December 11, 2000 8:04 AM
Subject: Fast Connect & Bi Directional channels

> Hi
> It looks like there is yet another bug in the fast start procedure.
> It is related to bi-directional channels establishment.
> Standard says that in each bi-directional channel proposal there should be
> unique forwardLogicalChannelNumber.
> Standard says nothing about the value of this field in the accepted
> bi-directional OLC.
> It is known that bi-directional channels need 2 logical channel numbers
> (forward and reverse).
> I see 2 options for the value of forwardLogicalChannelNumber field in the
> accepted bi-directional OLC:
> 1. It may be the same value as the forwardLogicalChannelNumber in the
> corresponding proposal.
> In this case we do not have the logical channel number for the reverse
> direction.
> This works OK till we are in fast start, but after H.245 connection
> establishment
> it will be impossible to perform H.245 actions on the reverse direction of
> the channel.
> 2. It may be the unique logical channel number that is provided by calling
> party and
> identifies the channel -- the reverseLogicalChannelNumber.
> The problem with this is that caller does not know to which proposal this
> channel belongs.
> BTW The same problem exists with the unidirectional channels from callee
> caller and the solution
> is just to find the corresponding proposal, using different channel
> characteristics.
> I personally prefer the second option because it is more correct from the
> H.245 point of view.
> But, In any case it should be decided which is the standard one .
> Sasha
> ***********************************************
> Alexander(Sasha) Ruditsky
> RADVision Ltd.
> 24 Raul Wallenberg St.
> Tel Aviv 69719  Israel
> Tel:       +972-3-645-5220
> Fax:       +972-3-644-2903
> Direct:    +972-3-645-5273
> sasha at
> ***********************************************

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