H.320 gateways

Brian Rosen brosen at ENG.FORE.COM
Tue Mar 30 11:06:28 EST 1999


I'm in favor of the second approach. 

You could have a termination class H.320 with H.320/audio 
H.320/video and H.320/T.120.  There would be 3 contexts, 
each with different media.  There is a slight ugliness where 
the termination class would define all the parameters for 
all of the streams as one big list, and each of the 
terminations would have all of them.  Unfortunate, but it 
works. 

Christian did not want to infer anything from the name.  
We would need to have some way for the MG to know which 
media was on which termination if we couldn't infer it from 
the name. 

I like this approach because from the MGC, whether the three 
streams are on one gateway, or multiple gateways, it operates 
on them the same way, only the names are changed (to protect 
the innocent).  The MG is built differently in these cases, 
but I don't see any way around that. 

BTW, the H.320 stream could be multi-ported, so you could have 
H.320/7/video. 

> -----Original Message----- 
> From: John Segers [ mailto:jsegers at lucent.com
<mailto:jsegers at lucent.com> ] 
> Sent: Tuesday, March 30, 1999 10:27 AM 
> To: megaco at BayNetworks.COM; ITU-SG16 at mailbag.cps.intel.com 
> Subject: H.320 gateways 
> 
> 
> People, 
> 
> In yesterday's conference call, the subject of H.320 GWs was raised 
> briefly. In my opinion, the connection model and protocol 
> should be able 
> to deal with H.320.  I would like to continue discussion on it on the 
> mailing list. 
> 
> H.320 allows a user to have a session with both audio and video on a 
> single 64 kbit/s channel such as an ISDN B-channel.  The same channel 
> carries some signalling information (frame alignment, bitrate 
> allocation).  To a MG supporting H.320, this means that on a single 
> endpoint, three streams can come in, carrying different types 
> of media. 
> The current connection model of megaco/H.gcp does not cater 
> to this.  I 
> see two possible solutions: 
> 
> The first is to allow multiple media in one context and to 
> describe for 
> terminations the logical streams they carry.  In a picture: 
> 
>                       +----------+ 
>                       |          | 
>                       |          +--------- signalling (FAS, BAS) 
>                       |          | 
> B-channel   ==========+          +--------- audio (16 kbit/s) 
>                       |          | 
>                       |          +--------- video (46.4 kbit/s) 
>                       |          | 
>                       +----------+ 
> 
> The second solution is to have separate terminations for the different

> streams.  They would all "connect to" the same physical endpoint.  In 
> order to properly identify the terminations, it is necessary to have 
> logical names for them.  The physical endpoint they connect 
> may have the 
> hierarchical name proposed in the megaco document. 
> 
> Another example of a H.320 session is the case of two B-channels being

> used for an audiovisual call.  The following frame structure is then 
> possible. 
> 
>    +--------------------------++-----------------------+ 
>    | Channel 1                || Channel 2             | 
>    +-----+--+--+--+--+--+--+--++--+--+--+--+--+--+--+--+ 
>    |Bit 1|B2|B3|B4|B5|B6|B7|B8||B1|B2|B3|B4|B5|B6|B7|B8| 
>    +-----+--+--+--+--+--+--+--++--+--+--+--+--+--+--+--+ 
> 1  | a1  |a2|a3|a4|a5|a6|v1|F ||v2|v3|v4|v5|v6|v7|v8|F | 
> 2  | a7  |a8|a9|a |a |a |v9|F ||v |v |v |v |v |v |v |F | 
> 3  | a   |a |a |a |a |a |v |F ||v |v |v |v |v |v |v |F | 
> 4  | a   |  |  |  |  |a |v |F ||v |              |v |F | 
> 5  | a   |  |  |  |  |a |v |F ||v |              |v |F | 
> 6  | a   |  |  |  |  |a |v |F ||v |              |v |F | 
> 7  | a   |  |  |  |  |a |v |F ||v |              |v |F | 
> 8  | a   |  |  |  |  |a |v |F ||v |              |v |F | 
>    +---------------------------------------------------+ 
> 9  | a   |  |  |  |  |a |v |B ||v |              |v |B | 
> 10 | a   |  |  |  |  |a |v |B ||v |              |v |B | 
> 11 | a   |  |  |  |  |a |v |B ||v |              |v |B | 
> 12 | a   |  |  |  |  |a |v |B ||v |              |v |B | 
> 13 | a   |  |  |  |  |a |v |B ||v |              |v |B | 
> 14 | a   |  |  |  |  |a |v |B ||v |              |v |B | 
> 15 | a   |  |  |  |  |a |v |B ||v |              |v |B | 
> 16 | a   |  |  |  |  |a |v |B ||v |              |v |B | 
>    +---------------------------------------------------+ 
> 17 | a   |  |  |  |  |a |v |v ||v |              |v |v | 
>  . 
>  . 
>  . 
> 80 | a   |  |  |  |  |a |v |v ||v |              |v |v | 
>    +---------------------------------------------------+ 
> 
> (a=audio, v=video, F=FAS, B=BAS). 
> 
> We see that the video stream is split up over two channels.  
> In order to 
> cater to this, it seems we have to allow terminations to receive media

> from and send it to multiple physical endpoints.  The two approaches 
> outlined above can both be extended to allow this. Both 
> extensions will 
> lead to the introduction of logical names for terminations.  In the 
> first approach there will be one termination "containing" two 
> B-channels 
> on one side and three logical streams on the other.  In the second 
> approach there will be three terminations, the one for the 
> video stream 
> referencing both B-channels, the ones for signalling and audio 
> referencing only channel 1. 
> 
> The second approach allows us to keep separate contexts for different 
> media types.  It is then easy to delete, for instance, the 
> video part of 
> a session (session used loosely to desribe the contexts for the audio 
> and video). 
> 
> The first approach groups the streams coming from/going to one user, 
> making it possible to remove a user from a context more easily. 
> 
> 
> Personally, I can't decide which approach I would prefer.  
> How do others 
> feel about these ideas? 
> 
> Regards, 
> 
> John Segers 
> -- 
> John Segers                                  email: jsegers at lucent.com

> Lucent Technologies                                        Room HE 344

> Dept. Forward Looking Work                      phone: +31 35 687 4724

> P.O. Box 18, 1270 AA  Huizen                      fax: +31 35 687 5954

> 

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