Subject: RE: MMUSIC/ITU Interoperability Scenarios

From: courtenay_j_m <[email-masked]>
Date: Wed, 26 Jul 1995 14:12:51 +0100

Ari wrote:

> 	T-120 is a great example of re-invention, duplication of 
> 	function and creeping featurism to add "data" exchange to the 
> 	H.320 suite. Some have even seriously suggested running TCP/IP over
> 	the T.120 data pipe...

I have in front of me a *draft* (note) of a *proposed* (note) first 
revision of T.123, which has the following statement (which is not 
intended to form part of the formal document, nor is it likely it ever 
will):

"These issues deserve further discussion:

...

"E. LAN access protocols, like SLIP or PPP, are intentionally
    omitted as being a poor choice for point-to-point connections among
    terminals and MCUs."

Would anyone care to pass comment on this?

Regards,
Mark

--
J Mark Courtenay                    tel. +44 1473 645423
MLB 4 15                            fax. +44 1473 620101
BT Labs, Martlesham Heath
Ipswich, UK IP5 7RE                 [email-masked]

---

From: Jon Crowcroft <[email-masked]>
Date: Thu, 27 Jul 95 09:53:27 +0100

Mark

yes

SLIP and PPP are reasonable serial line protocols developed to provide
commonality where HDLC had failed, but are fairly irrelevant to the
layers that would be considered when discuissing interworking of LAN
based conferncing using RTP/UDP and IP, and ISDN based conferncing
using H.320/H.221 and T.GCC/MCS...
 
I'm giving a talk at BT labs on september 6 on distributed multimedia 
and could clarify things then if you like...

the phrase "LAN access protocols" is inappropriate when describing
SLIP and PPP - SLIP is for dial up access to carry IP (amongst other
things) from a PC over (typicaslly) a phone line to another computer
(which might happen to then route the IP packets onto a LAN, but often
as not is a compuserve or other server site) 

PPP was orgiinally aimed at point-to-point leased line serial line
supprot between _routers_ 

neither has much to do with any discussion of conferecnice control
etc....although i guess people running IP over SLIP or PPP o nan ISDN
line might get a bit confused over the options - i suggest the
appication of the ITU, ATM or ISO OSI layer models will clarify things
quicky!

 jon