From: grayt@Software.Mitel.COM (Tom Gray)
Newsgroups: comp.dcom.cell-relay
Subject: Re: Curious attitude ...
Date: 29 Jul 92 13:17:08 GMT
Organization: Mitel. Kanata (Ontario). Canada.

In article <22064@venera.isi.edu> finn@dalek.isi.edu (Greg Finn) writes:
>In article <12409@pinard> grayt@Software.Mitel.COM (Tom Gray) writes:
>
>>However if you are attempting to provide service comparable to the
>>existing voice network and extend these services to include
>>associated video and data service, you will have to come up with a
>>system comparable to ATM.
>
>	I never said that I was.  Nor have others that have commented
>here recently.  The issue is whether or not ATM is a good LAN
>technology, not whether it is a good technology for carrying
>isochronous data.

ATM as I stated later in the same posting is not a technology
for carrying isochronous data. It is a very poor technology for
carrying isochronous data. Do you really wish to invoke 
packet techniques to carry voice traffic around a building?
However ATM and by this most people mean the suite of protocols
being developed for B-ISDN is a technology being developed to
supply multi-service multi-media service to the user.

ATM/B-ISDN can provide service comparable to the voice network
and it can provide LAN and video service and it can combine
this into multi-service applications.

Now the LAN  industry itself is rapidly accepting ATM. This
industry expects ATM to supplant existing protocols by
1995. This is occuring because of the intractable management
problems with the multitude of existing protocols. ATM
is seen as the means for creating a workable network
management system. I refer you to the paper
Conquering Complexity by John Hart of 3Com which
is in the proceedings of the 1990 IEEE Local Computer
Network Conference which makes these points. 

To repeat the point, the manufacturers of LAN equipment
regard ATM as the near term technology for their 
business. Does this make a point that ATM can be
used profitably and efficiently for LAN problems.
>
>	The carrying of voice/video traffic over TCP/IP shows that it
>can carry isochronous traffic, just as ATM can carry asynchronous
>traffic.  If someone makes a statement that isochronous traffic such
>as voice/video can't be carried conveniently over long-haul TCP/IP
>system, I will point out the error.

Voice has been carried in statistically multiplexed networks
since the 1950's. These networks have well known problems
of absolute delay, delay skew, delay jitter etc. which
make them unsuitable for creating multiservice networks.
Data networks such as the Internet work with routers which
are far too costly and unreliable to provide adequate
voice service.

Now voice can be carried over the Internet if the requirements
aren't particularly demanding in terms of performance and
cost. My Ford Tempo can carry packages but no one would
use it in the long haul transport business.

>

>	There is a larger looming issue.  Nearly artifact-free
>compression algorithms now exist that are used to decrease the
>bandwidth loading of both voice and video.  They are often
>variable-bit-rate.  This class produces VERY bursty transmission
>behavior.  Those of you who are so sure that video data will dominate
>MAN and WAN traffic in the future may find yourselves in an
>interesting situation.

Video will not dominate network traffic. Voice traffic is an
order of magnitude greater than all other services combined.
Therefore voice considerations will dominate the design of
networks for the forseeable future. This was reported in
IEEE Network for May or June of 1990.

Now the mention of compression algorithms is also interesting.
It is interesting because ATM/B-ISDN is being designed to
create a repeatable network which can be modelled so that
reliable predictions can be made. ATM is being designed so that
network management packages can be created which can predict
the bandwidth requirements of bursty and non-bursty traffic.
I refer you to the work of Hui (as  one example) as reported
in the December 1991 issue of JSAC which reports techniques
which will provide performance prediction policies.

Additionally ATM is being designed to provide for
protocols that can optimize the use of bandwidth. It
is being designed so that adaptation layers can be
provided to supply load smoothing (Fast Reservation,
String, Burst Announcing etc.). 

>
>>As others have pointed out, ATM/B-ISDN has been designed to work in
>>a multi-service environment. 
>
>	I don't disagree.  The ISO suite was designed to replace
>TCP/IP by the late 80's.  That ATM will work better than other
>link-layer protocols in LANs is an issue much up in the air.

As I have pointed out before ATM is not just a link layer protocol.
It is a family of protocols that are being designed to create
multi-service facilities that can be deployed practically.
As I have pointed out, it is now the protocol of choice for
the LAN industry which expects ATM to supplant existing
protocls by 1995.
-- 
i.sinature