Subject: Re: int serv on shared media LANs...

From: [email-masked] (Noel Chiappa)
Date: Wed, 27 Sep 95 16:45:25 -0400

From: Jon Crowcroft <[email-masked]>

    we're considering how to deploy CBQ or similar systems on a shared
    LAN ... the problem is not the mechanistic one of how to apply
    something like CBQ ... or even how to apply RSVP to the setup...
    it is how to decide what the flow spec request is mapped onto output

No, the real problem is how to deal with all the legacy hosts on the LAN that
are going to ignore your resource allocations of that LAN's bandwidth! :-)

    anyone think this is worth pursuing (i.e. using int-serv IP to turn legacy
    lans into multimedia multiservice capable beasties)???

Well, I dunno. For a long time, at least, existing LAN technology (i.e.
without hardware support for resource allocation) is a lot of what we're going
to have. As long as the bottlenecks are to P2P links with routers on either
end, we don't have to worry about doing resource reservations on our LAN's,
but I find already that sometimes one of the LAN's at MIT just goes belly-up
as someone dumps a ton of traffic down it. So maybe doing resource allocation
on legacy LAN technology will be an issue.

	Noel

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From: John Wroclawski <[email-masked]>
Date: Wed, 27 Sep 1995 23:33:19 -0400

From: [email-masked] (Noel Chiappa)

   No, the real problem is how to deal with all the legacy hosts on
   the LAN that are going to ignore your resource allocations of that
   LAN's bandwidth! :-)

Turns out you can do resource management on an ethernet by building a
little scheduler box which kills off pkts that "should not" have been
sent at that moment by causing a collision. I think this was invented
by some guy at GTE, but I may misremember. It has been built and
demonstrated to work.

Of course you could (and some folks have) build a distributed
algorithm which runs on all of the hosts on the LAN and manages the
bandwidth allocated to each node. Works great when everyone plays
along, which might be good enough for many situations.

But I imagine the best answer for a majority of current ethernet
installations is to replace the 10BT hub with a switching one which
does resource management. There are product people sniffing around
this already.

		-john

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From: Curtis Villamizar <[email-masked]>
Date: Thu, 28 Sep 1995 00:34:01 -0400

> on legacy LAN technology will be an issue.

Jon,

Why don't you simply take a 10baseT hub and teach it to understand the
RSVP being sent through it on the subnet?  It wouldn't be the first
time bridging devices peaked into the packets to make things slightly
more efficient.

Any legacy beasties that don't speak RSVP get block by the RSVP
reserved traffic.  You can probably still keep some of you hosts on
coax as long as the host Noel is speaking of is on its own 10baseT
port.

You might even be able to sell the thing in a year or two.  You know,
fancy brouchure with *multimedia capable* ethernet hub splattered on
it and all that.  Could be the biggest rage since *SNMP capable*.  ;-)

Curtis

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From: Jon Crowcroft <[email-masked]>
Date: Thu, 28 Sep 95 09:20:54 +0100

>are going to ignore your resource allocations of that LAN's bandwidth! :-)

not true - see john w.'s response, but also consider the token ring or
and also consider that if all the lgacy systems are pure tcp, then
adding CBQ to all the VBR/multimedia application hosts WILL do a lot
better as a mix of traffic sources even on a CSMA/CD net - especially
with regard to delay bounds... 

 jon

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From: Jon Crowcroft <[email-masked]>
Date: Thu, 28 Sep 95 09:29:08 +0100

>time bridging devices peaked into the packets to make things slightly
 
we're doing that too - i just wanted to see how far i could get with a
dumb cable:-)

 >it and all that.  Could be the biggest rage since *SNMP capable*.  ;-)

cheers

 jon

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From: "Jose Eduardo M. S. Brandao" <[email-masked]>
Date: Thu, 28 Sep 1995 09:29:44 -0700 (PDT)

> by some guy at GTE, but I may misremember. It has been built and
To minimize the output delay and colisions, we can reduce the total 
bandwidth to be reserved by the hosts/routers sharing the LAN. It is 
dependent of the number of hosts atached in the LAN.

> along, which might be good enough for many situations.
This idea is rigth. I'm develloping an distributed admission control to 
work at the ethernet. In resume, it receive a call by the RSVP, verify the 
resources and send a Reserv Message to the hosts. The hosts reduce the 
total LAN resurces.

Jose Eduardo. :-).