Subject: Re: QOS Routing - high level comments (long)

From: Steve Deering <[email-masked]>
Date: Fri, 5 Apr 1996 16:36:03 PST

My earthquake story was intended to be a meta-comment on the reservations
vs. no reservations debate, rather than a contribution to it.  (Jed Donnelley
is already doing a fine job of arguing a position very close to my own.)
I just found it ironic that Noel's example of a situation in which "sharing
the pain" of congestion was unacceptable was exactly the same scenario
I use to illustrate why sharing the pain might be preferable to busy
signals.

> From:	[email-masked] (Bill Zaumen)
> 
> At the risk of quibbling, this may be a bad example: the phone company
> tweaked the system so as to give more service to outgoing calls than
> incoming calls.

Yes, that's quibbling.  :-)  In fact, the same problem existed in the
outgoing direction -- it wasn't until six hours after the earthquake that
I was able to get a call through to my relatives on the outside.  During
that six hours, some small fraction of people got perfect 64kbps channels
to the outside, while the rest of us got nothing.  Many more people would
have been served with a system that allowed degraded operation.

>                   The rationale was that a person calling out would
> typically ask the person they contacted to call other friends and
> relatives to tell them that they were OK, whereas those calling in
> would make their calls independently (and approximately concurrently).

Sounds like a job for multicast!  :-)

> From:	[email-masked] (SanJeev Rampal)
> 
> Seems to me the example was more of a problem with the granularity of the 
> reservation system (64 kbps) than reservation techniques per se. For
> instance  with an ATM (:-)) telephone network, an intelligent terminal
> could progressively try lower and lower reservations until it got through.
> (Precisely  the reason that the Telcos came up with a transport network
> with  infinitesimal (!) bandwidth granularity... ). 

Oh great, fill up the bandwidth with signalling packets!

> From:	Daniel Zappala <[email-masked]>
> 
> The question is...given an application like this, how often will it just
> degrade to text form due to congestion limitations.  Only after
> earthquakes?  Every day between 9am and 5pm?

That depends on what it takes to keep the customers satisfied.  If it
degrades too often when making "conventional" local or long-distance calls,
the customers would presumably take their business to another carrier who
has provisioned their network to avoid such degradation.  (I understand that
the big US long-distance companies now size their networks so as to avoid
blocking any calls on Mothers Day -- I presume this is done either because
it is cheap to do and an easy way to avoid irritating their customers,
or because it has become necessary in order to avoid losing customers to
the competition.)  Therefore, I think competition will ensure that the
degradation occurs only in exceptional bandwidth shortages, such as
natural disasters, rock concert ticket releases, or when communicating
with submerged submarines or spaceships on their way to Mars.

>                                                Any time my neighborhood
> malcontents flood our local link?

Routers ought to prevent any source from monopolizing a link if there
are competing sources, e.g., by using RED or some approximation of Fair
Queueing.  Your household's share of the link ought to big enough to not
require your voice application to degrade to text mode.

I'll concede Lee Breslau's and John Wroclawski's point that allowing
reservations is not the same as requiring reservations, but that raises
questions about whether or not service providers would end up selling all
their bandwidth as "premium" reserved service, effectively eliminating
non-reserved service.  And that is a debate that I definitely don't
have the time or energy to take up right now.

Steve

---

From: "Brian Carpenter CERN-CN" <[email-masked]>
Date: Sat, 6 Apr 1996 17:15:43 +0200 (MET DST)

Steve
> have the time or energy to take up right now.
So I will. If best effort service costs X dollars/month and
a given QOS costs Y dollars/hour, where X and Y are on the
same order of magnitude, then the market will take care of
things.

  Brian Carpenter

---

From: Masataka Ohta <[email-masked]>
Date: Sun, 7 Apr 96 19:02:55 JST

Brian;

> same order of magnitude, then the market will take care of

As long as there is free competetion between providers, yes.

But, too much CIDRization will develop local monopoly.

							Masataka Ohta