Subject: Re: QOS Routing

From: [email-masked] (Albert E. Manfredi)
Date: Thu, 4 Apr 1996 15:09:42 -0500

> From:	[email-masked]     4-APR-1996 14:02

> I would like to solicit some responses to two questions
> with regard to QOS routing. Just to start off, I'm giving some
> possible answers. 
> 
> 1. Is there a need for QOS routing in the internet?

Yes, assuming you want the Internet to provide high quality service in
areas that are not strictly data communications in the current sense. 
Internet routing now, I believe, is optimized for data communications and 
for sophisticated end users (computers). It takes short-cuts based on the
nature of traffic it is designed to carry. If the basic nature of that
traffic and those users changes radically, one would have to expect that
the algorithms supporting that traffic and user base will no longer be
optimal. Simple "reachability" criteria, which are all that's now
provided, are not adequate for the general case.

> 2. Assuming that an IP QOS routing architecture is needed, what are the 
> requirements for it? 

You list a bunch, but I would prefer an orthogonal set of axes. For 
instance, for different _types_ of connection, bandwidth (peak,average),
latency, jitter. The types of connection might be pt-pt, pt-mpt,
mpt-mpt, and then whether you want constant or variable bit rate. The 
pricing structure would depend on this multivariate function and,
obviously, on what's easier to provide. (E.g. variable rate, low 
bandwidth, high latency, sloppy jitter would be cheap.) I've left your 
criteria listed below.

Here's the problem, though. The Internet works well because it capitalized 
on the nature of data traffic to set up a worldwide scheme that is simple 
and works well. It avoids use of complicated telephone systems (except 
dedicated leased lines) _because_ its traffic can get by without those 
complicated schemes _and_ because the Internet's end users are many times 
more sophisticated than the telephone system's end users.

If you now expect the Internet to provide services of equal quality to 
other types of data traffic and to dumber end users, some of the
attractive simplicity of the Internet could well vanish. It's not clear to 
me that the IP label by itself is enough to make a truly "integrated 
services Internet" any simpler than a BISDN net (with all those Q.xyz 
protocols that IP folk like to ignore).

Bert
[email-masked]

> - the ability to dynamically determine the QOS achievable on differnent types
> of links, including over NBMA networks 
> 
> - the ability to dynamically determine paths satisfying multiple 
> constraints (e.g., bandwidth and delay)
> 
> - the ability to route short-lived data flows with minimal overhead
> 
> - the ability to prioritize flows, and to permit high priority flows to 
> be established with precedence over lower priority flows
> 
> - the ability to utilize network resources efficiently, both by
> minimizing routing overheads and by routing data flows intelligently,
> using load spreading, global admission control techniques [5] and the like
> 
> - the ability to support link sharing
> 
> - the ability to scale to large numbers of nodes and links, and
> 
> - separation between intradomain and interdomain routing, 
> especially the ability to introduce constraints on routing information 
> flow at the boundary between two organizations.

---

From: [email-masked] (Bala Rajagopalan)
Date: Thu, 4 Apr 1996 15:58:16 -0500

On Apr 4,  3:09pm, Albert E. Manfredi wrote:
> Subject: Re: QOS Routing
> and works well.....
> attractive simplicity of the Internet could well vanish.

This is a good point, and I guess it applies to the notion
of IP QOS in general. But once IP QOS (along with RSVP) is
an accepted notion, the traditional simplicity vanishes, and
QOS routing seems to be just a missing (essential)component
of the picture.

Regards,

Bala Rajagopalan
([email-masked])

---

From: Zheng Wang <[email-masked]>
Date: Mon, 08 Apr 1996 12:44:07 +0100

> bandwidth, high latency, sloppy jitter would be cheap.) I've left your 

One of the problems with QoS routing is that the search with multiple 
constraints is hard. In fact, it can be shown that for some
combination, the problem is NP-complete. In a recent paper, we have argued
that bandwidth and delay should be used as metrics for QoS routing.

For full details, go to
http://boom.cs.ucl.ac.uk/staff/zwang/pub.htm for the paper
"QoS Routing for Supporting Resource Reservation" (to appear in JSAC
special issue on multimedia systems).

Cheers
Zheng