Subject: Re: DS-TE Requirements - input sought on "Overbooking"

From: Francois Le Faucheur <[email-masked]>
Date: Mon, 05 Nov 2001 19:34:00 +0100

To all Network Operators interested in DS-TE,

> > Do we agree it is worth adding something on Overbooking in the "DS-TE
> > Reqts" draft?
>
>The concept of overbooking should be addressed in the requirements
>draft. However, i am not sure if overbooking is necessary in the
>protocol extensions.  There are alternative ways to achieve over-
>booking, including adjusting bandwidth of particular LSPs.  While
>this doesn't allow you to overbook different parts of the network,
>i question whether adding this justifies the increased complexity.

Fair question. So, let's poll for an answer before we put it in the 
requirements draft:

Considering a DS-TE solution which allows to enforce different overbooking 
ratios for different Classes of Service, are there Network Operators out 
there (I repeat *Network Operators*) who have a specific requirement for 
enforcing different values for these per-COS overbooking ratios in 
different parts of the network ?

Thanks

Francois

>-dave
>
>
> >
> > Are the two points above reasonable?
> >
> > Thanks for your thoughts
> >
> > Francois
> > _________________________________________________________
> > Francois Le Faucheur
> > Development Engineer, IOS Layer 3 Services
> > Cisco Systems
> > Office Phone:          +33 4 97 23 26 19
> > Mobile :               +33 6 89 108 159
> > Fax:                   +33 4 97 23 26 26
> > Email:                 [email-masked]
> > _________________________________________________________
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> > 06 410  Biot - Sophia Antipolis
> > FRANCE
> > _________________________________________________________
> >

---

From: Jim Boyle <[email-masked]>
Date: Mon, 5 Nov 2001 11:44:55 -0500 (EST)

> different parts of the network ?

and as a question of delineation....

is this a function of protocol, or back-end configuration systems?

back end systems, which can be used to place a bandwidth on an LSP take in
a series of values V[1:N] and run them through a function to distill a
scalar.  This function may take in the class of the LSP as an input, and
could use a class specific oversubscription rate, and can do things no
protocol can do. As an example....  say you have the following:

	V	time series of bytes on an LSP
	dV	differential of V (e.g. dV[i] = dV[i] - dV[i-1] / time)
	gdV = g(dV)
		scalar gdV returned by function g
	bw = f(gdV)
		a non-linear mapping of the scalar gdV

f(gdV) may allow for more overbooking of smaller LSPs than of larger ones.

Also, links may also be adjusted to allow for overbookings as well.

So, Network Operators - to rephrase the question:

Is there a need for per-COS and per-Link based overbooking which requires
protocol hooks for advertising out per-COS, per-Link overbooking factors?

My answer is no.

---

From: Dave Cooper <[email-masked]>
Date: Mon, 5 Nov 2001 14:18:10 -0700

> protocol hooks for advertising out per-COS, per-Link overbooking factors?

As for GX, no.

-- 
Dave Cooper
Global Network Architecture, Global Crossing
Voice: 602.744.3473 - Cell: 916.761.3266

---

From: Marc Binderberger <[email-masked]>
Date: Wed, 7 Nov 2001 22:04:04 +0100

Hello,

> 	[...]

Without the "and":

Overbooking per CoS? Yes.

I want to overbook data services but don't want to overbook real-time 
services.

Overbooking per link? Not really.

 From my ATM colleagues I picked up some discussion about a different 
overbooking factor on a few links. Have to ask for the "why". A motivation 
could be to "squeeze" a particular link to delay a costly upgrade but 
remain with no/low overbooking on the network in general to make life 
(read: fulfilling SLAs) easy.
(But not a motivation for protocol designers I guess)

Some comments:

(i) Today ISIS/OSPF transports the Max Reservable bandwidth and the 
unreserved Bandwidth (per priority) per link which gives us a per-link 
overbooking capability already.

(ii) with global overbooking ratio per CoS it is just a matter of how much 
bandwidth I reserve for my TE-tunnel per CoS. When overbooking data by 4 
but not overbooking voice I reserve bw/4 for data and bw' for voice. So no 
need for per-link ratios.

Regards, Marc
--
Marc Binderberger          <[email-masked]>          Frankfurt/Germany