RE: IETF54- Informal discussion on BC Model for DS-TE

[neil.2.harrison@bt.com]

Francois,

Your comments seem OK to me.......but I have to point out that my
observation on pre-emption was quite general (so not just this DS/TE case,
and it can also apply to other network technologies like ATM or even SDH
VCs).  I am not so concerned for cases where traffic that gets dropped stays
dropped (which is similar to the 1:1/N protection switching case when 'extra
traffic' which is using the protection path gets dropped when the 'working'
traffic path fails), but rather where multiple priorities exist and one get
get a knock-on effect of 'bumped' traffic subsequently 'bumping' lower
priority traffic (and so on).

regards, Neil

> -----Original Message-----
> From: Francois Le Faucheur [mailto:flefauch@cisco.com]
> Sent: 15 July 2002 15:22
> To: neil.2.harrison@bt.com
> Cc: te-wg@ops.ietf.org
> Subject: RE: IETF54- Informal discussion on BC Model for DS-TE
> 
> 
> Neil and all,
> 
> At 10:47 15/07/2002 +0100, neil.2.harrison@bt.com wrote:
> >I'd agree with this too......our experience of pre-emption 
> schemes in other
> >technologies tells us we would want to be able to disable them.
> 
> So we're hearing:
>          -i- it should be possible to disable preemption
>          -ii- when preemption is disabled, the Model should 
> still work 
> reasonably well.
> Fair enough.
> 
> I also understand that:
>          -iii- there should be effective use of bandwidth (ie good 
> bandwidth sharing among CTs).
>          -iv- there should be some isolation (ie a CT cannot 
> hogg the bw of 
> another CT).
>          -v- there should be protection against QoS 
> degradation (at least 
> of the premium CTs e.g Voice, Premium DAta...).
>          -vi- the BC model should be reasoanly simple and 
> shouldn't require 
> additional IGP extensions.
> Is this right, or are any of those actually non-goals?
> 
> Thanks
> 
> Francois
> 
> 
> >regards, Neil
> >
> > > -----Original Message-----
> > > From: Geib, Ruediger [mailto:Ruediger.Geib@t-systems.com]
> > > Sent: 15 July 2002 08:21
> > > To: gash@att.com
> > > Cc: te-wg@ops.ietf.org
> > > Subject: RE: IETF54- Informal discussion on BC Model for DS-TE
> > >
> > >
> > > Hi Jerry
> > >
> > > > > Russian Dolls model does not "mandate" the use of
> > > > > preemption. It just uses it for what it has been specified
> > > > > for (ie bounce off LSPs when needed).
> > > > >
> > > > > My impression is that it is just not possible to 
> simultanesouly :
> > > > >          -(i) ensure bandwidth sharing (ie no 
> bandwidth wastage)
> > > > >          -(ii) ensure bandwidth isolation (ie a CT cannot
> > > > >               have some of its bandwidth taken by another CT)
> > > > >          -(iii) refuse to use preemption
> > > > >
> > > > > I believe SPs have requirements for (i) and (ii) and don't
> > > > > have a problem with using preemption, which is an existing
> > > > > TE mechanism.
> > >
> > > > Not all SPs assume the use of preemption.  So the default BC
> > > > model should not assume ('require') the use of preemption to
> > > > operate efficiently.
> > >
> > > Yes, that's correct. I'd prefer a default BC model where
> > > preemption is an optional add on instead of a mandatory feature.
> > >
> > > Regards, Rüdiger
> > >
> > >
> > >
> 
> 
> _________________________________________________________
> Francois Le Faucheur
> Development Engineer, IOS Layer 3 Services
> Cisco Systems
> Office Phone:          +33 4 97 23 26 19
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