The MPLS-OPS Archive

[Eric Osborne <eosborne@cisco.com>]

On Sun, Jan 11, 2004 at 07:55:09AM +0000, M. ELK wrote:
> 
> Eric
> 
> Reg
> 
> Quote
> 
> Keep in mind that no matter what bandwidth pool you reserve from, it's a 
> control
> plane reservation only.
> 
> Unquote
> 
> This is a well noted point  but it also raise the following  enquiry  :
> why their is no (separate) mechanism to police the b.w used by a TE tunnel 
> ,at least at
> the head-end .
> 
> say in CSCO implem , is it possible at the head-end  to apply a policer to a 
> TE tunnel ??
> (the logic :  a policer could be applied to an interface , a TE tunnel is 
> treated as an interface at
> the head-end so :  a  policer could be applied to a TE-Tunnel at the 
> head-end ) .

Not currently; the architecture has been that you police what comes
in to your network (from the client side), since assumedly you've got
contracts and SLAs and the like.  To aggregate all this into some
small number of TE tunnels and then police on that tunnel seems far
more arbitrary than most people would be happy with.




eric

> 
> Brgds
> 
> 
> >From: Eric Osborne <eosborne@cisco.com>
> >To: dh8@pobox.com
> >CC: Eric Osborne <eosborne@cisco.com>, mpls <mpls-ops@mplsrc.com>
> >Subject: [MPLS-OPS]: Re: Voice over MPLS
> >Date: Thu, 8 Jan 2004 09:11:29 -0500
> >
> >On Wed, Jan 07, 2004 at 10:38:00PM -0500, Dennis J. Hartmann wrote:
> > >     Is the MPLS TE Automatic Bandwidth Adjustment feature compatible 
> >with
> > > the Guaranteed Bandwidth feature?
> >
> >Not sure what "Guaranteed Bandwidth feature" is; if you mean
> >DiffServ-aware TE (DS-TE), yes, you can use this with auto-bw.
> >They're orthogonal; auto-bw changes the bandwidth request on a tunnel,
> >but other stuff you configure on that tunnel is independant of the
> >amount of BW you reserve.
> >
> > > I'm looking at an implementation on a
> > > 7301 router.  On the CE - PE link, we'll be setting the DSCP to EF 
> >(using
> > > the Priority Queue) for all of the Voice over IP and using WDRR 
> >(Weighted
> > > Deficit Round Robin) as a congestion avoidance mechanism.  We'd rather 
> >not
> > > use Traffic Engineering, but we will if we have to.  The issue we have 
> >is
> > > that we don't want to pre-allocate tunnels that may not be utilized.  
> >This
> > > is the reason we're looking into the Automatic Bandwidth Adjustment.  
> >Any
> > > reccomendations?
> >
> >Like Rajiv said, you have to build tunnels even if they're not in
> >use.  Whether TE will help you or not isn't clear to me.  Keep in mind
> >that no matter what bandwidth pool you reserve from, it's a control
> >plane reservation only.  You can reserve 10Mb from a DS-TE sub-pool
> >that is set to the same size as your EF queue, but you can send 100Mb
> >down the tunnel that's made that reservation, or overload the queue
> >with non-TE traffic.  In order to get some sort of bandwidth guarantee
> >(not a feature, but an architecture), you need:
> >
> >- admission control (make sure you don't let more onto your network
> >   than you've contracted/designed to handle)
> >
> >- proper reservation (if you're going to send X Mbps of traffic,
> >   reserve X Mbps of queue space, modulo any over/underprovisioning you
> >   want to do )
> >
> >- proper enforcement (don't reserve 25Mb for a TE tunnel intending to
> >   carry voice if you only have 10Mb of EF queue space, for example)
> >
> >Add these things together and you can probably get what you're asking
> >for, but it's more than just setting up a tunnel reservation.
> >
> >
> >
> >eric
> >
> > >
> > > Sincerely,
> > >
> > > Dennis Hartmann
> >
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