Subject: LSP utilization

From: Raymond Law <[email-masked]>
Date: Sat, 28 Jul 2001 15:51:08 -0400

What is the utilization of LSPs in a real MPLS domain?  It seems that the 
LSP utilization should be efficient since the LSPs are configured as such 
by traffic analysis and administrative means.  Is there a situation in 
which a LSP is overutilized and another LSP may be underutilized?

Thanks.
Ray,

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From: Raymond Law <[email-masked]>
Date: Sat, 28 Jul 2001 16:02:37 -0400

So has anyone looked into increasing the efficiency of LSP usage in a MPLS 
domain or is there any solution already out there?

Thanks.
Ray,

At 03:58 PM 7/28/01 -0400, you wrote:

>Of course there is.  It's called 'real world'.
>
>TE is a tool, but not everything in the world (or anywhere near to that) is
>always TE'ed.
>
>Any notion that MPLS LSP utilization is always efficient is ridiculous.
>
>On Sat, Jul 28, 2001 at 03:51:08PM -0400, Raymond Law wrote:
>--
>Christian Kuhtz <[email-masked]> -wk, <[email-masked]> -hm
>Sr. Architect, Engineering & Architecture, BellSouth.net, Atlanta, GA, U.S.
>"I speak for myself only.""

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From: Robert Raszuk <[email-masked]>
Date: Sat, 28 Jul 2001 17:54:11 -0700

Hi Ray,

What you are describing is in fact very true. In can be caused by nature
of Internet or even by geographic/time zone characteristics of your
users.

That was also the reason why some providers has requested the ability to
dynamically redimention the configured LSPs (just build a new one with a
adjusted bw). Now this new bw value is taken from the averaged real
traffic rates flowing via such an LSPs. 

I don't think such an ability requires an IETF draft as the solution to
address this is pretty simple, is contained within a router itself and
can be enabled by just one knob.

R. 

> Raymond Law wrote:
> 
> For example, once an MPLS solution is deployed after a pre-deployment
> analysis or simulation which found an optimal LSP setup in which all LSPs
> have 50% utilization. If some LSPs have 80% utilization whereas other LSPs
> have 30% utilization in deployment.
> 
> Or, due to the dynamic nature of Internet traffic, some LSPs become
> congested while other LSPs are underutilized.  Maybe a LSP setup
> specifically for best effort traffic experience a large amount of traffic
> during the busy hours and that LSP become overutilized.
> 
> Does any drafts address this problem or has any solution been attempted or
> proposed in dealing with this issue?
> 
> Thanks.
> Ray,
> 
> At 06:54 PM 7/28/01 -0400, you wrote:
> >On Sat, Jul 28, 2001 at 04:02:37PM -0400, Raymond Law wrote:
> >Define "efficient".  Then we can start talking about what the problem
> >may be, whether it needs to be solved, and how to solve it.
> >
> >
> >
> >eric
> >
> > > Thanks.
> > > Ray,
> > >

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From: Eric Osborne <[email-masked]>
Date: Sat, 28 Jul 2001 21:00:42 -0400

> have 30% utilization in deployment.

So first off, I assume you really mean s/MPLS/MPLS-TE/ in this
context.

TE LSPs (or most LDP LSPs) map to FECs.  A FEC is (currently) a
combination of address/mask.  And most traffic is going to be
headed to a FEC that is the BGP next-hop for a particular set of
traffic.  So what you're really asking is (I think) how to balance
traffic to BGP exit points - right?

One thing MPLS-TE can give you is better load-balancing than IP
forwarding, because of the opportunity for unequal-cost forwarding.
Since this is [email-masked], I'll leave the issue of such forwarding
algorithms alone other than to say that they're vendor specific.  But
in the one implementation I'm intimately familiar with, there's a fair 
bit of control as to how you balance between multiple LSPs to the same 
FEC.

> proposed in dealing with this issue?

I believe (but have not looked recently) that some of the
operationally-focused TE drafts discuss this.  If I understand what
you're saying (and I may not understand), then this is the same type
of traffic engineering problem one has with ATM VCs and other dynamic, 
bandwidth/QoS-related traffic-trunk stuff.  So since the question
probably reduces to the same whether it's MPLS or ATM, the answer for
ATM (mostly periodic reoptimization) should be the same.

eric

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From: Eric Osborne <[email-masked]>
Date: Sat, 28 Jul 2001 18:54:29 -0400

eric

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From: Raymond Law <[email-masked]>
Date: Sat, 28 Jul 2001 19:43:55 -0400

Thanks.
Ray,