Subject: MPLS VPNs and QoS

From: Juan Diego Otero <[email-masked]>
Date: Tue, 19 Sep 2000 14:21:20 +0100

Hi,

I am trying to add some QoS features to MPLS VPNs

provided with the Eric Rosen et al. method. I want to

use DIFF-SERV combinated with MPLS, but I don't know

exactly how. What is the best option? Establish 1 LSP

between every two sites of the VPN and distinguish CoS

with the use of the EXP field of the MPLS label or establish

1 LSP for every Class of Service and pair of sites? Should

I use RSVP to establish the LSPs with BW guarantees?

Any vendor supports these kind of configuration?

Regards

Diego Otero

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From: Francois Le Faucheur <[email-masked]>
Date: Tue, 19 Sep 2000 18:05:59 +0200

Juan Diego,

At 14:21 19/09/2000 +0100, Juan Diego Otero wrote: 
> with the use of the EXP field of the MPLS label 

Assuming :
        - you want to deploy MPLS VPN over MPLS Router LSRs (as opposed to ATM
LSRs), and
        - you need less than 8 classes of service, 
then I would suggest doing this first approach (i.e. single LSP with COS being
conveyed by the EXP field).
This sort of LSP is referred to as an E-LSP in the "Diff-Serv over MPLS" draft
(draft-ietf-mpls-diff-ext-07.txt).
I see this as the simplest solution (requires the smallest number of LSPs and
associated signaling) and it provides full Diff-SErv support in addition to the
MPLS VPN service.
This is available in commercial products.

> or establish 

If your one goal is to offer Diff-Serv services along with the MPLS VPN
service, then you can establish the E-LSPs via LDP (and IGP routing).

If you also want to minimise aggregate congestions in your network (or put
another way, if you want to optimise the way you utilise your resources), then
you can use MPLS Traffic Engineering simultaneously with MPLS VPN and MPLS
Diff-Serv. In that case, the lowest level of label can be established via RSVP
(and routed via Constraint Based Routing) and bandwidth reserved for each LSP
(note that bandwidth reservation is performed in the goal of performing
admission control of LSPs so they get properly routed over the network,
bandwidth reservation is not really there in teh goal of providing bandwidth
guarantees).
This is available in commercial products.

There is also recent work in the IETF to support Diff-Serv aware Traffic
Engineering. This will involve IGP extensions in order to advertise bandwidth
availability on a per class (or per class-type). Then, it will be possible to
perform Constraint BAsed Routing on a per class basis. You would then set-up
one LSP for each class (along possibly different paths).
I am aware of alpha/beta implementations of this and planned commercial
implementations later in the year, but I am not aware of commercial
implementations for this today.
However, note that this last mode of operation represents an optimum target
model but you certainly don't need to wait for this to deploy Diff-Serv
services jointly with MPLS VPN.

I hope this helps you

Francois

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From: "Bruce Davie" <[email-masked]>
Date: Tue, 19 Sep 2000 12:05:12 -0400

Diego,
 In an MPLS VPN environment you have the option to use basically any of the
QoS techniques that exist for MPLS. For example,
draft-ietf-mpls-diff-ext-07.txt describes how all the features of the
Diffserv architecture can be used in an MPLS environment. This is perfectly
applicable to an MPLS VPN environment.

Using the minimal number of LSPs (i.e. the ones that LDP automatically
establishes among PE routers) and distinguishing CoS based on the EXP bits
is the best choice if:
 - The LSRs in your network are not ATM-LSRs
 - you don't have a need for more than 8 per hop behaviors
 - you don't want to engineer traffic of different CoS over different paths
 - you are happy with Diffserv-style QoS (i.e. no hard bandwidth guarantees)

I would say that this is the most common environment in today's deployments.

If you have ATM-LSRs, or if you need more than 8 PHBs, then you will need
"L-LSPs" just to support diffserv (see the above referenced draft).

If you want to engineer some classes of traffic over different routes than
other classes, you want to use either RSVP-TE (my preference :-) or CRLDP to
establish explicitly routed LSPs for those classes of traffic. Also, if you
want to provide site-to-site bandwidth guarantees, you need to use a
protocol such as RSVP (or CRLDP) to establish LSPs with specific bandwidth
requirements.

I will answer privately your question about what vendors support.

Bruce Davie

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of Juan Diego
Otero
Sent: Tuesday, September 19, 2000 9:21 AM
To: MPLS WG
Subject: MPLS VPNs and QoS

Hi,

---

From: Juan Diego Otero <[email-masked]>
Date: Wed, 20 Sep 2000 13:17:08 +0100

Hi Bruce,

Bruce Davie wrote:

> Also, if you

So, it is possible establish 1 LSP between sites with BW guarantees
and combine it with DIFF-SERV (no more than 8 PHBs)?

One example to clarify my question: suppose a VPN with 3 sites and you want to
have 2 Mbps of BW guarantees between each pair of sites. Suppose you also want
to have 3 Classes of Service for this VPN and you want traffic from different
classes to share the 2 Mbps of BW between
each pair of sites. Is this possible?

Thanks

Diego Otero

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From: Curtis Villamizar <[email-masked]>
Date: Wed, 20 Sep 2000 13:51:44 -0400

> each pair of sites. Is this possible?

The best way to do this is with a signaled E-LSP.  See
draft-ietf-mpls-diff-ext-07.txt

Unfortunately you can specify the aggreagete bandwidth but if you
wanted to specify the bandwidth for individual SAs you'd need to put
them in separate LSPs.

Curtis