The MPLS-OPS Archive

[Srihari Raghavan <sraghava@vt.edu>]

Hi,
  Some details about Diffserv+MPLS. I am not concentrating on the
variable-bit rate part. But general Diffserv+MPLS.

  Diffserv and MPLS can be combined for effective use in backbone networks.
They mutually help each other, even though MPLS operates in layer 2.5ish and
Diffserv is a layer 3 solution.

  Diffserv aids MPLS in two ways.
     1. MPLS only aids layer3 QoS and does not introduce a new QoS arch. So,
Diffserv can help
        MPLS by providing a QoS arch. to MPLS networks.

     2. More importantly, MPLS being a path-oriented mech. when used in
backbone networks can
        give rise to scalability problems esp. with RSVP-TE (I think there
are lots of extensions
        proposed to overcome this problem like summary refresh etc.,)

        MPLS+DS combination gives rise to networks where there is no
per-flow state to be maintained in core routers. Only per-LSP state is to be
maintained. If diffserv is not used, and IntServ is used with MPLS (as is
proposed in a new draft), I think you will have the overhead of
maintaining both per-flow state and per-LSP state. With LSP aggregation, one
can reduce the number of LSPs. Please correct me if I am wrong.

   MPLS aids diffserv in many ways.
     1. When link failures happen, MPLS-based fast rerouting aids diffserv
in guaranteeing much
        stricter QoS. Of course, link failures are not day-to-day occurence
in backbone networks

     2. Traffic Engineering is provided by MPLS to diffserv. You can
visualize different paths
        for different PHB groups, resource-preemption, different protection
levels for different
        PHBs etc.,

     3. When you want to use diffserv in heterogeneous link-layer
envioronments, for example, in ATM networks, MPLS is pretty much the best
option to go for. Of course this may not be a great need, given the
excellent QoS guarantees supported by ATM.


A draft to look out for : draft-ietf-mpls-diff-ext-09

Hope it helps

Srihari Raghavan
Graduate Student
Dept. of Computer Science
Virginia Tech
=========================

-----Original Message-----
From: chetan jain [mailto:jcchetan@yahoo.com]
Sent: Monday, April 30, 2001 11:17 AM
To: mpls-ops@mplsrc.com
Subject: MPLS


Hi Everybody,

variable-rate video sources wanting to connect through
DiffServ and MPLS network

can any one tell me how the application interfaces
with DiffServ, how DiffServ interfaces with MPLS.

Thanks in advance

Chetan


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