The MPLS WG Archive

["alex.mondrus" <alex.mondrus@ipoptical.com>]

In general to do an explicit path set up you do not need to use MPLS.

Alex Mondrus

http://www.ipoptical.com


Traffic Engineering - MPLS allows you to set up tunnels
>         with explicit routing so that you can design your routes
>         off-line in order to achieve best traffic distribution to
>         minimize network hot spots (which often occur in OSPF
>         type routing) and improve network capacity efficiency.
>         Load balancing (parallel MPLS tunnels running between
>         a source-dest pair) and trunk protection also become easy.

-----Original Message-----
From: owner-mpls@UU.NET [mailto:owner-mpls@UU.NET]On Behalf Of David
Wilder
Sent: Wednesday, June 21, 2000 12:02 PM
To: Jay Wang
Cc: hasko10@hotmail.com; mpls@UU.NET
Subject: Re: TE


Very well put Jay.

- Dave


> Mike,
>
>     MPLS is not created to support constraint based routing
>     and it doesn't.  It let you set up layer two tunnels using
>     label switching.  An IP network can benefit from the
>     existence of MPLS with at least the following:
>
>     1. Faster data forwarding at the transient (core) routers -
>         This is because there is only label (index) lookup and
>         no IP header processing.  This however became much
>         weaker an argument lately since lots of work that used
>         to be done by software (e.g., header processing,
>         classification) now are typically done in ASIC in vendor's
>         box.
>
>     2. Traffic Engineering - MPLS allows you to set up tunnels
>         with explicit routing so that you can design your routes
>         off-line in order to achieve best traffic distribution to
>         minimize network hot spots (which often occur in OSPF
>         type routing) and improve network capacity efficiency.
>         Load balancing (parallel MPLS tunnels running between
>         a source-dest pair) and trunk protection also become easy.
>
>     3. QoS/VPN  - MPLS interworking with Diffserv gives you traffic
>         isolation (and hence some performance protection). Also,
>         MPLS with proper support of resource
>         reservation signaling mechanism (e.g., RSVP), you can specify
>         thE size of each MPLS 'pipe'.  With a careful traffic trunk
> analysis,
>         you may set up a set of corresponding pipes (using constraint
based
>         or explicit routing) such that you can place some application
> specific
>         (e.g., voice,  video) flows on the trunks while meeting some
>         stringent real-time specs (e.g., loss, jitters, latency).
>
> - Jay
>
> David Charlap wrote:
>
> > Mike Badil wrote:
> > >
> > > I just reading MPLS document, I have a question which I am not really
> > > clear to understand, if someone helps I will be happy.
> > >
> > > The Question is:
> > >
> > > What makes MPLS to support constraint based routing?
> >
> > The existance of LSPs makes traffic engineering easier to implement.  It
> > does not make it impossible, however.
> >
> > > If it just adding contsraint metrics to conventional routing in order
> > > to support TE.
> > > Why it is not possible without MPLS.
> >
> > Sure, it's possible.  Who said it wasn't?
> >
> > > In other word, in conventional IP routing, if we add constraint
> > > metrics, can conventional IP routing support it also?
> >
> > I think you're missing the point of MPLS.
> >
> > MPLS's purpose is not to create the ability to perform constraint-based
> > routing and traffic engineering where it was previously impossible.
> >
> > MPLS's purpose is to create a connection-oriented link layer (COLL).
> > Where forwarding decisions are made solely on the basis of a packet's
> > label, and not on any other content in the packet.
> >
> > The use of a COLL is not a requirement for traffic engineering.  It
> > simply makes it easier to implement.  With a COLL, the hard work of
> > determining the path that data packets must take can be done once, when
> > the LSP is set up.  Without a COLL, this work must be done by every
> > switch, for every data packet.
> >
> > Connection oriented link layers are not new.  ATM and Frame Relay also
> > use them.  The big thing that makes MPLS special is that it can run over
> > nearly any transport medium (ATM, FR, POS, Ethernet, etc) instead of
> > being tied to a specific layer-2 encapsulation.  Also, because it uses
> > IP for its addressing, it can work with many common routing and
> > signalling protocols (like OSPF, IS-IS, and RSVP).
> >
> > -- David
>
> --
> Jay Wang - http://math.research.bell-labs.com/~wang/wang.htm
> Bell Laboratories, Lucent Technologies     Tel: (908) 582-7223
> 600 Mountain Avenue, Room 2C-308,          wang@research.bell-labs.com
> Murray Hill, NJ 07974-2070
>
>
>