The MPLS WG Archive

[Abhijit Gadgil <gabhijit@ee.iitb.ac.in>]

MPLS does require layer 3 routing information. It works together with
Layer 3 routing information like OSPF / BGP etc. However the advantage of
MPLS is in terms of being able to label switch after it has formed the
LSPs. This is useful in case of hardware that cannot look into IP header
like ATM switches. Another advantage of MPLS is in terms of creating
explicitely routed label switched paths, which is useful in Traffic
Engineering. The original motivation for MPLS of being able to outperform
IP lookup is not the motivation for MPLS these days. Another advantage of
MPLS is its better than IP over ATM. Thus the advantages of MPLS can be
listed as follows.
1. Making use of network layer routing to create label switched paths.
2. No need to maintain 2 networks as in IP over ATM case.
3. Alleviating N^2 mesh problem common with ATM switches

hope that helps

-abhijit

On Fri, 13 Apr 2001, Rajesh P Jain wrote:

 >"Hello",
 >                        Thanks for the response.
 >
 >                        Well, if it requires L3 Routing table to build up the Label information, then what is the advantage of MPLS??? Well, Anyhow, it will require the building of L3 Routing Table (May be through RIP/OSPF/BGP etc), then Lable info can be formed by using only L3. So, Anyhow, MPLS is dependent on L3, please explain me what is the advantage of using MPLS (in terms of efficiency and speed switching of the packets).
 >
 >With Regards
 >                    Rajesh P Jain
 >  ----- Original Message -----
 >  From: Bharti Batra
 >  To: Rajesh P Jain ; mpls@UU.NET
 >  Sent: Friday, April 13, 2001 1:09 PM
 >  Subject: Re: Does MPLS Require L3 Routing Table ?
 >
 >
 >  Hi !
 >
 >  Yes. LDP needs IP routing table to find out the route towards the egress router to setup the LSP. LDP sends the LSP setup request message along this path.
 >
 >  Regds,
 >  Bharti
 >    ----- Original Message -----
 >    From: Rajesh P Jain
 >    To: mpls@UU.NET
 >    Sent: Friday, April 13, 2001 12:52 PM
 >    Subject: Does MPLS Require L3 Routing Table ?
 >
 >
 >    "Hello", List,
 >                        Well, I am very new to Jthe MPLS domain. I
 >just
wanted to check out whether MPLS domain neccesarily require the L3 Routing
Table (Maybe IP Routing Table) to build up it's label (using the LDP
Protocol). Or the LDP will take care of building the label information
automatically without the L3 Routing information?
 >
 >    TIA
 >            Rajesh P Jain
 >