The MPLS WG Archive

[Atsushi Iwata <iwata@ccm.CL.nec.co.jp>]

Ramanjaneyulu

>>WHY use MPLS?
>~~~~~~~~~~~~~
>  MPLS forwarding and LSP set up  is ATM like technology , but there r lot
>of differences between ATM and MPLS technologies. The following are the
>problem with ATM.
>
>  --- Scalability issue : In MPLS we can allow any number of Hierarchies,
>where as in ATM only 2 level hierarchy allowed. More over ATM VCI is 5 -
>bit , this becomes constraint in terms of scalability.

I think that this includes a wrong statement.

In MPLS, the number of hierarchies depends on the routing protocol that you
use. Normally you can have upto 4 level hierarchies, 2 level OSPF and 2
level BGP (if you use BGP confederation).

In ATM, you can use 104 level hierarhy in theory if you use PNNI in
bit-by-bit hierachy assignment. However, 4 or 5 level hierarhy would be
enough in the current ATM network, though.

Thanks

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Atsushi Iwata
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