Subject: Re:Some queries

From: Ramanjaneyulu Y T <[email-masked]>
Date: Sat, 16 Dec 2000 21:33:09 +0530 (IST)

>At a recent discussion with my MS class students, i was discussing MPLS
>and related issues. The discussion went into a complete confusion when we
>got stuck at the very question 

>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.

 -- Different environment : IP and ATM is designed for different tasks. IP
and ATM are based on completly different protocol architectures and they
have their own protocols for signalling and routing and resource
allocation schemes.

    So complexity arises when operating between two different technology.

 Where as MPLS is independent of n/w layer. Just it provides support of
forwarding , where as routing protocols and resource allocation schemes
are dependent  on n/w layer.So irrespective network protocol and link
layer protocol , MPLS can be used for achieving fast forwarding in IP
network without changing routing protocols and resource allocation
schemes.                            

>Is it only because of the fact that the efficient swapping mechanism,
>that MPLS is considered good. What about already accepted switching techs
>like ATMs, incase they are integrated with IPv6 networks for better
>services like QoS through flow labels?
>would anyone be kind enough to clarify?

Regards
YTR

---

From: "Yi Chu" <[email-masked]>
Date: Mon, 18 Dec 2000 09:10:52 -0500

Just to correct the statement on ATM.  ATM label has two levels: VP and VC.
The VPI is 12 bits with NNI format and 8 bits with UNI format.  VCI is
always 16 bits.  Some vendors may not implement the full 16-bit VCI, but
this should not be used to argue against ATM scalability.

Yi Chu
Winstar Communications

-----Original Message-----
From:	[email-masked] [mailto:[email-masked]] On Behalf Of
Ramanjaneyulu Y T
Sent:	Saturday, December 16, 2000 11:03 AM
To:	Faisal S. Naik
Cc:	mpls uunet
Subject:	Re:Some queries

~~~~~~~~~~~~~

Regards
YTR