Subject: RE: MPLS and Tag Switching

From: Nhat Thanh Hoang <[email-masked]>
Date: Thu, 27 Jan 2000 12:04:34 +0100

Hi, David

Let me try to explain briefly: The MPLS technique is based on label
switching i.e. on each LSR (MPLS enable router), it makes its routing
decision on the incoming label of the packet. In addition, MPLS encompasses
a lot of other features. Actually there is no difference between Label
Switching and Tag Swithing, except the name of tag instead of label in
Cisco's MPLS enabled Router which calls Tag Switching. Tag Switching is
implementation (approach) of MPLS techinque.
I hope it would help, otherwise the other experts will elucidate for you.

regards,

Nhat Thanh

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Can someone help me understanding the major
differences between Tag Switching and MPLS.
The reason for this question is that Cisco says that
there is no diference between both technologies.

Regards,
Dave
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From: "Aijaz Pathan" <[email-masked]>
Date: Thu, 27 Jan 2000 09:34:42 -0800

David,

As Nhat correctly pointed out, there are additional features supported by
MPLS.

The label format in the data plane is exactly similar for both tag switching
and MPLS, and hence the
compliance by Cisco.

However, there might be another angle to it. Cisco IOS supports TDP (Tag
Distribution Protocol) as the control
protocol for distributing labels, which they say will be replaced by
standard LDP and RSVP with extensions. So I think
"Tag" implies TDP as control and MPLS implies LDP for most people (Although
it should not).

BTW, Can anyone from Cisco confirm this, and also which versions of the
Cisco Router IOS supports TDP vs. LDP vs. RSVP?
That would be of great help to atleast the 3 of us.

Thanks

-Aijaz
----- Original Message -----
From: Nhat Thanh Hoang <[email-masked]>
To: 'David Curren' <[email-masked]>; <[email-masked]>
Sent: Thursday, January 27, 2000 3:04 AM
Subject: RE: MPLS and Tag Switching

Hi, David

regards,

Nhat Thanh

Regards,
Dave

---

From: Rene Tio <[email-masked]>
Date: Thu, 27 Jan 2000 10:39:17 -0800

On Thu, Jan 27, 2000 at 09:34:42AM -0800, Aijaz Pathan wrote:
[...]
> "Tag" implies TDP as control and MPLS implies LDP for most people (Although

From what I understand, before a certain release if you configure
"tag-switching" on a cisco box you are configuring the cisco-proprietary tag
switching (i.e., TDP, etc.)  After certain releases, "tag-switching" will
configure MPLS (i.e., LDP.)  This provides for easy migration (assuming
cisco will auto-detect between LDP and TDP so you won't have to flash-cut
the entire network.)

What those releases are only a cisco release wizard will be able to tell.

R.