Subject: Terminology

From: Robert Raszuk <[email-masked]>
Date: Mon, 09 Oct 2000 17:50:00 -0700

While talking to a lot of people about mpls applications (or even
watching this alias or drafts :) I see a lot of confusion about calling
different kinds of label switched paths as LSPs. The problem with this
is that all of them have very different characteristics - based on very
different control planes used to established them - with only one common
part (in the first two at least) imposed label shim(s) into ip unicast
packet.

I think about a year ago Lou presented clear separation:

* prefix based LSPs - those established based on the routes (carried by
IGPs), MP-BGP, PIM etc ...
* tunnel based LSPs - those established by extensions to RSVP or by
CR-LDP.

Now we also cold add third type:

* optical LSPs - established by MPLambda based control plane in optical
domains

I personally hate acronyms, but maybe to avoid any further confusion we
could append one letter to the LSP itself and start using P-LSP, T-LSPs
or O-LSPs to clearly indicate what we are talking about ? If somebody
has better suggestions feel free to propose. I just don't know anymore
what one means by term "mpls tunnel".

R.

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From: Robert Raszuk <[email-masked]>
Date: Mon, 09 Oct 2000 18:03:16 -0700

Grenville,

> on what basis an LSP is established
> doesn't really change how it behaves

From operational expereince with them for a decent time I see that it
really does change how it behavies depending on how it got setup/build.
Of course in steady state both are fine and doing the same, but when
things start to melt or break that is when you see big differences.

R.

> Grenville Armitage wrote:
> 
> Robert Raszuk wrote:
>         [..]
> > I just don't know anymore
> generically an LSP is always a tunnel of sorts, since the
> IP header of the MPLS payload is thereby always hidden from
> the intermediate LSR hops.  on what basis an LSP is established
> doesn't really change how it behaves as a form of 'tunnel'
> in the data path....
> 
> gja

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From: Grenville Armitage <[email-masked]>
Date: Mon, 09 Oct 2000 10:51:22 -0700

robert,

aside from the (lack of)ethics associated with reposting
private email back to the list, please at least do me the
courtesy of taking my comments in context. quite clearly
i made a restricted observation - viz. when the LSPs are up
they essentially function as tunnels since the inside
packets are isolated from the intermediate LSRs' forwarding
machinery.

gja

-- 
________________________________________________________________________
Grenville Armitage                    http://members.home.net/garmitage/
Bell Labs Research Silicon Valley