The MPLS WG Archive

[brijesh.kumar@att.net]

I don't know why some people will not accept that MPLS 
is mainly a connection oriented technology. The main 
characteristic of a Connection Oriented service is the 
long term association required between two end points. 
The process of how such association is established is 
not important. It is also not important if the 
connection doesn't begin or end at some hosts (why we 
need to use ISDN or X.25 definitions of connections?). 

It is quite obvious that there is very clearly 
established permanent association between two end points 
of LSPs. All LSRs also maintain the necessary states 
about particular paths (similar to circuit switched 
network). 

>From all this, MPLS clearly is the connection oriented 
layer at layer 2. Of course, I have also seen comments 
that MPLS doesn't fit in ISO model. Oh Really, !.
 

Cheers,

--brijesh
Corona Networks
> OK, here we go again....
> 
> To its nature MPLS is not "connection oriented"! I also depends quite a
> bit on the definition of "connection oriented", but if we e.g. let an
> ISDN
> phone call be the model of a connection oriented technology, then you 
> immediately see that MPLS misses the most important part of what a 
> connection oriented technology is all about.
> ISDN is separated into two parts "call control" and "connection
> handling",
> together they form the connection orientation.
> 
> So the "call control" handle e-2-2 compatibility and ability to take the 
> call. This does not exist in MPLS. The call control also OK's the set
> up of the call and is once it is established dependent of the e-2-e 
> connectivity, if the connectivity is broken the call is released.
> Nothing
> of this is present in MPLS.
> 
> Sometimes one hear that MPLS is connection oriented because there is 
> a mapping from node to node over the network, strictly this is not true,
> the only thing that is mapped incoming label to outgoing label and
> interface.
> The rest is routing in the standard IP connections way.
> 
> As for the arguments that "most of the" LSP setup is connection
> oriented,
> usually meaning end-to-end (which really is edge-to-edge, there is not 
> much idea to establish a connection edge-to-edge. But even so
> 
> LDP DU independent liberal is not connection oriented
> LDP DU independent conservative is not connection oriented
> LDP DU ordered liberal is not connection oriented
> LDP DU ordered conservative is not connection oriented
> 
> LDP DoD independent liberal is not connection oriented
> LDP DoD independent conservative is not connection oriented
> LDP DoD ordered liberal is not connection oriented
> LDP DoD ordered conservative could at best emulate part of a connection
>         oriented technology (signaling)
> 
> RSV-TE mostly strictly follows IP routing and is not connection oriented
>        and if there are explicit routes it falls into the same category
>        as LDP DoD ordered conservative
> 
> We are left with a technology where it is required to have an
> MPLS-external
> application that do the call control part of connection orientation. Why
> we would like to do that is beyond me, as we loses all the benefits of
> the
> IP and MPLS combination.
> 
> /Loa
> 
> -- 
> Loa Andersson
> Chief Architect,
> Utfors Research, Architecture and Future Lab (URAX)
> Utfors AB
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