The MPLS WG Archive

[David Escobar <c-david.escobar@wcom.com>]

Can you provide "guaranteed QoS" in MPLS?
Note: I make a difference between "guaranteed QoS" and "differentiated QoS".
"Guaranteed QoS" means that you can guarantee parameters like Packet Loss
Ratio, Packet transfer Delay, Packet Delay Variation in a given
transmission. "Differentiated QoS" means that you can only define packet
priority. You can only assign a priority to some packets so they are treated
better by routers (i.e. dropped last, forwarded faster, etc) but you still
can not guarantee any QoS.
----- Original Message -----
From: "Loa Andersson" <loa.andersson@utfors.se>
To: "David Allan" <dallan@nortelnetworks.com>
Cc: "Ding Aijun" <dingaijun@sina.com>; "Hongwei"
<hongwei.zhou@elec.qmul.ac.uk>; "David Escobar" <c-david.escobar@wcom.com>;
"mpls" <mpls@UU.NET>
Sent: Tuesday, September 04, 2001 11:35 AM
Subject: Re: Control and Forwarding functions


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)
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