Re: [Mpls-interop] Local and Remote

"Sprecher, Nurit (NSN - IL/Hod HaSharon)" <nurit.sprecher@nsn.com> Wed, 06 May 2009 12:58 UTC

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From: "Sprecher, Nurit (NSN - IL/Hod HaSharon)" <nurit.sprecher@nsn.com>
To: Adrian Farrel <adrian@olddog.co.uk>, mpls-interop@ietf.org
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Subject: Re: [Mpls-interop] Local and Remote
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Hi,

Thanks for the great clarification.

I am sorry for bothering but I still have some questions:

*         We have a requirement in the document for "Remote Defect
Indication" and it specifies that "The MPLS-TP OAM toolset MUST provide
a function to enable an End Point to notify its associated End Point of
the detection of a fault or defect that it detects on a PW, LSP or
Section between them." I.e. in the requirement refers to remote as to
the associated endpoint at the same layer!

*         I would like to refer to the last paragraph in your e-mail: ""
When a server layer provides a connection that is used as a link in the
client layer, a server layer fault (that is remote in the server layer)
may be reported to the client layer as a fault in the client layer link
(that is local in the client layer)...." Assuming that we have an LSP
that traversed nodes A-B-C-D-E-F-G and we have a fault in the link
between D and E. according to the above the server layer needs to notify
the client layer. Is it to the client layer in nodes D and E or to the
endpoints of the client layers, i.e. nodes A and G? If it is node D and
E (this is local) they need now to notify nodes A and G, but according
to the requirement document and to the framework they may be MIPs of the
LSPs but they cannot initiate OAM messages. Therefore, it seems that the
endpoint of the server layer needs to notify the endpoint of the client
layers of the fault (remote). And IMO we need to be clear about the
requirement. And also to extend the definition in the first bullet for
remote (not necessarily endpoint). 

*         Assuming that the failure is in the first (server) link. As a
result we have loss of continuity in the LSPs that transmit over this
failed link and in the PWs that are attached to these LSPs. As I
understand from your definition, as these fault are detected by the
endpoint (to which the link is attached), all these faults are
considered locals!. Is there still a requirement to distinguish between
these failures? Note that all of these are now local. 

I'll appreciate your further clarification.

Best regards,

Nurit

 

-----Original Message-----
From: mpls-interop-bounces@ietf.org
[mailto:mpls-interop-bounces@ietf.org] On Behalf Of ext Adrian Farrel
Sent: Wednesday, May 06, 2009 3:16 PM
To: mpls-interop@ietf.org
Subject: [Mpls-interop] Local and Remote

 

I know that Malcolm and Huub are going to work on the definition of
local 

and remote.

 

Huub usefully typed during the meeting yesterday that "remote" might be 

better stated as "non-local."

 

Watching some emails this morning, I wonder whether part of the
confusion 

arises from

- where the fault is detected

- where the fault exists

 

A node can (IMHO) only be detected locally. That is local to the point
of 

detection.

 

A fault may be reported (to the management plane) from the node of
detection 

(a local report), or may be signaled to another node (through the OAM or


control plane) and reported (to the management plane) from that other
node 

(a remote report).

 

The fault that is detected may be in the detecting node, or in a
resource 

directly connected to that node (such as a link). This is a local fault.

 

But the fault may also exist in a node or resource that is not local to
the 

detecting node. This is a remote fault.

 

If an LSP continuity check fails, the fault is detected by an end point 

(local detection), but the fault might be somewhere out in the network 

(remote fault).

 

When a server layer provides a connection that is used as a link in the 

client layer, a server layer fault (that is remote in the server layer)
may 

be reported to the client layer as a fault in the client layer link
(that is 

local in the client layer). The client layer does not know about the
route 

or resources used in the server layer (we MUST assume clean layer 

separation) so the client layer does not need to know about the location
of 

the server layer remote fault. If the client layer requests the server
layer 

to repair the client layer link (i.e. to repair the server layer
connection) 

the server layer may need to consider the location of the server layer 

fault.

 

Am I wrong?

Is this really so complicated?

 

Thanks,

Adrian 

 

 

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