Re: [Time] MEP and maintenance domain boundary

Huub van Helvoort <> Mon, 30 June 2014 12:58 UTC

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Date: Mon, 30 Jun 2014 14:58:21 +0200
From: Huub van Helvoort <>
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Subject: Re: [Time] MEP and maintenance domain boundary
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Hello Qin,

You wrote:

Hi, Greg:

Thanks for your review to problem statement draft." rel="nofollow">

Section 4 gives an architecture overview of management plane OAM,

You comment on the following quoted sentence

“MEP is a maintenance functional entity that is implemented into

   network entity at the maintenance domain boundary 

as “Not necessarily, e.g. MEP at Level < 7 in Ethernet Service OAM as CFM or Y.1731.

Unfortunately MPLS-TP has only one MEL, fixed at "7".

Are you saying MEP can be placed either at the maintenance domain boundary or within maintenance domain?

First of all you have to correct the expansion of MEP and MIP:
MEP = Maintenance entity End Point
MIP = Maintenance entity Intermediate Point.
MEPs and MIPs that belong to the same Maintenance Entity (ME) are not
aware of any MEPs or MIPs outside the ME they belong to.

A Maintenance Entity can be any path, tunnel or section in the
So it can exist between domain boundaries (NNIs) but also inside
a domain, or across multiple domains (end-to-end ME).

In section 4 I notice:
   MEP is a maintenance functional entity that is implemented
   into a Network Element either at the maintenance domain boundary or
   in the maintenance domain and can generate, send and receive OAM

What is the difference between generate and send OAM packets?

   MIP is a maintenance functional entity that is implemented
   into a Network Element in the maintenance domain and can forward OAM

A MIP can also respond to OAM messages sent by the source MEP.

   Either MEP or MIP may be at different layer and use various
   different encapsulating protocols.

This is confusing, as I explained above.
MEPs and MIPs can exist in different layers/technologies.
However in the same layer ME MIPs cannot exist without MEPs.
MEPs and MIPs in the same ME in a layer are not aware of 
MEPs and MIPs other ME in the same layer, nor in other layers.

Best regards, Huub.