Doubt in IEEE 802.1ag (Connectivity Fault Management)

Unanswered Question
Mar 12th, 2007

Hi,

Going through the Draft 8 of IEEE 802.1ag, I came across Down MEP and Up MEP. The draft defines Up MEP as "A MEP residing in a Bridge that transmits CFM PDUs and receives them from, the direction of the Bridge Relay Entity" and Down MEP as "A MEP residing in a Bridge that transmits CFM PDUs and receives them from, the direction of the LAN". Can somebody explain?

What is the significance and difference between them?

On what basis should a MEP be configured as Up or Down.

Any replies would be useful.

Thank you.

Sriram K

I have this problem too.
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attrgautam Mon, 03/12/2007 - 20:58

Didnt get a chance to read the draft but I am assuming that as per cisco jargon you are referring to MEP and MIP. MEP process CFM messages from UNI or from a higher mgmt zone [and drop them if otherwise] while MIP transparently pass through the frames. Typically MIP will be the link connecting to the NPE from the UPE in the same CFM domain. I am assuming this is what it is (until I probably read the draft).

http://www.cisco.com/univercd/cc/td/doc/product/metro/me3400/12225seg/3400scg/swoam.htm

Or probably u r referring to the MEP Up and MEP down SNMP traps generated ?

ksriram29 Mon, 03/12/2007 - 21:49

Thanks Gautam. I am referring to MEP and MIP and not SNMP traps. I will go through the link and get back if there are any doubts.

Regards,

Sriram K

Francois Tallet Mon, 03/12/2007 - 22:19

The term up/down is related to the direction the meps are facing in the typical "baggy pant" IEEE diagram representing a bridge.

Downward meps are below the STP blocking logic, facing the wire. That means that even when STP is blocking a port, a downward mep can still send and receive traffic. It is useful to monitor the availability of an alternate path (if your primary path fails, you know which alternate path still has connectivity to some other meps you're monitoring for instance).

Upward meps are facing the switching fabric.

HTH,

Francois

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