Subject: [Hubmib] RE: Question about EPON mib

From: "Lior Khermosh" <[email-masked]>
Date: Thu, 23 Mar 2006 09:16:48 +0200

Dear Mr. LiuDong,
Thanks for the question.
I believe that as the EPON MIB is an interface MIB, the relation to the
Entity MIB is defined through the relation to the interface MIB, and it
is deduced in a similar manner. The OLT has an EPON interface with N+1
virtual interfaces, one for each one of the ONUs and one for the
broadcast link. Each one has a dedicated ifIndex and considered for the
entity MIB as a separate interface. These ports at the OLT are probably
referred as separate logical entities for the entity MIB same like
bridge ports. 

The relation of the entity MIB to the interfaces MIB is defined in
RFC4133 section 2.6"

"
2.6.  Relationship to the Interfaces MIB

   The Entity MIB contains a mapping table identifying physical
   components that have 'external values' (e.g., ifIndex) associated
   with them within a given naming scope.  This table can be used to
   identify the physical location of each interface in the ifTable (RFC
   2863 [RFC2863]).  Because ifIndex values in different contexts are
   not related to one another, the interface to physical component
   associations are relative to the same logical entity within the
   agent.

   The Entity MIB also contains 'entPhysicalName' and 'entPhysicalAlias'
   objects, which approximate the semantics of the 'ifName' and
   'ifAlias' objects (respectively) from the Interfaces MIB [RFC2863],
   for all types of physical components.
"

The entAliasMappingTable defines the mapping and the
entAliasMappingIdentifier is mapped to the ifIndex as can be seen in the
examples in the entity document. 

Generally the layering model and the EPON MIB partition are described in
section 1.3 of the draft document
(http://www.ietf.org/internet-drafts/draft-ietf-hubmib-efm-epon-mib-04.t
xt) and an example is also provided in that section.

>> EPON is a point-to-multipoint system which include one OLT and a
number of ONU, one OLT includes multi PON interface 
>> which connected with multi ONU PON interface.

Although the physical model of the EPON is a point to multipoint model
the logical model is N point to point ports, like a bridge.  The point
to point emulation defined in clause 65 of the IEEE802.3ah defines the
point to point emulation layer which provides N (+1 for the broadcast)
virtual links.
>From management perspective each virtual link is modeled as a physical
interface and has a separate ifIndex.
More details can be found in the document itself, If there are more
specific items needed clarifications I would be happy to answer.

Hope it was clear enough.

Best regards,
Lior

-----Original Message-----
From: Liudong [mailto:[email-masked]] 
Sent: Wednesday, March 22, 2006 11:49 AM
To: Lior Khermosh
Subject: Question about EPON mib

Hello Mr. lior.khermosh,

What's the relationship between EPON mib and Entity Mib(RFC4133)?
How to describe such relationship that one physical OLT PON interface
connects to multiple physical ONU PON interface?
EPON is a point-to-multipoint system which include one OLT and a number
of ONU, one OLT includes multi PON interface which connected with multi
ONU PON interface.
It puzzles me how to describe such complex relationship using MIBs.

Could you give me an example about implemention of EPON mib?

Thanks a lot!		  
      
--
Best regards, 
LiuDong           mailto: [email-masked]

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