Subject: Re: [rbridge] TRILL MIB rbridgeUniFibTable

From: Anil Rijhsinghani <[email-masked]>
Date: Tue, 8 Nov 2011 13:18:07 -0500 (EST)

Mahesh,

I did not consider ECMP being used this way, however in discussing
further with Donald Eastlake – his comment is attached below – he
indicates it could happen, whether intentionally or not.

To accommodate this, I'll add rbridgeFibMacAddress to the index to make
it unique. (I considered taking out rbridgeFibPort from the index, but
that could make it non-unique if the same next-hop were attached to an
RBridge via more than one port.)

Regards,
Anil

-----
On Nov 7, 2011, at 7:50 PM, Donald Eastlake wrote:

It seems to me that this is possible.

It will not usually happen as there will be a pseudo-node and there
will be only one path out the port to the pseudo-node... However, the
DRB can suppress the pseudo-node. The standard says that it SHOULD do
this if there is only one adjacency, which is obviously no problem.
But if there are 2 or more adjacencies out the port and the DRB
suppresses the pseudo-node, then it seems to me that there can indeed
be more than one ECMP path out a port to a particular destination.
This will work fine as the frames will be unicast to the intended next
hop...

If the link is an Ethernet bridged LAN, this could cause more traffic
on the port than on some other port which also has an ECMP path to the
destination, but only one such path, perhaps causing some congestion.
On the other hand, if the link is something exotic like a switching
fabric link, there might be little interference between the unicast
traffic out the port to different ECMP adjacencies on the link...

Thanks,
Donald

-----
On Nov 7, 2011, at 5:00 PM, Mahesh Akula wrote:

Dear Authors,

As per the draft-ietf-trill-rbridge-mib-04, indices for the 
rbridgeUniFibTable has been defined as combination of rbridgeFibNickname 
and rbridgeFibPort.

In an ECMP scenario, on a Shared LAN link, there can be reachability to 
the Egress Rbridge over two different nexthop Rbridges connected to the 
same rbridge port right?  In this case, there will be more than one 
entry with the same rbridgeFibNickname and rbridgeFibPort but with 
different nexthop Rbridge nickname.

Don't we need to include the nexthop rbridge name also part of the 
indices for this table? Or Am I missing something here?

Regards,
Mahesh
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---

From: Mahesh Akula <[email-masked]>
Date: Tue, 8 Nov 2011 10:35:06 -0800

Hi Anil,

I'm curious, if all the three objects in the table has MAX-ACCESS set to
not-accessible, (as it will be the case if all 3 objects are part of the
index),  how can any operations be performed on the table?

Regards,
Mahesh

On Tue, Nov 8, 2011 at 10:18 AM, Anil Rijhsinghani <[email-masked]> wrote:

> same rbridge port right?  In this case, there will be more than one entry
> with the same rbridgeFibNickname and rbridgeFibPort but with different
> nexthop Rbridge nickname.
>
> Don't we need to include the nexthop rbridge name also part of the indices
> for this table? Or Am I missing something here?
>
> Regards,
> Mahesh