[rbridge] query regd. TRILL scenario

[Donald Eastlake]

Hi Joydeb,

On Tue, Jan 3, 2012 at 1:51 AM, Joydeb Roy <joydeb at gmail.com> wrote:
> Hi Donald,
>
> Thanks a lot for your reply. The understanding is indeed much better now.
> Just another query though regarding the AVF part you mentioned in your
> comments -
>
> Now, I understand that the default the DRB will carry all the traffic to and
> fro the end-user. But when the DRB does decide to distribute the traffic to
> other rbridges then what propels it to make that decision?
>
> The last sentence of the Section 2.2 from the RFC 6439 states -
>
> "How the DRB decides what other RBridges on the link, if any, to appoint
> forwarder for which VLANs is beyond the scope of this document."
>
> So, is there any other standard document that I can refer to? Is the
> behavior totally dynamic in nature e.g. the DRB takes such decision through
> the usage of some algorithm? Or should it be configurable, so that the
> Network Admin takes the last call?

I kind of think of how the DRB decides what forwarders to appoint as
an area where implementors can display their individual brilliance :-)

Seriously, there are a lot of factors that could be used in such
decisions. I don't see how it could be standardized. But you might
look at draft-zhang-trill-vlan-assign-02.txt and at Section 10.2 of
draft-eastlake-trill-rbridge-clear-correct-02.txt.

By the way, in connection with your previous question, you might look
at Section 6 of draft-eastlake-trill-rbridge-clear-correct-02.txt.

Thanks,
Donald
=============================
 Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
 155 Beaver Street, Milford, MA 01757 USA
 d3e3e3 at gmail.com

> Thank you.
> Best regards
> Joy
>
> On Mon, Jan 2, 2012 at 7:51 PM, Donald Eastlake <d3e3e3 at gmail.com> wrote:
>>
>> Hi Joybed,
>>
>> On Mon, Jan 2, 2012 at 5:06 AM, Joydeb Roy <joydeb at gmail.com> wrote:
>> > Hi Authors,
>> >
>> > Please let me know if my understanding is proper in the below case. If
>> > yes,
>> > then please clarify the doubts and if no, then please correct wherever
>> > applicable.
>> >
>> > Generally, RBridges learn about end stations on access ports and they
>> > communicate with each other to form adjacency through trunk ports.  But
>> > if
>> > we consider the following diagram –
>>
>> TRILL tries to be zero/minimum configuration. So by default, RBridge
>> ports are universal ports that can handle both native and TRILL Data
>> frames. RBridge access and trunk ports are ports that have been
>> configured to restrict them. While this is commonly a good idea, it is
>> not necessary for correct operation.
>>
>> In any case, TRILL Hellos are always sent out RBridge ports unless the
>> port is disabled or configured as point-to-point (in which case
>> point-to-point Hellos get sent on them).
>>
>> >                                   +---------+
>> > +---------+                       |   RB1   |
>> > |   End   |        +-----+ ------ +---------+
>> > |         | ------ | Hub |
>> > | Station |        +-----+ ------ +---------+
>> > +---------+                       |   RB2   |
>> >                                   +---------+
>> >
>> > How do the involved ports in RB1 and RB2 behave in this case? Do both of
>> > them manage to learn about the End Station and one of them becomes the
>> > DRB
>> > based upon the configured priorities? Also, do they manage to form an
>> > adjacency between them? If so, then how do they manage so in spite of
>> > the
>> > ports being designated as access?
>>
>> As above, TRILL Hellos are still sent out the ports of RB1 & RB2
>> whether or not the "access port" configuration bit has been turned on
>> for those ports. So they form an adjacency and one is elected DRB on
>> the link. By default, the DRB will handle all the native traffic
>> to/from the End Station. The other RBridge will see all that traffic
>> but will throw it away because by default it is not the Appointed
>> Forwarder for any VLAN on the link. However, the DRB can assign some
>> or all VLANs to the non-DRB RBridge as Appointed Forwarder.
>>
>> > Thank you.
>> >
>> > Best regards
>> > Joy
>>
>> Hope the above helps.
>>
>> Thanks,
>> Donald
>> =============================
>>  Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
>>  155 Beaver Street, Milford, MA 01757 USA
>>  d3e3e3 at gmail.com
>
>