Re: [trill] DTree Questions Regarding Router Capability TLV

[Ayan Banerjee <[e-mail]>]

Please see in-line.

Thanks,
Ayan

On Mon, Dec 17, 2012 at 1:50 PM, Arnel Lim <[e-mail]> wrote:

>  I have some questions about the sending and processing of the
> TREES-RT-ID and TREES-USE-ID sub-TLV in the Router Capability TLV.  I need
> a little clarification with respect to when these sub-TLVs are sent and who
> sends them.  I’ve outlined how I interpreted parts of the Distribution Tree
> section RFC632 with respect to these sub-TLVs, but I need a little
> validation.  ****
>
> ** **
>
> Note, the quoted items are taken directly from RFC6325. ** **
>
> ** **
>
> ** **
>
> 1) Only the highest priority Rbridge needs to send out TREES-RT-ID
> sub-TLV, correct? ****
>
> “The number of trees, k, that are computed for the campus is the number
> wanted by the RBridge RB1, which has the nickname with the highest "tree
> root" priority”****
>
> ** **
>
> [Ayan] Yes, this is accurate.
>


> **
>
> 2) Rbridges will calculate the highest priority k trees if they don't
>  receive TREES-RT-ID sub-TLV.  This implies it's *NOT* *mandatory* for
> highest priority Rbridge to send TREES-RT-ID sub-TLV, correct?****
>
> “If RB1 does not specify the specific distribution tree roots as described
> below, then the k highest priority trees are the trees that will be
> computed by all RBridges.”****
>
> ** **
>
>   [Ayan] Yes, this is accurate.
>
> 3) ALL Rbridges, RB2, that ingress native traffic *MUST* send
> TREES-USE-ID sub-TLV, correct?   This is required for RPF check used by
> adjacent RBridges.****
>
> “each RBridge RB2 MUST announce which trees RB2 may choose when RB2
> ingresses a multi-destination packet.”****
>
> [Ayan] No, this is not accurate. If ingress nodes use this TLV, it may
> help other nodes to be more strict in accepting packets from the relevant
> multi-destination trees. If it does not send out this TLV, then it implies
> that a node may use all multi-destination trees.
>
> 4) Transit-only RBridges do *NOT* need to send TREES-USE-ID sub-TLV,
> correct?  Since TREES-USE-ID indicates what trees a RBridge may use for
> ingressing native traffic, Transit-only RBridges have nothing to advertise.
> ****
>
> [Ayan] See answer to (3) above.
>
> ** **
>
> 5) Ingress RBridges, RB2, can specify, via user config, a set of j trees
> to use.   If NO trees in the set of j trees intersect with the k highest
> priority  trees advertised by the Rbridge with highest root priority, NONE
> of the  j trees are advertised.  Ingress RBridges, RB2, will then advertise
> the k  highest priority trees in the TREES-USE-ID sub-TLV. Correct?****
>
> OR, does RB2 advertise whatever it wishes, and the RBridge receiving the
> LSP examine the intersection of j with k?****
>
> [Ayan] It is the latter - others make use with the TREES-USE-ID TLV. What
> a local nodes announces with user configured "j" trees is a local decision.
>
> If no set of j trees is explicitly configured, will RB2 advertise the k
> highest priority trees in the TREES-USE-ID sub-TLV, or none at all.  What’s
> not clear is if in the special case of j==0, do we still have to include
> the sub-TLV in the LSP?  I would think the neighboring RBridge can assume
> if the TREES-USE-ID sub-TLV is not present, that means j==0 and RB2 will
> use the k highest priority trees.   Seems explicitily advertisine the k
> highest trees may be the “safe” thing to do for interoperability, but is it
> the “right” thing to do?****
>
> [Ayan] Sure a node can announce the "K" trees, but that is also implicit.
>

Thanks,
Ayan


> “The information to determine which trees RB2 might choose is included in
> RB2’s LSP. Similarly to how the highest priority RBridge RB1 specifies the
> k trees that will be computed by all RBridges, RB2 specifies a number j,
> which is the total number of different trees RB2 might specify, and the
> specific trees RB2 might specify are a combination of specified trees and
> trees selected from highest priority trees. If RB2 specifies any trees that
> are not in the k trees as specified by RB1, they are ignored.****
>
> ** **
>
> The j potential ingress trees for RB2 are the ones with nicknames that RB2
> has explicitly specified in "specified ingress tree nicknames" (and that
> are included in the k campus-wide trees selected by highest priority
> RBridge RB1), with the remainder (up to the maximum of {j,k}) being the
> highest priority of the k campus-wide trees.”****
>
> ** **
>
> When the RFC refers to *RB2’s LSP* it is referring to the TREES-US-ID
> sub-TLV, correct?****
>
> The j potential ingress trees this section talks about would be manually
> configured by the user, correct?****
>
> ** **
>
> If no j trees are specified, does RB2 default to sending out the k trees
> in the TREES-USE-ID sub-TLV, an empty TREES-USE-ID sub-TLV, or RB2 does not
> send any TREES-USE-ID sub-TLV at all?****
>
> ** **
>
> If j >= k and no tree in j intersects k, all j trees are ignored.  Does
> this imply neighbors should not expect dTree traffic from RB2? ****
>
> ** **
>
> ------------------------------
> DISCLAIMER:
> This e-mail and any attachments to it may contain confidential and
> proprietary material and is solely for the use of the intended recipient.
> Any review, use, disclosure, distribution or copying of this transmittal is
> prohibited except by or on behalf of the intended recipient. If you have
> received this transmittal in error, please notify the sender and destroy
> this e-mail and any attachments and all copies, whether electronic or
> printed.
>
> _______________________________________________
> trill mailing list
> [e-mail]
> https://www.ietf.org/mailman/listinfo/trill
>
>