[rbridge] dist tree parallel links - asymetric

[Ayan Banerjee]

Jeff,

In TRILL 3-way handshake is mandatory for P2P links. Hence, each node will
get an unique extended circuit identifier after adjacency formation. On LAN
links, the source mac can be used an identifier for uniqueness of each link.

I believe that P2P links are preferred over LAN links. Among the set, in the
event there are multiple "identifiers" then the highest (or lowest - I
remember that there was some discussion on the list about highest/lowest, do
not recall what we ended up with) one will be chosen for the tree.

Thanks,
Ayan

On 6/22/09 8:55 AM, "jeff pickering" <jpickering at nc.rr.com> wrote:

> 
> I have a distribution tree parallel links question I was hoping someone
> could clarify
> for me.
> 
> Let's say you have 2 RBs downstream from the root, with parallel links
> between them.
> 
> RB-A has cost 10 on link 1, cost 20 on link 2.
> RB-B has cost 20 on link 1, cost 10 on link 2.
> 
> Lets say RB-B is downstream from RB-A. When computing its paths, RB-A
> will clearly
> use link 1. Whether it shows 1 or 2 links in its LSPs is irrelevant,
> RB-B still needs to know
> somehow to choose its adjacency over link 1 for its path to the root.
> But in the asymetric cost
> case, I dont see how its can do this. Is there something new in either
> the LSP or hello that
> would resolve this?
> 
> Or should RB-B use its lower cost and if so how does the RPF issue get
> addressed?
> 
> Thanks to anyone who can enlighten me.
> 
> Jeff
> 
> 
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