[rbridge] Compromise proposal---allowing tradeoff between computation and optimality of delivery

[Sanjay Sane (sanjays)]

I would also support a minimum or a default of 2 trees. Thus, at
minimum, we can assure multicast-multipathing (even if it's 2-way) in a
TRILL network. 

Sanjay

-----Original Message-----
From: rbridge-bounces at postel.org [mailto:rbridge-bounces at postel.org] On
Behalf Of Eastlake III Donald-LDE008
Sent: Saturday, November 04, 2006 2:10 PM
To: rbridge at postel.org
Subject: Re: [rbridge] Compromise proposal---allowing tradeoff between
computation and optimality of delivery

I really can't see why the minimum should be one. In an network where
Rbridge trees make any difference you have at least two Rbridges so I
can't see why you wouldn't, at a minimum, have two trees. I think we
should just prohibit Rbridges that claim to be able to support only one
tree.

Donald

-----Original Message-----
From: rbridge-bounces at postel.org [mailto:rbridge-bounces at postel.org] On
Behalf Of Radia Perlman
Sent: Thursday, November 02, 2006 2:20 PM
To: Sanjay Sane (sanjays)
Cc: rbridge at postel.org
Subject: Re: [rbridge] Compromise proposal---allowing tradeoff between
com putation and optimality of delivery

Warning---half-baked idea at the end of this message (my own---see
"***")


Sanjay Sane (sanjays) wrote:

>
>So, the TLV inside rbridge LSP could contain 2 things
>1 -- "my priority for being a tree root is x". 
>2 -- "I can support n trees"
>
>If both of these are absent, we could choose 1 tree, and the rbridge 
>with lowest MAC address is the root of that single tree.
>
>-Sanjay
>
Right. I'm a bit nervous about some random RBridge that can only support
one tree, or that just leaves the TLV out, from going up and down. We
have to make sure it's not unstable.

Suppose the nickname of the RBridge with highest priority for being root
is 24.
Suppose ingress RBridge R1 doesn't notice that wimpy RBridge R5 (that
can only support one tree) has joined the net, and R1 selects "79" as
the tree .

I guess we should say that if you see a specified tree that shouldn't be
legal, you drop the packet, right?

***An alternative is to continue forwarding it along the 79-tree and
hey, if R5 is on the path, it will drop the packet and only nodes
downstream from R5 will suffer. We could even do complicated things like
say that you can calculate trees beyond R5's capabilities by considering
links out of R5 to be infinity. That way a wimpy RBridge can be a leaf,
and going up and down won't affect existing trees.

Radia

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