Subject: [rbridge] Ridirect, default VLAN ID, node ID and more

From: dahmna at gmail.com (Masanori Takashima)
Date: Wed, 19 Jul 2006 12:21:53 -0400

Hi,

I have comments and a question.

(1) Redirect situation
We may have a situation that we want to redirect frames.

  h1--R1----b1----R2
                |      (DR)
               h2

Suppose
 - h2 sends a frame to h1,
 - and h1 is learned by R1 already,
 - and R2 is DR on the shared link on that b1 and h2 are located,

apparently, the frame h2 to h1 goes through h2->b1->R2->b1->R1->h1,
although h2->b1->R1->h1 is a better path.

(2) default VLAN ID
Since all endnode information are carried by per VLAN instance of
routing protocol, all RBridge need to know what VLAN ID is assinged on
an interface defaultly if we keep to consider "less configuration". (I
don't know if I can say "zero configuration" or not.) So we need to
have a default VLAN ID that all interfaces of RBridge are defaultly
assigned.

(3) Node ID of shared link
Node ID of link state information is suggested in
"draft-perlman-trill-rbridge-protocol-00.txt" as follows,
2.2. Ingress Rbridge Tree Calculation
     .......               If the "node" is a pseudonode, i.e., a shared link,
   then one RBridge, say R1, on the link, is elected Designated RBridge,
   and R1 initiates a link state packet on behalf of the pseudonode. In
   this case the ID of the pseudonode is a 7-byte quantity which R1 can
   be sure is unique within the campus, usually the 6-byte system ID of
   R1, concatenated with a byte chosen by R1 to differentiate this
   pseudonode from any other link for which R1 might also be Designated
   RBridge.

But I think that those ID should not use the 6-byte system ID of DR.
Because RBridge could be replaced in case of failure, and the replaced
RBridge might be returned to the network with same system ID after it
is repaired.

We can say that the node ID of that shared link is changed to a new
DR's system ID. Removing the old ID and adding the new ID from/to an
adjacency list is not a good way, if the shared link does not
disappear but only the old DR disappear.

I don't think that we can keep using the node ID of that shared link
generated by disappearing DR's system id, because, as I mention
earlier, the removed old DR might come back to network with same
system id, and it might eventually be a new DR on another shared link.

I think that it is better to use "19-bit nickname" or random number
instead of system ID.

(4) Fast reroute
I wonder if Trill intends to have fast reroute mechaninsm or not in future?

(5) Ingress RBridge Tree (IRT)
I would like to clarify if my understanding is right or not.
If there are 100 RBridges, all RBridges will make 100 of IRT. Right?

Since there is no ingress tree distribution mechanism proposed, all
RBridges need to know its IRT and other RBridges' IRT from link state
in order to create tunnels.

Masanori