[rbridge] TRILL control frames communication

Hi!

Given in RFC6325 section 4.2.3
TRILL IS-IS frames are never forwarded by an RBridge but are locally
processed on receipt.  (Such processing may cause the RBridge to send
additional TRILL IS-IS frames.)
Given in RFC6325 section 4.6.2
1. If the Outer.MacDA is All-IS-IS-RBridges and the Ethertype is L2-IS-IS,
the frame is handled as described in Section 4.6.2.1.
4.6.2.1. TRILL Control Frames: The frame is processed by the TRILL IS-IS
instance on RBn and is not forwarded.
As IS-IS frames are never forwarded by an RBridge, why All-IS-IS-RBridges
multicast address is used? Please clarify.

As per my understanding TRILL IIH frames are sent to the neighbors, bounded
by RBridges ( Broadcast domain is link)
Am I right?

     +-------+    +---------+    +---------+         +---------+
+----------+   +-------+
     | ESa +----+ RB1  +----+ RB3  +--------+ RB4  +-------+  RB2  +---+ESb
|
     +-------+     |ingress|     | transit|          | transit|        |
egress |    +-------+
                    +---------+    +---------+         +---------+
+----------+

If all RBridges are just up, following pattern will be followed:
RB1 send TRILL IIH to RB3
RB2 send TRILL IIH to RB4
RB3 send TRILL IIH to RB1 and RB4
RB4 send TRILL IIH to RB2 and RB3
Please correct me, if I am misinterpreting it.

TRILL IS-IS LSP's are used to communicate the link information to the
campus. That's how, RBridges know each other.
As RBridges do not forward TRILL IS-IS frames, how information (TRILL IS-IS
LSP) of RB1 is communicated to RB2?

Thank you!

-- 
Best Regards,
Muhammad Mohsin Sardar

[rbridge] TRILL control frames communication

Attachment: TRILL.txt