Subject: [rbridge] draft protocol-10 WGLC Multicast Addresses

From: "Donald Eastlake" <[email-masked]>
Date: Wed, 26 Nov 2008 17:08:37 -0500

Hi,
When TRILL started, it had only one multicast address: All-RBridges. Then it
was decided that encapsulated IS-IS frames would have an Inner.MacDA of
All-IS-IS-RBridges and there were two. Now there are three multicast
address: (1) IS-IS frames are not longer encapsulated
and  All-IS-IS-RBridges is their Outer.MacDA, (2) All-RBridges is the
Outer.MacDA for ESADI and multi-destination data frames, and (3)
All-ESADI-RBridges is the Inner.MacDA for ESADI frames.

I don't think we are going to need any more than these three multicast
addresses for the Base Protocol Specification but multicast addresses are
cheap. 802.1 initially allocated itself a block of 16 addresses for bridging
and link protocols (see, for example, 802.1D-2004 Figure 7-10 or the more
recent 802.1Q-2005 Table 8-1) with the defined behavior being that a bridge
was required to drop any frame sent to one of these addresses if the bridge
did not understand the protocol(s) indicated by that address. This sort of
behavior has to be specified at the beginning. Once you start shipping
devices that are transparent to some addresses, you can't practically later
say they have to drop them if they don't know the protocol(s) associated
with those addresses. (This behavior for bridges has been somewhat modified
for more recent complicated cases like provider bridging.)

So, I propose that, when we apply, we get a block of 16 addresses with the
ones listed in the first paragraph above being the first three addresses in
this block and the remaining 13 being reserved for future use. And that the
protocol specification require RBridges to drop frames with Outer.MacDA
being any of these 13 addresses (unless the RBridge understands some future
use of that address).

Thanks,
Donald
=============================
Donald E. Eastlake 3rd   +1-508-634-2066 (home)
155 Beaver Street
Milford, MA 01757 USA
[email-masked]
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