Subject: [rbridge] PS Issue #3

From: Eric.Gray at marconi.com (Gray, Eric)
Date: Thu, 8 Dec 2005 12:21:53 -0500

--> 
--> #3 IF size is an issue...
--> 	what limits the size? STP/RSTP or broadcast traffic, or both?

Not sure what we mean by "size" here and how this differs from
"scale."

Obviously, an RBridge campus is limited to the size of workable
STP/RSTP solutions only in the fully-meshed connectivity case.
The complete solution may be several times as large given that
STP/RSTP domains exterior to the campus are made smaller.  In
addition, some proposed campus topologies will allow for smaller
STP/RSTP domains even within the RBridge campus. 

Employing multicast routing techniques against L2 multicast, may
allow for a larger broadcast domain as well.  This is especially
true given flooding within RBridge campi will be significantly
less than in a typical 802.1 LAN.

However, the size of the broadcast domain including exterior LAN
segments will ultimately determine the maximum "size" (at least
size measured as numbers of contiguous LAN segments).

--
Eric

---

From: gibanez at it.uc3m.es (Guillermo Ibáñez)
Date: Thu, 08 Dec 2005 21:36:00 +0100

>STP/RSTP domains even within the RBridge campus. 
The concept of a core formed by only  Rbridges, each ingress Rbridge 
being the root (or annex to root bridge) of an RSTP/STP  of standard 
bridges provides network predictability and scalability, besides getting 
rid of the need to modify the frame at each Rbridge hop with the next 
hop Rbridge address.
Guillermo

>size measured as numbers of contiguous LAN segments).
ARP traffic estimations should be done with and without ARP proxies to 
evaluate both the bandwidth (less critical, given
its abundance :1 Gb, 10 Gb Ethernet )  and, most important, the ARP 
processing effort at endnodes  (all network endnodes must process a 
cach? miss ARP).
Guillermo

>--
>Eric
>
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>  
>

-- 
Guillermo Ib??ez
Departamento de Ingenier?a Telem?tica
Universidad Carlos III de Madrid
1.1.B.11 Colmenarejo 91-6241393
4.1.F.13 Legan?s 91-6248794