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Ethernet's Resiliency
By Michael Cooney
As Ethernet has cast its ever-growing presence to WANs and
metropolitan-area networks, the need to bolster its robustness
and durability have grown with it. Hence we've seen efforts to
do just that.
Perhaps the most visible effort, and the one that has garnered
the most "spirited discussion" shall we say, is the IEEE's
802.17 Resilient Packet Ring proposal. In a nutshell, RPR
defines how to make Ethernet service infrastructures in the
metropolitan area as resilient as today's SONET rings, which
feature 50-msec rerouting when failures occur.
The problem has been the infighting over what the specification
should ultimately look like. Cisco has a proposal on the table
likewise a coalition of vendors. That mess aside what is
happening is a variety of vendors is building pre-RPR products
and services to sort of fill-in where RPR will be. One of those
technologies Riverstone's Rapid Ring Spanning Tree (RRST) has
been brought forward in our Technology Update this week.
Riverstone's RRST is software that could be used to introduce
basic SONET-like link recovery functions for Ethernet switches
deployed in a ring topology. In case of a link or node failure
on a metropolitan Ethernet ring, RRST software would identify
the outage and redirect traffic, the company says.
Our Riverstone author says that RRST takes advantage of
numerous enhancements to the traditional Spanning Tree
Protocol, known as 802.1D. For example, it utilizes the
recently standardized Rapid Reconfiguration Protocol, known as
802.1w, in order to make rapid decisions to change a port state
from blocking to forwarding and vice versa.
Should you want to read more about RRST, check out:
http://www.nwfusion.com/news/tech/2002/0121tech.html
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To contact Michael Cooney:
Michael Cooney is an Associate News Editor. Aside from his news
responsibilities, Cooney handles the Infrastructure and
Enterprise Application sections of Network World. Cooney has
been with in the industry for 13 years -- the last 9 with
Network World.
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