Metro Rings

 
 
By eweek  |  Posted 2001-09-24 Email Print this article Print
 
 
 
 
 
 
 

One of the least vulnerable networks is metro Ethernet, which has a multiple-ring architecture that lets data change directions and reroute if it runs into congestion or equipment failure. It also lets customers ratchet up bandwidth in seconds - rather th

One of the least vulnerable networks is metro Ethernet, which has a multiple-ring architecture that lets data change directions and reroute if it runs into congestion or equipment failure. It also lets customers ratchet up bandwidth in seconds - rather than days - during an emergency. Gigabit Ethernet networks can be constructed with so much resilience, they are almost fail-safe in any situation, said David Neil, vice president of Gartner. "You can have more than one ring going around the city, and leap from one ring to another to get over a failing component."
The problem, however, is that many metro rings rely on the more vulnerable first-mile connection. "Once you get on the Gigabit Ethernet ring, the metro area network, you should be quite safe. The issue is getting on there," Neil said.
Providers such as Yipes Communications offer their customers ring architecture right to the building. And most of Yipes 3,000 customers opt for it, said Kamran Sistanizadeh, the companys CTO. "We have a north and south entrance. The fiber comes into the building, gets terminated in a box, then comes out at another box and exits the building on a different path." If one side of the ring is lost, the data turns and goes through the other. Yipes networks performed without a hitch during the terrorist attacks on New York and Washington, just as they did in February, when an earthquake rocked Seattle. "Regardless of what we say about why metro Ethernet is theoretically better, in a practical demonstration, our networks survived," said Ron Young, co-founder of Yipes and chairman of the Metro Ethernet Forum.
Telephone companies snipe at the Ethernet players, saying rerouting through the maze of Ethernet rings and meshes can delay delivery of traffic anywhere from 200 milliseconds to two or three seconds. Thats in contrast to the much faster 50-millisecond latency in the circuit-switched world. But the members of the MEF bark back that theyd rather have a two-second delay and get the data, than have the data get close to the destination at blinding speed, only to disappear because a line card or trunk card has failed. "The majority of enterprises would prefer to have the service, although it might be a few milliseconds later," Young said. But Peter Evans, Nortel Networks vice president of marketing of metro optical solutions, said a two-second delay is too long for banks, brokers and financial institutions that transfer money and stocks in milliseconds. Nortel is building 50-millisecond latency into optical Ethernet networks, Evans said. Putting "five nines" reliability into the networks it builds for carriers gives Fortune 250 companies the option to get out of the network business and instead rely on service-level agreements from trusted carriers. Still, any network - circuit-switched, Ethernet or IP - has several single points of failure if redundancy hasnt been built in to guard against a natural or human-caused disaster.
 
 
 
 
 
 
 
 
 
 
 

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