Extreme Launches A Sonet Killer

Extreme Networks Inc http://www.extremenetworks.com today announced a new twist in the likely development of future carrier networks. It unveiled a new Gigabit Ethernet switch - the Alpine 3800 - and claimed that with it, carriers can guarantee latencies on metropolitan area networks (MANs).

If Extreme is right, that's a very big deal. It means that carriers can carry voice and video over such networks and be sure that quality of service won't suffer.

"This is a huge opportunity for Extreme," says Gordon Stitt, the vendor's president and CEO. "We can do what Sonet does and we can do it at one fifth the price." Once some carriers start cashing in on this opportunity, others will have to follow suit - rendering ATM and Sonet obsolete.

That's the idea, but can Extreme really deliver on its claim of being able to guarantee latencies? Does Gigabit Ethernet stack up as a serious replacement for ATM and Sonet?

The short answer to both questions is Extreme has certainly made Gigabit Ethernet more carrier friendly, but it's doubtful whether existing operators will take the plunge with this new technology.

Why's that?

Let's start with the good news: Ethernet's Alpine 3800 certainly has better carrier credentials than its Gigabit Ethernet competition - notably from Foundry Networks Inc. http://www.foundrynet.com and Cisco Systems, Inc. http://www.cisco.com

Like its rivals, Extreme uses the IETF Diff Serv standard for identifying and classifying IP traffic and uses the IEEE 802.1p QOS standard for prioritizing it. But that's just for starters. Extreme also uses two other technologies for making sure that shorter packets carrying time sensitive traffic such as voice and video don't get stuck behind longer packets carrying data - resulting in variable delays and quality of service problems.

First, its Alpine 3800 switch queues traffic on both in-bound and out-bound ports, rather than just on out-bound ports, as is normally the case.

Having in-bound queues enables Extreme to implement its second technology, a "fixed time sequencer" which is really the key mechanism behind its claims of guaranteed maximum delays. With this scheme, each port is serviced at a specific time interval, during which time 64 bytes of data is read. If the packet is longer than 64 bytes, then it's read in sections at each time interval - a system that lets smaller packets overtake bigger packets.

Does this add up to a Sonet killer? Not really, on two counts.

First, the mere fact that the switch has queues implies that delays can vary. It's probably true that the delays won't vary by much if the network is engineered properly - but that isn't equivalent to Sonet. With Sonet, a continuous, fixed bandwidth circuit is set up across the carrier backbone. Queuing can't occur within the network; it can only occur at the entry point, and that makes backbones easier to engineer and makes their performance more predictable.

Second, Sonet also brings a lot of other benefits to the table - notably ways of automatically rerouting traffic around failures. "Making IP more deterministic is one important factor," says John Reeves President and CEO of Sirocco Systems http://www.siroccosystems.com, an optical networking vendor with products that support IP, ATM and Sonet technologies. "But it won't be enough for service providers to take the Ethernet plunge. They need more robust protection and management like what they get with Sonet."

Even if Gigabit Ethernet wins the technical argument, it could face regulatory hurdles, according to Tom Nolle, president of CIMI Corp.http://www.cimicorp.com, an independent consultancy . Incumbent carriers can avoid unbundling their services by sticking to ATM and Sonet, he contends. For this reason, "there is no way that a product like Extreme's will ever be deployed in a major carriers' network," he says.

Extreme acknowledges that Ethernet in the MAN will be a tough sell in more established carrier networks. Right now, the company is focusing on winning accounts with greenfield providers like Yipes Networks http://www.yipes.com, a data only network that is now in several markets throughout the US (see Yipes Bets Big on Gig).

"Once these new players start taking business away from the incumbents, they'll wake up," says George Prodan, VP of marketing for Extreme, "And they'll see that while they were sleeping, the new age players ate their lunch in the metro space."

by Marguerite Reardon, senior editor, and Peter Heywood, international editor, Light Reading

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