Up to speed

Foundry Networks' BigIron 8000 is one of the company's series of 10-Gigabit-ready Layer 2 and 3 switches.

3Com's Switch 7700 provides multilayered 10-Gigabit switching; three chassis are available

10-Gigabit Ethernet switches and routers add speed and a lot of distance to your network

Last year, I predicted that this would be a good year for 10-Gigabit Ethernet switch and router manufacturers because of the growing demand for high-bandwidth connections in enterprise networks.

I was right, but not right enough'I hadn't realized just how fast the market would grow.

Synergy Research Group, a Phoenix-based market research company, says the market for 10-Gigabit Ethernet switches grew by more than 250 percent in the first quarter this year over the same period last year.

The number of 10-Gigabit Ethernet port shipments has grown by almost 2,000 percent since last year'an indication of lower port prices and the overall growth of the market.

The key use for 10-Gigabit technology exists within large enterprise networks and, to a lesser degree, data centers, metropolitan area networks and enterprise storage centers. Over the past few years, these applications have called for a huge increase in Gigabit Ethernet connectivity.

Why 10-Gigabit Ethernet? In the first place, it has cost advantages over competing high-bandwidth technologies such as 10-Gigabit Sonet and 10-Gigabit Fibre Channel for storage networks.

10-Gigabit Ethernet also supports all network services, including packetized voice and video data, and Layers 3 through 7 of network intelligence. It easily scales for both enterprise and service-provider networks and supports virtually all network configurations.

And since 10-Gigabit Ethernet is the first version of Ethernet to be entirely full duplex from the outset, it doesn't require the use of carrier-sense multiple-access with collision detection (CSMA-CD) methods that could slow earlier versions of Ethernet.
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Most important for many users, 10-Gigabit Ethernet exceeds the 5-kilometer distance limitation between repeaters. A number of third-party providers are shipping optical Xenpak transponders that allow for distances of up to 40 kilometers between devices on a 10-Gigabit Ethernet network.

Even for sophisticated buyers who keep up with networking, the question of when to use switches or routers in a 10-Gigabit Ethernet network segment can be perplexing.

Basically, a network switch is a device that joins multiple computers and workstations at the physical Data Link'Layer 2'layer of the Open Systems Interconnection model.

More intelligent

Layer 2 switches can inspect data packets as they are received, determine both the source and destination devices of the packets, and forward them appropriately. Because Layer 2 switches only look up the packet's Media Access Control address, they are known as dumb switches'not much more intelligent than their immediate ancestors, network hubs.

Routers are Layer 3'OSI Network Layer'devices used to connect networks, not simply other devices on the networks, so they are generally much more intelligent than Layer 2 switches.

Routers can determine the best path over the network, or multiple networks, to a destination host by looking at the header portion of an incoming packet, which contains the recipient's network address at Layer 3. The router then compares the destination address to its routing table and forwards the packet to the correct address.

Layer 3 switches are similar to routers in that they use the same routing algorithms. The primary difference between them depends more on usage than features. To further confuse the issue, Layer 3 switches are often called switch/routers because they provide many of the routing capabilities that routers do.

Newer switch models capable of providing Layers 4 through 7 switching are sometimes called content-aware because they also provide application-level information to users.

Even the largest carrier networks don't necessarily need a huge switch or router chassis filled only with 10-Gigabit Ethernet components. Because enterprise networks and MANs generally run a combination of 10-Mbps and 100-Mbps Ethernet, there's still a need for devices that support dense 10/100 Ethernet interfaces with several Gigabit Ethernet uplinks.

For this reason, large switches and routers need to support such technologies as Sonet, asynchronous transfer mode, frame relay and Multiprotocol Label Switching (MPLS) 10/100 Ethernet and Gigabit Ethernet.

J.B. Miles writes from Honomu, Hawaii. E-mail him at jbmiles@starband.net.

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