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High-speed Ethernet planning guide

Everything a network architect needs to know about migrating to 40/100Gigabit Ethernet

By , Network World
October 24, 2011 12:05 AM ET

Network World - Ten-gigabit Ethernet was so last year.

Standards-based 40- and 100-gigabit Ethernet switches and routers are starting to show up in enterprise networks, following ratification of the IEEE 802.3ba specification in mid-2010.

100Gigabit Ethernet bridge to Terabit Ethernet

It's easy to understand the motivation: Fast downlinks require even faster uplinks. The current solution, link aggregation of multiple 10-gigabit pipes, works well but only scales up to a point.

At the same time, servers for some high-performance applications now use 10-gigabit network interface cards, again requiring a faster uplink at the switch. It won't be long before 10-gigabit interfaces will be a standard part of server motherboards, just as gigabit Ethernet comes standard today.

For network managers, migrating to "higher-speed Ethernet", as it's been dubbed by the Ethernet Alliance, will definitely require some changes. Most of these are at the physical layer (new cabling may be required). Also, some monitoring and management gear may not be able to keep up with HSE rates.

On the plus side, HSE will help reduce prices for 10G Ethernet devices. "The real leverage [with HSE] is with pushing down the price point of 10-gigabit Ethernet, rather than the first-order effects of 100-gigabit deployment," says a senior architect at one of the largest ISPs in the U.S., who requested anonymity. "If bigger pipes are good, then bigger pipes that are affordable and create greater commoditization of 10-gigabit Ethernet are better."

Also, HSE is far more evolutionary than revolutionary. Network professionals who've worked with Ethernet will feel right at home with the 40G- and 100Gbps versions. Still, an understanding of what's new is essential (see sidebar: "5 steps to high-speed Ethernet").

No design changes

Migration to 40- and 100-gigabit Ethernet requires no modification to upper-layer network design, networking protocols, or applications. "It all looks the same to the upper layers," says Brandon Ross, Eastern U.S. director of network engineering at Torrey Point Group, a network design consultancy. "There aren't any changes needed."

That means, for example, that a network using the rapid spanning tree protocol (RSTP) between switches and open shortest path first (OSPF) between routers can continue to run these protocols across HSE interfaces, without configuration changes.

Applications, databases, and server farms similarly won't be affected by the addition of HSE interfaces to enterprise networks. Lower latency and improved response time should be the only noticeable effects, although Ross cautions that adoption of faster networking technologies inevitably exposes bottlenecks that weren't previously visible. If, for instance, network latency previously masked a disk I/O bottleneck and HSE is now faster than the bottleneck, application performance won't improve as much as expected.

That raises a critical question when it comes to HSE adoption: Even if the protocols are ready, is the network infrastructure ready for higher speeds?

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