The Network Hub

Sep 8 2010   4:19PM GMT

Some more advice on using commodity switches at the LAN access layer

Shamus McGillicuddy Shamus McGillicuddy Profile: Shamus McGillicuddy

Last week I wrote a story about how some enterprises save money by using commodity network switch vendors at the access edge of their local area networks. These low-cost vendors use merchant silicon and build basic-functionality switches to keep their costs low. While reporting this story, I emailed several questions to Bjarne Munch, an Australia-based principal research analyst with Gartner. Munch was on vacation at the time and was unable to respond to my questions until now. I’ve pasted my questions and his answers below.

1. You advocate that enterprises save money by using Layer 2 switches wherever possible. In what scenarios would an enterprise want to have layer 3 routing on their edge/access switches?

I would say not very often, but in cases with a high degree of VLAN segmentation there may be a need for routing in the access for some more distributed network design. Or in cases where the Layer 2 functionality do not offer sufficient QoS, this could be situations with high use of both voice and video from the desktop.

2. You mention that enterprises generally don’t need Gigabit Ethernet to the desktop. In what situations would you say enterprises should pull Gigabit all the way to the desktop?

If you add bandwidth needs for a typical enterprise user and incorporate UC and Video you will not even get close to 100M to the desktop. Some enterprises with CAD/CAM such as city planning or architects may have higher bandwidth needs or in the medical area with X-ray images. But this is a niche which is typically easy to identify.

3. You mention that enterprises can drive costs down even further with commodity switches by adopting automation for operational tools. Could you elaborate on this further?

A large percentage of the ongoing cost is labor-based, i.e. time based on configuring or trouble shooting. For larger networks operational tools that can automate these processes can thus save time and thus reduce the ongoing operational costs, i.e. bring down the TCO.

4. You talk about using fixed-format switches over modular ones where possible to drive down costs. In what kinds of situations will enterprises be required to deploy modular switches at the edge?

Most cases I have seen have been just in case investment where the enterprise was not sure of needs so they chose a modular switch partly for switch port expansion but also for housing of other functions such as WLAN controller

5. These low-cost vendors use merchant silicon instead of ASICs to keep costs low. What exactly is the value of those ASICs? What are enterprises losing by deploying switches with merchant silicon at the edge?

There is some loss of performance by using merchant silicon and there may also be some degree of performance variations depending on traffic load but for most enterprises this is not really an issue within the edge of the network.

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