Whether you are into broadcasting, post-production, video capture or editing, you are probably making greater demands on your switching hardware than ever before.
Customers are demanding higher quality content, while at the same time forcing more of their data exchange (phones, video and audio) onto the network. Systems (even inexpensive embedded units like printers) are starting to come equipped with 1GigE. Wireless access points are getting faster as well. The results are often lackluster at best and disastrous at worst — phone calls and video with jitter, failed captures and lost data.
What can you do to assure that you're not headed for a train wreck with your current switch?
First of all, the old adage “you get what you pay for” applies here. The retail network switch market is extremely competitive, and almost all vendors price their hardware as low as possible. Paying less generally means getting less. You will either get less support, less performance, fewer internal resources or fewer features.
You could move to a name brand unit, but the costs are prohibitive. Is it really worth paying five times the cost of a retail unit for the extra peace of mind?
After a great deal of searching and negotiations with manufacturers, Small Tree now carries a line of switches called Edge-Core. They have the performance and reliability of the high-end units at a low cost.
Considering our assertion that less cost means less support, less performance, fewer resources and fewer features, let's go through those in detail.
Gauging support and performance
Support often speaks for itself. When something does melt down, who is going to get on the phone to help? Most switches end up installed in relatively simple configurations where debugging is generally no more complicated than moving cables and ports around to see what's broken. When additional hardware — such as multiple networks, IP telephones and wireless networks — is added to the mix, things get more complicated, and fast. If you run into a multicast loop, your network can come down very quickly, and without the help of experienced network personnel, most end users won't figure this one out. The switcher line supports high-end features like spanning-tree protocol to help work out issues like this without a lot of fuss. And the service team is well-equipped to assist users operating Apple systems.
Switch performance is a difficult concept to understand. A switch seems like a bunch of electronic plumbing, connecting a group of systems together. Everything is gigabit Ethernet, so one would assume all switches are the same. In fact, a quick online census of good vs. bad switches shows that just about all vendors claim their switches are nonblocking and will provide line rate performance. This means that, in theory, the user could have each port pushing data out, sucking data in, or both, all at 1Gb/s simultaneously.
This would be great provided that's what we all wanted to do. The problem is most networks aren't set up to work this way. Data isn't uniformly spread across a network on 23 machines. Data lives on the server. Phones connect to a private branch exchange (PBX). The server and PBX aggregate many connections into one place. Thus, the switch has to deal with the natural congestion that occurs when bursts from multiple locations try to go to one place. This same phenomenon occurs in the broadcast industry when a server is asked to multicast content to many machines.
For example, a group of broadcast application engineers recently called to ask if our Ethernet driver had issues because their video was jittering when it was sent to 30 clients. After some quick investigation, it was discovered that their line rate switch was dropping packets almost immediately when they started their video feed. It could not deal with the congestion of a single gigabit stream getting replicated to 30 other ports. This would seem like an obvious thing for a high-performance switch claiming to handle line rate capabilities. Our switcher line is able to handle these bursts smoothly and let your network and server ride through these issues longer and with little or no disruption.
Switches aren't just plumbing. They have to do a lot of work. Each packet coming in has to be checked for consistency and then forwarded to the correct place. Gigabit Ethernet can generate more than 80,000 packets per second. The longer it takes the switch to analyze each packet, the higher the latency (the time it takes for a packet to flow across the switch from one port to the next). As latency increases, the switch's sensitivity to overload conditions increases as well. (See Figure 1.)
A good switch needs to have the CPU power to efficiently handle its expected workload and sufficient buffer memory to handle bursty overloads. Provided it can ride through the occasional overload condition, the switch will provide smooth performance.
With insufficient resources, the switch will quickly begin dropping packets during even brief overload conditions, resulting in more traffic as systems attempt to recover the missing packets. This leads to additional (and sustained) degradation. Edge-Core provides high-end Broadcom Network processors that can quickly process each packet. Many low-end switches are basically running an internal operating system and doing all of their switching operations in software. This means higher latency and lower overall throughput.
Check the features
It's important to consider the vast number of features when looking at switches. It's not always easy to figure out which ones are necessary for your environment. Do you need spanning-tree support or broadcast storm control? Should you buy a switch that supports static or dynamic link aggregation (IEEE 802.3ad)?
The short answer: It depends. Features like spanning tree and broadcast storm control are important if you plan on adding multiple switches to your network. They help prevent infinite loops where packets are continually forwarded around the fabric.
Additional features like 802.3ad link aggregation and 802.3x link-level flow control are extremely important in server environments where a single source of data (server, PBX, etc) might exist and need extra bandwidth along with the ability to smoothly deal with congestion. Good switches will also have prioritization and QoS features, allowing an administrator to select which ports should have priority when congested conditions occur.
Small Tree's Edge-Core line provides all of these features and allows users to easily enable, disable and configure them using their Web browsers. It is also easy for users to save configurations, allowing them to try things without a commitment. It's as simple as a reboot to put things back as they were.
A good switch does more for business than acting as the plumbing between systems. It assures that data flows smoothly, phone calls are crisp, and applications function flawlessly. You regularly spend thousands of dollars to purchase a high-quality desktop to run your applications, so why connect 20 such systems with a sub-standard switch?
Steve Modica is CTO of Small Tree Communications.
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