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Kicking the tires - Know what you're buying

A brief look at the components of a network and some key points of interest.

Dealing with vendors is getting increasing complex. When you buy a car, you can kick the tires, take it for a test drive, and even give it a little extra gas before you make the purchase. Network equipment is a bit different. For starters, equipment doesn't like to get kicked. So how do you really know what you're buying? We're going to take a brief look at the components of a network and some key points of interest.

Of course all networks rely on cabling systems. They may be copper, fiber or a combination of both. These systems are particularly important as they are deemed a 10-year investment or 12-year investment. They will carry signals for 2-3 different electronics systems. The TIA/EIA (Telecommunications Industry Association/Electronic Industries Alliance) Cat6 Consortium and manufacturers such as Dell and 3Com all recommend a minimum of Category 6 for all new cabling channels. The cabling industry echoes these recommendations. Category 6 has superior noise immunity and will adapt better to real world situations than its earlier counterpart, Category 5e. Remember, this is a 10-year investment at least. All cabling, connectivity and components should be Category 6. Even if your electronics state that they will run on is 5e, remember that they are tested in a lab under pristine conditions that don't always happen in office environments.

Fiber is a bit different. With fiber, you have options depending on distance and speed. The chart below shows different fiber capabilities and lengths.

Application Wavelength 62.5
100BASE-SX 850nm 300m 300m 300m 300m N/A
1000BASE-SX 850nm 220m 275m 550m 550m N/A
100BASE-LX 1300nm 550m 550m 550m 550m 5km
10GBASE-SX 850nm 28m 28m 86m 300m N/A
10GBASE-LX 1310nm N/A N/A N/A N/A 10km
10GBASE-EX 1550nm N/A N/A N/A N/A 40km
10GBASE-LX4 1310nm 300m 300m 300m 300m 10km

The top number on the fiber rating indicates the diameter of the fiber, while the second number indicates the cladding. All fiber listed is multi-mode fiber with the exception of the last column which is SMF or single mode fiber.

There are many cabling and connectivity manufacturers and it's important to understand all of the parameters listed within a cabling system to be assured that you are purchasing the best system possible. The 10GBASE-T (10 Gbps transmission over twisted pair cabling) initiative at the IEEE is moving forward with the development of the standard. The criteria states that they will develop a standard supporting 10G transmission at 100m for Category 7, and 55-100m for Category 6. Category 5e is not part of this effort. But in an effort to illustrate the life of a system, five years ago, gig was still in development. It is now standard in all new PC's that ship. 10G is already being developed. The point being that you will want to put in a system that will last a lifetime. Removing and replacing gets pricey!

Watch for the "Cabling primer" coming soon that will explain all of the parameters and terms like insertion loss, near end cross-talk, and modal dispersion to assist you in understanding how these affect your decisions.

Moving up a couple of layers to switches and routers the choices here are abundant. Price is always a consideration, as it should be. But there are some other factors that you will want to be aware of. The first is functionality. Switches are categorized as Layer 2 (bridging only) or Layer 3 (some routing capabilities). Newer switches coming to market are called Layer 7 switches, which allow some routing and prioritization of application traffic. Knowing what you are running on your network will help with this decision. For instance, if you know you will be running some VoIP applications that require steady and reliable bandwidth, it may be a good idea to look for switches that will allow you to prioritize that traffic.

Switches also come with different versions of operating systems. If you are running AS/400's and plan on using SNA, you want to be sure that your switch will support that traffic as well. Make sure that your switch supports all of the protocols that you plan to use. VLAN's can provide you with some traffic segmentation and in larger environments or manufacturing environments where process controllers continuously talk to their monitors, this can be a good option to assure that this traffic stays within a few ports and does not cause a bottleneck in the switch.

Routers are getting more sophisticated as security risks are becoming more predominant. Routers not only handle routing of traffic in and out of a network, but today's routers also offer services such as VPN's (Virtual Private Networks), firewall capabilities and Network Address Translation (NAT). You will want to be sure that you don't overload your router with services. Also, if several remote users use the network, redundancy is critical. One router that controls all of the access services may be more costly than separate boxes if a redundancy options are not in place. Downtime = $$$$. Another feature that can be quite important is the ability to change out modules and provide different functionality within the same chassis. This can be a cost savings down the road and provide you with several options that are not available with fixed port type switches and routers.

When looking at switches and routers pay close attention to figures like Mean Time Between Failure. This often-overlooked number will give you a great indication of the reliability of the equipment and the quality of the engineering and manufacture. Other figures like PPS or packets per second will let you know the speed in which it can process packets. Some vendors bypass this number and just say their switch is "wire speed" meaning that packets are processed at the speed of the backplane. Vendors will supply you with lots of numbers, some useful, some not. Make sure that you understand the numbers and can compare like figures.

Watch for the "Electronics primer" coming soon that will explain the terms used by the vendors, what they mean to you. The primer will include several scenarios to help you in your planning.

Moving up another notch to servers and storage, and here your options are huge! The newest player in the market is blade servers. While not all applications support them yet, they are expected to soon. Every square inch of a data center is prime real estate. The cost for the space, heating/cooling and power requirements added to the fact that there are many employees relying on what sits in that space makes its dollar to square foot ratio quite high. The new blade servers are great options for running supported applications. As with any new technology -- do yourself a favor and check with your application vendor FIRST. If your application won't run on the platform you will have nothing but headaches.

Storage now comes in the form of Network Attached Storage (NAS) where several servers can share the same storage unit. Storage Area Networks (SANs) are another configuration and may be either directly attached or accessed over a common protocol. The protocol options are also there. IP is vastly becoming the standard for everything. Whether native or encapsulating -- other storage access commands the trend is one common protocol.

Watch for "Are you dense? Data Center design considerations" which will cover new standards for data centers and key design considerations for your data center.

Carrie Higbie, Global Network Applications Market Manager, The Siemon Company
Carrie has been involved in the computing and networking industries for nearly 20 years. She has been involved in sales, executive management, and consulting on a wide variety of platforms and topologies. She has held Director and VP positions with fortune 500 companies and consulting firms. Carrie has taught classes for Novell, Microsoft, and Cisco certifications as well as CAD/CAE, networking and programming on a collegiate level. She has worked with manufacturing firms, medical institutions, casinos, healthcare providers, cable and wireless providers and a wide variety of other industries in both networking design/implementation, project management and software development for privately held consulting firms and most recently Network and Software Solutions.

Carrie currently works with The Siemon Company as the Global Network Applications Market Manager where her responsibilities include providing liaison services to electronic manufacturers to assure that there is harmony between the active electronics and existing and future cabling infrastructures. She participates with the IEEE, TIA and various consortiums for standards acceptance and works to further educate the end user community on the importance of a quality infrastructure. Carrie is one of the few that chose to work with applications and networks providing her with a full end-to-end understanding of business critical resources through all 7 layers of the OSI model. Carrie currently holds an RCDD/LAN Specialist from BICSI, MCNE from Novell and several other certifications.

This was last published in January 2004

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