Making the Transition to Gigabit Ethernet

The Switch

My first step in making the transition to gigabit Ethernet was to shop for a gigabit switch. There are countless Web sites that sell gigabyte switches, but there are a lot of things that you need to consider prior to making a purchase.

The first thing that you need to consider is whether the unit that you are considering is a hub or a switch. The difference between hubs and switches all comes down to collision domains. On a simple Ethernet network, all nodes exist on a common segment. When a machine sends out a packet, the packet goes to every machine on the segment. If two machines happen to transmit packets at the same time, then a collision occurs. When a collision happens, both packets are destroyed and must be retransmitted.

Collisions increase as the amount of traffic on a network segment increases. The problem is that collisions can become excessive and can slow a network to a crawl. Switches were developed to reduce the problem of excessive collisions. A switch maintains a table of which PC is connected to which port (based on MAC address). When a PC transmits a packet, the switch looks at the packet’s intended destination and forwards the packet directly to the destination computer rather than to every computer on the network. This greatly increases the potential speed of the network because not only are collisions almost eliminated, multiple communications can now occur simultaneously.

Hubs were extremely common a few years ago, but are starting to go extinct. Even so, if you happen to spot a really good price on gigabit hardware, it’s possible that the unit is a hub, so it’s important to check to make sure that you are buying a gigabit switch and not a gigabit hub.

The next thing that you need to check is the switch’s throughput. The switch that you select needs to support 10 / 100 / 1000 speeds on each port. While I was shopping for my switch, I ran across quite a few gigabyte switches that only supported 10 / 100 / 1000 on two ports. The remaining ports only supported 10 / 100.

I also encountered a disturbing number of gigabit switches that only supported 1000 megabits. Even if you are planning on making every machine in your entire organization run at gigabit speeds, it is extremely important to buy a switch that is backward compatible with 10 / 100 speeds. The primary reason for this is that having a switch that supports 10 / 100 / 1000 allows you to make the transition to gigabit Ethernet gradually. If your switch supports only gigabit, then you will have to convert every machine that’s connected to that switch simultaneously, which could lead to a significant amount of down time during the transition.

The other reason why it’s important to make sure that your switch is backward compatible with lower speeds is because not all of the devices on your network will run at gigabit speeds. For example, I own a fairly high end printer that connects directly to my network through an Ethernet connection. As expensive as the printer is though, it does not support gigabit speeds. If I had installed a switch that supported gigabit speeds only, I would have lost the use of my printer. Wireless access points are another great example of devices which must connect to your network, but that do not run at gigabit speeds.

The last thing that I recommend checking for when shopping for a switch is the switch’s total throughput. Remember that Ethernet (over twisted pair) is a base band technology. This means that separate wires are used for sending and receiving data. A full duplex switch should support transmitting data at up to 1000 megabits and receiving data at up to 1000 megabits. Therefore, the total throughput of your switch should ideally be 2000 megabits multiplied by the number of ports on the switch. Normally, this won’t be an issue, but I have seen some switches that have an unexpectedly low total throughput.

There are other features that you can look for when selecting a switch, such as the ability to manage the switch through SNMP or the ability to mount the switch on a rack. However, the issues that I have addressed are the most important things to look for when shopping for a switch.

Cabling

Probably the biggest hurdle of upgrading to gigabit Ethernet was the cabling issue. A lot of people seem to think that you can transmit data at gigabit speeds over standard CAT5 cable. This is a myth though. Currently, the only twisted pair cables that support gigabit Ethernet are CAT5E and CAT6. There is also an emerging CAT7 standard, but I  don’t think that CAT7 cable exists yet.

If your network happens to be wired with CAT5E or CAT6 cable, then you are all set to make the upgrade. All you have to do is to plug in your new switch and start replacing network cards. Unfortunately, my network was wired with CAT5, so I had to run a lot of new cable. I chose to go with CAT6 because it’s a little less susceptible to interference than CAT5E.

Pulling the cable wasn’t any big deal, but attaching the RJ-45 connectors was an interesting experience. I’m fairly adept at attaching RJ-45 connectors, and can usually attach a cable end in under five minutes. When I attempted to put a connector onto my CAT6 cable though, it took me almost an hour to attach two cable ends. The reason that it took so long was because CAT6 cable is quite a bit thicker than CAT5 cable, and the cable end just didn’t seem to want to fit.

Although that particular cable seemed to work OK, something told me that it just couldn’t be that difficult to attach a cable end. After doing a little research, I discovered that CAT5E and CAT6 cables require a different type of RJ-45 connector than CAT5 does. The wiring sequence is still the same as it was with CAT 5 (orange / white, orange, green / white, blue, blue / white, green, brown / white, brown). The difference is that while a connector for a CAT5 cable holds the individual wires in a straight line, an RJ-45 connector for a CAT6 cable staggers the wires to accommodate their thicker sizes. In practice though, attaching a connector to a CAT6 cable is almost identical to attaching a connector to a CAT5 cable. If you can put a connector onto a CAT5 cable successfully, then you won’t have any trouble with CAT6. You can even continue to use your old crimpier and cable tester.

Network Cards

Obviously, the only way that any of your computers will ever achieve gigabit speeds is if they contain a 10 / 100 / 1000 network card. There really isn’t anything special that you need to know about shopping for network cards other than to go with a reputable brand.

The one thing that I would caution you about is IP addresses. Most networks use primarily dynamically assigned IP addresses, but there are always a few static IP addresses. If you have any computers with static IP addresses, be sure to write the addresses down prior to removing the old network card. When you remove the old network card, Windows no longer displays the address that was assigned to the machine. You will therefore need to know the address so that you can bind it to the new card that you are installing.

Conclusion

Making the transition to gigabit Ethernet can be a lot of work. However, the process tends to be a lot easier if you do your homework ahead of time. This means buying the right components and understanding exactly what you are getting yourself into.