CHAPTER 51. Upgrading Older Ethernet Networks

SOME OF THE MAIN TOPICS IN THIS CHAPTER ARE

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Upgrading from 10BASE-2 or 10BASE-T 964

Hardware and Software Factors to Consider for 10BASE-2, 10BASE-T, and 100BASE-T 965

Connecting Networks That Use Different Cables or Topologies 970

Other Possibilities 970

Upgrading the Network Backbone to Gigabit Ethernet 971

Using Gigabit Ethernet for High-End Servers 971

Gigabit Ethernet Can Cover the Distance 972

10 Gigabit Ethernet Is Becoming Economically Feasible 972

At the end of the day, what makes the task of installing a network a timely and costly one is really just pulling network cables. You not only have to make sure that you meet local building codes, but you also must spend many hours (and labor is expensive) in dropping cables so that you can install a faceplate at the user’s cubicle or office. Cables also need to be laid out without interference from other energy sources and adhere to the recommended distance limitations depending on the type of cable.

The original Ethernet specifications used coaxial cabling instead of twisted-pair wiring or fiber-optic cables. If you’re still using older network technologies, it might be time to upgrade. Don’t get me wrong: If you have a specialized environment, such as automation control on a factory floor, you might not need to upgrade this type of network because data transfers will be miniscule when compared to an office network. However, this chapter assumes that you have an office network, which can eat up network bandwidth at tremendous rates. Not only do you have to provide file servers for such mundane tasks as word processing and other data files, but newer applications such as live video streaming can send 10BASE-2 and 100BASE-T networks to the history pile.

Older 10BASE-5 networks used a coaxial cable (referred to by those in the field as thicknet) as a backbone, and tapped into this cable (using what is popularly called a vampire tap) to drop a smaller coaxial cable such as 10BASE-2 (again with a nickname, thinnet) to each user’s workstation. In an office environment, this type of network is untenable today. Worker productivity is measured in hourly costs. Even a few minutes downloading a document from a file server or creating a report based on data on a remote server costs you money. For an office network, it’s time to upgrade.

The topic of this chapter is the office LAN and network enterprise network. Newer applications, from video conferencing to employees who like to waste time browsing through the Internet, require much more bandwidth than older Ethernet technologies such as 10BASE-2 can provide.

Upgrading from 10BASE-2 or 10BASE-T

Twisted-pair wiring pretty much replaced 10BASE-2 many years ago and was, for a long time, the networking solution of choice. Hubs allowed for centralization of wiring and switches helped localize errors due to faulty cables or network adapter cards.

100BASE-T and gigabit Ethernet solutions are now the de facto standards for creating a new network. If you’re creating a network from scratch, it’s best to start with the latest and greatest if your budget allows.

Like 10BASE-2 networks, you should ask yourself why you would even want to operate a 10BASE-T network. If you already have one in place, continuing to add new hubs, switches, and routers may make sense, provided this limited bandwidth (10Mbps) can satisfy the demands of your users/applications. However, 100BASE-T (also known as Fast Ethernet) has been around for more than 5 years, and is now the most widely used version of Ethernet between the wiring closet and the user desktop.

For more information about network topologies and how the physical network should be laid out, see Chapter 3, “Network Design Strategies.”

For this reason, this chapter skips upgrading from 10BASE-2 to 10BASE-T because such an upgrade really isn’t a good investment. If you’re going to swallow the expense of pulling new cabling to replace older coaxial cabling, there’s no reason to go to 10BASE-T today. Category 5 (and above) cabling can handle both, and almost every network adapter card produced today can operate at 10Mbps as well as 100Mbps. After you’ve upgraded the cable plant, you might as well go for the added bandwidth of 100Mbps instead.

The rest of this chapter quickly looks at some of the things to consider when planning to replace an older Ethernet network with more modern technology.

Hardware and Software Factors to Consider for 10BASE-2, 10BASE-T, and 100BASE-T

Obviously, it’s the hardware that you’ll have to replace when making this kind of upgrade. Network protocols, such as TCP/IP, don’t care what the underlying physical network is made up of as long as they can get data segments from one place to another. However, you might still be using older software, and if so, you might want to consider upgrading it in addition to the hardware when you plan for this kind of upgrade. As discussed in other parts of this book, Novell’s NetWare has basically lost the LAN environment to Unix and Windows NT/2000 and Windows 2003 servers, much less the Windows XP client, and even the most recent versions of NetWare can use IP. For NetWare 6.X, IP is the main protocol, given the emphasis that Novell now puts on Internet access. For the network that you use, whether it be a built-in technology as with Windows or Unix/Linux or an add-on product such as NetWare, the IP protocol remains an underlying factor.

For a historical overview, 10BASE-2 and 10BASE-T have more differences than just the type of cables they use. Although both of them use the same messaging technique (CSMA/CD), their topologies are basically different: 10BASE-2 uses a bus topology, whereas 10BASE-T (and 100BASE-T) installations use a star topology, implemented by a switch, although you might find an older hub still being used. The distances that can be covered by cable segments are also different. The network adapters transmit signals at different speeds. When preparing for an upgrade, check your network inventory to determine which parts of the hardware you’ll have to upgrade in addition to the cabling. The major considerations that need to be researched when upgrading from 10BASE-2 to a twisted-pair network are as follows:

Network cables—The fundamental difference between 10BASE-2 and 10BASE-T/100BASE-T is the move from coaxial cable to twisted-pair wiring, usually Category 5 cables, although newer cabling is now being deployed.

For more about cables and other relevant components, refer to Chapter 6, “Wiring the Network—Cables, Connectors, Concentrators, and Other Network Components.”

Network topology—You’ll be going from a linear bus topology to a star topology. The distances covered by 10BASE-T/100BASET are shorter than those allowed using 10BASE-2. But because of the star topology and the uses of switches, you’ll actually find it easier to greatly extend the reach of your network.

Network adapters—Older network adapters might have only a BNC connector on them. You’ll need cards that provide an RJ-45 jack for 10BASE-T or 100BASE-T. This connector looks much like an ordinary telephone jack, but is slightly larger.

Network cable connectors—Instead of BNC connectors, twisted-pair cabling uses RJ-45 connectors.

Hubs and switches—Although a 10BASE-2 network allows you to use multiport repeaters, no central wiring devices are actually required. For a 10BASE-T/100BASE-T network, you need (at a minimum) a hub to act as a wiring concentrator. Although a lone hub might suffice for a small network with a limited number of users, you should really consider using switches instead because they enable you to further extend the distances covered by a LAN. And it is very unlikely you’ll find a hub for sale today.

To learn more about how hubs and switches function, see “Bridges, Repeaters, and Hubs,” on the upgradingandrepairingpcs.com Web site and Chapter 8, “Network Switches.”

For example, if you’re using a multiport repeater, replacing it with a more functional hub or switch seemed a natural thing to do a few years ago. However, remember that the topology rules for 10BASE-2 and 10BASE-T networks specify different maximum cable segment lengths, so you might have to relocate wiring closets or make other accommodations if your current distances are too long:

Maximum segment length for 10BASE-2: 185 meters

Maximum segment length for 10BASE-T/100BASE-T: 100 meters

Maximum number of devices on a 10BASE-2 hub segment: 30

Maximum number of devices on a 10BASE-T/100BASE-T hub segment: 2 (but one of these is the hub, so effectively, just 1)

Chapter 13, “Ethernet: The Universal Standard,” covers in more detail the different cabling distances you’ll need to consider.

Today, however, using switching technology to replace hubs is about the only option you have today. As stated earlier, you’ll find it difficult, if not impossible, to find a hub on the market today. They are legacy devices. If you’re going to upgrade your network, consider a switch to be a hub replacement. That doesn’t mean you need to discard hubs in small segments of your LAN if you already have them. Indeed, if you connect a few computers that have minimal bandwidth requirements to your LAN, there’s really no need to replace a hub with a switch. It all depends on how your users make use of the network. If no one is complaining with a hub connection (which you’ll most likely have connected to a switch upstream), don’t worry about replacing it. Today it’s usually the applications that drive the need for additional network bandwidth. If it’s working now and no one is complaining, don’t change it.

The main consideration here is the topology requirements used for earlier Ethernet networks. If the cable doesn’t provide the distance or bandwidth requirements you need today, you’ll have to replace the cabling to accommodate modern networks. In a small LAN environment, this usually isn’t the case. In a larger environment, you might have to replace cabling to reach the distances you need, yet still provide the same bandwidth that older equipment (such as hubs) can give to users.

Network Cables

Because 10BASE-2 uses thinnet coaxial cabling, the first upgrade issue you must address is getting the appropriate network cabling.

This should be the simplest decision you have to make. Although it’s quite possible to use Category 3 wiring to construct a 10BASE-T (and even a 100BASE-T) network, the only good reason I can think of to do so would be that you already have the wiring in place and can use it with few modifications. Other than that, if you’re going to install a 100BASE-T network to replace a network based on coaxial cables, you would be better served to go ahead and use Category 5 cabling or better. Why? Further down the road you might find yourself upgrading to Gigabit Ethernet or even 10 Gigabit Ethernet.

Both of these technologies require Category 5 cables or higher. Although it might seem like Gigabit Ethernet is something that’s far in the future, keep in mind that many network administrators didn’t think that video on demand would be a requirement today. It’s easy to underestimate the network bandwidth that you’ll need for future requirements. And because installing the cabling is one of the most labor-intensive (and thus expensive) components of a network upgrade, I recommend that when you decide to upgrade cabling, you go for the latest to protect your investment farther into the future. Indeed, I’d say that your network backbone should already consist of fiber-optic cabling because Gigabit and the newly ratified standard for 10 Gigabit Ethernet operate best using these cables. Both can use ordinary copper cables, but only for very short distances—usually in the wiring closet.

The amount of cable you need might work out to be a lot more than you used for the 10BASE-2 network. Remember that in the bus topology that thinnet (coaxial) networks such as 10BASE-2 use, you can daisy chain one workstation to another using a linear bus. A 50-ohm terminator terminates each end of the bus. The total amount of cable needed is simply the sum of all the cables that are daisy chained together. When using a hub or switch, you can have two workstations sitting right next to each other, both having a 100-meter twisted-wire cable going back to the hub. Because of this, the total amount of cabling you’ll need is generally a lot more than you did when you installed 10BASE-2 technology. Yet consider that the cost of twisted-pair wiring is now a lot less expensive that it used to be. The economies of scale always provide for this.

If you instead use a multiport repeater on an existing 10BASE-2 network, and if only one computer is attached to each port, you’ll find that replacing the cables is a simple matter of stringing Category 5 (or greater) cables through the same route used by the current coaxial cables. Then all you need to do is replace the repeater with a switch. If you have segments on a multiport repeater that have more than one computer attached, you’ll have to plug each computer into a separate port on a switch. Another possibility is to place these computers on a separate switch and connect it to the network backbone.

Because you must string cable from a central location to each workstation, you need to have a place you can use as a wiring closet to store the switch and any other interconnecting equipment used to join the LAN to a larger network. Again, if you were using a multiport repeater in your 10BASE-2 network, all you need to do after stringing the cables is to replace the multiport repeater with a switch. Also keep in mind that if you’re simply upgrading a small office LAN (5–10 computers), you can use an inexpensive off-the-shelf switch from your local computer store and simply place it out of the way somewhere convenient in the office.

For all practical purposes, consider making backbone connections using fiber-optic cabling. Doing so will give you a much faster connection between LANs today and better prepare you for the future. Keep in mind that the old 80%/20% rule no longer applies. This rule stated that 80% of network traffic remained in the local LAN and 20% was sent to another segment of the LAN. Today, it’s more typical to centralize large servers in a computer room and keep LANs separated by switches. Because computers on the LAN need to access these servers, and they might be separated by multiple switches or even routers, you should consider the 80%/20% rule to be reversed. Now 80% of network traffic is directed outside of the local LAN.

Network Interface Card (NIC)

If you had the foresight to purchase the kind of network adapter cards called combo cards, which have connectors compatible with both BNC connectors and RJ-45 connectors (see Figure 51.1), this is one piece of hardware you might not necessarily have to replace unless the card is too old to use speeds past 10Mbps. The minimum requirement for the NIC is that it have a receptacle to which you can plug in the RJ-45 connector end of the cable to connect the adapter to a hub. However, if you plan to incorporate switches into the network and want servers to use full-duplex connections, you’ll probably have to get a newer card for these computers (most older cards supported only 10Mbps and not 100Mbps). Older combo cards enabled you to upgrade from BNC connectors (used by 10BASE-2) to 10BASE-T. Newer cards use the standard RJ-45 jack and allow for 10/100Mbs communications. And today, most of these cards support auto-negotiation and Wake on LAN (WOL) technologies. So, if you’re still using combo cards, you can continue to use them, but will most likely be limited to a 10Mbps bandwidth on the network for the workstations that use them.

Figure 51.1. A combo card contains connectors for both thinnet coaxial cables (BNC connectors) and a receptacle for an RJ-45 jack used with twisted-pair wiring.

To learn about the latest developments in network adapter cards, including technologies such as auto-negotiation, WOL, and even newer stuff such as PC Cards and wireless network adapters, refer to Chapter 7, “Network Interface Cards.”

If you’re going to have to upgrade a large number of workstations to newer NICs, think carefully about the future when you make this purchase. No matter what your budget is, there’s absolutely no reason to buy a 10Mbps network card, if you can still find one. At the bare minimum, a 10/100Mbps card that can support your older network as well as Fast Ethernet is the best choice to make. Why? Because the price of network adapter cards has fallen so low that you can now find 10/100Mbps cards (depending on the features they support) for less than $20–$30, and for even less at some computer stores and online retailers. If you purchase in quantity from a catalog reseller, you might even find greater reductions in price. Network adapter cards in this range are now commodity items. You can even buy them at department stores such as Wal-Mart.

Network Cable Connectors

As already pointed out earlier in this chapter, a 10BASE-2 network uses a different kind of connector than a 10BASE-T/100BASE-T network does. You should pay attention to the details when ordering connectors (if you plan to make cables yourself) or when ordering ready-made cables that have the connectors attached. When upgrading to twisted-pair wiring, I’ve already suggested that you use Category 5 cabling (or greater) instead of a less capable variety, such as Category 3. This enables you to use the cabling later when you decide it’s time to install 100Mbps segments on part or all or part of the network. Keep in mind that Gigabit Ethernet adapters are already available and the standard for 10 Gigabit Ethernet has just been approved. Although you might not find these speeds required for a workstation connection, they will probably figure into server and backbone connections in just a few years or even less. And because predictions of this sort tend to be conservative, think proactively and investigate the costs of these cards and the switches/routers that support them! Better to pay the more expensive up-front cost now than have to switch out a lot of cards at a lower price in the future.

Connectors, like cables, can exhibit different performance characteristics depending on how they’re manufactured. Be sure that the RJ-45 connectors you choose are compliant with the specifications for Category 5 cables. Inferior connectors can cause a lot of trouble later (such as noise or near-end crosstalk), causing you to spend a lot of time troubleshooting. When constructing your own cables, be sure that you follow the specifications when attaching the jacks to the cables. Many noisy cables are created simply because too much wire is left exposed at the end of the cable where the cable is attached to the connector.

In Chapter 6, “Wiring the Network—Cables, Connectors, Concentrators, and Other Network Components,” you’ll find more information about cables and connectors and the problems you can encounter when they aren’t manufactured correctly.

Bridges, Hubs, Repeaters, and Switches

To extend the length of a LAN based on 10BASE-2 technology, the standard technique is to attach multiple segments with a bridge or a multiport repeater. A repeater works similar to a hub: It simply makes one large broadcast domain out of the various cable segments that are connected to it. A bridge connects two segments, but is capable of learning MAC addresses. Therefore, a bridge can reduce traffic by passing on frames to segments only if their destination isn’t on the local segment from which they originate.

You can use bridges on a 100BASE-T network for the same purposes you would use them in 10BASE-2. They can group similar users on local segments, reduce traffic on individual segments, and extend the length of the local area network. Bridges can perform other functions related to performance as well, such as discarding packets with errors and reducing noise. Newer layer 3 switches accomplish much of the same function by reducing traffic between segments and between specific ports on the switch. Since the previous edition of this book was published, the price of switches has decreased dramatically. Because of this, and its superior performance capabilities on anything but a very small network, I advise using a switch rather than a hub. Hubs should be considered to be legacy devices. You probably won’t be able to find hubs on sale anymore because switches have replaced them and offer much better performance.

Network applications are becoming more data intensive than ever before as computers become faster and more memory is added. A switch creates a small collision domain (that is, just the switch and the computer attached to a switch port) and can drastically reduce network congestion.

Also, in anything but a small network, you might need to use more than one switch to connect user workstations to the network. If you’re planning ahead for a future migration to 100Mbps networking, you’ll find that a multitude of switches operate at both 10Mbps and 100Mbs. Look at the cost difference and decide whether making an investment in a 10/100Mbps device now will save you money in the future. Most switches support both speeds, as well as auto-negotiation to determine what types of devices are attached to each port.

A more important factor to consider when evaluating a switch is to find out whether it comes with management software that’s compliant with SNMP and RMON standards. Check to find out whether each port can be set to a different speed. If it can, make sure that you know whether it’s autosensing or if you must manually set it to operate at one speed or the other.

The Simple Network Management Protocol (SNMP) and RMON (Remote Monitoring) are discussed in detail in Chapter 49, “Network Testing and Analysis Tools.”

If your existing network already uses a router to connect to a larger network, be sure that the hub or switch has a receptacle that can be used for the router connection. Most routers made today accept cables terminated with several different kinds of connectors, even 10BASE-2, so this probably won’t be a problem. However, you should check this as you do all aspects of the network when making an upgrade plan. Note also that the connection between the switch and a router might need to provide for a larger bandwidth than the connection from the switch to the user’s desktop. Although 10Mbps or 100Mbps might be suitable for some end-user applications, when you aggregate this bandwidth and add up the amount of network traffic that will be needed on the entire network, you might want to consider a switch that can use a faster connection—such as fiber-optic cables—when it connects to another hub or a router.

For more information about using routers to join individual network subnets, refer to Chapter 10, “Routers,” and Chapter 33, “Routing Protocols.”

Connecting Networks That Use Different Cables or Topologies

Because switches, like routers, can be found with different kinds of ports that are used to link them (uplink ports), it’s possible that you can incrementally upgrade your network, depending on such factors as the size of the broadcast domain and the number of users on each network segment. For example, you might want to replace one multiport repeater with a hub or switch in one department, while leaving another existing multiport repeater in place for a while.

If you need to maintain backward compatibility by keeping a multiport repeater on the network for a while during the upgrade process, you can use a hub or switch that has a BNC port and connect the two using thinwire Ethernet cables. Or you can connect each of these two devices to separate ports on a router, and create different subnets on your network.

Subnets, and how to calculate subnet addresses and subnet masks, are covered in Chapter 13, “Ethernet: The Universal Standard.”

Other Possibilities

This chapter covered the basic components that you need to change when converting a network from 10BASE-2 to 10BASE-T and 100BASE-T, which are the most prevalent network standards in place today. However, in addition to the cables, connectors, network adapters, and other devices, a change such as this one might warrant further research into the larger network to which you’re connected. In many cases, the local LAN is in reality part of a much larger network. When you have resources that are frequently accessed and lie outside the local LAN, you might need to look at the big picture when making decisions about the local area network. Consider the following:

Do you need to replace the equipment that has been used to connect to the larger network?

Are you currently using a bridge that can be replaced by a switch to improve performance?

Do you have multiple small LANs that can now be merged into a single larger LAN connected by multiple switches?

Upgrading the Network Backbone to Gigabit Ethernet

Today Gigabit Ethernet has arrived, in a big way. You won’t find many people using Gigabit to the desktop yet (although in some high-end environments, such as video production, you just might). But as a backbone transport, Gigabit is an ideal replacement for Fast Ethernet or other protocols used to transfer high-bandwidth traffic.

The initial cost for implementing Gigabit Ethernet as a backbone transport doesn’t have to be a large expense. Consider what happens when you replace local switches and network adapter cards—a large expense can be involved due to the high number of workstations and switch ports required.

However, if you’re replacing a switch that consolidates traffic from these existing switches, you have only to replace these switches and possibly the cabling between these switches. Consider the collapsed backbone topology discussed in Chapter 2, “Overview of Network Topologies.” You don’t replace every departmental LAN switch. Instead, a collapsed backbone means that department level switches all feedback to a single larger switch that controls traffic between each of the departmental switches. So, if the departmental switches satisfy your users’ needs, you’d have to replace only the central switch that connects them. Gigabit (and now 10 Gigabit Ethernet) is ideal for network backbone transport. You can use this technology to connect backbone switches to others in different buildings in a campus environment, and further localize network traffic. It will still be a few years before it’s used to the desktop.

Using Gigabit Ethernet for High-End Servers

Another upgrade you might want to perform using Gigabit or 10 Gigabit Ethernet is for server connections. A single file server connected to a switch can be limited by the total bandwidth of all the workstations that connect to it through a single switch or a cascade of switches. For a high-end server, the CPU(s) and disk array (which could even be a fast storage area network) might not be the bottleneck where performance is concerned. Instead, you might find that you need to use multiple network adapter cards and make several connections between the switch and the server. Whether or not this is the situation, upgrading the server by using Gigabit Ethernet cards can dramatically increase performance. The switch can perform buffering between lower-bandwidth workstations and the server that’s now equipped with much faster adapter cards.

A good way to determine whether the network card is the bottleneck is to use a good network analyzer to determine the utilization of the connection between the computer and the switch. If it’s approaching 80% (in a full-duplex connection), you should definitely consider replacing the network card.

The other component you’ll have to replace is the switch to one that supports Gigabit Ethernet. That doesn’t mean you have to replace any downstream switches because they will feed into the new switch, with network traffic being funneled into the server by the new switch that supports both Gigabit Ethernet as well as Fast Ethernet ports for connections to the other switches or workstations.

Gigabit Ethernet to the Desktop?

Ethernet adapters that you can use in desktop workstations are available now. However, there’s no reason to consider placing them into a typical user’s workstation. Unless you also replace the switches between the workstation and the server(s) it uses, the switches that lie in between become a limiting factor.

But if your business involves such things as video editing or other high-end graphics applications, swapping out old adapter cards and switches might be a good idea. The main thing to consider here is whether the workstation can handle the Gigabit Ethernet bandwidth that the adapter provides. Again, use performance monitoring to be sure that the TCP/IP stack or the CPU of the workstation is not a limiting factor that makes the Gigabit Ethernet card merely something to talk about. If the workstation can’t process the bandwidth that the card can deliver, you’re wasting money! Use the cash in other parts of the network (such as the backbone)!

Gigabit Ethernet Can Cover the Distance

One of the main reasons for replacing network backbone segments with Gigabit Ethernet (and 10 Gigabit Ethernet) network adapters and switches is that the backbone carries a much larger amount of network traffic today than departmental switches do. Each local LAN switch merely needs to make connections for workstations that probably use very little of the 100Mbps bandwidth for the majority of the time. Yes, when you’re using FTP to download a file from a remote server, it can be frustrating because of the time involved. But if most of the work performed on the server falls into the typical office scenario type of work (word processing, spreadsheets, presentations), the network bandwidth usage is sporadic and you don’t need to use Gigabit Ethernet to make a connection to the network for this type of workstation.

However, when you consider consolidating network traffic from hundreds, if not thousands of workstations and the file and print servers they use, Gigabit Ethernet (and now 10 Gigabit Ethernet) is a viable solution. First, the technology provides a much faster bandwidth. Second, when using fiber-optic cabling (copper cabling is pretty much confined to the wiring closet for these technologies), the distances you can cover are measured in kilometers instead of meters. You might find that you can connect buildings that are much farther apart without having to use an intermediary switch or router due to the distance that Gigabit Ethernet technologies can cover. For example, when using single-mode fiber optic cabling with a 1300-nanometer laser, you can cover distances of at least 10 kilometers.

10 Gigabit Ethernet Is Becoming Economically Feasible

The standard for 10 Gigabit Ethernet was finalized in 2002. Just as Gigabit Ethernet equipment is now available that conforms to the established standards. In 2002, the 10 Gigabit Ethernet was finished. For this reason it might be considered as a replacement for older backbone technologies mentioned earlier in this chapter. Gigabit Ethernet is the more cost-effective technology today.