Within a few years of its introduction, 10BASE-T proved inadequate to meet the growing networking demand for speed. As with all things in the computing world, bandwidth is the key. Even with switching, the 10-Mbps speed of 10BASE-T, seemingly so fast when first developed, quickly found a market clamoring for even faster speeds. This chapter looks at the improvements in Ethernet since 10BASE-T. You’ll read about the 100-megabit standards and the Gigabit Ethernet standards. The chapter finishes with a look at Ethernet standards that exceed Gigabit speeds.

Test Specific

100-Megabit Ethernet

The quest to break 10-Mbps network speeds in Ethernet started in the early 1990s. By then, 10BASE-T Ethernet had established itself as the most popular networking technology (although other standards, such as IBM’s Token Ring, still had some market share). The goal was to create a new speed standard that made no changes to the Ethernet frames. By doing this, the 802.3 committee ensured that different speeds of Ethernet could interconnect, assuming you had something that could handle the speed differences and a media converter if the connections differed. This standardization ensures communication and scalability.

100BASE-T

When it came time to come up with a new standard to replace 10BASE-T, network hardware makers forwarded a large number of potential standards, all focused on the prize of leading the new Ethernet standard. As a result, two twisted-pair Ethernet standards appeared: 100BASE-T4 and 100BASE-TX. 100BASE-T4 used Cat 3 cable, whereas 100BASE-TX used Cat 5 and Cat 5e. By the late 1990s, 100BASE-TX became the dominant 100-megabit Ethernet standard. 100BASE-T4 disappeared from the market and today has been forgotten. As a result, we never say 100BASE-TX, simply choosing to use the term 100BASE-T.

100BASE-T Summary

•   Speed  100 Mbps

•   Signal type  Baseband

•   Distance  100 meters between the hub/switch and the node

•   Node limit  No more than 1024 nodes per hub/switch

•   Topology  Star-bus topology: physical star, logical bus

•   Cable type  Cat 5 or better UTP or STP cabling with RJ-45/8P8C connectors

Upgrading a 10BASE-T network to 100BASE-T was not a small process. First, you needed Cat 5 cable or better. Second, you had to replace all 10BASE-T NICs with 100BASE-T NICs. Third, you had to replace the 10BASE-T hub or switch with a 100BASE-T hub or switch. Making this upgrade cost a lot in the early days of 100BASE-T, so people clamored for a way to make the upgrade a little easier and less expensive. This was accomplished via multispeed, auto-sensing NICs and hubs/switches.

Figure 4-1 shows a typical multispeed, auto-sensing 100BASE-T NIC from the late 1990s. When this NIC first connected to a network, it negotiated automatically with the hub or switch to determine the other device’s highest speed. If they both did 100BASE-T, then you got 100BASE-T. If the hub or switch only did 10BASE-T, then the NIC did 10BASE-T. All of this happened automatically (Figure 4-2).

Figure 4-1  PCI 100BASE-T NIC

Figure 4-2  Auto-negotiation in action

Distinguishing a 10BASE-T NIC from a 100BASE-T NIC without close inspection was impossible. You had to look for something on the card to tell you its speed. Some NICs had extra link lights to show the speed (see Chapter 5 for the scoop on link lights). Of course, you could always simply install the card, as shown in Figure 4-3, and see what the operating system says it sees.

Figure 4-3  100BASE-T NIC in Windows 8.1

You’ll also have trouble finding a true 10BASE-T or 100BASE-T NIC any longer because multispeed NICs have been around long enough to have replaced any single-speed NIC. All modern NICs are multispeed and auto-sensing.

100BASE-FX

Most Ethernet networks use unshielded twisted pair (UTP) cabling, but quite a few use fiber-based networks instead. In some networks, using fiber simply makes more sense.

UTP cabling cannot meet the needs of every organization for three key reasons. First, the 100-meter distance limitation of UTP-based networks is inadequate for networks covering large buildings or campuses. Second, UTP’s lack of electrical shielding makes it a poor choice for networks functioning in locations with high levels of electromagnetic interference (EMI)—disturbance in electrical signals caused by electrical radiation coming from nearby devices. Finally, the Jason Bournes and James Bonds of the world find UTP cabling (and copper cabling in general) easy to tap, making it an inappropriate choice for high-security environments. To address these issues, the IEEE 802.3 standard provides for a flavor of 100-megabit Ethernet using fiber-optic cable, called 100BASE-FX.

The 100BASE-FX standard saw quite a bit of interest for years, as it combined the high speed of 100-megabit Ethernet with the reliability of fiber optics. Outwardly, 100BASE-FX looked exactly like its predecessor, 10BASE-FL (introduced in Chapter 3). 100BASE-FX uses multimode fiber-optic cabling, and subscriber connector (SC) or straight tip (ST) connectors. 100BASE-FX offers improved data speeds over 10BASE-FL and equally long cable runs, supporting a maximum cable length of 2 kilometers.

100BASE-FX Summary

•   Speed  100 Mbps

•   Signal type  Baseband

•   Distance  Two kilometers between the hub/switch and the node

•   Node limit  No more than 1024 nodes per hub/switch

•   Topology  Star-bus topology: physical star, logical bus

•   Cable type  Multimode fiber-optic cabling (generally OM1) with ST or SC connectors

100BASE-SX

100BASE-SX was a short-distance, LED-based alternative to 100BASE-FX. It ran on OM1 or OM2 fiber at 850 nm and used ST, SC, or LC connectors. It was completely backwardly compatible to 10BASE-FL, so was touted as a viable upgrade from the even older tech. 100BASE-SX is long gone but appears in the CompTIA Network+ N10-008 objectives for some reason, so I’ve included it here for completeness.

Full-Duplex Ethernet

Early 100BASE-T NICs, just like 10BASE-T NICs, could send and receive data, but not at the same time—a feature called half-duplex (Figure 4-4). The IEEE addressed this characteristic shortly after adopting 100BASE-T as a standard. By the late 1990s, most 100BASE-T cards could auto-negotiate for full-duplex. With full-duplex, a NIC can send and receive at the same time, as shown in Figure 4-5.

Figure 4-4  Half-duplex; sending at the top, receiving at the bottom

Figure 4-5  Full-duplex

All NICs today run full-duplex. The NIC and the attached switch determine full- or half-duplex during the auto-negotiation process. The vast majority of the time you simply let the NIC do its negotiation. Every operating system has some method to force the NIC to a certain speed/duplex, as shown in Figure 4-6.

Figure 4-6  Forcing speed and duplex in Windows 10

Fast Ethernet at 100 Mbps makes sense for local area networks (LANs)—with computers interconnected in a defined space, like a home or office—where you share small data, like documents and spreadsheets. Plenty of LANs around the world continue to soldier on at 100-megabit speeds. A lot of network-connected devices, such as printers, function just fine on Fast Ethernet as well. Still, Fast Ethernet is dead in new installations, so let’s turn to the current standard.

Gigabit Ethernet

By the end of the 1990s, Fast Ethernet was not enough for networking needs. In response, the IEEE created Gigabit Ethernet, which today is the most common type of Ethernet found on new NICs.

The IEEE approved two different versions of Gigabit Ethernet. The most widely implemented solution, published under the IEEE 802.3ab standard, is called 1000BASE-T. The other version, published under the 802.3z standard and known as 1000BASE-X, is divided into a series of standards, with names such as 1000BASE-SX and 1000BASE-LX.

1000BASE-T uses four-pair UTP or STP cabling to achieve gigabit performance. Like 10BASE-T and 100BASE-T, 1000BASE-T has a maximum cable length of 100 meters on a segment. 1000BASE-T connections and ports look exactly like the ones on a 10BASE-T or 100BASE-T network.

The 802.3z standards require a bit more discussion. Let’s look at each of these solutions in detail to see how they work.

1000BASE-SX

Many networks upgrading to Gigabit Ethernet use the 1000BASE-SX standard. 1000BASE-SX uses multimode fiber-optic cabling to connect systems, with a generous maximum cable length of 220 to 500 meters; the exact length is left up to the various manufacturers. 1000BASE-SX uses an 850-nm (nanometer) wavelength LED to transmit light on the fiber-optic cable. 1000BASE-SX devices look similar to 100BASE-FX devices, and although both standards can use several types of connectors, 1000BASE-SX devices commonly use LC, while 100BASE-FX devices frequently use SC. (See “SFF Fiber Connectors” later in the chapter for the scoop on LC connectors.)

1000BASE-LX

1000BASE-LX is the long-distance carrier for Gigabit Ethernet. 1000BASE-LX uses lasers on single-mode cables to shoot data at distances up to 5 kilometers—and some manufacturers use special repeaters to increase that to distances as great as 70 kilometers! The Ethernet folks are trying to position this as the Ethernet backbone of the future, and already some large carriers are beginning to adopt 1000BASE-LX. You may live your whole life and never see a 1000BASE-LX device, but odds are good that you will encounter connections that use such devices in the near future. 1000BASE-LX connectors look like 1000BASE-SX connectors.

SFF Fiber Connectors

Around the time that Gigabit Ethernet first started to appear, two problems began to surface with ST and SC connectors. First, ST connectors are relatively large, twist-on connectors, requiring the installer to twist the cable when inserting or removing it. Twisting is not a popular action with fiber-optic cables, as the delicate fibers may fracture. Also, big-fingered techs have a problem with ST connectors if the connectors are too closely packed: they can’t get their fingers around them.

SC connectors snap in and out, making them much more popular than STs. SC connectors are also large, however, and the folks who make fiber networking equipment wanted to pack more connectors onto their boxes.

This brought about two new types of fiber connectors, known generically as small form factor (SFF) connectors, both of which were introduced in Chapter 2. The first SFF connector—the Mechanical Transfer Registered Jack (MT-RJ), shown in Chapter 2 in Figure 2.25—gained popularity with important companies like Cisco and is still quite common. The second, the local connector (LC), is shown in Figure 4-7. LC-type connectors are very popular, particularly in the United States, and many fiber experts consider the LC-type connector to be the predominant fiber connector.

Figure 4-7  LC-type connector

LC and MT-RJ are the most popular types of SFF fiber connectors, but many others exist. The fiber industry has no standard beyond ST and SC connectors, which means that different makers of fiber equipment may have different connections. Table 4-1 summarizes common Gigabit Ethernet standards.

Table 4-1  Gigabit Ethernet Summary

Mechanical Connection Variations

Aside from the various connection types (LC, MT-RJ, and so on), fiber connectors vary in the connection point. The standard connector type today is called a physical contact (PC) connector because the two pieces of fiber touch when inserted. These connectors replace the older flat-surface connector that left a little gap between the connection points due to imperfections in the glass. PC connectors are highly polished and slightly spherical, reducing the signal loss at the connection point.

Two technologies have dropped in price and have replaced PC connectors in some implementations: UPC and APC. Ultra-physical contact (UPC) connectors are polished extensively for a superior finish. These reduce signal loss significantly over PC connectors. Angled physical contact (APC) connectors add an 8-degree angle to the curved end, lowering signal loss further. Plus, their connection does not degrade from multiple insertions, unlike earlier connection types.

So, note that when you purchase fiber cables today, you’ll see the connector type and the contact type, plus the type of cable and other physical dimensions. A typical patch cable, for example, would be an SC/UPC single-mode fiber of a specific length.

Implementing Multiple Types of Gigabit Ethernet

Because Ethernet frames don’t vary among the many flavors of Ethernet, network hardware manufacturers have long built devices capable of supporting more than one flavor right out of the box.

You can also use dedicated media converters to connect any type of Ethernet cabling together. Most media converters are plain-looking boxes with a port or dongle on either side with placement between two segments. They come in all flavors:

•   Single-mode fiber (SMF) to UTP/STP

•   Multimode fiber (MMF) to UTP/STP

•   Fiber to coaxial

•   SMF to MMF

Eventually, the Gigabit Ethernet folks created a standard for modular ports called a gigabit interface converter (GBIC). With many Gigabit Ethernet switches and other hardware, you can simply pull out a transceiver—the connecting module, commonly referred to as an optic—that supports one flavor of Gigabit Ethernet and plug in another. You can replace an RJ-45 GBIC, for example, with an SC GBIC, and it’ll work just fine. In this kind of scenario, electronically, the switch or other gigabit device is just that—Gigabit Ethernet—so the physical connections don’t matter. Ingenious!

Switches and other network equipment today use a much smaller modular transceiver, called a small form-factor pluggable (SFP). Hot-swappable like the GBIC transceivers, the SFPs take up a lot less space and support all the same networking standards.

Ethernet Evolutions

The vast majority of wired networks today feature Gigabit Ethernet, which seems plenty fast for current networking needs. That has not stopped developers and manufacturers from pushing well beyond those limits. This last section looks at high-speed Ethernet standards: 10/40/100 gigabit.

10 Gigabit Ethernet

Developers continue to refine and increase Ethernet networking speeds, especially in the LAN environment and in backbones. 10 Gigabit Ethernet (10 GbE) offers speeds of up to 10 gigabits per second, as its name indicates.

10 GbE has a number of fiber standards and two copper standards. While designed with fiber optics in mind, copper 10 GbE can still often pair excellent performance with cost savings. As a result, you’ll find a mix of fiber and copper in data centers today.

Fiber-Based 10 GbE

When the IEEE members sat down to formalize specifications on Ethernet running at 10 Gbps, they faced an interesting task in several ways. First, they had to maintain the integrity of the Ethernet frame. Data is king, after all, and the goal was to create a network that could interoperate with any other Ethernet network. Second, they had to figure out how to transfer those frames at such blazing speeds. This second challenge had some interesting ramifications because of two factors. They could use the traditional Physical layer mechanisms defined by the Ethernet standard. But a perfectly usable ~10-Gbps fiber network, called Synchronous Optical Network (SONET), was already in place and being used for wide area networking (WAN) transmissions. What to do?

The IEEE created a whole set of 10 GbE standards that could use traditional LAN Physical layer mechanisms, plus a set of standards that could take advantage of the SONET infrastructure and run over the WAN fiber. To make the 10-Gbps jump as easy as possible, the IEEE also recognized the need for different networking situations. Some implementations require data transfers that can run long distances over single-mode fiber, for example, whereas others can make do with short-distance transfers over multimode fiber. This led to a lot of standards for 10 GbE.

The 10 GbE standards are defined by several factors: the type of fiber used, the wavelength of the laser or lasers, and the Physical layer signaling type. These factors also define the maximum signal distance.

The IEEE uses specific letter codes with the standards to help sort out the differences so you know what you’re implementing or supporting. All the standards have names in the following format: “10GBASE-” followed by two other characters, what I’ll call xy. The x stands for the type of fiber (usually, though not officially) and the wavelength of the laser signal; the y stands for the Physical layer signaling standard. The y code is always either R for LAN-based signaling or W for SONET/WAN-based signaling. The x differs a little more, so let’s take a look.

10GBASE-Sy uses a short-wavelength (850 nm) signal over multimode fiber. The maximum fiber length is 400 meters, although this length will vary depending on the type of multimode fiber used. (OM1 offers a super-short 33 m range, for example, whereas with OM4 the distance extends to 400 m.) 10GBASE-SR is used for Ethernet LANs, and 10GBASE-SW is used to connect to SONET devices.

10GBASE-Ly uses a long-wavelength (1310 nm) signal over single-mode fiber. The maximum fiber length is 10 kilometers, although this length will vary depending on the type of single-mode fiber used. 10GBASE-LR connects to Ethernet LANs and 10GBASE-LW connects to SONET equipment. 10GBASE-LR is the most popular and least expensive 10 GbE media type.

10GBASE-Ey uses an extra-long-wavelength (1550 nm) signal over single-mode fiber. The maximum fiber length is 40 kilometers, although this length will vary depending on the type of single-mode fiber used. 10GBASE-ER works with Ethernet LANs and 10GBASE-EW connects to SONET equipment.

The 10 GbE fiber standards do not define the type of connector to use and instead leave that to manufacturers (see the upcoming section “10 GbE Physical Connections”).

The Other 10 GbE Fiber Standards

Manufacturers have shown both creativity and innovation in taking advantage of both existing fiber and the most cost-effective equipment. This has led to a variety of standards that are not covered by the CompTIA Network+ exam objectives, but that you should know about nevertheless. The top three as of this writing are 10GBASE-L4, 10GBASE-RM, and 10GBASE-ZR.

The 10GBASE-L4 standard uses four lasers at a 1300-nanometer wavelength over legacy fiber. On multimode cable, 10GBASE-L4 can support up to 300-meter transmissions. The range increases to 10 kilometers over single-mode fiber.

The 10GBASE-LRM standard uses the long-wavelength signal of 10GBASE-LR but over legacy multimode fiber. The standard can achieve a range of up to 220 meters, depending on the grade of fiber cable.

Finally, some manufacturers have adopted the 10GBASE-ZR “standard,” which isn’t part of the IEEE standards at all (unlike 10GBASE-L4 and 10GBASE-LRM). Instead, the manufacturers have created their own set of specifications. 10GBASE-ZR networks use a 1550-nanometer wavelength over single-mode fiber to achieve a range of a whopping 80 kilometers. The standard can work with both Ethernet LAN and SONET/WAN infrastructure.

Copper-Based 10 GbE

It took until 2006 for IEEE to come up with a standard for 10 GbE running on twisted pair cabling—called, predictably, 10GBASE-T. 10GBASE-T looks and works exactly like the slower versions of UTP Ethernet. The only downside is that 10GBASE-T running on Cat 6 has a maximum cable length of only 55 meters. The Cat 6a standard enables 10GBASE-T to run at the standard distance of 100 meters.

Table 4-2 summarizes the 10 GbE standards.

Table 4-2  10 GbE Summary

10 GbE Physical Connections

This hodgepodge of 10 GbE types might have been the ultimate disaster for hardware manufacturers. All types of 10 GbE send and receive the same signal; only the physical medium is different. Imagine a single switch that had to come out in seven different versions to match all these types! Instead, the 10 GbE industry simply chose not to define the connector types and devised a very clever, very simple concept called multisource agreements (MSAs): agreements among multiple manufacturers to make interoperable devices and standards. A transceiver based on an MSA plugs into your 10 GbE equipment, enabling you to convert from one media type to another media type.

Characteristics of Fiber Transceivers

Up to this point, the book has described the most common forms of fiber-optic networking, where fiber is installed in pairs, with one cable to send and the other to receive. This is still the most common fiber-based networking solution out there. All the transceivers used in these technologies have two connectors, a standard duplex format. A typical transceiver used in 10 GbE is called the enhanced small form-factor pluggable (SFP+), shown in Figure 4-8.

Figure 4-8  SFP+ transceiver (Photo courtesy of D-Link)

Manufacturers have developed technology that relies on wave division multiplexing (WDM) to differentiate wave signals on a single fiber, creating single strand fiber transmission. Bidirectional (BiDi) transceivers (Figure 4-9) have only a single optical port designed inside to send on one wavelength, such as 1310 nm, and receive on a different wavelength, such as 1550 nm. A corresponding BiDi transceiver must be installed on the other end of the fiber for this to work.

Figure 4-9  BiDi transceiver

BiDi technology has a couple of notable advantages over its dual-fiber predecessors. First, it costs less to deploy in a new network. You can establish the same level of network performance using half the number of fiber runs. Second, you can use existing fiber runs to rapidly double the capacity of a network. Replace the duplex transceivers with twice the number of BiDi transceivers and plug in the fiber.

Gigabit BiDi transceivers typically use SFP optics. Most 10 GbE BiDi transceivers use SFP+ connectors. 40 GbE BiDi transceivers use quad small form-factor pluggable (QSFP) optics.

Backbones

The beauty and the challenge of the vast selection of Ethernet flavors is deciding which one to use in your network. The goal is to give your users the fastest network response time possible while keeping costs reasonable. To achieve this balance, most network administrators find that a multispeed Ethernet network works best. In a multispeed network, a series of high-speed (relative to the rest of the network) switches maintain a backbone network. No computers, other than possibly servers, attach directly to this backbone. Figure 4-10 shows a typical backbone network. Each floor has its own switch that connects to every node on the floor. In turn, each of these switches also has a separate high-speed connection to a main switch that resides in the office’s computer room.

Figure 4-10  Typical network configuration showing backbone (pun intended)

To make this work, you need switches with separate, dedicated, high-speed ports like the ones shown in Figure 4-11. The ports (often fiber) on the switches run straight to the high-speed backbone switch.

Figure 4-11  Switch with dedicated, high-speed ports

Try This!

40 GbE and 100 GbE

Way back in 2010, the IEEE 802.3ba committee approved standards for 40- and 100-Gb Ethernet, 40 Gigabit Ethernet (40 GbE) and 100 Gigabit Ethernet (100 GbE), respectively. Both standards, in their many varieties, use the same frame as the slow-by-comparison earlier versions of Ethernet, so with the right switches, you’ve got perfect interoperability. The 40 GbE and 100 GbE standards are primarily used when lots of bandwidth is needed, such as connecting servers, switches, and routers.

Common 40 GbE runs on OM3 or better multimode fiber, uses laser light, and uses various four-channel connectors. A typical connector is called an enhanced quad small form-factor pluggable (QSFP+), essentially taking four SFP+ transceivers and squashing them into a single, wider transceiver. Other 40 GbE standards run on single-mode fiber and can do distances up to 10 km. Still other 40 GbE connections run on Cat 8 UTP for an underwhelming 30 meters. This is 40GBASE-T and shows up in the CompTIA Network+ objectives.

100 GbE standards employ both MMF and SMF with various connectors. A typical connector is the QSFP28 that has four channels of 25 Gb each. You’ll sometimes see this connector referred to as a QSFP100 or 100G QSFP.

Chapter Review

Questions

1.   With 100BASE-T, what is the maximum distance between the switch and the node?

A.   1000 meters

B.   400 meters

C.   100 meters

D.   150 meters

2.   What type of cable and connector does 100BASE-FX use?

A.   Multimode fiber with ST or SC connectors

B.   STP Cat 6 with RJ-45 connectors

C.   Single-mode fiber with MT-RJ connectors

D.   UTP Cat 5e with RJ-45 connectors

3.   Which of the following connector would you typically find with a 40 GbE installation?

A.   LC

B.   SFP

C.   QSFP+

D.   XSFP+

4.   What standard does IEEE 802.3ab describe?

A.   1000BASE-LX

B.   1000BASE-T

C.   100BASE-T

D.   1000BASE-SX

5.   What is the big physical difference between 1000BASE-SX and 100BASE-FX?

A.   1000BASE-SX commonly uses the LC connector, whereas 100BASE-FX frequently uses the SC connector.

B.   1000BASE-SX is single-mode, whereas 100BASE-FX is multimode.

C.   1000BASE-SX uses the ST connector exclusively.

D.   There is no difference.

6.   What is the maximum distance for 1000BASE-LX without repeaters?

A.   1 mile

B.   2500 meters

C.   20,000 feet

D.   5000 meters

7.   What is a big advantage to using fiber-optic cable?

A.   Fiber is common glass; therefore, it’s less expensive.

B.   Fiber is not affected by EMI.

C.   Making custom cable lengths is easier with fiber.

D.   All that orange fiber looks impressive in the network closet.

8.   How many wire pairs does 1000BASE-T use?

A.   1

B.   2

C.   3

D.   4

9.   What is the standard connector for the 10 GbE fiber standard?

A.   ST

B.   SC

C.   MT-RJ

D.   There is no standard.

10.   What is the maximum cable length of 10GBASE-T on Cat 6?

A.   55 meters

B.   100 meters

C.   20 meters

D.   70 meters

Answers

1.   C. The maximum distance is 100 meters.

2.   A. 100BASE-FX uses multimode fiber with either ST or SC connectors.

3.   C. 40 GbE installations over fiber typically use QSFP+ connectors.

4.   B. IEEE 802.3ab is the 1000BASE-T standard (also known as Gigabit Ethernet).

5.   A. While 1000BASE-SX looks similar to 100BASE-FX, the former commonly uses the LC connector; the latter frequently uses the SC connector.

6.   D. 1000BASE-LX can go for 5000 meters (5 kilometers).

7.   B. Because fiber uses glass and light, it is not affected by EMI.

8.   D. 1000BASE-T uses all four pairs of wires.

9.   D. There is no standard connector; the 10 GbE committee has left this up to the manufacturers.

10.   A. With Cat 6 cable, 10GBASE-T is limited to 55 meters.