Teaching Tip The short paragraph in the opening page of this chapter contains a bit of historical information as a bridge between the previous chapter, which detailed the earliest versions of Ethernet, and this chapter, which follows Ethernet developments from the 1990s to the present. This entire chapter is Test Specific. It would be very easy for students to lose their way amidst the long list of standards with very similar names. Use the bulleted facts presented in the beginning to point out what is common among Ethernet standards. Then, point out the several small tables throughout the chapter that summarize the features of each Ethernet standard. Lab 5.3 at the end of the book chapter has the students create a comparison chart of all the standards described. Building that comparison chart will be a great way to review all the standards in preparation for the exam. If a student is not taking the exam, the chart will still be a practical job aid.
Teaching Tip These are continued on a second slide. Take time to go over these facts , common to all version of Ethernet. This chapter gives the students a great deal of basic data on the various modern Ethernet standards. Understanding the commonalities will help them understand the differences.
Teaching Tip Per the Cross Check on Page 81, take the time to have the students review the difference between an Ethernet hub and an Ethernet switch. They learned this in Chapter 4, Ethernet Basics.
Teaching Tip Point out the note on the bottom of Page 81, explaining that the term Fast Ether net , originally coined for 100BaseT, is still used to refer to any of the 100-Mbps standards, including 100BaseFX. In general, it is not used to refer to the even faster versions of Ethernet available today.
Teaching Tip Point out the Note on bottom of Page 84: Full-duplex doesn’t increase the speed of the network, but it doubles the bandwidth. Imagine a one-lane road expanded to two lanes while keeping the speed limit the same.
Note: There is an upcoming section titled 10-GbE Physical Connections.
Networking Chapter 5
Modern Ethernet Chapter 5
Objectives• Describe the varieties of 100-megabit Ethernet• Discuss copper- and fiber-based Gigabit Ethernet• Compare the competing varieties of 10- Gigabit Ethernet
Three Parts to Chapter 5• 100-megabit Ethernet standards• Gigabit Ethernet standards• 10-Gigabit Ethernet standards
Ethernet Facts• There are only four Ethernet speeds: 10 mega- bit, 100 megabit, 1 gigabit, and 10 gigabit• Every version of Ethernet uses either unshield- ed twisted pair (UTP) or fiber-optic. (With a few, rare exceptions)• Every version of Ethernet uses a hub or switch, although hubs are incredibly rare today.
Ethernet Facts (continued)• Only 10- and 100-megabit Ethernet may use a hub. Gigabit and 10-Gigabit Ethernet networks must use a switch.• Every version of Ethernet has a limit of 1024 nodes.• Every UTP version of Ethernet has a maximum distance from the switch or hub to the node of 100 meters.
• 100BaseT – 100BaseT4 • CAT 3 or better cabling • Uses all four pair of wires • Disappeared from the market after 100BaseTX generally accepted – 100BaseTX • Dominant 100-megabit standard by the late 1990s • The term “100BaseT” now applies to this standard
• 100BaseTX Summary – Speed: 100 Mbps – Signal type: Baseband – Distance: 100 meters between the hub and the node – Node limit: No more than 1,024 nodes per hub – Topology: Star bus topology: physical star, logical bus – Cable type: Uses CAT5(e) or better UTP cabling with RJ-45 connectors
• Upgrading 10BaseT network to 100BaseT – CAT 5 cable or better – Replace all old 10BaseT NICs with 100BaseT NICs – Replace 10BaseT hubs or switches with 100BaseT hubs or switches – Multispeed, auto-sending NICs and hubs/switches ease the upgrade
• Multispeed, autosensing NIC – When first connected, it negotiates automatically with the hub or switch – If both do 100BaseT, they will use that mode – If the hub/switch only does 10BaseT, NIC does 10BaseT
• 100BaseFX – UTP versus fiber-optic • UTP cannot meet the needs of every organization – 100-meter distance limit inadequate for large buildings and campuses – Lack of electrical shielding – Easy to tap – Fast Ethernet refers to all the 100-Mbps Ethernet standards
• 100BaseFX Summary – Speed: 100 Mbps – Signal type: Baseband – Distance: Two kilometers between hub and node – Node limit: No more than 1,024 nodes per hub – Topology: Star bus topology: physical star, logical bus – Cable type: Uses multimode fiber cabling with ST or SC connectors
• Full-Duplex Ethernet – Early 100BaseT NICs were half-duplex • Could both send and receive data • But not at the same time – IEEE added full-duplex to the standard • Device sends and receives at the same time • By late 1990s, most 100BaseT cards could auto-negotiate for full-duplex – NIC and hub/switch determine full-or-half duplex – Setting can be forced through the operating system
Figure 5.4 Half-duplex; sending at the top, receiving at the bottom
• IEEE 802.3z (continued) – 1000BaseSX • More common • Multimode fiber-optic cable • Maximum cable length 200 to 500 meters, depending on manufacturer • Uses 850-nm wavelength LED • Devices look exactly like 100BaseFX products • SC is the most common type of connection
• IEEE 802.3z (continued) – 1000BaseLX • Long distance carrier • Single-mode (laser) cables • Maximum cable length 5 kilometers • Special repeaters increase distance to 70 kilometers! • Positioned as the Ethernet backbone of the future • Connectors look like 100BaseSX connectors
• New Fiber Connectors – Problems with ST and SC connectors • ST connectors are large, twist-on • Installer must twist cable—danger of fracturing fibers • Techs have trouble getting fingers around closely packed connectors • SC connectors snap in and out, but are also large • Manufacturers wanted smaller connectors for more ports
• New Fiber Connectors (continued) – Solution: Small Form Factor (SFF) connectors • Mechanical Transfer Registered Jack (MT-RJ) • Local Connector (LC) – Very popular – Considered the predominant fiber connector • Other fiber connectors exist • Only standards are ST and SC • Manufacturers have different connectors
• Introduction to 10-Gigabit Ethernet (10- GbE) – Showing up in high-level LANs – Expected to trickle down to the desktops in near future – New technology – Large number of fiber standards – Two copper standards – 10-GbE copper product available only since 2008
• Fiber-base 10-GbE – IEEE challenge • Maintain the integrity of Ethernet frame • How to transfer frames at high speeds – Could use traditional Ethernet Physical layer mechanisms – Already a usable ~10 GbE fiber network (SONET) used for WANs
• Fiber-base 10 GbE (continued) – IEEE Actions • A set of 10GbE standards using traditional LAN Physical-layer mechanisms • A set of 10 GbE standards using SONET infrastructure over WAN fiber • Recognized need for different networking situations
• IEEE created several standards defined by – The type of fiber used – The wavelength of the laser or lasers – The Physical layer signaling type – Maximum signal distance (defined by previous factors)
• Naming convention begins with 10GBasexy – x = type of fiber (usually) and the signal wavelength – y = Physical layer signaling standard • R for LAN-based signaling • W for SONET/WAN-based signaling
• 10GBaseSy uses a short-wavelength (850 nm) signal over multimodeStandard Fiber Type Wavelength Physical Maximum Layer Signal Signaling Length10GBaseSR Multimode 850 nm LAN 26-300 m10GBaseSW Multimode 850 nm SONET/WAN 26-300 m Fiber-based 10GBaseSy Summary
Figure 5.10 A 10GBaseSR NIC (photo courtesy of Intel Corporation)
• 10GBaseLy uses a long-wavelength (1310 nm) signal over single-modeStandard Fiber Type Wavelength Physical Maximum Layer Signal Signaling Length10GBaseLR Single-mode 1310 nm LAN 10 km10GBaseLW Single-mode 1310 nm SONET/WAN 10 km Fiber-based 10GBaseLy Summary
• 10GBaseEy uses an extra-long-wave- length (1550 nm) signal over single- mode fiberStandard Fiber Type Wavelength Physical Maximum Layer Signal Signaling Length10GBaseER Single-mode 1550nm LAN 40 km10GBaseEW Single-mode 1550 nm SONET/WAN 40 km Fiber-based 10GBaseEy Summary
• 10 GbE connectors – Standards do not define the type of connector – Manufacturers determine connectors
• Copper-based 10GbE (10GBaseT) – 2006: IEEE standard for 10GbE running on UTP – Looks and works like slower versions of UTP Ethernet – Downside: 10GBaseT running on CAT 6 has maximum cable length of only 55 meters – 10GBaseT running on CAT 6a can to go to 100 meters
Table 5.2 10-GbE Summary Wavelength / Standard Cabling Cable Details Connectors Length 10GBaseSR Multimode 850 nm Not defined 26 – 300 m /SW fiber 10GBaseLR Single- 1310 nm Variable – LC 10 km /LW mode fiber is common 10GBaseER Single- 1550 nm Variable – LC, 40 km mode fiber SC are common 10GBaseT CAT 6/6a Four-pair / RJ-45 55 – 100 m UTP full-duplex
• 10-GbE Physical Connections – Hodgepodge of 10-GbE types – Problem: single router may need to support several connector types – Solution: multisource agreement (MSA) • Modular transceiver plugs into10-GbE equipment • Converts between media types • Many competing media types recently – 10-GbE equipment exclusive domain of high- bandwidth LANs and WANs, including the Internet
• Backbones – Multispeed network works best for many situations – Series of high-speed switches create a backbone • No computers (except maybe servers) on the backbone • Each floor has its own switch connecting to every node on floor • Each floor switch has a separate high-speed connection to a main switch
Figure 5.13 Switches with dedicated, high-speed add-on ports
• Know Your Ethernets! – Know details of the Ethernet versions – Use summaries and tables – So far in the text, only the functions of a basic switch have been explained – More to see in terms of capabilities of switches