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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. Overview. Three Parts to Chapter 5. 100-megabit Ethernet standards Gigabit Ethernet standards

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Modern ethernet

Modern Ethernet

Chapter 5



  • 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
Three Parts to Chapter 5

  • 100-megabit Ethernet standards

  • Gigabit Ethernet standards

  • 10-Gigabit Ethernet standards

Ethernet facts
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
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.

Modern ethernet

  • 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

Modern ethernet

  • 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

Modern ethernet

  • 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

Modern ethernet

  • 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

Modern ethernet

Figure 5.1 Typical 100BaseT NIC

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Figure 5.2 Auto-negotiation in action

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Figure 5.3 Typical 100BaseT NIC in Vista

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  • 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

Modern ethernet

  • 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

Modern ethernet

  • 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

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Figure 5.4 Half-duplex; sending at the top, receiving at the bottom

Modern ethernet

Figure 5.5 Full-duplex

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Figure 5.6 Forcing speed and duplex in Windows Vista

Modern ethernet

  • IEEE 802.3ab called 1000BaseT

    • Most dominant Gigabit Ethernet

    • Four-pair UTP

    • Maximum cable length 100 meters

    • Connectors and ports look exactly like 10BaseT, 100BaseT

Modern ethernet

  • IEEE 802.3z known as 1000BaseX

    • 1000BaseCX

      • Twinaxial cable

        • Shielded 150-Ohm

        • Maximum length of 25 meters

      • This standard made little progress

Modern ethernet

Figure 5.7 Twinaxial cable

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  • 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

Modern ethernet

  • 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

Modern ethernet

  • 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

Modern ethernet

  • 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

Modern ethernet

Figure 5.8 MT-RJ connector

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Figure 5.9 LC-type connector

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Table 5.1

Gigabit Ethernet Summary

Standard Cabling Cable Details Connectors Length

1000BaseCX Copper Twinax Twinax 25 m

1000BaseSX Multimode 850 nm Variable – 220 – 500 m

fiber SC is


1000BaseLX Single- 1,300 nm Variable – 5 km

mode fiber LC, SC are


1000BaseT CAT 5e/6 Four-pair / RJ-45 100 m

UTP full-duplex

Modern ethernet

  • 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

Modern ethernet

  • 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

Modern ethernet

  • 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

Modern ethernet

Modern ethernet

  • 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

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Fiber-based 10GBaseSy Summary

Modern ethernet

Figure 5.10 multimode A 10GBaseSR NIC (photo courtesy of Intel Corporation)

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Fiber-based 10GBaseLy Summary

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Fiber-based 10GBaseEy Summary

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  • 10 GbE connectors over single-mode fiber

    • Standards do not define the type of connector

    • Manufacturers determine connectors

Modern ethernet

  • Copper-based 10GbE over single-mode fiber(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

Modern ethernet

Table 5.2 over single-mode fiber

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


10GBaseT CAT 6/6a Four-pair / RJ-45 55 – 100 m

UTP full-duplex

Modern ethernet

  • 10-GbE Physical Connections over single-mode fiber

    • 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

Modern ethernet

Figure 5.11 over single-mode fiber XENPAK MSA

Modern ethernet

  • Backbones over single-mode fiber

    • 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

Modern ethernet

Figure 5.12 over single-mode fiber Typical network configuration showing backbone

Modern ethernet

Figure 5.13 over single-mode fiber Switches with dedicated, high-speed add-on ports

Modern ethernet

  • Know Your Ethernets! over single-mode fiber

    • 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