Modern Ethernet

Chapter 5

ObjectivesObjectives• Describe the varieties of 100-megabit

Ethernet• Discuss copper- and fiber-based Gigabit

Ethernet• Compare the competing varieties of 10-

Gigabit Ethernet

OverviewOverview

Three Parts to Chapter 5Three Parts to Chapter 5

• 100-megabit Ethernet standards• Gigabit Ethernet standards• 10-Gigabit Ethernet standards

Ethernet FactsEthernet 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.

100-Megabit Ethernet100-Megabit 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

• 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

Figure 5.1 Typical 100BaseT NIC

Figure 5.2 Auto-negotiation in action

• Distinguishing 10BaseT NIC from 100BaseT NIC– Inspect closely– Look for something indicating the card’s speed– All modern NICs are multispeed and auto-sensing

Figure 5.3 Typical 100BaseT NIC in Vista

• 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

Figure 5.5 Full-duplex

Figure 5.6 Forcing speed and duplex in Windows Vista

Gigabit EthernetGigabit 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

• IEEE 802.3z known as 1000BaseX– 1000BaseCX

• Twinaxial cable– Shielded 150-Ohm– Maximum length of 25 meters

• This standard made little progress

Figure 5.7 Twinaxial cable

• 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

Figure 5.8 MT-RJ connector

Figure 5.9 LC-type connector

Gigabit Ethernet Summary

Standard Cabling Cable Details Connectors Length

1000BaseCX Copper Twinax Twinax 25 m

1000BaseSX Multimode 850 nm Variable – 220 – 500 mfiber SC is

common

1000BaseLX Single- 1,300 nm Variable – 5 kmmode fiber LC, SC are

common

1000BaseT CAT 5e/6 Four-pair / RJ-45 100 mUTP full-duplex

Table 5.1

10-Gigabit Ethernet10-Gigabit 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

• 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

Standard Fiber Type Wavelength Physical Layer Signaling

Maximum Signal Length

10GBaseSR Multimode 850 nm LAN 26-300 m

10GBaseSW Multimode 850 nm SONET/WAN 26-300 m

• 10GBaseSy uses a short-wavelength (850 nm) signal over multimode

Fiber-based 10GBaseSy Summary

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

Standard Fiber Type Wavelength Physical Layer Signaling

Maximum Signal Length

10GBaseLR Single-mode 1310 nm LAN 10 km

10GBaseLW Single-mode 1310 nm SONET/WAN 10 km

• 10GBaseLy uses a long-wavelength (1310 nm) signal over single-mode

Fiber-based 10GBaseLy Summary

Standard Fiber Type Wavelength Physical Layer Signaling

Maximum Signal Length

10GBaseER Single-mode 1550nm LAN 40 km

10GBaseEW Single-mode 1550 nm SONET/WAN 40 km

• 10GBaseEy uses an extra-long-wave-length (1550 nm) signal over single-mode fiber

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

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 kmmode fiber SC are

common

10GBaseT CAT 6/6a Four-pair / RJ-45 55 – 100 mUTP full-duplex

Table 5.2

• 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

Figure 5.11 XENPAK MSA

• 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 5.12 Typical network configuration showing backbone

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