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 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.

100-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 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 StandardCablingCable DetailsConnectors Length 1000BaseCXCopperTwinaxTwinax25 m 1000BaseSXMultimode850 nmVariable – 220 – 500 m fiberSC is common 1000BaseLXSingle-1,300 nmVariable – 5 km mode fiberLC, SC are common 1000BaseTCAT 5e/6Four-pair /RJ m UTPfull-duplex Table 5.1

10-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

StandardFiber TypeWavelengthPhysical Layer Signaling Maximum Signal Length 10GBaseSRMultimode850 nmLAN m 10GBaseSWMultimode850 nmSONET/WAN 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)

StandardFiber TypeWavelengthPhysical Layer Signaling Maximum Signal Length 10GBaseLRSingle-mode1310 nmLAN10 km 10GBaseLWSingle-mode1310 nmSONET/WAN10 km 10GBaseLy uses a long-wavelength (1310 nm) signal over single-mode Fiber-based 10GBaseLy Summary

StandardFiber TypeWavelengthPhysical Layer Signaling Maximum Signal Length 10GBaseERSingle-mode1550nmLAN40 km 10GBaseEWSingle-mode1550 nmSONET/WAN40 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 / StandardCablingCable DetailsConnectors Length 10GBaseSRMultimode850 nmNot defined26 – 300 m /SWfiber 10GBaseLRSingle-1310 nmVariable – LC10 km /LWmode fiberis common 10GBaseERSingle-1550 nmVariable – LC,40 km mode fiberSC are common 10GBaseTCAT 6/6aFour-pair /RJ-4555 – 100 m UTPfull-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