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High-Speed LAN and High-Speed LAN and Backbone NetworksBackbone Networks

After studying this Chapter you should: Know which internetworking devices are used in

backbone networks Describe several types of fast Ethernet and fast

Token Ring Describe FDDI Describe ATM and fiber channels Know ways to improve performance on BN

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DefinitionDefinition Backbone Network (BN) - a large high-speed

central network that connects all the terminals, microcomputers, mainframes, local area networks, and other communications equipment on a single company or site. Sometimes called a Campus Area Network (CAN). Use Higher speed circuits for connectivity.

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DefinitionDefinition Enterprise Network (EN) - a supernetwork that

interconnects all of an organizations networks (LANs and WANs), regardless of whether it crosses state, national, or international boundaries.

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Why interconnect networks?Why interconnect networks? Reliability Performance Security

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IntroductionIntroductionThere are two approaches to providing high speed

networking. “speed up” the technologies currently used in local area

networks. Fast Ethernet Fast Token Ring

develop new high speed technologies that provide dedicated point-to-point communication circuits

Switched Ethernet Switched Token Ring ATM

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Backbone Network ComponentsBackbone Network Components Two basic components to the BN

hardware devices that connect the networks to the backbone

hubs bridges switches routers brouters gateways

network cable

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HubsHubs very simple devices that pass all traffic in both

directions between the LAN sections they link same or different cable types use physical layer protocols pass on every message used to connect LANs of similar technology, or to

extend the distance of one LAN can be called repeaters or amplifiers

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HUB DevicesHUB Devices

HUB (MAU)

Repeater/Amplifier

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HubsHubs inexpensive easy to Install can connect different media very little delay

limited distance between devices limited on the number of repeaters no protocol or rate conversion no error detection does not filter

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BridgesBridges connect two LAN segments that use the same data

link and network protocol operated at the data link layer same or different cable types forward only those messages that need to go out

(filtering) “learn” whether to forward packets internal routing table combination of “black box” hardware and software

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BridgesBridges

There are three types of bridges: Simple bridge Learning bridge Multiport bridge

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Bridges InterconnectingBridges Interconnecting

HUB (MAU)

Repeater/Amplifier

HUB (MAU)

Repeater/Amplifier

Bridge

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BridgesBridges may be different data rates and different media easy

to Install no modifications required to the communications

software can learn the ports for data transmission

understand only data link layer protocols and addresses

no protocol conversion broadcasts when it does not know the address

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SwitchesSwitches connect more than two LAN segments that use

the same data link and network protocol. operate at the data link layer same or different type cable ports are usually provided for 4, 8, 16, or 32 LAN

segments ports are used simultaneously connect lower speed segments to high speed BN

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SwitchesSwitches Cut-through switches

use circuit-switching to immediately connect the port with the incoming message to the correct outgoing port

very fast as decisions are done in hardware outgoing packet is lost if port is in use

Store-and-forward switches copy the incoming packet to memory prior to

processing the destination address -- transmit it when the outgoing port is ready

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Switches InterconnectingSwitches Interconnecting

Wing C Wing C

Wing A Wing B

First Floor Switch

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SwitchesSwitches much more sophisticated than previously enable all ports to work at the same time can convert protocols configurable high speed

understand only data link layer protocols and addresses

much more expensive then previous options higher maintenance

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RoutersRouters connect two or more LANs that use the same or

different data link protocols, but the same network protocol.

same or different cable types operate at the network layer forward only messages that need to go out routers use the internetwork address internal routing tables only processes messages addressed to it

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RoutersRouters choose the best route to send the packet (path)

IDs of other networks paths to the networks relative efficiency of the paths

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RoutersRouters The router must deal with network differences:

addressing schemes minimum packet size interfaces reliability

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\

Routers InterconnectingRouters Interconnecting

Router

EthernetLAN2

Token RingLAN1

X.25 Networkthe “cloud”

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RoutersRouters can mix-in-match protocols and convert them enable all ports to work at the same time can be used as an extra layer of security configurable high speed

hard to configure and manage access lists must be kept current high maintenance/high training costs very expensive

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BroutersBrouters devices that combine the functions of both bridges

and routers operate at both the data link and network layers same or different data link protocol same network protocol as fast as bridges for same data link type networks

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GatewaysGateways complex machines that are interfaces between two or

more dissimilar networks connect two or more LANs that use the same or

different data link layer, network layer, and cable types operates at the network layer (3) or higher layers (4-7) forwards only those messages that need to go out a combination of both hardware and software

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GatewaysGateways translates one network protocol to another translates data formats translates open sessions between application

programs translates to mainframes

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GatewaysGateways Exists in four major types:

LAN-to-IBM mainframe Network-to-network System-to-network System-to-system

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LAN-to-IBM MainframeLAN-to-IBM Mainframe Allow LANs using TCP/IP and Ethernet to be

connected to IBM mainframe using SNA Eliminates the need for each PC on the LAN to

have SNA hardware/software that makes it act like an IBM 3270 terminal

GatewayMainframe

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\

Network-to-NetworkNetwork-to-Network

X.75 Gateway X.25 NetworkA

\X.25 NetworkB

X.75 provides terminaladdress translation

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System-to-NetworkSystem-to-Network

\X.25 NetworkGateway

Minicomputer orMicrocomputer

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System-to-SystemSystem-to-System allows connecting one vendor’s architecture to

another vendor’s architecture allows both the existence of OSI-based and

proprietary architectures (like SNA or AppleTalk) gives management to tools necessary to plan a

gradual migration to a completely OSI environment applications can work with other application

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System-to-SystemSystem-to-System

\X.25 Network

LAN E-mail Gateway

LAN E-mail Server

Profs E-mail

Profs E-mail Gateway

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Hub Physical All transferred S/D Same SameBridge Data link Filtered using S/D Same Same

data link layer add. Switch Data link Switched using S/D Same Same

data link layer add.Router Network Routed using S/D S/D Same

network layer add.Brouter Data link & Filtered & routed S/D S/D Same

NetworkGateway Network Routed using S/D S/D S/D

network layer add.

Physical Data Link NetworkDevice Operates at Messages Layer Layer Layer

Backbone Network DevicesBackbone Network Devices

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Terminology WarningsTerminology Warnings Multiprotocol bridges translate between different data

link layer protocols. Multiprotocol routers translate between different network

layer protocols. Protocol filtering bridges forward only packets of a

certain type, i.e., token-ring or ethernet Encapsulating bridges connect networks with different

data link protocols, encapsulating messages with correct protocol for transmission

Layer-3 switches (IP switches) - can also switch messages based on their network layer address

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Shared Media TechnologiesShared Media Technologies Fast Ethernet Fast Token Ring Fiber Distributed Data Interface

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Fast EthernetFast Ethernet 100Base-X Ethernet 100VG-AnyLAN Gigabit Ethernet Iso-ENET (isochronous ethernet)

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100Base-X Ethernet100Base-X Ethernet IEEE 802.13 identical to 10Base-T Ethernet three data link layer protocols 100 Mbps data rate standard ethernet bus topology ethernet data link packets ethernet CSMA/CD media access protocol

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100Base-X Ethernet100Base-X Ethernet

Three versions of 100Base-X Ethernet 100Base-TX 100Base-FX 100Base-T4

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100VG-AnyLAN100VG-AnyLAN

IEEE 802.12 both Ethernet or token-ring Demand Priority Access Method (DPAM)

polling polls each computer to see if it has data to send can use a priority system (notification system)

four sets of twisted pair running at 25 Mbps faster than 100Base-T

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Gigabit Ethernet Gigabit Ethernet IEEE 802.3Z 1000Base-X 1000 Mbps (1000 Mbps = 1 Gbps) high speed of transmission may cause

collisions to go undetected mainly used for point-to-point full-duplex

communication links (BN, MAN) PCs send or receive data at rates up to 100

Mbps

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Gigabit Ethernet Gigabit Ethernet Four versions of 1000Base-X Ethernet

1000 Base-LX (fiber up to 440 meters) 1000 Base-SX (fiber up to 260 meters) 1000 Base-T (four pairs twisted-pair up to 100

meters) 1000 Base-CX (one cat 5 cable up to 24 meters)

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Iso-ENETIso-ENET IEEE 802.9A isochronous Ethernet standard 10Base-T Ethernet + 6.144 Mbps both transmitted on the same twisted pair 6.144 circuit configured for ISDN for

transmission of voice and video mainly used for desktop videoconferencing

and multimedia products

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Fast Token RingFast Token Ring high-speed token ring (HSTR) standard token ring topology standard token ring protocols token passing media access control 100 Mbps instead of 16 Mbps category 5 or fiber optics cable IBM working on 1 Gbps version

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Fiber Distributed Data Fiber Distributed Data Interface (FDDI)Interface (FDDI)

ANSI X3T9.5 Topology - token-passing 2 counter-rotating rings Each ring operates at 100 Mbps over fiber optic

cable maximum of 1000 stations distance 120 mile path (200k) required repeaters to push transmission (2K) data is usually carried on the primary ring

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FDDI Station TypesFDDI Station Types

Dual-Attachment Station (DAS) connects to both primary and secondary rings requires 4 fibers to the desk allows the ring to continue to operate even if a

break occurs in the line by rerouting through the secondary ring (backwards)

Single-Attachment Station (SAS) connects only to the primary ring requires 2 fibers to the desk

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FDDI TopologyFDDI Topology

Primary Ring

Secondary Ring

FDDI Hub

SAS

SAS

SAS

DAS

Bridge

DAS

DAS

DAS

DAS

Workstations

Gateway

Mainframe

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FDDI - How does it work?FDDI - How does it work? Media accesss control

variation of token-passing standard FDDI allows multiple messages to attach to the token -

increases throughput above 100 Mbps An FDDI-to-IEEE 802.x bridge is required to

connect to lower speed corporate LANs At each node the optical signal is:

converted to an electrical signal amplified copied (if necessary) converted back to light to send to the next node

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Types of FDDITypes of FDDI Basic FDDI previously discussed FDDI-C (FDDI on Copper)

Copper Distributed Data Interface (CDDI) uses copper wire instead of fiber optic

FDDI-II permits transmission of voice and video over the same

cable as FDDI token-passing data uses time division multiplexing 17 channels

1 - 768 Kbps channel (token-passing) 16 - 6.144 Mbps channels (wide band - voice/video or data)

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Switched NetworksSwitched Networks Switched Ethernet Full-Duplex Ethernet Switched Token Ring Switched FDDI Asynchronous Transfer Mode (ATM) Fibre Channel

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Switched EthernetSwitched Ethernet the switch replaces the hub creates a point-to-point circuit to the switch allows multiple transmissions between computers store-and-forward improves LAN performance circuit to the server is the network bottleneck

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Other Ethernet SolutionsOther Ethernet Solutions Full-Duplex Ethernet

uses the same cables as regular Ethernet 10BaseT but full-duplex doubles the speed of connections to 20 Mbps full-duplex only from the switch to the server

may have several connections to one server

10/100 switched ethernet combines 10BaseT and 100BaseT to the server cheaper to install than 100Base-T maybe as fast as fast ethernet

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Switched Token RingSwitched Token Ring token ring switch replaces the token ring hub provides a series of point-to-point connections star topology no token to pass because of full duplex switch called “token-ring” because it uses token ring

packet format and is compatible with 802.5 hardware

dedicated token ring (DTR) full duplex 32 Mbps data rate due to full duplex (16 Mbps

each direction)

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Switched FDDISwitched FDDI FDDI witch replaces the FDDI hub point-to-point connctions to computers star topology no token because all computers can transmit

and receive at will same packet format and is fully compatible

with other FDDI hardwar

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ATMATM Isochronous networks provide very low and predictable node-

to-node delays. They are capable of dealing with steady, immediate delivery, and high-bandwidth requirements of multimedia technology.

Asynchronous Transfer Mode (ATM) is the ultimate isochronous technology by allocating bandwidth on demand via virtual circuits. high-speed, hardware-based, circuit-switching technology cell-relay LANE (LAN Emulation/LAN Encapsulation) connection-oriented ATM desktop - point-to-point full duplex - “low speed” version for the

desktop

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ATMATM

ATM is a switched network but differs from switched ethernet and switched token ring in four ways:1. ATM uses fixed-length packets of 53 bytes (ATM

encapsulation)

2. no error correction on the user data

3. ATM uses a very different type of addressing from traditional data link layer protocols such as ethernet or token ring

4. ATM prioritizes transmissions based on Quality of Service (QoS).

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Asynchronous Transfer Asynchronous Transfer Mode (ATM)Mode (ATM)

Asynchronous Transfer Mode is connection-oriented so all packets travel in order through the virtual circuit. A virtual circuit can either be a:

Permanent Virtual Circuit (PVC) - defined when the network is established or modified.

Switched Virtual Circuit (SVC) - defined temporarily for one transmission and deleted with the transmission is completed.

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LAN TranslationLAN Translation two approaches for translation

LANE (LAN Emulation/LAN Encapsulation) Multiprotocol over ATM (MPOA)

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LAN EncapsulationLAN Encapsulation usually referred to as LAN Emulation data link layer packets left intact; broken down

and encapsulated reassembled on the LAN side LAN thinks that the packets are token ring or

Ethernet requires ATM edge switches at each side

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Multiprotocol over ATMMultiprotocol over ATM extension of LANE uses network layer addresses and data link layer

addresses destination determines which address to use route servers required (MPOA servers)

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ATM to the Desktop ATM to the Desktop

ATM-25 is a low speed version of ATM which provides point-to-point full duplex circuits at 25.6 Mbps in each direction. It is an adaptation of token ring that runs over cat 3 cable and can even use token ring hardware if modified.

ATM-51 is another version designed for the desktop allowing 51.84 Mbps from computers to the switch.

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ATM Classes of Service ATM Classes of Service

ATM provides five classes of service: Constant Bit Rate (CBR) Variable Bit Rate-Real Time (VBR-RT) Variable Bit Rate-Non-Real Time (VBR-NRT) Available Bit Rate (ABR) Unspecified Bit Rate (UBR)

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Fiber ChannelFiber Channel

Fiber channel is relatively new networking technology, although it has been used inside computer and disk storage devices for several years.

Fiber channel was originally designed to provide high speed transmission over fiber optic cable. The maximum data rate is 1.062 Gbps up to 10 k with higher rates under development.

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Improving Backbone Improving Backbone PerformancePerformance

change network protocol check impact of applications replace the hubs with switches and make

point-to-point connections available increase circuit capacity make sure BN devices have sufficient

memory, so packets don’t get lost and have to be resent

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Improving Backbone Improving Backbone PerformancePerformance

use faster routing protocol upgrade computers that perform routing use switches from a single vendor eliminate need for switch-to-switch routing by

use of collapsed backbone switch

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Collapsed Backbone Collapsed Backbone NetworksNetworks

uses point-to-point circuits when possible uses a switch and a set of circuits to each LAN uses more cable, but fewer devices “backbone” exists in the switch improved performance switch replaces multiple bridges or routers lowers costs simplifies network management if the switch fails, the network is down

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Improving Circuit CapacityImproving Circuit Capacity increase overall circuit capacity or place

additional circuits alongside heavily used circuits

move from shared circuit to switched circuit BN

increase capacity to the server

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How much bandwidth to expect

LAN Type SpeedEthernet 10 MbpsToken Ring 16 MbpsFast Ethernet 100 MbpsFaster Ethernet 1 GbpsFast Token Ring 100 MbpsFDDI 100 MbpsATM 2.4 Gbps

Improving Circuit CapacityImproving Circuit Capacity

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Reduce Network DemandReduce Network Demand restrict high-bandwidth applications:

video conferencing medical imaging multimedia

set routing devices to filter broadcast messages

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Selecting a Backbone NetworkSelecting a Backbone Network

5 important factors to consider: Throughput Network cost Type of application Ease of network management Compatibility with current and future

technologies