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Network ComponentsNetwork 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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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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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