DCN286Introduction to Data Communication

Technology

Session 6

Review

1) Which of the following describes attenuation?a) A loss of signal strength b) An increase in signal strengthc) The delay experienced during d) The time it takes a signal to reach

signal travel its destination

2) Which of the following are tests specified by TIA/EIA-568-B standard for copper cable? (Select 3 answers)?

a) Signal harmonics b) Conductive responsec) Wire map d) Signal absorptione) Insertion loss f) Propagation delay

3) What are three distinct kinds of crosstalk (Select three answers)?a) NEXT b) FEXTc) ANEXT d) SPNEXTe) PSNEXT

4) Which cable type is cheapest to install?a) Coaxial b) Fibre-opticc) STP d) UTP

5) What can be discovered by using an Ethernet cable-testing device to do wire maps?a) Faulty serial circuits b) The location of a cabling runc) Information about the distance d) Incorrect pinouts

to a cabling fault

Objectives

Design ConsiderationsRepeaters, Hubs, Bridges and SwitchesModels for PC CommunicationsCabling WANsDTE and DCE cablesConsole

Ethernet LAN Physical Layer

4

Design Considerations

Data LinkLayer

PhysicalLayer

ISO Layers

Eth

erne

tIEEE 802.2 (Logical Link Control - LLC)

IEEE 802.3 (Media Access Control – MAC)

10B

AS

E2

10B

AS

E5

10B

AS

E-T

10B

AS

E-F

100B

AS

E-T

X

100B

AS

E-F

X

100B

AS

E-T

4

1000

BA

SE

-T

1000

BA

SE

-X

Picking a cableMaximum cable length (per standard) vs. length of run required

Cost of the cable

Cost of equipment at each end of cable

Which cables support different Ethernet speeds

Ease of installation

Susceptibility to interference

5

Design Considerations

Choosing Ethernet Types (Speeds)When choosing the Ethernet speed, what attribute of a communications link are we selecting?

When this is determined – is it a once-size-fits-all installation?

Consider the following three ways you can categorize the installation:End-user level – link from Hub/Switch to PC's NIC

Workgroup level – links from Hubs/Switches that connect End-user level to other Hubs/Switches in the LAN core

Backbone level - links from Hubs/Switches to other Hubs/Switches in the LAN core (no end-user devices)

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Design Considerations

Choosing Ethernet Types (Speeds)

7

Design Considerations

10/100Mbps

100Mbps-1Gbps

1Gbps-10Gbps

End-userLevel

WorkgroupLevel

BackboneLevel

Bandw

idth Requirem

ent

Choosing Ethernet Types (Speeds)

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Design Considerations

Access Links

Uplinks

Core Links

AccessSwitches

Distribution Switches

Core Switches

Building Block

to other building blocks

to otherbuilding blocks

Picking UTP Cable PinoutsStraight-through cable

Connects what to what?

Wire both ends TIA/EIA-T568-AORWire both ends TIA/EIA-T568-B

9

Design Considerations

Picking UTP Cable PinoutsCrossover cable

Connects what to what?

10BASE-T and 100BASE-TXWire one side TIA/EIA-T568-A and the other endTIA/EIA-568-B

1000BASE-TWire one end TIA/EIA-T568-B, on the other end swap the orange/green pair (pairs 1 and 2) with the blue/brown pair (pairs 3 and 4)

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Design Considerations

Picking UTP Cable PinoutsTransmit Pair DevicesPins 1 & 2 PCs (NIC cards), routers,

servers, wireless access points

Pins 3 & 6 Switches, hubsbridges, repeaters

Straight-though cable when connecting a device that transmits on Pins 1 & 2 to a device that transmits on Pins 3 & 6.

Crossover cable when connecting a device that transmits on Pins 1 & 2 to another device that transmits on Pins 1 & 2. Or connecting a device that transmits on Pins 3 & 6 to another device that transmits on Pins 3 & 6.

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Design Considerations

Picking UTP Cable PinoutsSome devices have built-in crossover capabilities. Look for an 'X' on the port's label

1 X 1

2 2X

3X X 3X

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Design Considerations

Connecting Ethernet Networking Devices

RepeaterPurpose?5-4-3 Rule: maximum 5 cables, maximum 4 repeaters, and maximum 3 cables can have end-user devices

HubPurpose?

Passive – no power required to run, does not repeat signal

Active – power required, repeats signal

Intelligent – Active Hub with some management capability

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Design Considerations

Connecting Ethernet Networking Devices

BridgePurpose?How does it work?

SwitchPurpose?

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Design Considerations

ClientA network device that requires use of a resource

ServerA network device that provides the resource or service used by a client

Peer-to-PeerA net model where computers act as equals (peers) providing their service to each other. A PC may act as a client in one moment and as a server in another

Client/ServerA network model where a PC is designated as being a client or being a server

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Models for PC Communications

Peer-to-PeerAdvantages:Capability is built into modern operating systemsEasy to set upDoes not require administrator to manageNo special hardware or software required

Disadvantages:No centralized security controls (user responsible for protecting their own PC)Backups must be performed by each individualPC's performance drops while acting as a serverEach user needs to be trained properly manage their own PC

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Models for PC Communications

Client/ServerServers are more powerful machines that the typical user's.

The O/S is a Network Operating System (NOS) that is designed specifically for the purpose.

Must be available 24/7 – which implies multiple servers to allow for failure or backups.

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Models for PC Communications

Client/ServerAdvantages:Centralized security – controlled through user ID and passwordEasy to backup data – especially data that has regulatory requirementsMore scalable than peer-to-peer

Disadvantages:Hardware / software costs are greaterPersonnel costs are higher as you require dedicated Network AdministratorsServers can be a single point of failure (through poor design or cost restrictions)

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Models for PC Communications

RouterRouter may have dedicated ports for various connection methods (DSL, ISDN, ...), however more typically they have a single serial interface.

It is up to the network engineer to decide on the serial connection. The N.E. selects the serial device (requires a Channel Service Unit (CSU) and Data Service Unit (DSU)) and orders the appropriate cables.

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Cabling WANs

Telco

RouterSample WAN link:

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Cabling WANs

Cable with RJ-45Connector

CSU / DSU

Serial Interface

Serial cable (short)

Router

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Cabling WANs

http://www.jlsnet.co.uk

RouterTelco provides:CSU/DSUData communications cable with RJ-45 jacks

Router supplier provides:Router with specific serial interface (EIA-232, EIA-449, V.35, X.21, EIA-530...Appropriate cable (maybe)(built-in CSU/DSU available)

Network Engineer providesAppropriate cable for serial interface to CSU/DSUSelection of serial protocol: Point-to-Point Protocol (PPP), High-Level Data Link Control (HDLC), Frame Relay

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Cabling WANs

WAN LinksCable:Uses CATV coaxial cable

DSL:Uses phone line

ISDN (Integrated Services Digital Network)Connection dialed like a phone numberUsed as a fail-over link if leased line goes downBRI (Basic Rate Interface) runs over phone line – 2 x 64Kbps B channels and a 16Kbps D channelPRI (Primary Rate Interface) – 23 x 64Kbps B + 1 x 64Kbps D channels = 1.5Mbps

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Cabling WANs

WAN SpeedsRun at a variety of speeds, eg 2400bps (2.4Kbps)

Typically run in multiples of 64Kbps up to 1.536Mbps

T1 line runs at 1.536Mbps. Multiples of T1 are available, for example T3 runs 28 times faster, giving about 43Mbps

SONET uses fibre-optic cables with a minimum speed of 51.84Mbps. Multiples of 51.84Mbps are available up to 10Gpbs.

Telco charges for the service – the faster the service the more you pay.

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Cabling WANs

WAN Speeds vs Cable LengthsData (bps) Distance (m) Distance (m)

EIA-232 EIA-449, V.35, X.21, EIA-530

2400 601250

4800 30625

9600 15312

19200 15156

38400 15 78115200 3.7 -T1 (1.5Mbps) - 15

This is the distance between your router and the CSU/DSU – typically these distances are not an issue as the router and CSU/DSU are in the same room or cabinet.

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Cabling WANs

Data Communications Equipment (DCE)A device that supplies clocking to another device

Modems, Hubs, Bridges, Switches

Data Terminal Equipment (DTE)A device that receives clocking from another device and adjusts its clock as needed

NIC (PC), Routers, AP (WLAN Access Point)

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DCE / DTE Cables

Connecting Routers “back-to-back”Used in lab situations

Connecting a DTE cable to a DCE cablePerforms crossover of transmit and receive lines, and allows router acting as DCE to provide clocking signals.

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DCE / DTE Cables

DTE cable DCE cable

Tx

Tx

Tx Tx Rx

RxRxRx

Connecting Asynchronous DTE Devices “back-to-back”Used in lab situations

- transmit and receive lines are crossed- other signal lines (CTS, RTS, DSR) are connected together to fool the DTE into believing it is connected to a modem that has an active session to a remote DCE/DTE.

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NULL Modem Cable