CISCO NETWORKING ACADEMY Chabot College ELEC 99.08 Wide Area Network Introduction.

CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY

Chabot CollegeChabot College

ELEC 99.08ELEC 99.08Wide Area Network Introduction


WANsWANs


WAN TechnologiesWAN Technologies

Data Link Layer

Physical Layer

Network Layer

Session Layer

Transport Layer

Presentation Layer

Application Layer

WAN technologies


Physical and Data LinkPhysical and Data Link

Layer 2

Layer 1


WAN: Layer 1WAN: Layer 1

WAN physical layer protocols describe how to provide connections.


The WAN interfaceThe WAN interface

Your Ethernet LAN connects to your router. But what does you router connect to?

802.3 LAN ? WAN

Cat5 UTP


Regional Bells Provide MediaRegional Bells Provide Media

PACBELL

Regional Bells usually provide the media for Wide-Area Network connectivity.

SF NY


WAN PipesWAN Pipes

More….


The WAN interfaceThe WAN interface

How do routers connect to the phone companies lines?

to phone company


Data Terminal EquipmentData Terminal Equipment

Routers are usually considered DTEs. DTEs are devices at the end of a user’s network that serve as a data source, destination, or both.

The router is a DTE, or Data Terminal Equipment


Data Terminal EquipmentData Terminal Equipment

Your home computer can also be a DTE.

How do you connect to the phone company’s network at home?


to phone company

modem

DTEs and DCEsDTEs and DCEs

At home, you connect to the phone company’s network using a modem.


Data Circuit EquipmentData Circuit Equipment

A modem is a type of DCE, or Data Circuit-Termination Equipment. It’s the device at the end of the service provider’s network (phone company).


Data Circuit EquipmentData Circuit Equipment

• Another type of DCE is a CSU/DSU– Channel Service Unit– Data Service Unit

• CSU/DSU is located at the end of the service provider’s network (phone company).

• connects to router Serial port.


Customer’s Network

Phone Company’s

Network

DTEs and DCEsDTEs and DCEs

A DTE interfaces with a DCE to gain access to the phone company’s network.

DTE DCE

PCPCRouterRouter

ModemModemCSU/DSUCSU/DSU


DTEs and DCEsDTEs and DCEs• Router to CSU/DSU connection:

– Serial port on router– V.35 port on CSU/DSU – V.35 Cable between

CSU/DSU

DCEDTE


phone company

digital line

CSU/DSU

DTEs and DCEsDTEs and DCEsTypical WAN configuration:

CSU/DSU

DCE DCE

HaywardOakland

DTE DTE


DTEs and DCEsDTEs and DCEsOur Lab’s unusual configuration:

No digital phone lines, no CSU/DSUs.

The WAN is simulated in our lab.

Therefore, one router must play the DCE role - very unusual.

Serial interface Serial interface

V.35 CablesBack-to-Back

HaywardOakland

DTE DCE


WAN: Layer 2WAN: Layer 2

WAN data-link protocols describe how frames are carried between systems on a single data path.

– point-to-point

– multipoint

– multiaccess (Frame Relay)


WAN at Layer 2WAN at Layer 2

dedicated

switched


Data Link Layer: WAN ProtocolsData Link Layer: WAN Protocols


HDLCHDLC

High-level Data Link Control– usually used when connecting one router directly

to another (point-to-point)

– also is capable of supporting multipoint connections (multiple point-to-point) (test question)

– requires dedicated private digital lines

– HDLC implementations are proprietary

– Cisco serial interfaces default to HDLC


PPPPPP

Point-to-Point Protocol– used in point-to-point dedicated connections

– used by

• routers over dedicated digital lines

• POTS users over dial-up (circuit switched) lines (Windows & Mac dial-up networking)

– descendant of SLIP

– open standard (RFC 1661)

– allows authentication (PAP, CHAP)

– allows multiple layer 3 protocols


Frame RelayFrame Relay

Frame Relay– packet switched

– private dedicated digital lines not required

– one physical link can handle multiple logical links - (multiaccess)

– descendant of X.25

– simplified frame (no error correction) relies on today’s superior data links

– very fast

– cheap: pay for what you use


ISDNISDN

Integrated Services Digital Network– circuit switched - (over digital voice/data line)

– designed to transmit voice, data, video over existing phone lines

– used primarily for remote access via modems

– not very fast (especially BRI - 128 Kbps)

– may disappear with the emergence of cable modems and DSL


WAN Technology Options WAN Technology Options

CISCO NETWORKING ACADEMY Chabot College ELEC 99.08 Wide Area Network Introduction.

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