01 - Introduction to WAN

CCNA ExplorationCampus-Booster ID : 327

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Introduction to WAN

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Course objectives

Learn about WAN devices

Understand WAN norms

Create a hierarchical network

Learn about WAN networks

By completing this course, you will :

Introduction to WAN

Course topics

WAN Technology concepts

WAN Connection options

Course plan

Introduction to WAN


Introduction to WAN

Plan

Overview

Equipments and devices

Physical Layer Terminology

Norms

Physical Layer concepts

Data Link concepts

Chapters we will study:


OverviewWAN Technology concepts

Working primarily on Layers 1 & 2 of the OSI Model

Correlation between OSI Model and WAN Services

OSI Model WAN Services

Data Link Frame Relay, ATM, HDLC

Physical Link Electrical, mechanical, operational connections


Main characteristics of WAN networks:

Wide geographical areas

Internet providers services

Layers 1 & 2 of the OSI Model


Local loop = part between the customer’s POP and the service provider CO

Group of links linked to interconnected telecom providers


Router

Layer 3 equipment

Provides several services such as :

Path selection

LAN and/or WAN ports

Filtering

NAT Redirection



Communication server

Layer 7 equipment

Inbound and outbound concentrator for users communications

Example : DSLAM


WAN Switches

Layer 2 unit

Multi-port device that ensure WAN traffic switching

Examples : ATM switch, ISDN




Modem & CSU/DSU unit

Layer 1 unit

Converts a signal into another one

Exemples

Modem : Digital to analog converter using modulation and demodulation process

CSU/DSU unit : Digital Interface (TA, NT1, etc.)




12

3

4

5

6

LAN1

CPE2

Demarcation line3

Local loop4

Central Office switch5

Service provider interurban network6



CPE

Located at the customer premise

Belong to the customer or rented by the provider

Example : Modem, NT1

DCE:

Convert user’s data in a WAN format



DTE

Provides the user’s data

Demarcation Line :

Demarcation between customer side and provider side

Line that separate responsibilities



Local loop

Link between the demarcation line and the central office

Switch :

Nearest to the customer

Inter-Urban network :

Service provider “cloud” (Routers, switches, etc).


WAN norms

Describes :

Delivery ways of Physical layer

Configuration of Data-link layer

Addressing

Flow control

Encapsulation


WAN norms

Normalization organisations :

ITU (International Telecommunications Union

ISO (International Standards Organization)

IETF (Internet Engineering Task Force)

EIA (Electrical Industries Association)

TIA (Telecommunications Industry Association)

WAN Physical Layer conceptsWAN Technology concepts

Physical layer

Description of the interface between DCE and DTE

DTE DCE

Physical layer norms


EIA/TIA-232 (similar to the V.24)

Asymmetrical circuits

Up to 64 Kbits/s

EIA/TIA-449

Faster version of EIA/TIA-232 (2 Mbits/s)

EIA/TIA-612/613

Describes HSSI interface (Pour E3, T3, SDH STM-0, etc.)


V.35

Synchronous circuits

For packet networks

X.21

Synchronous digital lines

G.703

BNC connector

E1 throughputs (2.048 Mbits/s)


V. EAI-530: Two electrical implementation of EIA/TIA-449

RS-422: Symmetrical transmission

RS-423: Asymmetrical transmission

WAN Data Link conceptsWAN Technology concepts

Data link layer

Definition of data encapsulation

WAN Encapulations (Layer 2)


Frame Relay :

Lightweight simplified Encapsulation

No error correction

To be used with very-top digital equipment

Fast data transmission

2 variants :

Cisco

IETF


PPP :

Contain a layer 3 protocol identification field

Link quality verification at the connection establishment

Possible authentication:

PAP

CHAP

ISDN :

Group of digital services for voice and data


LAPB :

For X.25 networks

On packets switching network

Also on point-to-point link if bad reliability and/or important delay (Example: satellite link)

Reliability and flow control


HDLC :

Can be incompatible between providers (several implementation of HDLC)

Support point-to-point and multipoint connection type

Based on and replacement to SDLC

Enable by default on WAN interfaces of Cisco router

Very simplified ( no windowing and no flow control)

HDLC is recommended for link between 2 IOS equipment (if not PPP is advised)


Telecom providers supply end-to-end communications

Offer services such as:

Communication initiation (Signalization)

Data transit

Time-division multiplexing

Bandwith sharing


WAN paths that interconnect DTE

Link

Circuit

Canal

Line


DTE provides datas (router)

DCE converts and transports datas (Modem, CSU/DSU unit, TA, NT1)

DCE is the interface between DTE and service provider WAN link


2 kinds of circuits

End-to-End : Dedicated circuits (POTS, ISDN)

Virtual : Logical circuit through a cloud (Frame Relay, X.25)

SVC

PVC


SVC

Dynamically established on demand an closed at the end of the transmission

3 steps communication :

Establishment

Data transfert

Closing

Bandwidth consumption (because of steps)

Low costs (according to time)


PVC

Permanently established

Used for constant transmission needs

Communication in 1 step

Transfert

Lower bandwidth consumption (less steps)

Higher costs (permanent services)


Line Bandwith

T1

E1

E3

T3

1.544 Mbits/s

2.048 Mbits/s

34.064 Mbits/s

44.736 Mbits/s

Examples :

PauseWAN Technology concepts

At which layers of the OSI Model do WAN networks work?

Layers 1 & 2


What is the difference between a modem and a CSU/DSU unit?

The first one is analog, the second one digital


What kind of encapsulation is generally used on ADSL lines ?

PPP

WAN Connection Options

Introduction to WAN

Plan

Introduction

Dedicated connection link options

Switched connection options

Chapters we will study:

WAN Connection Options

WAN network

Dedicated Switched

Circuits switching

Packets/cells switching

T1/E1T3/E3

POTSISDN

56K,V90

X.25Frame Relay

ATMSMDS

IntroductionWAN Connection Options

Dedicated connection link optionsWAN Connection Options

Continuous service

Physical dedicated link between customer and provider

Point-to-point synchronous serial links

Physical link

Virtual link made of several physical links

Used for big quantities of informations and constant traffics

Dedicated connection link optionsWAN Connection Options

Switched Connection OptionsWAN Connection Options

Circuit switching :

Physical commutation of telephony central in order to get a point-to-point link

Packets /cells Switching:

“Logical” switching performed at the layer 2 of the OSI model


Circuit switching :

Physical dedicated circuit using switching at central offices

Established, maintained and closed at each session

Established on demand

Can be used as backup link for main link

Dedicated bandwidth



Circuit switching disadvantages :

Low data rate

Relatively long connection time

Example of ISDN:

2 types: BRI and PRI


Usage of a virtual point-to-point dedicated circuit (PVC or SVC)

Forwarding variable (packets) or fixed (cells) length frames

Flexible usage

Better use of the bandwith than circuits switching links


WAN network

Switch

LAN

LA

N

LA

N

Provider network

DCE

DCE DCE


Packet switching can be viewed as a mix between leased lines and circuit switching (low cost)

Frame Relay, ATM, and legacy X.25 are the most popular packet-switching technologies used today

PauseWAN Connection Options

ATM

POST

RNIS

Frame Relay

Circuits switching

Packet switching

Link peers up

QuizzWAN networks

At customer side

At provider side

Where is DCE located ?

WAN connection

Option

WAN connection

Option

Course summary

WAN technologies

concept

WAN technologies

concept

Introduction to WAN

Congratulations

You have successfully completed the SUPINFO course

Introduction to WAN

The EndIntroduction to WAN

01 - Introduction to WAN

Documents

wan devices

wan traffic

devices wan switches

wan networks introduction

wan course objectivesby

wan interfaces of cisco

devices router layer

hdlc physical link electrical