© Synergon Informatika Rt., 1999

Synergon Informatika Rt.

Chapter 13

WAN Connectivity Overview

2

Objectives

Upon completion of this chapter, you will be able to perform the following tasks:

List at least four common issue to be considered when evaluating a WAN service

Describe Cisco”s implementation of the following WAN connection type, including the key features of each type:

Dialin line via modem

Leased lines

Dial-up connections services

Packet-switched services

Identify encapsulation and compression methods for each WAN service type

3

WAN Connectivity

Options

4

Network Growth

TokenRing

TokenRing

TokenRing

• As networks expand, remote connection methods must be closely evaluated

5

Connection Considerations

• Availability

• Bandwidth

• Cost

• Easy of management

• Application traffic

• Routing protocol characteristics

6

Types of Connections

Async dialin using modems

Dedicated (leased) lines

Dial-up connections using a router

Packet-switched services

Async dialin using modems

Dedicated (leased) lines

Dial-up connections using a router

Packet-switched services

Access servers

Point-to-point over serial lines

Dial-on-demand routing and circuit-switched services

X.25, Frame Relay, SMDS/ATM

Access servers

Point-to-point over serial lines

Dial-on-demand routing and circuit-switched services

X.25, Frame Relay, SMDS/ATM

Services Description Cisco Offerings

7

Access Servers

Async Ports

Dialin Client

PSTN Network

File Server

E-Mail Server

Cisco 2511

• Asynchronous dial-up connections allow users access to shared data

8

Point-to-Point Serial Lines

DSU/CSU DSU/CSU

DSU/CSU DSU/CSU

• Dedicated links continuously available

9

Dial-on-Demand Routing

TokenRing

• Connections are made only when traffic dictates a need

PSTN or ISDN

A

B

C

10

Packet-Switched Service

Frame RelayX.25

SMDSATM

• Packet-switched networks are multiaccess, and data is carried within frames, packets, or cells

11

Frame Relay Networks

• Use a frame-based digital technology

• Have error checking but no error notification or retransmissions

• Are widely available in the United States and Europe

• Now support PVCs and SVCs (Cisco IOS Release 11.2)

• Support connection-oriented service

• Operate at speeds of 56/64 kbps up to 45 Mbps (T3)

• Have well-defined specifications

12

X.25 Networks

• Use a packet-based analog technology

• Have extensive error checking and retransmissions

• Are widely available in the Europe; some usage in the United States

• Now support PVCs and SVCs

• Support connection-oriented service

• Typically operate at speeds of 56/64 kbps up to T1/T3

• Have well-defined specifications

13

SMDS Networks

• Use a fast packet-based technology

• Have no end-to-end error checking or retransmissions

• Available in part of the United States and Europe

• Support connectionless service (SMDS)

• Operate at Ds-1 and DS-3 speeds

• Have well-defined specifications

14

ATM Networks

• Use a cell-switching technology

• Have no end-to-end error checking or retransmissions

• Available in the United States and growing rapidly in Europe

• Support both PVCs/SVCs and connectionless service

• Operate at speeds up to 155 Mbps

• Have still-evolving implementation standards

15

WAN Encapsulation and Compression

Options

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WAN Encapsulation Protocol

X.25/LAPB Frame Relay

ISDN/LAPD

Dial-up

Point-to-Point

Switched

PPP

PSTN

HDLC, PPP, LAPB

Packets Switched

Circuit Switched

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Encapsulation Command

Router (config-if) #

Encapsulation encapsulation-typeEncapsulation encapsulation-type

Defines the encapsulation (framing) type

Encapsulation are protocol-specific

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LAPB Encapsulation Commands

Router (config-if) #

Encapsulation lapb [ dte | dce | multi | protocol-name ]Encapsulation lapb [ dte | dce | multi | protocol-name ]

Selects LAPB as the encapsulation type

Uses the multi option allows multiple protocols to be carried within the LAPB frame

Using the protocol-name option allows a single protocol to be carried within the LAPB frame

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Configuring LAPB

Parameter Range Default

Lapb n1 bits 1088-32832 largest available lapb t1 milliseconds 1-64000 3200 lapb n2 retries 1-255 20 lapb k window-size 1-7 7 lapb modulo modulos 8 or 128 8

Lapb n1 bits 1088-32832 largest available lapb t1 milliseconds 1-64000 3200 lapb n2 retries 1-255 20 lapb k window-size 1-7 7 lapb modulo modulos 8 or 128 8

These parameters alter the retransmission characteristics of

LAPB

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Encapsulation Example

Interface serial 0

encapsulation ppp

ip address 144.200.18.1 255.255.255.0

ipx network 10

Interface serial 0

encapsulation ppp

ip address 144.200.18.1 255.255.255.0

ipx network 10

PSTN

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Serial Compression Techniques

Uncompressed (default )

Header compression

Payload compression

Link compression

header Payload

• More efficient use of bandwidth

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Compression CommandsRouter (config-if) #

Ip tcp header-compression [ passive ]Ip tcp header-compression [ passive ]

Specifies that headers for TCP traffic will be compressedRouter (config-if) #

Frame-relay payload-compressFrame-relay payload-compress

Enables payload compression on a specified poitn-to-point

interface or subinterface

Router (config-if) #

Compress [ predictor | stac ]Compress [ predictor | stac ]

Configure software compression for LAPB, PPP, and HDLC for a

link

23

Summary

WAN services are critical to global networks

Some available WAN services:

Dialin lines via PSTN

Leased lines

Dial-on-demand routing

Packet-switched or cell-switched networks

Some WAN encapsulation options:

Cisco HDLC, PPP, LAPB

Cisco compression options:

Header, payload, link