Module 1 Introduction to WANs

Module 1

Introduction to WANs

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Objectives

• Describe how the Cisco enterprise architecture provides

integrated services over an enterprise network.

• Describe key WAN technology concepts.

• Select the appropriate WAN technology to meet different

enterprise business requirements.

Providing Integrated Services

to the Enterprise

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Introducing Wire Area Network

The three major characteristics of WANs:

• WANs generally connect devices that are separated by a broader

geographical area than can be served by a LAN.

• WANs use the services of carriers, such as telephone companies, cable

companies, satellite systems, and network providers.

• WANs use serial connections of various types to provide access to bandwidth

over large geographic areas.

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The Evolving Enterprise

A Growing Business and Its Network

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The Hierarchical Network Model

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The Hierarchical Network Model

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The Enterprise Architecture

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The Enterprise Architecture Example

WAN Technology Concepts

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WAN Technology Overview

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WAN Physical Layer Concepts

WAN Physical Layer Terminology

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WAN Devices

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WAN Physical Layer

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WAN Data Link Layer Concepts

WAN Datalink Protocol

Router(config)#interface serial slot/port number

Router(config-if)#encapsulation ppp| hdlc| frame-relay

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WAN Data Link Layer ConceptHDLC Frame

01111110 01111110

Information

or ControlLayer3

Protocol

(IP, IPX…)

Layer2

Address

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WAN Switching Concept

• A circuit-switched network is one that establishes a dedicated circuit (or

channel) between nodes and terminals before the users may communicate

• The internal path taken by the circuit between exchanges is shared by a

number of conversations. Time division multiplexing (TDM) gives each

conversation a share of the connection in turn. TDM assures that a fixed

capacity connection is made available to the subscriber.

Circuit-switched network

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WAN Switching Concept

An alternative is to allocate the capacity to the traffic only when it is needed, and share the available capacity between many users.

Packet-switching networks do not require a circuit to be established, and they allow many pairs of nodes to communicate over the same channel.

Because of shared the circuit, there must be some mechanism to label the bits so that the system knows where to deliver them.

It is difficult to label individual bits, therefore they are gathered into groups called cells, frames, or packets.

Packet-switched network

WAN Link Connection Options

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WAN Link Connection Options

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Dedicated Connection Link Options

Leased Line

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Circuit Switched Connection Options

Analog Dialup

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Circuit Switched Connection Options

ISDN

Integrated Service Digital Network

The connection uses 64 kbps bearer channels (B) for carrying voice or data and a signaling, delta channel (D) for call set-up and other purposes.

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Packet Switching Connection Options

• The first of these packet-switched networks was standardized as the X.25

group of protocols.

• X.25 link speeds vary from 2400 b/s up to 2 Mb/s. However, public networks

are usually low capacity with speeds rarely exceeding above 64 kb/s.

• X.25 networks are now in dramatic decline being replaced by newer layer 2

technologies such as Frame Relay, ATM, and ADSL.

X.25

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Frame-Relay

• Frame Relay offers data rates up to 4 Mb/s, with some providers offering even higher

rates

• Frame Relay virtual-circuits (VC) are uniquely identified by a DLCI, which ensures

bidirectional communication from one DTE device to another

• Most Frame Relay connections are PVCs rather than SVCs.

• Frame Relay provides permanent shared medium bandwidth connectivity that carries

both voice and data traffic.


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ATM

• Asynchronous Transfer Mode (ATM) technology is capable of transferring voice,

video, and data through private and public networks

• It is built on a cell-based architecture

• ATM cells are always a fixed length of 53 bytes

• ATM was designed to be extremely scalable and can support link speeds of

T1/E1 to OC-12 (622 Mb/s) and higher.

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Broadband Service

• DSL technology is an always-on connection technology that uses existing twisted-pair

telephone lines to transport high-bandwidth data, provides IP services to subscribers.

• A DSL modem converts an Ethernet signal from the user device to a DSL signal

DSL – Digital Subscriber Line

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• Coaxial cable is widely used in urban areas to distribute television signals.

• This allows for greater bandwidth than the conventional telephone local loop.

• Enhanced cable modems enable two-way, high-speed data transmissions

using the same coaxial lines that transmit cable television.

• Cable modems provide an always-on connection and a simple installation.

Cable Modem

Broadband Service

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• WiMAX

‒ Described in the IEEE standard 802.16

‒ WiMAX operates in a similar way to WiFi, but at higher speeds, over greater

distances (10 miles), and for a greater number of users.

‒ It uses a network of WiMAX towers that are similar to cell phone towers

• Satellite Internet

‒ The upload speed is about one-tenth of the 500 kb/s download speed

‒ To access satellite Internet services, subscribers need a satellite dish, two modems

(up and down), and coaxial cables between the dish and the modem

Broadband Wireless

Broadband Service

VPN

• Virtual Private Network (VPN) is defined as network connectivity deployed on a

shared infrastructure with the same policies and security as a private network.

• A VPN can be between two end systems, or it can be between two or more

networks.

• A VPN can be built using tunnels and encryption. VPNs can occur at any layer of

the OSI protocol stack.

• A VPN is an alternative WAN infrastructure that replaces or augments existing

private networks that use leased-line or enterprise-owned Frame Relay or ATM

networks.

• There are two types of VPN access:

– Site-to-site VPNs

– Remote-access VPNs33

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Internet Connection Options

Site-to-site VPNs

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Remote-access VPNs

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• Extending Ethernet to the metropolitan area

• Metro Ethernet is a rapidly maturing networking technology that broadens

Ethernet to the public networks run by telecommunications companies.

• IP-aware Ethernet switches enable service providers to offer enterprises

converged voice, data, and video services such as IP telephony, video

streaming, imaging, and data storage

Metro Ethernet

Good luck with this module!

Module 1 Introduction to WANs

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