Exploration Accessing WAN Chapter1 Enhan

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2006 Cisco Systems, Inc. All rights reserved. Cisco PublicITE I Chapter 6 1

Services in a Converged

WAN

Accessing the WAN

Chapter 1


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2006 Cisco Systems, Inc. All rights reserved. Cisco PublicITE 1 Chapter 6 2

Objectives

Describe how the Cisco Enterprise CompositeModel (ECNM) provides integrated servicesover an Enterprise network.

Describe the key WAN technology concepts. Identify the appropriate WAN technologies to

use when matching ECNM best practices withtypical enterprise requirements for WAN

communications.


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WAN

A WAN is a data communications network thatoperates beyond the geographic scope of a LAN.

A LAN is privately owned, but you must subscribe to aservice provider to use WAN services.

WANs use serial connections of various types for large

geographic areas.


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Why are WANs Necessary?

For branches to communicate to the central office.

To share information.

For people who are

travelling.

To communicate withbanks & stores.

To do research.

Obi-WAN


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Example of Small Business Growth

As a business grows, so does the needs for business

requirements for services. The Internet has become an essential part of doing business.


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Hierarchical Design Model Refresher

Lower layers aggregate into upper layers.

Core Layer is the network backbone.

Distribution layer is the wiring closets.

Access Layer is user access to network devices.


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Cisco Enterprise Architectures

Problems with the Hierarchical Design Model (growingnetworks increasingly difficult to manage) areaddressed in the Cisco Enterprise Model (standardizedmodules).

Modules areavailable tomatch yourorganizationsneed.



Enterprise Campus Architecture

The Campus Module is modular, fast converging &

easy to expand.Access layer contains workstations, IP phones, & Layer 2switches.

Distribution layer provides Layer 3 switches.

The Edge Module gives access to voice, video, & datafrom outside the Campus Module.

Modules of Enterprise Architecture Sample Enterprise Topology: WAN & Internet



WAN in the OSI Reference Model

WAN takes place in:

Layer 1: Electrical, Mechanical, Operational, & FunctionalConnections.

Layer 2: How data is encapsulated for WAN transmission.



WAN Layer 1 Terms

Customer Premises Equipment (CPE) Equipment thatis customer owned & located on premises.

Data Communications Equipment (DCE) Connectionto service provider. Data Terminal Equipment (DTE) Customer Network. See p. 22 for DCE/DTE connections.

Local Loop Connects CPE to CO Demarcation Point

Separates customer fromservice provide

equipment. Central Office (CO)

Service Provide facilitylinked to long-distance

fiber lines.



WAN Devices

1. Modem Analog to digital conversion.

2. CSU/DSU (for high-speed lines) CSU terminatesdigital signal/provides error control & DSU converts adigital line (T1/T3) to frames.

3. Access Server For dial-In user communications.

4. WAN Switch Used in carrier networks like FrameRelay/ATM.

5. Router Providesinterface ports tocreate networks.

6. Core Router Highspeed WAN router.

1 1

23

4

5

61

1

1



Data Link Layer Protocols

Defines how data is encapsulated for transmission to

remote sites & mechanisms for transferring resultingframes.

ATM is differentfrom the otherprotocols becauseit uses a fixed-sizecells instead ofvariable sizedpackets.



WAN Encapsulation

Circuit Switching is one that

establishes a dedicatedcircuit between sending &receiving device.

Like a telephone call.

Higher cost/decreased

latency.

Packet Switching splitstraffic into packets that arerouted over a shared network.

No circuit is necessary.

Lower cost/increased latency.

2 link determination approaches: 1) Connectionless Switchdetermines route (full addressing in each packet). 2) ConnectionOriented Systems predetermine route (packet only carriesidentifier).



Virtual Circuit (VC)

A virtual circuit is a logical circuit created within a

shared network between 2 devices. 2 Types: 1) Permanent Used to transfer data. 2) Switched On-demand connection to reduce costs.



WAN Link Connection Options

WAN connections can be either over a privateinfrastructure or over a public infrastructure.

Private:

Dedicated(Point-to-Point).

Switched can be Circuit-Switched(must establishconnection beforecommunication) &Packet-Switched (forusers with

fluctuatingdata flow).

Public: Internet.



DEDICATED: Leased Line

Point-to-Point lines are leased from a carrier (leased

lines). A CSU/DSU is necessary. This is how Stark State gets its WAN capacity.



CIRCUIT SWITCHED: Analog Dialup

10 years ago, dialup was the most popular access tothe Internet. Still used to connect to networkequipment.

Limited to less than 56 kbps.



CIRCUIT SWITCHED: ISDN (Digital)

Integrated Services Digital Network (ISDN) enables the

local loop of a PSTN to carry digital signals.Allows the use of digital subchannels over PSTN.

Uses bearer (B)channels for data

& signaling (D)delta channel.

2 types:

Basic Rate Interface (BRI)

with 2 B channels & 1 D forhome/small business.

Primary Rate Interface(PRI) with 23 B channels& 1 D for larger

installations



PACKET-SWITCHED: X.25

X.25 is a legacy network-layer protocol that providessubscribers with a network address.

Used for point-of-sale terminals. Operates at Layer 3.



PACKET-SWITCHED: Frame Relay

Similar to X.25 but is much simpler (operates at

Layer 2).

Chapter 3 is all about Frame Relay.



PACKET-SWITCHED: ATM

Asynchronous Transfer Mode (ATM) is built on cell-based architecture.

ATM cells are always a fixed length of 53 bytes.


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INTERNET BROADBAND: Cable Modem

Similar to DSL but has greater bandwidth.



INTERNET BROADBAND: Broadband Wireless

Uses the unlicensed radio spectrum to send andreceive data.

New developments:

Municipal Wi-Fi City runs free wireless Internet.

WiMAX Similar to Wi-Fi but faster & broader coverage.Satellite Used whereCable & DSL areunavailable.


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circuits (PVCs) or switched virtual circuits (SVCs).


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Virtual Private Network (VPN)

VPN is an encryptedconnection (tunnel)between privatenetworks over a

public networksuch as the Internet.

Benefits are costsavings (eliminate

dedicated lines),security (encryption), scalability (easy to addusers), & compatibility (with DSL, cable, etc).


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