CS计算机代考程序代写 flex Instructor Materials Chapter X: Chapter Title

Instructor Materials Chapter X: Chapter Title

CE321

Network Engineering

Introduction

CE321 – Introduction ‹#›
1

Chapter 1: WAN Concepts
Connecting Networks

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
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Cisco Networking Academy Program
Connecting Networks
Chapter 1: WAN Concepts

Chapter 1 – Sections & Objectives
1.1 WAN Technologies Overview
Explain WAN access technologies available to small to medium-sized business networks.
1.2 Selecting a WAN Technology
Select WAN access technologies to satisfy business requirements.

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
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1.1 WAN Technologies Overview

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
4
Cisco Networking Academy Program
Connecting Networks
Chapter 1: WAN Concepts

WAN Technologies Overview
Purpose of WANs
WANs connect LANs
WANs are used to connect remote sites to the enterprise network.
WANs connect home users to the Internet.
Enterprise networks are using security and privacy solutions over the Internet to connect remote sites and users.

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
5
1.1 – WAN Technologies Overview
1.1.1 – Purpose of WANs

WAN Technologies Overview
Purpose of WANs
Common WAN topologies are:
Point-to-Point – Typically a dedicated leased-line connection such as T1/E1
Hub-and-Spoke – A single-homed, point-to-multipoint topology where a single interface on the hub router can be shared with multiple spoke routers through the use of virtual interfaces
Full Mesh – Each router has a connection to every other router; requires a large number of virtual interfaces
Dual-homed – Provides redundancy for a single-homed, hub-and-spoke topology by providing a second hub to connect to spoke routers

Point-to-Point
Hub-and-Spoke
Full Mesh
Dual-Homed

Presentation_ID
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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
6
1.1 – WAN Technologies Overview
1.1.1 – Purpose of WANs

WAN Technologies Overview
Purpose of WANs
As businesses grow, the topologies and WAN strategies change:
Small Office – These businesses typically consist of one LAN at one location that connects to the Internet through a broadband technology.
Campus Network – A small- to medium-sized business with one location and multiple LANs uses specialized equipment and technologies to connect to the Internet.
Branch Networks – As the business grows, it adds more branch offices, each with its own campus network. WAN contracts to connect the remote networks are negotiated.
Distributed Network – A multinational business has a network distributed across the globe. These businesses have complex WAN strategies to securely connect to regional offices, branch offices, partners, and telecommuters.

Small Office
Campus Network
Distributed Network

Presentation_ID
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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
7
1.1 – WAN Technologies Overview
1.1.1 – Purpose of WANs

WAN Technologies Overview
WAN Operations
WAN operations focus primarily on the physical layer (OSI Layer 1) and the data link layer (OSI Layer 2).
Layer 1 protocols describe how to provide electrical, mechanical, operational, and functional connections
Layer 2 protocols define how data is encapsulated
WAN Terms include:
Customer Premises Equipment (CPE) – owned by the business or leased from the service provider.
Data Communications Equipment (DCE) – provides an interface to connect subscribers to a communication link on the WAN cloud.
Data Terminal Equipment (DTE) – connects to the local loop through the DCE.
Demarcation Point – separates customer equipment from service provider equipment and is the place where the responsibility for the connection changes from the user to the service provider.
Local Loop – cable that connects the CPE to the CO of the service provider (last mile).
Central Office (CO) – local service provider facility or building that connects the CPE to the provider network.
Toll network – all the cabling and equipment inside the WAN provider network.

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
8
1.1 – WAN Technologies Overview
1.1.2 – WAN Operations

WAN Technologies Overview
WAN Operations
WAN devices include:
Dialup modem – legacy WAN technology that converts digital signals into voice frequencies to be transmitted over the analog lines of the public telephone network.
Access server – legacy WAN technology that coordinates dial-in and dial-out user communications.
Broadband modem – used with high-speed DSL or cable Internet service
CSU/DSU – used to convert digital, leased-line signals into frames that the LAN can interpret and vice versa.
WAN switch – multiport internetworking device used in service provider networks
Router – provides internetworking and WAN access interface ports to connect to the service provider network
Core router/Multilayer switch – resides within the backbone of the WAN, supports multiple interfaces, and forwards IP packets at full line speed

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
9
1.1 – WAN Technologies Overview
1.1.2 – WAN Operations

WAN Technologies Overview
WAN Operations
WANs can operate as circuit-switched or packet-switched networks:
Circuit-switched Networks – establish a dedicated circuit between source and destination before the users may communicate, such as making a telephone call
Packet-Switched Networks – split traffic into packets that are routed over a shared network and do not require a dedicated circuit between source and destination

Circuit-Switched
Packet-Switched

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
10
1.1 – WAN Technologies Overview
1.1.2 – WAN Operations

1.2 Selecting a WAN Technology

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
11
Cisco Networking Academy Program
Connecting Networks
Chapter 1: WAN Concepts

Selecting a WAN Technology
WAN Services
Two way that a business can get WAN access:
Private WAN Infrastructure
The business negotiates for dedicated or switched WAN access with a service provider.
Public WAN Infrastructure
WAN access is achieved through the Internet using broadband connections. VPNs secure the connections.

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
12
1.2 – Selecting a WAN Technology
1.2.1 – WAN Services

This topology illustrates some of these WAN access technologies.

Selecting a WAN Technology
WAN Services (cont.)

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
13
1.2 – Selecting a WAN Technology
1.2.1 – WAN Services

Selecting a WAN Technology
Private WAN Infrastructures
Advantages:
Simplicity
Quality
Availability

Disadvantages:
Cost
Limited flexibility

Dialup

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
14
1.2 – Selecting a WAN Technology
1.2.2 – Private WAN Infrastructures

Selecting a WAN Technology
Private WAN Infrastructures (Cont.)
ISDN

ISDN BRI
ISDN PRI
Sample ISDN Topology

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
15
1.2 – Selecting a WAN Technology
1.2.2 – Private WAN Infrastructures

Selecting a WAN Technology
Private WAN Infrastructures (Cont.)
Frame Relay
PVCs carry both voice and data traffic.
PVCs are uniquely identified by a data-link connection identifier (DLCI).
PVCs and DLCIs ensure bidirectional communication from one DTE device to another.
R1 uses DLCI 102 to reach R2 while R2 uses DLCI 201 to reach R1.

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
16
1.2 – Selecting a WAN Technology
1.2.2 – Private WAN Infrastructures

Selecting a WAN Technology
Private WAN Infrastructures (Cont.)
ATM
Built on a cell-based architecture, rather than on a frame-based architecture. ATM cells are always a fixed length of 53 bytes.

Presentation_ID
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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
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1.2 – Selecting a WAN Technology
1.2.2 – Private WAN Infrastructures

Selecting a WAN Technology
Private WAN Infrastructures (Cont.)
Ethernet WAN
Features and Benefits of Ethernet WAN include:
Reduced expenses and administration
Easy integration with existing networks
Enhanced business productivity
Service providers now offer Ethernet WAN service using fiber-optic cabling.
Known as Metropolitan Ethernet (MetroE), Ethernet over MPLS (EoMPLS), and Virtual Private LAN Service (VPLS).

Note: Commonly used to replace the traditional Frame Relay and ATM WAN links.

Selecting a WAN Technology
Private WAN Infrastructures (Cont.)
MPLS
Multiprotocol Label Switching (MPLS) is a multiprotocol high-performance WAN technology that directs data from one router to the next, based on short path labels rather than IP network addresses.

Selecting a WAN Technology
Private WAN Infrastructures (Cont.)
VSAT
Very small aperture terminal (VSAT) – a solution that creates a private WAN using satellite communications.

Selecting a WAN Technology
Public WAN Infrastructures
DSL
Always-on connection technology that uses existing twisted-pair telephone lines to transport high-bandwidth data, and provides IP services to subscribers.
A DSL modem converts an Ethernet signal from the user device to a DSL signal, which is transmitted to the central office.

Selecting a WAN Technology
Public WAN Infrastructures (Cont.)
Cable
Network access is available from some cable television networks.
Cable modems provide an always-on connection and a simple installation.

Selecting a WAN Technology
Public WAN Infrastructures (Cont.)
Wireless
New developments in broadband wireless technology:
Municipal Wi-Fi – Many cities have begun setting up municipal wireless
WiMAX – Worldwide Interoperability for Microwave Access (WiMAX) is a new technology that is just beginning to come into use.
Satellite Internet – Typically used by rural users where cable and DSL are not available.

Selecting a WAN Technology
Public WAN Infrastructures (Cont.)
3G/4G
Common cellular industry terms include:
3G/4G Wireless – Abbreviation for 3rd generation and 4th generation cellular access. These technologies support wireless Internet access.
Long-Term Evolution (LTE) – A newer and faster technology, considered to be part of the 4th generation (4G) technology.

Selecting a WAN Technology
Public WAN Infrastructures (Cont.)
Public WANs rely on VPNs for securing data between private networks as it crosses a public network, such as the Internet.
Benefits:
Cost savings
Security
Scalability
Compatibility with broadband technology
Two types of VPN:
Site-to-site VPNs
Remote-access VPNs

Site-to-Site
Remote-Access

Selecting a WAN Technology
Selecting WAN Services
Answer the following questions when choosing a WAN Connection:

WAN access standards operate at Layers 1 and 2 of the OSI model.
Permanent, dedicated point-to-point connections are provided by using leased lines.
Private WAN connections include:
Dialup
ISDN
Frame Relay
ATM
Metro Ethernet
MPLS
VSAT
Security over public infrastructure connections can be provided by using remote-access or site-to-site Virtual Private Networks (VPNs).
Chapter Summary
Summary
Public WAN connections include:
DSL
Cable
Wireless
Cellular

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