CCNA 4 v6.0 Study Material – 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.

1.1 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.

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
  • 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.

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.

  • 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

  • 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

1.2 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.

    • This topology illustrates some of these WAN access technologies.

Private WAN Infrastructures

      • Dialup
        • Advantages:
          • Simplicity
          • Quality
          • Availability
        • Disadvantages:
          • Cost
          • Limited flexibility

  • ISDN
    • Sample ISDN Topology
    • ISDN BRI
    • ISDN PRI
  • 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.

  • ATM
    • Built on a cell-based architecture, rather than on a frame-based architecture. ATM cells are always a fixed length of 53 bytes.
  • Ethernet WANFeatures 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.

  • MPLSMultiprotocol 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.

  • VSATVery small aperture terminal (VSAT) – a solution that creates a private WAN using satellite communications.

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.

  • Cable
      • Network access is available from some cable television networks.
      • Cable modems provide an always-on connection and a simple installation.

  • 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.

  • 3G/4GCommon 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.

    • 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

Selecting WAN Services

Answer the following questions when choosing a WAN Connection:

1.3 Summary


  • 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
  • Public WAN connections include:
    • DSL
    • Cable
    • Wireless
    • Cellular
  • Security over public infrastructure connections can be provided by using remote-access or site-to-site Virtual Private Networks (VPNs).

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