Purpose of WANs

  • A WAN operates beyond the geographic scope of a LAN.
  • WANs are used to interconnect the enterprise LAN to remote LANs in branch sites and telecommuter sites.
  • A WAN is owned by a service provider whereas a LAN is typically owned by an organization.
  • An organization must pay a fee to use the WAN service provider’s network services to connect remote sites.
  • Service providers provide links to interconnect remote sites for the purpose of transporting data, voice, and video.

Are WANs Necessary?

  • Without WANs, LANs would be a series of isolated networks.
  • As organizations expand, businesses require the ability to communicate between geographically separated sites. For example:
  • Regional or branch offices of an organization need to be able to communicate and share data with the central site.
  • Organizations need to share information with other customer organizations.
  • Employees who travel on company business frequently need to access the corporate network.
  • In addition, consumers now commonly communicate over the Internet with banks, stores, and other providers of goods and services.

WAN Operations : WANs in the OSI Model

  • WAN operations focus primarily on the physical and data link layer of the OSI Model.
  • Data link layer requirements include physical addressing, flow control and encapsulation.
  • WAN access standards are defined and managed by a number of recognized authorities:
  • Layer 1 protocols describe how to provide electrical, mechanical, operational, and functional connects to the services of a communications service provider.
  • Layer 2 protocols define how data is encapsulated and the mechanisms for transferring the resulting frames.

WAN Terminology

  • One primary difference between a WAN and a LAN is that a company must subscribe to an outside WAN service provider to use WAN carrier network services.
  • Terminology commonly used to describe WAN connections:
  • Customer Premises Equipment (CPE) –Consists of devices and inside wiring located on the enterprise edge connecting to a carrier
  • Data Communications Equipment (DCE) – Also called circuit-terminating equipment, the DCE consists of devices that put data on the local loop. The DCE primarily provides an interface to connect subscribers to a communication link on the WAN cloud.

WAN Terminology

  • Data Terminal Equipment (DTE) – The customer devices that pass the data from a customer network or host computer for transmission over the WAN. The DTE connects to the local loop through the DCE.
  • Demarcation Point – This is a point established in a building to separate customer equipment from service provider equipment.
  • Local Loop (“last mile”) – The actual copper or fiber cable that connects the CPE to the CO of the service provider.
  • Central Office (CO) – The CO is the local service provider facility or building that connects the CPE to the provider network.
  • Toll network – This consists of the long-haul, all-digital, fiber-optic communications lines and other equipment inside the WAN provider network.

WAN Devices

Circuit Switching

  • A circuit-switched network establishes a dedicated circuit (or channel) between endpoints before the users can communicate.

    • Establishes a dedicated virtual connection through the service provider network before communication can start.
    • All communication uses the same path.
    • The two most common types of circuit-switched WAN technologies are the public switched telephone network (PSTN) and the legacy Integrated Services Digital Network (ISDN).

Packet Switching

  • Network communication is most commonly implemented using packet-switched communication.

    • Segments traffic data into packets that are routed over a shared network.
    • Much less expensive and more flexible than circuit switching.
    • Common types of packet-switched WAN technologies are:
    • Ethernet WAN (Metro Ethernet),
    • Multiprotocol Label Switching (MPLS)
    • Frame Relay
    • Asynchronous Transfer Mode (ATM).

Modern WANs

  • Modern WANS have more connectivity options than traditional WANs.

    • Enterprises now require faster and more flexible WAN connectivity options.
    • Traditional WAN connectivity options have rapidly declined in use because they are either no longer available, too expensive, or have limited bandwidth.

Modern WAN Connectivity Options

New technologies are continually emerging. The figure summarizes the modern WAN connectivity options.

Dedicated broadband
Fiber can be installed independently by an organization to connect remote locations directly together.
Dark fiber can be leased or purchased from a supplier.
Packet-switched
Metro Ethernet – Replacing many traditional WAN options.
MPLS – Enables sites to connect to the provider regardless of its access technologies.
Internet-based broadband
Organizations are now commonly using the global internet infrastructure for WAN connectivity.

Ethernet WAN

Service providers now offer Ethernet WAN service using fiber-optic cabling.
The Ethernet WAN service can go by many names, including the following:

  • Metropolitan Ethernet (Metro E)
  • Ethernet over MPLS (EoMPLS)
  • Virtual Private LAN Service (VPLS)

There are several benefits to an Ethernet WAN:
Reduced expenses and administration
Easy integration with existing networks
Enhanced business productivity

Ethernet WANs have gained in popularity and are now commonly being used to replace the traditional serial point-to-point, Frame Relay and ATM WAN links.

MPLS

Multiprotocol Label Switching (MPLS)
is a high-performance service provider WAN routing technology to interconnect clients without regard to access method or payload.

  • MPLS supports a variety of client access methods (e.g., Ethernet, DSL, Cable, Frame Relay).
  • MPLS can encapsulate all types of protocols including IPv4 and IPv6 traffic.
  • An MPLS router can be a customer edge (CE) router, a provider edge (PE) router, or an internal provider (P) router.
  • MPLS routers are label switched routers (LSRs). They attach labels to packets that are then used by other MPLS routers to forward traffic.
  • MPLS also provides services for QoS support, traffic engineering, redundancy, and VPNs.

Public WAN And Private WAN

A private WAN is a connection that is dedicated to a single customer.

Private WANs provide the following:

  • Guaranteed service level
  • Consistent bandwidth
  • Security
    A public WAN connection is typically provided by an ISP or telecommunications service provider using the internet. In this case, the service levels and bandwidth may vary, and the shared connections do not guarantee security.
Download DSL LAB

RAS Configuration

#bba-group pppoe ISPGROUP
#virtual-template 1
#exit
#interface virtual-template 1
#ip unnumbered g0/0/1
#peer default ip address pool ISPPOOL
#ppp authentication chap
#exit
#ip local pool ISPPOOL 193.1.1.100 193.1.1.200
#interface g0/0/1
#pppoe enable group ISPGROUP
#exit
#do wr
#username U1 password #U1PASS
#username U2 password U2PASS

#bba-group pppoe SOHOGROUP
#virtual-template 2
#exit
#interface virtual-template 2
#ip unnumbered g0/0/2
#peer default ip address pool SOHOPOOL
#ppp authentication chap
#exit
#ip local pool SOHOPOOL 194.1.1.100 194.1.1.100
#interface g0/0/2
#pppoe enable group SOHOGROUP
#exit

#username SOHO password SOHOPASS
#ip route 192.168.10.0   255.255.255.0  194.1.1.100

SOHO Configration

#interface dialer 1
#encapsulation ppp
#ppp authen chap
#ppp chap password SOHOPASS
#ppp chap hostname SOHO
#dialer pool 1
#mtu 1492
#exit
#hostname SOHO
#do wr
#interface g0/0
#pppoe-client dial-pool-number 1
#no shutdown
#ip route 0.0.0.0  0.0.0.0  dialer 1

Frame Relay LAB
Frame Relay Configuration

HQ
conf t
interface g0/0
no shutdown
ip address 192.168.1.1 255.255.255.0
interface s0/0/0
ip address 10.0.0.1 255.255.255.0
encapsulation frame-relay
bandwidth 64
frame-relay map ip 10.0.0.2 102 broadcast
no shutdown

===================================
Branch1
interface g0/0
no shutdown
ip address 192.168.2.1 255.255.255.0
interface s0/0/0
ip address 10.0.0.2 255.255.255.0
encapsulation frame-relay
bandwidth 64
frame-relay map ip 10.0.0.3 203 broadcast
no shutdown


Branch2
interface g0/0
no shutdown
ip address 192.168.3.1 255.255.255.0
interface s0/0/0
ip address 10.0.0.3 255.255.255.0
encapsulation frame-relay
bandwidth 64
frame-relay map ip 10.0.0.1 301 broadcast
no shutdown

enable EIGRP or OSPF routing
HQ
router eigrp 100
no auto-summary
network 192.168.1.0
network 10.0.0.0
Branch1
router eigrp 100
no auto-summary
network 192.168.2.0
network 10.0.0.0
Branch2
router eigrp 100
no auto-summary
network 192.168.3.0
network 10.0.0.0

 

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WAN Quiz

Test Your Understanding

1 / 8

What is a characteristic of a WAN?

2 / 8

Which statement describes a characteristic of a WAN?

3 / 8

A small company with 10 employees uses a single LAN to share information between computers. Which type of connection to the Internet would be appropriate for this company?

4 / 8

Which type of network would be used by a company to connect locations across the country?

5 / 8

An intercity bus company wants to offer constant Internet connectivity to the users traveling on the buses. Which two types of WAN infrastructure would meet the requirements? (Choose two.)

6 / 8

To which two layers of the OSI model do WAN technologies provide services? (Choose two.)

7 / 8

A customer needs a metropolitan area WAN connection that provides high-speed, dedicated bandwidth between two sites. Which type of WAN connection would best fulfill this need?

8 / 8

A new corporation needs a data network that must meet certain requirements. The network must provide a low cost connection to sales people dispersed over a large geographical area. Which two types of WAN infrastructure would meet the requirements? (Choose two.)

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