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Semester 4 v3.1.1: WAN Technologies


Never heard of it... Provides long-distance connections at a lower data rate between ... Web, e-mail, Active Directory/NetWare/LDAP, storage and file servers, ... – PowerPoint PPT presentation

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Title: Semester 4 v3.1.1: WAN Technologies

Semester 4 v3.1.1WAN Technologies
  • MODULE 2
  • WAN Technologies

WAN? Never heard of it
  • Provides long-distance connections at a lower
    data rate between networking devices across a
    large geographical area.
  • ... unlike LANs, which generally connect end-user
    devices (eg. workstations, printers) across a
    small area (eg. a building).
  • Usually long-distance links owned and operated by
    telcos, and leased out to customers.
  • American WAN providers include Regional Bell
    Operating Companies (RBOCs), ATT (formerly SBC),
    Sprint, Verizon, Qwest, and MCI (formerly
  • Australian WAN providers include Telstra, SingTel
    Optus, Macquarie Telecom, AAPT, PowerTel, and
  • The Internet is a collection of WANs.

More on WANs
  • Devices in a WAN include
  • Routers
  • Modems (including CSU/DSUs and TA/NT1s)
  • Communications servers
  • WAN physical layer describes the connection
    between DTE and DCE, implemented by standards
    such as E1, E3, xDSL, and SONET.
  • WAN data link layer protocols include HDLC, PPP,
    Frame Relay, ISDN, ATM, SLIP, and SDLC.

WANs What Fits Where?
  • WAN link options
  • Last-mile access T1/E1, T3/E3, xDSL, optic fibre
  • Circuit-switched POTS, ISDN
  • Packet-switched X.25, Frame Relay, Metro
  • Cell-switched ATM
  • A variety of physical connectors are used for WAN
  • Serial links utilise RS-232 (unbalanced) V.35,
    X.21 (both balanced). These lines plug into Cisco
    routers with either DB-60 or Smart Serial
  • ISDN BRI and PRI utilise RJ-48c connectors

How are WANs used?
  • For every site an organisation has, theres at
    least one LAN established there.
  • Multiple LANs are connected by WANs... but LANs
    provide services, not just connectivity.
  • Web, e-mail, Active Directory/NetWare/LDAP,
    storage and file servers, CallManager (voice),
    MeetingPlace (collaboration)...
  • Important to design WANs to provide access to
    these services.
  • How much bandwidth does a service require?
  • Does a service require Quality of Service (QoS)
    for higher priority and reduced latency?

WAN Traffic Considerations
  • Basic set of services run on TCP
  • Web (HTTP), e-mail (POP3/SMTP), and file transfer
    (SMB/FTP) are connection-oriented... benefits
    from error-checking
  • Real-time data streams require UDP
  • Voice packets (RTP) and video traffic (H.323)
    require low latency and have no time for TCP
    overheads handshakes, re-transmissions, etc.

Which WAN?
  • E1 popular for last-mile access
  • Good balance between price and performance.
  • DSL suitable for home and small businesses
  • SLAs can guarantee bandwidth, but not QoS.
  • Lower latency due to deployment with ATM
  • Frame Relay can provide QoS controls, good for
    last-mile access
  • Pricey, older technology being phased out.
  • ATM also being phased out of last-mile usage
  • Developed for low latency and high capacity, but
    inefficient due to fixed cell sizes. Still used
    in several service provider (SP) backbones.
  • Metro Ethernet is on the rise
  • Highest bandwidth, QoS shaping and policing
  • Transition to all-IP infrastructure, ties in to
    new MPLS SP backbones.

Getting Layered with WANs
  • Which topology to employ?
  • Star? Partial mesh?
  • Hierarchical models can employ different
    technologies with different topologies at
    different layers
  • If a company grows, they can scale up their
    access layer without compromising a well-designed
    distribution or core layer.
  • Hierarchy can be compressed into two layers if
    three layers is deemed too complex or costly to

Welcome to my world )
  • Daniel Comarmond
  • Cisco Networking Academy Instructor
  • Systems Engineer Cisco Systems
  • E-Mail
  • MSN
  • Phone 61 2 8446-5037
  • Website http//
  • Take care, and SMILE!!! )
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