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    WANs

    A WAN is a network that spans a large geographical area.
    A WAN is organized to allow each segment or section of a network to be situated in a different building, city, state, or even country.
    WANs are connected by a variety of communication links.

    Communication Links
    WANs are often constructed by linking individual LANs. Links include:

      Packet switching networks
      Fiber optic cable
      Microwave transmitters
      Satellite links
      Cable television systems

    Link Technologies

      Analog
      Digital
      Packet Switching

    Analog Connectivity
    Public switched telephone service (PSTN)

      AKA Plain old telephone service (POTS)
      Slow and inconsistent
    A step up from POTS is a leased (or dedicated) line.
      Due to conditioning, a leased possess increased line quality.
      Since a leased line is not switched, it also has more quality.

    Digital Connectivity

      Digital Data Services (DDS) lines are direct or point to point synchronous communication links with various bandwidths.
      All digital lines require a CSU/DSU (Channel Service Unit/Data Service Unit) between the network connection device and the outside line.

    T1 Lines

      Full duplex at a maximum rate of 1.544 Mbps.
      Because 24 individual channels, 64 Kbps each, make up a T-1 line, fractional T-1 is usually available.

    Multiplexing enables several communication streams to travel simultaneously over the same cable segment.

    Packet Switching Networks

      Fast, efficient, and highly reliable.
      Data delivery does not depend on any single pathway between the origin and the destination.
      Frame relay is an advanced fast packet variable length, digital, packet switching technology.

    Provides bandwidth as needed.

      Utilizes a PVC.

    Virtual Circuits

      Virtual circuits provide temporary dedicated pathways between two points on a digital network.
        A virtual circuits can be Switched or Permanent.

    Virtual private networks represent temporary or permanent connections across a public network.

      Point to Point Tunneling Protocol (PPTP)

    Advanced WAN Technologies

    X.25 provides an interface between public packet switching networks and their customers.

      Can utilize a PAD (packet assembler/dissambler) that supports X.25 communication for low speed character based terminals.

    ISDN Integrated Services Digital Network

      A cost effective nondedicated link.

    Frame Relay

      A point to point PVC technology, offers WAN communications over a fast, reliable, digital packet switching network.
        Uses variable length packets.

    ATM Asynchronous Transfer Mode

      Uses a 53 byte fixed length cell for transmission rates up to 622Mbps.

    SONET

      Synchronous Optical Network uses fiber optic media to transmit voice, data, and video at speeds in multiples of 51.84 Mbps.