Semester 4 v3.1.1: WAN Technologies

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Semester 4 v3.1.1WAN Technologies

• MODULE 2
• WAN Technologies

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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
  WorldCom).
• Australian WAN providers include Telstra, SingTel
  Optus, Macquarie Telecom, AAPT, PowerTel, and
  TransACT.
• The Internet is a collection of WANs.

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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.

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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
  Ethernet
• Cell-switched ATM
• A variety of physical connectors are used for WAN
  links.
• 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
  connectors
• ISDN BRI and PRI utilise RJ-48c connectors

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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?

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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.

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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
  technology
• 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.

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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
  implement

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Welcome to my world )

• Daniel Comarmond
• CCNP, CCDP, CCSP, CCAI
• Cisco Networking Academy Instructor
• Systems Engineer Cisco Systems
• E-Mail dcom_at_it.uts.edu.au
• MSN dcom82_at_dcom82.com
• Phone [phone]
• Website http//www-staff.it.uts.edu.au/dcom
• Take care, and SMILE!!! )