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WAN is a data communications network that operates beyond a LAN’s geographic scope.

WAN is a data communications network that operates beyond a LAN’s geographic scope. One must subscribe to a WAN provider such as AT&T, Sprint, RBOC. They provide network services such as: Frame Relay Integrated Services Digital Network (ISDN) Asynchronous Transfer Mode (ATM)

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WAN is a data communications network that operates beyond a LAN’s geographic scope.

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  1. WAN is a data communications network that operates beyond a LAN’s geographic scope. • One must subscribe to a WAN provider such as AT&T, Sprint, RBOC. They provide network services such as: • Frame Relay • Integrated Services Digital Network (ISDN) • Asynchronous Transfer Mode (ATM) • Which carries traffic type of voice, data and video. • In general, WAN’s operate at the 1st three layers of the OSI. (Though Frame Relay actually operates at layer 1 and layer 2.) So all of the WAN services have layer 1 & layer 2 in common. • Other characteristics of WAN are: • operate beyond LAN geographic area • use serial connections • provide full-time & part-time connectivity

  2. Router’s Internal Components • The main internal components of the router are: • Random Access Memory (RAM) • Nonvolatile Random-Access Memory (NVRAM) • flash memory • Read-Only Memory (ROM) • Interfaces

  3. Router’s Internal Components • RAM: • stores routing tables • holds ARP cache • holds fast-switching cache • performs packet buffering • maintains packet-hold queues • provides temporary memory for the configuration file of the router while the router is powered on • loses content when router is powered down or restarted

  4. Router’s Internal Components • NVRAM: • provides storage for the startup configuration file • retains content when router is powered down or restarted

  5. Router’s Internal Components • Flash memory: • holds the operating system image (IOS) • allows software to be updated without removing & replacing chips on the processor • retains content when router is powered down or restarted • can store multiple versions of IOS software • is electronically erasable, programmable ROM (EEPROM)

  6. Router’s Internal Components • ROM: • maintains instructions for power-on self test (POST) diagnostics • stores bootstrap program & basic operating system software • requires replacing pluggable chips on the motherboard for software upgrades

  7. Router’s Internal Components • Interfaces: • connect router to network for frame entry & exit • can be on the motherboard or on a separate module • connect the router to LANs and WANs

  8. Subscriber to Provider Interface Modem Router DCE DTE A key interface in the customer site occurs between the Data Terminal Equipment (DTE) such as a router to the Data Circuit-Terminating equipment (DCE) to the WAN network such as a modem. DTE is on the customer’s side of the network. The DCE is a modem and in many cases is circuitry in a CO, switch which is made up of a CSU/DSU (Channel Service Unit/Data Service Unit). The major reason for CSU/DSU is to protect the equipment from CPE/DTE from aberrant voltages, and to ‘square’ up the signal. DCE is usually on the provider’s side.

  9. Subscriber to Provider Interface EIA/TIA-232, V.35, X.21, HSSI, others Modem Router DCE DTE

  10. Routers Physical Characteristics • The 3 basic types of connections on a router are: • LAN interfaces • WAN interfaces • Management ports • Console • auxiliary

  11. Routers Physical Characteristics • Management ports provide • Text-based connection • Configuration, monitoring, password recovery and troubleshooting • The management ports: • EIA-232 asynchronous serial ports • used for non-network connections • used for initial router configuration • to connect to a port, a PC must have a terminal emulation program • rollover cable from PC to the management ports

  12. Management Ports • The console port, says Cisco is preferred when troubleshooting: • doesn’t depend on network services • displays start and error messages by default • To establish a connection between PC and a router, one needs • terminal emulation software • rollover cable • RJ-45 to DB-9 connector

  13. Routers Physical Characteristics • Cisco says, the terminal emulation software, HyperTerminal, the parameters used to configure a router are: • Data bits • Stop bits • parity

  14. Router’s connection LAN & WAN • For a PC of a LAN to connect to a router, one • straight-thru cable from the PC to a HUB or switch • straight-thru cable from the HUB or switch to router’s Ethernet interface

  15. Router’s connection LAN & WAN • An internetwork must include: • switching • dynamic or static routing • consistent end-to-end addressing

  16. Router’s connection to LAN & WAN EIA/TIA-232, V.35, X.21, HSSI, others Modem Router DCE DTE • The connections to WAN on router is through the serial interface, either as a Smart Serial interface connector or DB-60 connector. • The following devices are used in the construction of a WAN: • communication servers • routers • modems

  17. Router vs. PC • Cisco says the common components between a router and PC are: • CPU • input/output interfaces • system bus

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