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Pertemuan 1 WAN

Discussion Topics

• Introduction to WANs• Introduction to routers in a WAN• Router LANs and WANs• Role of routers in a WAN• Academy approach to hands-on labs

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Introduction to WANs

• A WAN is a data communications network that spans a large geographic area such as a state, province, or country.

WAN Devices

The following devices are used in WANs:   •Routers offer many services, including internetworking and WAN interface ports. •Modems include interface voice-grade services, channel service units/digital service units (CSU/DSUs) that interface T1/E1 services, and Terminal Adapters/Network Termination 1 (TA/NT1s) that interface Integrated Services Digital Network (ISDN) services. •Communication servers concentrate dial in and dial out user communication.

WAN Services

Data Link Encapsulations

WAN data link protocols describe how frames are carried between systems on a single data link. They include protocols designed to operate over dedicated point-to-point, multipoint, and multi-access switched services such as Frame Relay. WAN standards are defined and managed by a number of recognized authorities, including the following agencies:

•International Telecommunication Union-Telecommunication Standardization Sector (ITU-T), formerly the Consultative Committee for International Telegraph and Telephone (CCITT) •International Organization for Standardization (ISO) •Internet Engineering Task Force (IETF) •Electronic Industries Association (EIA)

Routers Connected by WAN Technologies

Internal Configuration Components

RAM

RAM has the following characteristics and functions: •Stores routing tables •Holds ARP cache •Holds fast-switching cache •Performs packet buffering as shared RAM •Maintains packet-hold queues •Provides temporary memory for the configuration file of a router while the router is powered on •Loses content when a router is powered down or restarted

NVRAM , FLASH MEMORY

NVRAM has the following characteristics and functions: •Provides storage for the startup configuration file •Retains content when a router is powered down or restarted

Flash memory has the following characteristics and functions: •Holds the IOS image •Allows software to be updated without removing and replacing chips on the processor •Retains content when a router is powered down or restarted •Can store multiple versions of IOS software •Is a type of electrically erasable programmable read-only memory (EEPROM)

ROM , INTERFACE

ROM has the following characteristics and functions: •Maintains instructions for power-on self test (POST) diagnostics •Stores bootstrap program and basic operating system software •Requires replacing pluggable chips on the motherboard for software upgrades

Interfaces have the following characteristics and functions: •Connect routers to a network for packet entry and exit •Can be on the motherboard or on a separate module

Path Determination

Internetwork Routers

• Any internetwork must include the following: – Consistent end-to-end addressing – Addresses that represent network topologies – Best path selection – Dynamic or static routing – Switching

Academy Approach to Labs

• In the academy lab, all the networks will be connected with serial or Ethernet cables and the students can see and physically touch all the equipment.

• Devices that make up the WAN cloud are simulated by the connection between the back-to-back DTE-DCE cables.