CISCO4 CHAPTER 1
WAN is a data communications network that operates beyond the geographic scope of a LAN. WAN allows the transmission of data across greater geographic distances. 3 Major characteristics of WANs
• Generally connect devices that are separated by a broader geographical area than can be served by a LAN. • Use the services of carriers, such as telephone companies, cable companies, satellite systems, and network providers. • Use serial connections of a various types to provide access to bandwidth over large geographic areas. LAN connects computers, peripherals, and other devices in a single building or the small geographical area.
Campus (Multiple LANs): usually with more than 100 employees in one or more floors or neighboring buildings.
The HIERARCHICAL NETWORK MODEL is a useful high-level tool for designing a reliable network infrastructure.
ACCESS LAYER – grants user access to network devices. Generally incorporates switched LAN devices with ports that provide connectivity to workstations and servers. DISRTRIBUTION LAYER – Aggregates the wiring closets, using switches to segment workgroups and insole network problems in a campus environment. CORE LAYER – A high-speed backbone that is designed t switch as as fast as possible.
WANs and the OSI Model
WAN operations focus primarily on Layer 1 and Layer 2.
Physical Layer (OSI Layer 1) protocols describe how to provide electrical, mechanical, operational, and functional connections to the services of a communications service provider. Data Link Layer (OSI Layer 2) protocols define how data is encapsulated for transmission toward a remote location and the mechanism for transferring the resulting frames.
Customer Premises Equipment (CPE) – The devices and inside wiring locate at the premises of the subscriber and connected with a telecommunication channel of a carrier.
Data Communications Equipment (DCE) also called circuit-terminating equipment, he DCE...
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