Cisco 2521LF - 2521LF Router Manual do Utilizador descarregar pdf (Página 9)

6-17CSE: Networking Fundamentals — WAN Basics

www.cisco.com

DSL

“Modem”

End User

DSL

“Modem”

DSL

• DSL is a pair of “modems” on each end of a copper wire pair

• DSL converts ordinary phone lines into high-speed data conduits

• Like dial, cable, wireless, and T1, DSL by itself is a transmission

technology, not a complete end-to-end solution

• End-users don’t “buy” DSL, they “buy” services, such as high-

speed Internet access, intranet, leased line, voice, VPN, and video

on demand

• Service is limited to certain geographical areas

Copper Loop

Ethernet ATM

Digital Subscriber Line (xDSL)

Server

Corporate

Network

6-18CSE: Networking Fundamentals — WAN Basics

www.cisco.com

Asynchronous Transfer Mode

(ATM)

• Technology capable of transferring voice, video, and

data through private and public networks

• Uses VLSI technology to segment data, at high

speeds, into units called cells

– 5 bytes of header information

– 48 bytes of payload

– 53 bytes total

• Cells contain identifiers that specify the data stream

to which they belong

• Capable of T3 (44 Mbps), E3 (34 Mbps), and SONET

transmission speeds (OC-1 at 51.84 Mbps to OC-12+)

• Primarily used in enterprise backbones or WAN links

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Cisco 2521LF - 2521LF Router Manual do Utilizador Página 9