5/2/2014 Characteristics of WANs Covers large geographical areas Circuits provided by a common carrier Consists of interconnected switching nodes Traditional WANs provide modest capacity • 64000 bps common • Business subscribers using T1 service – 1.544 Mbps common Higher-speed WANs use optical fiber and transmission technique known as asynchronous transfer mode (ATM) • 10s and 100s of Mbps common
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5/2/2014
Characteristics of WANs
Covers large geographical areas
Circuits provided by a common carrier
Consists of interconnected switching nodes
Traditional WANs provide modest capacity
• 64000 bps common
• Business subscribers using T1 service – 1.544 Mbps common
Higher-speed WANs use optical fiber and transmission technique known as asynchronous transfer mode (ATM)
• 10s and 100s of Mbps common
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Wide Area Networks
Alternative technologies
• Circuit switching
• Packet switching
• Frame relay
• Asynchronous Transfer Mode (ATM)
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Characteristics of LANs
Like WAN, LAN interconnects a variety of devices
and provides a means for information exchange
among them
Traditional LANs
• Provide data rates of 1 to 20 Mbps
High-speed LANS
• Provide data rates of 100 Mbps to 10 Gbps
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Differences between LANs and WANs
Scope of a LAN is smaller
• LAN interconnects devices within a single
building or cluster of buildings
LAN usually owned by organization that owns the
attached devices
• For WANs, most of network assets are not owned
by same organization
Internal data rate of LAN is much greater
Example Networks
The Internet
Connection-Oriented Networks: ATM
Ethernet
Wireless LANs: 802:11
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Architecture of the Internet
Overview of the Internet
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ATM Virtual Circuits
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ATM cell
The ATM Reference Model
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Ethernet
Architecture of the original Ethernet
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Wireless LANs
(a) Wireless networking with a base station.(b) Ad hoc networking.
Modems
(a) A binary signal
(b) Amplitude modulation
(c) Frequency modulation
(d) Phase modulation
The Local Loop: Modems, ADSL, and Wireless
Digital Subscriber Lines
Bandwidth versus distanced over category 3 UTP for DSL.
Digital Subscriber Lines
Operation of ADSL using discrete multitone modulation
A typical ADSL equipment configuration.
Wireless Local Loops
Frequency Division Multiplexing
Wavelength Division Multiplexing
Time Division Multiplexing
The T1 carrier (1.544 Mbps)
Time Division Multiplexing
Multiplexing T1 streams into higher carriers
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Techniques Used in Switched Networks
Circuit switching
• Dedicated communications path between two
stations
• E.g., public telephone network
Packet switching
• Message is broken into a series of packets
• Each node determines next leg of transmission for