Download - Comp net 2
![Page 1: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/1.jpg)
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
![Page 2: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/2.jpg)
5/2/2014
Wide Area Networks
Alternative technologies
• Circuit switching
• Packet switching
• Frame relay
• Asynchronous Transfer Mode (ATM)
![Page 3: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/3.jpg)
5/2/2014
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
![Page 4: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/4.jpg)
5/2/2014
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
![Page 5: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/5.jpg)
Example Networks
The Internet
Connection-Oriented Networks: ATM
Ethernet
Wireless LANs: 802:11
5/2/2014
![Page 6: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/6.jpg)
Architecture of the Internet
Overview of the Internet
5/2/2014
![Page 7: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/7.jpg)
ATM Virtual Circuits
5/2/2014
ATM cell
![Page 8: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/8.jpg)
The ATM Reference Model
5/2/2014
![Page 9: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/9.jpg)
Ethernet
Architecture of the original Ethernet
5/2/2014
![Page 10: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/10.jpg)
Wireless LANs
(a) Wireless networking with a base station.(b) Ad hoc networking.
![Page 11: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/11.jpg)
Modems
(a) A binary signal
(b) Amplitude modulation
(c) Frequency modulation
(d) Phase modulation
The Local Loop: Modems, ADSL, and Wireless
![Page 12: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/12.jpg)
Digital Subscriber Lines
Bandwidth versus distanced over category 3 UTP for DSL.
![Page 13: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/13.jpg)
Digital Subscriber Lines
Operation of ADSL using discrete multitone modulation
A typical ADSL equipment configuration.
![Page 14: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/14.jpg)
Wireless Local Loops
![Page 15: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/15.jpg)
Frequency Division Multiplexing
![Page 16: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/16.jpg)
Wavelength Division Multiplexing
![Page 17: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/17.jpg)
Time Division Multiplexing
The T1 carrier (1.544 Mbps)
![Page 18: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/18.jpg)
Time Division Multiplexing
Multiplexing T1 streams into higher carriers
![Page 19: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/19.jpg)
5/2/2014
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
each packet
![Page 20: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/20.jpg)
Circuit Switching
(a) Circuit switching.
(b) Packet switching.
![Page 21: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/21.jpg)
5/2/2014
Data sent out of sequence
Small size (packets) of data at a time
Packets passed from node to node between source
and destination
Used for terminal to computer and computer to
computer communications
Packet Switching
![Page 22: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/22.jpg)
Message Switching
(a) Circuit switching (b) Message switching (c) Packet switching
![Page 23: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/23.jpg)
Packet Switching
A comparison of circuit switched and packet-switched networks.
![Page 24: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/24.jpg)
5/2/2014
Effect of Packet Size on Transmission
Effect of Packet Size on Transmission time
![Page 25: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/25.jpg)
Propagation and Transmission Delay
Propagation Delay = Distance/Propagation speed
Transmission Delay = Message size/bandwidth bps
Latency = Propagation delay + Transmission delay +
Queueing time + Processing time
![Page 26: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/26.jpg)
5/2/2014
Performance comparison
Circuit switching Packet switching
![Page 27: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/27.jpg)
5/2/2014
Variable vs. Fixed-Length Packets
No Optimal Length
if small: high header-to-data overhead
if large: low utilization for small messages
Fixed-Length Easier to Switch in Hardware
simpler
enables parallelism
![Page 28: Comp net 2](https://reader031.vdocuments.net/reader031/viewer/2022020110/559b0fc61a28abb1498b458a/html5/thumbnails/28.jpg)
5/2/2014
Network Criteria
Performance
Depends on Network Elements
Measured in terms of Delay and Throughput
Reliability
Failure rate of network components
Measured in terms of availability/robustness
Security
Data protection against corruption/loss of data due to:
• Errors
• Malicious users