Feb. 4., 2002. Kåre J. K ristoffersen Networks and Protocols - Intr oduction 1 Networks and Protocols - What is really going on when we send emails and surf the web?
Dec 11, 2015
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 1
Networks and Protocols
- What is really going on when we send emails and surf the web?
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 2
The Book:
Computer Networking
A Top-Down Approach Featuring the Internet,
by James F. Kurose og Keith W. Ross, Addison-Wesley Longman, Inc., se http://www.awl.com/kurose-ross/
Kan købes på IT-Højskolen d. 6. – 7. Feb 2002 i lokale 1.05 fra 11.00 til 15.00. Pris: Kr. 645,-
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 3
Excercises and Instructors
Rooms: 3.15 and 3.16, Glentevej 67.
Monday Afternoon (13:00 – 15:30):
Anders Ejlev, ([email protected])
Monday Evening (19:00 – 21:30):
Sune Kloppenborg Jeppesen, ([email protected])
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Examination – June 2002
20 min individual oral examn without preparation, judged using the, Dansih 13-scale, external censor. It is allowed to bring a disposition (one sheet of A4 paper for each question) The book will be available at the exam.
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 5
Outline feb 4. 20021. What is the internet?2. What is a Protocol?3. Connection-Oriented service.4. Connectionless service.5. Multiplexing.6. Message switching (demo).7. Packet switching (demo).8. Routing.9. Access Networks.10. Delay and Packet loss i a network.11. Protocol Layering.12. Course overview.
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Some Internet Applications
•Streaming multimedia
•www
•File transfer
•Internet telephony
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 7
Some pieces of the Internet
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 8
A service description
The Internet:
• Allows distributed applications running on it’s end systems to exchange data with each other.
• Provides a connection-oriented and a connectionless service.
• Makes no promises about time of delivery.
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 9
What is a protocol?
A human protocol and a computer network protocol.
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 10
Definition (protocol):
A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 11
End systems, Clients and Servers
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 12
Connection-Oriented Service
1. Initial handshake.
2. Reliable data transfer, using acknowledgements.
3. Flow Control.
4. Congestion Control.
Note: The Transmission Control Protocol (TCP) implements a connection-oriented service.
Used by: Email, www, FTP, Telnet.
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 13
Connectionless Service
1. No Initial handshake.
2. Unreliable data transfer.
3. No Flow Control.
4. No Congestion Control.
Used by: audio on demand, intertenet telephony, …
Note: The User Datagram Protocol (UDP) implements a connectionless service.
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How to share a communication link?
1. In Curcuit switching (e.g. ordinary telephone) a curcuit is reserved for the duration of the session.
2. In Packet switching (e.g. internet) the ressource is used on demand.
Note: Sharing is called Multiplexing.
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Multiplexing (FDM)
Frequency-division multiplexing (FDM):
Each Connection gets 4 KHz of the total frequency spectrum.
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Multiplexing (TDM)
Time-division Multiplexing: Each connection get one slot in each Frame.
Frame
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Multiplexing for Packetswitching.
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Example: Message Switching
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 22
Example: Packet Switching
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 23
Demo: Packet Switching
Run the JAVA Applet on:
http://www.awl.com/kurose-ross/
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 24
Break
• Table Tennis
• Table soccer
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 25
Routing: Virtual Curcuit Networks
Incoming Interface Incoming VC# Outgoing Interface Outgoing VC#
1 12 3 22
2 63 1 18
3 7 2 17
1 97 3 87
… … … …
VC number translation table for PS1:
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 26
Routing: Datagram Networks
Tom Jones (name)
Walnut Street 421 (street)
Philadelphia (city)
Pennsylvania (state)
USA (country)
Using: Hierarchical adresse, e.g:
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Access Networks and Physical Media
•Residental access networks
•Institutional access networks
•Mobile access networks
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Residental Access Networks
• Modem (telephone line, e.g. 56 kbps)
• ISDN, 128 kbps
• ADSL, up to 8Mbps using frequency Multiplexing
- A high speed downstream channel 50 kHz – 1 MHz
- A medium-speed upstream channel 4 kHz – 50 kHz
- Ordinary telephone 0 – 4 kHz.
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 29
HFC: Hybrid Fiber coaxial cable
Note: Cable modem needed!
Note: HFC is a shared broadcast medium.
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Company Access Networks
A Local Area Network (LAN) is used to connect end systems to an edge router.
Ethernet: A shared medium using twisted-pair copper wire or coaxial cable.
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Mobile Access
AP = Access Point.
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Delay and packet-loss
Delay through router A:
- nodal processing delay+
- Queuing delay +
- Transmission delay+
- Propagation delay
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Traffic intensityPacket size: L bits
Transmission Rate: R bits/second
Average packet arrival: a packets / second
Traffic intensity: La/R
Hopefully: Traffic intensity < 1
If Traffic Intensity > 1 then queue will overflow and packets are lost.
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Average Queuing Delay
(Traffic Intensity)
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Protocol Layering
PDU = Protocol Data Unit.
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Internet Protocol stack
Feb. 4., 2002. Kåre J. Kristoffersen Networks and Protocols - Introduction 37
Moving data in a network