Introduction

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Introduction Chapter 1

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Introduction. Chapter 1. Uses of Computer Networks. Business Applications Home Applications Mobile Users Social Issues. Business Applications of Networks. A network with two clients and one server. Business Applications of Networks (2). - PowerPoint PPT Presentation

Transcript of Introduction

Page 1: Introduction

Introduction

Chapter 1

Page 2: Introduction

Uses of Computer Networks

• Business Applications

• Home Applications

• Mobile Users

• Social Issues

Page 3: Introduction

Business Applications of Networks

A network with two clients and one server.

Page 4: Introduction

Business Applications of Networks (2)

The client-server model involves requests and replies.

Page 5: Introduction

Home Network Applications

• Access to remote information

• Person-to-person communication

• Interactive entertainment

• Electronic commerce

Page 6: Introduction

Home Network Applications (2)

In peer-to-peer system there are no fixed clients and servers.

Page 7: Introduction

Home Network Applications (3)

Some forms of e-commerce.

Page 8: Introduction

Mobile Network Users

Combinations of wireless networks and mobile computing.

Page 9: Introduction

Network Hardware

• Local Area Networks

• Metropolitan Area Networks

• Wide Area Networks

• Wireless Networks

• Home Networks

• Internetworks

Page 10: Introduction

Classification

Types of transmission technology

• Broadcast links

• Point-to-point links

Page 11: Introduction

Classification(2)

Classification of interconnected processors by scale.

Page 12: Introduction

Local Area Networks

Two broadcast networks(a) Bus(b) Ring

Page 13: Introduction

Metropolitan Area Networks

A metropolitan area network based on cable TV.

Page 14: Introduction

Wide Area Networks

Relation between hosts on LANs and the subnet.

Page 15: Introduction

Wide Area Networks (2)

A stream of packets from sender to receiver.

Page 16: Introduction

Wireless Networks

Categories of wireless networks:

• System interconnection

• Wireless LANs

• Wireless WANs

Page 17: Introduction

Wireless Networks (2)

(a) Bluetooth configuration(b) Wireless LAN

Page 18: Introduction

Wireless Networks (3)

(a) Individual mobile computers(b) A flying LAN

Page 19: Introduction

Home Network Categories

• Computers (desktop PC, PDA, shared peripherals• Entertainment (TV, DVD, VCR, camera, stereo, MP3)• Telecomm (telephone, cell phone, intercom, fax)• Appliances (microwave, fridge, clock, furnace, airco)• Telemetry (utility meter, burglar alarm, babycam).

Page 20: Introduction

Network Software

• Protocol Hierarchies• Design Issues for the Layers• Interfaces and services• Connection-Oriented and Connectionless Services• Service Primitives• The Relationship of Services to Protocols

Page 21: Introduction

Network SoftwareProtocol Hierarchies

Layers, protocols, and interfaces.

Page 22: Introduction

Protocol Hierarchies (2)

The philosopher-translator-secretary architecture.

Page 23: Introduction

Protocol Hierarchies (3)

Example information flow supporting virtual communication in layer 5.

Page 24: Introduction

Design Issues for the Layers

• Addressing• Transfer rule• Error Control• Flow Control• Disassemble and reassemble• Multiplexing• Routing

Page 25: Introduction

Design Issues for the LayersAddressing

• Each layer needs a mechanism for identifying senders and receivers

• Sender: a process on a machine• Receiver: a process on another machine

Page 26: Introduction

Design Issues for the LayersTransfer rule

• Simplex• Half-duplex• Full-duplex

Page 27: Introduction

Design Issues for the LayersError Control

• Physical lines are not perfect• Error-detecting or error-correcting codes• How the receiver tells the sender which messages have

been correctly received and which have not• Messages may be out of sequence• How the sender numbers the messages, how the receiver

deals with the messages arrive out of order

Page 28: Introduction

Design Issues for the LayersFlow control

• A fast sender may swamp a slow receiver with data• Method 1: some kind of feedback from the receiver to

announce it’s current situation• Method 2: limit the sender’s transmission rate

Page 29: Introduction

Design Issues for the LayersDisassemble & Reassemble

• Each layer could have different message size• Lower layer may disassemble upper layer’s message into

several smaller messages reassembled by receiving peer• Lower layer may gather several small messages into a

single large message to improve efficiency

Page 30: Introduction

Design Issues for the LayersMultiplexing

• The underlying layer may use the same connection for multiple, unrelated conversions

• The multiplexing and demultiplexing must be done transparently

Page 31: Introduction

Design Issues for the LayersRouting

• When multiple paths exist, a route must be chosen

Page 32: Introduction

Interfaces and services

• Entity: active elements in a layer, software entity or hardware entity

• Peers: entities in the same layer on different machines• Service provider and service user: the entities in layer n

implement a service used by layer n+1, layer n is called the services provider, layer n+1 is called service user

• SAPs: Service Access Points, the layer n SAPs are the places where layer n+1 can access the services offered

• IDU: Interface Data Unit, the information elements exchanged between neighboring layers via SAP

Page 33: Introduction

Interfaces and services(2)

• SDU: Service Data Unit, the information passed across the network to the peer entity and then up to layer n+1,it is filled into user data part of layer n PDUs

• PDU: Protocol Data Unit, the information exchanged between two peers

• ICI: Interface Control information, the control information in IDU

• PCI: Protocol Control Information, the control information in PDU

Page 34: Introduction

Interfaces and services(3)

Page 35: Introduction

Connection-Oriented and Connectionless Services

Six different types of service.

Page 36: Introduction

Service Primitives

• Requests: an entity wants the service to do some work

• Indication: an entity is to be informed about an event

• Response: an entity wants to respond to an event• Confirm: The response to an earlier request has

come back

Page 37: Introduction

Service Primitives (2)

服务用户

（ N+1）

服务提供者

（ N）

SYSTEM A

服务用户

（ N+1）

服务提供者

（ N）

SYSTEM B

RequestIndication

Response

Confirm

confirmed

RequestIndication

PDU

unconfirmed

Page 38: Introduction

Service Primitives (3)Example

1. CONNECT.request - request a connection to be established

2. CONNECT.indication - signal the called party

3. CONNECT.response - used by the callee to accept/reject calls

4. CONNECT.confirm – tell the caller whether the call was accepted

5. DATA.request – request that data be sent

6. DATA.indication – signal the arrival of data

7. DISCONNECT.request – request that a connection be released

8. DISCONNECT.indication – signal the peer about the request

Page 39: Introduction

Service Primitives (3)Example(2)

Page 40: Introduction

Services to Protocols Relationship

The relationship between a service and a protocol.

Page 41: Introduction

Reference Models

• The OSI Reference Model

• The TCP/IP Reference Model

• A Comparison of OSI and TCP/IP

• A Critique of the OSI Model and Protocols

• A Critique of the TCP/IP Reference Model

Page 42: Introduction

*Reference Models

The OSI reference model.

Page 43: Introduction

*Reference Models (2)

Page 44: Introduction

*Reference Models (3)

The TCP/IP reference model.

Page 45: Introduction

*Reference Models (4)

Protocols and networks in the TCP/IP model initially.

Page 46: Introduction

*Comparing OSI and TCP/IP Models

Concepts central to the OSI model

• Services

• Interfaces

• Protocols

Page 47: Introduction

A Critique of the OSI Model and Protocols

Why OSI did not take over the world

• Bad timing

• Bad technology

• Bad implementations

• Bad politics

Page 48: Introduction

Bad Timing

The apocalypse of the two elephants.

Page 49: Introduction

A Critique of the TCP/IP Reference Model

Problems:• Service, interface, and protocol not distinguished• Not a general model• Host-to-network “layer” not really a layer• No mention of physical and data link layers• Minor protocols deeply entrenched, hard to replace

Page 50: Introduction

Hybrid Model

The hybrid reference model to be used in this book.

Page 51: Introduction

Example Networks

• The Internet

• Connection-Oriented Networks: X.25, Frame Relay, and ATM

• Ethernet

• Wireless LANs: 802:11

Page 52: Introduction

The ARPANET

(a) Structure of the telephone system.(b) Baran’s proposed distributed switching system.

Page 53: Introduction

The ARPANET (2)

The original ARPANET design.

Page 54: Introduction

The ARPANET (3)

Growth of the ARPANET (a) December 1969. (b) July 1970.(c) March 1971. (d) April 1972. (e) September 1972.

Page 55: Introduction

NSFNET

The NSFNET backbone in 1988.

Page 56: Introduction

Internet Usage

Traditional applications (1970 – 1990)

• E-mail

• News

• Remote login

• File transfer

Page 57: Introduction

Architecture of the Internet

Overview of the Internet.

Page 58: Introduction

Ethernet

Architecture of the original Ethernet.

Page 59: Introduction

Wireless LANs

(a) Wireless networking with a base station.(b) Ad hoc networking.

Page 60: Introduction

Wireless LANs (2)

The range of a single radio may not cover the entire system.

Page 61: Introduction

Wireless LANs (3)

A multicell 802.11 network.

Page 62: Introduction

Network Standardization

• Who’s Who in the Telecommunications World• Who’s Who in the International Standards World• Who’s Who in the Internet Standards World

Page 63: Introduction

ITU

• Main sectors• Radio communications• Telecommunications Standardization• Development

• Classes of Members• National governments• Recognized private operators• Regional telecommunications organizations• Telecommunication vendors and scientific

organizations• Other interested organizations

Page 64: Introduction

IEEE 802 Standards

The 802 working groups. The important ones are marked with *. The ones marked with are hibernating. The one marked with † gave up.


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