2.2 Network hardware-scale
2.2.1 Network hardware-scale
Personal Area Networks
2.2.2 Network hardware-scale
Local Area Networks
2.2.3 Network hardware-scale
applicatictions
Home applications
• • • •
Twitter Youtube Facebook Ubiquitous computing
• • • •
Smart phone GPS M-commerce Wearable computer
Mobile users
Social issues
Since computer scientists like to have their cake and eat it, too, we will use the hybrid model of Fig. 1-23 as the framework for this book.
4.1 Reference models-OSI
4.1 Reference models-OSI
4.2 Reference models-TCP/IP
4.3 Reference models- Used in This Book
目前在计算机网络领域有影响的标准化组织： 1、国际电信联盟（ITU) 2、国际标准化组织（ISO） 3、电子工业协会（EIA） 4、电气与电子工程师协会（IEEE） 5、ATM论坛
Network hardware Network software
Reference models
4 Reference models
Although the protocols associated with the OSI model are not used any more, the model itself is actually quite general and still valid, and the features discussed at each layer are still very important. The TCP/IP model has the opposite properties: the model itself is not of much use but the protocols are widely used.
3.3 Network software-interface
interface
Interface is a connection point which exchange of information between the adjacent layers.
The interface defines which primitive operations and services the lower layer makes available to the upper one.
Metropolitan Area Networks
2.2.4 Network hardware-scale
Wide Area Networks
Uses of computer networks
Network hardware Network software
Reference models
3 Network software
Point-topoint
• Point-to-point links connect individual pairs of machines
broadcast
• On a broadcast network,the communication channel is shared by all the machines on the network
COMPUTER NETWORKS
ห้องสมุดไป่ตู้
TEACHER: HUAN
Uses of computer networks
Network hardware Network software
Reference models
1 Uses of computer networks
• • • •
Resource sharing(VPN) E-mail Desktop sharing E-commerce Business
3.2 Network software-protocol
protocol A protocol is an agreement between the communicating parties on how communication is to proceed.
As an analogy,when a woman is introduced to a man, she may choose to stick out her hand. He,in turn, may decide to either shake it or kiss it, depending, for example, on whethershe is an American lawyer at a business meeting or a European princess at a formal ball. Violating the protocol will make communication more difficult, if not completely impossible.
3.4 Network software-service
service
A service is a set of operations that a layer provides to the layer above it. A service relates to an interface between two layers, with the lower layer being the service provider and the upper layer being the service user. Layers can offer two different types of service to the layers above them: connectionoriented and connectionless.
Layer
Protocol service
Connect-oriented service Connectless service
Network architecture
3.1 Network software-layer
layer To reduce their design complexity, most networks are organized as a stack of layers or levels, each one built upon the one below it. The purpose of each layer is to offer certain services to the higher layers while shielding those layers from the details of how the offered services are actually implemented.
3 Network software
3.4 Network software-network architecture
A set of layers and protocols is called a network architecture.
network architecture
Dutch
Uses of computer networks
• • • •
Sharing problems Piracy Privacy Law problems
Uses of computer networks
Network hardware Network software
Reference models
2.1 Network hardware-transmission technology