Notes On Chapter One -- Introduction And Overview

• 1.1 Growth of Computer Networking
  • Clearly the use of computer networks has grown enormously during the last few decades and has had a dramatic effect on large portions of the world society and economy.
  • Knowledge of communications networks has become an important job skill for computer scientists.
  
  
• 1.2 Why Networking Seems Complex
  • There are many network technologies and many ways to connect networks together.
  • There really is no unified model of how networks are supposed to be designed.
  • There's no true agreement on terminology
  
  
• 1.3 The Five Key Aspects of Networking
  • 1.3.1 Network Applications and Network Programming
    • Computer software provides network services like email, file transfer, web browsing, computer telephone, teleconferencing and distributed databases. All are implemented using the same basic network functions.
    • Understanding network technology helps programmers write applications that are more reliable, correct and efficient.
  • 1.3.2 Data Communications
    • The term "data communication" refers to low-level technology for transmitting information through media.
    • Bandwidth, multiplexing and encryption are important at the data communications level, as well as at higher levels.
  • 1.3.3 Packet Switching and Networking Technologies
    • Packet switching technology is important because it allows many senders to use a network at the same time.
    • Routers direct packets between network nodes.
    • Different packet switching technologies are designed to accommodate varying needs for speed, distance and cost. Many technologies exist, and they differ in many of their details.
  • 1.3.4 Internetworking with TCP/IP
    • The Internet is a technology for allowing people using different kinds of network technologies to communicate. This is more practical than to try to create one network technology for all needs.
    • It is typically fairly easy for new technologies to be used in the (same old) Internet.
  • 1.3.5 Additional Networking Concepts and Technologies
• 1.4 Public and Private Parts of The Internet
  • 1.4.1 Public Network If a network is made available to anyone who can pay for the service, then it is a public network.
  • 1.4.2 Private Network On the other hand, if only members of a certain group are allowed to use a network, then it's a private network. Types of private network include:
    • Consumer
    • Small Office/Home Office (SOHO)
    • Small-To-Medium Business (SMB)
    • Large Enterprise
• 1.5 Networks, Interoperability, and Standards
  • Parts of a network have to interoperate suitably, else attempts to use the network for communication will fail. In particular, network components must be designed to support protocols - rules regarding how information is represented and transmitted.
  • It is important that protocols specify what actions will be taken in response to all conditions - abnormal occurrences (e.g. errors) as well as normal operating conditions.
  
  
• 1.6 Protocol Suites and Layering Methods
  • Different protocols are designed to handle different aspects of communication.
  • Families (suites) of protocols are designed to be combined to handle all aspects of communication, and to work together efficiently.
  • Layering is a design principle applied to networks.
  • Layer 1: Physical Protocols here specify transmission media.
  • Layer 2: Network Interface Communication between network hardware and higher/software layers (e.g. details of network addressing and packet size).
  • Layer 3: Internet Computer-to-computer communication, Internet addresses, Internet packet formats, packet segmentation schemes, error reporting.
  • Layer 4: Transport Application-to-application communication, data rate and congestion control, packet ordering.
  • Layer 5: Application Format and meaning of messages exchanged by applications, e.g. how does an application submitting e-mail for transmission communicate with the server that accepts the e-mail? Other applications include file transfer, web browsing, voice over IP, and video teleconferencing.
  
  
• 1.7 How Data Passes Through Layers
  • When an application sends data, it passes the data to protocol software operating at the next layer down (e.g. the transport layer), software at that layer places the data into packets and passes it along to software at the next layer down (e.g. Internet layer). In this way the data travels down the "protocol stack" through each software and hardware layer.
  • After reaching the physical layer, the packet travels over the network to the destination host.
  • When it reaches the destination host, it moves up through each layer from bottom to the top.
  
  
• 1.8 Headers and Layers
  • Each layer performs a computation or adds something to outbound data - something that helps insure communication happens as it should.
  • A layer on the sending computer may add information to packets (usually a 'header' and/or 'trailer').
  • The corresponding layer on the receiving computer removes that information and uses it.
  
  
• 1.9 ISO and the OSI Seven Layer Reference Model
  • The International Organization for Standardization (ISO) and International Telecommunications Union, Telecommunication Standardization Sector (ITU-T) jointly formed the ISO network layering model, which includes the following layers:
    • Layer 1: Physical
    • Layer 2: Data Link
    • Layer 3: Network
    • Layer 4: Transport
    • Layer 5: Session
    • Layer 6: Presentation
    • Layer 7: Application
  
  
• 1.10 The Inside Scoop
  • "efforts to develop and deploy OSI protocols were terminated"
  • This is basically because the TCP/IP model was favored by the people who built the Internet.
  
  
• 1.11 Remainder of the Text
  • Part One: brief introduction, network applications and network programming
  • Part Two: data communications and information transmission
  • Part Three: packet switching, packet technologies and categories of computer networks.
  • Part Four: internetworking, TCP/IP protocol family, IP addressing and Internet routing.
  • Part Five: topics that relate to networking as a whole - network performance, emerging technologies, network security, and network management