© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Communicating over the Network Network Fundamentals – Lecture 2 (CCNA1 – Chapter 2)

2 ITD1388 NF (11/12) Lecture 2 Objectives  Describe the structure 結構 of a network, including the devices and media that are necessary for successful communications.  Explain the function 功能 of protocols 協定 in network communications.  Explain the advantages 好處 of using a layered model to describe network functionality.  Describe the role 角色 of each layer in two recognized network models: The TCP/IP model and the OSI model.  Describe the importance of addressing 編址 and naming schemes 方案 in network communications.

3 ITD1388 NF (11/12) Lecture 2 Network Structure  What is a network? Data or information networks capable of carrying many different types of communications  3 common elements of communication message 信息 source 來源, the channel/media 媒介, message destination 目的地 信息訊號 來源 加密解碼器傳送器接受器 目的地 傳送媒介 渠道

4 ITD1388 NF (11/12) Lecture 2 How messages are communicated  Data is sent across a network in small “chunks” called segments ( 段落 ) Segmentation: Breaking communication into pieces Multiplexing: Interleaving the pieces as they transverse the media 插入

5 ITD1388 NF (11/12) Lecture 2 Network components 成分  Hardware device; media  Software/service

6 ITD1388 NF (11/12) Lecture 2 Basic Network Components  Network devices / Intermediary 中間的 devices provide connectivity 連接 and ensure data flows in the network e.g. Router 路由器, Switch 交換器, Hub 中轉站, Wireless device, etc.  End devices provide services directly to end users is the interface between human and network e.g. PC, server, networked printers, etc.  Network media (medium) Network cable, wireless media

7 ITD1388 NF (11/12) Lecture 2 Role ( 作用 ) of end devices  Act as client or server or both 選擇路線 來自 流動 通過 到達

8 ITD1388 NF (11/12) Lecture 2 Basic Network Components  Network media Channel over which a message travels  Factors 要素 to choose the media Speed, Cost, Mobility 流動性 Distance Environment Data Amount Network Media Copper -electrical signal Fiber Optics -light pulse Wireless -infra-red, radio frequency

9 ITD1388 NF (11/12) Lecture 2 Software/Services  Services and processes are the communication programs, called software, that run on the networked devices. A network service provides information in response to a request.

10 ITD1388 NF (11/12) Lecture 2 Network Types  Local Area Networks (LANs) - A network serving a home, building or campus is considered a Local Area Network (LAN)

11 ITD1388 NF (11/12) Lecture 2 Network Types  Wide Area Networks (WANs) - LANs separated by geographic distance are connected by a network known as a Wide Area Network (WAN)

12 ITD1388 NF (11/12) Lecture 2 Network Types  Internet is defined as A global mesh of interconnected networks

13 ITD1388 NF (11/12) Lecture 2 Network Symbols

14 ITD1388 NF (11/12) Lecture 2 Protocols ( 協定 )  The importance of protocols and how they are used to facilitate communication over data networks A protocol is a set of predetermined ( 預先決定 ) rules ( 規則 ) to govern communications

15 ITD1388 NF (11/12) Lecture 2 Protocols Network protocols are used to allow devices to communicate successfully Message format Sharing method Error handling Set up and Termination

16 ITD1388 NF (11/12) Lecture 2 Technology independent Protocols  Different types of network devices can communicate using the same sets of protocols.  This is because protocols specify ( 詳細指明 ) network functionality ( 功能 ), not the technology ( 技術 ) of devices

17 ITD1388 NF (11/12) Lecture 2 Protocols in Network Communication  Protocol suites and industry standards A protocol suite 協議系列 is A group of inter-related protocols that are necessary to perform a communication function. They are implemented in software and hardware that is loaded on each host and network device. For example: TCP/IP suite A standard 標準 is A process or protocol that has been endorsed 認可 by the networking industry and ratified 批准 by a standards organization. For example:The Institute of Electrical and Electronics Engineers (IEEE); Internet Engineering Task Force (IETF)

18 ITD1388 NF (11/12) Lecture 2 Example of protocol suites  The interaction between a Web server and a Web browser as an example to explain the protocol suites

19 ITD1388 NF (11/12) Lecture 2 Layered Network Model  Benefits of using a layered model – include assists in protocol design fosters competition changes in one layer do not affect other layers provides a common language

20 ITD1388 NF (11/12) Lecture 2 Two basic types of networking models:  Protocol model It provides a model that closely matches the structure of a particular protocol suite. For example: TCP/IP model is a protocol model because it describes the functions that occur at each layer of protocols within the TCP/IP suite.  Reference model 參考模型 It provides a common reference for maintaining 保持 consistency 一致 within all types of network protocols and services. I ts primary purpose is to aid in clearer understanding of the functions and process involved. For example: Open Systems Interconnection (OSI) model Networking Models

21 ITD1388 NF (11/12) Lecture 2 TCP/IP Model  Created in the early 1970s and is referred to as the Internet model  Open Standard 譯成密碼 描述 對話 控制 不同的 決定 路線

22 ITD1388 NF (11/12) Lecture 2 Communication Process

23 ITD1388 NF (11/12) Lecture 2 Protocol Data Unit  Protocol data units 協議數據單元 (PDU) and encapsulation 封裝 Encapsulation process Protocol Data Unit

24 ITD1388 NF (11/12) Lecture 2 Process of sending and receiving messages

25 ITD1388 NF (11/12) Lecture 2 OSI Model  It provides a framework 架構 on which to build a suite of open systems protocols.  Unfortunately, the speed at which the TCP/IP based Internet was adopted, and the rate at which it expanded, caused the OSI Protocol Suite development and acceptance to lag behind.

26 ITD1388 NF (11/12) Lecture 2 Layers with TCP/IP and OSI Model  Compare OSI and TCP/IP model 應用層 展示層 會談層 實體層 資料鏈結層 網路層 傳輸層 應用層 傳輸層 網際網路層 網絡接達層

27 ITD1388 NF (11/12) Lecture 2 Addressing and Naming Schemes  Encapsulation 封裝 headers 表頭 are used to manage communication in data networks  Using the OSI model as a guide, we can see the different addresses and identifiers 識別號 that are necessary at each layer Port number IP Address MAC Address TCP Segment IP Packet Ethernet Frame

28 ITD1388 NF (11/12) Lecture 2 Addressing and Naming Schemes  Destination and source physical addresses is concerned with the delivery of messages on a single local network.  For example: In an Ethernet LAN, this address is called the Media Access Control (MAC) address.

29 ITD1388 NF (11/12) Lecture 2 Addressing and Naming Schemes  Destination and source logical network addresses are used to manage communication in different data networks.  For example: IP address

30 ITD1388 NF (11/12) Lecture 2 IP Address and MAC address  Use “ipconfig /all” to show the IP address and MAC address (Physical Address) of a PC

31 ITD1388 NF (11/12) Lecture 2 Addressing and Naming Schemes  Destination and Source port numbers are used to identify the source and destination processes for data communication.

32 ITD1388 NF (11/12) Lecture 2 Key Concepts of Chapter 2  Data Network Structures and Types End Devices, Intermediary Devices, Media, Software/Service LAN, WAN, Internet, Intranet  Message Transfer using Layers Benefits, Protocol Model and Reference Model (TCP/IP and OSI)  Addressing Schemes Encapsulation and PDUs Data, Segments, Packets, Frames and Bits