Communicating over the Network

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Communicating over the Network

Network Fundamentals – Lecture 2 (CCNA1 – Chapter 2)

2ITD1388 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.


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


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


Network components 成分 Hardware

device; media

Software/service


Basic Network Components

Network devices / Intermediary 中間的 devicesprovide 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 devicesprovide 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


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


Basic Network Components Network media

Channel over which a message travels

Factors 要素 to choose the mediaSpeed, Cost,

Mobility 流動性 Distance

Environment

Data Amount

Network Media

Copper

-electrical signal

Fiber Optics

-light pulse

Wireless

-infra-red, radio frequency


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.


Network Types Local Area Networks (LANs)

- A network serving a home, building or campus is considered a Local Area Network (LAN)


Network Types Wide Area Networks (WANs)

- LANs separated by geographic distance are connected by a network known as a Wide Area Network (WAN)


Network Types Internet is defined as

A global mesh of interconnected networks


Network Symbols


Protocols ( 協定 ) The importance of protocols and how they are used to

facilitate communication over data networksA protocol is a set of predetermined (預先決定 ) rules ( 規則 ) to govern communications


Protocols

Network protocolsare used

to allow devices to

communicate

successfully

Message format

Sharing method

Error handling

Set up and Termination


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


Protocols in Network Communication Protocol suites and industry standards

A protocol suite 協議系列 isA 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)


Example of protocol suites The interaction between a Web server and a Web

browser as an example to explain the protocol suites


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


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. Its primary purpose is to aid in clearer understanding of the functions and process involved. For example:

Open Systems Interconnection (OSI) model

Networking Models


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


Communication Process


Protocol Data Unit Protocol data units 協議數據單元 (PDU) and

encapsulation 封裝Encapsulation

process

ProtocolData Unit


Process of sending and receiving messages


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.


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


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 numberIP Address MAC Address

TCP Segment

IP Packet

Ethernet Frame


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.


Addressing and Naming Schemes Destination and source logical network addresses

are used to manage communication in different data networks.

For example: IP address


IP Address and MAC address Use “ipconfig /all” to show the IP address and MAC address (Physical Address) of

a PC


Addressing and Naming Schemes Destination and Source port numbers are used to

identify the source and destination processes for data communication.


Key Concepts of Chapter 2

Data Network Structures and TypesEnd Devices, Intermediary Devices, Media,

Software/Service

LAN, WAN, Internet, Intranet

Message Transfer using LayersBenefits, Protocol Model and Reference Model

(TCP/IP and OSI)

Addressing SchemesEncapsulation and PDUs

Data, Segments, Packets, Frames and Bits

Documents

Communicating over the Network