Chapter_7_Datalink Layer
电子信息专业英语(5)
山东信息职业技术学院电子工程系
计算机网络的优点(网络的主要功能)
The benefit of network is that it can transmit information rapidly and easily among widely separated people; people can share hardware and software resources on the network; a computer network can also provide high reliability by having alternative source of supply.
communication 通信 located in … 位于,坐落于 exchange
交换, 互换, 交流
山东信息职业技术学院电子工程系
say
adv 比方说,例如
Similarly, at a local level within, say, a single building or establishment, distributed communities of computer-based workstations use local communication networks to access expensive shared resources--for example, printers, copiers, disks, tapes, etc.--that are also managed by computers.
山东信息职业技术学院电子工程系
Unit Twelve Computer Networks
OSI参考模型详解
osi参考模型详解
OSI（Open System Interconnection，开放系统互连）七层网络模型称为开放式系统互联参考模型 ，是一个逻辑上的定义，一个规范，它把网络从逻辑上分为了7层。每一层都有相关、相对应的物理设备，比如路由器，交换机。OSI 七层模型是一种框架性的设计方法 ，建立七层模型的主要目的是为解决异种网络互连时所遇到的兼容性问题，其最主要的功使就是帮助不同类型的主机实现数据传输。它的最大优点是将服务、接口和协议这三个概念明确地区分开来，通过七个层次化的结构模型使不同的系统不同的网络之间实现可靠的通讯。
模型优点
建立七层模型的主要目的是为解决异种网络互连时所遇到的兼容性问题。它的最大优点是将服务、接口和协议这三个概念明确地区分开来：服务说明某一层为上一层提供一些什么功能，接口说明上一层如何使用下层的服务，而协议涉及如何实现本层的服务；这样各层之间具有很强的独立性，互连网络中各实体采用什么样的协议是没有限制的，只要向上提供相同的服务并且不改变相邻层的接口就可以了。网络七层的划分也是为了使网络的不同功能模块（不同层次）分担起不同的职责，从而带来如下好处： ● 减轻问题的复杂程度，一旦网络发生故障，可迅速定位故障所处层次，便于查找和纠错； ● 在各层分别定义标准接口，使具备相同对等层的不同网络设备能实现互操作，各层之间则相对独立，一种高层协议可放在多种低层协议上运行； ● 能有效刺激网络技术革新，因为每次更新都可以在小范围内进行，不需对整个网络动大手术； ● 便于研究和教学。 模型中数据传输图示
《高级计算机网络》
Functions of the Data Link Layer
• Provide service interface to the network layer
• Dealing with transmission errors • Regulating data flow
Slow receivers not swamped by fast senders
Framing
A character stream. (a) Without errors. (b) With one error.
编辑课件
Framing (2)
(a) A frame delimited by flag bytes. (b) Four examples of byte seq编u辑e课n件ces before and after stuffing.
● 校验和的计算与填入由硬件实现
编辑课件
Elementary Data Link Protocols
● 过程wait_for_event(&event), 接收一帧后： event={cksun_err , frame_arrival , timeout, network_layer_ready}
编辑课件
Error-Detecting Codes
Calculation of the polynomial code checksum.
编辑课件
3.3 Elementary Data Link Protocols
• An Unrestricted Simplex Protocol • A Simplex Stop-and-Wait Protocol • A Simplex Protocol for a Noisy Channel
OSI Data Link Layer WkispacesOSI数据链路层的wiki空间
Data stream
Segment
Packet
Frame Bits
HTTP, FTP,
TFTP, SMTP etc Application
TCP, UDP
IP
Ethernet, WAN technologies
Transport Internet
Network Access
time so one device can send at a time. Simple media access control.
M Rajab- 2019
Controlled media access
• Predictable, deterministic. • Each device is given a time when it may send,
and it most not send at any other time. • High overhead. • No collisions. • Token passing – each host in turn gets the
token and is allowed to send. • E.g. token ring, FDDI
Objectives
• Explain the role of Data Link layer protocols in data transmission.
• Describe how the Data Link layer prepares data for transmission on network media.
• Encapsulates packets by adding a frame header and trailer including appropriate addressing.
信息系统项目管理师、系统集成项目管理工程师考试常见英语单词汇总
信息系统项目管理师、系统集成项目管理工程师考试常见英语单词汇总在软考，信息系统项目管理师、系统集成项目管理工程师考试中，涉及了5分英语选择题。
涉及到的英语知识点比较多，为了大家方便备考，小僧加以归纳、整理。
分两部分，第一部分技术词汇，第二部分项目管理词汇。
一、涉及常见的信息应用系统、软件、网络应用技术、电子政务、电子商务、云计算、物联网、信息安全等。
▪IS------------- Information System 信息系统▪MIS-----------Management Information System 管理信息系统▪TPS-----------Transaction process System 事务处理系统▪DSS-----------Decision Support System 决策支持系统▪ERP-----------Enterprise Resource Planning 企业资源计划▪MRP----------Material Requirement Planning 物料需求计划▪MRPII--------Manufacturing Resource Planning 制造资源计划▪BSP------------Business System Planning 企业系统规划▪CAD------------Computer Aided Design 计算机辅助设计▪OCR------------Optical Character Recognition 光学字符识别▪SA-------------Structured Analisys 结构化分析方法▪OOA----------Object-Oriented Analysis 面向对象分析方法▪OOD----------Object-Oriented Design 面向对象设计▪OOP----------Object Oriented Programming 面向对象编程▪DFD----------Data Flow Diagram 数据流图▪DD------------Data Dictionary 数据字典▪E-R-----------Entity Relationship Diagram E-R图▪OLAP--------On-Line Analytical Processing 在线联机分析处理▪OLTP--------On-Line Transaction Processing 联机事物处理系统▪EDI-----------Electronic Data Interchange 电子数据交换▪CRM---------Customer Relationship Management 客户关系管理▪SCM----------Supply Chain Management 供应链管理▪Data Mining----------数据挖掘▪Data Warehouse----------数据仓库▪Database----------数据库▪Data Mart----------数据集市▪ITIL----------Information Technology Infrastructure Library 信息技术基础架构库▪ITSM----------IT Service Management IT服务管理▪Message----------消息▪Communication-----------消息通信▪UML----------Unified Modeling Language 统一建模语言▪Use case diagram----------用例图▪Class diagram----------类图▪Object diagram----------对象图▪Component diagram----------构件图▪Deployment diagram----------部署图▪State diagram----------状态图▪Sequence diagram----------序列图▪Collaboration diagram----------协作图▪Activity diagram----------活动图▪C/S---------- Client/Server 客户机/服务器▪B/S---------- Browser/Server 浏览器/服务器▪SOA----------Service Oriented Architecture 面向服务的体系结构▪Middleware----------中间件▪RPC----------Remote Procedure Call 远程过程调用▪Web Services----------Web服务▪SOAP----------Simple Object Access Protocol 简单对象访问协议▪WSDL----------Web Services Description Language Web服务描述语言▪UDDI----------Universal Description Discovery and Integration 通用描述、发现与集成服务▪XML-----------Extensible Markup Language 可扩展标记语言▪HTML----------Hypertext Markup Language 超文本标记语言▪Component----------构建▪Containe----------容器▪WorkFlow----------工作流▪WFMS---------- Workflow Management System 工作流管理系统▪CORBA---------- Common Object Request Broker Architecture 公共对象请求代理体系结构▪OMG---------- Object Management Group 对象管理组织▪DCOM-----------Distributed Component Object Model 分布式构件对象模型▪API-----------Application Programming Interface 应用程序编程接口▪Graphical User Interface-----------图形用户界面▪Logic View----------逻辑视图▪Development View----------开发视图▪Module View----------模块视图▪Process View----------进程视图▪Physical View----------物理视图▪Attribute----------属性▪Object----------对象▪Class----------类▪Inheritance----------继承▪Dependency----------依赖▪Generalization----------泛化▪Aggregation----------聚合▪Composite----------组合▪Association----------关联▪function---------函数▪template---------模板▪LAN---------- Local Area Network 局域网▪Ethernet----------以太网▪Token King----------令牌环网▪WAN----------- Wide Area Network 广域网▪Proxy----------代理▪Server----------服务器▪Workstation----------工作站▪Bridge-----------网桥▪Router----------路由器▪Gateway----------网关▪OSI----------Open System Interconnect 开放式互联系统▪Physical Layer----------物理层▪Datalink Layer----------数据链路层▪Network Layer----------网络层▪Transport Layer----------传输层▪Session Layer----------会话层▪Presentation Layer---------表示层▪Application Layer---------应用层▪Virus---------病毒▪Firewall---------防火墙▪Directory structure--------- 目录结构▪TCP----------Transmission Control Protocol 传输控制协议▪UDP----------User Datagram Protocol 用户数据包协议▪ARP----------Address Resolution Protocol 地址解析协议▪URL----------Uniform Resource Locator 统一资源定位器▪FTP----------File Transfer Protocol 文件传输协议▪DHCP----------Dynamic Host Configuration Protocol 动态主机设置协议▪PPTP---------- Point to Point Tunneling Protocol 点对点协议▪ATM----------Asynchronous Transfer Mode 异步传输模式▪DAS----------Direct-Attached Storage 直接连接存储▪NAS---------- Network Attached Storage 网络连接存储▪SAN---------- Storage Area Network 存储区域网络▪PDS----------Premises Distribution System 综合布线系统▪Work Area Subsystem---------- 工作区子系统▪Horizontal Backbone Subsystem---------- 水平干线子系统▪Administrator Subsystem---------- 设备间子系统▪Backbone Subsystem---------- 垂直干线子系统▪Campus Backbone Subsystem---------- 楼宇▪Equipment Room Subsystem----------设备间子系统▪SQA----------Software Quality Assurance软件质量保证▪Performance----------性能▪Reliability----------可靠性▪Availability----------可用性▪Security----------安全性▪Modifiability----------可修改性▪Maintainability----------可维护性▪Extendibility----------可扩展性▪Reassemble----------结构重组▪Portability---------可移植性▪Functionality--------功能性▪FDMA----------Frequency Division Multiple Access 频分多址▪WDMA---------Wave Division Multiple Access 频分多址▪TDMA----------Time Division Multiple Access 时分多址▪CDMA----------Code Division Multiple Access 码分多址▪ADSL----------Asymmetric Digital Subscriber Line 非对称数字用户环境▪HDSL----------High-speed Digital Subscriber Line 高速率数字用户体验▪VDSL----------Very-high-bit-rate Digital Subscriber loop 甚高速数字用户环境。
《电子商务概论》教案
《电子商务概论》教案课时序第 2 讲（次）授课日期课题网络的基础知识与Internet的形成教学目的与要求1.熟悉网络定义与构成及进展的4个阶段2掌握网络的分类（按拓扑结构分）3.熟悉网络的体系结构与要紧联网设备，Internet的进展4掌握互联网协议TCP/IP，与与OSI/ISO的区别教学重点与难点1.网络的拓扑结构2TCP/IP教学方法与手段多媒体讲授教具与挂图电脑、常见网线等课后小结教学过程：案例一：中国互联网络的进展统计CNNIC报告案例二：从IPv4到IPv6的进展（案例详见PPT课件）2.1网络基础知识2.1.1计算机网络进展历史1、网络进展的四个阶段①面向终端的计算机网络起源于20世纪40年代末期，特点：计算机为中心的远程联机系统，终端尽管通过通信系统相连，但不具备处理能力。
本阶段典型代表：20世纪60年代的SABRE(美国机票预定系统)单机系统的典型结构示意②计算机互联网络阶段20世纪60年代后期开始兴起的，是由多台主计算机通过通信线路互联起来为用户提供服务。
与第一代区别是这里的多台主计算机都具有自主处理能力，它们之间不存在主从关系。
图3 单机式网络与互联网络逻辑上的区别第二代计算机网络的典型代表是ARPA网(ARPAnet)。
③开放式标准化网络计算机网络系统是非常复杂的系统，为实现网络资源共享，计算机网络使用分层解决问题的方法。
国际标准化组织ISO（International Standards Organization）于1977年成立了专门的机构来研究该问题，在1984年正式颁布了"开放系统互连基本参考模型"（Open System Interconnection Basic Reference Model）的国际标准OSI。
第三代计算机网络具有统一的网络体系结构、遵循国际标准化协议。
标准化使得不一致的计算机能方便地互联在一起。
开放式标准化网络的著名例子就是国际互联网，它是在原ARPAnet基础上通过改造而逐步进展起来的，它对任何计算机开放，只要遵循TCP/IP协议套的标准并申请到IP地址，就能够通过信道接人Internet。
07-DataLinkControl - New
ARQ, ACK, REJ, SREJ, RR, RNR
High Level Data Link Control (HDLC)
Primary/Secondary/Combined station
Unbalanced/balanced configuration
Transmission/propagation time Stop-and-wait flow control Sliding window flow control
"Great and enlightened one," said Ten-teh, as soon as his stupor was lifted, "has this person delivered his message competently, for his mind was still a seared vision of snow and sand and perchance his tongue has stumbled?" "Bend your ears to the wall," replied the Emperor, "and be assured." —Kai Lung's Golden Hours, Earnest Bramah
计算机网络第4版(自顶向下方法)英文版ppt
connect adjacent nodes along communication path are links
wired links wireless links LANs
layer-2 packet is a frame,
encapsulates datagram
data-link layer has responsibility of transferring datagram from one node to adjacent node over a link
services:
error detection, correction sharing a broadcast channel: multiple access link layer addressing reliable data transfer, flow control: done!
each link protocol
tourist = datagram
provides different services
transport segment =
e.g., may or may not provide rdt over link
communication link transportation mode = link layer protocol travel agent = routing algorithm
5-11
Parity Checking
Single Bit Parity:
Detect single bit errors
Two Dimensional Bit Parity:
Data Link Layer.ppt
Ethernet – CSMA/CD Token ring – Token passing FDDI – Dual ring
When the workstation completes transmitting, the token is released back to the network
logical link control (LLC) media access control (MAC)
logical link control (LLC)
starts and maintains connections between devices.
when you send data from your workstation to a server on the same network segment, LLC sub-layer establishes a connection with that server
Examples are 802.11a, 802.11g, 802.11n
802.2
Standard defining Logical Link Control (LLC)
responsible for the data transmission between computers or devices on a network
Data Link Layer
B. Konkoth
PDU
Protocol Data Unit
A unit of data which is specified in a protocol of a given layer
3rdeditionchapter5eeamptlecturenotes第三版eeampt讲义
collision if node receives two or more signals at the same time
multiple access protocol
distributed algorithm that determines how nodes share channel, i.e., determine when node can transmit
communication about channel sharing must use channel itself!
no out-of-band channel for coordination
DataLink Layer 2-12
Ideal Multiple Access Protocol
Link Layer: Introduction
Some terminology:
hosts and routers are nodes communication channels that
connect adjacent nodes along communication path are links
“link”
DataLink Layer 2-1
Link Layer Functions
Framing Error control Addressing and Multiple-access control Flow control Reliable transfer
DataLink Layer 2-2
two or more transmitting nodes ➜ “collision〞,
random access MAC protocol specifies:
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© 2007 Cisco Systems, Inc. All rights reserved.
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Data Link Layer – Accessing the Media
Describe the role of framing in preparing a packet for transmission on a given media
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Media Access Control Addressing and Framing Data Describe the role of addressing in the Data Link layer and identify cases where addresses are needed and cases where addresses are not needed
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Media Access Control Techniques
Contrast logical and physical topologies
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Media Access Control Techniques
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Data Link Layer – Accessing the Media
Describe why Data Link layer protocols are required to control media access
OSI Data Link Layer
Network Fundamentals – Chapter 7
Version 4.0
© 2007 Cisco Systems, Inc. All rights reserved.
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Objectives
Explain the role of Data Link layer protocols in data transmission. Describe how the Data Link layer prepares data for transmission on network media. Describe the different types of media access control methods. Identify several common logical network topologies and describe how the logical topology determines the media access control method for that network. Explain the purpose of encapsulating packets into frames to facilitate media access. Describe the Layer 2 frame structure and identify generic fields. Explain the role of key frame header and trailer fields including addressing, QoS, type of protocol and Frame Check Sequence.
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Media Access Control Techniques
Identify two media access control methods for shared media and the basic characteristics of each
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Media Access Control Addressing and Framing Data Describe the importance of the trailer in the Data Link layer and its implications for use on Ethernet, a "nonreliable" media
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Media Access Control Techniques
Explain the necessity for controlling access to the media
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Identify the characteristics of point-to-point topology and describe the implications for media access when using this topology
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© 2007 Cisco Systems, Inc. All rights reserved.
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Data Link Layer – Accessing the Media
Describe the role the Data Link layer plays in linking the software and hardware layers
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Media Access Control Techniques
Identify the characteristics of ring topology and describe the implications for media access when using this topology
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Media Access Control Addressing and Framing Data Describe the purpose of encapsulating packets into frames to facilitate the entry and exit of data on media
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Media Access Control Techniques
Identify the characteristics of multi-access topology and describe the implications for media access when using this topology
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Media Access Control Addressing and Framing Data Describe the role of the frame header in the Data Link layer and identify the fields commonly found in protocols specifying the header structure
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Media Access Control Techniques
Define Full Duplex and Half Duplex Access Control for non-shared media
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© 2007 Cisco Systems, Inc. All rights reserved.
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Data Link Layer – Accessing the Media
Describe the service the Data Link Layer provides as it prepares communication for transmission on specific media
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Summary
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Media Access Control Techniques
Describe the purpose of a logical topology and identify several common logical topologies