Download of the Internet

计算机网络与通信
授课班级: 软件工程111、112班
授课教师： 郑秋生
School of Computer Science
Zhongyuan University of Technology
http://www.cs.zzti.edu.cn
[email protected]
Sept. 2013
选用教材
计算机网络
Andrew S. Tanenbaum 第5版
严伟 潘爱民翻译
清华大学出版社
Computer Network
Andrew S. Tanenbaum，
5th ,Prentice-Hall Inc.
影印版，清华大学出版社
参考资料
1、Andrew S. Tanenbaum, David J. Wetherall,
“Computer Networks”, 5th Ed., 2010, AddisonWesley.该中文版的英文原版教材
2、James F. Kurose, Keith W. Ross, “Computer
Networks: A Top-Down Approach”, 5th Ed.,
2010, Addison-Wesley.
3、Larry L. Peterson, Bruce S. Davie, “Computer
Networks: A System Approach”, 5th Ed., 2011,
Elsevier.
4、 Computer Network and Internets, Douglas E.
Comer, 5th, 2009.
参考资料
5、网络协议分析，寇晓蕤、罗君勇、蔡延荣 编著，
机械工业出版社，2009
6、计算机网络与因特网，第5版翻译，机械工业出
版社，2009
7、计算机网络，谢希仁，第6版，电子工业出版社
8、计算机网络课程设计，吴功宜等，机械工业出
版社，2005
9、Douglas Comer, “Internetworking With TCP/IP
volume 1: Principles, Protocols, and
Architecture”, 5th Ed., 2006, Pearson.
The Most Important Journals
 IEEE-ACM Transaction on Networking：
Bimonthly，ISSN: 1063-6692
 IEEE NETWORK：
Bimonthly，ISSN: 0890-8044
The Most Important Conferences
 ACM SIGCOMM：
http://www.acm.org/sigcomm
 IEEE Infocom：
http://www.ieee-infocom.org
 ACM SIGMETRICS：
http://www.sigmetrics.org
China Computer Federation
CCF
 Evaluating academic achievement
 Class A is top important of journal and
conference
 Class B is very important of journal and
conference
 Class C is important of journal and
conference
 http://www.ccf.org.cn/sites/ccf/paiming.jsp
Websites and online courses
http://www.computernetworks5e.org
See:
Video Lectures for CN5E
Computer Networks MOOC
Chapter 1
Introduction
Chapter 1 Introduction
 Concepts:
 Computer Networks
 Distributed System
 World Wide Web
 Middleware
 Internet of Things 物联网
Uses of Computer Networks
1. Business Applications
2. Home Applications
3. Mobile Users
4. Social Issues
Business Applications of Networks
 A network with two clients and one server.
Business Applications of Networks (2)
 The client-server model involves requests
and replies.
Home Network Applications
 Access to remote information
 Digital Library: ACM,IEEE
 IM (Instant Message)
 Chat Room
 Person-to-person (P2P)communication
 Napster
 电驴
 Interactive entertainment
 Electronic commerce
Home Network Applications (2)
 In peer-to-peer system there are no fixed
clients and servers.
Home Network Applications (3)
 Some forms of e-commerce.
Mobile Network Users
 Combinations of wireless networks（无线
网络） and mobile computing.(移动计算)
1.2 Network Hardware
 Local Area Networks
 Metropolitan Area Networks
 Wide Area Networks
 Wireless Networks
 Home Networks
 Internetworks
Broadcast （广播）Networks
 Types of transmission technology
 Broadcast links
 Point-to-point links
Broadcast Networks (2)
 Classification of interconnected processors by scale.
1.2.1 Local Area Networks
 Three Characteristics:
 Size
 Transmission technology
 Topology
Local Area Networks
 Two broadcast networks
 (a) Bus
 (b) Ring
1.2.2 Metropolitan Area Networks
 A metropolitan area network based on cable TV.
1.2.3 Wide Area Networks
 Relation between hosts on LANs and the subnet.
Wide Area Networks (2)
 A stream of packets from sender to receiver.
1.2.4 Wireless Networks
 Categories of wireless networks:
 System interconnection
 Wireless LANs (802.11 a/b/g/n , Wi-Fi)
 Wireless WANs (802.16, Wi-Fi Max)
 GPRS、3G
Wireless Networks (2)
 Bluetooth configuration (802.15)
 Wireless LAN (802.11)
Wireless Networks (3)
 (a) Individual mobile computers
 (b) A flying LAN
1.2.5 Home Network Categories
 Computers (desktop PC, PDA, shared peripherals
 Entertainment (TV, DVD, VCR, camera, stereo, MP3)
 Telecomm (telephone, cell phone, intercom, fax)
 Appliances 家用电器 (microwave, fridge, clock, furnace,
airco)
 Telemetry遥测设备 (utility meter 抄表, burglar alarm,
babycam).
1.3 Network Software
从提出问题、解决问题的方法上理解、掌握
 Protocol Hierarchies
 Design Issues for the Layers
 Connection-Oriented and Connectionless Services
 Service Primitives （服务原语）
 The Relationship of Services to Protocols
1.3.1 Protocol Hierarchies (1)
 The philosopher-translator-secretary architecture.
• 复杂问题的
处理方法
• 分层思想
1.3.1 Protocol layers (2)
 Protocol layering is the main structuring method
used to divide up network functionality.
Physical communication
– Each layer
communicates only by
using the one below
– Lower layer services
are accessed by an
interface
– At bottom, messages
are carried by the
medium
– Each protocol instance
talks virtually to its peer
 Layers, protocols, and
interfaces.
Virtual communication
1.3.1 Protocol layers (3)
 Each lower layer adds its own header (with control
information) to the message to transmit and removes it
on receiver
 Layers may also split and join messages, etc.
1.4.1 Protocol layers (4)
 Information transmission unit
Protocol Hierarchies (5)
 Example information flow supporting virtual
communication in layer 5.
1.3.2 Design Issues for the Layers
为什么会有这些问题？如何解决？

Addressing

Error Control

Flow Control

Multiplexing

Routing
1.3.2 Design Issues for the Layers
 Each layer solves a particular problem but must include
mechanisms to address a set of recurring design issues
Issue
Example mechanisms at different layers
Reliability despite
failures
Codes for error detection/correction (§3.2, 3.3)
Routing around failures (§5.2)
Network growth
and evolution
Addressing (§5.6) and naming (§7.1)
Protocol layering (§1.3)
Allocation of resources Multiple access (§4.2)
like bandwidth
Congestion control (§5.3, 6.3)
Security against
various threats
Confidentiality of messages (§8.6)
Web security (§8.9)
1.3.3 Connection-Oriented and
Connectionless Services (1)
 Connection-oriented
must be set up for ongoing use (and torn
down after use)
e.g., phone call
 Connectionless
messages are handled separately
e.g., postal delivery
1.3.3 Connection-Oriented and
Connectionless Services (2)
 Six different types of service. //Quality of service
1.3.3 Connection-Oriented vs.
Connectionless (3)
 In connection-oriented service
 Establishes a connection, uses the connection,
and then releases the connection.
 When a connection is established, negotiation
has to do with getting both sides to agree on
some parameters or values to be used during
the communication.
 In the most cases the bits arrive to receiver in
the order they were sent
 Message sequences vs. byte streams
1.3.3 Connection-Oriented vs.
Connectionless (4)
 In connectionless service
 Store-and-forward switching vs. cut-through
switching
 It is possible that the messages arrive to
receiver out of order they were sent.
 Unreliable connectionless service is called
datagram （数据报）
 Reliable service vs. unreliable service
 Must have acknowledgement （确认） or
need not one
1.3.4 Service Primitives
 Five service primitives for implementing a simple
connection-oriented service.
1.3.4 Service Primitives (2)
 Hypothetical example of how these primitives
may be used for a client-server interaction
Server
Client
LISTEN (0)
CONNECT (1)
Connect request
Accept response
SEND (3)
RECEIVE
ACCEPT (2)
RECEIVE
Request for data
SEND (4)
Reply
DISCONNECT (5)
Disconnect
DISCONNECT (6)
Disconnect
1.3.5 Services to Protocols Relationship
 The relationship between a service and a protocol.
K层协议、K层服务
1.3.5 Services to Protocols Relationship
 A layer provides a service to the one
above [vertical]
 A layer talks to its peer using a protocol
[horizontal]
1.4 Reference Models
1. The OSI Reference Model
2. The TCP/IP Reference Model
3. A Comparison of OSI and TCP/IP
4. A Critique of the OSI Model and Protocols
5. A Critique of the TCP/IP Reference Model
自顶向下，自底向上的讨论、分析方法
1.4.1 The OSI Reference Model
Provides functions
needed by users
Converts different
representations
Manages task
dialogs
Provides end-to-end
delivery
Sends packets over
multiple links
Sends frames of
information
Sends bits as
signals
1.4.1 The OSI Reference Model
 A principled, international standard, seven layer
model to connect different systems
• The OSI reference model.
• 理解：end to end 端到端
• 7层模型
1.4.2 The TCP/IP Reference Model 4层
1.4.2 The TCP/IP Reference Model
 A four layer model derived from experimentation
 omits some OSI layers and uses the IP as the
IP is the “narrow waist
network layer.
细腰” of the Internet
Protocols are shown in their respective layers
1.4.3 Model used for this Course 5层
 It is based on the TCP/IP model but we call out
the physical layer and look beyond Internet
protocols.
1.4.4 Critique of OSI & TCP/IP
 OSI
+ Very influential model with clear concepts
 Models, protocols and adoption all bogged down
by politics and complexity
 TCP/IP
+ Very successful protocols that worked well
and thrived （兴盛）
 Weak model derived after the fact from
protocols
A Critique 缺点 of the OSI Model and Protocols
 Why OSI did not take over the world
 Bad timing
 Bad technology
 Bad implementations
 Bad politics
Bad Timing
 The apocalypse of the two elephants.
A Critique（批评） of the TCP/IP Reference Model
 Problems:
 Service, interface, and protocol not distinguished
 Not a general model
 Host-to-network “layer” not really a layer
 No mention of physical and data link layers
 Minor protocols deeply entrenched, hard to replace
1.5 Example Networks




The Internet
3G mobile phone networks
Wireless LANs
RFID and sensor networks
The ARPANET
 (a) Structure of the telephone system.
 (b) Baran’s proposed distributed switching system.
The ARPANET (2)
 The original ARPANET design.
The ARPANET (3)
 Growth of the ARPANET (a) December 1969. (b) July 1970.
 (c) March 1971.
(d) April 1972.
(e) September 1972.
NSFNET
 The NSFNET backbone in 1988.
Internet Usage





Traditional applications (1970 – 1990)
E-mail
News
Remote login
File transfer
Architecture of the Internet
 Overview of the Internet architecture
Internet
 Access network is the
physical links that connect
an end system to the edge
router
 The technology includes
 ADSL
 Ethernet
 FTTH
 WiFi
 WiMAX
 Mobile communication
…
From KUROSE & ROSS, Computer Networking: A Top-Down Approach, 5th Edition
Internet
 The modern Internet is more complex (1)
 ISP networks serve as the Internet backbone
 ISPs connect or peer to exchange traffic at
IXPs
 Within each network routers switch packets
 Between networks, traffic exchange is set by
business agreements
Internet
 The modern Internet is more complex (2)
 Customers connect at the edge by many
means
 Cable, DSL, Fiber-to-the-Home, 3G/4G wireless,
dialup
 Data centers concentrate many servers (“the
cloud”)
 Most traffic is content from data centers (esp.
video)
 The architecture continues to evolve
Internet
 ICANN (The Internet Corporation for
Assigned Names and Numbers)
announced ‘Available Pool of unallocated
IPv4 Internet Addresses Now Completely
Emptied’ in Feb. 3, 2011
 US, EU (European Union), and Japan
have scheduled for IPv4 to convert into
IPv6
Internet
Source: 邬贺铨, 《中国下一代互联网的研究和CNGI项目》, 2010.3.9
Internet
 China's Next Generation Internet (CNGI)
Source: 邬贺铨, 《中国下一代互联网的研究和CNGI项目》, 2010.3.9
1.5.2 3G mobile phone（移动电话）
networks (1)
 3G network is based on spatial cells; each cell
provides wireless service to mobiles within it via
a base station
1.5.2 3G mobile phone networks (2)
 Base stations connect to the core network to find other
mobiles and send data to the phone network and Internet
Architecture of UMTS 3G network
1.5.2 3G mobile phone networks (3)
 As mobiles move, base stations hand them off
from one cell to the next, and the network tracks
their location
 Soft handover vs. hard handover （交接）
Handover
1.5.2 3G mobile phone networks (4)
 Security
 SIM (Subscriber Identity Module) card
 Authentication
 Cryptographic keys on the chip are used to
encrypt transmissions
 Encryption cell phone
 3.5G
 4G and WiMAX
1.5.3 Wireless LANs 8.2.11
 Two different communication modes in 802.11
 Infrastructure wireless LAN: Clients communicate via
an AP (Access Point) that is wired to the rest of the
network.
 Ad hoc （自组织）networks: clients can communicate
directly in same radio rang.
1.5.3 Wireless LANs (2)
 Signals in the 2.4GHz ISM band vary in strength
due to many effects, such as multipath fading
（多经衰落） due to reflections
 requires complex transmission schemes, e.g., OFDM
1.5.3 Wireless LANs (3)
 Radio broadcasts interfere with each other, and
radio ranges may incompletely overlap
 CSMA (Carrier Sense Multiple Access) designs are
used
1.5.3 Wireless LANs (4)
 Mobility（移动性）
 Over a single 802.11 network
 Across different networks (IEEE 802.21)
 Security (802.11i)
 WEP (Wireless Equivalent Privacy 等效保密) was
flawed and broken
 WPA2 (WiFi Protected Access 保护访问)
 WAPI (Wireless Authentication Privacy Infrastructure
认证与保密基础结构(): China standard (GB 15629)
 通过互联网（百度百科、Wiki百科等），
了解以上技术
1.5.4 RFID & Sensor Networks
（传感器网络）(1)
 networks everyday objectsPassive UHF（无源超高频）
RFID
 Tags (stickers with not even a battery) are placed (or embedded)
on objects
 Backscatter（反向散射体）: readers send signals that the tags
reflect to communicate
1.5.4 RFID & Sensor Networks (2)
 The Category of RFID Tags
 Passive （无源）RFID tags have neither an electric
plug nor a battery.
 Active（有源） RFID has a power source in the tag.
 The Category Frequency of RFID
 UHF RFID (Ultra-High Frequency RFID) tags
communicate at distance of several meters. It is used
on shipping pallets and some drivers licenses.
 HF RFID (High Frequency RFID) is likely to be in the
passports, credit cards, books, and noncontact
payment systems.
 LF RFID (low Frequency RFID) is used for animal
tracking.
1.5.4 RFID & Sensor Networks (3)
 The Problems in Using RFID
 Multiple tags in reading rage
 Like 802.11: wait for a short random interval
 Security
 Malware
 Virus
1.5.4 RFID & sensor networks (4)
 Sensor networks spread small devices over an
area
 Multihop network: devices send sensed data to
collector via wireless hops
Problems: 24, 25
1.5.4 RFID & sensor networks (4)
 Sensor networks spread
small devices over an
area (2)
 The connections can be
wired or wireless
 (Wireless) Mesh （网状）
network
 The full mesh topology
 The partial mesh topology
 using self-healing（自愈
） algorithms
The figures from Wikipedia
（Internet of Things）物联网




以物流为中心
不再是PC计算机节点 /IP编址，新的编址方法
比Internet的价值大30倍
中国的优势
 起步早
 参与标准的制定
 物流环节完整
 相关技术




无线网络、手机移动网、卫星网
GIS、WSN、RFID
系统的集成技术
物联网安全、物联网应用
 通过互联网查资料，大家讨论IOT
1.6 Network Standardization
 Standards define what is needed for interoperability （互
操作性）
 Some of the many standards bodies
Body
Area
Examples
ITU
Telecommunications
G.992, ADSL
H.264, MPEG4
IEEE
Communications
802.3, Ethernet
802.11, WiFi
IETF
Internet
RFC 2616, HTTP/1.1
RFC 1034/1035, DNS
W3C
Web
HTML5 standard
CSS standard
IEEE 802 Standards
The 802 working groups. The important ones are marked with *.
The ones marked with  are hibernating. The one marked with †
gave up.
1.7 Metric Units
 The principal metric prefixes
1.8 The Future of Networks (1)
 Roadmap for the future of Web
Source: 邬贺铨, 《中国下一代互联网的研究和CNGI项目》, 2010.3.9
1.8 The Future of Networks (2)
 Future Internet (1)
 There are different naming
 Future Internet
 Post IP network，
 etc.
 Design methods: clean slate vs. dirty slate
 Related national projects or programs (1)
 USA
 GENI (Global Environment for Network Innovations)
 FIND (Future Internet Design)
 FIA (Future Internet Architecture)
1.8 The Future of Networks (3)
 Future Internet (2)
 Related national projects or programs (2)
 EU
 FIRE (Future Internet Research and Experimentation)
 FIA (Future Internet Assembly)
 China
 CNGI
 国家重点基础研究发展计划（973）：面向服务的未来互
联网体系结构与机制研究
 国家自然科学基金（NSFC）：后IP网络体系结构及其机
理探索，未来网络体系结构与关键技术
1.8 The Future of Networks (4)
 Future Internet (3)
 Related International Standards
 ITU-T SG13 and FGFN (Focus Group on Future
Networks)
 ISO JTC1/SC6
 IETF
 ALTO WG (Application-Layer Traffic Optimization)
 LISP WG (Location-ID Separation Protocol)
 Multimob WG (Multicast Support for Proxy Mobile IPv6)
 LEDBAT WG (Low Extra Delay Background Transport)
1.8 The Future of Networks (5)
 Software Defined Networking (SDN)
 SDN separates the control plane from the
data plane in network switches and routers
 OpenFlow is a leading SDN architecture
 Elastic（弹性） cloud architectures,
dynamic resource allocation, mobile
computing, and virtual machines need SDN
实验要求
 教材
 网络工程实训和实践应用教程
 清华大学出版社
 到学院资料室借阅
 实验地点
 计算机学院实验室
 联系人：裴斐老师
 实验时间
 统一安排，再通知
实验要求
第1章 网络基础知识
第2章 综合布线
第3章 交换路由
第4章 Windows Server 2008操作系统
第5章 Linux操作系统管理及服务器配置
第6章 协议分析
第7章 网络测量
第8章 网络管理
第9章 网络安全
第10章 网络编程
第11章 故障排除
第12章 网络系统集成与规划设计
习题
课后习题




量大
有难度
先思考，自己做一下，再看习题答案
答疑
 泛雅平台，网上答疑
 课间