Download Internet

计算机网络（Internet）
历史，现状与未来
舒炎泰 2009
计算机网络


Transportation service: move objects
 horse, train, truck, airplane ...
Communication network: move information
 bird, fire, telegraph, telephone,
 计算机网络…Internet …
A Taxonomy of Communication Networks

Communication networks can be classified based on
the way in which the nodes exchange information:
Communication
Network
Switched
Communication
Network
Broadcast
Communication
Network
广播，电视
Packet-Switched
Circuit-Switched
Communication Communication Network
Network
Datagram
电话
Virtual Circuit
Network
Network
Internet
The example

通话在 C 到 D (只经过一个本地交换机) 的连接上进行
通话在 A 到 B (经过四个交换机) 的连接上进行

思考：电话交换对于计算机是否适合？



效率/成本
应用－实时
中继线
A
用户线
(
C
(
D
(
交换机
中继线
交换机
交换机
交换机
B
(
用户线
Circuit Switching （电路交换-电话）

A node (switch) in a circuit switching network
incoming links
Node
outgoing links
Circuit Switching: Multiplexing/Demultiplexing
Time divided in frames and frames divided in
slots
 Relative slot position inside a frame determines
which conversation the data belongs to
 Needs synchronization between sender and
receiver
 In case of non-permanent conversations

Needs
to dynamic bind a slot to a conservation
How to do this?
Timing in Circuit Switching
Host 1
Host 2
Node 1
Node 2
processing delay at Node 1
propagation delay
between Host 1
and Node 1
Circuit
Establishment
propagation delay
between Host 2
and Node 1
Data
Transmission
DATA
Circuit
Termination
Packet Switching （分组/包交换） 1961
报文
1101000110101010110101011100010011010010
假定这个报文较长
不便于传输

在发送端，先把较长的报文划分成较短的、固定长度的数据
段。
Computer networks self-development
----packet switching
分组交换网以“分组”(也称 包)作为数据传输单元
依次把各分组发送到接收端（假定接收端在左边）。
分组 1
首部
数
据
分组 2
首部
数
据
分组 3
首部
数
据
Computer networks development
----packet switching

最后，在接收端把收到的数据恢复成为原来的报文。
报文
1101000110101010110101011100010011010010
数 据
数 据
数 据

这里我们假定分组在传输过程中没有出现差错，在转发时也
没有被丢弃。
Packet Switching （分组/包交换） 1961


Data are sent as formatted bit-sequences, so-called
packets
Packets have the following structure:
Header
 Header



Data
Trailer
and Trailer carry control information (e.g.,
destination address, check sum)
Each packet is passed through the network from node
to node along some path (Routing)
At each node the entire packet is received, stored
briefly, and then forwarded to the next node
(Store-and-Forward Networks)
Typically no capacity is allocated for packets
Packet Switching - Example
Router E
Router A
Router
Congested
Router C
Router D
Router B
Router F
Timing of Datagram Packet Switching
Host 1
transmission
time of Packet 1
at Host 1
Node 1
Packet 1
Host 2
Node 2
propagation
delay between
Host 1 and
Node 2
Packet 2
Packet 1
Packet 3
processing
delay of
Packet 1 at
Node 2
Packet 2
Packet 1
Packet 2
Packet 3
Packet 3
Packet Switching （分组/包交换） 1961

A node in a packet switching network
incoming links
Node
Memory
outgoing links
Packet Switching: Multiplexing/Demultiplexing



Data from any conversation can be transmitted at any
given time
How to tell them apart?
Use meta-data (header) to describe data
Datagram Packet Switching
Each packet is independently switched
 Each packet header contains destination address
No resources are pre-allocated (reserved) in advance
Example: IP networks
Model: Queuing System
Customers
Queue
Server
Queuing System

Use Queuing models to
 Describe the behavior of queuing systems
 Evaluate system performance
Response Time vs. Arrivals
Waiting vs. Utilization
0.25
W(sec)
0.2
0.15
0.1
0.05
0
0
0.2
0.4
0.6
r (%)
W 
1
 
0.8
1
1.2
Internet 历史(1)
Sep69 1st IMP in UCLA, Oct69 2nd IMP in SRI
Internet 之父-- L. Kleinrock
1999
1969
History of the Internet (2)
History of the Internet (3)

Sep69 1st IMP in UCLA
Oct69 2nd IMP in SRI

22:30 29Oct69

LOGIN from UCLA to
SRI CLA
We sent an “L” - did
you get the “L”? YEP!
We sent a “O” - did you
get the “O”? YEP!
We sent an “G” - did
you get the “G”?



Crash!
Internet 提供的服务




Shared access to computing resources
 telnet (1970’s)
Shared access to data / files
 FTP, NFS, AFS (1980’s)
Communication medium over which people interact
 email (1980’s), on-line chat / messaging (1990’s)
 audio, video (1990’s)
 replacing telephone network?
A medium for information dissemination
 USENET (1980’s)
 WWW (1990’s)
 replacing newspaper, magazine?
 audio, video (1990’s)
 replacing radio, CD, TV?
Internet Physical Infrastructure
Classification by Coverage
模型, 协议, 分层
Protocol Architecture
Don’t Need All Layers Everywhere
Protocol Data Unit - PDUs
Network Components (Examples)
Links
Interfaces
Fibers
Ethernet card
Switches/routers
Large router
Wireless card
Coaxial Cable
Telephone
switch
Growth of the Internet

Today: backbones run at 2.4/10/100 Gbps,
500 millions computers in 150 countries
Internet 在中国



中科院高能物理所
 1993年3月64Kbps
 1986.8.25 Email
TJU:1995年3月22日
2009年7月
 网民 3.4亿
 WWW站 306万
 CN域名 1296万
 国际出口带宽 748 Gbps
 连接美国、俄罗斯、法国、英国、德国、
日本、韩国、新加坡等
宽带接入速度远远落后于发达国家
趋势: 网络时代






每一件事务都是数字的: 声音, 视频, 音乐, 画
片
每一件事务都是在线的: 银行, 医疗, 航空, 天
气情况, 公路交通, …
每个人之间都是相互联系的:医生,教师,经济人,
母亲,儿子, 朋友, 敌人
实现家庭
 教育， 办公， 购物， 娱乐/网上娱乐
虚拟工作场所
 2000年，美国有五千五百万人实现远程工作
网络制造/电子商务
趋势: 网络时代

计算机集成制造系统/先进制造/信息化
CIMS (Computer Integrated Manufacturing)



1973 Dr. Joseph Harrington
目标：市场竞争 - T, Q, C, S
 时间T（即开发新产品的时间或成熟产品的上市时间）
、质量Q、成本C和服务S
核心思想
 系统的观点 -- 全局优化
 企业的各个环节，包括市场分析、产品设计、加工
制造、经营管理及售后服务的全部经营活动，是不
可以分割的整体.
 信息的观点 -- 信息集成
 企业的运行是信息采集，传递，加工处理的过程.
产品可以看作数据的物质表现.
目标-提高竞争力（CIMS-Internet）
70年代前 降低劳动成本
降低产品成本
降低产品成本 提出CIMS
70年代
提高企业整体效益
80年代
TQCS
CIMS推广应用
90年代
新产品开发，信息、知识
CIMS发展
2000年代
核心：服务/用户
范围：全球企业间/供应链
资源：信息、知识（无时空）
网络制造/
电子商务
网络制造




Internet从单纯的信息工具变成”E－时代”
的关键资源.全球经济一体化成为制造业变革
的最根本的推动力
基于Internet的虚拟制造与虚拟装配
在相互联结的网络上，建立24小时工作的协同
工作组，大大加快了设计进度、及时获得所需
要的零部件，减少库存、降低成本，提高质量
网络制造的本质特性就是产品的制造过程更加
分散化，信息的传递网络化，信息的流动伴随
着各项工作的并发进行而同时发生
电子商务




信息技术和Internet引发的商务过程的变化
利用以Internet为核心的信息技术，进行商务
活动和企业资源管理
CIMS是企业实施电子商务的基础
企业实施电子商务是CIMS发展的主要标志和主
要内容
电子商务产生背景
竞争环境改变
管理重心迁移
核心
产品竞争
服务竞争
范围
单个企业
全球多企业
资源
人、财、物
信息、知识
生产管理
集中内部资源
离散管理
供应/营销链管理
整合外部资源
集约管理
商务模式转化
传统商务
•文秘型管理
•关注后台（企业内部）
•关注业务记录（报表）
•地区性
•推销产品为中心
•（卖方市场）
电子商务
•自我服务型管理
•关注前端（客户关系）
•要求商业智能（分析）
•全球化
•客户为中心
•（买方市场）
e企业的业务体系结构
客户
市场营销
产品/服务
销售
服务/支持
产品制造
供应商
合作伙伴
网络智能
协同产品商务( CPC)
制造企业
用户
供应商
……


制造规划方案
制造规划方案
生产管理方案
生产管理方案
销售和输送方案
销售和输送方案
零部件管理方案
零部件管理方案
维护和售后服务方案
维护和售后服务方案

供应商方案
供应商方案
营销方案
营销方案
Internet/Intranet
产品开发方案
产品开发方案
用户在互联网上
参与产品的开发
、设计及修订。
在虚拟市场空间
中，顾客与生产
者及供应商一起
参与产品生命周
期中的每一项技
术及商业环节。
不受地域及时间
的限制，信息可
以快速地流动。
企业的发展趋势
业务过
程重组
IDS Sheer
业务流程
部门之间的障碍
2000年以后
电子商
务工程
IDS Sheer
企业之间的障碍
网络制造--电子商务
网络发展趋势









趋势: 融合
趋势: 泛在（Ubiquitous）
趋势: 信息爆炸
更多的网络业务流量
数据流量 > 话声流量
更快的传输介质/骨干网（Backbone）
更大的带宽（Bandwidth）
宽带无线网飞速增长(WLAN) (Wi-Fi)
Everything over IP
趋势: 融合






新闻/广告-媒体-信息提供者
 数字媒体产品
有线电视
 视频传输
电话
 声音传输
计算机
 数字媒体存储/处理
信息提供者和信息传输者的结合
电话公司, 有线公司, 娱乐事业, 和计算机公司
的结合
Trend:
趋势: 更快的传输介质

局域网：1 Gbps over 4-pair UTP-5 up to 100 m,
10Gbps being discussed
 Was

骨干网：光纤DWDM ( Dense Wavelength
Division Multiplexing)
 OC-768 = 40 Gbps over a to 65 km,
1600 Gbps - 10 Tbps
 Was

1 Mbps (1Base-5) in 1984
100 Mbps (FDDI) in 1993
无线网：54 /500 Mbps(100-2km-50km) wireless
networks, 2.5 Gbps to 5km using light
 Was
1 Mbps (IEEE 802.11) in 1998
Why Optical Networks?
DWDM optoelectricl metro network
Trend:宽带无线网飞速增长
Trend:宽带无线网(Wi-Fi)飞速增长
Trend: Wireless / Mobile
Integration of 3G and WLAN
- offer possibility of achieving anywhere, anytime,
high speed and low expense Internet access
3G
WLAN
Wide area
Local area
Low bit rate
(2M when stand
still)
High bit rate
(11M to 54M)
Data/Voice service
(QoS support)
High expense
Data service
Low expense
High mobility
Low mobility
Future Internet Research and
Experimentation
Today’s Internet
Millions of users
 Web, email, low-quality audio & video
 Interconnect personal computers and servers
 Applications adapt to underlying technology
 Today’s Internet Doesn’t
Provide reliable end-to-end performance
Encourage cooperation on new
capabilities
Allow testing of new technologies
Support development of revolutionary
applications


Internet2 Project



Develop and deploy advanced network
applications and technologies, accelerating
the creation of tomorrow’s Internet.
Goals
 Enable new generation of applications
 Re-create leading edge R&E network
capability
 Transfer capability to the global
production Internet
206 University Members, Jan. 2005
Abilene Connections :: Apr-2000
Abilene Connections: July 2006
Abilene Connections :: Apr-2000
Abilene International Peering 2006
Internet Development Spiral
Commercialization
Privatization
Today’s Internet
Research and
Development
Internet2
Partnerships

Packet-Switching vs. Circuit-Switching

Most important advantage of packet-switching
over circuit switching: ability to exploit
statistical multiplexing:
Efficient
bandwidth usage; ratio between peek and
average rate is 3:1 for audio, and 15:1 for data traffic

However, packet-switching needs to deal with
congestion:
More
complex routers
Harder to provide good network services (e.g., delay
and bandwidth guarantees)

In practice they are combined:
IP
over SONET, IP over Frame Relay
Virtual-Circuit Packet Switching
Hybrid of circuit switching and packet
switching
Data is transmitted as packets
All packets from one packet stream are sent
along a pre-established path ( = virtual
circuit)
 Guarantees in-sequence delivery of packets
 However: Packets from different virtual
circuits may be interleaved
 Example: ATM networks
MPLS?

Virtual-Circuit Packet Switching
Host C
Host D
Host A
Node 1
Node 2
Node 3
Node 5
Host B
Node 6
Node 4
Node 7
Host E
Virtual Circuit Packet Switching-Example
3.
Circuit Disconnect
1.2.Connection
Information
Establishment
Transfer
Router E
Router C
Router A
Router D
Router B
Router F
Timing of Virtual-Circuit Packet Switching
Host 1
Node 1
Host 2
Node 2
propagation delay
between Host 1
and Node 1
VC
establishment
Packet 1
Packet 2
Packet 1
Data
transfer
Packet 3
Packet 2
Packet 3
Packet 1
Packet 2
Packet 3
VC
termination
Asynchronous Transfer Mode: ATM


1990’s/00 standard for high-speed (155Mbps to
622 Mbps and higher) Broadband Integrated
Service Digital Network architecture
Goal: integrated, end-end transport of carry
voice, video, data
 meeting timing/QoS requirements of voice,
video (versus Internet best-effort model)
 “next generation” telephony: technical roots
in telephone world
 packet-switching (fixed length packets,
called “cells”) using virtual circuits
ATM reference model
How far along are we?



Standardization bodies - ATM Forum, ITU-T
We may never see end-to-end ATM (1997)
 ATM - too complex - too expansive <IP>
 Backbone: - 1995 vBNS (ATM)
- 1998 Abilene (SONET) - 2000 IP over
DWDM
Internet technology + ATM philosophy
 but ATM ideas continue to powerfully
influence design of next-generation
Internet
 ex: MPLS, admission ctl., resource
reservation, …...
Best of Both Worlds



Multiprotocol label switching (MPLS)
MPLS + IP form a middle ground that
combines the best of IP and the best of
virtual circuit switching technologies
ATM and Frame Relay cannot easily come to
the middle so IP has!
Label Encapsulation

MPLS Encapsulation is specified over
various media types. Top labels may use
existing format, lower label(s) use a new
“shim” label format.
Label Substitution

Have a friend go to B ahead of you using one of the
previous two techniques. At every road they reserve
a lane just for you. At every intersection they post a
big sign that says for a given lane which way to turn
and what new lane to take.
We are at an Impasse
ISPs are unlikely candidates for architectural
change
 We can’t test new architectures
- Despite sizable investments in testbeds
 We can’t deploy new architectures
- And things are getting worse, not better
 Yet there are pressing requirements for which
the current architecture is not well suited

GENI (Global Environment for
Network Innovations) - NSF 2005 (1)

What is GENI?
GENI is a facility concept being explored by
the US computing community
back to an NSF workshop in 2005
focus on architectural research, and
provide the experimental infrastructure
needed to support that research
focus on the research agenda (and
infrastructure needs) of the optical,
wireless, sensor network, and distributed
systems communities
GENI (Global Environment for
Network Innovations) (2)
The
goal of GENI
 Goal: a Future Internet that meets the
demands of 21st century
to increase the quality and quantity of experimental
research outcomes in networking and distributed
systems
 to accelerate the transition of these outcomes into
products and services
enhance economic competitiveness and secure
the Nation's future

Ultimately, to lead to a transition of the
Internet

FIND (Future Internet Network Design)
– NSF 2006

FIND asks two broad questions:
What are the requirements for the global network
in 15 years
 How would we re-conceive tomorrow's global
network today, if we could design it from scratch?

FIND program solicits "clean slate process"
research proposals in the broad area of
network architecture, principles, and design

FIRE (Future Internet Research and
Experimentation) – European 2007
FIRE is an experimentally-driven long-term research initiative on
Future Internet concepts, protocols and architectures
 encompassing technological, industrial and socio-economic
aspects
 acting as proof-of-concept of the newly proposed
technologies and services
 FIRE RESEARCH
Long term multidisciplinary research on future internet
paradigms
Open to fresh bottom-up ideas with no backwardscompatibility constraints
Building on the FET SAC initiative “Situated and Autonomic
Communications”
Considering at the same time technological, economic and
social/policy aspects
Build in from the outset and on all levels the right balance
between security / accountability and privacy
