1. Network & Inter-networking
Ilmin Kim

2. Who Invented Networking?
29 March 2004
CS 200 Spring 2004

3. What is a Network?
A group of three or more connected communicating entities
29 March 2004
CS 200 Spring 2004

4. Beacon Chain Networking
Thus, from some far-away beleaguered island, where all day long the men have fought a desperate battle from their city walls, the smoke goes up to heaven; but no sooner has the sun gone down than the light from the line of beacons blazes up and shoots into the sky to warn the neighboring islanders and bring them to the rescue in their ships.
Iliad, Homer, 700 BC
Chain of beacon’s signaled Agammemnon’s return (~1200BC), spread on Greek peaks over 600km.
29 March 2004
CS 200 Spring 2004

5. Pony Express April 1860 – October 1861 Missouri to California
10 days
10-15 miles per horse, ~100 miles per rider
400 horses total (not per station like Kahn’s)
29 March 2004
CS 200 Spring 2004

6. Chappe’s Semaphore Network
First Line (Paris to Lille), 1794
Mobile Semaphore Telegraph Used in the Crimean War
29 March 2004
CS 200 Spring 2004

7. Measuring Networks Latency Time from sending a bit until it arrives
seconds (or seconds per geographic distance)
Bandwidth
How much information can you transmit per time unit
bits per second
29 March 2004
CS 200 Spring 2004

8. Latency and Bandwidth Napoleon’s Network: Paris to Toulon, 475 mi
Latency: 13 minutes (1.6s per mile)
What is the delay at each signaling station, how many stations to reach destination
At this rate, it would take ~1 hour to get a bit from California to Virginia.
Bandwidth: 2 symbols per minute (98 possible symbols, so that is ~13 bits per minute
How fast can signalers make symbols
At this rate, it would take you about 9 days to get ps7.zip
29 March 2004
CS 200 Spring 2004

9. Improving Latency Less transfer points Faster travel Faster transfers
Longer distances between transfer points
Semaphores: how far can you see clearly
Telescopes can help, but curvature of Earth is hard to overcome
Use wires (electrical telegraphs, 1837)
Faster travel
Hard to beat speed of light (semaphore network)
Electrons in copper travel about 1/3rd speed of light
Faster transfers
Replace humans with machines

10. How many transfer points between Virginia and California
How many transfer points between Virginia and California? >tracert: (DOS 창) 특정 host까지 연결 경로 표시 >ping: 특정 컴퓨터의 연결확인
29 March 2004
CS 200 Spring 2004

11. > (define seconds-to-berkeley 0.070)
] tracert cs.berkeley.edu
Tracing route to cs.berkeley.edu [ ]
over a maximum of 30 hops:
1 <10 ms <10 ms <10 ms router137.cs.Virginia.EDU [ ]
2 <10 ms <10 ms <10 ms carruthers-6509a-x.misc.Virginia.EDU [ ]
3 <10 ms <10 ms <10 ms uva-internet.acc.Virginia.EDU [ ]
4 <10 ms <10 ms <10 ms
5 <10 ms <10 ms ms
6 <10 ms ms ms nycm-wash.abilene.ucaid.edu [ ]
ms ms ms clev-nycm.abilene.ucaid.edu [ ]
ms ms ms ipls-clev.abilene.ucaid.edu [ ]
ms ms ms kscy-ipls.abilene.ucaid.edu [ ]
ms ms ms dnvr-kscy.abilene.ucaid.edu [ ]
ms ms * snva-dnvr.abilene.ucaid.edu [ ]
ms ms ms
ms ms ms BERK--SUNV.POS.calren2.net [ ]
ms ms ms pos1-0.inr-000-eva.Berkeley.EDU [ ]
ms ms ms vlan199.inr-202-doecev.Berkeley.EDU [ ]
* * * Request timed out.
ms ms ms relay2.EECS.Berkeley.EDU [ ]
Trace complete.
> (define meters-to-berkeley (* )) ;; 3000 miles * 1600 meters/mi
> (define seconds-to-berkeley 0.070)
> (define speed-to-berkeley (/ meters-to-berkeley seconds-to-berkeley))
> speed-to-berkeley ;;; meters per second
> (define speed-of-light ) ;;; meters per second
> (/ speed-of-light speed-to-berkeley)
4.375
The Internet latency today is about ¼ the best physically possible!
29 March 2004
CS 200 Spring 2004

12. Improving Bandwidth Faster transmission Bigger pipes Better encoding
Train signalers to move semaphore flags faster
Use something less physically demanding to transmit
Bigger pipes
Have multiple signalers transmit every other letter at the same time
Better encoding
Figure out how to code more than 98 symbols with semaphore signal
Morse code (1840s)
29 March 2004
CS 200 Spring 2004

13. Morse Code Represent letters with series of
short and long electrical pulses
29 March 2004
CS 200 Spring 2004

14. Circuit Switching
Reserve a whole path through the network for the whole message transmission
Bourges
Paris
Lyon
Toulon
Once you start a transmission,
know you will have use of the network until it is finished. But,
wastes network resources.
Nantes
29 March 2004
CS 200 Spring 2004

15. Packet Switching Use one link at a time Bourges Lyon Paris Toulon
Interleave messages – send whenever the next link is free.
Nantes
29 March 2004
CS 200 Spring 2004

16. Circuit and Packet Switching
Telephone Network
Circuit: when you dial a number, you have a reservation on a path through the network until you hang up
The Internet
Packet: messages are broken into small packets, that find their way through the network link by link
29 March 2004
CS 200 Spring 2004

17. Basic Networking Concepts
Computer network
Set of independent computer systems connected by telecommunication links
Purpose: Sharing information and resources
Nodes, hosts, or end systems
Individual computers on a network

18. Communication Links How to send message with media
Using dial-up telephone line
A circuit is temporarily established between the caller and callee
Analog medium
Requires modem at both ends to transmit information produced by a computer
Computers generate digital information

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Figure 7.1 Two Forms of Information Representation
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20. Modulation of a Carrier to Encode Binary Information
Figure 7.2
Modulation of a Carrier to Encode Binary Information
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21. Communication Links (continued)
Dial-up phone links:
- transmission rate: 56,000 bps (56 Kbps)
Broadband links: Exceeding 256 Kbps
Wideband links: bandwidth over 1-2 Mbps (?)
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22. Communication Links (continued)
Options for broadband communications
Home use
Digital subscriber line (DSL)
Cable modem
Commercial and office environment
Ethernet
Fast Ethernet
Gigabit Ethernet
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23. Transmission Time of an Image at Different Transmission Speeds
Figure 7.3
Transmission Time of an Image at Different Transmission Speeds
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24. Communication Links (continued)
Wireless data communication
Uses radio, microwave, and infrared signals
Enables “mobile computing”
Types of wireless data communication
Wireless local access network
Wireless wide-area access network(SK, KT, LGU+)

25. Local Area Networks Local area network (LAN) = Ethernet
Connects hardware devices that are in close proximity
The owner of the devices is also the owner of the means of communications
Common wired LAN topologies
Bus
Ring
Star
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26. Invitation to Computer Science, Java Version, Third Edition
Figure 7.4
Some Common LAN Topologies
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27. Local Area Networks (continued)
Ethernet dev. by Xerox in 1973 (IEEE 802.3)
Most widely used LAN technology
Uses the bus topology
Two ways to construct an Ethernet LAN
Shared cable
Hubs: The most widely used technology
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28. Invitation to Computer Science, Java Version, Third Edition
Figure 7.5
An Ethernet LAN Implemented
Using Shared Cables
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29. internetwork
A collection of multiple networks connected together, so messages can be transmitted between nodes on different networks.
29 March 2004
CS 200 Spring 2004

30. Okay, so who invented the Internet?
29 March 2004
CS 200 Spring 2004

31. The first comm. internet
1800: Sweden and Denmark worried about Britain invading
Edelcrantz proposes link across strait separating Sweden and Denmark to connect their (signaling) telegraph networks
1801: British attack Copenhagen, network transmit message to Sweden, but they don’t help.
Denmark signs treaty with Britain, and stops communications with Sweden
29 March 2004
CS 200 Spring 2004

32. First Use of Internet
October 1969: First packets on the ARPANet from UCLA to Stanford. Starts to send "LOGIN", but it crashes on the G.
20 July 1969:
Live video (b/w) and audio transmitted from moon to Earth, and to several hundred televisions worldwide.
29 March 2004
CS 200 Spring 2004

33. Modern Concept
Packet Switching: Leonard Kleinrock (UCLA) thinks he did, Donald Davies and Paul Baran, Edelcrantz’s signalling network (1809) sort of did it
Internet Protocol: Vint Cerf, Bob Kahn
Vision, Funding: J.C.R. Licklider, Bob Taylor
Government: Al Gore (first politician to promote Internet, 1986; act to connect government networks to form “Interagency Network”)
29 March 2004
CS 200 Spring 2004

34. Government and Networking
Chappe wanted a commercial network
The use of novel methods that modify established habits, often hurts the interests of those who profit the most from the older methods. Few people, with the exception of the inventors, are truly interested in helping projects succeed while their ultimate impact is still uncertain Those in power will normally make no effort to support a new invention, unless it can help them to augment their power; and even when they do support it, their efforts are usually insufficient to allow the new ideas to be fully exploited. (Claude Chappe, 1824)
Anyone performing unauthorized transmissions of signals from one place to another, with the aid of telegraphic machines or by any other means, will be punished with an imprisonment of one month to one year, and a fine of 1,000 to 10,000 Francs.
French Law passed in 1837 made private networking illegal
29 March 2004
CS 200 Spring 2004

35. Overall Structure of the Internet
All real-world networks, including the Internet, are a mix of LANs and WANs
Example: A company or a college
One or more LANs connecting its local computers
Individual LANs interconnected into a wide-area company network
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36. Structure of a Typical Company Network
Figure 7.8(a)
Structure of a Typical Company Network
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37. Overall Structure of the Internet (continued)
Internet Service Provider (ISP – KT, SKT)
A wide-area network
Provides a pathway from a specific network to other networks, or from an individual’s computer to other networks
ISPs are hierarchical
Interconnect to each other in multiple layers to provide greater geographical coverage
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38. Structure of a Network Using an ISP
Figure 7.8(b)
Structure of a Network Using an ISP
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39. Invitation to Computer Science, Java Version, Third Edition
Figure 7.8(c)
Hierarchy of Internet Service Providers
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40. Overall Structure of the Internet (continued)
A huge interconnected “network of networks”
Includes nodes, LANs, WANs, bridges, routers, and multiple levels of ISPs
Early 2005
317 million nodes (hosts)
Hundreds of thousands of separate networks located in over 225 countries
Click will bring up the statistics from 2003
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41. Communication Protocols
A protocol
A mutually agreed upon set of rules, conventions, and agreements for the efficient and orderly exchange of information
TCP/IP
The Internet protocol hierarchy
Governs the operation of the Internet
Five layers (vs 7 layers protocols)
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42. The Five-Layer TCP/IP Internet Protocol Hierarchy
Figure 7.10
The Five-Layer TCP/IP Internet Protocol Hierarchy
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43. Physical Layer
Protocols govern the exchange of binary digits across a physical communication channel
Goal: Create a bit pipe between two network devices Details: voltage levels, wavelengths, radio frequencies Note: different specifications for different machines and different mode of communication
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44. Data Link Layer Protocols carry out
Error handling (detection and correction)
Framing - identify the start and stop of a message
Creates an error-free message pipe
Composed of two services
Layer 2a: Medium access control
Layer 2b: Logical link control
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45. Data Link Layer (continued)
Medium access control protocols
Determine how to arbitrate ownership of a shared line when multiple nodes want to send at the same time - collisions are possible.
Possible techniques: a. taking-turns protocols examples: polling and token-passing b. channel partitioning protocols examples: TDM (time-division multiplexing) FDM (frequency-division multiplexing) c. random access protocols (contention based) example: Carrier sense multiple protocol (ethernet)
CSMA
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46. Data Link Layer (continued)
Logical link control protocols
Ensure that a message traveling across a channel from source to destination arrives correctly
How to handle errors? A B
M(1)
Packet
ARQ algorithm
(automatic repeat request)
CSMA
Packet
ACK(1)
Seq number
M(2)
Packet
ERROR
M(3)
Packet
Packet
ACK(3)
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47. Network Layer (IP protocol)
Delivers a message from the site where it was created to its ultimate destination
Critical responsibilities
Create a universal addressing scheme for all network nodes
Deliver messages between any two nodes in the network (route the packets between two nodes)
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48. Network Layer (continued)
Provides a true network delivery service
Messages are delivered between any two nodes in the network, regardless of where they are located
IP (Internet Protocol) layer
Network layer in the Internet
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49. Network Layer (continued)
Router
Router
Key concepts
Host names
example: gordon.edu
IP addresses
example:
Domain name system (DNS)
(def) converts a symbolic host name to 32-bit IP address
Routing
store and forward & best path
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50. Routing in Network layer
Routing is a function that is required in all networks excepts that LANs such as Ethernet that provide the direct connection between all pairs of attached hosts.
In the large networks adaptive routing which is the best route for communication between two points and this route is identifies by periodically re- evaluation, is employed.
Assume a packet switching network shown in the next slide, the routers located at connection points are responsible for delivery of packets.

51. Routing Hosts Links or local networks A D E B C 1 2 5 4 3 6 Routers
Couloris,Dollimore and Kindberg Distributed Systems: Concepts & Design Edn. 4 , Pearson Education 2005

52. Routing
A simple algorithm for routing discussed here is “distance vector” algorithm which is the basis for link-state algorithm that is used by Internet.
In this algorithm each router has a table contains a single entry for each possible destination showing the next hope (link field in the table) that packet must take toward its destination.
Cost field in the table is simple calculation of vector distance or number of hopes for a given destination. See the next slide that shows routing tables for the previous network.
Couloris,Dollimore and Kindberg Distributed Systems: Concepts & Design Edn. 4 , Pearson Education 2005
Couloris,Dollimore and Kindberg Distributed Systems: Concepts & Design Edn. 4 , Pearson Education 2005

53. Routing Routings from A Routings from B Routings from C To Link Cost AD E
local 1 3 2 4 5
Routings from D
Routings from E To
Link
Cost A B C D E 3 6
local 1 2 4 5
Couloris,Dollimore and Kindberg Distributed Systems: Concepts & Design Edn. 4 , Pearson Education 2005

54. Routing
For a packet addressed to C, when it arrives at the router at A, the algorithm uses routing table in A and choose the row staring with C therefore forwards the packet to link labeled 1.
When the packet arrives at B same procedure is followed and link 2 will be selected
When packet arrives at C, routing table entry shows local that means packet should be delivered to a local host
The routing tables will be built up and maintained whenever faults occur in the network
Couloris,Dollimore and Kindberg Distributed Systems: Concepts & Design Edn. 4 , Pearson Education 2005

55. Transport Layer
Provides a high-quality, error-free, order- preserving, end-to-end delivery service
TCP (Transport Control Protocol)
Primary transport protocol on the Internet
Requires the source and destination programs to initially establish a connection
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56. Transport Layer Port: 23 Port: 78 Port: 80 Port: 567 Router Router
Host A:
Host B:
Key Concepts
1. Port Numbers
(def) identifies a specific application on a host
2. Well-known port numbers
3. TCP (transport control protocol)
requires a handshake and connection setup
4. UDP (user datagram protocol)
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57. Logical View of a TCP Connection
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58. Application Layer
Implements the end-user services provided by a network
There are many application protocols
HTTP (hypertext transfer protocol)
SMTP (simple mail transfer protocol)
POP3
IMAP
FTP (file transfer protocol)
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59. Some Popular Application Protocols on the Internet
Figure 7.16
Some Popular Application Protocols on the Internet
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60. Application Layer (continued)
Uniform Resource Locator (URL)
A symbolic string that identifies a Web page
Form
protocol://host address/page
The most common Web page format is hypertext information
Accessed using the HTTP protocol
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61. Network Services and Benefits
Services offered by computer networks
Electronic mail ( )
Bulletin boards
News groups
Chat rooms
Resource sharing
Physical resources
Logical resources
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62. Network Services and Benefits (continued)
Services offered by computer networks
Client-server computing
Information sharing
Information utility
Electronic commerce (e-commerce)
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63. Network Concept: tunnelling
communicate through an "alien" protocol
“Hide” in the payload(탑재장비, 운송화물)
IPv6 traffic using IPv4 protocols A B
IPv6
IPv6 encapsulated in IPv4 packets
Encapsulators
IPv4 network

64. A Brief History of the Internet and the World Wide Web: The Internet
August 1962: First proposal for building a computer network
Made by J. C. R. Licklider of MIT
ARPANET
Built by the Advanced Research Projects Agency (ARPA) in the 1960s
Grew quickly during the early 1970s
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65. The Internet (continued)
NSFNet: A national network built by the National Science Foundation (NSF)
October 24, 1995: Formal acceptance of the term Internet
Internet service providers start offering Internet access once provided by the ARPANET and NSFNet
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66. Invitation to Computer Science, Java Version, Third Edition
Figure 7.20
State of Networking in the Late 1980s
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67. The World Wide Web Development completed in May 1991
Designed and built by Tim Berners-Lee
Components
Hypertext
A collection of documents interconnected by pointers called links
URL (Uniform Resource Locator)
The worldwide identification of a Web page located on a specific host computer
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68. Invitation to Computer Science, Java Version, Third Edition
Figure 7.21
Hypertext Documents
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69. Summary of Level 3 Virtual environment Created by system software
Easy to use and easy to understand
Provides services such as
Resource management
Security
Access control
Efficient resource use
Operating systems continue to evolve
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70. Summary
Computer network: A set of independent computer systems connected by telecommunication links
Options for transmitting data on a network: Dial-up telephone lines, DSL, cable modem, Ethernet, Fast Ethernet
Types of networks: Local area network (LAN) and wide area network (WAN)
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71. Summary (continued)
The Internet is a huge interconnected "network of networks"
TCP/IP is the Internet protocol hierarchy, composed of five layers: physical, data link, network, transport, and application
The World Wide Web is an information system based on the concept of hypertext
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