1. Useful Learning Techniques

2. Read Ahead Also please proof read assignments & tests.
Like in an English class
You are expected to read the lecture notes before the lecture.
This will facilitate more productive discussion during class.

3. We are going to test you on your ability to explain the material.
Explaining
We are going to test you on your ability to explain the material.
Hence, the best way of studying is to explain the material over and over again out loud to yourself, to each other, and to your stuffed bear.

4. Day Dream While going along with your day
Mathematics is not all linear thinking.
Allow the essence of the material to seep into your subconscious
Pursue ideas that percolate up and flashes of inspiration that appear.

5. Ask questions. Why is it done this way and not that way?
Be Creative
Ask questions.
Why is it done this way and not that way?

6. Guesses and Counter Examples
Guess at potential solutions a problem.
Look for input instances for which your solution gives the wrong answer.
Treat it as a game between these two players.

7. Rudich www.discretemath.com
Refinement: The best solution comes from a process of repeatedly refining and inventing alternative solutions
Rudich

8. Chapter 1
Introduction

9. Computer Network is a collection of
autonomous computers interconnected
by a single technology

10. Uses of Computer Networks
Business Applications
Home Applications
Mobile Users
Social Issues

11. Business Applications of Networks
A network with two clients and one server.

12. Business Applications of Networks (2)
The client-server model involves requests and replies.

13. Home Network Applications
Access to remote information
Person-to-person communication
Interactive entertainment
Electronic commerce

14. Home Network Applications (2)
In peer-to-peer system there are no fixed clients and servers.

15. Home Network Applications (3)
Some forms of e-commerce.

16. Combinations of wireless networks and mobile computing.
Mobile Network Users
Combinations of wireless networks and mobile computing.

17. Network Hardware Local Area Networks Metropolitan Area Networks
Wide Area Networks
Wireless Networks
Home Networks
Internetworks

18. Broadcast Networks Types of transmission technology Broadcast links
Point-to-point links

19. Classification of interconnected processors by scale.
Broadcast Networks (2)
Classification of interconnected processors by scale.

20. Local Area Networks
Two broadcast networks
(a) Bus
(b) Ring

21. Metropolitan Area Networks
A metropolitan area network based on cable TV.

22. Relation between hosts on LANs and the subnet.
Wide Area Networks
Relation between hosts on LANs and the subnet.

23. A stream of packets from sender to receiver.
Wide Area Networks (2)
A stream of packets from sender to receiver.

24. Wireless Networks Categories of wireless networks:
System interconnection
Wireless LANs
Wireless WANs

25. Wireless Networks (2)
(a) Bluetooth configuration
(b) Wireless LAN

26. Wireless Networks (3)
(a) Individual mobile computers
(b) A flying LAN

27. Home Network Categories
Computers (desktop PC, PDA, shared peripherals
Entertainment (TV, DVD, VCR, camera, stereo, MP3)
Telecomm (telephone, cell phone, intercom, fax)
Appliances (microwave, fridge, clock, furnace, airco)
Telemetry (utility meter, burglar alarm, babycam).

28. Network Software Protocol Hierarchies Design Issues for the Layers
Connection-Oriented and Connectionless Services
Service Primitives
The Relationship of Services to Protocols

29. What Goes Wrong in the Network?
Bit-level errors (electrical interference)
Packet-level errors (congestion)
Link and node failures
Messages are delayed
Messages are deliver out-of-order
The key problem is to fill in the gap between what
applications expect and what the underlying
technology provides.

30. Performance Bandwidth (throughput)
Amount of data that can be transmitted per time unit
Example: 10Mbps
Notation
KB = bytes
Mbps = bits per second
Bandwidth related to “bit width”

31. Latency (delay) Latency = Propagation + Transmit + Queue
Time it takes to send message from point A to point B
Example: 24 milliseconds (ms)
Sometimes interested in in round-trip time (RTT)
Components of latency
Latency = Propagation + Transmit + Queue
Propagation = Distance / SpeedOfLight
Transmit = Size / Bandwidth

32. Speed of light Notes 3.0 x 108 meters/second in a vacuum
2.3 x meters/second in a cable
2.0 x meters/second in a fiber
Notes
no queuing delays in direct link
bandwidth not relevant if Size = 1 bit
process-to-process latency includes software overhead
software overhead can dominate when Distance is small

33. Can Speed Grow Indefinitely?
24 ms time it takes for light wave to travel 3000 miles width of the US
Queuing and Bandwidth will improve. But Latency will stay.

34. Relative importance of bandwidth and latency
small message (e.g., 1 byte): 1ms vs 100ms dominates 1Mbps vs 100Mbps
large message (e.g., 25 MB): 1Mbps vs 100Mbps dominates 1ms vs 100ms
Latency = Delay + Size / Bandwidth
Application Needs
bandwidth requirements: burst versus average rate
jitter: variance in latency (inter-packet gap)

35. Protocols Building blocks of a network architecture
Each protocol object has two different interfaces
service interface: defines operations on this protocol
peer-to-peer interface: defines messages exchanged with peer
Term “protocol” is overloaded
specification of peer-to-peer interface
module that implements this interface

36. Network Software Protocol Hierarchies
Layers, protocols, and interfaces.

37. Protocol Hierarchies (2)
The philosopher-translator-secretary architecture.

38. Protocol Hierarchies (3)
Example information flow supporting virtual communication in layer 5.

39. Design Issues for the Layers
Addressing
Error Control
Flow Control
Multiplexing
Routing

40. Connection-Oriented and Connectionless Services
Six different types of service.

41. Service Primitives
Five service primitives for implementing a simple connection-oriented service.

42. Service Primitives (2)
Packets sent in a simple client-server interaction on a connection-oriented network.

43. Services to Protocols Relationship
The relationship between a service and a protocol.

44. Reference Models
The OSI (Open Systems Interconnection) Reference Model
The TCP/IP Reference Model
A Comparison of OSI and TCP/IP
A Critique of the OSI Model and Protocols
A Critique of the TCP/IP Reference Model

45. The OSI reference model.
Reference Models
The OSI reference model.

46. Physical layer Provides only the means of transmitting raw bits.
The shapes of the electrical connectors,
which frequencies to broadcast on
An analogy of this layer in a physical mail network would be
a specification for various kinds of paper and ink, for example.

47. Data link layer
Responds to service requests from the network layer and issues
service requests to the data link layer.
Provides the functional and procedural means to transfer data between
network entities and might provide the means to detect and possibly correct
errors that may occur in the Physical layer.
The data link provides data transfer across the physical link.
That transfer might or might not be reliable.
Responsible for node to node (hop to hop) packet delivery.
Example: Ethernet

48. Network layer
Responds to service requests from the transport layer and issues
service requests to the physical layer .
Addresses messages and translates logical addresses and names into
physical addresses. It also determines the route from the source to the
destination computer and manages traffic problems, such as switching,
routing, and controlling the congestion of data packets.
Responsible for end to end (source to destination) packet delivery

49. Transport layer
Responds to service requests from the session layer and issues
service requests to the network layer .
Provide transparent transfer of data between end users, relieving the
upper layers from any concern with providing reliable and cost-effective data transfer
Connection-Oriented
Same Order Delivery
Reliable Data
Flow Control
Byte Orientation
Ports
Example: TCP – Transmission Control Protocol.

50. Session layer
Responds to service requests from the presentation layer and issues
service requests to the transport layer .
Provides the mechanism for managing the dialogue between end-user
application processes. It provides for either full duplex or half-duplex
operation and establishes checkpointing, adjournment, termination, and
restart procedures.
Usually completely unused, but the idea is to allow information on different
streams, perhaps originating from different sources, to be properly combined.

51. Presentation layer
Responds to service requests from the application layer and issues
service requests to the session layer.
Responsible for the delivery and formatting of information to the
application layer for further processing or display .
The presentation layer is the first one where people start to care about what they
are sending at a more advanced level than just a bunch of ones and zeros.
Encryption is typically done at this level .

52. Application layer Issues requests to the presentation layer.
It interfaces directly to and performs common application services
for the application processes.
The common application layer services provide semantic conversion
between associated application processes
Example: HTTP

53. The TCP/IP reference model.
Reference Models (2)
The TCP/IP reference model.

54. Protocols and networks in the TCP/IP model initially.
Reference Models (3)
Protocols and networks in the TCP/IP model initially.

55. Comparing OSI and TCP/IP Models
Concepts central to the OSI model
Services
Interfaces
Protocols

56. A Critique of the OSI Model and Protocols
Why OSI did not take over the world
Bad timing
Bad technology
Bad implementations
Bad politics

57. The apocalypse of the two elephants.
Bad Timing
The apocalypse of the two elephants.

58. A Critique 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

59. The hybrid reference model to be used in this book.
Hybrid Model
The hybrid reference model to be used in this book.

60. Example Networks The Internet
Connection-Oriented Networks: X.25, Frame Relay, and ATM
Ethernet
Wireless LANs: 802:11

61. The ARPANET (a) Structure of the telephone system.
(b) Baran’s proposed distributed switching system.

62. The original ARPANET design.
The ARPANET (2)
The original ARPANET design.

63. The ARPANET (3)
Growth of the ARPANET (a) December (b) July 1970.
(c) March (d) April (e) September 1972.

64. NSFNET
The NSFNET backbone in 1988.

65. Internet Usage Traditional applications (1970 – 1990) E-mail News
Remote login
File transfer

66. Architecture of the Internet
Overview of the Internet.

67. ATM Virtual Circuits
A virtual circuit.

68. ATM Virtual Circuits (2)
An ATM cell.

69. The ATM Reference Model

70. The ATM Reference Model (2)
The ATM layers and sublayers and their functions.

71. Architecture of the original Ethernet.

72. Wireless LANs (a) Wireless networking with a base station.
(b) Ad hoc networking.

73. The range of a single radio may not cover the entire system.
Wireless LANs (2)
The range of a single radio may not cover the entire system.

74. Wireless LANs (3)
A multicell network.

75. Network Standardization
Who’s Who in the Telecommunications World
Who’s Who in the International Standards World
Who’s Who in the Internet Standards World

76. ITU Main sectors Classes of Members Radiocommunications
Telecommunications Standardization
Development
Classes of Members
National governments
Sector members
Associate members
Regulatory agencies

77. 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.

78. The principal metric prefixes.
Metric Units
The principal metric prefixes.