1. Computer Networks

2. A History Lesson of Networking
1969 – ARPANET, first packet switched network consist of UCLA, Stanford, UC Santa Barbara and Utah University
1971 – first program
1974 – TCP/IP
1980’s – Local Area Networks (LANs)
1984 – OSI Layer
1990’s – WWW / Internetworking
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3. Introduction Computer Network
Why Networking?
Efficiency and Productivity
Reliability
Distributed Systems
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4. Introduction Computer Network
What Applications?
Client/Server Business Applications
Electronic Messaging
Information Retrieval
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5. Network Classification by Area
Wide Area Network
Metropolitan Area Network
Local Area Network
Personal Area Network
Ad Hoc Network
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6. Introduction Computer Network
Protocols
Driving Force: need for different proprietary networking system to communicate
Protocol: set of rules for acceptable behaviour (how communication should take place in)
Specifically:
the set of rules used by communicating parties for that communication to be successful
Suite of protocols cover all required behaviour
Mostly implemented in Software
Complexity demands that protocols are ‘layered’
Introduction Computer Network

7. Advantages of Layering Protocols
Dividing complex network operation into more manageable layers
Defining the standard interface for the “plug-and-play” multi-vendor integration
Facilitate Modular Engineering
Simplifies Teaching and Learning
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8. ISO/OSI Reference Model
ISO in 1984
Open Systems Interconnect (OSI)
A design guideline for network layering
Abstract layers provide different services
Defines 7 layers of service
Each layer provides service to adjacent layers
Each layer communicates with same layer in remote machine…
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9. Introduction Computer Network
OSI Reference Model
Physical Layer
Link Layer
Network Layer
Transport Layer
Session Layer
Presentation Layer
Application Layer
Physical Layer
Link Layer
Network Layer
Transport Layer
Session Layer
Presentation Layer
Application Layer
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10. Introduction Computer Network
Layer 1 - Physical
Physical Layer:
Move bits between devices
Specifies voltage, wire speed, and pin out cables
Passes data up to data link layer (and receives from data link layer)
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11. Introduction Computer Network
Layer 2 – Data Link
Data Link Layer:
Performs framing of bits, flow and error control but not correction
Responsible for transmission of frames across the physical link
Provide access to media using MAC address
Passes data between physical and network layers
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12. Introduction Computer Network
The Institute of Electrical and Electronics Engineers (IEEE) has subdivided the data link layer into two sublayers: Logical Link Control (LLC) and Media Access Control (MAC).
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13. Introduction Computer Network
The Logical Link Control (LLC) sublayer is responsible for identifying Network Layer protocols and then encapsulating them. An LLC header tell the Data Link Layer what to do with the packet if a frame is coming. Also provide flow control and sequencing of control bits
The Media Access Control (MAC) sublayer of the data link layer manages protocol access (logical topologies) to the physical network medium. The IEEE MAC specification defines MAC addresses, which enable multiple devices to uniquely identify one another at the data link layer. IEEE dan 802.5
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14. Introduction Computer Network
Layer 3 - Network
Network Layer:
Passes data between data link and transport layers
Responsible for routing data across a network, from source to destination using network-wide addressing
Pass data between (separate) subnetworks
Hides network topology from higher layers
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15. Introduction Computer Network
Layer 4 - Transport
Transport Layer:
Passes data between network and session layers
Provides reliable end-to-end delivery of data, including flow and error control of packets
Fragmentation of large messages
Quality of Service (QoS), usually with layer 3
Last of the pure network layers
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16. Introduction Computer Network
Layer 5 - Session
Session Layer:
Passes data between presentation and transport layers
Responsible for managing network sessions (series of related data streams)
Provides synchronization and scheduling
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17. Introduction Computer Network
Layer 6 - Presentation
Presentation Layer:
Passes data between application and session layers
Provides translation services for data to ensure applications are using compatible formats
E.g. converting from ASCII to EBCDIC text representations
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18. Introduction Computer Network
Layer 7 - Application
Application Layer:
Passes data to presentation layer (and receives from presentation layer)
… to and from the user!
Communicates with remote applications
Determines the user capability within the network
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19. Introduction Computer Network
Data Encapsulation
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20. Introduction Computer Network
Data Encapsulation
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21. OSI Layer vs. TCP/IP Layer
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22. Introduction Computer Network
FTP – File Transfer Protocol
HTTP – Hypertext Transfer Protocol
WAP – Wireless Application Protocol
SMTP – Simple Mail Transfer Protocol
5-7
TCP
UDP 4 3 IP
1-2
e.g. IEEE 802.x
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23. Some Protocols in TCP/IP Suite
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24. Introduction Computer Network
Quiz
Protocols
What are they?
Why do we layer protocols?
ISO/OSI – 7 layer reference model
How does the OSI abstract services?
How does data pass between layers (local/remote)?
How does Internet stack relate to OSI?
Introduction Computer Network