1. Advanced Computer Networks Lecture 1
CIS 725
Advanced Computer Networks
Lecture 1

2.
Phone: (785)
Fax: (785)
Nichols 234C

3. Books Computer Networks (not required) Andrew Tanenbaum Lecture notes
Papers

4. Evaluation Midterm 25% Final 30% 2-3 homeworks 15%
3 programming assignments: 30%
- SPIN: Promela modeling language
- UDP/TCP programming

5. Course contents Protocol Design Network protocols
Issues in network protocol design and implementation
Current research topics
high speed networks,
wireless networks
sensor networks
multimedia networks

6. Pre-requisites Undergraduate networking or OS course
or equivalent experience

7. Network A set of entities connected by communication links
- telephone networks
- ethernet
- internet
- hardware circuits

8. Types of Networks Local Area Networks Metropolitan Area Networks
Wide Area Networks
Wireless Networks
Home Networks
Internetworks

9. Local Area Networks Two broadcast networks (a) Bus (b) Ring
Fig. from Tanenbaum 03

10. Wide Area Networks Relation between hosts on LANs and the subnet.
Fig. from Tanenbaum 03

11. Wide Area Networks A stream of packets from sender to receiver.
Fig. from Tanenbaum 03

12. Wireless Networks

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

14. Protocol A set of rules for communicating - who should speak when
- what is the language for communication
What are the common problems
- Correctness: deadlocks, livelocks,…
- Efficiency
Specification languages

15. Clayton Tunnel in England (1841) - Best protected railway section
Signalman:
After allowing a train to enter, send “Train in tunnel”
After train leaves the tunnel, send “Tunnel is free”
“Has the train left the tunnel?”
“Train in tunnel”
“Has the train left the tunnel”
“Tunnel is free”
If semaphore failed to turn to red, signalmen is warned by a bell and could then use red and white flags.

16. Has the train left the tunnel Tunnel is clear
First train passes A, and it fails to set the signal to red;
Signalman is warned and he send “Train in tunnel”
Signalman gets the red flag to stop the next train;
Second train is too fast, and passes the green signal; But driver catches a glimpse of the red flag
Signalman is able to stop the third train
Signalman A sends another “Train in Tunnel” message
Signalman A sends “Has the train left the tunnel”
B has no way of knowing what is going on. B sees the train coming out and sends “tunnel is clear”
A now allows third train to enter
The driver of the second train had seen the red flag; he stops in the middle;
To play it safe, he decided to back out;
Collision: 21 people died and 176 injured.
Signal, Red flat
Train in tunnel,
Has the train left the tunnel
Tunnel is clear

17. Attack at 5am

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

19. Layered Network Architecture
Each layer takes care of some concerns
Number of layers may vary in different networks
Each layer provides an interface to the upper layer with more functionality added.

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

21. Layering Example:
Letter in envelope
Address on outside
FedX guy adds addressing information, barcode.
Local office drives to airport and delivers to hub.
Sent via airplane to nearest city.
Delivered to right office
Delivered to right person

22. Protocol Hierarchies

23. Problems in a network Naming Routing Congestion control Error Handling
Flow control
Security
Quality of service

24. Seven Layer Model (ISO)
Physical Layer:
- transmission of raw data over a physical
channel
- twisted pair, coaxial cables, fiber optics,
wireless

25. Data Link Layer
Physical layer may lose, corrupt, reorder and duplicate data/bits.
Data link layer provides
- framing
- error free transmission

26. Network Layer
Provides communication between any pair of nodes in the network;
Provides an illusion that everyone is directly connected to everyone else
Routing
Congestion control

27. Transport Layer Connection establishment Disconnection Flow control
Sequencing

28. Session Layer Establish sessions
- a session may have several connections
Recovery

29. Presentation Layer:
- encryption
- formatting
Application Layer:
- ftp

30. The TCP/IP reference model

31. Reference Models
Protocols and networks in the TCP/IP model initially.