CIS 725
Advanced Computer Networks
Lecture 1
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Email: gurdip@ksu.edu
http://www.cis.ksu.edu/~singh
Phone: (785) 532-7945
Fax: (785) 532-7353
Nichols 234C
Books
• Computer Networks (not required)
Andrew Tanenbaum
• Lecture notes
• Papers
Evaluation
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Midterm 25%
Final 30%
2-3 homeworks 15%
3 programming assignments: 30%
- SPIN: Promela modeling language
- UDP/TCP programming
Course contents
• Protocol Design
• Network protocols
• Issues in network protocol design and
implementation
• Current research topics
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high speed networks,
wireless networks
sensor networks
multimedia networks
Pre-requisites
• Undergraduate networking or OS course
or equivalent experience
Network
• A set of entities connected by
communication links
- telephone networks
- ethernet
- internet
- hardware circuits
Types of Networks
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Local Area Networks
Metropolitan Area Networks
Wide Area Networks
Wireless Networks
Home Networks
Internetworks
Local Area Networks
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Two broadcast networks
(a) Bus
(b) Ring
Fig. from Tanenbaum 03
Wide Area Networks
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Relation between hosts on LANs and the
subnet.
Fig. from Tanenbaum 03
Wide Area Networks
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A stream of packets from sender to
receiver.
Fig. from Tanenbaum 03
Wireless Networks
Home Networks
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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).
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
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.
- 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
Attack at 5am
Network Software
Protocol Hierarchies
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Layers, protocols, and interfaces.
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.
Services to Protocols
Relationship
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The relationship between a service and a
protocol.
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
Protocol Hierarchies
Problems in a network
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Naming
Routing
Congestion control
Error Handling
Flow control
Security
Quality of service
Seven Layer Model (ISO)
• Physical Layer:
- transmission of raw data over a physical
channel
- twisted pair, coaxial cables, fiber optics,
wireless
Data Link Layer
• Physical layer may lose, corrupt, reorder
and duplicate data/bits.
• Data link layer provides
- framing
- error free transmission
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
Transport Layer
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Connection establishment
Disconnection
Flow control
Sequencing
Session Layer
• Establish sessions
- a session may have several connections
• Recovery
• Presentation Layer:
- encryption
- formatting
• Application Layer:
- ftp
The TCP/IP reference model
Reference Models
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Protocols and networks in the TCP/IP
model initially.