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EEE 448

Computer Networks with

Network Programming

Lecture #1

Dept of Electrical and Electronics Engineering

Çukurova University

Course Objectives • Become familiar with the mechanisms and protocols for

reliable data communication via a computer network

• Be able to evaluate the performance of various network

technologies and protocols

• Think as an engineer: What technologies should be

employed to build a network with particular

specifications?

• Develop a fundamental understanding of the network

design principles and performance metrics

• Develop C Sharp interest in the area of Computer

Networks

Topics to be covered

• Network architectures, performance metrics, layering

• Medium access control

• Internetworking, routing

• End-to-end protocols, flow control

• Congestion control and resource allocation

• Network security

• Applications

Course Materials

• Textbook “Computer Networks: A Systems Approach”

L. Peterson, and B. Davie, 5th edition.

• Additional References “Data Networks”D. Bertsekas, and R. Gallager, 2nd edition

“Computer Networks”, S. Tanenbaum and D. Wetherall, 5th edition,

• Course Website :

eembdersler.wordpress.com Lectures, homework, useful links,

Supplementary material, announcements

Where to find me

• My Office:

• EEE bldg: Room 305

• Office Hours by appointment

• My email: turgayibrikci@hotmail.com

When the class

• Thursdays

– EEE bld Computer Lab: Room 223

– 13:15 – 16:00 AM

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Class Expectations

• Class participation – Your input is needed for good discussion

• Keep up with reading material

• Present your presentation clean and understandable

• Submit clean, organized, concise and on time your project (back

of a flyer is not ok!)

• Identify potential project partner early (in one week, if possible)

• Brush up prior knowledge (Probability theory, C# Programming)

• Follow academic integrity code (Remember EEE117)

Presentation: At least a 45 mins-presentation (How to use the time, to present the

details, to answer the questions will be graded)

Midterm and Final Exam: will be setup by the department- Closed books and materials

Grading Scheme

Assignment Points

Presentation 75%(30%) 40% of

Midterm 25%(10%) 40% of

Project 85%(50%) 60% of

Final Exam 15%(10%) 60% of

If you attend all 10%

Total 110% 100

Data Communications

•The term telecommunication means communication

at a distance.

•The word data refers to information presented in

whatever form is agreed upon by the parties creating

and using the data.

•Data communications are the exchange of data

between two devices via some form of transmission

medium such as a wire cable.

Characteristics that define effectiveness of data

communications

• Delivery

• Accuracy

• Timeliness

• Jitter

A data communications system must transmit data to the

correct destination in an accurate and timely manner.

Components of Data Communication System

• Message is the information (data) to be communicated

(text, numbers, images, audio, and video).

• Sender is the device that sends the data message

(computer, mobile phone, video camera and so on).

• Receiver is the device that receives the message.

• Transmission medium is the physical path by which a

message travels from sender to receiver (twisted-pare,

coaxial, fiber-optic cables and radio waves).

• Protocol is an agreement between the communicating

devices on how communication is to proceed.

Five components of data communication

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Data flow modes

• Simplex as one-way street. Only one of the two

devices on a link can transmit; the other can only

transmit.

• Half-duplex, each station can both transmit, but

not at the same time.

• Full-duplex (or duplex), both stations can

transmit and receive simultaneously.

Data flow modes

Networks

• Computer Network is a collection of devices

(nodes) interconnected by a single technology

(transmission medium link).

• Node can be a computer, printer, or any other

device capable of sending and/or receiving data

generated by other nodes on the network.

• Interconnected computers are two or more

computers that able to exchange information.

Computer network example

Networks

• Internet is the network of networks (connection of

two or more networks)

• Intranet is a private business network.

• Most networks use distributed processing, in

which a task is divided among multiple computers.

• Distributed System is a software system built on top

of a network.

• World Wide Web is a distributed system that runs on

top of the Internet.

Networks Internet

• An inter-net: a network of networks.

– Networks are connected using routers that support

communication in a hierarchical fashion

– Often need other special devices at the boundaries for

security, accounting, ..

– IANNA (Internet Assigned Numbers Authority)

– ICANN (Internet Corporation for Assigned Names and Numbers) controls

all from US

• ODTU for Turkey

• The Internet: the interconnected set of networks of the

Internet Service Providers (ISPs)

– About 50,000+ different networks make up the Internet

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TCP/ IP is a protocol suite in the Internet.

The main Internet applications are:

E-mail, News, Remote Login, File transfer, World Wide

Web (WWW)

Internet

The Internet has revolutionized many aspects of our

daily lives. It has affected the way we do business as well as

the way we spend our leisure time.

The Internet is a communication system that has brought a

wealth of information to our fingertips and organized it for

our use.

History of Internet:

Beginning in 1969. It was called ARPANET.

Hierarchical organization of the Internet

Internet

- The Internet today is mostly run by private companies, not the

government (Some governments still controls internet connection with

other).

- The national Internet service providers are backbone networks

created and maintained by specialized companies.

- These backbone networks are connected by complex switching

stations (normally run by a third party) called network access

points (NAPs).

- Local ISPs can be connected to a regional or national

service provider.

- Most end users are connected to the local ISPs.

Internet Challenges of the Internet

• Heterogeneity

– Address formats

– Performance – bandwidth/latency

– Packet size

– Loss rate/pattern/handling

– Routing

– Diverse network technologies satellite links,

cellular links, carrier pigeons

Challenges of the Internet

• Scale

– 21,220,000,000s of hosts( that is why IPv6)

– 72,400,000 (2010)

– 18,000+ administrative domains,

– Thousands of applications

• Adversarial environment

• Oh, and let’s make it easy to use…

• How to translate between various network technologies?

Naming

What’s the IP address for www.cu.edu.tr?

It is 193.140.54.10

Translates human readable names to logical endpoints

Local DNS Server Computer 1

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Routing

R

R

R

R R H

H

H

H

R

R H

R

Routers send

packet towards

destination

H: Hosts

R: Routers

Networks Criteria

Performance can be measured in many ways, including: Transit time (time required for a message to travel from one device to

another);

Response time (elapsed time between inquiry and response).

Performance is often evaluated by two networking metrics:

Throughput and delay : To enhance performance we need more throughput and less delay.

Reliability is measured by :

1) accuracy of delivery;

2)frequency of failure;

3) time it takes a link recover from failure.

Security includes: protecting data from unauthorized access;

protecting data from damage;

development recovery policies and procedures.

Business Applications

- Resource Sharing (printers, scanners, storage

devices, and sharing information, (client-server model))

- Communication Medium (E-mail)

- Being able to place orders in real time (Purchase)

- E-Commerce, M-Commerce

Benefits of Computer Networks I Business Applications of Networks

A network with two clients and one server.

Home Network Applications

Access to remote information (e.g. Google)

Person to person communication (chat)

Using social networks (e.g. Facebook)

Interactive entertainment (Games)

E-commerce, M-Commerce (web shopping)

Benefits of Computer Networks II Network attributes: 1 - Types of connection

• Point-to-point

• Multipoint (or multidrop, e.g. broadcasting networks)

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Network attributes: 2 –Topology

The topology of the network is the geometric

representation of the relationship of all the links

and nodes to each other.

Network attributes: 3 - Categories of networks

The most common classification of networks is based on its

physical size (scale).

- Every device in the home will be capable of

communicating with every other device, and all of

them will be accessible over the Internet.

- Examples

1. Computers (PC, Notebook, PDA)

2. Entertainment (TV, DVD, Camera...)

3. Telecommunications (telephone, intercom...)

4. Appliances (microwave, refrigerator, lights…)

5. Telemetry (smoke alarm, thermostat, babycam…)

Home Networks

LAN is a network within a single building or campus

of up to a few kilometres in size.

LANs share the following characteristics:

- their transmission media

- their size (restricted small size)

- their topology (Bus, Ring, Star)

- their setting up cost is low

- data transfer rate is high (10Mbps, 100Mbps,

10Gbps)

Local Area Network (LAN)

LAN example

A fully connected mesh topology (five devices)

We need n(n-1)/2 duplex-mode point-to-point links to connect n devices

LAN topologies: Mesh (1)

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LAN topologies: Mesh (2)

Advantages of mesh topology:

•Eliminating traffic problem (each link is dedicated to pair of devices);

•Robustness (break in one line does not lead to break of all network);

•Privacy and security;

•Fault identification and isolation is easy.

Disadvantages of mesh topology:

•Large amount of cabling and I/O ports are required;

•Wiring can be greater than available space;

•It is expensive.

Mesh mainly is used to connect servers of a hybrid topology

network that can include several other topologies.

LAN topologies: Star (1)

Star topology uses point-to-point connections (station-hub).

LAN topologies: Star (2)

In a Star topology, each station is directly connected to

a central controller – hub.

The hub acts as exchange: device sends data to hub,

which then relays the data to other device.

Advantages of star topology:

•Less expensive than mesh;

•Less cabling;

•Easy maintenance.

Disadvantages of star topology:

•One single point of failure – hub.

An isolated LAN connecting 4 computers and one printer to a hub in a

closet

LAN topologies: Star (3)

LAN topologies: Bus (1)

Bus topology is multipoint. One large cable acts as a

backbone to link all devices in a network.

LAN topologies: Bus (2)

In a bus topology, all stations are attached to a liner

transmission medium (bus) through appropriate hardware

interface (tap).

Advantages of bus topology:

•easy to install;

•efficient use of wiring;

Disadvantages of bus topology:

•One single point of failure – backbone cable.

•Difficult maintenance.

IEEE 802.3 (Ethernet) is an example of bus topology.

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LAN topologies: Ring (1)

In a Ring topology, each station on the network is connected to two

other stations, forming a loop or ring.

It uses token (signal circulating in a ring) to control transmission.

Advantages of ring topology:

• To add or delete a device requires changing only two connections.

• Fault isolation is simplified

• No conflict in the transmission of data.

Disadvantages of ring topology:

• if one connection fails, the rest of the network will fail.

• To avoid this a dual ring could be used.

IEEE 802.5 ( IBM Token Ring) & FDDI (Fiber Distributed Data Interface)

are examples.

LAN topologies: Ring (2)

LAN topologies: Hybrid-Tree (1)

A hybrid topology: a star backbone with three bus networks

LAN topologies: Hybrid-Tree (2)

Network topology

• Advantages and Disadvantages of Network Topologies

Topology Advantages Disadvantages

Bus Cheap. Easy to install.

Difficult to reconfigure.

Break in bus disables entire network.

Star Cheap. Easy to install.

Easy to reconfigure.

Fault tolerant.

More expensive than bus.

Ring Efficient. Easy to install.

Reconfiguration difficult.

Very expensive.

Mesh Simplest. Most fault

tolerant.

Reconfiguration extremely difficult.

Extremely expensive.

Very complex.

Physical Structures of Nets

Physical Topology Common Cable Common Protocol

Linear Bus

Twisted Pair

Coaxial

Fiber

Ethernet

Star Twisted Pair

Fiber Ethernet

Tree

Twisted Pair

Coaxial

Fiber

Ethernet

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MAN is a network with a size between a LAN

and a WAN.

–A MAN spans the distance of a typical

metropolitan city.

–The cost of installation and operation is higher.

–MANs use high-speed connections such as fiber

optics to achieve higher speeds.

Examples of a MAN:

1) part of the telephone company network that can

provide a high-speed DSL line to the customer;

2) cable TV network.

Metropolitan Area Network (MAN) (1)

MAN based on cable TV

Metropolitan Area Network (MAN) (2)

Metropolitan area network

Metropolitan Area Network (MAN) (3)

Relation between hosts on LANs and the subnet.

Wide Area Network (WAN) (1)

The main differences between WAN and LAN are:

- LAN is fully controlled by the owner whilst the WAN needs

the involvement of another authority like Telephone Company.

- The transfer rate of LAN is higher than the transfer rate of

WAN.

– WAN network spans a large geographical area, it

contains a collection of hosts that are connected by

a communication subnet.

– The Internet is a good example of a WAN.

– Host is a machine that is used to run user (i.e.,

application) program and is owned by the

customers.

– Subnet consists of transmission lines and switching

elements, and its job is to carry messages from host

to host.

Wide Area Network (WAN) (2)

Wide area network

Wide Area Network (WAN) (3)

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• A stream of packets from sender to receiver.

Wide Area Network (WAN) (4) Wide Area Network (WAN) (5)

- Users have a dream to connect their

notebooks to the network without having to be

plugged into a telephone wall socket.

- To achieve a true mobility there is a need to

use a radio (or infrared) signals for communication.

Three main categories:

1. System interconnection

2. Wireless LANs

3. Wireless WANs

Wireless Networks (1)

(a) Bluetooth configuration

(b) Wireless LAN

Wireless Networks (2)

- System interconnection, it is about

interconnecting the components of a computer

using a short-range radio that uses the master-

slave paradigm.

Example:

- Bluetooth is a short-range wireless network

that allows digital components to connect to a

computer by merely being brought within range.

Wireless Networks (3)

- Wireless LAN, it is a system where every

computer has a radio modem and antenna with

which it can communicate with other systems.

- Wireless LANs are used in small offices,

homes, older office building , conference rooms

and other places.

- IEEE 802.11 (WiFi) is a standard for wireless

LANs.

Wireless Networks (4)

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Wireless LAN

Wireless Networks (5)

- Wireless WAN, it is similar to wireless LAN

system, but with lower bandwidth and is used in a

wide area systems.

- Three generations of Wireless WAN :

1. was analog and for voice only

2. was digital and for voice only

3. is digital and for both voice and data

- IEEE 802.16 (WiMAX) is a standard for wireless

WANs.

Wireless Networks (6)

The Internet (4) Networking Standards (1)

We define two widely used terms: protocols and standards.

First, we define protocol, which is synonymous with rule. Then

we discuss standards, which are agreed-upon rules.

A protocol is a set of rules that governs data communication;

the key elements of a protocol are syntax, semantics, and

timing.

- The term syntax refers to the structure or format of the data,

meaning the order in which they are presented.

- The word semantics refers to the meaning of each section

of bits. How is a particular pattern to be interpreted, and what

action is to be taken based on that interpretation?

- The term timing refers to two characteristics: when data

should be sent and how fast they can be sent.

Networking Standards (2)

Advantages of standards

• A standard assures that there will be a large market for

a particular piece of equipment or software.

• A standard allows products from multiple vendors to

communicate.

Disadvantages of standards

• A standard tends to freeze the technology.

• There are multiple standards for the same thing.

Standards are necessary to ensure that products from

different manufacturers can work together as expected.

Networking Standards (3)

Standards are developed through the cooperation of standards creation

committees, forums, and government regulatory agencies.

The ISO, ITU-T, ANSI, IEEE, and IETF are some of the organizations involved

in standards creation.

ISO - International Organization for Standardization

ITU-T - International Telecommunication Union-Telecommunication Standards

Sector

ANSI - American National Standards Institute

IEEE - Institute of Electrical and Electronics Engineers

IETF - Internet Engineering Task Force

- Forums are special-interest groups that quickly evaluate and standardize

new technologies.

- A Request for Comment (RFC) is an idea or concept that is a originator to

an Internet standard.

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The 802 working groups. The important ones are marked with

*. The ones marked with are hibernating. The one marked

with † gave up.

Networking Standards (4) Summary

• A network consists of two or more entities

sharing resources and information.

• A computer network consists of two or

more computers that are connected and

are able to communicate.

Summary

• The basic purpose of networks is to enable

effective communication, share resources,

and facilitate centralized management of

data.

• Networks can be classified according to

their geographical boundaries or their

component roles.