GREEN UNIVERSITY OF

BANGLADESH

Final Examination Assignment

COURSE TITEL: Web Programming

COURSE CODE: 303

Submitted To Submitted By
SAFIAL ISLAM AYON Name: MD afge vtg
ID: 1810020777
Lecturer Section: 181_DB
Nuts and bolts” view
Department of CSE Department of CSE
One way is to describe the nuts and bolts of the Internet, that is, the basic hardware and

software components that make up the Internet

What is the Internet?

The Internet is a vast network that connects computers all over the world.

What’s a protocol?
A protocol is a standard set of rules that allow electronic devices to communicate with each
other…Examples  wireless networking and Internet communication …http I a protocol

What is edge.
Network Edge: Computers and other devices are connected at the edge (end) of the network.
- These computers are known as hosts or end systems,,,,,,example…. a wireless LAN

Sockets
Networking er dorja mane holo sockets……jkuno message akta process er maddome toiri holo
and ak jaiga theke r ak jai gai jbe se hoito tar ba internet er maddome jbe …tkhn take akta
dorjar maddome te hbe atak bola hoi socket.

What is Network Core

A core network is a telecommunication network's core part, which offers numerous
services to the customers who are interconnected by the access network. Its key
function is to direct telephone calls over the public-switched telephone network. ... This
term is also known as network core or backbone network.
Packet switching 
Packet switching is the transfer of small pieces of data across various networks.
More efficient than circuit switching.  Reduces lost data packets because packet
switching allows for resending of packets…  packet switching works by breaking data up
into packets and sending it into a decentralized netw.
Throughput refers to how much data can be transferred from one location to another in a
given amount of time. However, the actual data transfer speed may be limited by other
factors such as the Internet connection speed and other network traffic.
TCP service
 reliable transport between sending and receiving process
 connection-oriented: setup required between client and server processes
UDP service:
1…..unreliable data transfer between sending and receiving process
2….does not provide: reliability, flow control, congestion control, timing, throughput
guarantee, security,

Network edge: connection-oriented service

Suppose a , b k akta request pathalo….tarpor b rzi holo and akta response korlo…..akhn a wait
korte thakbe jotokhn na b response pathai.totokhn porjnto a ber 7a connected hote parbe na. r b
jodi razi hoi tkhn 2 jone conoction hote parbe.
Network edge: connectionless service
Goal: data transfer between end systems
A and b Akjon onno joner jonno opekkkha korte hbe na…a dairek b k data send kore dite parbe
….likge gmail….. ata not secure…. Se amake virus file pathaleu ami recive kortesi atai
connecting less.
 UDP - User Datagram Protocol [RFC 768]:
1….connectionless 2…unreliable data transfer

Circuit-Switched Network –
a type of network where the communications between end devices (nodes) must be set up before
they can communicate. Once set up, the “circuit” is dedicated to the two nodes it connects for the
duration of that connection. An example of a circuit-switched network is an analog telephone
network.
TDM (Time Division Multiplexing) and FDM (Frequency Division Multiplexing) are two methods
of multiplexing multiple signals into a single carrier. ... FDM divides the channel into two or more
frequency ranges that do not overlap, while TDM divides and allocates certain time periods to
each channel in an alternating manner
Access networks and physical mediaPhysical media used in communications include
twisted-pair cable, coaxial cable, and fiber-optic cable. These cables typically are used within or
underground between buildings.
We said that ordinary modems, ISDN, and ADSL use twisted-pair copper wire. And we said that
mobile access network use the radio spectrum
cable modems
jgula amra basay use kori.
Wireless networks 
Wireless networks operate using radio frequency (RF) technology, a frequency within the
electromagnetic spectrum associated with radio wave propagation
অপটিক্যাল ফাইবার (

Optical Fibre)  খুবই সূক্ষ্ম, স্বচ্ছ কাচতন্তু যার মধ্য দিয়ে আলোর প্রতিফলনের মাধ্যমে কোনো একটি প্রতিবিম্ব অথবা তথ্য এক
প্রান্ত থেকে অন্য প্রান্তে প্রেরিত হতে পারে। সহজভাবে বলা যায়, অপটিক্যাল ফাইবার হলো আলোর এক ধরনের পরিবাহক।

Coaxial cable
To get better high-frequency performance, the inner conductor may be silver-plated.
it is very suitable for home installation and average capacity data transmission network
 broadband:
Virtual-circuit Network
Sender kuta theke asce setar dike focus. Switches forward packets according to their VC
numbers A switch in a VC maintains state information.
network of networks
sutp suto koiak ta network mile jodi akta boro network toiri hoi tahole atake network of networks
bole.  Jara leaf noder dike na jara intermidiary noder dike tader network of networks
networking is connecting a company's internal network to the Internet, either by
connecting one computer to the Internet and sharing the access through the network.

Network Delays and Losses

Network delays are usually small. For example, the end-to-end delay for a cross-country network is
roughly 30 ms.

However, packets can get lost in a network. Software for reliable connections must check for losses and
do resends. If a resend is needed, the overall delay is at least doubled: the another round-trip time is added
for a resend request and response. For higher speed reliable data transfer protocols the impact can be even
greater.

This web page examines first the delay equation which breaks down network delays into easier to analyse
components. It then examines some of the causes of packet losses.

latancy dnodal = dproc + dqueue + dtrans + dprop

Four sources of packet delay

processing delay
 check bit errors
 determine output link
queueing delay
 time waiting at output link for transmission
 depends on congestion level of router

transmission delay:
 L: packet length (bits)
 R: link bandwidth (bps)
propagation delay
  length of physical link
 s: propagation speed (~2x108 m/sec)

Why layering
1.Jodi transmission ta onk long distance hoi 2. Transmission ta jdi onk complex packet er
somsoti hoi…. Transmission tar mode jdi khub important information thake ta jdi karo hate
pore amr onk khoti hoiye jbe ai soskol karoner jnnoi layering bebohar kora hoi.
 layering means to break up the sending of messages into separate components and
activities.
Internet protocol stack
 application: supporting network applications
 FTP, SMTP, HTTP
 transport: process-process data transfer
 TCP, UDP
 network: routing of datagrams from source to destination
 IP, routing protocols
 link: data transfer between neighboring network elements
 Ethernet, 802.111 (WiFi), PPP
physical: bits “on the wire”

ISO/OSI reference model

 application
 presentation
 session
 transport
 network
 link
 physical

spyware malware
kisu harmfull website ase jkhne bivinno key press korle ba dukar por tara pc ar harmfull attack
hoi

packet “sniffing
 ata hlo amn attac jkhne se sudu pc dekhte pbe pc te ki hose.

Some network apps

 e-mail web text messaging remote login
Application architectures
 client-server
 peer-to-peer (P2P)
clint server :
server akta jaigai cirojibon active thake.
server:
 always-on host
 permanent IP address
 data centers for scaling
clients:
 communicate with server
 may be intermittently connected
 may have dynamic IP addresses
 do not communicate directly with each other

peer-to-peer (P2P)
atate server bole kuno kisu nai.
In a P2P network, files are shared between the different computers.
 arbitrary end systems directly communicate
Processes communicating
process: program running within a host
within same host, two processes communicate using inter-process communication
Addressing processes
In order for a process on one host to send a message to a process on another host, the
sending process must identify the receiving process…  In Internet applications, the destination
host is specified by its IP address.
What transport service does an app need?
1.data integrity:
Amn app amra banabo na jkhne data pathate pathte data loss hoiye jai. Jder kuno data loss hbe
na.
2.timing
Kto taratri jbe…sob timing er upr nirvor na.
3. throughput 4. Security

Internet transport protocols services

Web and http.

Amara akta web page ter structure oiri kori maily htttp diye… tarpor http diye web er bivinno
icon create kori…..web e bivino droner jpg, img, video audio file add kori.
Non-Persistent Connection: It requires connection setup again and again for each object to
send. 
Persistent connection: It does not require connection setup again and again. Multiple objects
can use connection

HTTP request message: general format

Joto rokomer code ja kisu ase asob amra kori na asob browser bakend e nize kore.
1, request line (GET, POST, HEAD commands
2. header lines 3, boday
HTTP response message
1.status line(protocol ,status code ,status phrase)
2…Header lines 3…… data, e.g., requested HTML file

Cookies….jkhn new akta server a duki tkhn akta cookies show kore.browser e cookies ta save
hoiye thke …
• unique ID
• entry in backend database for ID
Web caches
Caches mane hossse proxy server jtar kaz hose clint er request handling kora.original server er
7 a involbe na hoye….clint akta kisu proxy server er kase request korlo jdi ta proxy server er
kase na thake tkhn ta proxy server original server er kase request pathabe ….then original
 servaer jdi dekhe sob thik thak ase tkhn forword kore proxy server er kase pathabe . then clint
sundor vabe dekhte pabe.

 Faster delivery of Web objects to the end user.

 Reduces bandwidth needs and cost. It benefits the user, the service provider
and the website owner.
 Reduces load on the website servers
difference between cookies and cache