OCI models and layers

3. QASIM ALI 22091556-017
SOHAIL AHMED 22091556-012
GHULLAM
MUSTAFA
22091556-022
GROUP PRESENTATION :
PRESENTED BY:

4.  Application layeer:
The application layer sits at Layer 7, the top of the Open
Systems Interconnection (OSI) communications model. It
ensures an application can effectively communicate with
other applications on different computer systems and
networks.
The application layer is not an application. Instead, it is a
component within an application that controls the
communication method to other devices. It is an abstraction
layer service that masks the rest of the application from the
transmission process.

5.  Function of Application Layer:
The application layer handles the following functions:
• ensures that the receiving device is identified, reachable
and ready to accept data;
• when appropriate, enables authentication between devices
for an extra layer of network security;
• ensures agreement at both ends on error recovery
procedures, data integrity and privacy;
• determines protocol and data syntax rules at the application
level; and
• presents the data on the receiving end to the user
application.

6.  DNS:
• DNS stands for Domain Name System.
• DNS is a directory service that provides a mapping between
the name of a host on the network and its numerical address.
• DNS is required for the functioning of the internet.
• Each node in a tree has a domain name, and a full domain
name is a sequence of symbols specified by dots.
• DNS is a service that translates the domain name into IP
addresses.

7. DNS is a TCP/IP protocol used on different platforms. The domain name space
is divided into three different sections: generic domains, country domains, and
inverse domain.
Computer Network DNS

8.  Country Domain
The format of country domain is same as a generic domain, but it uses two-
character country abbreviations (e.g., us for the United States) in place of
three character organizational abbreviations.
 Inverse Domain
The inverse domain is used for mapping an address to a name. When the
server has received a request from the client, and the server contains the files
of only authorized clients. To determine whether the client is on the authorized
list or not, it sends a query to the DNS server and ask for mapping an address
to the name.
 Generic Domains
It defines the registered hosts according to their generic behavior.Each node in
a tree defines the domain name, which is an index to the DNS database.It
uses three-character labels, and these labels describe the organization type.

9.  Electronic Mail:
Electronic Mail (e-mail) is one of most widely used services of Internet. This
service allows an Internet user to send a message in formatted manner (mail) to
the other Internet user in any part of world. Message in mail not only contain
text, but it also contains images, audio and videos data. The person who is
sending mail is called sender and person who receives mail is called recipient.
The basic components of an email system are :
1.User Agent (UA) : The UA is normally a program which is used to send
and receive mail. Sometimes, it is called as mail reader. It accepts variety of
commands for composing, receiving and replying to messages as well as for
manipulation of the mailboxes.
2.Message Transfer Agent (MTA) : MTA is actually responsible for
transfer of mail from one system to another. To send a mail, a system must have
client MTA and system MTA. It transfer mail to mailboxes of recipients if they are
connected in the same machine. The delivery from one MTA to another MTA is
done by Simple Mail Transfer Protocol.
.

10. 3.Mailbox : It is a file on local hard drive to collect mails. Delivered mails
are present in this file. The user can read it delete it according to his/her
requirement. To use e-mail system each user must have a mailbox . Access to
mailbox is only to owner of mailbox.
4.Spool file : This file contains mails that are to be sent. User agent
appends outgoing mails in this file using SMTP. MTA extracts pending mail
from spool file for their delivery. E-mail allows one name, an alias, to
represent several different e-mail addresses. It is known as mailing list.

11.  File transfer protocol :
File transfer protocol (FTP) is an Internet tool provided by TCP/IP. The first
feature of FTP is developed by Abhay Bhushan in 1971. It helps to transfer files
from one computer to another by providing access to directories or folders on
remote computers and allows software, data, text file to be transferred between
different kinds of computers. The end-user in the connection is known as
localhost and the server which provides data is known as the remote host.
Type of FTP Connections
1) Active FTP connection:
In an Active FTP connection, the client establishes the command channel and
the server establishes the data channel. When the client requests the data over
the connection the server initiates the transfer of the data to the client. It is not
the default connection because it may cause problems if there is a firewall in
between the client and the server.

12. 2) Passive FTP connection:
In a Passive FTP connection, the client establishes both the data channel as
well as the command channel. When the client requests the data over the
connection, the server sends a random port number to the client, as soon as
the client receives this port number it establishes the data channel. It is the
default connection, as it works better even if the client is protected by the
firewall.

13.  Network security issues :
Network security issues can include threats like unauthorized access, data
interception, and service disruptions. Common types include:
1.Unauthorized Access: Intruders gaining unauthorized entry to networks,
often through weak passwords or vulnerabilities.
2.Phishing: Deceptive tactics, often via email, to trick users into revealing
sensitive information like passwords.
3.Denial of Service (DoS) Attacks: Overwhelming a network or system to
make it unavailable to users, disrupting services.
4.Man-in-the-Middle Attacks: Interception of communication between two
parties, allowing attackers to eavesdrop or manipulate data.
5.Insider Threats: Security risks from within an organization, where employees
may intentionally or unintentionally compromise network security.
6.Weak Encryption: Inadequate encryption methods make it easier for
attackers to decipher sensitive information.

14.  Overview of Cryptography and Security in Internet:
In present day scenario security of the system is the sole priority of any
organisation. The main aim of any organisation is to protect their data from
attackers. In cryptography, attacks are of two types such as Passive attacks
and Active attacks. Passive attacks are those that retrieve information from the
system without affecting the system resources while active attacks are those
that retrieve system information and make changes to the system resources
and their operations.
The Security can be classified as follows:
1.Confidentiality:
The degree of confidentiality determines the secrecy of the information. The
principle specifies that only the sender and receiver will be able to access the
information shared between them. Confidentiality compromises if an
unauthorized person is able to access a message.
For example, let us consider sender A wants to share some confidential
information with receiver B and the information gets intercepted by the attacker
C. Now the confidential information is in the hands of an intruder C.

15. 2.Authentication:
Authentication is the mechanism to identify the user or system or the entity. It
ensures the identity of the person trying to access the information. The
authentication is mostly secured by using username and password.
3.Integrity:
Integrity gives the assurance that the information received is exact and
accurate. If the content of the message is changed after the sender sends it
but before reaching the intended receiver, then it is said that the integrity of the
message is lost.
4. Non-Repudiation:
Non-repudiation is a mechanism that prevents the denial of the message
content sent through a network. In some cases the sender sends the message
and later denies it. But the non-repudiation does not allow the sender to refuse
the receiver.

16. 5. Access control:
The principle of access control is determined by role management and rule
management. Role management determines who should access the data while
rule management determines up to what extent one can access the data. The
information displayed is dependent on the person who is accessing it
6. Availability:
The principle of availability states that the resources will be available to
authorize party at all times. Information will not be useful if it is not
available to be accessed. Systems should have sufficient availability of
information to satisfy the user request.