2023-2024
IT Department
Shekhan Technical Institute
Duhok Polytechnic University
Network I
Network Models (OSI & TCP/IP)
Mr. Awf Abdulrahman
Week 5, 2024
The OSI (Open System Interconnection) Model :
➢ International Standards Organization (ISO) is a
multinational body dedicated to the worldwide agreement
on international standards and was established in 1947.
➢ An ISO standard that covers all aspects of network
communication is the Open System Interconnection (OSI)
model. It was first introduced in the late 1970s.
ISO is the organization. OSI is the model.
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Layered Architecture :
➢ The model consists of 7 separate but related layers, each of which
defines a segment of the process of moving information across a
network. Each layer in the model defines what services either
hardware or software or both provide.
➢ The scheme is shown below basically the architecture model
adopted by the ISO when its members created the open system
interconnection (OSI) reference model.
➢ Open system: a model that allows any two different systems to
communicate.
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OSI Model :
➢ Different layers perform different tasks, and the whole would not
function without the proper operation of each of its parts.
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OSI Model :
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Summary of OSI Layer Functions :
Application It is responsible for providing services to the user like E-mailservice.
Presentation To translate, encrypt, and compress data.
The session layer is responsible for dialog control and
Session
synchronization, to establish, manage, and terminate sessions.
Transport To provide end-to-end message delivery and error recovery.
To move packets from source to destination;
Network to provide internet working.
Network addressing.
Organize bit into frames;
Data link to provide node-to-node delivery.
Error checking.
To transmit bits over a medium; to provide mechanical and electrical
specification.
Physical
The physical layer is responsible for movements of individual bits from
one node to the next. 6
OSI Model :
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TCP/IP Model :
➢ TCP/IP: Transmission Control
Protocol (TCP) / Internetworking
Protocol (IP).
➢ TCP/IP protocol suite is the actual
Internet model in today's data
communications.
➢ The layers of the TCP/IP contain and
define protocols to do those functions
defined in OSI model.
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TCP/IP Protocols :
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TCP/IP Protocols :
➢Layer 1 and 2: (Physical Layer and Data Link Layer ) :
➢ Layer 1 and 2 have no specific protocol , Supports standard
protocols, TCP/IP based network can be a LAN or a WAN
➢ Layer 3: (Network Layer ):
➢ This layer selects path to route packets, IP is the main
protocol ,
➢ IP protocol uses four protocols: ARP, RARP, ICMP, and
IGMP
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TCP/IP Protocols :
➢ Internet Control Message Protocol (ICMP) A protocol in
the TCP/IP protocol suite that handles error and control
messages.
➢ Internet Group Management Protocol (IGMP) A protocol in
the TCP/IP protocol suite that handles multicasting.
➢ Address Resolution Protocol (ARP) In TCPIIP, a protocol
for obtaining the physical address of a node when the
Internet address is known.
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TCP/IP Protocols :
➢ Reverse Address Resolution Protocol (RARP) In TCPIIP, a
protocol for obtaining the internet address of a node when
the physical address is known.
➢ Internet Protocol (lP) The network-layer protocol in the
TCP/IP protocol suite governing connectionless
transmission across packet switching networks (network
addressing).
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TCP/IP Protocols :
➢ Layer 4 - Transport
➢ Handles communication among programs on a network.
TCP and UDP falls within this layer.
➢ User Datagram Protocol (UDP) A connectionless TCP/IP
transport layer protocol.
➢ Transmission Control Protocol (TCP) A transport protocol
in the TCP/IP protocol suite. A connection TCP/IP
transport layer protocol.
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TCP/IP Protocols :
➢ Layer 5 - Application
➢ End-user applications reside at this layer.
➢ Hyper Text Transfer Protocol (HTTP) An application
service for retrieving a web document.
➢ Simple Mail Transfer Protocol (SMTP) The TCP/IP
protocol defining electronic mail service on the Internet.
➢ Simple Network Management Protocol (SNMP) The
TCPI/IP protocol that specifies the process of management
in the Internet.
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TCP/IP Protocols :
➢ Terminal Network (TELNET) A general purpose client-
server program that allows remote login.
➢ File Transfer Protocol (FTP) In TCPIIP, an application
layer protocol that transfers files between two sites.
➢ Domain Name System (DNS) A TCP/IP application service
that converts user-friendly names to IP addresses.
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