OSI Reference Model (Open System Interconnection)

OSI Layer

OSI Model (Open Systems Interconnection) is model or reference main architectural for the network that describe how data and information network in communicate from a computer application to another application computer through a transmission media. OSI is not hardware or software but guidelines for vendor so it devices can run on the network.

Benefit
• Make the equipment of the different vendor can cooperate each others.
• Make standardization that can it use by vendor for reduce complexity of the
design.
• Standardization interfaces.
• Cooperation and communication with the different technology.

1. Physical Layer
Defines the transmission media, such as plugs, wire, and electrical signal that connect the sender and reciever node in the network.
2. Data Link Layer
Responsible for providing access to the network and transmitting the physical blog of tha data from one node to another.
3. Network Layer
Responsible for Routing, switcing and controlling the flow of data between nodes.
4. Transport Layer
convert messages into segment or breakes large segment into smaller segment that can be handle by lower layer.
5. Session Layer
Establishes, manage, and syncronize the comunication between to nodes.
6. Presentation Layer
Responsible for encoding and decoding data in a muttually agreeable format.
7. Application Layer
Provides the interface between the end user and the network.


Function of Layer physic (Layer 1)
• Carry forward bit between devices
• Direct communication with kind of transmission media
• Determine electric needed, mechanical, procedural and fuctionalizations maintain
and deactivate physic connection between systems.
• The specification such as voltage, wire, speed, pin at cable for example
EIA/TIA-232, V.35
Technology that is used in this layer for example: Hub and Repeater

Function of data link Layer (Layer 2)
• Sending data between nodes such as frame
• Error detection and error handling
• Add header that consist of source and destination address (like information
control)
This layer consists of:
Media Access Control (MAC) that Function to send data between nodes
Logical Link Control (LLC) that function to synchronize frame, flow control and handling error.
Technology that is used in this layer for example Bridge and switch

Function of Network Layer (Layer 3)
In this layer, will determine efficiency traffic that pass through mentioned package in the network
Technology that is used in this layer is Router
Ways of working a Router:
• Packages accepted by router interface
• Router will check destination IP Address and then router check destination network address in routing table that it have, if the not found in the entry of routing table so the data will be dropped. If the networks address it found so the router interface will slide over data and send to the local network.

Function of Transport Layer (Layer 4)
• Perform segmentation and unify return data segmentation (reassembling)
• Responsible to prepare multiplexing mechanism.
• Multiplexing is technique for sending and receiving some kind of the different
data at the same time through a network media. Demultiplexing convey package
segment that has accepted to application process that run in host mentioned.
• Transport layer have connectionless and connection-oriented character
In the TCP/IP protocol we know that this protocol have connection-oriented character.

Three phase in make initial setup in TCP/IP protocol (Three Way Handshake):
1. Establish connection: making connection before perform transaction. Process:
client send SYN data to server, then server send SYN + ACK to client, after that
the client send ACK.
2. Data transfer: after connection has made, then can do transaction, data transfer
or another.
3. Terminate connection: break or close connection after perform transaction.

Function of Session Layer (Layer 5)
In this layer establishes, manage, and synchronize the communication between to nodes.

Function of Presentation Layer (Layer 6)
In this layer determine form of the data that would be used in perform communication and encryption process.

Function of Application Layer (Layer 7)
In this layer occurs interaction with user. Such as software application for computer network can be applied.