Page 17 - CITS - Computer Software Application -TT

COMPUTER SOFTWARE APPLICATION - CITS

Logical Link Control Layer(LLC)

• LLC is responsible for transferring the packets to the Network layer of the receiver that is receiving.
• It also provides flow control, responsible for multiplexing, acknowledgement and even error-checking functions
of DDL

Media Access Control Layer(MAC)
• A MAC (Media Access Control) layer is a link between the LLC (Logical Link Control) layer and the network’s
physical layer.
• Used for transferring the packets over the network.

Some Functions of Data-Link Layer
Framing - Framing is a function of the data link layer. it is adds a header to the frame that contains a destination
address. The frame is transmitted to the destination address mentioned in the header.

Flow Control - Flow control is the main functionality of the data-link layer. This prevents a fast sender from
overwhelming a slower receiver by using techniques like sliding window protocols.
Physical Addressing - These addresses are used to identify the source and destination devices within the same
local network. The Data Link Layer assigns unique addresses.
Error Control - It checks for errors that might occur during transmission using techniques like checksums or
cyclic redundancy checks (CRC). If errors are detected, the frame can be retransmitted.

Access Control - When two or more devices are connected to the same communication channel, the MAC sub-
layer of the data link layer helps to determine which device has control over the channel at a given time.
Switch & Bridge are Data Link Layer devices
3 Network Layer

• The Network Layer deals with logical addressing, routing, and forwarding of data packets between different
networks.
• It also takes care of packet routing.

• It’s layer is responsible for routing and forwarding the packets.
• It is used to route the network traffic are known as Network layer protocols.
Some Functions of Network Layer
• Logical Addressing-A network layer adds the source and destination address to the header of the frame.
Addressing is used to identify the device over the internet. these addresses are hierarchical and provide a way
to uniquely identify devices across different networks.
• Routing-The Network Layer is responsible for determining the best path that data packets. This involves
analysing network topology, congestion, and other factors to make efficient routing decisions.
4 Transport Layer
• The main responsibility of the transport layer is to transfer the data as a whole.

• it is ensures that messages are transmitted in the order in which they are sent and there is no duplication
of data.
• It is responsible for determining the optimal path for data packets to travel from the source to the destination
across interconnected networks.
• The Internet Protocol (IP) operates at this layer.
• The transport layer is called as Heart of the OSI model.
• Protocol Use : TCP, UDP NetBIOS, PPTP.

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CITS : IT&ITES - Computer Software Application - Lesson 01-17