Network layer is majorly focused on getting packets from the source to the destination, routing error handling and congestion control.
Before learning about design issues in the network layer, let’s learn about it’s various functions.
Maintains the address at the frame header of both source and destination and performs addressing to detect various devices in network.
This is performed by Internet Protocol. The network layer converts the packets from its upper layer.
It is the most important functionality. The network layer chooses the most relevant and best path for the data transmission from source to destination.
It works to deliver a logical connection across multiple devices.
Network layer design issues:
The network layer comes with some design issues they are described as follows:
1. Store and Forward packet switching:
The host sends the packet to the nearest router. This packet is stored there until it has fully arrived once the link is fully processed by verifying the checksum then it is forwarded to the next router till it reaches the destination. This mechanism is called “Store and Forward packet switching.”
2. Services provided to Transport Layer:
Through the network/transport layer interface, the network layer transfers it’s services to the transport layer. These services are described below.
But before providing these services to the transfer layer following goals must be kept in mind :-
- Offering services must not depend on router technology.
- The transport layer needs to be protected from the type, number and topology of the available router.
- The network addresses for the transport layer should use uniform numbering pattern also at LAN and WAN connections.
Based on the connections there are 2 types of services provided :
- Connectionless – The routing and insertion of packets into subnet is done individually. No added setup is required.
- Connection-Oriented – Subnet must offer reliable service and all the packets must be transmitted over a single route.
3. Implementation of Connectionless Service:
Packet are termed as “datagrams” and corresponding subnet as “datagram subnets”. When the message size that has to be transmitted is 4 times the size of the packet, then the network layer divides into 4 packets and transmits each packet to router via. a few protocol.Each data packet has destination address and is routed independently irrespective of the packets.
4. Implementation of Connection Oriented service:
To use a connection-oriented service, first we establishes a connection, use it and then release it. In connection-oriented services, the data packets are delivered to the receiver in the same order in which they have been sent by the sender.
It can be done in either two ways :
- Circuit Switched Connection – A dedicated physical path or a circuit is established between the communicating nodes and then data stream is transferred.
- Virtual Circuit Switched Connection – The data stream is transferred over a packet switched network, in such a way that it seems to the user that there is a dedicated path from the sender to the receiver. A virtual path is established here. While, other connections may also be using the same path.
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