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Physical Layer

Digital Transmission Analog Transmission Transmission Media Switching

Data Link Layer

Error detection and Error correction Data Link Control Multiple Access Aloha

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Network Layer - Logical Address Address Mapping Unicast Routing Protocol

Transport Layer

Process to Process Delivery User Datagram Protocol Transmission Control Protocol Stream Control Transmission Protocol Session Layer and Presentation Layer

Application Layer

Domain Name System Application Protocol E-mail Cryptography


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What is Non-Persistent CSMA

CSMA stands for "Carrier Sense Several Access". It is a commonly used Media Access Control (MAC) technology that allows several users to share a single transmission channel, such as 802.11 a wireless LAN and Internet. Since Abramson's seminal publication on ALOHA systems pioneered the computational analysis of a number of access channels, numerous academics have followed in his footsteps in exploring various MAC protocols such as CSMA. The origins of CSMA analysis may be dated back to Kleinrock et Tobagi's publication. They calculated the throughput of several CSMA protocols using a renewal theory-based technique, assuming an unlimited number of nodes and aggregate traffic as a Poisson stream. Despite the fact that the characteristic formula of throughput may be simply computed using.

What is Non-Persistent CSMA

After sensing the channel status, the node using the Non-Persistent Carrier-Sense Multiple Access (NP-CSMA) protocol takes action. If the channel in question is idle, the packet is transmitted right away; otherwise, that payload is delayed for an undetermined length of time until detecting the 2 channel again. Collisions can occur if multiple packets are sent at the same time.

Almost all subsequent research on the effectiveness of evaluation of CSMA protocols has relied on the network model described in. In for example, the attribute equation for network performance was re-derived using a transmission channel state-transition diagram. The semi-Markovian feature of the methods inis used to calculate the saturation performance for NP-CSMA. The time axes have slots and the entire network is synchronized in a stacked NP-CSMA network.

Packets may only be sent at the start of a timeslot, so every single transfer consumes one slot time. We assume inthat the computation time for sending an acknowledgement packet is minimal and that the spread delay to package transmission time ratio is a. The timeslot can then be subdivided into mini-slots of berth size a. The time axis may be thought of as a succession of alternating busy and idle times based on the channel condition.

Each node's input buffer is described as a Geo/G/1 with a Bernoulli arrival procedure that rate packets/timeslot. For contention resolutions in the NP-CSMA protocol, we investigate a broad backoff technique known as the K-Exponential Backoff algorithm. A new HOL package is sent only after an empty channel is detected, and if a collision occurs, the signal is scheduled for replay at a later time. If a backlogged HOL message has experienced i collisions, it is in phase i. The K-Exponential Backoff technique allows a HOL session in phase i to be transmitted again with probability q i for i = 1,..., K, where retransmission factor is 0 q 1 and cut-off phase is K.

What is Non-Persistent?

Non-persistent Carrier Sense Multiple Access (CSMA) is a non-aggressive form of the Carrier Sense Multiple Access (CMSA) protocol which operates on the Medium Access Control (MAC) layer. CMSA protocols allow numerous users or nodes to transmit and receive data across a shared media, which might be one cable or fiber optic linking a number of nodes, or a section of the wireless frequency.

When a transmitting station has a frame to broadcast and detects a busy channel, it waits for a random length of time without detecting the channel, and then repeats the procedure.

Algorithm of Non-persistent CSMA

In a non-persistent CMSA algorithm:

  1. When a frame is ready for transmission, the transmitting station determines if the channel being used is idle or busy.
  2. If the channel being used is idle, the frame is transmitted instantly.
  3. If the given channel is occupied, the transmitter waits over a random amount of time without checking if the connection is quiet or busy.
  4. It verifies the state of the channel again at the conclusion of the waiting period and resumes the algorithm.

Non-Persistent Connection

Non-Persistent Connections are ones in which we must make a new connection for each item in order to transmit it from source to destination. We can only send one item from a single TCP connection.

There are two varieties:

  1. Non-persistent-without-parallel connection: Each objection requires two RTTs (assuming no window restriction), one for the TCP connection and one for the HTTP image/text file.
  2. Non-persistent with concurrent connection: Non-persistent using a concurrent connection necessitates additional data transmission overhead.

Since the link opens only once there is data to be transferred, there is very little resource waste. Non-Persistent Connections are more secure since the connection is closed after transferring the data and nothing can be exchanged after that.

Non-Persistent Connection necessitates a higher CPU overhead for data delivery.

Comparing Throughputs

A network system's throughput is defined by the amount of successful transfers per frame time. The graph below compares non-persistent CMSA throughput to that of different MAC protocols.

Advantage of Non-Persistent

It has a substantially lower collision rate than 1-persistent CMSA. This is due to the fact that each station waits a random period of time before trying retransmission. The likelihood of numerous stations waiting for the same period of time is quite low. As a result, collisions between competing stations are considerably decreased.

Disadvantage of Non-Persistent

It minimizes network bandwidth utilization. This is due to the fact that the channel stays idle even while there are stations with frames to send. This happens because each station waits a random amount of time before trying retransmission. While the television network is idle, many stations may be waiting.


In conclusion, if it is an idle channel, non-persistent frames will transmit frames to that channel instantly. So, if the channel appears to be busy, it is going to wait for a random amount of time before determining whether the station is idle or busy. The radio station will not detect the channel instantly in a non-persistent fashion. The key advantage is that it minimizes the likelihood of a collision. However, the difficulty with on-persistence lies in the way it affects network efficiency.