Carrier Sense Multiple Access (CSMA) – Part 1

Computer Networks: Carrier Sense Multiple Access (CSMA) in Computer Networks
Topics Discussed:
1) Types of Multiple Access Protocols.
2) Carrier Sense Multiple Access (CSMA).
3) Types of CSMA.
4) Behavior of 1-Persistent, Non-Persistent, and P-Persistent CSMA.

--Music--
Axol x Alex Skrindo - You [NCS Release]

--Credits--
Book name: Data Communication and Networking
Author: Behrouz A. Forouzan
Edition: Fourth Edition

--Web Reference--

#ComputerNetworksByNeso #ComputerNetwork #CSMA

[abhirammanthena]

Hi Neso academy, just want to know how many of your viewers are from India? Great work!

[hamza]

You are teaching very well because you are telling problem statement and teaching in Laman
language

[yugendhiran.d]

I have never seen this type of clear explanation ever.. Great job 👏 👍

[mohamadzaytoun]

best educational channel ever. good job legends

[pranavi.yalamanchili]

U are one who saves my life thank you 🙏💕

[yagzyalcntas]

I am doing master in TUM for communication engineering, this was way more clear then the lecture thanks :D i looked over the slides again and again but couldnt relate how 1 persistent differs from non-persistant except the behavior after collision.

[harisreereddy]

You said that, In O- persistent CSMA( sub part of Random access protocol), supervisory node decides the order of transmission. Whereas in Random access protocol u said there is no superior node, every node is equal. Can you please explain how this is possible?

[deekshabhat]

The first carrier sense protocol that we will study here is called 1-persistent CSMA (Carrier
Sense Multiple Access). When a station has data to send, it first listens to the channel to see if
anyone else is transmitting at that moment. If the channel is busy, the station waits until it
becomes idle. When the station detects an idle channel, it transmits a frame. If a collision
occurs, the station waits a random amount of time and starts all over again. The protocol is
called 1-persistent because the station transmits with a probability of 1 when it finds the
channel idle. A second carrier sense protocol is nonpersistent CSMA. In this protocol, a conscious attempt
is made to be less greedy than in the previous one. Before sending, a station senses the
channel. If no one else is sending, the station begins doing so itself. However, if the channel is
already in use, the station does not continually sense it for the purpose of seizing it
immediately upon detecting the end of the previous transmission. Instead, it waits a random
period of time and then repeats the algorithm. Consequently, this algorithm leads to better
channel utilization but longer delays than 1-persistent CSMA.
The last protocol is p-persistent CSMA. It applies to slotted channels and works as follows.
When a station becomes ready to send, it senses the channel. If it is idle, it transmits with a
probability p. With a probability q = 1 - p, it defers until the next slot. If that slot is also idle, it
either transmits or defers again, with probabilities p and q. This process is repeated until either
the frame has been transmitted or another station has begun transmitting. In the latter case,
the unlucky station acts as if there had been a collision (i.e., it waits a random time and starts
again). If the station initially senses the channel busy, it waits until the next slot and applies
the above algorithm.

[umairalvi]

You didn't explain p-persistent properly, especially the concept of probability.the probability is calculated randomly and has no relationship with time slots.

[ahmetm.]

What is the limit of that random time exactly ? I mean is it possible to take 1 day or more ? or is it depends

[lanstondavisrobert]

Hello, Is the O Persistent continuously checking or randomly checking ?

[ScottBooker-vq]

Hall Scott Williams George Anderson Jose

[glazefrect]

Why does P persistent CSMA needs to sense the carries if it has specific time slots?

[anisht]

Thankyou dear for the great work, I had a doubt, CSMA/CD is used by Ethernet. Ethernet is end to end, like between two nodes. It has different channel for transmission and receiption, I hope. Then how could a collision occur. Can't understand, correct me if I am wrong. Tell me what I am missing.

[hiraansari]

Plsss make little more easy notes😥...its more bulky #onourhead..
Less points ...Bt need main point

[subhadeepbhakat]

Sir ig the channel utilisation in case of non persistent is much lesser than 1persistant csma

[lunavathsainaik]

Sir please complete the full syllabus of computer networks ( network layer design issues) and other transport layer, session layer, presentation layer, application layer 🎉)

[machinesonearth]

Sir you said that collision occurs in csma but cant the node sense the channel