hello everyone welcome back to the next lecture in the computer Network series and today we will see the multiple access protocols as usual let's start the session with outcomes upon the completion of this session the learner will be able to know the various multiple access protocols before going into the topic of multiple access protocols let's see an analogy the analogy is let's assume in a classroom full of students when a teacher asks a version and all the students start answering simultaneously a lot of chaos is created then how to handle this it is the job of the teacher to manage the students and make them answer one at a time then how this analogy is related in computer network in computer network if we have an exclusive channel or medium between the sender and the receiver then nobodies but if the channel or medium is shared among many stations or nodes then just like that we cannot send the data because the channel may already be involved in data transmission between any other two nodes if any station or node wants to send data without knowing the status of the channel or the medium that is whether the channel or the medium is busy or idle then the data can be lost or the data can be corrupted or the data can be overlapped in the analogy the teacher resolves the chaos in computer network the multiple access protocols resolves this chaos let's see why do we need multiple access protocols in detail if there is a dedicated link between the sender and the receiver then data link control layer is sufficient that is since the channel is exclusively between the sender and the receiver we need not worry about it however if there is no dedicated link present between the sender and the receiver then multiple stations can access the channel simultaneously if multiple stations can access the channel simultaneously it has to be handled because there is a serious problem called collision hence multiple access protocols are required to decrease collision and avoid crosstalk collision means if two or more stage for North Saint data at the same time without checking the status of the channel whether it is BC or a little then the data will be colliding with each other and it becomes unusable and that is why we need multiple access protocol this multiple access protocol is mainly necessary for channels that are not exclusively between the sender and the receiver it means if the channel is a shard 1 then we need multiple access protocols let's see what are the various multiple access protocols the multiple access protocols involved the random access protocols the controlled access protocols and the channelization protocols so basically we have three types let's start with the random access protocols the name itself says that the random access protocols where any station can send the data in any time but obviously there are chances for collision in this all station have same superiority that is no station has more priority than any other station it means if random access protocols are deployed then all stations have same priority all are equal in the network so any station can send data depending on the medium state that is idle or busy that any station can send data at any attempt but obviously it leads to collision in a random access method or protocol each station has the right to the medium that is the channel without being controlled by any other station because all stations have same superiority nobody is inferior and nobody is superior so if more than one station tries to send there is an access conflict which we call as an collision and the frames will be either destroyed or modified since there is a possibility of collision in random access protocol it is a must to resolve it how it is resolved in random access protocol let's see it now to avoid access conflict or collision each station must follow a procedure this procedure is the nature of the protocol let's see what are the things that are dealt with the procedures when the station can access the medium what can the station do if the medium is busy how can the station determine the success or failure of the transmission what can the station do if there is an access conflict all these questions will be addressed by the procedure where this procedure is the random access protocol let's see what are the various random access protocols basically we have multiple access protocols as random access protocols controlled access protocols and channelization protocols let's see random access protocols we have aloha csma that is carrier sense multiple access carrier sense multiple access with collision detection and carrier sense multiple access with collision avoidance anyway don't worry about these protocols anyway we are going to deal about these protocols labret Lee in the upcoming lectures so far we are done with random access protocols now let's move on to the next protocol that is the controlled access protocol controlled access protocol in the random access protocol nobody is inferior and nobody is superior so nobody controlled the channel whereas in controlled access protocol the station's consult one another to find the station has the right to send so in this method the medium will be controlled by the station a station cannot send unless it has been authorized by other stations here whoever is getting the turn to send the data they are superior at that moment so when other station cancelled this station to send the data it will not authorize that so this is what a controlled access protocol concept is let's see what are the protocols that are coming under controlled access protocols we know controlled access protocol is the second type we are addressing and it has reservation polling and token passing let's see it elaborately in the upcoming lectures for time being now you note only these are the three methods coming under controlled access protocols and the last type of medium access protocol is the channelization protocol channelization is a multiple access method or a protocol in which the available bandwidth of a link is shard in time frequency or through code between stations if there is a channel and that channel is obviously a shared channel because it is going to be used by more than one stations in that case the bandwidth of the channel is going to be shared in terms of time frequency or code and that's the concept of channelization protocol let's see what are the schemes or methods coming under channelization protocols we know channelization is the third protocol that we are addressing in multiple access protocol and the schemes or methods are FDMA TDMA and CDMA that is frequency division multiple access time division multiple access and code division multiple access and that's it guys I hope now you are clear with the various multiple access protocols the various multiple access protocols are random access protocols controlled access protocols and channelization protocols I hope you guys enjoyed the session and thank you for watching [Applause] [Music]