Have you ever wondered while chatting in a Whatsapp group that why exactly one set of people are listening to your chat and not your full list of contacts, Or for that matter when you order a VOD or a live feed of a match why the whole world is not seeing Or when you send a mail to your team that you are taking a leave why the whole company is not receiving it. Welcome to the world of Multicast ! We all do Multicasting in some form or other everyday from time Immemorial.
Remember in School days when we used to share some jokes with few of our friends only or your favorite sports teacher giving some important sports tips to you only. Multicasting is all about multiple Receivers with typically one active sender at that point of time.
The funny thing is that IP Multicasting works following the same set of principles. Interested Receivers become part of a Group. The sender sends the packets(or data) and everyone part of the Group receives it.
Now how do you know which group you would want to be. In real life you would like to be part of a group by filling up a form or talking to the Group Leader. This is the job of IGMP protocol. The Host here talk to the First Hop Router that I would like data from this Group. This is analogous to you talking to the Class Teacher or the Monitor about your interest in certain topic and it was their responsibility to give you the correct information.
Now how exactly your Class Teacher knows when the topic of your interest is scheduled and to notify you? May be she used to get that information from your Principal or from other teachers and they from other authorities who have a direct connection with the originator of the information. These are exactly the control messages that are carried over in another interesting protocol called PIM.
Basically IP Multicast can be divided into two parts Data from the Source coming to the directly connected Router. This part is handled by PIM. The second part is the interested hosts subscribing for that Data. This is achieved by IGMP.
Does PIM uses any special way of knowing whom to send the data. The answer again lies in our good old school example. Does your Principal use any special method for telling to your Class Teacher about your interest. The answer is No. The Principal knows which Teacher is Managing which class. So all she needs to know whether the Student belongs to this class, and if yes provide the data to this Class Teacher. PIM also uses the existing Routing Protocols only to know its neighbors and ultimately get to the First Hop IGMP Router (the Class Teacher). Now what happens if for an existing Class the students don't require a particular information any more. Does the Principal still gives the same information to the Class Teacher. The answer is again No, as this information is of no use to the Class Teacher. PIM also follow the same principle where if hosts have sent IGMP leave messages for a Group and there are no more interested Host the First Hop Router would send a PIM leave message towards the Source. Simple Isn't it ? Well somewhat but not completely :)
PIM has its different flavors in PIM-DM, PIM-SM. Similarly IGMP also has various versions in V1, V2 and V3. Interested Readers can read numerous materials available over the Internet to satisfy their need to learn more on these topics. This was my own humble way of explaining this complicated topic in a simplistic manner. The actual protocols have nuances that require good amount of networking knowledge to appreciate. I would try and add more stuffs in near future to enjoy the beautiful world of Technology. I would be partial to Networking subjects as I have some knowledge on these areas :)
Remember in School days when we used to share some jokes with few of our friends only or your favorite sports teacher giving some important sports tips to you only. Multicasting is all about multiple Receivers with typically one active sender at that point of time.
The funny thing is that IP Multicasting works following the same set of principles. Interested Receivers become part of a Group. The sender sends the packets(or data) and everyone part of the Group receives it.
Now how do you know which group you would want to be. In real life you would like to be part of a group by filling up a form or talking to the Group Leader. This is the job of IGMP protocol. The Host here talk to the First Hop Router that I would like data from this Group. This is analogous to you talking to the Class Teacher or the Monitor about your interest in certain topic and it was their responsibility to give you the correct information.
Now how exactly your Class Teacher knows when the topic of your interest is scheduled and to notify you? May be she used to get that information from your Principal or from other teachers and they from other authorities who have a direct connection with the originator of the information. These are exactly the control messages that are carried over in another interesting protocol called PIM.
Basically IP Multicast can be divided into two parts Data from the Source coming to the directly connected Router. This part is handled by PIM. The second part is the interested hosts subscribing for that Data. This is achieved by IGMP.
Does PIM uses any special way of knowing whom to send the data. The answer again lies in our good old school example. Does your Principal use any special method for telling to your Class Teacher about your interest. The answer is No. The Principal knows which Teacher is Managing which class. So all she needs to know whether the Student belongs to this class, and if yes provide the data to this Class Teacher. PIM also uses the existing Routing Protocols only to know its neighbors and ultimately get to the First Hop IGMP Router (the Class Teacher). Now what happens if for an existing Class the students don't require a particular information any more. Does the Principal still gives the same information to the Class Teacher. The answer is again No, as this information is of no use to the Class Teacher. PIM also follow the same principle where if hosts have sent IGMP leave messages for a Group and there are no more interested Host the First Hop Router would send a PIM leave message towards the Source. Simple Isn't it ? Well somewhat but not completely :)
PIM has its different flavors in PIM-DM, PIM-SM. Similarly IGMP also has various versions in V1, V2 and V3. Interested Readers can read numerous materials available over the Internet to satisfy their need to learn more on these topics. This was my own humble way of explaining this complicated topic in a simplistic manner. The actual protocols have nuances that require good amount of networking knowledge to appreciate. I would try and add more stuffs in near future to enjoy the beautiful world of Technology. I would be partial to Networking subjects as I have some knowledge on these areas :)
