Problem on RTP session

Question

Consider an RTP session consisting of 5 users, each of which are sending and receiving RTP packets into the same multicast address. All user sends video at 200kbps.

a) At what rate the RTCP will limit its traffic to?

b) By how much RTCP bandwidth a specific sender will be assigned?

c) How much RTCP bandwidth a particular receiver will be allocated?

Answer 1

A) The session bandwidth is 5 * 200 kbps = 1000 kbps.
As RTCP attempts to limit its traffic to 5% of the session bandwidth. Hence,
Then, 5% of the session bandwidth is 50 kbps that RTCP will limit its traffic to.

B) Each user is both a sender and receiver where each gets 50 kbps for RTCP packets as calculated above. 
The protocol gives 25% of this rate to the sender
                            = 50 * .25
                            = 12.5 kbps

Hence, sender will be allocated 12.5kbps of RTCP bandwidth.

C) Each user is both a sender and receiver while each user gets 50 kbps for RTCP packets as calculated above.

The protocol gives 75% of this rate to the receivers i.e.
                                     =  50 * .75
                                     =  37.5 kbps
As given, total no of users = 5

So, if there is one sender then there will be remaining R=4 users are as receivers to achieve multicast. Hence,

Each receiver will be allocated 37.5 / 4 = 9.375 kbps of bandwidth.