Pull/Push system which in rmtp

NIKHIL，ThankYou for your help,the article which you suggest("http://www.flashrealtime.com/multicast-explained-flash-101-p2p/comment -page-1/#comment-103042") ,i've readed few days ago;The question ("Pull/Push system which in rmtp") is Just from that article，so i question here (sorry).in that article ，some description that about how to "push",i do not know enough ,such as :"sequence number slice  ","Modulo size of mask"

if you is convenient,please give some explain ,so that we could learn more about it, with best wishes.

###########  from that article ###################

Push

1. Send map of what blocks you have to one (or all) neighbor(s) 
2. Neighbor notices that data is flowing 
3. Neighbor picks candidate sources for each sequence number slice 
4. Neighbor sends mask describing which sequence numbers to push 
5. Modulo size of mask (in this example every 3rd, 5th, and 6th) 
6. Periodically tests other neighbors to check for lower latency 
7. For each sequence number slice, keeps just quickest source 
8. Data is pushed immediately as it arrives for requested slices 
9. For each slice, there is a limit to the number of push clients served

Push then works this way