Reliable BCAST
n Each node keeps cache of recently transmitted packets
(FIFO, small)
n Each node, upon receiving packet X from sender S, checks
whether it received packet X-1 from that sender
Ø If not, broadcast retransmission request (NACK) to 1-hop
neighbors
Ø Neighbors listen to overhear other retransmission and cancels
theirs
n First set of experiments revealed that under high traffic
load, too many NACKs were issued, flooding the network
and resulting in overall worse performance (70% PDR for
10 sender scenarios)
n Added feature: NACK throttle