Seonglae ChoSelective Repeat ARQ
receiver 측에서 받은 각각의 패킷들에 대해 ACK
receiver individually acknowledges all correctly received packets and sender times-out/retransmits individually for unACKed packets. sender maintains timer for each unACKed pkt
That is why sequence number space is at least twice than window size
Sender window
consecutive seq #s which limits seq #s of sent, unACKed packets
Sender
Problems
Receiver can’t see difference of the sender’s side situation.
- Request packet lost
- Response packet lost
so large sequence number and random
