If we have A and B:
A: 5 6 7 8 9 and
B: -

• A sends #5 - # 9 to B, then B will send a SEND_FIRST_SEQNO to A per message for a total of 5
• A resends #5 with a conn-id of (say) 322649
• B creates the receiver window for A with conn-id=322649 and adds #5, then removes it and acks #5
• A receives an ack for #5 and removes #5 from it sender window
• A then receives the next (stale) SEND_FIRST_SEQNO request
• A now resends #6 with a conn-id=322649
  ---> B drops #6 (and all subsequent messages) with conn-id=322649 !

==> The simple solution is to not drop messages with a conn-id if the receiver window already exists and the conn-ids match

Potential issue: what if we re-send #6 with conn-id=322649 before #5 with conn-id=322649 ?

• A message on the sender side is only removed if it received an ACK from the receiver
• Reception of an ACK means the receiver window was created
• When we receive ACK(5), that means we created a receiver window on B with conn-id=322649 and added #5
• Therefore the re-sending of #6 with conn-id=322649 will never happen before the receiver window on B is created for #5 and conn-id=322649 !