Intermittent Connectivity Means…
Continuous end-to-end transmission through relay elements may be impossible, due to time-disjoint episodes of connectivity at adjacent relays.
- So relays can’t just route packets. Relays must store incoming packets, forwarding them when opportunities arise.
End-to-end retransmission would reserve resources (retransmission buffer) at originator for entire duration of the transaction – possibly days or weeks.
- So most retransmission should be point-to-point rather than end-to-end, between relays rather than between endpoints.