Add concept of ordered channels? about bud

[neilconway]

See also #26.

[neilconway]

Random thought: tcp provides an ordered stream abstraction, but for many applications, the receiver can consume network messages out-of-order in certain (many) circumstances (eg commutative operations, multiplexing multiple application-level sessions over a single channel). Providing "too much" ordering harms performance, because 1. It prevents forward progress due to needless waiting 2. It results in not sending the packet that would be most useful to the receiver. Naturally, these factors are most significant when there is significant packet loss (eg wireless).

Hence, what about pushing program semantics down to the transport layer? When we can prove that delivering a packet "out of order" is equivalent to in-order delivery, we can deliver that packet to the recipient application early. We might also be able to leverage program semantics to do more intelligent retransmission: we should be more aggressive about retransmission of packets that block the forward progress of the recipient.