[E-Lang] security, comms, ordering guarantees

[Ralph Hartley]

Karp, Alan wrote:

>Ralph Hartley wrote:
>
>>This strong form is what willl be used most often. Most applications 
>>cannot be expected to make sense of out of order 
>>communications, there's 
>>just too much subtlety involved.
>>
>There are plenty of times when messages can be handled in receive order.
>The most common case is sending a large amount of data in separate pieces.
>As another example, it doesn't matter in what order a sequence of deposits
>(I should be so lucky :) appear in my account, but withdrawals need to be
>ordered properly with respect to deposits.
>
If I thought there were NO situations where weaker ordering was usefull, 
I wouldn't have written about them.

>Switching normally involves a handshake, but we have a patent (sorry MarkM)
>that lets the sender inform the receiver of whether messages must be
>processed in send order or if they can be processed in receive order.  The
>idea is entries in the message header that say "This is the Nth message.
>You may process it after handling the Kth message."  If K=N-1, we have
>send-order processing.  If, instead, K=N-M, then M messages can be processed
>in the order received.
>
Your (more than likely invalid) patent doesn't really cover what we are 
talking about here. We are considering the order in which messages are 
DELIVERED, only for some applications is there even a concept of 
messages being "processed".

In any case, it is more often the recipient, not the sender, who is in a 
position to judge what order to process the messages in. Only the 
recipient knows how many messages were recieved, and in what order, and 
has any idea of the cost of getting a different order. Ordering 
constraints are a contract with the reciever, which the reciever may 
chose waive ((b weak) allows this). The sender might advise, but it 
can't enforce the order anyway.

In most cases, the order sensitivity of messages is fixed by the 
(application layer) protocol anyway, the applications already know if it 
matters or not. I wouldn't expect per-message canges in ordering policy 
to be all that common.

Ralph Hartley

I wouldn't expect the patent office to notice, but if your what you 
describe was invented AFTER the telgraph, I would be supprised.