[EME] Re: transport recovery at the APP layer ?

Joe Touch wrote:
> Rémi Després wrote:
>   
>> ... A transport layer acknowledgement (TCP ACK) doesn't mean that the
>> destination application has seen the data.
>>     
> It never did. But receiving an ACK to a FIN does.
>   
However regrettable it may be :'( , it's no true in all cases either.
 If a FIN is received by a TCP stack, it MUST be acked within 0.5 s to 
conform to RFC1122  -  4.2.3.2.
 It MAY be acked long before that. .
 If the application hasn't absorbed all buffered data before the ACK is 
sent, remaining data MAY never be received by the app.

 Since changing all TCP stacks would not be realistic, this fact of life 
has to be faced.
>> I guess what is meant by "E2E" should be clarified: transport stack 
>> to transport stack, or app to app?
>>  TCP provides only the former.
>>  What TCP does guarantee is that all received data have been sent, in
>> the same order and with no intermediate omission.
>>     
> when the connection closes, the app HAS received the data.
>   
 See above.

> ... if the TCP
> connection closes it knows that the other application has received the
> data. That's no longer true in spliced connections.
>   
It's NEVER true (see above).
Making clearer in IETF what the apps can expect from the TCP transport 
service would IMO be useful.

RD