[ih] principles of the internet

[John Day]

At 11:10 -0700 2010/06/03, Dave Crocker wrote:
>>applications could relay (and hence need
>>routing) but mail didn't do end to end error control, but check-point
>>recover in FTP did.
>
>
>It's worth noting that check-point restart was a later addition to 
>FTP.  My impression is that it's had limited uptake.

Really.  Later when?  It was in the 1973 version.  Also in the UK 
color books which actually had a sliding window.

>
>Email later added data integrity, through MIME Content-MD5, and as a 
>side-effect of content protection through PEM, PGP or S/MIME and, 
>more recently, DKIM, if one is loose about the function.  It also 
>added delivery confirmation and error reporting via DSN and MDN 
>notifications.  It had non-standardized non-delivery notices pretty 
>much from the start; these were later standardized.  These all 
>provide a pretty good platform for developing a re-transmission 
>mechanism, if the sender wishes to pursue it.

Integrity, yes. But not reliability.  There is no MPL for mail.

>
>(email relaying was also a later value-added mechanism, first 
>through Parc's internal conventions, UUCP such as at Berkeley and 
>CSNet at Udel; later standardized through DNS MX records, but let's 
>not go down that... path.)

Correct.  Mail was originally two commands in FTP, but that must have 
been later.

Take care,
John

>
>d/
>--
>
>   Dave Crocker
>   Brandenburg InternetWorking
>   bbiw.net