Re: [EAI] AD review of draft-ietf-eai-pop-06

[Alexey Melnikov <[e-mail]>]

Barry Leiba wrote:

>>>  The octet count (size) of a message reported in a response to the
>>>  LIST command SHOULD match the actual number of octets sent in a RETR
>>>  response.  Sizes reported elsewhere, such as in STAT responses and
>>>  non-standardized free-form text in positive status indicators
>>>  (following "+OK") need not be accurate, but it is preferable if they
>>>  are.
>>>      
>>>
>>I would like to hear some justification for returning inaccurate sizes (and
>>for the SHOULD instead of a MUST).
>>    
>>
>It may be that a conversion has to be made in order to get an accurate
>size.  Perhaps an implementation would be well advised to go ahead and
>do the conversion as soon as the size is needed, and then cache the
>converted document until the RETR is done, but that might not be
>practical (suppose a LIST is listing 5000 messages; the server can't
>really convert all 5000 for the list command, and it'd likely then
>have to re-convert the ones that are actually retrieved).
>
>The SHOULD (and the permission to be inaccurate in other responses)
>gives an "out" to the server, allowing it to reserve the expensive
>processing for when the message is actually retrieved.
>
>Because clients have to be changed to ask for this anyway, those
>clients can also understand that they have to deal with a retrieval
>that might be larger than they were led to expect, and they can code
>for it.
>  
>
Note that in IMAP we decided to always return exact sizes. This is true 
for the base IMAP spec and for the CONVERT extension, which is similar 
to what EAI POP3 servers might be doing.

If we want to keep the SHOULD, your last point ("Because clients have to 
be changed to ask for this anyway") needs to be explicitly spelled out. 
I am not sure how existing clients are using results of the LIST 
command. I also think that in this case the document needs to say that 
messages sizes MUST be consistent (i.e. for a given message the server 
must return the same size in LIST all the time).