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Re: How to download over https



Pascal Hambourg:
> Le 16/06/2016 22:13, Dan Purgert a écrit :
> 
>> as well as making the overall amount of data
>> transmitted somewhat larger.  This is because encrypted blocks have
>> specific size requirements (...)
>> 
>> Remeber that a single packet can only carry 1460 bytes, before
>> accounting for services that specify MTUs <1500 .  If you're using
>> something like 64-byte blocks for the encryption scheme (which is fairly
>> common, so I'm going with that from here on out), you're limited to only
>> sending 1408 bytes / packet of actual data, assuming zero overhead.  For
>> the 660 602 880 bytes of "cd1" from the debian installer suite, this
>> means you're transmitting 469,178 fully loaded packets, plus 1 partial
>> (approx 315 bytes) ... or a total transmission of 689 691 975 bytes.
> 
> Hmm. I don't know how SSL works, but HTTPS runs on top of TCP so I doubt
> that it cares about IP packet size. The task of splitting the TCP payload
> stream into IP packets is done by the TCP layer.

Sure, but if your encryption scheme wastes payload in yout packets you
have more overhead for TCP/IP headers in each packet. I have yet to
actually meet someone who optimizes on that level but at Google scale
these things obviously matter.

J.
-- 
Whenever I hear the word 'art' I reach for my visa card.
[Agree]   [Disagree]
                 <http://archive.slowlydownward.com/NODATA/data_enter2.html>

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