Re: [TLS] record layer limits of TLS1.3

[Yoav Nir <[e-mail]>]

> On 24 Nov 2016, at 15:47, Hubert Kario <[e-mail]> wrote:
> 
> On Wednesday, 23 November 2016 10:50:37 CET Yoav Nir wrote:
>> On 23 Nov 2016, at 10:30, Nikos Mavrogiannopoulos <[e-mail]> wrote:
>>> On Wed, 2016-11-23 at 10:05 +0200, Yoav Nir wrote:
>>>> Hi, Nikos
>>>> 
>>>> On 23 Nov 2016, at 9:06, Nikos Mavrogiannopoulos <[e-mail]>
>>> That to my understanding is a way to reduce
>>> latency in contrast to cpu costs. An increase to packet size targets
>>> bandwidth rather than latency (speed).
>> 
>> Sure, but running ‘openssl speed’ on either aes-128-cbc or hmac or sha256
>> (there’s no test for AES-GCM or ChaCha-poly) you get smallish differences
>> in terms of kilobytes per second between 1024-byte buffers and 8192-byte
>> buffers. And the difference going to be even smaller going to 16KB buffers,
>> let alone 64KB buffers.
> 
> this is not valid comparison. openssl speed doesn't use the hardware
> accelerated codepath
> 
> you need to use `openssl speed -evp aes-128-gcm` to see it (and yes, 
> aes-gcm and chacha20-poly1305 is supported then)
> 
> What I see is nearly a 1GB/s throughput increase between 1024 and 8192 byte blocks for AES-GCM:
> 
> type             16 bytes     64 bytes    256 bytes   1024 bytes   8192 bytes
> aes-128-gcm     614979.91k  1388369.31k  2702645.76k  3997320.76k  4932512.79k
> 
> While indeed, for chacha20 there's little to no difference at the high end:
> type             16 bytes     64 bytes    256 bytes   1024 bytes   8192 bytes  16384 bytes
> chacha20-poly1305   242518.50k   514356.72k  1035220.57k  1868933.46k  1993609.50k  1997438.98k
> 
> (aes-128-gcm performance from openssl-1.0.2j-1.fc24.x86_64, chacha20-poly1305 from openssl master, both on 
> Intel(R) Core(TM) i7-6600U CPU @ 2.60GHz)

Cool. So you got a 23% improvement, and I got an 18% improvement for AES-GCM. I still claim (but cannot prove without modifying openssl code (maybe I’ll do that over the weekend) that the jump from 16KB to 64KB will be far, far less pronounced.

Yoav