I’m using Apache 2.2 running on Windows Server 2008 R2 as a WebDAV server for clients to upload large media files (roughly 100-2000MB). I am finding that when I have SSL enabled (openSSL 0.9.8o) and use HTTPS for the uploads the throughput is around 13Mbps but when I disable it and just use HTTP I get around 80Mbps. I can’t understand why this is happening as my understanding was that the heavy SSL work was done at the beginning of the connection.
If it helps the client that I am using is command line cURL and here is the command:
curl -k -f -u digital:recorder -T 00320120321101048_ch1.mkv http://mediaserver/webdav/ curl -k -f -u digital:recorder -T 00320120321101048_ch1.mkv https://mediaserver/webdav/
Does anyone have any idea why the performance is so drastically affected by enabling SSL?
UPDATE: The problem does not exist on Windows 7 clients so this only happens on XP. This at least identifies that the issue is at the client end. I am running the exact same command line from both systems but it only affects WinXP. Does anyone know of why that might be? That XP is somehow crippling the SSL upload speed?
I’ve run tests on Fedora Linux as well. So the issue has now been closer defined to be that the same version of cURL + OpenSSL uploading the same file to the same server is fast on Linux and Windows 7 but very slow on Windows XP.
Can anybody help with this because I’ve really hit a brick wall!
Well the answer was that this was an issue with the way that Windows XP handles SSL packets. Strange but true. In the end we modified the cURL library ourselves to avoid the problem.
For anyone else having this problem with Apache as the WebDAV target then I found that another option is to use the SSLCipherSuite directive to change the encryption level to MEDIUM (the default is HIGH). This means that it uses 128-bit RSA rather than 256-bit AES encryption which sped up the throughput to almost non-encrypted speed levels. This may or may not help on IIS servers as I haven’y had a chance to try this yet.
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