SSL, Bandwidth, & High Latency...
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Anyone out there have any good references on how to improve TCP/SSL performance on high latency connections. We see bandwidth dropping radically as latency increases... would like to get rid of this issue. I don't see much of anything in the socket options. I also cannot switch away from TCP, am required to use SSL. Oh, and I really cannot mess with the registry... And am using OpenSSL for my SSL overhead. Any thoughts to share?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Peter Weyzen Staff Engineer [SoonR Inc.](http://www.soonr.com) -
Anyone out there have any good references on how to improve TCP/SSL performance on high latency connections. We see bandwidth dropping radically as latency increases... would like to get rid of this issue. I don't see much of anything in the socket options. I also cannot switch away from TCP, am required to use SSL. Oh, and I really cannot mess with the registry... And am using OpenSSL for my SSL overhead. Any thoughts to share?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Peter Weyzen Staff Engineer [SoonR Inc.](http://www.soonr.com)Where/when is the latency, how are you measuring it, and where is it coming from? Depending on when the latency occurs, it could definitely impact throughput. Mark
"If you can dodge a wrench, you can dodge a ball."
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Where/when is the latency, how are you measuring it, and where is it coming from? Depending on when the latency occurs, it could definitely impact throughput. Mark
"If you can dodge a wrench, you can dodge a ball."
It's not a measured thing unfortunately. We have this client/server thingy. I am in California and the server is in California. I don't have much trouble with throughput. But I have this user in Denmark who is trying to connect to the serer in California. He's got a soooper high speed connection to the internet... but can only get limited bandwidth between his client and our server. I am very confident in his connection...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Peter Weyzen Staff Engineer [SoonR Inc.](http://www.soonr.com) -
It's not a measured thing unfortunately. We have this client/server thingy. I am in California and the server is in California. I don't have much trouble with throughput. But I have this user in Denmark who is trying to connect to the serer in California. He's got a soooper high speed connection to the internet... but can only get limited bandwidth between his client and our server. I am very confident in his connection...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Peter Weyzen Staff Engineer [SoonR Inc.](http://www.soonr.com)Try increasing the TCP window size, on both client and server, for both send and receive buffers. See SO_SNDBUF and SO_RCVBUF, in the Winsock docs. The buffers should be sized to approximately RTT (round trip time) times the bandwidth of the smallest pipe. So, you really need to get a good estimate of RTT (try ping), and it really doesn't matter if your Danish user has a huge pipe if you are shipping it up to him through a 1500/300 ADSL link. If you don't have access to code, there are some registry tweaks available as described (e.g.,) at "Windows 2000 TCP Performance Tuning Tips" at http://rdweb.cns.vt.edu/public/notes/win2k-tcpip.htm[^]. There are lots of sites like that one (search on "SO_RCVBUF SO_SNDBUF RTT bandwidth"). The Win2k registry entries are the same in WinXP. Mike
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Try increasing the TCP window size, on both client and server, for both send and receive buffers. See SO_SNDBUF and SO_RCVBUF, in the Winsock docs. The buffers should be sized to approximately RTT (round trip time) times the bandwidth of the smallest pipe. So, you really need to get a good estimate of RTT (try ping), and it really doesn't matter if your Danish user has a huge pipe if you are shipping it up to him through a 1500/300 ADSL link. If you don't have access to code, there are some registry tweaks available as described (e.g.,) at "Windows 2000 TCP Performance Tuning Tips" at http://rdweb.cns.vt.edu/public/notes/win2k-tcpip.htm[^]. There are lots of sites like that one (search on "SO_RCVBUF SO_SNDBUF RTT bandwidth"). The Win2k registry entries are the same in WinXP. Mike
Hey Mike Great reply. From a programmer with minimal IT skills - Thanks for the info! Mark
"If you can dodge a wrench, you can dodge a ball."