Citrix NetScaler provides a host of advanced TCP optimizations that accelerate the performance of application traffic by improving the efficiency of the underlying network and still preserving 100 percent interoperability with all clients, servers and the networking infrastructure. While many of these TCP optimizations have been available on NetScaler appliances for some time, what is new is the use of TCP Profiles specific to Citrix XenDesktop and XenApp.

With NetScaler 10, we included a TCP profile for XenDesktop and XenApp traffic that automatically selects those TCP optimizations relevant for ICA traffic flows – with particular attention paid to improving the network performance of small packets, which are common in virtualized desktop and application delivery. The pre-defined TCP profile for XenDesktop/XenApp sets the right parameters to get the very best performance over any network, with just a single click.

Some of these optimizations include TCP Selective Acknowledgement, TCP Window Scaling and Nagle’s algorithm. The net result is that by putting NetScaler in front of your XenDesktop or XenApp infrastructure, your users get a better overall experience because NetScaler optimizes TCP behaviors (e.g. maximum transmission size and retransmission times). Check this blog out for more of the gory details.

NetScaler’s TCP optimizations extend well beyond ICA traffic, of course. NetScaler supports a large number of such TCP optimization features, which can be easily configured through a TCP Profile Wizard just released in NetScaler 10. A few examples include:

  • Selective Acknowledgement. This addresses the problem of multiple packet loss and the resulting reduction of throughput capacity. Receivers can now inform the senders as to the segments successfully received and only retransmit lost packets, not entire sessions.
  • Fast Ramp. Upon packet loss, senders reduce their congestion window and throttle back on data transmission. This window size can now ramp much more rapidly to enable a faster data transfer rate. Provided the network is capable of higher rates, NetScaler exponentially increases this window to quickly maximize transfers.
  • Window Scaling. This allows the TCP receive window to increase beyond 65K bytes. Overall TCP performance is improved, especially in networks with high bandwidth and long delays. Latency is reduced and response times are improved.
  • Nagle’s Algorithm.  Many applications like Telnet and other real time engines result in very small packet sizes; often every new key stroke needs acknowledgement. NetScaler supports Nagle and buffers small packets together and sends them as a group to increase transmission efficiency.

The bottom line is that you don’t need to be a TCP or ICA expert to squeeze the best performance for your Citrix virtual solutions.