Configure TCP Acceleration

TCPTransmission Control Protocol Acceleration is the heart of Exinda's application acceleration technology. All accelerated connections pass through TCP Acceleration. In order to accelerate traffic over the WANWide Area Network, Exinda transparently proxies TCP connections at each end. Both the client and server think they have established a connection with each other; however, they have connected with their local Exinda devices.

In addition to facilitating other acceleration technologies like WAN Memory and SMB acceleration, TCP acceleration also provides performance improvements over and above regular TCP, while being fully compliant with TCP.

You can configure various settings for TCP acceleration.

  • Acceleration occurs between two Exinda appliances. The appliances can discover other appliances on the network that they can accelerate with. You can configure whether your appliance will attempt to discover other appliances and which IPInternet protocol address your appliance will use when other appliances discover your appliance.
  • TCP acceleration and auto-discovery require the use of custom TCP options. If other equipment is stripping the required TCP option from the TCP headers, you can specify that the TCP accelerated traffic must tunnel to avoid the options being stripped. Once a connection is setup via the protocol tunnel, subsequent connections can use the protocol connection and avoid the 3-way TCP handshake, which will reduce the number of TCP connections traversing the WAN and reduces the TCP connection setup time.
  • Also TCP option 30 which historically has been used to indicate Exinda acceleration, has been assigned to indicate multi-path TCP. Exinda now uses both option 30 and option 230 to indicate Exinda acceleration. You can specify which option code should be used in acceleration. Your choice will depend on the Exinda appliance version you are using and whether you are seeing multi-path TCP traffic in your network. Also you can indicate not to accelerate traffic (bypass acceleration) when traffic is using multi-path TCP.
  • Throughput is limited by two windows: the TCP receive window size and the congestion control window. Setting the appropriate sizes for these windows can ensure efficient use of the available bandwidth:
  • Windows scaling increases the TCP window size, which allows more data to be in-flight before TCP requires acknowledgments. This means higher throughput can be achieved on WAN links with higher levels of latency.
  • Selectable congestion control algorithms can be chosen to match the WAN environment. For instance, for high speed high latency links, High Speed TCP should be used. For Satellite links, or other high-latency links, TCP Hybla should be used. This allows for better TCP performance over different WAN technologies.
  • Adaptive Initial Congestion Window allows automatic adjustment of the initial window size depending on the connectivity properties of the WAN link between the Exinda appliances.
  • Slow Start with Congestion Avoidance is used to reset the send window size temporarily to avoid congestion.
  • TCP keep-alive signals prevent the link between accelerated appliances from being broken. You can set whether to use keep-alives and how frequently to send the keep-alive signals.
  • When accelerating traffic in a backhauled setting, the dual-bridge bypass setting will ensure that acceleration processing happens on only one bridge so that the traffic is not re-accelerated. This option, by default, is disabled.
  • When you know that a particular Exinda is always at the end of an acceleration chain, you can indicate that it is the end and therefore should not pass through option 30 packets. This is useful when the traffic is transported to a server or firewall that does not know how to handle option 30 packets or when the traffic is forwarded to the Internet. Note that you should not use this setting if the Exinda appliance is also an Exinda in the middle in some scenarios.

Furthermore, TCP acceleration also provides performance improvements without requiring configuration:

  • Delayed and Selective Acknowledgments are used to acknowledge the receipt of packets in batches, instead of acknowledging every single packet. This reduces the amount of return data on the wire.
  • Explicit Congestion Notification (ECN) allows end-to-end (between the Exinda appliances) notification of network congestion without dropping packets. Traditionally, TCP/IP networks signal congestion by dropping packets. When ECN is enabled, an ECN-aware router may set a mark in the IP header instead of dropping a packet in order to signal impending congestion.

Use the form below to configure various TCP Acceleration settings.