Product Documentation

Softboost and Hardboost

Feb 06, 2014

TCP flow control has two modes: softboost and hardboost.

Softboost uses a rate-based sender that sends accelerated traffic at speeds up to the link's bandwidth limit. If the bandwidth limit is set slightly lower than the link speed, packet loss and latency are minimized, while link utilization is maximized. Interactive applications see fast response times while bulk-transfer applications see high bandwidth. Softboost shares the network with other applications in any topology, and it interoperates with third-party QoS systems.

Hardboost is more aggressive than softboost. By ignoring packet losses and other so-called "congestion signals," it performs very well on links plagued with heavy, non-congestion-related losses, such as satellite links. It is also excellent on low-quality, long-haul links with a high background packet loss, such as many overseas links. Hardboost is recommended only for point-to-point links that do not achieve adequate performance with softboost.

Note:
  • Hardboost should be used only on fixed-speed point-to-point links or hub-and-spoke deployments where the hub bandwidth is at least equal to the sum of the accelerated spoke bandwidths.
  • Softboost and hardboost are mutually exclusive, which means that all the Appliances that must communicate with each other must be set the same. If one unit is set to hardboost and the other is set to softboost, no acceleration takes place.
To select softboost mode

Softboost is the default mode and is recommended in most cases.

  1. On the Configuration: Links: Hardboost/Softboost tab, select Softboost as the WAN Boost Mode.
  2. Click Update.

To select hardboost mode

Select hardboost mode only on fixed-speed point-to-point links or hub-and-spoke links where the hub bandwidth is greater than or equal to that of the accelerated spoke links.
  1. On the Configuration: Links: Hardboost/Softboost tab, select Hardboost as the WAN Boost Mode.
  2. Set WAN Bandwidth Receive Limit to 95% of the link speed.
  3. Click Update.