About transport settings

After applying your settings, you can verify whether the changes have had the desired effect by reviewing the Current Connections report. This report provides a summary of established connections that are being optimized through SCPS.

SCPS connections are categorized as typical established, optimized, or single-ended optimized connections. To view specific details about a connection, simply click on it within the report.

In the SCPS connection detail report, you’ll see either SCPS Initiate or SCPS Terminate listed under the Connection Information section, depending on whether the SteelHead initiated or terminated the SCPS connection. Additionally, under the Congestion Control section, the report displays the specific congestion control method that the connection is currently using.

About TCP, SCPS, and SkipWare

About high-speed TCP

Identifies the optimal TCP configuration by using the same mode as the peer appliance for inner connections. It defaults to SkipWare when negotiated, or standard TCP for all other cases.

If your environment consists of a mix of different network types connecting to a hub or server-side SteelHead, you can enable this setting on your hub appliance. This allows the hub appliance to reflect the various transport optimization mechanisms used by your remote site appliances.

Appliances advertise their automatic TCP detection capabilities to peers through their out-of-band (OOB) connections.

Applies data and transport streamlining to non-SCPS TCP connections. When enabled, this setting forces peers to use standard TCP as well. It also clears any previously set advanced bandwidth congestion control settings.

Enables high-speed TCP optimization, designed to make more complete use of long fat pipes (high-bandwidth, high-delay networks). However, it should not be enabled for satellite networks.

We recommend enabling high-speed TCP optimization only after carefully evaluating whether it will benefit your specific network environment. Additionally, this feature can be enabled using the tcp highspeed enable command.

Uses an intelligent algorithm along with a modified slow-start algorithm to optimize performance in long, lossy networks like satellite, cellular, microwave, or Wi-Max networks. This feature is a sender-side modification of TCP and is compatible with other TCP stacks.

Estimation is based on the analysis of ACKs and latency measurements. The modified slow-start enables faster ramp-up in high-latency environments compared to traditional TCP. The intelligent bandwidth estimation algorithm allows it to learn effective transmission rates for use during modified slow start. Additionally, it can differentiate between bit error rate (BER) loss and congestion-derived loss, managing both types appropriately.

Bandwidth estimation offers good fairness and friendliness toward other traffic on the same network path.

Applies TCP congestion control to each SCPS-capable connection. The congestion control uses:

This transport setting uses a modified slow-start algorithm and a modified congestion-avoidance approach. When enabled, SCPS per-connection ramps up flows faster in high-latency environments and handles lossy scenarios while remaining reasonably fair and friendly to other traffic. SCPS per-connection is especially effective in satellite networks, offering high performance.

We recommend enabling per-connection if the error rate in the link is less than approximately 1 percent.

Accelerates SCPS and provides error-rate detection and recovery. This setting allows per-connection congestion control to tolerate some loss due to corrupted packets (bit errors), without reducing throughput, using a modified slow-start algorithm and a modified congestion-avoidance approach. It requires significantly more retransmitted packets to trigger this congestion-avoidance algorithm than the SkipWare per-connection setting. Error-tolerant TCP acceleration assumes that the environment has a high BER and that most retransmissions are due to poor signal quality instead of congestion. This method maximizes performance in high-loss environments, without incurring the additional per-packet overhead of a forward error correction (FEC) algorithm at the transport layer.

SCPS error tolerance is a high-performance option for lossy satellite networks. Use caution when enabling this feature, particularly in channels with coexisting TCP traffic. It can be quite aggressive and adversely affect channel congestion with competing TCP flows. We recommend enabling this feature if the error rate in the link is more than approximately 1 percent.

Enables the Cubic congestion control algorithm, which offers better performance and faster recovery after congestion events than NewReno, the previous local default.