The Silver Peak solution provides a variety of optimization techniques to mitigate WAN latency. These include:
TCP Acceleration
Silver Peak optimizes the performance of TCP across the WAN by employing the following functions:
Window Scaling - Silver Peak utilizes the TCP Window Scale option to deliver window sizes as large as 1GB. This overcome the throughput limitation imposed by the standard 64 KB TCP window size in higher latency networks.
Selective Acknowledgement - Selective acknowledgements (SACK) provide a mechanism for handling multiple packet loss in a WAN environment. They give the sender a complete picture of which segments are queued at the receiver and which have not yet arrived, enabling the sender to retransmit only the missing data segments
Round-Trip Measurement - Silver Peak utilizes a proprietary round trip measurement scheme that enables RTTs to be calculated more efficiently. This leads to more accurate RTO (retransmission timeout) measurements which, in turn, improves throughput.
HighSpeed TCP- Silver Peak has implemented HighSpeed TCP, which is a modification to TCP's congestion control mechanism for use with TCP connections with large congestion windows. It alters how the window is opened on each round trip and closed on congestion events as a function of the absolute size of the window. This enables TCP to perform better in high-bandwidth, high-latency environments.
CIFS Acceleration
Silver Peak optimizes the performance of Microsoft's CIFS protocol, which is notorious for performing poorly across a WAN due to excessive "chattiness". Specific CIFS optimization features include:
CIFS Read-ahead - when a user is working with a file, Silver Peak appliances generate read ahead requests within the file in order to pipeline operations to the server, thus eliminating the round-trip delay associated with waiting for acknowledgement. This minimizes the latency associated with read operations.
CIFS Write-behind – Silver Peak NX appliances pipeline write operations on behalf of a client, thus eliminating round-trip delays associated with waiting for acknowledgements. This minimizes the amount of round trips required to perform write operations, improving performance without risking data integrity.
CIFS Meta Data Optimizations – standard Microsoft clients make many unnecessarily independent and duplicative requests for file and directory meta-data. Performance is enhanced by locally consolidating and responding to these requests.
SIlver Peak's Unique Advantages
Silver Peak is able to perform Network Acceleration at very high data rates. With appliances that scale up to 1 Gbps on the WAN side and 10 Gbps on the LAN side, Silver Peak can overcome latency on even the largest of WAN links.
Silver Peak also combines standard Network Acceleration features with its Network Integrity features to address the combined impact of loss and latency. The two of these issues together have a “saw tooth” effect on WAN performance, which can result in erratic effective throughput. By addressing both of these issues in tandem, Silver Peak offers a robust solution for WAN acceleration.
