Alteon HTTP Compression

Scenario

Compression Definition

HTTP compression is a technique to reduce data size and improve transfer speed and bandwidth utilization. Compression is implemented on servers and client web browsers.

HTTP data is compressed before it is sent from the server: compliant browsers will announce to the server what methods are supported before downloading the correct format. Browsers which do not support compliant compression method will download uncompressed data.

The most common compression schemes include gzip and Deflate. There are other compression methods like SDCH, Brotli, Xpress, XZ etc.

The web client communicates preferred compression methods using the Accept-Encoding HTTP header. For example: Accept-Encoding: gzip, deflate.

The web server communicates the used compression method with the content encoding header: For example: Content-Encoding: gzip.

Configuration

Why is it Better to Compress on the Server Side Instead of on Alteon?

Modern server implementations have up to date modern compression libraries that can compress data efficiently without noticeable performance overhead on the server. In addition, the compression ratio for gzip and deflate is approximately 20% better when the compression algorithm is calculated over the whole resource body.

Since the web servers usually store most of the resource data locally, the compression is most efficient if done on the server side. Inherently, in ADC scenarios (forward proxy or middle box), the proxy compresses only the current available piece of the data and not the complete resource. This can cause less than optimal compression output.

When should Compression on Alteon be Used?

When the following content modification features are enabled:

Fastview

Body Modifications

Traffic Inspection

The ADC needs to process the clear text version of the content, hence a decompressed payload must be available in order to have decompressed payload. The ADC can choose either to ask the server to not compress any of the data and send clear text payload (not recommended) or to receive compressed data from the server and decompress according to demand.

Compression Throughput of Alteon D-Line for Various Platforms

When compression is enabled, Alteon D-Line can scale with below performance

Platform Throughput
5208 D-Line 3.5 Gbps
6024 D-Line 5.5 Gbps
6420 D-Line 6 Gbps
7612 D-Line 16 Gbps
7220 D-Line 16 Gbps
8420 D-Line 20 Gbps