Overview
The transfer rate of assets on the CDN can be throttled via URL parameters or via a static configuration that applies to specific User-Agents.
Throttling via URL Parameters
There are a number of parameters that can be added to the HTTP query string that control the delivery behavior. With none of these parameters set, entire files are delivered, start to finish, as quickly as possible.
| FIELD | DEFAULT PARAMETER | DESCRIPTION |
|---|---|---|
| Bandwidth Throttling Initial Burst Parameter | ri | This is the name of the query string parameter that indicates to the CDN an initial burst rate to use when delivering a file. This parameter is part of the bandwidth limiting feature that is initiated on a per request basis. Specifies a value in bytes that should run at full speed before an "rs" parameter takes effect. |
| Bandwidth Throttling Sustained Rate Parameter | rs | This is the name of the query string parameter that indicates to the CDN the sustained rate being requested for the delivery of a file. This parameter is part of the bandwidth throttling feature that is initiated on a per request basis. Specifies a value in kilobits per second at which the transfer should run at that rate sustained. This can be used with progressive download delivery to keep the player from getting too far ahead of what the end user is actually viewing. |
Example
Run a progressive download at full speed for 500k, then back the rate off to 10% higher than the encoded rate of 400 kilobit:
http://hwcdn.net/a1b2c3d4/cds/donotchange3.flv?ri=500000&rs=440Throttling via User-Agent
In addition to throttling via URL parameters, an internal configuration policy can be set by the NOC or your Solutions Engineer (SE) that will apply the same behavior based upon a pattern match with the requestor's HTTP User-Agent. Each rule includes a pattern match against the User-Agent from the HTTP request and a pattern match against the requested file's extension.
Example
The pattern below will match all MP3 files and EXE files containing the substring 'dir' that are requested by a User-Agent containing the substring "Mozilla", all JPG and ZIP files requested by a User-Agent containing the substring "IE", and all requests made by User-Agents containing the substring "ios 6":
Mozilla*:*.mp3,*dir*.exe|*IE*:*.jpg,*.zip|*ios 6*:*