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Bandwidth Throttling - Overview

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The Bandwidth Throttling feature makes it possible for you to police the consumption of bandwidth used by MDaemon. You can control the rate at which sessions or services progress — you can set different rates for each of MDaemon's major services on a per-domain basis, including the Default and Extra Domains and Domain Gateways. You can also set limits on local connections by selecting "Local traffic" from a drop down box. This will allow you to create special bandwidth settings that will take effect if the connection is either from or to a local IP address or domain name.

Bandwidth Throttling can be applied on either a per-session or per-service basis. When using the per-session mode, each session will be independently throttled to the associated rate. Thus multiple sessions of the same service type occurring simultaneously could exceed a service's configured value. When configured to throttle bandwidth on a per-service basis, MDaemon will monitor the combined use of all sessions of the same service type and allocate equal fractions of the total bandwidth to each. Multiple sessions will then share the configured maximum bandwidth equally. This will allow you to set a limit on an entire service.

When extending Bandwidth Throttling to a Domain Gateway, it must be handled a bit differently than a normal domain since a Domain Gateway doesn't have a specific IP address associated with it. MDaemon must use the value passed in the RCPT command to determine whether or not an inbound SMTP session is bound for the gateway. If it is, then inbound SMTP bandwidth throttling will be applied. Due to the limitations of SMTP, if even one recipient of a multiple recipient message is destined for a Domain Gateway then the entire session will be throttled.

The Bandwidth Throttling system is calibrated in kilobytes per second (KB/s). A value of "0" means that no limit will be applied to the speed at which a session (or service) progresses, thus it will use the maximum amount of available bandwidth. A value of "10", for example, will force MDaemon to deliberately throttle back on the speed of transmission so as to remain at or slightly above 10 KB/s.

Bursts of activity at the beginning of a session can and will exceed the fixed limits. Throttling takes place and becomes more defined as the session progresses.