Handbook:Advanced Server Configuration:Modem Priorities

The HylaFAX scheduler process assigns modems to outbound jobs based on three criteria: the modem is considered ready for use, the modem is a member of the requested modem class (if any was specified), and the modem's capabilities support the requirements of the job (e.g. transmission of high-resolution 2D-encoded data). When multiple modems are present on a server machine it is also possible to force an order to the set of modems that are considered for allocation by assigning each modem a priority. This can be used, for example, to reduce the likelihood of assigning modems that are heavily used for inbound calls; e.g. near the front of a hunt group.

Modem priorities are specified using the ModemPriority configuration parameter. Priority values are integer numbers in the range 0-255 with lower values meaning higher priority.

Modem priorities are passed to the HylaFAX scheduler by the faxgetty processes or with the faxmodem program. Priorities can be dynamically changed by using the faxconfig program to send a new priority to a faxgetty process (who in turn will notify the scheduler), e.g.

hyla# faxconfig -m ttyf2 ModemPriority 32

or with the -u option to the faxmodem program when operating in a send-only environment. The ability to dynamically alter the priority of modems means it is easy to reconfigure modem usage based on time-of-day and traffic patterns.