If you set up your own BSMTP routing without using the command
procedure bitnet_domains_driver.com, you will find that
the number of channels needed rapidly gets out of hand. The
multigate keyword allows systems that accept BSMTP format
messages with similar characteristics to be serviced by a single
channel. There is still some overhead because each mailer needs a
separate entry in the channel block, but the overhead is much less than
when separate channels are used.
In order to use the multigate keyword, systems that accept
BSMTP format messages must be grouped according to their use of the
daemon and user keywords. Only mailers with
identical daemon and user specifications can
be grouped on a single channel.
For example, suppose that the mailer gateways for the .ARIZONA.EDU and .UU.SE subdomains as well as the mailer for the system YMIR.BITNET share the same characteristics --- they all accept BSMTP format messages sent to the special user tag SMTPUSER from the special user tag SMTPUSER. They could be grouped in a single channel as follows:
.ARIZONA.EDU $U%$H$D@ARIZONA.BITNET .UU.SE $U%$H$D@SEMAX51.BITNET YMIR.BITNET $U%$D@BIT-GATE-1 _gate1 smtp daemon smtpuser user smtpuser multigate single_sys BIT-GATE-1 ARIZONA.BITNET ARIZONA.BITNET SEMAX51.BITNET SEMAX51.BITNETThe presence of the
single_sys keyword is required -- a
separate copy of each message is needed for each of the gateways.
Using this technique can substantially reduce the size of the PMDF
configuration file. However, determining which gateways support the
necessary RFC 822 addressing conventions is not trivial, nor is the
task of organizing the various gateways in the proper manner. As a
result, the use of multigate is best left to automated
procedures like bitnet_domains_driver.com.