The shipping server makes one attempt to transmit a packet to another
host. If the packet cannot be transmitted (for example, because the receiving
host is unavailable), the shipping server generates an error message and log
file entry and exits.
You can set up a retry scheme to control its frequency:
- After successful transmission of a packet, the shipping server deletes
the packet and its shipping order. After a failure, the packet and shipping
order remain in the storage bay.
- shipping_server –poll transmits all packets it finds in
one or more storage bays. Thus, any packets that remain after a transmission
failure are sent (if possible) by the next invocation of shipping_server –poll.
Attempts
to transmit an undelivered packet can continue indefinitely, through repeated
invocations of the
shipping_server command. However, you usually
want to fix problems with failed transmissions instead of letting the attempts
continue. Accordingly, each shipping order can include an expiration date-time,
specified with one of the following:
- The command option –expire
- (Linux® and
the UNIX® system)
An EXPIRATION entry in the shipping.conf file on the sending
host
- (Windows®)
A Packet Expiration value in the MultiSite Control
Panel on the sending host
By default, shipping orders expire 14 days after they are created.
When the shipping server encounters a shipping order that has expired,
it does not attempt to transmit the corresponding packet to its destination.
Instead, it does the following:
- It modifies the shipping order to return the packet to the original sending
host, where it is placed in a return bay.
- It sends an electronic mail message to one or more addresses on the original
sending host. (Another message is sent when the returned packet arrives at
the original sending host.)
Note: If a packet is delivered through a Windows host
on which electronic mail notification is not enabled, a failure on that Windows host
means that no notification message is sent by electronic mail. Instead, a
message is written to the event log; this message contains a request that
the appropriate users be informed of the failure. For information about enabling
electronic mail notification, see the MultiSite Control Panel reference
page.
The return trip may involve multiple hops.
During such a trip, a packet is placed in the return bay of each intermediate
host. Each hop is handled by shipping_server –poll, which
processes a host’s return bay in addition to its storage bays. The expiration
time for a packet’s return trip is 14 days; a packet that cannot be returned
in that interval is deleted.