What is back-channel in Destination.getBackChannel()?

[iclin <ic...@cisco.com>]

Hi,

I'm trying to implement a customize org.apache.cxf.transport.Destination by
extending AbstractDestination. In the Destination interface there is a
method called getBackChannel() and the description reads like:

"Retreive a back-channel Conduit, which must be policy-compatible with the
current Message and associated Destination. For example compatible Quality
of Protection must be asserted on the back-channel"

I still do not understand what is the purpose of a 'back-channel' and when
it is used to properly implement my Destination.

A more elaborated description will be very helpful.

Thanks.