Does anybody have a clue what the srcAlternatives and destAlternatives fields in the ARQ are supposed to be?

I did a search on H.225.0 and H.323 and the only occurence of it is in H.225.0 where the fields are described to be "a sequence of prioritized source endpoint alternatives for srcInfo, srcCallSignalAddress, or rasAddress" and "a sequence of prioritized destination endpoint alternatives for destinationInfo or destCallSignalAddress".