replication and availability

hi everyone,

having read the online doc, and a book, i can't find precisely what i'm
looking for, but it's maybe normal.... here it is....
I have a distant postgres database used to store networking info. This
database "may" be unavailable, so i need to have another postgres
database somewhere else (it theory, i should know where...). What can i
do to tell somewhere/postgres to be exactly the same as
elsewhere/postgres... Let's imagine that somewhere/postgres is my
primary database, shall i have to use triggers in order to insert/delete
datas in elsewhere/postgres at the same time as somewhere/postgres ? or
should i have to dump somewhere/postgres regularly and update
elsewhere/postgres with this dump (cron job ?)...

Isn't there a something in postgres to say elsewhere should be the
database image of somewhere/postgres ?

regards

stephane