问题：

[多选] Which of the following describe the process identifier that is used to run OSPF on a router? (Choose two.)（）

A . It is locally significant.
B . It is globally significant.
C . It is needed to identify a unique instance of an OSPF database.
D . It is an optional parameter required only if multiple OSPF processes are running on the router.
E . All routers in the same OSPF area must have the same process ID if they are to exchange routing information.