In which two ways is GRE used in GGSN? (Choose two.)
A. to transport the subscriber traffic between MS and GGSN
B. to transport AAA packets between GGSN and the service provider RADIUS server
C. to transport AAA packets between GGSN and the corporate RADIUS server
D. to transport the enterprise subscriber packets to the corporate gateway
E. to transport the enterprise subscriber packets to the Internet
