can anybody provide me with the difference between GRE and IPsec or any such topic explaining that......
GRE = Generic Routing Encapsulation is a protocol that has been introduced to provide a way to transport OSI L2 or OSI L3 frames over an IP network: for example to interconnect IPX lans via an IP network, GRE can also carry IPv4 packets in this second case it provide a virtual point-to-point link between two routers that don't need to be directly connected.
GRE support multicast traffic and allows routing protocols to be used over it.
IPSec = is a group of protocols and features that have been introduced to provide security services over the network like authentication, encryption, non-repudiation and so on.
IPSec provides a way to secure and protect traffic between two endpoints and include protocols for negotiation and setup of the communication. IPSec is thought to carry IPv4 unicast packets (no multicast support)
To be noted that the two can be used together because they provide different features and complement each other in this case usually the GRE packet is the payload of IPSec.
For example see the following link:
an introduction to ipsec
Hope to help