Embodiments herein disclose methods and systems for optimizing resources in an IP multimedia subsystem (IMS) network, wherein a method includes receiving capabilities of contacts present in the contact book in response to a request sent by an OPTIONS applications server (AS) to the contacts present in the contact book. Further, the method includes aggregating the capabilities of the contacts present in the contact book. Further, the method includes transmitting the aggregated capabilities of the contacts present in the contact book to the UE through a PNT server. Further, the embodiments include fetching updated capabilities of user equipment (UE) by the presence AS through the PNT server. Further, the embodiments include receiving a metadata in response to the received service request using push notifications through the PNT server. Further, the embodiments include registering the UE with the IMS network, if the IMS client is capable of in-call service.