Scalability is an important aspect in the Web 2.0 era where services need to be massively scalable. Building massive scaled services without failure and complexity is a challenging task. Meanwhile, in practice, communication services consist of two layers: signaling layer and media layer. The signaling architecture should be scalable when a number of users and calls keep on increasing. However, scalability is not well-defined for the signaling architecture and is considered as an afterthought. The main goal of this paper is to characterize the scalability aspect for the signaling architecture and present an analytical comparison of the existing signaling architectures - IP Multimedia Subsystem (IMS)/ Session Initiation Protocol (SIP), Peer-to-Peer (P2P) SIP, along with our new signaling architecture, My Own Communication Service Provider (MOCSP).