Fundamentally, proxy servers get SIP messages and redirect them to the next SIP server in the network. Proxy servers are able to provide operations like authentication, authorization, network access control, routing, reliable request transmission, and security. (ii) Redirect server: Gives the client with information regarding the nest hop or hops which the message must take and subsequently the client contacts the next hop server and UAS directly. (iii) Registrar Server: Processes requests taking from UACs for registration of their present location. Registrar servers are frequently are co-situated with a redirect or proxy server. (Overview of the Session Initiation Protocol)

Functioning of the SIP:

SIP is an easy, ASCII-based protocol that utilizes requests and responses to set up communication among the different components in the network and to finally set up a conference among two of more terminal points. Users in a SIP network are recognized by a unique SIP address....
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