How does the SIP registrar server maintain the registered user's information in its database?
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A. B. C. D. E.D.
The SIP registrar server is responsible for registering users and maintaining their information in its database. When a User Agent (UA) wants to register with the registrar server, it sends a SIP REGISTER message containing its contact information. The registrar server then creates a record in its database to store this information for future reference.
The process of maintaining the registered user's information in the registrar server's database involves creating various types of associations between different elements of the SIP protocol.
Option A: DNS Server The registrar server does not maintain registered user's information by querying a DNS server. DNS (Domain Name System) is used to translate domain names into IP addresses, but it is not used for registration or authentication purposes.
Option B: ENUM Server The registrar server also does not maintain registered user's information by querying an ENUM server. ENUM (Telephone Number Mapping) is used to map telephone numbers to SIP URIs, but it is not used for registration or authentication purposes.
Option C: Registration Cache Entry When a UA registers with the registrar server, the server creates a registration cache entry, which is an association between a layer 3 IP address and the UA's Via address. This cache entry is used to route incoming SIP messages to the correct UA.
Option D: Location Record The registrar server also creates a location record, which is an association between the Call-ID and the UA's Contact address. This location record is used to route incoming SIP messages to the correct UA.
Option E: Binding Finally, the registrar server creates a binding, which is an association between a globally unique SIP URI and the UA's Contact address. This binding is used to route incoming SIP messages to the correct UA.
In summary, the SIP registrar server maintains the registered user's information in its database by creating various types of associations between different elements of the SIP protocol, such as registration cache entries, location records, and bindings.