Which DNS record type is used for service discovery and indicates protocol and port for SIP?

Which DNS record type is used for service discovery and indicates protocol and port for SIP?

• A. A record
• B. MX record
• C. CNAME record
• D. SRV records (e.g., _sip._tcp / _sips._tcp)

Answer: (D)

DNS SRV records are used for service discovery of SIP because they encode where a service lives, how to reach it, and over which transport. For SIP you’ll see names like _sip._tcp.example.com or _sips._tcp.example.com. An SRV record provides the port and the target host, along with priority and weight to help clients choose among multiple servers. This lets a SIP client locate the correct SIP service endpoint and know exactly which port to contact, and whether to prefer one server over another or balance traffic. Other records don’t carry this service-specific information. An A record simply maps a domain to an IP address without any port or transport details. MX records are for directing email, not SIP signaling. CNAME records act as an alias to another name but don’t themselves specify service endpoints or ports for a protocol like SIP.

DNS SRV records are used for service discovery of SIP because they encode where a service lives, how to reach it, and over which transport. For SIP you’ll see names like _sip._tcp.example.com or _sips._tcp.example.com. An SRV record provides the port and the target host, along with priority and weight to help clients choose among multiple servers. This lets a SIP client locate the correct SIP service endpoint and know exactly which port to contact, and whether to prefer one server over another or balance traffic.

Other records don’t carry this service-specific information. An A record simply maps a domain to an IP address without any port or transport details. MX records are for directing email, not SIP signaling. CNAME records act as an alias to another name but don’t themselves specify service endpoints or ports for a protocol like SIP.