Which DNS record type defines the hostname and port for services, enabling clients to locate specific services within a domain?

Which DNS record type defines the hostname and port for services, enabling clients to locate specific services within a domain?

• A. A
• B. MX
• C. NS
• D. SRV

Answer: (D)

Service discovery in DNS relies on SRV records. These records define the hostname and port for a given service within a domain, allowing clients to locate the exact server and port to contact. An SRV record includes the service identifier (such as _sip._tcp or _xmpp-client._tcp), the domain, and numeric values for priority, weight, port, and the target host. This setup supports selecting among multiple servers and ports to reach the right service, with load balancing and failover handled by priority and weight. This is different from others: A records map a name to an IP address, MX records specify which host handles mail for the domain, and NS records point to the domain’s authoritative name servers. So for locating a specific service and its port within a domain, the SRV record is the appropriate choice. Example: _sip._tcp.example.com. IN SRV 10 60 5060 sipserver.example.com.

Service discovery in DNS relies on SRV records. These records define the hostname and port for a given service within a domain, allowing clients to locate the exact server and port to contact. An SRV record includes the service identifier (such as _sip._tcp or _xmpp-client._tcp), the domain, and numeric values for priority, weight, port, and the target host. This setup supports selecting among multiple servers and ports to reach the right service, with load balancing and failover handled by priority and weight.

This is different from others: A records map a name to an IP address, MX records specify which host handles mail for the domain, and NS records point to the domain’s authoritative name servers. So for locating a specific service and its port within a domain, the SRV record is the appropriate choice.

Example: _sip._tcp.example.com. IN SRV 10 60 5060 sipserver.example.com.