SRV

networking

Stands for: Service record

A DNS record that advertises the host and port for a specific service.

A Service record (RFC 2782) tells clients where a service lives - hostname, port, priority, weight - used by protocols like SIP and by Active Directory for service discovery.

An SRV record says where a specific service lives, rather than where a host lives, and it carries priority, weight, port and target in one answer. That combination lets a client discover both the address and the port without either being hardcoded, which is exactly what protocols with movable endpoints need.

The naming convention is what makes it work and what makes it look strange. The record name encodes the service and protocol as underscore-prefixed labels before the domain, so a client that knows which service it wants can construct the query without configuration. Active Directory depends on this heavily: domain controllers advertise themselves through SRV records, and a client finds its domain by asking DNS rather than by being told.

Priority and weight together give a fuller failover and balancing model than MX offers: lower priority wins outright, and among equal priorities the weight distributes load proportionally. The catch is that adoption in web protocols never happened, because browsers do not consult SRV, which is why HTTPS service discovery took a different route entirely through the newer HTTPS and SVCB record types.

Also known as: srv, SRV record

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