SVCB Record

In one line

The SVCB (Service Binding) record is the generalized form of the HTTPS record. It allows any service to publish alternative endpoints, connection parameters, and hints. HTTPS is a SVCB record restricted to the https scheme. SVCB enables service aliasing (like CNAME but for service parameters) and lets clients learn connection details before attempting a connection.

Description

SVCB (RFC 9460) introduces two RR types: SVCB (general) and HTTPS (HTTPS-specific). A SVCB record in AliasMode (priority 0) redirects to another name for all parameters. In ServiceMode (priority >= 1), it provides inline parameters: ALPN tokens, port, ECH config, IP hints. Multiple SVCB records can be published for failover and load distribution. The client tries records in priority order.

Examples

_https._tcp.example.com. IN SVCB 0 service.example.net.

_https._tcp.example.com. IN SVCB 1 . port=8443 alpn="h2"

dig _https._tcp.example.com SVCB

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