sni

Server Name Indication - see RFC3546 section 3.1. If set, the load balancer sends this string as the SNI hostname in the TLS connection to the backend, and requires that this string match a Subject Alternative Name (SAN) in the backend's server certificate. With a Regional Internet NEG backend, if the SNI is specified here, the load balancer uses it regardless of whether the Regional Internet NEG is specified with FQDN or IP address and port.