What is an SRV record?

It is a type of resource record supported by the database of the DNS server. It records the simple information about which computer provides the service.

SRV record: It is generally an application set for Microsoft's Active Directory. DNS can be independent from the Active Directory, but the Active Directory must have DNS help to work. To make the Active Directory work properly, the DNS server must supportService Positioning(SRV)Resource RecordThe resource record maps the service name to the name of the server that provides the service. Active Directory customers and domain controllers use SRV resource records to determine the IP addresses of domain controllers.S> xabt: m 

SRV record functions include (based on their groups on the DNS console)
'_ Msdcs. In this group, SRV records are collected based on their statuses. Various statuses include DC, domain call, GC, and PDC. DC and GC are divided by site, so that the ad client can quickly find the local service. "Domain call" is used to support replication. Each DC obtains a guid, which is used when replication is called. The PDC entry contains the SRV record of the DC set as the PDC simulator.
'_ Sites. The site represents a high-speed connection area. After a DC index is created based on the DC's site subordination, the client can check _ sites to find the local service, instead of sending LDAP query requests over the WAN. The standard LDAP query port is 389, and the Global Catalog query uses 3268.
'_ TCP. This group collects all the DC in the DNS region. If the client cannot find their specific site, or any DC with a local SRV record does not respond, you need to find the DC in other parts of the network, you should put these clients in this group.
'_ UDP. Keberos V5 allows the client to use the "No connection" service to obtain the ticket and change the password. This is done through the UDP port corresponding to the TCP port of the same service. Specifically, the ticket exchange uses port 88 of UDP, while the Password Change uses port 464.