Virtual circuit - use TCP to communication with server. All domain names used in a single update request must belong to the same DNS zone. A blank line causes the accumulated records to be formated into a single update request and transmitted to the zone's authoritative name servers. Additional records may follow, which are formed into additional, completely independent update requests. For the last request to be transmitted, a blank line must end the input.
Records take one of two general forms.
Prerequisite records specify conditions that must be satisfied before the request will be processed. Update records specify changes to be made to the DNS database. A update request consists of zero or more prerequisites and one or more updates. Each update request is processed atomically - all prerequisites must be satisfied, then all updates will be performed. If data is specified, it must match exactly.