Màn hình 3,1 hiển thị). Lưu ý rằng các máy chủ DNS đã gửi tin nhắn này là thẩm quyền đối với hồ sơ này (cờ Authoritative được thiết lập để 1) và tin nhắn có chứa tất cả các hồ sơ yêu cầu (cờ Rút gọn được thiết lập là 0). Entries Câu hỏi phần của tin nhắn có chứa các mục câu hỏi ban đầu từ tin nhắn yêu cầu truy vấn Name. | Chapter 15 Domain Name System 325 Monitor display . Note that the DNS server that sent this message is authoritative for the record the Authoritative flag is set to 1 and the message contains all of the requested records the Truncation flag is set to 0 . The Question Entries portion of the message contains the original question entry from the Name Query Request message. The Answer RRs section contains a single answer RR for the IPv4 address which the DNS client can cache for 3600 seconds 60 minutes . Resolving Addresses to Names Resolving addresses to names also known as reverse name resolution occurs when a DNS client or DNS server sends a DNS server a Name Query Request message containing an FQDN corresponding to an IPv4 address in the reverse namespace with instructions to return all PTR RRs. For example the FQDN corresponding to the IPv4 address in the reverse DNS namespace is . An example of this message exchange is Capture 15-02 a Network Monitor trace that is included in the Captures folder on the companion CD-ROM. The following is the DNS Name Query Request message from Capture 15-02 Frame 1 as displayed with Network Monitor Frame Ethernet Etype Internet IP IPv4 Ipv4 Next Protocol UDP Packet ID 13033 Total IP Length 69 Udp SrcPort 53206 DstPort DNS 53 Length 49 - Dns QueryId 0XB75C QUERY Standard query Query for of type PTR on class Internet QueryIdentifier 46940 0xB75C Flags Query Opcode - QUERY Standard query RD Rcode - Success QuestionCount 1 0x1 AnswerCount 0 0x0 NameServerCount 0 0x0 AdditionalCount 0 0x0 - QRecord of type PTR on class Internet QuestionName QuestionType PTR Domain name pointer 12 0xc QuestionClass Internet 1 0x1 In this frame a DNS client is requesting that the DNS server return all PTR RRs for the FQDN . The following is the corresponding DNS Name Query Response message from Capture
