List 6-3　リソースレコードの登録を確認するPrerequisiteパケット

3 DNS: 0x63:Dyn Upd PRE records to PC98.active.dsl.local. of type Canonical name
      DNS: Query Identifier = 99 (0x63)
      DNS: DNS Flags = Query, OpCode - Dyn Upd, RCode - No error
		↑“Query”から，メッセージは照会であることがわかる。
		　“OpCode”が“Dyn Upd”であれば，Dynamic DNSパケットであると判断できる
          DNS: 0............... = Request
          DNS: .0101........... = Dynamic Update
		↑2進数の“0101”は，10進数で“5”を表すため，
		　Dynamic DNSパケットであることがわかる
          DNS: .....0.......... = Server not authority for domain
          DNS: ......0......... = Message complete
          DNS: .......0........ = Iterative query desired
          DNS: ........0....... = No recursive queries
          DNS: .........000.... = Reserved
          DNS: ............0000 = No error
      DNS: Zone Count = 1 (0x1)
		↑Dynamic DNSパケットには，必ずZoneセクションが存在する
      DNS: Prerequisite Section Entry Count = 2 (0x2)
		↑Prerequisiteセクションが2つあることを示している。
		　このパケットは，2つのリソースレコードを確認している
      DNS: Update Section Entry Count = 0 (0x0)
		↑Updateセクションは存在しない
      DNS: Additional Records Count = 0 (0x0)
      DNS: Update Zone: active.dsl.local. of type SOA on class INET addr.
          DNS: Update Zone Name: active.dsl.local.
		↑Updateするゾーンが“active.dsl.local”であることを示す
          DNS: Update Zone Type = Start of zone of authority
          DNS: Update Zone Class = Internet address class
      DNS: Prerequisite: PC98.active.dsl.local. of type Canonical name on class Unknown Class(2 records present)
		↑Prerequisiteセクション。2つのレコードが含まれている
          DNS: Resource Record: PC98.active.dsl.local. of type Canonical name on class Unknown Class
              DNS: Resource Name: PC98.active.dsl.local.
		↑確認するリソースレコードの名前
              DNS: Resource Type = Canonical name for alias
		↑“Canonical name for alisas”とは，CNAMEレコードを意味する
              DNS: Resource Class = 0x00FE
              DNS: Time To Live = 0 (0x0)
              DNS: Resource Data Length = 0 (0x0)
          DNS: Resource Record: PC98.active.dsl.local. of type Host Addr on class INET addr.
              DNS: Resource Name: PC98.active.dsl.local.
		↑確認するリソースレコードの名前
              DNS: Resource Type = Host Address
		↑“Host Address”とは，Aレコードを意味する
              DNS: Resource Class = Internet address class
              DNS: Time To Live = 0 (0x0)
              DNS: Resource Data Length = 4 (0x4)
              DNS: IP address = 192.168.1.101

4 DNS: 0x63:Dyn Upd Resp. PRE records to PC98.active.dsl.local. of type Canonical name : RR set that ought to exist, does not exist
      DNS: Query Identifier = 99 (0x63)
      DNS: DNS Flags = Response, OpCode - Dyn Upd, RCode - RR set that ought to exist, does not exist
		↑“Response”から応答メッセージであることがわかる。
		　“OpCode”が“Dyn Upd”であれば，Dynamic DNSパケットであると判断できる
          DNS: 1............... = Response
          DNS: .0101........... = Dynamic Update
          DNS: .....0.......... = Server not authority for domain
          DNS: ......0......... = Message complete
          DNS: .......0........ = Iterative query desired
          DNS: ........0....... = No recursive queries
          DNS: .........000.... = Reserved
          DNS: ............1000 = RR set that ought to exist, does not exist
		↑2進数の“1000”は10進数で“8”を表すので，
		　「リソースレコードセットは存在していない」という回答であることがわかる
      DNS: Zone Count = 1 (0x1)
      DNS: Prerequisite Section Entry Count = 2 (0x2)
      DNS: Update Section Entry Count = 0 (0x0)
      DNS: Additional Records Count = 0 (0x0)
      DNS: Update Zone: active.dsl.local. of type SOA on class INET addr.
          DNS: Update Zone Name: active.dsl.local.
          DNS: Update Zone Type = Start of zone of authority
          DNS: Update Zone Class = Internet address class
      DNS: Prerequisite: PC98.active.dsl.local. of type Canonical name on class Unknown Class(2 records present)
          DNS: Resource Record: PC98.active.dsl.local. of type Canonical name on class Unknown Class
              DNS: Resource Name: PC98.active.dsl.local.
              DNS: Resource Type = Canonical name for alias
              DNS: Resource Class = 0x00FE
              DNS: Time To Live = 0 (0x0)
              DNS: Resource Data Length = 0 (0x0)
          DNS: Resource Record: PC98.active.dsl.local. of type Host Addr on class INET addr.
              DNS: Resource Name: PC98.active.dsl.local.
              DNS: Resource Type = Host Address
              DNS: Resource Class = Internet address class
              DNS: Time To Live = 0 (0x0)
              DNS: Resource Data Length = 4 (0x4)
              DNS: IP address = 192.168.1.101