12. AUTHORITY SECTION(1of13)
NAME 1 .
TYPE 2 NS
CLASS 2 IN
TTL 4 (snip)TTL 4 (snip)
RDLENGTH 2 (snip)
RDATA 20 a.root-serverse.net.
total 31
31 x 13 = 403[Byte]
13.
14. NAME 20 a.root-serverse.net.
TYPE 2 NS
CLASS 2 IN
TTL 4 (snip)
ADDITIONAL SECTION(1of13)
TTL 4 (snip)
RDLENGTH 2 (snip)
RDATA 4 198.41.0.4
total 34
34 x 13 = 442[Byte]
17. RFC1035 4.1.4. Message compression
The pointer takes the form of a two octet sequence:
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| 1 1| OFFSET |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
The first two bits are ones. This allows a pointer to be distinguished
from a label, since the label must begin with two zero bits becausefrom a label, since the label must begin with two zero bits because
labels are restricted to 63 octets or less. (The 10 and 01 combinations
are reserved for future use.) The OFFSET field specifies an offset from
the start of the message (i.e., the first octet of the ID field in the
domain header). A zero offset specifies the first byte of the ID field,
etc.
18. The pointer takes the form of a two octet sequence:
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| 1 1| OFFSET |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
最初の 2bit が '11' (10 と 01 は予約済)
RFC1035 4.1.4. Message compression
最初の 2bit が '11' (10 と 01 は予約済)
OFFSET はメッセージの先頭からのオフセット
ラベルは 63 octets 以下なので
圧縮されていないラベルの上位 2bitは ‘00’