Bit
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... case-insensitive manner, assuming an ASCII character set, and a high
order zero bit. This means that you are free to create a node with
...
... which is an encoded 16 bit value that specifies the type
of the resource in this resource record. Types refer to
...
... which is an encoded 16 bit value which identifies a
protocol family or instance of a protocol. ...
... time to live of the RR. This field is a 32
bit integer in units of seconds, an is primarily used by
resolvers when they cache ...
... The MX RRs have an RDATA section which consists of a 16 bit number
followed by a domain name. The address ...
...
The most important field in the header is a four bit field called an
opcode which separates different queries. Of the possible 16 values,
...
... query" to mean standard query unless otherwise specified. The
QTYPE and QCLASS fields are each 16 bits long, and are a superset of
defined types and classes.
...
... name server agree to its use. The agreement is negotiated through
the use of two bits in query and response messages:
...
... The recursion available, or RA bit, is set or cleared by a
name server in all responses. The bit ...
... bit, is set or cleared by a
name server in all responses. The bit is true if the name
server is willing to provide recursive service for the client ...
... bit called recursion desired or RD. This
bit specifies specifies whether the requester wants recursive
service for this query ...
... service is available and
requested via the RD bit in the query, go to step 5,
otherwise step 2.
...
... limit on how fast a zone can be updated, basically that old copies must
die out before the serial number covers half of its 32 bit range. In
practice, the only concern is that the compare operation deals properly
...
... practice, the only concern is that the compare operation deals properly
with comparisons around the boundary between the most positive and most
negative 32 bit numbers.
...
... servers, or may have the requested information in a local cache, the
amount of time that a resolver will take to complete can vary quite a
bit, from milliseconds to several seconds.
...
... based function. Given a character string, the caller wants
one or more 32 bit IP addresses. Under the DNS, it
...
...
This function will often follow the form of previous
functions. Given a 32 bit IP address, the caller wants a
...
... header of the query, except
that the RESPONSE bit is set, indicating that this message is a
response, not a query, and the Authoritative Answer (AA ...
... response, not a query, and the Authoritative Answer (AA) bit is set
indicating that the address RRs ...
... query is the AA and
RESPONSE bits in the header. The interpretation of this response is
that the server is authoritative for the name, and the name exists, but
...
...
Note that the AA bit in the header guarantees that the data matching
QNAME is authoritative, but does not say anything about whether the data
...