EVB-PIC24 WIZnet, EVB-PIC24 Datasheet - Page 86

• Manufacturer Part Number: EVB-PIC24
• Description: Development Boards & Kits - PIC / DSPIC W3150A+EVAL BOARD BASED ON PIC24
• Manufacturer: WIZnet

Specifications of EVB-PIC24

• Rohs: yes
• Product: Development Kits
• Interface Type: RS-232
• Data Bus Width: 16 bit
• Dimensions: 50 mm x 40 mm

Header Section of DNS Message holds Type of Message, DNS Query Type, and count information on
variable length section.
In <Fig 3.35: Header Section Format>, QR Field gets 0 when DNS Message is a request from Resolver to
Name Server and gets 1 when it‟s from Name Server to Resolver. Opcode Field gets 0 when it queries
Domain Name as IP Address and gets 2 when it queries Name Server status.
QDCOUNT, ANCOUNT, NSCOUNT, and ARCOUNT Field, count information for variable length, represent
Block Count that is composed of Question, Answer, Authority, and Additional Section. Question Section is
made of Block of <Fig 3.36: Question Section Format> Recode Resources(RRs) which are Format. Answer,
Authority, and Additional Sections are composed of Block of <Fig 3.37>.
For example, if QDCOUNT is 1, ANCOUNT is 10, NSCOUNT is 10, and ARCOUNT is 10 then Question
Section is composed of Block 1 of <Fig 3.36: Question Section Format> and Answer, Authority, and
Additional Section are composed of 10 Blocks in <Fig 3.37>.
NAME of <Fig 3.37>, QNAME Filed of <Fig 3.36> and RDDATA Field also get variable lengths. QNAME and
NAME are variable length fields which are composed of <Fig 3.36> Format and they process each field.
RDDATA, variable length field, processes using the data length of RDLENGTH Field.
For further details, refer to RFC1034 and RFC1035
DNS Message is operated by Data Type defined in <Table 3-38>. Refer to “inet/dns.h”
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<Fig 3.37: Recode Resources Format>
RDLENGTH
RDDATA
CLASS
NAME
TYPE
TTL
15
Variable
Variable
Length
Length
2 Byte
2 Byte
4 Byte
2 Byte
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