11. DNS(Domain Name Service)


  ¾Õ¿¡¼­ ó·³, ¸¹Àº NS(Name Server)µé°£ÀÇ Çù·Â¿¡ ÀÇÇؼ­ À̸§µéÀÌ °ü¸®µÈ´Ù. µû¶ó¼­, »õ·Î¿î µµ¸ÞÀÎ ¸íÀ» ºÎ¿©¹ÞÀ¸·Á¸é, ÀÌ·¯ÇÑ Ã¼°è¿¡ µî·ÏÀ» Çؾ߸¸ ÇÑ´Ù.

  ±¹³»¿¡ ÀÌ·¯ÇÑ DNS µî·ÏÀ» ó¸®ÇØÁÖ´Â ¾÷ü·Î, °¡ºñ¾Æ, ÈÄÀÌÁî, RGNames, µµ·¹Áö °°Àº ¾÷üµéÀÌ ÀÖÀ¸¸ç, °Ë»ö»çÀÌÆ®¿¡¼­ "µµ¸ÞÀεî·Ï"À¸·Î ãÀ¸¸é µÈ´Ù. ºñ¿ëÀº 2,3¸¸¿ø Á¤µµÀε¥, ¾÷ü¿¡ µû¶ó¼­ µî·Ï°¡´ÉÇÑ µµ¸ÞÀÎ ¿¹¸¦ µé¸é, *.com, *.net¸¸ µÇ°Å³ª, *.co.kr¸¸ µÇ´Â °æ¿ìµµ ÀÖ´Ù.

  ¾ÕÀÇ ±×¸²Ã³·³ ´Ù¼öÀÇ NS°¡ Âü¿©Çϱ⠶§¹®¿¡ ¸¸¾à ¾û¶×ÇÑ µµ¸ÞÀÎ ¸íÀ¸·Î »çÀÌƲ °Ë»öÇÏ°Ô µÇ¸é, ¿©·¯ NSµé¿¡°Ô ¹°¾îº¸´Â ½Ã°£ÀÌ °É¸®±â ¶§¹®¿¡ Àû°Ô´Â 30ÃÊ¿¡¼­ ¸¹°Ô´Â 4ºÐ±îÁö ¼Ò¿äµÈ ÀÌÈÄ¿¡¾ß ¿¡·¯ ¸Þ½ÃÁö¸¦ ¸¸³ª°Ô µÈ´Ù. ºê¶ó¿ìÀú·Î µµ¸ÞÀθíÀ» À߸øÄ£ °æ¿ì ÇÑÂüÈÄ¿¡ ¿¡·¯ ¸Þ½ÃÁö°¡ ³ªÅ¸³ª´Â ÀÌÀ¯°¡ ¹Ù·Î ÀÌ·¯ÇÑ ¿øÀÎ ¶§¹®ÀÌ´Ù.

  DNS ¸Þ½ÃÁö´Â TCPÀ§¿¡ ´ÙÀ½°ú °°Àº ÇüÅ·Π±¸¼ºµÇ¾îÁø´Ù. ÀÌ Áß ÀϺδ °æ¿ì¿¡ µû¶ó¼­ ºñ¾îÀÖÀ» ¼ö ÀÖ´Ù.

    +---------------------+
    |        Header       |
    +---------------------+
    |       Question      | the question for the name server
    +---------------------+
    |        Answer       | RRs answering the question
    +---------------------+
    |      Authority      | RRs pointing toward an authority
    +---------------------+
    |      Additional     | RRs holding additional information
    +---------------------+
  ´ÙÀ½Àº Çì´õºÎºÐ¿¡ ´ëÇÑ Çü½ÄÀÌ´Ù.
                                    1  1  1  1  1  1
      0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                      ID                       |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |QR|   Opcode  |AA|TC|RD|RA|   Z    |   RCODE   |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                    QDCOUNT                    |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                    ANCOUNT                    |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                    NSCOUNT                    |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                    ARCOUNT                    |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
FieldBitsDescription
ID16DNSÁúÀÇ/ÀÀ´äÀ» ¸ÂÃß±â À§ÇÑ Sequence/KeyÁ¤µµ·Î º¸¸é µÈ´Ù. Áï, 2 Byte ¹üÀ§ÀÇ ¼ýÀÚ·Î Áõ°¡½ÃÄÑ °¡¸é¼­ »ç¿ëÇÏ¸é µÈ´Ù.
QR1ÁúÀÇÀÎÁö ÀÀ´äÀÎÁö ¿ë Ç÷¡±× ( 0:ÁúÀÇ, 1:ÀÀ´ä )
Opcode4QueryÀÇ Á¾·ù·Î ´ë°³ 0À» »ç¿ëÇÑ´Ù.

- 0 : a standard query (QUERY)
- 1 : an inverse query (IQUERY)
- 2 : a server status request (STATUS)
- 3 ~ 15 : reserved for future use
AA1Authoritative Answer (ÀÀ´ä ½Ã¸¸ ¼³Á¤µÇ¾î¿È)
°ø½Ä³×ÀÓ¼­¹öÀÇ ÀÀ´ä¿©ºÎ Ç÷¡±×( 0:ºñ°ø½Ä, 1:°ø½Ä)
TC1TrunCation(ÀÀ´ä ½Ã¸¸ ¼³Á¤µÇ¾î¿È)
ÀÀ´äÀÇ °æ¿ì Á¤ÇØÁø »çÀÌÁî(UDPÀÇ Á¦ÇÑÀº 512ÀÓ)¸¦ ÃÊ°úÇؼ­ Àß·È´ÂÁö ¿©ºÎ¸¦ ³ªÅ¸³»´Â Ç÷¡±× ( 0:Á¤»ó , 1:À߸² )
RD1Recursion DesiredÁúÀǽÿ¡ Àç±ÍÀûÀÎ ÁúÀÇ ÇÊ¿ä ¿©ºÎ
±âº»Àº ÇÊ¿ä ( 0:ºÒÇÊ¿ä,1:ÇÊ¿ä )
RA1Recursion Available(ÀÀ´ä½Ã¿¡¸¸ ¼³Á¤µÇ¾î¿È)
ÀÀ´äÇÑ ³×ÀÓ¼­¹ö°¡ Àç±ÍÁúÀÇ(RD)¸¦ ÇÒ ¼ö ÀÖ´ÂÁö ¿©ºÎ( 0:¸øÇÔ,1:ÇÔ )
Z3 ³ªÁßÀ» À§ÇØ ¿¹¾àµÈ ºÎºÐ. Ç×»ó 0À¸·Î ¼³Á¤ÇØ¾ß ÇÔ.
RCODE4Response code(ÀÀ´äÄÚµå)
Value³»¿ë¼³¸í
0Success¼º°ø
1Format ErrorQuery°¡ À߸øµÈ °æ¿ì
2Server Failure³×ÀÓ¼­¹ö ÀÚüÀÇ ¹®Á¦·Î ½ÇÆÐ
3Name ErrorÇØ´ç ³×ÀÓÀÌ Á¸ÀçÇÏÁö ¾ÊÀ½
4Not Implemented³×ÀÓ¼­¹ö°¡ Query¸¦ Áö¿ø¸øÇÔ
5RefusedÁ¤Ã¥ÀûÀÎ ÀÌÀ¯·Î Query¸¦ °ÅÀýÇÔ
6~15Reserved³ªÁßÀ» À§Çؼ­ ¿¹¾àµÊ
QDCount16Question SectionÀÇ °³¼ö( unsigned 16 bit integer)
ANCount16Answer Section¿¡ ÀÖ´Â resource recordÀÇ °³¼ö(ÀÀ´ä ½Ã¸¸ ¼³Á¤µÊ)( unsigned 16 bit integer)
NSCount16Authorities Section¿¡ ÀÖ´Â server resource recordÀÇ °³¼ö(ÀÀ´ä ½Ã¸¸ ¼³Á¤µÊ) ( unsigned 16 bit integer)
ARCount16Additional Information Section¿¡ ÀÖ´Â resource recordÀÇ °³¼ö(ÀÀ´ä ½Ã¸¸ ¼³Á¤µÊ) ( unsigned 16 bit integer)


  * ÁúÀǸ¦ Àü¼ÛÇÒ ¶§ QDCOUNT°¡ 1°³ ÀÖ°í, ³ª¸ÓÁö COUNTµéÀº ´ë°³ 0À¸·Î ¼³Á¤µÇ¾î Àü¼ÛµÈ´Ù.

- Last Update : 2003.04.25 by Deadfire(http://www.deadfire.net)

TCP/IP °­ÁÂ
Starting
NIC
Çãºê
Cable
ÀÌ´õ³Ý
LAN
¶ó¿ìÅÍ
IP
ICMP
TCP / UDP
TCP
UDP
DNS
Ending

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