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Learning TCP/IP

BY: Nasser-Desperado

TCP/IP ‫ﻣﻮﺿﻮع : ﺁﻣﻮزش‬ Desperado_Nasser@yahoo.com ‫ﺗﺎﻟﻴﻒ و ﮔﺮدﺁورﯼ : ﻧﺎﺻﺮ ﺑﺮﻗﻴﺎن‬ www.nasser-desperado.persiangig.com : ‫ﺳﺎﻳﺖ‬ 1383/6/6 : ‫ﺗﺎرﻳﺦ ﻧﮕﺎرش‬ 1385/9/10 : ‫ﺗﺎرﻳﺦ اﻧﺘﺸﺎر‬

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‫‪Learning TCP/IP‬‬

‫‪BY: Nasser-Desperado‬‬

‫ﻓﻬﺮﺳﺖ‬
‫ﻧﺤﻮۀ ﺷﺒﮑﻪ ﺑﻨﺪﯼ ﺑﺎ ‪: TCP/IP‬‬
‫ﻣﺪل ﻣﺮﺟﻊ ‪ OSI‬وﻻﻳﻪ ﺑﻨﺪﯼ ﭘﺮوﺗﮑﻞ‬ ‫ﻣﺪل ﻣﺮﺟﻊ ‪ OSI‬از هﻔﺖ ﻻﻳﮥ زﻳﺮ ﺗﺸﮑﻴﻞ ﻣﯽ ﺷﻮﻧﺪ‬ ‫‪ TCP/IP‬ﭼﮕﻮﻧﻪ ﺑﺮاﯼ اﻧﺘﻘﺎل دادﻩ هﺎ ﺑﺎ ﺳﻴﺴﺘﻢ اﺳﺘﻔﺎدﻩ ﻣﯽ ﺷﻮﻧﺪ؟‬ ‫‪TCP/IP‬‬ ‫ﭘﺮوﺗﮑﻞ ﮐﻨﺘﺮل اﻧﺘﻘﺎل ‪TCP‬‬ ‫ﺷﻤﺎرﻩ دروازﻩ هﺎﯼ ‪TCP‬‬ ‫ﺑﻴﺘﻬﺎﯼ ﮐﻨﺘﺮل ‪، TCP‬اﺗﺼﺎل ﺳﻪ راهﻪ و ﺷﻤﺎرﻩ ﻣﺮاﺣﻞ ﮐﺎر‬ ‫دﻳﮕﺮ زﻣﻴﻨﻪ هﺎﯼ ﻋﻨﻮان‪TCP‬‬ ‫ﭘﺮوﺗﮑﻞ )‪User Datagram Protocol (UDP‬‬ ‫ﺁﻳﺎ ‪ UDP‬اﻳﻤﻨﯽ ﮐﻤﺘﺮﯼ از ‪ TCP‬دارد؟‬ ‫ﭘﺮوﺗﮑﻞ ‪ IP‬و ﭘﺮوﺗﮑﻞ ﭘﻴﻐﺎم ﮐﻨﺘﺮل اﻳﻨﺘﺮﻧﺖ )‪(ICMP‬‬ ‫ﺷﺒﮑﻪ هﺎﯼ ﻧﺎﺣﻴﻪ ﻣﺤﻠﯽ و ﻣﺴﻴﺮﻳﺎب هﺎ‬ ‫ﺁدرﺳﻬﺎﯼ ‪IP‬‬ ‫ﻧﺖ ﻣﺴﮑﻬﺎ‬ ‫ﺗﻘﺴﻴﻢ ﺑﻨﺪﯼ ﺑﺴﺘﻪ ﻧﺮم اﻓﺰارﯼ در ‪ IP‬ﺑﻪ ﺻﻮرت ﻗﻄﻌﺎت ﻣﺴﺎوﯼ‬ ‫اﺟﺰاﯼ دﻳﮕﺮ ﻋﻨﻮان ‪IP‬‬ ‫اﻳﻤﻨﯽ در ‪ IP‬ﻗﺪﻳﻤﯽ‬ ‫‪ICMP‬‬

‫ﻋﻨﺎوﻳﻦ دﻳﮕﺮدرﺳﻄﺢ ﺷﺒﮑﻪ‬
‫ﺗﻌﻴﻴﻦ ﻣﺴﻴﺮ ﺑﺴﺘﻪ هﺎ‬ ‫ﺗﻔﺴﻴﺮ ﺁدرس ﺷﺒﮑﻪ‬ ‫دﻳﻮارﻩ هﺎﯼ ﺁﺗﺶ: ﻣﺎﻣﻮران ﮐﻨﺘﺮل ﻧﻘﻞ و اﻧﺘﻘﺎل دادﻩ هﺎ ﺷﺒﮑﻪ و دروازﻩ ﺑﺎﻧﻬﺎ‬ ‫ﻓﻴﻠﺘﺮهﺎﯼ ﻗﺪﻳﻤﯽ ﺑﺴﺘﻪ‬ ‫ﻓﻴﻠﺘﺮهﺎﯼ ﺣﺎﻟﺖ ﭘﺬﻳﺮ ﺑﺴﺘﻪ‬ ‫دﻳﻮارﻩ هﺎﯼ ﺁﺗﺶ ﭘﺮوﮐﺴﯽ دار‬ ‫ﮐﺪام ﺗﮑﻨﻮﻟﻮژﯼ ﺑﺮاﯼ ﺳﺎﺧﺖ دﻳﻮارﻩ هﺎﯼ ﺁﺗﺶ ﺑﻬﺘﺮ اﺳﺖ؟‬ ‫ﺳﻔﺎرﺷﯽ ﻧﻤﻮدن دﻳﻮارﻩ هﺎﯼ ﺁﺗﺶ‬ ‫اﺗﺼﺎل دادﻩ و ﻻﻳﻪ هﺎﯼ ﻓﻴﺰﻳﮑﯽ را ﻓﺮاﻣﻮش ﻧﻨﻤﺎﻳﻴﺪ‬ ‫اﺗﺮﻧﺖ، ﺳﻠﻄﺎن ﺑﺮﻗﺮارﯼ ارﺗﺒﺎط‬ ‫‪ARP ARP ARP‬‬ ‫ﺳﻮﻳﭻ و هﺎب‬ ‫راﻩ ﺣﻞ هﺎﯼ اﻳﻤﻨﯽ ﺷﺒﮑﻪ هﺎ‬ ‫اﻳﻤﻨﯽ ﻻﻳﻪ ‪Application‬‬ ‫)‪Secure Socket Layer (SSL‬‬ ‫اﻳﻤﻨﯽ در ﺳﻄﺢ ‪IPsec-IP‬‬ ‫)‪IPSec Authentication Header (AH‬‬ ‫)‪IPSec Encapsulating Security Payload (ESP‬‬ ‫ﺁﻳﺎ ‪ IPSe‬و 6‪ IPv‬ﻣﺎ را ﻧﺠﺎت ﺧﻮاهﻨﺪ داد؟‬

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‫‪Learning TCP/IP‬‬

‫‪BY: Nasser-Desperado‬‬

‫ﻧﺤﻮۀ ﺷﺒﮑﻪ ﺑﻨﺪﯼ ﺑﺎ ‪: TCP/IP‬‬
‫ﺑﺮاﯼ اﻳﻨﮑﻪ ﺑﺪاﻧﻴﺪ هﮑﺮ هﺎ از ﭼﻪ روﺷﻬﺎﻳﯽ ﺑﺮاﯼ ﺣﻤﻠﻪ ﺑﻪ ﺳﻴﺴﺘﻤﻬﺎﯼ ﮐﺎﻣﭙﻴﻮﺗﺮﯼ از ﻃﺮﻳﻖ ﺷﺒﮑﻪ اﺳﺘﻔﺎدﻩ ﻣﯽ‬ ‫ﮐﻨﻨﺪ ﻻزم اﺳﺖ ﺷﻨﺎﺧﺖ ﮐﻠﯽ از ﺑﻴﺸﺘﺮ ﺗﮑﻨﻮﻟﻮژﯼ ﺷﺒﮑـﻪ ﻋﻤﻮﻣﯽ داﺷﺘـﻪ ﺑﺎﺷﻴﺪ. ﭘﺮوﺗﮑﻞ ﮐﻨﺘﺮل اﻧﺘﻘﺎل ﻳﺎ ﭘﺮوﺗﮑﻞ‬ ‫اﻳﻨﺘﺮﻧﺖ )‪ (TCP/IP‬ﻧﺎم ﮐﺎرﺑﺮدﯼ ﻣﻴﺒﺎﺷﺪ ﮐﻪ در ﻣﻮرد ﻳﮑـﺴﺮﯼ ﭘﺮوﺗﮑﻞ هﺎﯼ ارﺗﺒﺎﻃﯽ ﮐـﺎﻣﭙﻴﻮﺗﺮ ﺑﻪ ﮐـﺎﻣﭙﻴﻮﺗﺮ‬ ‫از ﻃﺮﻳﻖ ﺷﺒﮑـﻪ اﺳﺘﻔـﺎدﻩ ﻣﻴﺸﻮد اﻳﻦ ﺑﺤﺚ ﺧﻼﺻـﻪ اﯼ از ﻋﻤﻠﮑﺮدهـﺎﯼ اﺻـﻠﯽ ‪ TCP/IP‬ﻣﯽ ﺑـﺎﺷـﺪ.ﻗﺼـﺪ ﻣﻦ‬ ‫ﺑﻴﺸﺘﺮ ﺗﺤﻠﻴﻞ ‪ TCP/IP‬اﺳﺖ و اﻳﻨﮑـﻪ هـﮑﺮ هﺎ ﭼﮕﻮﻧـﻪ ﻣﯽ ﺗﻮاﻧﻨﺪ اﻳﻦ ﭘﺮوﺗﮑﻞ را از هﻢ ﺟﺪا ﮐﺮدﻩ و در ﺟﻬﺖ‬ ‫اهﺪاف ﺧﻮد اﺳﺘﻔﺎدﻩ ﮐﻨﻨﺪ.‬ ‫ﻳـﮏ ﺳـﻮال: ﭼﺮا در ﻋﻮض اﻳﻨﮑـﻪ ﭘﺮوﺗﮑﻞ ﻧﺴﺒﺘﺎ ﺧﻮب دﻳﮕﺮ و ﭘﺮوﺗﮑﻞ هﺎﻳﯽ ﮐﻪ ﺑﻪ ﻃﻮر ﮔﺴﺘﺮدﻩ اﺳﺘﻔﺎدﻩ‬ ‫ﻣﻴﺸﻮﻧﺪ ‪ TCP/IP‬را ﻣﻮرد ﺗﺤﻠﻴﻞ ﻓﺮار ﻣﻴﺪهﻴﻢ؟‬ ‫ﺟﻮاب : ‪ TCP/IP‬ﭘﺮوﺗﮑﻠﻬﺎﻳﯽ ﻣﻴﺒﺎﺷﺪ ﮐﻪ ﺑﻪ ﻃﻮر ﻣﺘﺪاول در دﻧﻴﺎ ﻣﻮرد اﺳﺘﻔﺎدﻩ ﻗﺮار ﻣﯽ ﮔﻴﺮد.‬

‫ﻣﺪل ﻣﺮﺟﻊ ‪ OSI‬وﻻﻳﻪ ﺑﻨﺪﯼ ﭘﺮوﺗﮑﻞ :‬
‫در ﺳﺎل 0981 ﺳﺎزﻣﺎن ﺑﻴﻦ اﻟﻤﻠﻠﯽ اﺳﺘﺎﻧﺪارد )‪ (ISO‬ﭘﻴﺸﻨﻬﺎدﯼ ﺑﺮاﯼ ارﺗﺒﺎﻃﺎت ﺑﺮﻧﺎﻣﻪ اﯼ ﻣﻨﺘﺸﺮ ﮐﺮد ﮐﻪ ﻣ ﺪل‬ ‫ﻣﺮﺟﻊ )‪ (OSI‬ﻧﺎﻣﻴﺪﻩ ﺷﺪ.اﻳﻦ ﻣﺪل ﺑﺮ اﺳﺎس ﻻﻳﻪ ﺑﻨﺪﯼ ﭘﺮوﺗﮑﻠﯽ ﻗﺮار داﺷﺖ.ﻳﻌﻨﯽ وﻗﺘﯽ دو ﮐﺎﻣﭙﻴﻮﺗﺮ ﺑﺎ ﻳﮑﺪﻳﮕﺮ‬ ‫ارﺗﺒﺎط ﺑﺮﻗ ﺮار ﻣﻴﮑﻨﻨ ﺪ ﻳﮑ ﺴﺮﯼ ﻣ ﺪﻟﻬﺎﯼ ﻧ ﺮم اﻓ ﺰارﯼ ﮐﻮﭼ ﮏ ﺑ ﺮ روﯼ ه ﺮ ﺳﻴ ﺴﺘﻢ،ﻣﺠﻤﻮﻋـﻪ اﯼ از وﻇ ﺎﻳﻒ را‬ ‫اﻧﺠﺎم ﻣﯽ دهـﺪ ﺗﺎ ارﺗﺒﺎط ﺷﮑـﻞ ﮔﻴﺮد.ﻳﮏ ﻣﺪول اﻃﻤﻴﻨﺎن ﻣﯽ دهﺪ ﮐﻪ‬ ‫دادﻩ هﺎ ﺑﻪ ﻃﻮر ﻣﻨﺎﺳﺐ ﻓﺮﻣﺖ ﺷﺪﻩ اﻧﺪ،ﻣﺪل دﻳﮕﺮ ﻣﺮاﻗﺐ اﻧﺘﻘﺎل دوﺑﺎرۀ ﺑ ﺴﺘﻪ ه ﺎﯼ ﻧ ﺮم اﻓ ﺰارﯼ از دﺳ ﺖ رﻓﺘ ﻪ‬ ‫ﻣﯽ ﺑﺎﺷﻨﺪ وﻣﺪل دﻳﮕﺮﯼ ﺑﺴﺘﻪ هﺎ را از ﮐﺎرﺗﯽ ﺑﻪ ﮐﺎرت دﻳﮕﺮ از ﻃﺮﻳﻖ اﻳﻨﺘﺮﻧ ﺖ اﻧﺘﻘ ﺎل ﻣ ﯽ ده ﺪ.ه ﺮ ﻳ ﮏ از اﻳ ﻦ‬ ‫ﻣﺪﻟﻬﺎ )ﺑﺎ ﻧﺎم ﻻﻳﻪ( وﻇﻴﻔﻪ ﺗﻌﺮﻳﻒ ﺷﺪۀ ﮐ ﻮﭼﮑﯽ در ﻗﺒ ﺎل ﺑﺮﻗ ﺮارﯼ ارﺗﺒ ﺎط دارﻧ ﺪ.ﻣ ﺪوﻟﻬﺎﯼ ارﺗﺒ ﺎﻃﯽ ﮐ ﻪ در ﮐﻨ ﺎر‬ ‫ﻳﮑﺪﻳﮕﺮ ﻗﺮار ﻣﻴﮕﻴﺮﻧﺪ ﺗﻮدۀ ﭘﺮوﺗﮑﻠﯽ ﻧﺎم ﻣﯽ ﮔﻴﺮﻧﺪﮐﻪ ﺣﺎوﯼ ﺷﺎﺧﻪ اﯼ از اﻳﻦ ﻻﻳـﻪ هﺎ )ﻳﮑﯽ در ﺑﺎﻻﯼ دﻳﮕ ﺮﯼ(‬ ‫ﻣﯽ ﺑـﺎﺷﺪ.ﻣﺪل ‪ OSI‬داراﯼ هﻔﺖ ﻻﻳﻪ از ﭼﻨﻴﻦ ﻻﻳ ـﻪ ه ﺎﻳﯽ ﻣ ﯽ ﺑﺎﺷ ﺪ ﮐ ﮥﻩ ه ﺮ ﻳ ﮏ ﻧﻘ ﺶ ﺗﻌﺮﻳ ﻒ ﺷ ﺪﻩ اﯼ در‬ ‫ﻓﺮاﻳﻨﺪ ﻧﻘﻞ و اﻧﺘﻘﺎل دادﻩ هﺎ از ﻃﺮﻳﻖ اﻳﻨﺘﺮﻧﺖ دارﻧﺪ.‬

‫ﻣﺪل ﻣﺮﺟﻊ ‪ OSI‬از هﻔﺖ ﻻﻳﮥ زﻳﺮ ﺗﺸﮑﻴﻞ ﻣﯽ ﺷﻮﻧﺪ :‬
‫ﻻﻳـﮥ1، ﻻﻳﻪ ﻓﻴﺰﻳﮑﯽ،اﻳﻦ ﻻﻳﻪ در واﻗﻊ ﺑﻴﺖ هﺎ را از ﻃﺮﻳﻖ اﺗﺼﺎل ﻓﻴﺰﻳﮑﯽ ﻣﻨﺘﻘﻞ ﻣﯽ ﻧﻤﺎﻳﺪ ﮐﻪ ﻣﯽ ﺗﻮاﻧﺪ ﮐﺎﺑﻞ‬ ‫ﻣﺴﯽ ،ﻓﻴﺒﺮ ﻧﻮرﯼ،اﺗﺼﺎل رادﻳﻮﺋﯽ ﻳﺎ هﺮ ﻣﺤﻴﻂ ﻓﻴﺰﻳﮑﯽ دﻳﮕﺮ ﺑﺎﺷﺪ.‬ ‫ﻻﻳـﻪ 2 ،ﻻﻳﻪ اﺗﺼﺎل دادﻩ هﺎ ،اﻳﻦ ﻻﻳﻪ دادﻩ هﺎ از ﻃﺮﻳﻖ ﮐﻠﻴﺪ ﻣﺮﮐﺰﯼ ﺷﺒﮑﻪ دادﻩ هﺎ ﻣﻨﺘﻘﻞ ﻣﯽ ﻧﻤﺎﻳﺪ.‬ ‫ﻻﻳـﻪ 3 ، ﻻﻳﻪ ﺷﺒﮑﻪ، اﻳﻦ ﻻﻳﻪ ﻣﺴﺌﻮل ﺟﺎ ﺑﺠﺎﻳﯽ دادﻩ هﺎ از ﻃﺮﻳﻖ ﺷﺎﺧﻪ اﯼ از ﻣﺴﻴﺮﻳﺎﺑﻬﺎ ﺑﻪ دﺳﺘﮕﺎﻩ ﻣﻘﺼﺪ،و‬ ‫در ﻃﻮل ﺷﺒﮑﻪ ﻣﯽ ﺑﺎﺷﺪ.‬ ‫ﻻﻳـﻪ 4 ، ﻻﻳﻪ اﻧﺘﻘﺎل ،اﻳﻦ ﻻﻳـﻪ ﺑﺮاﯼ ﻓﺮاهﻢ ﺁورﯼ ﺟﺮﻳﺎن ارﺗﺒﺎﻃﺎت ﻣﻨﻄﻘﯽ ﺑﻴﻦ دو ﺳﻴﺴﺘﻢ اﺳﺘﻔـﺎدﻩ ﻣﯽ ﺷﻮد،ﮐـﻪ‬ ‫ذاﺗﺎ ﺷﺎﻣﻞ ﺑﺴﺘـﻪ هﺎﻳﯽ ﻣﯽ ﺷﻮﻧﺪ ﮐﻪ در ﺣﻴﻦ اﻧﺘﻘﺎل درﺳﺖ ﻣﻨﺘﻘﻞ ﻧﺸﺪﻩ اﻧﺪ و ﺑﺎﻳﺪ دوﺑﺎرﻩ ﻣﻨﺘﻞ ﺷﻮﻧﺪ،ﺑﺴﺘﻪ هﺎ را‬ ‫ً‬ ‫در ﻣﺮﺗﺒﻪ ﻣﻨﺎﺳﺐ ﻗﺮار ﻣﯽ دهﺪ و ﮐﻨﺘﺮل ﺧﻄﺎ را ﻓﺮاهﻢ ﻣﯽ ﺳﺎزد.‬ ‫ﻻﻳـﻪ 5 ، ﻻﻳﻪ دورﻩ ﮐﺎر،اﻳﻦ ﻻﻳﻪ ﺑﺎ دورﻩ هﺎﯼ ﮐﺎر ﺑﻴﻦ دﺳﺘﮕﺎهﻬﺎﯼ ارﺗﺒﺎﻃﯽ هﻤﺎهﻨﮕﯽ ﺑﺮﻗﺮار ﻣﻴﻨﻤﺎﻳﺪ و ﺑﻪ‬ ‫ﺁﻏﺎز ﺑﻪ ﮐﺎر ﺁﻧﻬﺎ ،ﻧﮕﻬﺪارﯼ‬ ‫و ﺑﺮﻧﺎﻣﻪ رﺑﺰﻳﺸﺎن ﮐﻤﮏ ﻣﯽ ﻧﻤﺎﻳﺪ.‬ ‫ﻻﻳـﻪ 6 ، ﻻﻳﻪ ﻧﻤﻮﻧﻪ ﺳﺎزﯼ،اﻳﻦ ﻻﻳﻪ ﺑﺎ روﺷﯽ ﺳﺮ وﮐﺎر دارد ﮐﻪ در ﺁن اﺟﺰاﯼ دادﻩ هﺎ ﺑﺮاﯼ اﻧﺘﻘﺎل ﻧﻤﻮدار‬ ‫ﺧﻮاهﻨﺪ ﺷﺪ.ﻣﺜﻞ ﻣﺮﺗﺒﻪ ﻋﺪدﯼ ﺑﻴﺖ هﺎ،ﺑﺎﻳﺖ هﺎ،ﻓﺮﻣﺖ اﻋﺪاد ﺷﻨﺎور و ﻏﻴﺮﻩ.‬ ‫ﻻﻳـﻪ 7 ، ﻻﻳﻪ ﻧﺮم اﻓﺰار ﮐـﺎر ﺑﺮدﯼ، اﻳﻦ ﻻﻳـﻪ ﺑـﻪ ﺻﻮرت ﭘﻨﺠﺮﻩ اﯼ ﻧﺴﺒﺖ ﺑـﻪ ﮐﺎﻧﺎل ارﺗﺒﺎﻃﺎت ﺑـﺮاﯼ ﺧﻮد ﻧﺮم‬ ‫اﻓﺰارهﺎﯼ ﮐـﺎرﺑـﺮدﯼ ﺑﺎ ﺗﻔﺴﻴﺮ دادﻩ هﺎ و ﺗﻐﻴﻴﺮ ﺁﻧﻬﺎ ﺑﻪ اﻃﻼﻋﺎت ﺧﻮاﻧﺎ ﺑﺮاﯼ ﻧﺮم اﻓﺰارهﺎﯼ ﮐﺎرﺑﺮدﯼ ﻋﻤﻞ ﻣﯽ‬ ‫ﻧﻤﺎﻳﺪ.‬

‫‪ TCP/IP‬ﭼﮕﻮﻧﻪ ﺑﺮاﯼ اﻧﺘﻘﺎل دادﻩ هﺎ ﺑﺎ ﺳﻴﺴﺘﻢ اﺳﺘﻔﺎدﻩ ﻣﯽ ﺷﻮﻧﺪ؟‬
‫در ﺣﺎﻟﯽ ﮐﻪ ﺑﺴﻴﺎرﯼ از ﻣﻌﻴﺎر هﺎﯼ ﻣﺪل ﻣﺮﺟﻊ ‪ OSI‬در ﭘﺮوﺗﮑﻞ ﺷﺒﮑﻪ اﯼ ﺑﻪ ﮐﺎر ﻣﯽ روﻧﺪ،اﻣﺎ ﭘﺮوﺗﮑﻞ ﺧﺎﺻﯽ‬ ‫را در ﻣﻮرد ﺗﺠﺰﻳﻪ و ﺗﺤﻠﻴﻞ ﻗﺮار ﻣﯽ دهﻴﻢ ﮐـﻪ ‪ TCP/IP‬ﻣﯽ ﺑﺎﺷﺪ.‪ TCP/IP‬ﺑﻪ ﺷﺪت ﺑﻪ اﻧﺘﻬﺎﯼ ﭼﻬﺎر ﻻﻳـﻪ‬ ‫ﻣﺪل ﻣﺮﺟﻊ ‪ OSI‬وﺻﻞ ﻣﯽ ﺷﻮد و هﺮ ﻣﻮردﯼ ﮐﻪ ﺑﺎﻻﯼ ‪ TCP/IP‬ﻣﯽ ﺑﺎﺷﺪ ﺑﻪ ﺻﻮرت ﺑﺮﻧﺎﻣﻪ ﮐﺎرﺑﺮدﯼ دﻳﺪﻩ‬ ‫ﻣﯽ ﺷﻮد،ﺑﻨﺎﺑﺮاﻳﻦ ﻻﻳـﻪ هﺎﯼ ﻧﺮم اﻓﺰار ﮐﺎرﺑﺮدﯼ،ﻧﻤﻮدار ﺳﺎزﯼ و دورﻩ ﮐﺎرﯼ ﻣﺪل ﻣﺮﺟﻊ ‪ OSI‬وﺻﻞ ﻣﯽ ﺷﻮد‬ ‫و هﺮ ﻣﻮردﯼ ﮐﻪ ﺑﺎﻻﯼ ‪ TCP/IP‬ﻣﻴﺒﺎﺷﺪ ﺑﻪ ﺻﻮرت ﺑﺮﻧﺎﻣﻪ ﮐﺎرﺑﺮدﯼ دﻳﺪﻩ ﻣﯽ ﺷﻮﻧﺪ،ﺑﻨﺎﺑﺮاﻳﻦ ﻻﺑـﻪ هﺎﯼ ﻧﺮم‬ ‫اﻓﺰار ﮐـﺎرﺑﺮدﯼ ،ﻧﻤﻮدارﺳﺎزﯼ و دورﻩ ﮐﺎرﯼ ﻣﺪل ﻣﺮﺟﻊ ‪ OSI‬ﺗﻤﺎﻣﺎ در ﭘﺮوﻧﺪﻩ هـﺎﯼ ﺑﺮﻧﺎﻣـﻪ ﮐـﺎرﺑﺮدﯼ ﺟﺎﯼ‬

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‫‪Learning TCP/IP‬‬

‫‪BY: Nasser-Desperado‬‬

‫ﻣﯽ ﮔﻴﺮد.‪ TCP/IP‬روﯼ اﻧﺘﻘﺎل دادﻩ هــﺎ از ﺁن ﻧﺮم اﻓﺰار ﮐـﺎر ﺑﺮدﯼ ﻣﺘﻤﺮﮐـﺰ ﻣﯽ ﺑـﺎﺷﺪ.از ﻧﻘﻄـﻪ ﻧﻈﺮ‬ ‫‪ TCP/IP‬ﻻﻳـﻪ هــﺎﯼ زﻳﺮ ﺑﺮاﯼ ارﺗﺒﺎط اﺳﺘﻔﺎدﻩ ﻣﯽ ﺷﻮﻧﺪ.‬ ‫ﻻﻳﻪ ﻧﺮم اﻓﺰار ﮐﺎرﺑﺮدﯼ: اﻳﻦ ﻻﻳﻪ ﺧﻮدش ‪ TCP/IP‬ﻧﻤﯽ ﺑﺎﺷﺪ واز ﺑﺮﻧﺎﻣﻪ هﺎﯼ ﺧﺎﺻ ﯽ ﺳ ﺎﺧﺘﻪ ﺷ ﺪﻩ اﺳ ﺖ واز‬ ‫ﻃﺮﻳﻖ ﺷ ﺒﮑﻪ ﺑ ﺎ اﺳ ﺘﻔﺎدﻩ از ‪ TCP/IP‬ارﺗﺒ ﺎط ﺷ ﮑﻞ ﻣ ﯽ ده ﺪ.ﻣ ﺪول ارﺗﺒ ﺎﻃﯽ در اﻳ ﻦ ﻻﻳ ـﻪ ﻣﻤﮑ ﻦ اﺳ ﺖ ﺷ ﺎﻣﻞ‬ ‫ﻣﺮورﮔﺮ وب،ﺳﺮوﻳﺲ دهﻨﺪﻩ وب،دو ﺳﺮوﻳﺲ ﻣﺮﺳﻮﻟـﻪ ﭘﺴﺘﯽ ،ﺳﺮوﻳﺲ دهﻨﺪﻩ وﺳﺮوﻳﺲ ﮔﻴﺮﻧﺪﻩ ﺗﻠﻨﺖ،ﺳ ﻮﻳﺲ‬ ‫دهﻨﺪﻩ وﺳﺮوﻳﺲ ﮔﻴﺮﻧﺪﻩ ‪ FTP‬ﻳﺎ ﻧﺮم اﻓﺰارهﺎﯼ ﮐﺎرﺑﺮدﯼ دﻳﮕﺮ ﻣﯽ ﺑﺎﺷﺪ.‬ ‫ﻻﻳﻪ اﻧﺘﻘﺎل : اﻳﻦ ﻻﻳﻪ ﺷﺎﻣﻞ ﭘﺮوﺗﮑﻞ ﮐﻨﺘﺮل اﻧﺘﻘﺎل ‪ TCP‬و ﻣﺸﺎﺑﻪ ﺁن،ﭘﺮوﺗﮑﻞ دﻳ ﺎﮔﺮام ﮐ ﺎرﺑﺮ)‪، (UDP‬ﭘﺮوﺗﮑ ﻞ‬ ‫ﺳﺎدﻩ اﯼ ﻣﯽ ﺑﺎﺷﺪ ﮐﻪ ﺑﺎ در اداﻣﻪ ﺑﺎ ﺟﺰﺋﻴﺎت ﺑﻴﺸﺘﺮﯼ ﺁن را ﺗﻮﺿﻴﺢ ﺧﻮاهﻢ داد.اﻳﻦ ﻻﻳ ـﻪ ﺗ ﻀﻤﻴﻦ ﻣ ﯽ ﻧﻤﺎﻳ ﺪ ﮐ ـﻪ‬ ‫ﮐﻠﻴـﻪ ﺑﺴﺘـﻪ هﺎ ﺑﻪ ﻣﮑﺎن ﻣﻨﺎﺳﺒﯽ در دﺳﺘﮕﺎﻩ ﻣﻘﺼﺪ ارﺳﺎل ﻣﯽ ﺷﻮﻧﺪ و ﻧﻴﺰ ﻣﯽ ﺗﻮاﻧﺪ ارﺳﺎل ﻣﻨﺎﺳﺐ ﺑ ﺴﺘﻪ ه ﺎ را‬ ‫ﺑﺎ ﻣﺮاﺣﻞ درﺳﺖ ﺑﺮاﯼ ﺑﺮﻧﺎﻣﻪ هﺎﯼ ﮐﺎرﺑﺮدﯼ ﮐﻪ ﺑﻪ اﻳﻦ ﻋﻤﻠﻴﺎت ﻧﻴﺎز دارﻧﺪ را ﻓﺮاهﻢ ﻣﯽ ﺁورد.‬ ‫ﻻﻳﻪ ﺷﺒﮑﻪ : اﻳﻦ ﻻﻳﻪ ﺑﺮ ﭘﺎﻳ ﻪ ﭘﺮوﺗﮑ ﻞ اﻳﻨﺘﺮﻧ ﺖ ﻗ ﺮار دارد و ه ﺪف ﺁن ارﺳ ﺎل ﺑ ﺴﺘﻪ ه ﺎ ﺑ ـﻪ دﻧﺒ ﺎل ه ﻢ از ﻃﺮﻳ ﻖ‬ ‫ﺷﺒﮑﻪ،از ﮐﺎﻣﭙﻴﻮﺗﺮ ﻣﺒ ﺪا ﺑ ـﻪ دﺳ ﺘﮕﺎﻩ ﻣﻘ ﺼﺪ ﻣ ﯽ ﺑﺎﺷ ﺪ.ﺑ ﺎ اﺳ ﺘﻔﺎدﻩ از واژﻩ ﺷﻨﺎﺳ ﯽ ﻣ ﺪل ﻣﺮﺟ ﻊ ‪، OSI‬ﻻﻳ ﻪ ‪IP‬‬ ‫ﮔﻬﯽ اوﻗﺎت ﻻﻳﻪ 3 ﻧﻴﺰ ﻧﺎﻣﻴﺪﻩ ﻣﯽ ﺷﻮد.‬ ‫ﻻﻳـﻪ اﺗﺼﺎل دادﻩ هﺎ : اﻳﻦ ﻻﻳـﻪ ﺑﺴﺘـﻪ ﻧﺮم اﻓﺰارﯼ را از ﻃﺮﻳﻖ هﺮ ﺟﻬ ﺶ ﺷ ﺒﮑﻪ اﻧﺘﻘ ﺎل ﻣ ﯽ ده ﺪ.ﻣ ﺜﻼ اﻳ ﻦ ﻻﻳ ـﻪ‬ ‫در ﮐﺎﻣﭙﻴﻮﺗﺮ دادﻩ هﺎ را از ﮐﺎﻣﭙﻴﻮﺗﺮ ﺗﺎن ﺑﻪ ﻣﺴﻴﺮ ﻳﺎب و ﺑﺮاﯼ ﺷﺒﮑﻪ ﻧﺎﺣﻴﻪ ﻣﺤﻠﯽ ﺟﺎ ﺑﻪ ﺟﺎ ﻣﯽ ﻧﻤﺎﻳﺪ.ﻣﺴﻴﺮ ﻳ ﺎب‬ ‫ﻧﻴﺰ از اﺗﺼﺎل دادﻩ هﺎﻳﺶ ﺑﺮاﯼ ﺟﺎ ﺑﻪ ﺟﺎﻳﯽ دادﻩ هﺎ ﺑﻪ ﻣ ﺴﻴﺮ ﻳ ﺎب دﻳﮕ ﺮ اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﮐﻨ ﺪ.دوﺑﺎرﻩ،ﺑ ﺎ اﺳ ﺘﻔﺎدﻩ از‬ ‫زﺑﺎن ﻣﺪل ﻣﺮﺟﻊ ‪، OSI‬ﻻﻳﻪ اﺗﺼﺎل دادﻩ هﺎ ،ﻻﻳﻪ 2 ﻧﺎﻣﻴﺪﻩ ﻣﯽ ﺷﻮد.‬ ‫ﻻﻳﻪ ﻓﻴﺰﻳﮑﯽ : اﻳ ﻦ ﻻﻳ ﻪ ﻣﺤ ﻴﻂ ﻓﻴﺰﻳﮑ ﯽ ﻣﺜ ﻞ ﺳ ﻴﻢ ﮐﺎﺑ ﻞ ﻳ ﺎ ﻓﻴﺒ ﺮﯼ ﻣ ﯽ ﺑﺎﺷ ﺪ ﮐ ﻪ اﻃﻼﻋ ﺎت در واﻗ ﻊ از ﻃﺮﻳ ﻖ ﺁن‬ ‫ﻣﻨﺘﻘﻞ ﻣﯽ ﮔﺮدد.‬ ‫درﮐ ﻞ ﻻﻳ ﻪ ه ﺎﯼ ‪ Network ,Transport‬از ‪ TCP/IP‬ﺳﻴ ﺴﺘﻢ ﺗ ﺸﮑﻴﻞ ﻣﻴﮕﺮدﻧ ﺪ، واز ﻧ ﺮم اﻓ ﺰارﯼ ﺳ ﺎﺧﺘﻪ‬ ‫ﻣﻴﺸﻮﻧﺪ ﮐﻪ ﺑﺮ روﯼ ﮐﺎﻣﭙﻴﻮﺗﺮ اﺟﺮا ﻣﯽ ﮔﺮدد.ﻓﻘﻂ در ﻣﺪل ‪، OSI‬ﻳﮏ ﻻﻳـﻪ ﺑﺎ هﻤﺎن ﻻﻳـﻪ در ﻗﺴﻤﺖ دﻳﮕﺮ ارﺗﺒ ﺎط‬ ‫ﺑﺮﻗﺮار ﻣﯽ ﻧﻤﺎﻳﺪ.ﺑﻌﻼوﻩ ﻻﻳـﻪ ﭘﺎﻳﻴﻦ ﺗﺮ ﺳﺮوﻳﺴﯽ را ﺑﺮاﯼ ﻻﻳﻪ هﺎﯼ ﺑﺎﻻﺗﺮ ﻓﺮاهﻢ ﻣﯽ ﺁورد.‬ ‫ﺣﺎل ﺑﺎﻳﺪ دﻳﺪ ﮐﻪ اﻳﻦ اﻧﺘﻘﺎل دادﻩ هﺎ ﺑﻴﻦ ﻻﻳﻪ هﺎ ﺑﻪ ﭼﻪ روﺷﯽ ﮐﺎ ﻣﯽ ﮐﻨﻨﺪ؟ هﺮ ﻻﻳـﻪ ﺑـﻪ اﻃﻼﻋ ﺎﺗﯽ در ﺟﻠ ﻮﯼ دادﻩ‬ ‫هﺎ اﻟﺼﺎق ﻣﯽ ﮔﺮدد ﮐـﻪ اﻳﻦ اﻃﻼﻋـﺎت در ﺟﻠﻮﯼ دادﻩ هﺎ اﻟﺼﺎق ﻣﯽ ﮔﺮدد ﮐـﻪ اﻳﻦ اﻃﻼﻋـﺎت را از ﻻﻳـﻪ ﺑﺎﻻﺗﺮ ﺁن‬ ‫ﮐﺴﺐ ﻣﯽ ﮐﻨﺪ.اﻳﻦ اﻃﻼﻋـﺎت اﺿﺎﻓــﻪ ﺷﺪﻩ در ﺟﻠﻮﯼ دادﻩ هﺎ ﻋﻨﻮان ﻧﺎم دارد و ﺷﺎﻣﻞ اﻃﻼﻋﺎت اﺳﺎﺳﯽ در ﻣ ﻮرد‬ ‫ﻻﻳـﻪ ﻣﯽ ﺑﺎﺷﺪ.‬ ‫در هﻨﮕ ﺎم درﻳﺎﻓ ﺖ دادﻩ هﺎ،ﺳﻴ ﺴﺘﻢ ﻣﻘ ﺼﺪ ﺗﻤ ﺎم ﺑ ﺴﺘـﻪ دادﻩ ه ﺎﯼ ارﺳ ﺎﻟﯽ را ﻻﻳ ـﻪ ﺑ ﻪ ﻻﻳ ـﻪ ﺑ ﺎز ﻣ ﯽ ﮐﻨ ﺪ.ﺑ ﺴﺘـﻪ‬ ‫ﺣﺎﺻﻠﻪ ﺑﻪ ﻧﺮم اﻓﺰار ﮐﺎرﺑﺮدﯼ ارﺳﺎل ﻣﯽ ﮔﺮدد ﮐﻪ ﻣﯽ ﺗﻮاﻧﺪ ﺗﻘﺎﺿﺎﯼ وب را ﭘ ﺮدازش ﻧﻤﺎﻳﻨﺪ،ﭘ ﺴﺖ اﻟﮑﺘﺮوﻧﻴﮑ ﯽ‬ ‫را ﻗﺒﻮل ﮐﻨﺪ ﻳﺎ هﺮ ﺁﻧﭽﻪ ﮐﻪ ﻧﺮم اﻓﺰار ﮐﺎرﺑﺮدﯼ ﺑﺮاﯼ اﻧﺠﺎم ﺁن ﻃﺮاﺣﯽ ﺷﺪﻩ اﺳﺖ را اﻧﺠﺎم دهﺪ.‬ ‫ﺑﺪون ﺗﻮﺟـﻪ ﺑـﻪ ﻧﺮم اﻓﺰار ﮐﺎرﺑﺮدﯼ ﻣﻮرد اﺳﺘﻔﺎدﻩ در اﻳﻨﺘﺮﻧﺖ راﻳﺎﻧـﻪ دادﻩ هﺎ را ﺑﻪ ﺷﮑﻞ ﺛﺎﺑﺖ،ﺑ ـﻪ ﺑ ﺎﻻ و ﭘ ﺎﻳﻴﻦ‬ ‫ﻻﻳـﻪ هﺎﯼ ﺗﻮدﻩ ﭘﺮوﺗﮑﻞ اﻧﺘﻘﺎل ﻣﯽ دهﺪ.ﺳﺮوﻳﺲ دهﻨﺪﮔﺎن دادﻩ هﺎ را از ﻃﺮﻳﻖ ﺗﻮدﻩ ه ﺎﯼ ‪ TCP/IP‬ارﺳ ﺎل ﻣ ﯽ‬ ‫ﮐﻨﻨﺪ.‬

‫‪: TCP/IP‬‬
‫ﺣﺎﻻ ﮐﻪ ﺷﻨﺎﺧﺘﯽ از ﭘﺮوﺗﮑﻞ ﻻﻳﻪ ﺑﻨﺪﯼ ﭘﻴﺪا ﮐﺮدﻳﺪ ﻣ ﯽ ﺧ ﻮاهﻢ در اﻳ ﻦ ﻗ ﺴﻤﺖ ‪ TCP/IP‬را ﺑ ﺎ ﺟﺰﺋﻴ ﺎت ﺑﻴ ﺸﺘﺮﯼ‬ ‫ﺗﻮﺿﻴﺢ دهﻢ.‬ ‫ﺧﺎﻧﻮاد ﭘﺮوﺗﮑﻞ هﺎﯼ ‪ TCP/IP‬از ﭼﻨﺪﻳﻦ ﺑﺨﺶ ﺗﺸﮑﻴﻞ ﻣﯽ ﺷﻮﻧﺪ:ﭘﺮوﺗﮑﻞ ﮐﻨﺘﺮﻻﻧﺘﻘﺎل ‪، TCP‬ﭘﺮوﺗﮑﻞ دﻳ ﺎﮔﺮام‬ ‫ﮐﺎرﺑﺮ)‪، (UDP‬ﭘﺮوﺗﮑﻞ اﻳﻨﺘﺮﻧﺖ )‪ (IP‬وﭘﺮوﺗﮑ ﻞ ﭘﻴﻐ ﺎم ﮐﻨﺘ ﺮل اﻳﻨﺘﺮﻧ ﺖ )‪ TCP/IP.(ICMP‬در ﺳ ﺮﯼ اﺳ ﻨﺎد‬ ‫اﻳﺠﺎد ﺷﺪﻩ و ﻧﮕﻬﺪارﯼ ﺷﺪﻩ ادارﻩ ﮐﺎر ﻣﻬﻨﺪﺳﯽ اﻳﻨﺘﺮﻧﺖ )‪ (IEFT‬ﺗﻌﺮﻳﻒ ﻣﯽ ﺷﻮﻧﺪ.‬ ‫‪ TCP/IP‬در اﺻﻞ ﺑﺮاﯼ ﺗﺤﻘﻴﻘﺎت و ﻋﻠﻮم ﺁﻣﻮزﺷﯽ و داﻧﺸﮕﺎهﯽ ﺑﻪ وﺟﻮد ﺁﻣﺪ و داراﯼ ﻗﺎﺑﻠﻴﺘﻬ ﺎﯼ اﻳﻤﻨ ﯽ ﻗ ﻮﯼ‬ ‫ﻧﻤ ﯽ ﺑﺎﺷ ﺪ.ﻣﺠﻤﻮﻋ ﮥ ﻗ ﺪﻳﻤﯽ ﭘﺮوﺗﮑ ﻞ ‪ TCP/IP‬ه ﻴﭻ وﺳ ﻴﻠﻪ اﯼ ﺑ ﺮاﯼ ﺗ ﻀﻤﻴﻦ ﻣﺤﺮﻣﺎﻧ ﻪ ﺳ ﺎزﯼ،ﻳﮑﭙﺎرﭼﮕﯽ و‬ ‫ﺗﺎﻳﻴﺪ دادﻩ هﺎﯼ ﻣﻨﺘﻘﻞ ﺷﺪﻩ از ﻃﺮﻳﻖ اﻳﻨﺘﺮﻧﺖ ﻧﺪارد.ﺑﺪون ﮐﻨﺘﺮل ﻣﺤﺮﻣـﺎﻧـﻪ ﺳﺎزﯼ و ﻳﮑﭙﺎرﭼﮕـﯽ،وﻗﺘﯽ ﺑ ﺴﺘـﻪ اﯼ‬ ‫را از ﻃﺮﻳﻖ اﻳﻨﺘﺮﻧﺖ ارﺳﺂال ﻣﯽ ﻧﻤـﺎﻳـﻨﺪ،‪ TCP/IP‬اﻳﻦ اﻣﮑـﺎن را ﺑﺮاﯼ دﻳـﮕﺮ ﻣﺸﺘﺮﮐﺎن ﻓﺮاهﻢ ﻣﯽ ﮐﻨﺪ ﺗﺎ دادﻩ‬ ‫هﺎ را ﺑﺒﻴﻨﻨﺪ ﻳﺎ ﺗﻐﻴﻴﺮ دهﻨﺪ.ﺑﻌﻼوﻩ ،ﺑﺪون ﺗﺎﻳﻴﺪﻳ ﻪ ،هﮑﺮه ﺎ ﻣ ﯽ ﺗﻮاﻧﻨ ﺪ دادﻩ ه ﺎﻳﯽ را ﺑﺮاﻳﺘ ﺎن ارﺳ ﺎل ﻧﻤﺎﻳﻨ ﺪ، و ﺑ ﻪ‬ ‫ﻃﺮﻳﻖ ﻣﺠﺎزﯼ ﻣﺴﺌﻮﻟﻴﺖ دادﻩ هﺎﯼ ارﺳﺎﻟﯽ از ﻃﺮف دﻳﮕﺮان ﺑﻪ ﺷﺒﮑﻪ را ﺑﻪ ﻋﻬﺪﻩ ﻣﯽ ﮔﻴﺮﻧﺪ.‬ ‫در ﮔﺬﺷ ﺘﻪ ،ﮐﻠﻴ ﻪ ﻗﺎﺑﻠﻴ ﺖ ه ﺎﯼ اﻳﻤﻨ ﯽ در ﺷ ﺒﮑﻪ ه ﺎﯼ ‪ TCP/IP‬در ﻧ ﺮم اﻓﺰاره ﺎﯼ ﮐ ﺎرﺑﺮدﯼ و ﻧ ﻪ در ﺗ ﻮدﻩ‬ ‫‪ TCP/IP‬اﺟﺮا ﻣﯽ ﮔﺮدد.ﺗﻨﻬﺎ در ﺳﺎﻟﻬﺎﯼ اﺧﻴﺮ اﻳﻤﻨﯽ در ‪ TCP/IP‬و ﺑﻪ ﺷ ﮑﻞ ﺿ ﻤﻴﻤﻪ ﭘﺮوﺗﮑ ﻞ اﺿﺎﻓ ـﻪ ﺷ ﺪﻩ‬ ‫اﺳﺖ ﮐﻪ ‪ IPSec‬ﻧﺎﻣﻴﺪﻩ ﻣﯽ ﺷﻮد.ﺑﺎ اﻳﻨﮑﻪ ‪ IPSec‬ﺗﻌﻬﺪ ﺑﺴﻴﺎر ﺑـﺎﻻﻳﯽ دارد اﻣﺎ هﻨﻮز ﺑﻪ ﻃﻮر ﮔﺴﺘﺮدﻩ اﺟﺮا ﻧﻤﯽ‬ ‫ﮔـﺮدد.ﺑﻨـﺎﺑﺮاﻳﻦ،ﺑﺪون اﻳﻦ ﻗﺎﺑﻠﻴﺘﻬـﺎﯼ اﻳﻤﻨﯽ ﻧﺼﺐ ﺷﺪﻩ در اﻳﻦ ﭘﺮوﺗـﮑﻞ،ﻧﺮم اﻓﺰارهـﺎﯼ ﮐﺎرﺑﺮدب هﻨﻮز ﺧﻮدﺷ ﺎن‬ ‫را ﺑﺎ اﻳﻤﻨﯽ اﺟﺮاﻳﯽ ﺗﺠﻬﻴﺰ ﻧﻤﯽ ﮐﻨﻨﺪ.‬

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‫‪Learning TCP/IP‬‬

‫‪BY: Nasser-Desperado‬‬

‫ﺣـﺎﻻ ﻣﯽ ﺧﻮاهﻢ ﮐﻪ اﻋﻀـﺎﯼ ﺧﺎﻧﻮادﻩ ‪ TCP/IP‬را ﺗﮏ ﺗﮏ ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار دهﻢ ﺗﺎ ﺁﻧﺮا ﺑﻬﺘﺮ درﮎ ﻧﻤﺎﻳﻴﺪ و‬ ‫روش ﮐﺎر هـﮑﺮهـﺎ را ﻧﻴﺰ ﻣﻮرد ﺑﺮرﺳــــﯽ ﻗﺮار ﺧﻮاهﻴﻢ داد.‬

‫ﭘﺮوﺗﮑﻞ ﮐﻨﺘﺮل اﻧﺘﻘﺎل ‪: TCP‬‬
‫‪ TCP‬ﭘﺮ ﮐﺎرﺗﺮﻳﻦ ﭘﺮوﺗﮑﻞ اﻳﻨﺘﺮﻧﺖ ﻣﯽ ﺑﺎﺷﺪ ﮐﻪ اﻣﺮوزﻩ ﺑﺎ ﻧﺮم اﻓﺰارهﺎﯼ ﮐﺎرﺑﺮدﯼ ﺑﺴﻴﺎرﯼ اﺳﺘﻔﺎدﻩ ﻣﯽ‬ ‫ﺷﻮد.در ﺑﻴﻦ هﺰاران ﻧﺮم اﻓﺰار ﮐﺎرﺑﺮدﯼ ﮐﻪ از ‪ TCP‬اﺳﺘﻔﺎدﻩ ﻣﯽ ﻧﻤﺎﻳﻨﺪ، ﺑﻌﻀﯽ از ﺑﺮﺟﺴﺘﻪ ﺗﺮﻳﻦ ﺁﻧﻬﺎ ﻋﺒﺎرﺗﻨﺪ‬ ‫از:‬ ‫اﺗﻘﺎل ﻓﺎﻳﻞ : ﮐﻪ از ﭘﺮوﺗﮑﻞ اﻧﺘﻘﺎل ﻓﺎﻳﻞ )‪ (FTP‬اﺳﺘﻔﺎدﻩ ﻣﯽ ﻧﻤﺎﻳﻨﺪ.‬ ‫ﺗﻠﻨﺖ : ﮐﻪ واﺳﻄﻪ دﺳﺘﻮر ﺧﻄﯽ راﻩ دور را اﺳﺘﻔﺎدﻩ ﻣﯽ ﮐﻨﺪ.‬ ‫ﭘﺴﺖ اﻟﮑﺘﺮوﻧﻴﮑﯽ : ﮐﻪ از ﭘﺮوﺗﮑﻞ هﺎﯼ ﻣﺨﺘﻠﻒ اﺳﺘﻔﺎدﻩ ﻣﯽ ﻧﻤﺎﻳﻨﺪ ﮐﻪ ﻋﺒﺎرﺗﻨﺪ از: ‪Post (Simple Mail‬‬ ‫‪Transfer Protocol (SMTP,(Office Protocol (POP‬‬ ‫ﻣﺮورﮔﺮ وب : ﮐﻪ از ﭘﺮوﺗﮑﻞ )‪ Hypertext Transfer Protocol (HTTP‬اﺳﺘﻔﺎدﻩ ﻣﯽ ﻧﻤﺎﻳﻨﺪ.‬ ‫هﺮ ﻳﮏ از اﻳﻦ ﻧﺮم اﻓﺰارهﺎﯼ ﮐﺎرﺑﺮدﯼ ﺑﺴﺘﻪ هﺎﻳﯽ را ﺗﻮﻟﻴﺪ ﻣﯽ ﻧﻤﺎﻳﻨﺪ و ﺁﻧﻬﺎ را ﺑﻪ ﺗﻮدﻩ ‪ TCP/IP‬دﺳﺘﮕﺎﻩ‬ ‫ﻣﺤﻠﯽ اﻧﺘﻘﺎل ﻣﯽ دهﻨﺪ. ﻧﺮم اﻓﺰار ﻻﻳﻪ ‪ TCP‬ﮐﻪ ﺑﺮ روﯼ ﺳﻴﺴﺘﻢ وﺟﻮد دارد، اﻳﻦ دادﻩ هﺎ را ﺑﺮﻣﯽ دارد و ﺑﺴﺘﻪ‬ ‫هﺎﯼ ‪ TCP‬ﺑﺮ روﯼ هﺮ ﺑﺴﺘﻪ ﻧﺮم اﻓﺰارﯼ ﺗﻮﻟﻴﺪ ﻣﯽ ﻧﻤﺎﻳﻨﺪ.ﺑﺮاﯼ اﻳﻨﮑﻪ ﺑﺪاﻧﻴﺪ ﮐﻪ ﺣﻤﻼت ﺑﻪ ﭼﻪ روﺷﯽ در‬ ‫ﺑﺮاﺑﺮ ‪ TCP‬ﮐﺎر ﻣﯽ ﻧﻤﺎﻳﻨﺪ، ﻻزم اﺳﺖ ﭼﻨﺪﻳﻦ زﻣﻴﻨﻪ و ﻗﺼﺪ ﺁﻧﻬﺎ را در ﻋﻨﻮان ‪ TCP‬ﺗﺤﻠﻴﻞ ﮐﻨﻢ.ﺑﻪ ﺧﺼﻮص‬ ‫ﺑﻪ ﺷﺮح ﺷﻤﺎرﻩ دروازﻩ هﺎ،اﻋﺪاد ﻣﺮاﺣﻞ ﮐﺎر و اﻋﻼم ﻣﺮاﺣﻞ ﮐﺎر،و ﺑﻴﺘﻬﺎﯼ ﮐﻨﺘﺮل ﻣﯽ ﭘﺮدازم.‬

‫ﺷﻤﺎرﻩ دروازﻩ هﺎﯼ ‪: TCP‬‬
‫ﻋﻨﻮان هﺮ ﺑﺴﺘﻪ ﺷﺎﻣﻞ ‪ TCP‬ﺷﺎﻣﻞ دو ﺷﻤﺎرﻩ دروازﻩ ﻣﯽ ﺑﺎﺷ ﺪ: دروازﻩ ﻣﺒ ﺪا و دروازﻩ ﻣﻘ ﺼﺪ.اﻳ ﻦ اﻋ ﺪاد 61‬ ‫ﺑﻴﺘﯽ ﻣﺜﻞ درهﺎﯼ ﮐﻮﭼﮑﯽ روﯼ ﺳﻴﺴﺘﻢ ﻣﯽ ﺑﺎﺷﻨﺪ ﮐﻪ از ﺁﻧﺠﺎ دادﻩ هﺎ ﻣﯽ ﺗﻮاﻧﻨﺪ ارﺳﺎل ﻳﺎ درﻳﺎﻓﺖ ﺷ ﻮﻧﺪ.دروازﻩ‬ ‫هﺎ درهﺎﯼ ﻓﻴﺰﻳﮑﯽ ﻧﻤﯽ ﺑﺎﺷﻨﺪ و وﺟﻮدﯼ ﻣﻨﻄﻘﯽ دارﻧﺪ ﮐﻪ ﺑﺎ ﻧﺮم اﻓﺰار ﺗﻮدﻩ ‪ TCP/IP‬ﺗﻌﺮﻳﻒ ﻣ ﯽ ﺷ ﻮﻧﺪ.ﺗﻌ ﺪاد‬ ‫53556 دروازﻩ ‪ TCP‬ﻣﺘﻔﺎوت ﺑ ﺮ روﯼ ه ﺮ دﺳ ﺘﮕﺎﻩ وﺟ ﻮد دارد.دروازﻩ ﺻ ﻔﺮ ‪ TCP‬دروازﻩ اﯼ ذﺧﻴ ﺮﻩ ﺷ ﺪﻩ‬ ‫ﻣ ﯽ ﺑﺎﺷ ﺪ و اﺳ ﺘﻔﺎدﻩ ﻧﻤ ﯽ ﮔ ﺮدد.ه ﺮ ﺑ ﺴﺘﻪ ‪ TCP‬از درون ﻳﮑ ﯽ از اﻳ ﻦ دره ﺎ و ﺷ ﻤﺎرﻩ دروازﻩ ‪ TCP‬ﻣﺒ ﺪا از‬ ‫دﺳﺘﮕﺎﻩ ﻣﺒ ﺪا ﺑﻴ ﺮون ﻣ ﯽ ﺁﻳ ﺪ،و ﺑ ﺮاﯼ دروازﻩ دﻳﮕ ﺮﯼ )ﺷ ﻤﺎرﻩ دروازﻩ ﻣﻘ ﺼﺪ‪ ( TCP‬ﺑ ﺮ روﯼ دﺳ ﺘﮕﺎﻩ ﻣﻘ ﺼﺪ‬ ‫رهﺴﭙﺎر ﻣﯽ ﮔﺮدد.‬ ‫وﻗﺘﯽ ﻧﺮم اﻓﺰارﻩ ﮐﺎرﺑﺮدﯼ ﺳﺮوﻳﺲ دهﻨﺪﻩ ‪ TCP‬ﺑﺮ روﯼ ﺳﻴﺴﺘﻢ اﺟﺮا ﻣﯽ ﮔﺮدد.ﺑﺮ روﯼ دروازﻩ ﺧﺎﺻ ﯽ ﺑ ﺮاﯼ‬ ‫ﺑﺴﺘﻪ هﺎﯼ ‪ TCP‬ﮐﻪ از ﺳﺮوﻳﺲ ﮔﻴﺮﻧ ﺪﻩ ﻣ ﯽ ﺁﻳ ﺪ،ﻣﻨﺘﻈﺮ ﭘﺎﺳ ﺦ ﻣ ﯽ ﻣﺎﻧ ﺪ.دروازﻩ اﯼ ﮐ ﻪ دارﯼ ﺳ ﺮوﻳﺲ اﻧﺘﻈ ﺎر‬ ‫ﭘﺎﺳﺦ ﻣﯽ ﺑﺎﺷﺪ را دروازﻩ ﺑﺎز ﻣ ﯽ ﻧ ﺎﻣﻴﻢ،در ﺣ ﺎﻟﯽ ﮐ ﻪ دروازﻩ اﯼ ﮐ ﻪ در ﺁن ﭼﻴ ﺰﯼ در ﺣ ﺎل درﻳﺎﻓ ﺖ ﭘﺎﺳ ﺦ ﻧﻤ ﯽ‬ ‫ﺑﺎﺷﻨﺪ دروازﻩ ﺑﺴﺘﻪ ﻧﺎﻣﻴﺪﻩ ﻣﯽ ﺷﻮد.ﺳﺮوﻳﺲ دهﻨﺪﮔﺎن ﻧﺮم اﻓﺰار ﮐﺎرﺑﺮدﯼ از اﻧﻮاع ﮔﻮﻧ ﺎﮔﻮن ﺑ ﻪ ﺷ ﻤﺎرﻩ در ﮔ ﺎﻩ‬ ‫هﺎﯼ ﺷﻨﺎﺧﺘﻪ ﺷﺪﻩ اﯼ ﮔﻮش ﻓﺮا ﻣﯽ دهﻨﺪ.اﻳﻦ ﺷﻤﺎرﻩ دروازﻩ هﺎﯼ ﺷﻨﺎﺧﺘﻪ ﺷ ﺪﻩ ﺑ ﻪ ﺻ ﻮرت 0071‪ RFC‬هﺠ ﯽ‬ ‫ﻣﯽ ﺷﻮد،ﮐﻪ ﺷﺎﻣﻞ اﻋﺪا ﻣﺨﺘﻠﻒ ﺑﺴﻴﺎر زﻳﺎدﯼ ﻣﯽ ﺑﺎﺷ ﻨﺪ ﮐ ﻪ ﻣﻌﻴﺎره ﺎﯼ ﻣﺘﻔ ﺎوت ‪ TCP/IP‬واﺑ ﺴﺘﻪ ﺑ ﻪ ﭘﺮوﺗﮑ ﻞ‬ ‫هﺎ اﺧﺘﺼﺎص دادﻩ ﻣﯽ ﺷﻮد.‬ ‫ﺷﻤﺎرﻩ دروازﻩ هﺎﯼ ‪ TCP‬ﮐﻪ ﻏﺎﻟﺒﺎ اﺳﺘﻔﺎدﻩ ﻣﯽ ﺷﻮﻧﺪﻋﺒﺎرﺗﻨﺪ از:‬ ‫)‪TCP Port 21-File Transfer Protocol (FTP‬‬ ‫‪TCP Port 23-Telnet‬‬ ‫‪(TCP Port 25-Simple Mail Transfer Protocol (SMTP‬‬ ‫)‪TCP Port 80-World Wide Web (HTTP‬‬ ‫‪TCP Port 666-Doom‬‬ ‫ﺑﺮاﯼ ﺗﻤﺎس ﺑﺎ اﻳﻦ ﺳﺮوﻳﺲ دهﻨﺪﮔﺎن ﻧﺮم اﻓﺰارﯼ ﮐﺎرﺑﺮدﯼ،ﻻﻳﻪ ‪ TCP‬ﺳ ﺮوﻳﺲ ﮔﻴﺮﻧ ﺪﻩ ﺑ ﺴﺘﻪ ه ﺎﻳﯽ را دروازﻩ‬ ‫‪ TCP‬ﻣﻘﺼﺪ ﺗﻮﻟﻴﺪ ﻣﯽ ﮐﻨﺪ ﮐﻪ ﺑﻪ دروازﻩ اﯼ ﺗﻌﻠﻖ دارد ﮐﻪ در ﺁ» ﻧ ﺮم اﻓ ﺰار ﮐ ﺎرﺑﺮدﯼ ﺳ ﺮوﻳﺲ دهﻨ ﺪﻩ در ﺣ ﺎل‬ ‫در ﻳﺎﻓﺖ ﭘﺎﺳﺦ ﻣﯽ ﺑﺎﺷﺪ.دروازﻩ ﻣﺒﺪا ﺑﺮاﯼ ﺑﺴﺘﻪ در ﺧﻮاﺳﺘﯽ از ﻟﺤﺎظ دﻳﻨﺎﻣﻴﮑﯽ ﺗﻮﺳﻂ ﺳﻴﺴﺘﻢ ﻋﺎﻣﻞ ﺑ ﻪ ﺑﺮﻧﺎﻣ ﻪ‬ ‫ﺳ ﺮوﻳﺲ ﮔﻴﺮﻧ ﺪﻩ اﺧﺘ ﺼﺎص دادﻩ ﻣ ﯽ ﺷ ﻮد، و ﻳ ﺎ ﻣﻘ ﺪارﯼ ﺑﻴ ﺸﺘﺮ از 3201 ﺗﻨﻈ ﻴﻢ ﻣ ﯽ ﮔﺮدد،ﺑﻨ ﺎﺑﺮاﻳﻦ دروازﻩ‬ ‫"ﺷﻤﺎرﻩ ﺑﺎﻻﺗﺮ" ﻧﺎﻣﻴﺪﻩ ﻣ ﯽ ﺷ ﻮد.دروازﻩ ﻣﻘ ﺼﺪ درﺧﻮاﺳ ﺘﯽ ﺑ ﺎ ﻧ ﺮم اﻓ ﺰار ﮐ ﺎرﺑﺮدﯼ در ارﺗﺒ ﺎط اﺳ ﺖ،ﮐﻪ در ﺁن‬ ‫ﺳﺮوﻳﺲ دهﻨ ﺪﻩ در ﺣ ﺎل درﻳﺎﻓ ﺖ ﭘﺎﺳ ﺦ ﻣ ﯽ ﺑﺎﺷ ﺪ)ﻣ ﺜﻼ دروازﻩ 08 ‪ TCP Port‬ﺑ ﺮاﯼ ﺗﺮاﻓﻴ ﮏ ‪ .( HTTP‬در‬ ‫ﺑﻴ ﺸﺘﺮ ﻧ ﺮم اﻓﺰاره ﺎﯼ ﮐ ﺎرﺑﺮدﯼ ،ﺳ ﺮوﻳﺲ دهﻨ ﺪﻩ ﺑ ﺴﺘﻪ ه ﺎ، ﭘﺎﺳ ﺨﯽ را ارﺳ ﺎل ﺧﻮاهﻨ ﺪ ﻧﻤ ﻮد ﮐ ﻪ ﺷ ﻤﺎرﻩ ه ﺎﯼ‬ ‫دروازﻩ را ﻣﻌﮑﻮس ﻣﯽ ﮐﻨﺪ.دروازﻩ ﻣﺒﺪا ﺑﺴﺘﻪ ﭘﺎﺳﺦ،ﺷﻤﺎرﻩ دروازﻩ اﯼ ﻣﯽ ﺑﺎﺷﺪ ﮐﻪ ﺑ ﻪ ﺳ ﺮوﻳﺲ ﮔﺒﺮﻧ ﺪﻩ ﺑ ﺴﺘﻪ‬ ‫اﯼ ارﺳ ﺎل ﻣ ﯽ ﺷ ﻮد )ﺑ ﺮاﯼ ﻣﺜ ﺎل 08 ‪ ( TCP Port‬ودروازﻩ ﻣﻘ ﺼﺪ ﺟ ﺎﻳﯽ ﻣ ﯽ ﺑﺎﺷ ﺪ ﮐ ﻪ ﺑ ﻪ ﺳ ﺮوﻳﺲ ﮔﻴﺮﻧ ﺪﻩ‬ ‫ﺑﺴﺘﻪ اﯼ ارﺳﺎل ﻣﯽ ﺷﻮد )ﺑﺮاﯼ ﻣﺜﺎل 4321 ‪.( TCP Port‬‬ ‫ﻣﺪﻳﺮ اﺟﺮاﻳ ﯽ ﺳﻴ ﺴﺘﻢ ﻣ ﯽ ﺗﻮاﻧ ﺪ ه ﺮ ﺳ ﺮوﻳﺲ دهﻨ ﺪﻩ ﻧ ﺮم اﻓ ﺰار ﮐ ﺎرﺑﺮدﯼ را ﭘﻴﮑﺮﺑﻨ ﺪﯼ ﻧﻤﺎﻳ ﺪ ﺗ ﺎ از ه ﺮ ﺷ ﻤﺎرﻩ‬ ‫دروازﻩ اﯼ اﺳﺘﻔﺎدﻩ ﻧﻤﺎﻳﺪ،اﻣﺎ ﺑﺮﻧﺎﻣﻪ هﺎﯼ ﺳﺮ.ﻳﺲ ﮔﻴﺮﻧﺪﻩ ﻣﻨﺘﻈﺮ ﺑﺮﻧﺎﻣﻪ هﺎﯼ ﮐﺎرﺑﺮدﯼ ﻣﯽ ﻣﺎﻧﺪ ﺗﺎ دروازﻩ ه ﺎﯼ‬ ‫-5-‬

‫‪Learning TCP/IP‬‬

‫‪BY: Nasser-Desperado‬‬

‫ﺧ ﺎص ﻣﻘ ﺼﺪ ﻣﻨﺘﻈ ﺮ ﭘﺎﺳ ﺦ ﺑﻤﺎﻧ ﺪ.ﺑﻨ ﺎﺑﺮاﻳﻦ ،اﮔ ﺮ ﺳ ﺮوﻳﺲ ﮔﻴﺮﻧ ﺪﻩ و ﮐ ﺎرﺑﺮ در ﻣ ﻮرد دروازﻩ ﻣﻘ ﺼﺪ ﺳ ﺮوﻳﺲ‬ ‫ﮔﻴﺮﻧﺪﻩ ﺑﺮ روﯼ ﺳﺮوﻳﺲ دهﻨﺪﻩ ﭼﻴﺰﯼ ﻧﺪاﻧﻨﺪ،ﺷﻤﺎرﻩ دروازﻩ هﺎﯼ ﻣ ﻮرد ﺑﺮرﺳ ﯽ در 0071 ‪ RFC‬اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ‬ ‫ﺷﻮد.‬ ‫ﺑﺮاﯼ دﻳﺪن اﻳﻨﮑﻪ ﮐﺪام دروازهﺎ در ﺳﻴ ﺴﺘﻢ 0002/‪ Windows NT‬ﻳ ﺎ ‪ UNIX‬اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﺷ ﻮﻧﺪ،ﻣﯽ ﺗﻮاﻧﻴ ﺪ‬ ‫از دﺳﺘﻮر "‪ "Netstat‬اﺳﺘﻔﺎدﻩ ﻧﻤﺎﻳﻴﺪ.ﺑﺎ ﺗﺎﻳﭗ"‪ "netstat –na‬در ﺧﻂ ﻓﺮﻣﺎن ﻣﯽ ﺗﻮاﻧﻴ ﺪ ﺗﻤ ﺎم دروازﻩ ه ﺎﯼ‬ ‫دادﻩ هﺎﯼ ارﺳﺎﻟﯽ و دروازﻩ هﺎﻳﯽ ﮐﻪ ﻣﻨﺘﻈﺮ درﻳﺎﻓﺖ دادﻩ ه ﺎﯼ ارﺳ ﺎﻟﯽ و دروازﻩ ه ﺎﻳﯽ ﮐ ﻪ ﻣﻨﺘﻈ ﺮ درﻳﺎﻓ ﺖ دادﻩ‬ ‫هﺎ ﻣﯽ ﺑﺎﺷﻨﺪ،ﻧﺸﺎن دادﻩ ﻣﯽ ﺷﻮﻧﺪ.‬

‫ﺑﻴﺘﻬﺎﯼ ﮐﻨﺘﺮل ‪، TCP‬اﺗﺼﺎل ﺳﻪ راهﻪ و ﺷﻤﺎرﻩ ﻣﺮاﺣﻞ ﮐﺎر :‬
‫ﺑﻴﺘﻬﺎﯼ ﮐﻨﺘﺮل ‪ TCP‬ﮐﺪ ﺑﻴﺘﻬﺎ ﻗﺴﻤﺖ ﻗﺎﺑﻞ ﮐﺎرﺑﺪ . ﺧﺎﺻﯽ از ﻋﻨﻮان ‪ TCP‬ﻣ ﯽ ﺑﺎﺷ ﻨﺪ.اﻳ ﻦ ﺷ ﺶ زﻣﻴﻨ ﻪ ﮐﻮﭼ ﮏ‬ ‫)هﺮ ﮐﺪام ﻳﮏ ﺑﻴﺖ ﻃﻮل دارﻧﺪ( ﺷﺮح ﻣﻴﺪهﻨﺪ ﮐﻪ ﮐﺪام ﺑﺨﺶ از دورﻩ ﮐﺎر ﺑﺴﺘﻪ ‪ TCP‬ﺑﺎ ﭼﻪ ﭼﻴ ﺰﯼ هﻤ ﺮاﻩ اﺳ ﺖ‬ ‫)ﻣﺜﻞ ﺷﺮوع دورﻩ ﮐﺎ،ﺗﺎﻳﻴﺪﻳﻪ،ﻳﺎ دورﻩ ﮐﺎرﯼ ﮐﻪ ﮔﺴﺴﺘﻪ ﻣﯽ ﺷﻮﻧﺪ(.اﻟﺒﺘﻪ،ﺑﻴﺘﻬﺎﯼ ﮐﻨﺘ ﺮل ﻣ ﯽ ﺗﻮاﻧﻨ ﺪ دﻻﻟ ﺖ ﻧﻤﺎﻳﻨ ﺪ‬ ‫ﮐﻪ ﺁﻳﺎ ﺑﺴﺘﻪ ﻧﺮم اﻓﺰارﯼ ﺑﻪ ﮐﻨﺘﺮل ﺧﺎص و ﻧﺎﮔﻬﺎﻧﯽ ﺗﻮﺳﻂ ﻻﻳﻪ ‪ TCP‬ﻧﻴﺎز دارد.‬ ‫ﭼﻮن ﺑﻴﺸﺘﺮ اﻓﺮاد ﺑﻴﺘﻬﺎﯼ ﮐﻨﺘﺮل ‪ TCP‬را "ﮐﺪ ﺑﻴﺖ" ﻣﻴﻨﺎﻣﻨﺪ ﺑﻪ هﻤﻴﻦ ﺧﺎﻃﺮ در اداﻣﻪ ﻣﻦ از اﻳ ﻦ واژﻩ اﺳ ﺘﻔﺎدﻩ‬ ‫ﻣﯽ ﮐﻨﻢ.هﺮ ﮐﺪ ﺑﻴ ﺖ را ﻣﻴﺘ ﻮان ﺑ ﻪ ﻃ ﻮر ﻣ ﺴﺘﻘﻞ ﺗﻨﻈ ﻴﻢ ﮐﺮد،ﺑﻨ ﺎﺑﺮاﻳﻦ،ﻋﻨﻮان ﻣﺠﺰاﻳ ﯽ از ﺑ ﺴﺘﻪ ‪ TCP‬ﻣ ﯽ ﺗﻮاﻧ ﺪ‬ ‫ﺷﺎﻣﻞ ﻳﮏ ﻳﺎ ﭼﻨﺪ از ﺷﺶ ﮐﺪﺑﻴﺖ ﺑﺎﺷﺪ ﮐﻪ ﻣﻘﺪار ﺻﻔﺮ و ﻳﮏ دارﻧﺪ.ﻣﻌﻤﻮﻻ ﺗﻨﻬﺎ ﻳﮏ ﻳﺎ دو ﮐﺪ ﺑﻴﺖ ﺑﻪ ﻣﻘ ﺪار ﻳ ﮏ‬ ‫در ﺑﺴﺘﻪ دادﻩ ﺷﺪﻩ ﺗﻨﻈﻴﻢ ﻣﯽ ﺷﻮد. ﺗﮏ ﺗﮏ ﮐﺪ ﺑﻴﺘﻬﺎ داراﯼ ﻣﻔﻬﻴﻢ زﻳﺮ ﻣﯽ ﺑﺎﺷﻨﺪ:‬ ‫‪ : URG‬اﺷﺎرﻩ ﮔﺮ ﻓﻮرﯼ ﻳﺎ ‪ Urgen Pointer‬ﮐﻪ در زﻣﻴﻨﻪ ‪ TCP Header‬ﻣﻬﻢ ﻣﯽ ﺑﺎﺷﺪ.‬ ‫‪ : ACK‬در زﻣﻴﻨ ﻪ ‪ Acknowledment‬ﻣﻬ ﻢ اﺳ ﺖ. اﻳ ﻦ ﺑ ﺴﺘﻪ ﺑ ﺮاﯼ ﺗ ﺼﺪﻳﻖ ﺑ ﺴﺘﻪ ه ﺎﯼ اوﻟﻴ ﻪ اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ‬ ‫ﺷﻮد.‬ ‫‪ : PSH‬اﻳ ﻦ ﻣﻔﻬ ﻮم ﺑ ﻪ ﻣﻌﻨ ﺎﯼ ‪ Push Function‬ﻣ ﯽ ﺑﺎﺷ ﺪ و ﺑ ﺮاﯼ روﺷ ﻦ ﻧﻤ ﻮدن دادﻩ ه ﺎ در ﺳﺮاﺳ ﺮ ﻻﻳ ﻪ‬ ‫‪ TCP‬ﺑﻪ ﮐﺎر ﻣﯽ رود.‬ ‫‪ : RST‬ارﺗﺒﺎﻃﯽ ﮐﻪ ﺑﺎﻳﺪ ﺑﻮاﺳﻄﻪ ﺧﻄﺎ ﻳﺎ ﻧﻘﺺ ﻓﻨﯽ دﻳﮕﺮ از ﻧﻮ ﺗﻨﻈﻴﻢ ﮔﺮدد.‬ ‫‪ : SYN‬ﺳﻴﺴﺘﻢ ﺑﺎﻳﺪ ﺷﻤﺎرﻩ ﻣﺮاﺣﻞ ﮐﺎر را هﻤﺎهﻨﮓ ﻧﻤﺎﻳﺪ.اﻳﻦ ﮐﺪ ﺑﻴﺘﻪ در ﻃ ﻮل اﺳ ﺘﻘﺮار دورﻩ ﮐ ﺎر اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ‬ ‫ﮔﺮدد.‬ ‫‪ : FIN‬دادﻩ هﺎﯼ ﺑﻴﺸﺘﺮﯼ از ﻃﺮف ﺳﺮوﻳﺲ دهﻨﺪﻩ وﺟﻮد ﻧﺪارد.ﺑﻨﺎﺑﺮاﻳﻦ،درورﻩ ﮐﺎر ﺑﺎﻳﺪ از هﻢ ﮔﺴﺴﺘﻪ ﺷﻮد.‬ ‫اهﻤﻴﺖ ﮐﻨﺘﺮل ﺑﻴﺘﻬﺎﯼ ‪ TCP‬وﻗﺘﯽ ﻣﻌﻠﻮم ﻣﯽ ﺷﻮد ﮐ ﻪ ﻣ ﺎ روش ﺷ ﺮوع ﺑ ﻪ ﮐ ﺎر اوﻟﻴ ﻪ ‪ TCP‬را ﻣ ﻮرد ﺗﺤﻠﻴ ﻞ و‬ ‫ﺑﺮرﺳﯽ ﻗﺮار دهﻴﻢ.ﮐﻠﻴﻪ ارﺗﺒﺎﻃﺎت ﻣﻨﻄﻘ ﯽ ‪ TCP‬ﺑ ﺎ اﺳ ﺘﻔﺎدﻩ از اﺗ ﺼﺎل ﺳ ﻪ راﻩ ﺑﺮﻗ ﺮار ﻣ ﯽ ﮔ ﺮدد. و اﺑ ﺰار ﭘﺎﻳ ﻪ‬ ‫ﺑﺮاﯼ اﻧﺠﺎم ﮐﺎ ‪ TCP‬ﺻﻮرت ﻣﯽ ﮔﻴﺮد.اﺗﺼﺎل ﺳﻪ راهﻪ ﺑﻪ ﺳﻴ ﺴﺘﻢ اﺟ ﺎزﻩ ﻣ ﯽ ده ﺪ ﺗ ﺎ دورﻩ ﮐ ﺎر را ﺑ ﺎز ﻧﻤﺎﻳ ﺪ و‬ ‫ﻣﺠﻤ ﻮ ﻋ ﻪ اﯼ از اﻋ ﺪاد ﻣﺮاﺣ ﻞ ﮐ ﺎر را ﺑ ﺮاﯼ ﺑ ﺴﺘﻪ ه ﺎﻳﯽ ﺑﺮﻗ ﺮار ﻣ ﯽ ﮐﻨ ﺪ ﮐ ﻪ از ﻃﺮﻳ ﻖ دورﻩ ﮐ ﺎر اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ‬ ‫ﺷﻮﻧﺪ.‬ ‫ﻓﺰض ﮐﻨﻴﺪ ﮐﻪ دﺳﺘﮕﺎهﯽ ﻣﺜﻞ ‪ A‬داراﯼ دادﻩ هﺎﻳﯽ ﻣﯽ ﺑﺎﺷﺪ ﮐﻪ ﺑﺎﻳﺪ ﺑﻪ ﺳﻴﺴﺘﻤﯽ ﭼ ﻮن ‪ B‬ارﺳ ﺎل ﺷ ﻮﻧﺪ ﺷ ﺎﻳﺪ ‪A‬‬ ‫در ﺣﺎل اﺟﺮاﯼ ﻣﺮورﮔﺮ وب ﺑﺎﺷﺪ و ‪ B‬ﻧﻴﺰ ﺳﺮوﻳﺲ دهﻨ ﺪﻩ وب ﺑﺎﺷ ﺪ.‪ A‬اﺗ ﺼﺎل ﺳ ﻪ راﻩ را ﺑ ﺎ ﺑﺮﻗ ﺮارﯼ ارﺗﺒ ﺎط‬ ‫‪ TCP‬و ﺑﺎ ارﺳﺎل ﺑﺴﺘﻪ اﯼ ﺑﺎ ﮐﺪ ﺑﻴ ﺖ ﻣ ﺴﺎوﯼ ﺑ ﺎ ﻳ ﮏ و ﺷ ﻤﺎرﻩ ﻣﺮاﺣ ﻞ ﮐ ﺎر ﻣ ﺴﺎوﯼ ﺑ ﺎ ﻳ ﮏ ﻣﻘ ﺪار اوﻟﻴ ﻪ )ﮐ ﻪ‬ ‫ﺷﻤﺎرﻩ ﻣﺮﺣﻠﻪ ﮐﺎر اوﻟﻴﻪ ﻧﺎﻣﻴﺪﻩ ﻣﯽ ﺷﻮد( ارﺳﺎل ﻣﯽ ﻧﻤﺎﻳﺪ )ﭼﻮن اﻳﻦ ﺷﻤﺎرﻩ ﻣﺮﺣﻠﻪ ﮐﺎر از ﻃﺮف ‪ A‬ﻣ ﯽ ﺁﻳ ﺪ و‬ ‫ﺁﻧﺮا ‪ ISNA‬ﻣﯽ ﻧﺎﻣﻴﻢ(. اﻳﻦ ﺷﻤﺎرﻩ ﻣﺮﺣﻠﻪ ﮐﺎر اوﻟﻴﻪ ﺑﻪ ﻃﻮر دﻳﻨﺎﻣﻴﮑﯽ ﺑﺎ ﻻﻳ ﻪ ‪ TCP‬ﺗﻌﻴ ﻴﻦ ﻣ ﯽ ﺷ ﻮد و ﺑ ﺮاﯼ‬ ‫اﻳﻦ ارﺗﺒﺎط ﻣﻨﺤﺼﺮ ﺑﻪ ﻓﺮد اﺳﺖ.‬ ‫‪ B‬اﻳﻦ ﺑﺴﺘﻪ ‪ TCP TYN‬را از ﻃﺮف ‪ A‬درﻳﺎﻓ ﺖ ﻣ ﯽ ﮐﻨ ﺪ.اﮔ ﺮ دروازﻩ ﻣﻘ ﺼﺪ از ﻃ ﺮف ﺑ ﺴﺘﻪ ﻧ ﺮم اﻓ ﺰارﯼ ﺑ ﺮ‬ ‫روﯼ ‪ B‬ﺑ ﺎز ﺑﺎﺷ ﺪ.‪ B‬دوﻣ ﻴﻦ ﺑﺨ ﺶ از اﺗ ﺼﺎل ﺳ ﻪ راه ﻪ را ﺑ ﺎ ‪ A‬اﻧﺠ ﺎم ﻣ ﯽ ده ﺪ. ‪ B‬ﺑ ﺴﺘﻪ ﻣﺠﺰاﻳ ﯽ را ﺑ ﺎ دو‬ ‫ﻣﺠﻤﻮﻋ ﻪ ﮐ ﺪ ﺑﻴ ﺖ ‪ ACK‬و‪ SYN‬ﺑ ﻪ ‪ A‬ارﺳ ﺎل ﻣ ﯽ ﮐﻨ ﺪ.در اﻳ ﻦ ﺗ ﮏ ﺑ ﺴﺘﻪ ﭘﺎﺳ ﺦ،‪ B‬زﻣﻴﻨ ﻪ ه ﺎﯼ‬ ‫‪ Acknowledgment Number‬و ‪ Sequence Number‬را ﻧﻴﺰ ﭘﺮ ﻣﯽ ﮐﻨﺪ.ﺑﺎ اﻳ ﻦ ﭘﺎﺳ ﺦ، ‪ B‬ﭘﻴﻐ ﺎﻣﯽ ﺑ ﺎ‬ ‫اﻳ ﻦ ﻣ ﻀﻤﻮن را ارﺳ ﺎل ﻣ ﯽ ﻧﻤﺎﻳ ﺪ.‪، A‬ﻣ ﻦ درﺧﻮاﺳ ﺖ ﺑﺮﻗ ﺮارﯼ دورﻩ ﮐﺎرﺗ ﺎن را و ‪Initial Sequence‬‬ ‫‪ Number A‬را ﺗﺼﺪﻳﻖ ﻣﯽ ﮐﻨﻢ و ﺁﻧﺮا ﺑﺎ اﺳﺘﻔﺎدﻩ از ‪ Initial Sequence Number B‬هﻤﺎهﻨﮓ )‪(SYN‬‬ ‫ﺧﻮاهﻢ ﻧﻤﻮد. ﺑﻨﺎﺑﺮاﻳﻦ ‪ B‬ﺑ ﺴﺘﻪ ‪ SYN-ACK‬را ﺑ ﺎ ‪ ، ISNB‬و هﻤ ﺮاﻩ ﺑ ﺎ ﺗﺎﻳﻴﺪﻳ ﻪ ‪ ISNA‬ارﺳ ﺎل ﺑ ﺴﺘﻪ اﯼ ﺑ ﺎ‬ ‫ﻣﺠﻤﻮﻋﻪ ﮐﺪﺑﻴﺖ ‪ ACK‬و ﻳﮏ ﺗﺎﻳﻴﺪﻳﻪ )‪ (AKC‬و ﺑﻪ ‪ ISNB‬ﮐﺎﻣﻞ ﺧﻮاهﺪ ﻧﻤﻮد.‬ ‫ﺑﺪﻳﻦ ﻃﺮﻳﻖ ،‪ A‬و ‪ B‬از ﮐﺪﺑﻴﺖ هﺎ ﺑﺮاﯼ ﺑﺮﻗﺮارﯼ دورﻩ ﮐﺎر ‪ TCP‬اﺳﺘﻔﺎدﻩ ﮐ ﺮدﻩ اﻧ ﺪ. ﻩ دو ﻃ ﺮف ﺑ ﺎ ﻣﺠﻤﻮﻋ ﻪ‬ ‫ﺷﻤﺎرﻩ ﻣﺮاﺣﻞ ﮐﺎرﯼ ﺗﻮاﻓﻖ ﮐﺮدﻩ اﻧﺪ ﮐﻪ در ارﺗﺒﺎط اﺳﺘﻔﺎدﻩ ﺧﻮاهﺪ ﺷﺪ.ﺗﻤﺎم ﺑﺴﺘﻪ هﺎﻳﯽ ﮐﻪ از ﻃﺮف ‪ A‬ﺑ ﻪ ﺳ ﻤﺖ‬ ‫‪ B‬ﻣﯽ روﻧﺪ ﺑﻪ ﺷﮑﻞ ﻧﻤﻮدﯼ داراﯼ ﺷﻤﺎرﻩ ﻣﺮاﺣﻞ ﮐﺎر ﺑﺎﻻﺗﺮ ﻣﯽ ﺑﺎﺷﻨﺪ و اﻳﻦ ﺷﻤﺎرﻩ در هﺮ ه ﺸﺖ ﺑﻴ ﺖ دادﻩ ه ﺎ‬ ‫ﻳ ﮏ ﺷ ﻤﺎرﻩ زﻳ ﺎد ﻣ ﯽ ﮔ ﺮدد و اﻳ ﻦ دادﻩ ه ﺎ از ﻃ ﺮف ‪ A‬ﺑ ﻪ ﺳ ﻤﺖ ‪ B‬ﻣ ﯽ رود، واز ‪ ISNA‬ﺷ ﺮوع ﻣ ﯽ ﺷ ﻮد.‬ ‫هﻤﭽﻨﻴﻦ،ﺗﻤﺎم ﺑﺴﺘﻪ هﺎﻳﯽ ﮐﻪ از ﻃﺮف ‪ B‬ﺑ ﻪ ﺳ ﻤﺖ ‪ A‬ﺑﺮﻣ ﯽ ﮔﺮدﻧ ﺪ ﺷ ﻤﺎرﻩ ﻣﺮاﺣ ﻞ ﮐ ﺎرﯼ ﺧﻮاهﻨ ﺪ داﺷ ﺖ ﮐ ﻪ از‬

‫-6-‬

‫‪Learning TCP/IP‬‬

‫‪BY: Nasser-Desperado‬‬

‫‪ ISNB‬ﺷﺮوع ﻣﯽ ﺷﻮد و ﺑﺮاﯼ هﺸﺖ ﺑﻴﺖ از دادﻩ هﺎ اﻓﺰاﻳﺶ ﻣﯽ ﻳﺎﺑﺪ.ﺑﻌ ﻼوﻩ، ﺑ ﺴﺘﻪ ه ﺎ ﺷ ﻤﺎرﻩ ﺗ ﺼﺪﻳﻖ ه ﺎﻳﯽ‬ ‫ﺧﻮاهﻨﺪ داﺷﺖ ﮐﻪ ﺑﺮ ﭘﺎﻳﻪ ﺷﻤﺎرﻩ ﻣﺮاﺣﻞ ﮐﺎر ﺑﺴﺘﻪ هﺎﻳﯽ درﻳﺎﻓﺘﯽ ﻣﯽ ﺑﺎﺷﺪ.‬ ‫ﺑﺎ اﻳﻦ ﻣﺒﺎدﻟﻪ و ﺗﻮاﻓﻖ دﻗﻴﻖ در ﺷﻤﺎرﻩ ﻣﺮاﺣﻞ ﮐﺎر،‪ TCP‬اﮐﻨﻮن ﻣ ﯽ ﺗﻮاﻧ ﺪ اﻃﻤﻴﻨ ﺎن ده ﺪ ﮐ ﻪ ﺗﻤ ﺎم ﺑ ﺴﺘﻪ ه ﺎ در‬ ‫دورﻩ ﮐﺎر ﺑﺎ ﻣﺮﺗﺒﻪ ﻣﻨﺎﺳﺐ ﻣﯽ رﺳﻨﺪ.اﮔﺮ دو ﺑﺴﺘﻪ ﻧﺮم اﻓﺰارﯼ در اﻧﺘﻘﺎل ﻣﻌﮑ ﻮس ﮔﺮدﻧ ﺪ )ﺑ ﺮاﯼ ﻣﺜﺎل،ﺑ ﻪ ﺧ ﺎﻃﺮ‬ ‫اﻳﻨﮑﻪ ﺑﺴﺘﻪ ﺑﻌﺪﯼ ﻣﺴﻴﺮ ﮐﻮﺗﺎهﺘﺮﯼ از ﺑﺴﺘﻪ اوﻟﻴﻪ ﻣﯽ رﺳﺪ(،اﻳﻦ ﻻﯼ ‪ TCP‬ﻣﯽ ﺗﻮاﻧﺪ ﻣ ﺸﮑﻞ را ﮐ ﺸﻒ ﻧﻤﺎﻳ ﺪ و‬ ‫ﺑﺴﺘﻪ هﺎ را ﻗﺒﻞ از ﻋﺒﻮر ﺑﻪ ﻧﺮم اﻓﺰار ﮐﺎرﺑﺮدﯼ از ﻧﻮ ﻣﺮﺗﺐ ﻧﻤﺎﻳﺪ.ﺑﻌﻼوﻩ،اﮔﺮ ﺑﺴﺘﻪ اﯼ در ﻃﻮل اﻧﺘﻘﺎم ﮔ ﻢ ﺷ ﻮد.‬ ‫‪ TCP‬ﻣﯽ ﺗﻮاﻧﺪ ﻣﺴﺎﻟﻪ را ﺑﺎ ﻳ ﮏ ﻧﮕ ﺎﻩ در ﺷ ﻤﺎرﻩ ﻣﺮاﺣ ﻞ ﮐ ﺎر و ﺗ ﺼﺪﻳﻖ ﮐ ﺸﻒ ﮐﻨ ﺪ و ﺑ ﺴﺘﻪ ﮔ ﻢ ﺷ ﺪﻩ را از ﻧ ﻮ‬ ‫اﻧﺘﻘﺎل دهﺪ.‬ ‫ﺑﻨﺎﺑﺮاﻳﻦ اﺗﺼﺎل ﺳﻪ راهﻪ و ﺷﻤﺎرﻩ ﻣﺮاﺣﻞ ﮐﺎر ﮐﻪ از ﺁن ﺣﺎﺻ ﻞ ﻣ ﯽ ﺷ ﻮد، اﻣﮑ ﺎن اﻧﺘﻘ ﺎل ه ﺎﯼ ﻣﻨﻄﻘ ﯽ و ﻣﺮﺗ ﺐ‬ ‫ﺷﺪﻩ ﺑﺮاﯼ ‪ TCP‬ﻓﺮاهﻢ ﻣﯽ اورد.‬ ‫در ﺣ ﺎﻟﯽ ﮐ ﻪ ﮐ ﺪﺑﻴﺘﻬﺎﯼ ‪ ACK‬و ‪ SYN‬ﺑ ﻪ ﺷ ﺪت ﺑ ﺮاﯼ ﺑﺮﻗ ﺮارﯼ دورﻩ ﮐ ﺎر اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﺷ ﻮﻧﺪ. ﮐ ﺪﺑﻴﺖ ‪FIN‬‬ ‫ﺑﺮاﯼ ﮔﺴﺴﺘﻦ دورﻩ ﮐﺎر اﺳﺘﻔﺎدﻩ ﻣﯽ ﮔﺮدد.هﺮ ﻃﺮف ﺑﺴﺘﻪ اﯼ را ﺑﺎ ﻣﺠﻤﻮﻋﻪ ﮐﺪ ﺑﻴ ﺖ ‪ FIN‬ارﺳ ﺎل ﻣ ﯽ ﻧﻤﺎﻳ ﺪ ﺗ ﺎ‬ ‫ﻧﺸﺎن دهﺪ ﮐﻪ دورﻩ ﮐﺎر ﺑﺎﻳﺪ ﺧﺎﺗﻤﻪ ﻳﺎﺑﺪ.‬ ‫ﮐﺪ ﺑﻴﺖ ‪ RST‬ﺑﺮاﯼ ﻗﻄﻊ ارﺗﺒﺎﻃﺎت و ﺑﺎز ﻧﻤﻮدن ﺷﻤﺎرﻩ ﻣﺮاﺣﻞ ﮐﺎر اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﺷ ﻮد.اﮔ ﺮ دﺳ ﺘﮕﺎهﯽ ﺑ ﺴﺘﻪ اﯼ‬ ‫در درﻳﺎﻓﺖ ﻧﻤﺎﻳﺪ ﮐﻪ اﻧﺘﻈﺎر درﻳﺎﻓﺖ ﺁن ﻧﺪارد )ﻣﺜﻞ ﺑﺴﺘﻪ اﯼ ﮐﻪ ﺷﺎﻣﻞ ﻣﺠﻤﻮﻋﻪ ﺑﻴﺖ ‪ ACK‬ﻣﯽ ﺑﺎﺷﺪ وﻗﺘﯽ هﻴﭻ‬ ‫دورﻩ ﮐﺎرﯼ ﺑﺮﻗﺮار ﻧﺸﺪﻩ اﺳﺖ(، ﺑﺎ ﺑﺴﺘﻪ اﯼ ﺑﻪ ﺁن ﭘﺎﺳﺦ ﺧﻮاهﺪ داد ﮐﻪ داراﯼ ﻣﺠﻤﻮﻋﻪ ﺑﻴﺖ ‪ RST‬ﻣﯽ ﺑﺎﺷ ﺪ و‬ ‫ﺑﻪ اﻳﻦ ﻣﻀﻨﻮن ﻣﯽ ﺑﺎﺷﺪ ﮐﻪ اﮔﺮ ﻓﮑﺮ ﻣﯽ ﮐﻨﻴﺪ دورﻩ ﮐﺎرﯼ وﺟﻮد دارد،ﺁن را ﺑﺎز ﻧﻤﺎﻳﻴﺪ،ﺑﺮاﯼ اﻳﻨﮑﻪ ﻣﺎﺷﻴﻦ ﻧﻤ ﯽ‬ ‫ﺗﻮاﻧﺪ ﻣﺪ ﻧﻈﺮﺗﺎن ﭼﻪ ﭼﻴﺰﯼ ﻣﯽ ﺑﺎﺷﺪ.‬ ‫ﮐ ﺪ ﺑﻴ ﺖ ه ﺎﯼ ‪ URG‬و ‪ PSH‬ﮐﻤﺘ ﺮ از ﭼﻬ ﺎر ﮐ ﺪﺑﻴﺖ دﻳﮕ ﺮ ﻣ ﻮرد اﺳ ﻨﻔﺎدﻩ ﻗ ﺮار ﻣ ﯽ ﮔﻴﺮﻧ ﺪ.ﮐ ﺪ ﺑﻴ ﺖ ‪ URG‬ﺑ ﻪ‬ ‫ﻣﻌﻨﺎﯼ ﺁن ﻣﯽ ﺑﺎﺷﺪ ﮐﻪ ﺟﺮﻳﺎن دادﻩ هﺎ ﺷﺎﻣﻞ ﻳﮑﺴﺮﯼ دادﻩ هﺎﯼ ﻓﻮرﯼ ﻣﯽ ﺑﺎﺷ ﻨﺪ.اﮔ ﺮ ﮐ ﺪﺑﻴﺖ ‪ URG‬ﻣ ﺴﺎوﯼ ﺑ ﺎ‬ ‫ﻳ ﮏ ﻗ ﺮار ﮔﻴ ﺮد، زﻣﻴﻨ ﻪ ‪ Urgent Pointer‬ﻧ ﺸﺎن ﺧﻮاه ﺪ داد ﮐ ﻪ در ﮐﺠ ﺎﯼ ﺟﺮﻳ ﺎن دادﻩ ه ﺎ، دادﻩ ه ﺎﯼ ﻓ ﻮرﯼ‬ ‫واﻗﻊ ﺷﺪﻩ اﻧﺪ.‪ TCP‬روش ﮐﻨﺘﺮل دادﻩ هﺎﯼ ﻓ ﻮرﯼ را ﺑ ﺎ ﻧ ﺮم اﻓ ﺰار ﮐ ﺎرﺑﺮدﯼ ﺑ ﺮاﯼ ﻃ ﺮف دﻳﮕ ﺮ ارﺗﺒ ﺎط ﻧ ﺸﺎﻧﻪ‬ ‫ﮔﺬارﯼ ﻧﻤﺎﻳﺪ.ﮐﺪ ﺑﻴﺖ ‪ PSH‬ﺑﻪ ﻣﻌﻨﺎﯼ ﺁن اﺳﺖ ﮐﻪ ﻻﻳﻪ ‪ TCP‬ﺑﺎﻳﺪ از درون ﺗﻮدﻩ ﻻﻳﻪ هﺎ ﺳ ﺮﻳﻌﺎ روﺷ ﻦ ﮔ ﺮدد،و‬ ‫ﻧﺒﺎﻳﺪ ﺑﺮاﯼ ارﺳﺎل ﺑﻌﺪﯼ ﻣﻨﺘﻈﺮ ﺑﻤﺎﻧﺪ.‬

‫دﻳﮕﺮ زﻣﻴﻨﻪ هﺎﯼ ﻋﻨﻮان‪: TCP‬‬
‫در زﻣﻴﻨﻪ هﺎﯼ ﻋﻨﻮان ‪ TCP‬ﮐﻪ ﻗﺒﻼ ﺑﺮﺳﯽ ﮐﺮدﻳﻢ،ﭼﻨﺪﻳﻦ زﻣﻴﻨﻪ دﻳﮕﺮ در ﻋﻨﻮان ‪ TCP‬وﺟﻮد دارد .اﻳﻦ زﻣﻴﻨ ﻪ‬ ‫هﺎﯼ اﺿﺎﻓﯽ ﻋﺒﺎرﺗﻨﺪ از:‬ ‫‪ : Data Offset‬اﻳﻦ زﻣﻴﻨﻪ ﺟﺎﻳﯽ را در ﺑﺴﺘﻪ ‪ TCP‬ﻧﺸﺎن ﻣﯽ دهﺪ ﮐﻪ ﻋﻨﻮان ﭘﺎﻳﺎن ﻣﯽ ﻳﺎﺑﺪ و ار ﺁﻧﺠﺎ دادﻩ ه ﺎ‬ ‫ﺷﺮوع ﻣﯽ ﺷﻮﻧﺪ و ﻣﺴﺎوﯼ ﺑﺎ ﻃﻮل ﻋﻨﻮان ‪ TCP‬ﺑﺎ واژﻩ هﺎﯼ 23 ﺑﻴﺘﯽ اﺳﺖ.‬ ‫‪ : Reserved‬اﻳﻦ زﻣﻴﻨﻪ ﺑﺮاﯼ ﻣﺼﺮف ﺑﻌﺪﯼ ذﺧﻴﺮﻩ ﻣﯽ ﺷﻮد.‬ ‫‪ : Window‬اﻳﻦ زﻣﻴﻨﻪ ﺑﺮاﯼ ﮐﻨﺘﺮل ﺷﻤﺎرﻩ هﺎﯼ ﺑﺮﺟﺴﺘﻪ ارﺳﺎل ﺷﺪﻩ ﺑﻴﻦ ﺳﻴﺴﺘﻤﻬﺎ اﺳﺘﻔﺎدﻩ ﻣ ﯽ ﺷ ﻮد. در ه ﺮ‬ ‫ﻃﺮف ارﺗﺒﺎط ﻃﺮﻳﻘﻪ اﯼ ﺑﺮاﯼ ﮐﻨﺘﺮل ﺟﺮﻳﺎن ﺑﺴﺘﻪ هﺎ از دﻳﮕﺮ ﻗﺴﻤﺖ اﻳﺠﺎد ﻣﯽ ﮐﻨﺪﺗﺎ اﻃﻤﻴﻨﺎن دهﺪ ﮐﻪ ﺗﻤﺎم ﺑ ﺴﺘﻪ‬ ‫هﺎ ﺑﻪ ﻃﻮر ﻣﻨﺎﺳﺐ درﻳﺎﻓﺖ ﻣ ﯽ ﺷ ﻮد و ﺑ ﻪ ﺷ ﮑﻞ دﺳﺘﺮﺳ ﯽ ﻗﺒ ﻞ از اﻳﻨﮑ ﻪ ﺑ ﺴﺘﻪ ه ﺎﯼ ﺟﺪﻳ ﺪ ارﺳ ﺎل ﺷ ﻮﻧﺪ،ﻣﻮرد‬ ‫ﺗﺼﺪﻳﻖ ﻗﺮار ﻣﯽ ﮔﻴﺮد.‬ ‫‪ : Checksum‬اﻳﻦ ﺁﺷﮑﺎر ﺳﺎزﯼ ﺧﻄﺎ ﺑﺮاﯼ ﺗﺎﻳﻴﺪ اﻳﻦ ﻣﻄﺎﻟﺐ اﺳﺘﻔﺎدﻩ ﻣﯽ ﮔﺮدد ﮐ ﻪ ﺑ ﺴﺘﻪ ‪) TCP‬ﻋﻨ ﻮان دادﻩ‬ ‫هﺎ( در ﻣﺴﻴﺮش در ﻃﻮل ﺷﺒﮑﻪ ﺧﺮاب ﻧﺸﺪﻩ اﺳﺖ.‬ ‫‪ : Urgent Pointer‬اﻳ ﻦ زﻣﻴﻨ ﻪ داراﯼ اﺷ ﺎرﻩ ﮔ ﺮﯼ در دادﻩ ه ﺎﯼ ﺑ ﺴﺘﻪ ﻣ ﯽ ﺑﺎﺷ ﺪ ﺗ ﺎ ﻧ ﺸﺎن ده ﺪ ﮐ ﻪ در ﮐﺠ ﺎ‬ ‫اﻃﻼﻋﺎﺗﯽ ﮐﻪ ﻓﻮرا ﻣﻮرد ﻧﻴﺎز ﻣﯽ ﺑﺎﺷﺪ،واﻗﻊ ﻣﯽ ﺷﻮد.‬ ‫‪ : Options‬اﻳ ﻦ ﻣﺠﻤﻮﻋ ﻪ از زﻣﻴﻨ ﻪ ه ﺎ ﺑ ﺎ ﻃ ﻮل ﻣﺘﻐﻴ ﺮ ﻣ ﯽ ﺗﻮاﻧﻨ ﺪ اﻃﻼﻋ ﺎت اﺿ ﺎﻓﯽ را در ﻣ ﻮرد ﻻﻳ ﻪ ‪TCP‬‬ ‫ﺑﺘﻮاﻧﺪ ﺗﻨﻬﺎ ﺑﺴﺘﻪ هﺎﯼ ،‪ TCP‬را ﺑﺎ ﺣﺪاﮐﺜﺮ اﻧﺪازﻩ دادﻩ ﺷﺪﻩ ﭘﺸﺘﻴﺒﺎﻧﯽ ﮐﻨﺪ،ﺳﻴﺴﺘﻢ ﻣﯽ ﺗﻮاﻧﺪ اﻳ ﻦ اﻃﻼﻋ ﺎت را در‬ ‫‪ TCP Options‬ﻧﺸﺎن دهﺪ.‬ ‫‪ : Padding‬اﻳﻦ زﻣﻴﻨﻪ ﺷﺎﻣﻞ ﻣﺠﻤﻮﻋﻪ ﺻﻔﺮ ﺑﻴﺖ هﺎﯼ ﮐﺎﻓﯽ اﺳﺖ ﺗﺎ ﻃﻮل ﻋﻨ ﻮان ‪ TCP‬را ﺑ ﻪ ﺣ ﺪﯼ ﮔ ﺴﺘﺮش‬ ‫دهﺪ ﮐﻪ ﺑﻪ ﻣﺮز 23 ﺑﻴﺘﯽ ﺧﺎﺗﻤﻪ ﻳﻠﺒﺪ و در ﻋﻨﻮان داﺧﻞ ﻣﯽ ﺷﻮد ﺗﺎ ﺧﺎﻃﺮ ﻧ ﺸﺎن ﺳ ﺎزد ﮐ ﻪ ﮐﻠﻴ ﻪ ﻣ ﻮارد ﺑ ﻪ ﻃ ﻮر‬ ‫ﻣﺴﺎوﯼ ﻣﺮﺗﺐ ﺷﺪﻩ اﻧﺪ.‬

‫ﭘﺮوﺗﮑﻞ )‪User Datagram Protocol (UDP‬‬
‫در ﺣﺎﻟﯽ ﮐﻪ ﻧﺎم ﮐﻠﯽ ﭘﺮوﺗﮑﻞ ﺑﻪ ﺻﻮرت "‪ "TCP/IP‬ﻧﺎﻣﻴﺪﻩ ﻣﯽ ﺷﻮد،اﻋﻀﺎﯼ دﻳﮕﺮﯼ از اﻳﻦ ﺧﺎﻧﻮادﻩ در ﮐﻨﺎر‬ ‫‪ TCP‬و‪ IP‬وﺟ ﻮد دارﻧ ﺪ.‪ UDP‬ﭘﺮوﺗﮑ ﻞ ﻻﻳ ﻪ ‪ Transport‬دﻳﮕ ﺮﯼ اﺳ ﺖ ﮐ ﻪ ﻣ ﯽ ﺗﻮاﻧ ﺪ ﺑ ﺮ ﺑ ﺎﻻﯼ ‪ IP‬ﻗ ﺮار‬ ‫ﮔﻴ ﺮ.‪ TCP‬و‪ UDP‬ﺑ ﻪ ﻣﺜ ﺎل دو ﭘ ﺴﺮ ﻋﻤ ﻮ ﻣ ﯽ ﺑﺎﺷ ﻨﺪ.‪ TCP‬ﺑ ﻪ ﺗﻮﺟ ﻪ ﺑﻴ ﺸﺘﺮﯼ ﻧﻴ ﺎز دارد وﺑ ﺎ ﻧ ﺎم ﺧ ﺎﻧﻮادﮔﯽ‬

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‫‪Learning TCP/IP‬‬

‫‪BY: Nasser-Desperado‬‬

‫اﺳﺘﻔﺎدﻩ ﻣﯽ ﺷﻮد.اﻣﺎ ‪ UDP‬هﻨﻮز ﭘﺎﻳ ﻪ ﺑ ﺴﻴﺎرﯼ از ﻧ ﺮم اﻓ ﺰار ه ﺎﯼ ﮐ ﺎرﺑﺮدﯼ ﻣﻬ ﻢ ﻣ ﯽ ﺑﺎﺷ ﺪ.در اﻧﺘﺨ ﺎب اﻧﺘﻘ ﺎل‬ ‫دادﻩ هﺎ ﺑﺎ اﺳﺘﻔﺎدﻩ از ‪ TCP‬ﻳﺎ ‪، UDP‬ﺗﻮﺳﻌﻪ دهﻨﺪ ﻧﺮم اﻓﺰار ﮐﺎرﺑﺮدﯼ ﺑﺎﻳ ﺪ در ﻧﻈ ﺮ داﺷ ﺘﻪ ﺑﺎﺷ ﺪ ﮐ ﻪ ﭼ ﻪ ﻧ ﺮم‬ ‫اﻓﺰار ﮐﺎرﺑﺮدﯼ از ﻻﻳ ﻪ ‪ Transport‬ﻣ ﻮرد ﻧﻴ ﺎز ﻣ ﯽ ﺑﺎﺷ ﺪ.ﺑ ﺴﺘﻪ دادﻩ ﺷ ﺪﻩ و ﺟﺮﻳ ﺎن ارﺗﺒ ﺎط،ﻣﻌﻤﻮﻻ ‪ TCP‬ﻳ ﺎ‬ ‫‪ UDP‬ﻣ ﯽ ﺑﺎﺷ ﺪ. و ﻧﻤ ﯽ ﺗ ﻮان ه ﺮ دو ﭘﺮوﺗﮑ ﻞ را ﺑ ﻪ ﻃ ﻮر هﻤﺰﻣ ﺎن ﺑ ﻪ ﮐ ﺎرﺑﺮد.ﺳ ﺮوﻳﺲ ه ﺎﻳﯽ ﮐ ﻪ از ‪UDP‬‬ ‫اﺳﺘﻔﺎدﻩ ﻣﯽ ﻧﻤﺎﻳﻨﺪ داراﯼ ﻧﺮم اﻓﺰارهﺎﯼ ﮐﺎرﺑﺮدﯼ ﺻﻮﺗﯽ و ﺗﺼﻮﻳﺮﯼ در ﺣﺎل ﺟﺮﻳﺎن و هﻤﻮارﻩ ﺑﺎ ﭘﺎﺳﺦ و ﭘﺮس‬ ‫ﺟﻮ هﺎ ) ‪ (Domain Name Service KNS‬ﻣﯽ ﺑﺎﺳﻨﺪ.ﺑ ﺮاﯼ اﻳﻨﮑ ﻪ ﺑﺪاﻧﻴ ﺪ ﭼ ﺮا اﻳ ﻦ ﺳ ﺮوﻳﺲ ه ﺎ ﺑ ﺮ ﻣﺒﻨ ﺎﯼ‬ ‫‪ UDP‬ﻣﯽ ﺑﺎﺷﻨﺪ،ﺧﺼﻮﺻﻴﺎت ‪ UDP‬را ﺑﺎ ﺟﺰﺋﻴﺎت ﺑﻴﺸﺘﺮ ﻣﻮرد ﺗﺤﻠﻴﻞ ﻗﺮار ﻣﯽ دهﻢ.‬ ‫‪ UDP‬ﻋﺎرﯼ از ارﺗﺒ ﺎط ﻣ ﯽ ﺑﺎﺷ ﺪ ﻳﻌﻨ ﯽ ﭘﺮوﺗﮑﻞ،ﺷ ﮑﻞ و ﻧ ﻮع ارﺗﺒ ﺎط را ﻧﻤ ﯽ داﻧ ﺪ و ه ﻴﭻ ﻣﻔﻬ ﻮﻣﯽ از ﺷ ﺮوع‬ ‫دورﻩ ﮐﺎر،ﺗﺼﺪﻳﻖ،از هﻢ ﮔﺴﻴﺨﺘﮕﯽ ﻳﺎ ﻣﻮارد ﻣﺸﺎﺑﻪ دﻳﮕﺮ ﻧﺪارد.ﺑﻌﻼوﻩ،ﺧﻮد ‪ UDP‬ﺑﺴﺘﻪ هﺎﯼ از دﺳﺖ رﻓﺘﻪ را‬ ‫اﻧﺘﻘﺎل ﻧﻤﯽ دهﺪ، و ﻳﺎ ﺁﻧﻬﺎ را در ﻣﺮﺗﺒﻪ ﻣﻨﺎﺳﺐ ﻗﺮار ﻧﻤﯽ دهﺪ.ﺑﻨﺎﺑﺮاﻳﻦ ،اﮔﺮ ﺑﺴﺘﻪ 1،ﺑﺴﺘﻪ 2 و ﺑﺴﺘﻪ 3 ﻓﺮﺳ ﺘﺎدﻩ‬ ‫ﺷﻮﻧﺪ،ﻣﻘﺼﺪ ﻣﻤﮑﻦ اﺳﺖ ﺑﺴﺘﻪ 2 ،ﺑﺴﺘﻪ 1 و ﮐﭙ ﯽ دﻳﮕ ﺮﯼ از ﺑ ﺴﺘﻪ 1 را درﻳﺎﻓ ﺖ ﮐﻨ ﺪ.ﺑ ﺴﺘﻪ 3 ﮔ ﻢ ﺷ ﺪﻩ اﺳ ﺖ،و‬ ‫ﺑﺴﺘﻪ 1 ﺑﻪ ﻃﺮﻳﻘﯽ دوﺑﺎرﻩ ﻓﺮﺳﺘﺎدﻩ ﺷﺪﻩ اﺳﺖ.‪ UDP‬ذاﺗﺎ ﻏﻴﺮ ﻗﺎﺑﻞ اﻃﻤﻴﻨﺎن اﺳﺖ و ﻣﻤﮑﻦ اﺳ ﺖ ﺑ ﺴﺘﻪ ه ﺎﻳﯽ را‬ ‫ﮔﻢ ﻧﻤﺎﻳﺪ ﻳ ﺎ ﺧ ﺮاب ﺁﻧﻬ ﺎ را ﺧ ﺮاب ﮐﻨ ﺪ.ﺑﻌ ﻀﯽ از ﻧ ﺮم اﻓﺰاره ﺎﯼ ﮐ ﺎر ﺑ ﺮدﯼ ﺑ ﺮاﯼ درﻳﺎﻓ ﺖ ﺑ ﺴﺘﻪ ه ﺎﻳﯽ از ﻃﺮﻳ ﻖ‬ ‫ﺷﺒﮑﻪ ﺑﺴﻴﺎر ﺟﺎﻟﺐ ﻣﯽ ﺑﺎﺷﺪ،و ﺑﻪ اﻃﻤﻴﻨﺎن ﺑﺴﻴﺎر زﻳﺎدﯼ ﻧﻴﺎز ﻧﺪارﻧﺪ.ﭼﻨﻴﻦ ﻧﺮم اﻓﺰارهﺎﯼ ﮐ ﺎر ﺑ ﺮدﯼ اﺗ ﺼﺎل ﺳ ﻪ‬ ‫راهﻪ،ﺷﻤﺎرﻩ ﻣﺮاﺣﻞ ﮐﺎر در هﺮ ﺑﺴﺘﻪ،ﺗﺎﻳﻴﺪ و ﻏﻴﺮﻩ ﻧﻤ ﯽ ﺧﻮاهﻨ ﺪ.در ﻋﻮض،ﺑﻌ ﻀﯽ از ﻧ ﺮم اﻓﺰاره ﺎﯼ ﮐ ﺎرﺑﺮدﯼ‬ ‫ﺑﻪ ﺳﺎدﮔﯽ و ﺳﺮﻋﺖ ﻧﻴﺎز دارﻧﺪ.‬ ‫ﻳﻪ ﺳﻮال : ﭼﻪ ﻧﻮع ﻧﺮم اﻓﺰارهﺎﯼ ﮐﺎرﺑﺮدﯼ داراﯼ اﻳ ﻦ ﻣﻠﺰوﻣ ﺎت ﻣ ﯽ ﺑﺎﺷ ﻨﺪ؟ﻏﺎﻟﺒﺎ ﻧ ﺮم اﻓﺰاره ﺎﯼ ﮐ ﺎرﺑﺮدﯼ ﮐ ﻪ‬ ‫دادﻩ هﺎﻳﯽ را ﺑﺮاﯼ ﮔﻮش و ﭼﺸﻢ اﻧﺴﺎن اﻧﺘﻘﺎل ﻣﯽ دهﻨﺪ،ﻣﺜﻞ دادﻩ هﺎﯼ ﭘﻴﻮﺳﺘﻪ ﺻﻮﺗﯽ ﻳ ﺎ ﺗ ﺼﻮﻳﺮﯼ از اﻳ ﻦ ﻧ ﻮع‬ ‫ﻣﯽ ﺑﺎﺷﻨﺪ.درﺣﺎﻟﯽ ﮐﻪ ﭼﺸﻢ وﮔﻮﺷﺘﺎن را ﺧﻮاهﻴﺪ ﺑﺴﺖ،اﮔﺮ ﺑ ﺴﺘﻪ اﯼ ﮔ ﺎﻩ و ﺑﻴﮕ ﺎﻩ از دﺳ ﺖ ﺑﺮود،اﺣﺘﻤ ﺎﻻ ﺑﻴ ﺸﺘﺮ‬ ‫وﻓﺘﯽ ﻣﺘﻮﺟﻪ ﻣﯽ ﺷﻮﻳﺪ ﮐﻪ ﺗﻤﺎم ﺑﺴﺘﻪ اﯼ ﮔﺎﻩ و ﺑﻴﮕﺎﻩ از دﺳﺖ ﺑﺮود،اﺣﺘﻤ ﺎﻻ ﺑﻴ ﺸﺘﺮ وﻗﺘ ﯽ ﻣﺘﻮﺟ ﻪ ﻣ ﯽ ﺷ ﻮﻳﺪ ﮐ ﻪ‬ ‫ﺗﻤﺎم ﺑﺴﺘﻪ هﺎ ﺑﺎ ﭘﺮدازش ﺳﻨﮕﻴﻦ و ﺑﻪ ﮐﻨﺪﯼ ارﺳﺎل ﻣﯽ ﺷﻮﻧﺪ.ﺑﻌﻼوﻩ ﺑﻌﻀﯽ از ﻧﺮم اﻓﺰارهﺎﯼ ﭘﺎﺳﺨﯽ و ﭘﺮس و‬ ‫ﺟ ﻮﻳﯽ از ‪ ، UDP‬ﻋﻠ ﯽ اﻟﺨ ﺼﻮص ‪ DNS‬اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﮐﻨﻨ ﺪ.وﻗﺘ ﯽ ﺑ ﻪ ﺁدرس ﺷ ﺒﮑﻪ ﺑ ﺮاﯼ ﻧ ﺎم ﻗﻠﻤ ﺮو ﺧﺎﺻ ﯽ‬ ‫ﻧﮕﺎهﯽ ﻣﯽ اﻧﺪازﻳ ﺪ.‪ DNS‬ﺁدرس ‪ www.skodis.com‬را ﺑ ﻪ ﺷ ﻤﺎ ﻧ ﺸﺎن ﻣ ﯽ ده ﺪ.وﺑ ﺴﺘﻪ ‪ UDP‬ﻣﺠﺰاﻳ ﯽ در‬ ‫ﭘﺎﺳﺦ درﻳﺎﻓ ﺖ ﻣ ﯽ ﮔ ﺮدد ﻣ ﺜﻼ ﺑ ﺴﺘﻪ اﯼ ﮐ ﻪ اﻇﻬ ﺎر ﻣ ﯽ ﻧﻤﺎﻳ ﺪ ﮐ ﻪ ﺁدرس 3.14.12.01 ﻣ ﯽ ﺑﺎﺷ ﺪ اﻳ ﻦ ﻧ ﺮم اﻓ ﺰار‬ ‫ﮐﺎرﺑﺮدﯼ ﺑﻪ ﻣﻮارد اﺿﺎﻓﯽ هﻤﺮاﻩ ﺑﺎ ﺑﺮﻗﺮارﯼ ارﺗﺒﺎط ﺑﺎ اﺳﺘﻔﺎدﻩ از اﺗﺼﺎل ﺳﻪ راه ﻪ ﺑ ﺮاﯼ ارﺳ ﺎل ﭘ ﺮس وﺟ ﻮ و‬ ‫درﻳﺎﻓﺖ ﭘﺎﺳﺦ ﻧﻴﺎز ﻧﺪارﻧﺪ.‬ ‫‪ UDP‬داراﯼ ﺷﻤﺎرﻩ دروازﻩ هﺎﯼ 61 ﺑﻴﺘﯽ ﻣ ﯽ ﺑﺎﺷ ﺪ.ﺑﻨ ﺎﺑﺮاﻳﻦ 53556 دروازﻩ ‪ UDP‬اﺣﺘﻤ ﺎﻟﯽ وﺟ ﻮد دارد.در‬ ‫‪، TCP‬دادﻩ ه ﺎ از ﻳ ﮏ دروازﻩ ﺳﻴ ﺴﺘﻢ ﻣﺒ ﺪا ﺑﻴ ﺮون ﻣ ﯽ ﺁﻳﻨ ﺪ )دروازﻩ ﻣﺒ ﺪا‪، (UDP‬و ﺑ ﻪ دروازﻩ اﯼ ﮐ ﻪ در‬ ‫ﺳﻴﺴﺘﻢ ﻣﻘﺼﺪ ﺧﺘﻢ ﻣﯽ ﺷﻮﻧﺪ)دروازﻩ ﻣﻘﺼﺪ ‪، ( UDP‬ﻳﮑﯽ از ﻣﺘﺪاول ﺗ ﺮﻳﻦ ﺳ ﺮوﻳﺲ ه ﺎﯼ ‪ UDP‬ﮐ ﻪ ﺑ ﻪ ﻃ ﻮر‬ ‫وﺳﻴﻊ اﺳﺘﻔﺎدﻩ ﻣ ﯽ ﺷ ﻮد)‪ (DNS‬ﻣﻨﺘﻈ ﺮ درﻳﺎﻓ ﺖ ﭘﺎﺳ ﺦ از ﭘ ﺮس وﺟﻮه ﺎﯼ ‪ DNS‬در دروازﻩ 35 و ‪ UDP‬ﻣ ﯽ‬ ‫ﻣﺎﻧﺪ.دﻳﮕﺮ ﺳﺮوﻳﺲ هﺎﯼ ‪ UDP‬ﻋﺒﺎرﺗﻨﺪ از :‬ ‫96 ‪Trivial File Transports Protocol (TFTP),UDP Port‬‬ ‫161 ‪Simple Network Management Protocol (SNMP) ,UDP Port‬‬ ‫)‪RealPlayer (audio/video‬‬

‫ﺁﻳﺎ ‪ UDP‬اﻳﻤﻨﯽ ﮐﻤﺘﺮﯼ از ‪ TCP‬دارد؟‬
‫ﺑﺪون اﺗﺼﺎل ﺳﻪ راهﻪ،ﺁﻳﺎ ‪ UDP‬اﻳﻤﻨﯽ ﮐﻤﺘﺮﯼ از ‪ TCP‬دارد؟ ﺑ ﻪ ﻋﺒ ﺎرت دﻳﮕﺮ،ﺁﻳ ﺎ ﻧ ﺮم اﻓ ﺰار ه ﺎﯼ ﮐ ﺎرﺑﺮدﯼ‬ ‫ﮐﻪ در ‪ UDP‬اﺟﺮا ﻣﯽ ﺷﻮﻧﺪ ﺳ ﺨﺖ ﺗ ﺮ ازﺳ ﺮوﻳﺲ ه ﺎﯼ ‪ TCP‬اﻳﻤ ﻦ ﻣ ﯽ ﺷ ﻮد ﮐ ﻪ اﻟﺒﺘ ﻪ، ﺑ ﺮاﯼ اﺟ ﺰاﯼ ﺷ ﺒﮑﻪ‬ ‫درﮎ و ردﮔﻴﺮﯼ ﺁﻧﭽﻪ ﮐﻪ ﻧﺮم اﻓﺰار ﮐﺎرﺑﺮدﯼ ﺑﺎ اﺳﺘﻔﺎدﻩ از ‪ UDP‬ﺻﻮرت ﻣ ﯽ ﮔﻴ ﺮد )ﻣﺜ ﻞ دﻳ ﻮارﻩ ه ﺎﯼ ﺁﺗ ﺶ و‬ ‫ﻣﺴﻴﺮ ﻳﺎﺑﻬﺎ( ﺑﺮﺧﻼف ‪ TCP‬ﺳﺨﺖ ﺗﺮ و ﻣﺸﮑﻞ ﺗﺮ ﻣﯽ ﺑﺎﺷﺪ.ﺑﻪ ﺧﺼﻮص ،ﮐﺪﺑﻴﺖ ه ﺎﯼ ‪ TCP‬و ﺷ ﻤﺎرﻩ ﻣﺮاﺣ ﻞ‬ ‫اﺷﺎرﻩ هﺎﯼ ﺑﺴﻴﺎر زﻳﺎدﯼ را ﺑﻪ دﻳﻮارﻩ هﺎﯼ ﺁﺗﺶ و ﻣﺴﻴﺮ ﻳﺎﺑﻬﺎ داﻧﺪ.ﺑﻨﺎﺑﺮاﻳﻦ ﺑﺎ ﺁﻧﻬﺎ راﺣﺘﺘﺮ ﻣﯽ ﺗﻮان ارﺗﺒﺎط را‬ ‫ﮐﻨﺘﺮل ﮐﺮد.ﺟﺰﺋﯽ از ﺷﺒﮑﻪ از زﻣﺎن ﺑﺮﻗﺮارﯼ دورﻩ ﮐﺎر ‪ TCP‬اﻃﻼع ﻻزم دارد،ﺑﺮاﯼ اﻳﻨﮑﻪ ﻣﯽ ﺗﻮاﻧﺪ ﺑﻪ ﮐ ﺪﺑﻴﺖ‬ ‫‪ SYN‬رﺟﻮع ﻧﻤﺎﻳﺪ ﺑﻌﻼوﻩ ﻣﺴﻴﺮ ﻳ ﺎب ﻳ ﺎ دﻳ ﻮارﻩ ﺁﺗ ﺶ از زﻣ ﺎن ﺗ ﺼﺪﻳﻖ ﺑ ﺴﺘﻪ ﻳ ﺎ دورﻩ ﮐ ﺎرﯼ ﮐ ﻪ ﮔﺴ ﺴﺘﻪ ﺷ ﺪﻩ‬ ‫اﺳﺘﻮﺑﺎ ﺳﺎﺧﺖ ﮐﺪﺑﻴﺖ هﺎ و ﺷﻤﺎرﻩ ﻣﺮاﺣﻞ ﮐﺎر اﻃﻼع دارد.‬ ‫ﺑﺎ ﻧﺒﻮد ﮐﺪﺑﻴﺘﻬﺎ و ﻣﺮاﺣﻞ ﮐﺎر ‪ ، UDP‬ردﻳﺎﺑﯽ ﺟ ﺎﻳﯽ ﮐ ﻪ دو ﺳﻴ ﺴﺘﻢ ﺑ ﺎ ه ﻢ در ارﺗﺒ ﺎط ﻣ ﯽ ﺑﺎﺷﻨﺪ،ﺑ ﺴﻴﺎر ﻣ ﺸﮑﻠﺘﺮ‬ ‫اﺳﺖ.ﺑ ﺴﺘﻪ ه ﺎﯼ ‪ UDP‬ﮐ ﻪ از اﻳﻨﺘﺮﻧ ﺖ ﺣﺎﺻ ﻞ ﻣ ﯽ ﺷ ﻮﻧﺪ،ﻣﯽ ﺗﻮاﻧﻨ ﺪ ﭘﺎﺳ ﺦ ه ﺎﻳﯽ ﺑ ﺮاﯼ ﺳ ﺮوﻳﺲ ه ﺎﯼ ﻣﻨﻄﻘ ﯽ‬ ‫ﺑﺎﺷﻨﺪ،ﻳﺎ ﻣﯽ ﺗﻮاﻧﻨﺪ اﺳﮑﻦ هﺎﻳﯽ ﺑﺎﺷﻨﺪ ﮐﻪ از روﯼ ﺳﻮءﻧﻴﺖ ﺻﻮذت ﻣﯽ ﮔﻴﺮد.‬ ‫ﺑﺎ ﺟﺴﺘﺠﻮﯼ ﺳﺎدﻩ در ﻋﻨﻮان ‪ ،UDP‬ﻣﯽ ﺗﻮان دﻳﺪ هﻴﭻ ﻃﺮﻳﻘﯽ وﺟﻮد ﻧﺪارد ﮐﻪ ﺑﮕﻮﻳﻴﻢ ﺑﺴﺘﻪ ﻧﺮم ﻓ ﺎزارﯼ، ﻗﻄ ﻪ‬ ‫ﺷﺮوع ارﺗﺒﺎط ﻳ ﺎ ﭘﺎﺳ ﺦ ﻣ ﯽ ﺑﺎﺷ ﻨﺪ.ﺑﻨ ﺎﺑﺮاﻳﻦ ﮐﻨﺘ ﺮل ‪ UDP‬از ﻟﺤ ﺎظ اﻳﻤﻨ ﯽ ﺑ ﺴﻴﺎر ﻣ ﺸﮑﻠﺘﺮ از ﮐﻨﺘ ﺮل ‪ TCP‬ﻣ ﯽ‬ ‫ﺑﺎﺷﺪ.‬

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‫‪Learning TCP/IP‬‬

‫‪BY: Nasser-Desperado‬‬ ‫ﺧﻮب در اداﻣﻪ درﺑﺎرﻩ دﻳﻮارﻩ هﺎﯼ ﺁﺗﺶ ﺗﻮﺿﻴﺢ ﺧﻮاهﻢ داد.‬

‫ﭘﺮوﺗﮑﻞ ‪ IP‬و ﭘﺮوﺗﮑﻞ ﭘﻴﻐﺎم ﮐﻨﺘﺮل اﻳﻨﺘﺮﻧﺖ )‪(ICMP‬‬
‫وﻓﺘ ﯽ ﻻﻳ ﻪ ‪ TCP‬ﻳ ﺎ ‪ UDP‬ﺑ ﺴﺘﻪ اﯼ را ﺗﻮﻟﻴ ﺪ ﻣ ﯽ ﻧﻤﺎﻳﻨ ﺪ،اﻳﻦ ﺑ ﺴﺘﻪ ﺑﺎﻳ ﺪ از ﻃﺮﻳ ﻖ ﺷ ﺒﮑﻪ ارﺳ ﺎل ﺷ ﻮﻧﺪﻩ ﻻﻳ ﻪ‬ ‫‪ ، (TCP or UDP) Transport‬ﺑﺴﺘﻪ را ﺑ ﻪ ﻻﻳ ﻪ ‪ Network‬ﻣ ﻮرد اﺳ ﺘﻔﺎدﻩ اﻣ ﺮوزﯼ ﻣ ﯽ ﺑﺎﺷ ﺪ، و ﺑ ﺮاﯼ‬ ‫ﺗﻤﺎم ﺗﺮاﻓﻴﮑﻬﺎﻳﯽ ﮐﻪ در ﺣﺎل ﺣﺮﮐﺘﺎز ﻃﺮﻳﻖ اﻳﻨﺘﺮﻧﺖ ﻣﯽ ﺑﺎﺷﻨﺪ.اﺳﺘﻔﺎدﻩ ﻣﯽ ﺷﻮد. در هﻨﮕﺎم درﻳﺎﻓ ﺖ اﻃﻼﻋ ﺎت از‬ ‫ﻻﻳﻪ ‪ ، Transport‬ﻻﻳﻪ ‪ IP‬ﻋﻨﻮاﻧﯽ را ﺗﻮﻟﻴﺪ ﻣﯽ ﮐﻨﺪ ﮐ ﻪ ﺷ ﺎﻣﻞ ﺁدرس ‪ IP‬ﻣﻘ ﺼﺪ و ﻣﺒ ﺪا ﻣ ﯽ ﺑﺎﺷ ﺪ.ﻋﻨ ﻮان ﺑ ﻪ‬ ‫ﺟﻠﻮﯼ ﺑﺴﺘﻪ ‪ TCP‬اﻟﺼﺎق ﻣﯽ ﺷﻮد ﺗﺎ ﺑﺴﺘﻪ ‪ IP‬ﻓﺎﺻﻠﻪ اﯼ را اﻳﺠﺎد ﻧﻤﺎﻳﺪ،ﮐﻪ ﺑﺮاﯼ ﺣﻤﻞ ﮐﻞ ﻣﺤﺘﻮﻳﺎت از ﻃﺮﻳ ﻖ‬ ‫ﺷﺒﮑﻪ اﺳﺘﻔﺎدﻩ ﺧﻮاهﻨﺪ ﺷﺪ )ﻋﻨﻮان ‪ ، IP‬ﻋﻨﻮان ‪ ، TCP‬و دادﻩ هﺎﯼ ﺗﺮاز ﻧﺮم اﻓﺰار ﮐﺎرﺑﺮدﯼ(.‬

‫ﺷﺒﮑﻪ هﺎﯼ ﻧﺎﺣﻴﻪ ﻣﺤﻠﯽ و ﻣﺴﻴﺮﻳﺎب هﺎ‬
‫ﺑﺮاﯼ اﻳﻨﮑﻪ ﺑﺪاﻧﻴﻢ ‪ IP‬ﭼﻄﻮر ﮐﺎر ﻣﯽ ﮐﻨﺪ، ﻻزم اﺳ ﺖ ﮐﻤ ﯽ وﻗ ﺖ ﺑﮕ ﺬارﻳﻢ و روش ﺳ ﺎﺧﺘﻪ ﺷ ﺪن ﺷ ﺒﮑﻪ را درﮎ‬ ‫ﮐﻨﻴﻢ.هﺪف از ‪ IP‬ﻣﺤﻞ ﺑﺴﺘﻪ هﺎﯼ ﻣﺘﺪاوم اﻧﺘﻘﺎل ﻳﺎﻓﺘﻪ از ﻃﺮﻳﻖ ﺷ ﺒﮑﻪ ﻣ ﯽ ﺑﺎﺷ ﺪ.اﻣ ﺎ در واﻗ ﻊ ﺷ ﺒﮑﻪ ﭼ ﻪ ﭼﻴ ﺰﯼ‬ ‫ﻣ ﯽ ﺑﺎﺷ ﺪ؟ ﺷ ﺒﮑﻪ ه ﺎﯼ ﮐﺎﻣ ﻞ از ﺑﻠ ﻮﮎ ه ﺎﯼ ﺳ ﺎﺧﺘﺎرﯼ ﭘﺎﻳ ﻪ ﺳ ﺎﺧﺘﻪ ﻣ ﯽ ﺷ ﻮﻧﺪ ﮐ ﻪ ﺷ ﺒﮑﻪ ه ﺎﯼ ﻧﺎﺣﻴ ﻪ ﻣﺤﻠ ﯽ‬ ‫)‪ (LAN‬ﻧﺎﻣﻴﺪﻩ ﻣ ﯽ ﺷ ﻮﻧﺪ. ‪ LAN‬ﺑﻄ ﻮر ﺳ ﺎدﻩ دﺳ ﺘﻪ اﯼ از ﮐ ﺎﻣﭙﻴﻮﺗﺮ ه ﺎﯼ ﻣﺘ ﺼﻞ ﺑ ﻪ ه ﻢ ﺑ ﻪ اﺳ ﺘﻔﺎدﻩ از ﮐﻠﻴ ﺪ‬ ‫ﻣﺮﮐﺰﯼ اﺳﺖ، ﮐ ﻪ ﻣ ﺴﻴﺮ ﻳ ﺎب ه ﺎﻳﯽ ﺟ ﺪا از ﺳﻴ ﺴﺘﻢ ه ﺎ ﻧﺪارﻧ ﺪ. هﻤ ﺎﻧﻄﻮر ﮐ ﻪ ﻧ ﺎم ﺁﻧﻬ ﺎ ﺑﻴ ﺎن اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﻧﻤﺎﻳ ﺪ،‬ ‫‪ LAN‬ﺑﻄ ﻮر ﻧﻤﻮﻧ ﻪ و از ﻟﺤ ﺎظ ﺟﻐﺮاﻓﻴ ﺎﻳﯽ ﮐﻮﭼ ﮏ ﻣ ﯽ ﺑﺎﺷ ﻨﺪ،ﻣﻌﻤﻮﻻ در ﻳ ﮏ ﺳ ﺎﺧﺘﻤﺎن ﻳ ﺎ در ﻳ ﮏ ﻣﺤ ﻴﻂ‬ ‫داﻧﺸﮕﺎهﯽ ﮐﻮﭼﮏ ﻣﻮرد ﮐﺎرﺑﺮد دارﻧﺪ.‬ ‫ﺷﺒﮑﻪ هﺎﯼ ﻣﺤﻠﯽ )‪ (LANs‬ﺑﺎ ﻳﮑﺪﻳﮕﺮ ﺑﻪ اﺳﺘﻔﺎدﻩ از ﻣﺴﻴﺮﻳﺎب ه ﺎ ﻣﺘ ﺼﻞ ﻣ ﯽ ﺷ ﻮﻧﺪ.ﮐ ﺎر ﻣ ﺴﻴﺮﻳﺎب ﺟ ﺎ ﺑ ﻪ ﺟ ﺎ‬ ‫ﮐﺮدن ﺑﺴﺘﻪ هﺎ ﺑﻴﻦ ﺷﺒﮑﻪ هﺎﯼ ﻣﺤﻠﯽ اﺳﺖ، در ﻧﺘﻴﺠﻪ ﺑﺪﻳﻦ ﺗﺮﺗﻴ ﺐ ﺷ ﺒﮑﻪ ﺑﺰرﮔ ﯽ را اﻳﺠ ﺎد ﻣ ﯽ ﮐﻨ ﺪ.ﻳ ﮏ ﻳ ﺎ ﭼﻨ ﺪ‬ ‫ﭘﺮوﺗﮑﻞ ﻻﻳﻪ ‪ ،Network‬دادﻩ ه ﺎ را ﺑ ﻪ ﻃ ﻮر ﻣ ﺪاوم از ﻃﺮﻳ ﻖ ﺷ ﺒﮑﻪ، و از ﻳﺎراﻧ ﻪ ﮐ ﺎرﺑﺮ، از ﻃﺮﻳ ﻖ ﻳﮑ ﺴﺮﯼ‬ ‫ﻣﺴﻴﺮ ﻳﺎﺑﻬﺎ ، ﺑﻪ ‪ LAN‬ﻧﻬﺎﻳﯽ و ﺑﻪ ﻣﻘﺼﺪ ﻧﻬﺎﻳﯽ ﻣﻨﺘﻘﻞ ﻣﯽ ﮐﻨﺪ. اﻟﺒﺘﻪ، ﺑﺴﻴﺎرﯼ از ﺳﻴﺴﺘﻤﻬﺎ ﺑﻪ ﻃﻮر ﻣﺴﺘﻘﻴﻢ ﺑﻪ‬ ‫ﻣﺴﻴﺮﻳﺎﺑﻬﺎ ﺑﺎ ﻳﮑﺪﻳﮕﺮ ﺑﺎ اﺳﺘﻔﺎدﻩ از اﺗﺼﺎﻻت ﻧﻘﻄﻪ ﺑ ﻪ ﻧﻘﻄ ﻪ ﻣﺘ ﺼﻞ ﻣ ﯽ ﮔﺮدﻧ ﺪ.ﺧ ﻮد اﻳﻨﺘﺮﻧ ﺖ ﭼﻴ ﺰﯼ ﻧﻴ ﺴﺖ اﻣ ﺎ‬ ‫ﻣﺠﻤﻮﻋﻪ ﺣﺎﺻﻠﻪ اﯼ اﺳﺖ از ﺷﺒﮑﻪ هﺎﯼ ﻣﺤﻠﯽ و اﺗﺼﺎﻻت ﻧﻘﻄﻪ ﺑﻪ ﻧﻘﻄﻪ ﺑﺎ ﻳﮑﺪﻳﮕﺮ ﮐﻪ ﺑﺎ اﺳ ﺘﻔﺎدﻩ از دﺳ ﺘﻪ اﯼ‬ ‫از ﻣﺴﻴﺮ ﻳﺎﺑﻬﺎ ﺑﻪ هﻢ ﻣﺘﺼﻞ ﻣﯽ ﺷﻮﻧﺪ.‬

‫ﺁدرﺳﻬﺎﯼ ‪IP‬‬
‫ﺁدرس هﺎﯼ ‪ IP‬دﺳﺘﮕﺎﻩ ﺧﺎﺻﯽ را ﺑﺮ روﯼ ﺷﺒﮑﻪ ﺗﻌﺮﻳﻒ ﻣﯽ ﻧﻤﺎﻳﺪ،و 23 ﺑﻴﺖ ﻃﻮل دارﻧﺪ. هﺮ ﺳﻴ ﺴﺘﻢ ﺑ ﻪ ﻃ ﻮر‬ ‫ﻣ ﺴﺘﻘﻴﻢ ﺑ ﻪ اﻳﻨﺘﺮﻧ ﺖ ﻣﺘ ﺼﻞ ﻣ ﯽ ﮔ ﺮدد و ﺁدرس ‪ IP‬واﺣ ﺪﯼ دارد.ﺁدرس ه ﺎﯼ ‪ IP‬ﻣﻌﻤ ﻮﻻ در ﻧﻤﺎدﮔ ﺬارﯼ ﭼﻬ ﺎر‬ ‫ﻧﻘﻄ ﻪ اﯼ ﻧﻮﺷ ﺘﻪ ﻣ ﯽ ﺷ ﻮد. ﻧﻤﺎدﮔ ﺬارﯼ ﭼﻬ ﺎر ﻧﻘﻄ ﻪ اﯼ ه ﺮ ﭼﻬ ﺎر دﺳ ﺘﻪ ه ﺸﺖ ﺑﻴﺘ ﯽ از ﺁدرس ه ﺎﯼ ‪ IP‬را ﺑ ﻪ‬ ‫ﺻ ﻮرت ﻋ ﺪدﯼ ﺑ ﻴﻦ ﺻ ﻔﺮ و 552 را ﻟﻴ ﺴﺖ ﻣ ﯽ ﻧﻤﺎﻳﺪ،ﮐ ﻪ ﺣﺎﺻ ﻞ ﺁن ﺁدرس ‪ IP‬ﺑ ﻪ ﺷ ﮑﻞ ‪ W.X.Y.Z‬ﻣ ﺜﻼ‬ ‫3.14.12.01 ﻣﯽ ﺑﺎﺷﺪ. ﻣﺜﺎل ﭘﺎﻳﻴﻦ‬ ‫3.14.12.01‬ ‫=‬ ‫01010000‬ ‫10101000‬ ‫10010100‬ ‫11000000‬

‫ه ﺮ ﺑ ﺴﺘﻪ ‪ IP‬ﺣ ﺎوﯼ ﺁدرس ‪ IP‬ﻣﺒ ﺪا ﻣ ﯽ ﺑﺎﺷ ﻨﺪ، و ﺳﻴ ﺴﺘﻤﯽ را ﺗﻌ ﺮف ﻣ ﯽ ﻧﻤﺎﻳ ﺪ ﮐ ﻪ در ﺣ ﺎل ارﺳ ﺎل ﺑ ﺴﺘﻪ، و‬ ‫ﺁدرس ‪ IP‬ﻣﻘﺼﺪ ﻣﯽ ﺑﺎﺷﺪ ﮐﻪ ﺳﻴﺴﺘﻢ را ﺑﺮاﯼ ﺑﺴﺘﻪ ﺗﻌﺮﻳﻒ ﻣﯽ ﮐﻨﺪ.‬

‫ﻧﺖ ﻣﺴﮑﻬﺎ‬
‫هﺮ ﺁدرس ‪ IP‬در واﻗﻊ ﺣﺎوﯼ دو ﻣﻮﻟﻔﻪ ﻣﯽ ﺑﺎﺷﺪ. ﺁدرس ﺷﺒﮑﻪ و ﺁدرس ﻣﻴﺰﺑ ﺎن در ﺁن ﺷ ﺒﮑﻪ ﺧ ﺎص ، ﺁدرس‬ ‫ﺷﺒﮑﻪ ‪ LAN‬ﺧﺎﺻﯽ را ﺗﻮﺿﻴﺢ ﻣﯽ دهﺪ ﮐﻪ در ﺁ» داد وﺳﺘﺪ دادﻩ هﺎ ﻣﯽ ﺗﻮاﻧﺪ ﺑ ﺮاﯼ ارﺳ ﺎل ﺗﻨﻈ ﻴﻢ ﺷ ﻮد.ﺁدرس‬ ‫ﻣﻴﺰﺑﺎن دﺳﺘﮕﺎﻩ ﺧﺎﺻﯽ را در ‪ LAN‬دادﻩ ﺷﺪﻩ ﻣﻌﺮﻓﯽ ﻣﯽ ﮐﻨﺪ.‬ ‫ﭼﻄﻮر ﮐﺎﻣﭙﻴﻮﺗﺮ ﻳﺎ ﻣﺴﻴﺮ ﻳﺎب ﻣﯽ داﻧﺪ ﮐﻪ ﮐﺪام ﺑﺨﺶ از ﺁدرس ‪ IP‬ﺑﻪ ﺷ ﺒﮑﻪ اﺷ ﺎرﻩ ﻣ ﯽ ﻧﻤﺎﻳ ﺪ و ﮐ ﺪام ﺑﺨ ﺶ ﺑ ﻪ‬ ‫ﻣﻴﺰﺑﺎن اﺷﺎرﻩ ﻣﯽ ﮐﻨﺪ؟ اﻳﻦ اﻃﻼﻋﺎت ﺑﺮﭘﺎﻳﻪ ﭼﻴﺰﯼ ﺗﻌﻴﻴﻦ ﻣﯽ ﮔ ﺮدد ﮐ ﻪ ﻧ ﺖ ﻣ ﺴﮏ ﻧﺎﻣﻴ ﺪﻩ ﻣ ﯽ ﺷ ﻮد. ﻧ ﺖ ﻣ ﺴﮏ‬ ‫ﺗﻌﺮﻳﻒ ﻣ ﯽ ﻧﻤﺎﻳ ﺪ ﮐ ﻪ ﮐ ﺪام ﺑﻴﺘﻬ ﺎ در ﺁدرس ﺷ ﺒﮑﻪ ﻣ ﯽ ﺑﺎﺷ ﻨﺪ )ﮐ ﻪ ﻣ ﺎﺑﻘﯽ ﺑﻴﺘﻬ ﺎ در ﺁدرس ‪ IP‬در ﺑﺨ ﺶ ﻣﻴﺰﺑ ﺎن‬ ‫ﺁأرس وﺟ ﻮد دارﻧ ﺪ(.ﻧ ﺖ ﻣ ﺴﮏ ﺷ ﻤﺎرﻩ دوﺗ ﺎﻳﯽ ﻣ ﯽ ﺑﺎﺷ ﺪ.وﻗﺘ ﯽ ﺑﻴ ﺖ دادﻩ ﺷ ﺪﻩ در ﺁدرس ‪ IP‬ﺑﺨ ﺸﯽ از ﺁدرس‬ ‫ﺷﺒﮑﻪ ﺑﺎﺷﺪ، داراﯼ ﻣﺠﻤﻮﻋﻪ ﺑﻴﺘﻬﺎﯼ ﻣﺴﺎوﯼ ﺑﺎ ﻳﮏ اﺳﺖ.وﻗﺘﯽ ﺑﻴﺖ ﺁدرس ‪ IP‬ﺑﺨﺸﯽ از ﺁدرس ﻣﻴﺰﺑ ﺎن ﺑﺎﺷ ﺪ،‬ ‫ﻧﺖ ﻣﺴﮏ داراﯼ ﺑﻴﺖ ﺻﻔﺮ ﻣﯽ ﺑﺎﺷﺪ.ﺑﻨﺎﺑﺮاﻳﻦ ، ﻣﯽ ﺗﻮاﻧﻴﺪ ﺁﻧﭽﻪ را ﮐﻪ ﺷﺒﮑﻪ ﺑﺎ اﺳﺘﻔﺎدﻩ از ﺗﺎﺑﻊ ‪ XOR‬در ﺣ ﺎل‬ ‫ﺗﺮﮐﻴﺐ ﮐ ﻞ ﺁدرس ‪ IP‬ﺑ ﺎ ﻧ ﺖ ﻣ ﺴﮏ اﺳ ﺖ را ﭘﻴﮑﺮﺑﻨ ﺪﯼ ﻧﻤﺎﻳﻴ ﺪ.ﻧ ﺖ ﻣ ﺴﮑﻬﺎ ﻧﻴ ﺰ ﻣﺜ ﻞ ﺁدرﺳ ﻬﺎﯼ ‪ IP‬ﺑ ﻪ ﺻ ﻮرت‬ ‫ﻧﻤﺎدﮔﺬارﯼ ﭼﻬﺎر ﻧﮑﺘﻪ اﯼ ﻧﻮﺷﺘﻪ ﻣﯽ ﺷﻮﻧﺪ.‬ ‫-9-‬

‫‪Learning TCP/IP‬‬

‫‪BY: Nasser-Desperado‬‬

‫: ‪Address‬‬ ‫: ‪Netmask‬‬

‫3.14.12.01‬

‫=‬

‫01010000‬ ‫11111111‬

‫10101000‬ ‫11111111‬

‫10010100‬ ‫00000000‬

‫11000000‬ ‫00000000‬ ‫‪XOR‬‬

‫= 0.0.552.552‬

‫_______________________________________________________‬ ‫00000000 00000000 10101000 01010000‬

‫ﺗﻘﺴﻴﻢ ﺑﻨﺪﯼ ﺑﺴﺘﻪ ﻧﺮم اﻓﺰارﯼ در ‪ IP‬ﺑﻪ ﺻﻮرت ﻗﻄﻌﺎت ﻣﺴﺎوﯼ‬
‫ﻣﺤﻴﻂ هﺎﯼ ﻣﺘﻔﺎوت اﻧﺘﻘﺎل دارﯼ ﺧﺼﻮﺻﻴﺎت ﻋﻤﻠﮑﺮد ﻣﺨﺘﻠ ﻒ ﻣ ﯽ ﺑﺎﺷ ﻨﺪ. ﺑﻌ ﻀﯽ از ﻣﺤ ﻴﻂ ه ﺎ، وﻗﺘ ﯽ ﺑ ﺴﺘﻪ ه ﺎ‬ ‫ﺑﺰرﮔﺘﺮﻧﺪ،ﮐﺎر ﺑﺴﻴﺎر ﺑﻬﺘﺮﯼ را اﻧﺠﺎم ﻣﯽ دهﻨﺪ. در ﺣﺎﻟﯽ ﮐﻪ ﻣ ﺎ ﺑﻘ ﯽ از داﺷ ﺘﻦ ﺑ ﺴﺘﻪ ه ﺎﯼ ﻧﺮﻣ ﺎﻓﺰارﯼ ﮐ ﻪ ﻃ ﻮل‬ ‫ﮐﻮﺗﺎهﺘﺮﯼ دارﻧﺪ،ﺳﻮد ﻣﯽ ﺑﺮﻧﺪ. ﺑﺮاﯼ ﻣﺜﺎل،دﺳﺘﻪ ﺑﻨﺪﯼ ﺑﺴﺘﻪ ‪ IP‬اﻧﺘﻘﺎل ﻳﺎﻓﺘﻪ از ﻃﺮﻳﻖ ﻣﺎهﻮارﻩ ﺑﺴﺒﺎر ﻣ ﺸﮑﻠﺘﺮ‬ ‫از ارﺳﺎل ﺑﺴﺘﻪ اﯼ اﺳﺖ ﮐﻪ از ﺟﻠﻮﯼ ﺷﻴ ﺸﻪ دﻓﺘﺮﺗ ﺎن ﻣ ﯽ ﮔ ﺬرد.در ﺣ ﻴﻦ ارﺳ ﺎل اﻃﻼﻋ ﺎت از ﻃﺮﻳ ﻖ ﻣ ﺎهﻮارﻩ ،‬ ‫ﺑﺴﺘﻪ هﺎﯼ ﺑﺰرﮔﺘﺮ ﮐﺎرﺁﻳﯽ ﺑﻴﺸﺘﺮﯼ دارﻧﺪ،ﺑﺮاﯼ ﺑﻬﻴﻨﻪ ﺳﺎزﯼ ﻃﻮل اﻃﻼﻋ ﺎت ﺑ ﺮاﯼ اﺗ ﺼﺎل ارﺗﺒ ﺎﻃﯽ ﻣﺨﺘﻠ ﻒ ،‪IP‬‬ ‫ﺑﺮاﯼ اﺟﺰاﯼ ﺷﺒﮑﻪ )ﻣﺜﻞ دﻳﻮارﻩ هﺎﯼ ﺁﺗﺶ ﻳ ﺎ ﻣ ﺴﻴﺮ ﻳﺎﺑﻬ ﺎ( ﺗﻮاﻧ ﺎﻳﯽ ﻻزم را ﻓ ﺮاهﻢ ﻣ ﯽ ﺁورد ﺗ ﺎ ﺑ ﺴﺘﻪ ه ﺎ را ﺑ ﻪ‬ ‫ﻗﻄﻌﺎت ﮐﻮﭼﮑﺘﺮ ﺗﻘﺴﻴﻢ ﻧﻤﺎﻳﺪ، ﻋﻤﻠﯽ ﮐﻪ ﺗﻘﺴﻴﻢ ﻧﻤﺎﻳﺪ،ﻋﻤﻠﯽ ﮐﻪ ﺗﻘﺴﻴﻢ ﺑﻨﺪﯼ ﺑﺎ ﻗﻄﻌﺎت ﻣﺴﺎوﯼ ،ﻧﺎﻣﻴ ﺪﻩ ﻣ ﯽ ﺷ ﻮد.‬ ‫ﺳﻴﺴﺘﻢ ﻣﻘﺼﺪ ﻳﺎ ﺷﺒﮑﻪ ﻣﯽ ﺗﻮاﻧﺪ ﺑﺴﺘﻪ هﺎﯼ ‪ IP‬ﺑﺰرگ را ﺑﭙﺬﻳﺮد و ﺁﻧﻬﺎ را ﺑﻪ ﻗﻄﻌﺎت ﮐﻮﭼﮑﺘﺮ و ﺑﺮاﯼ اﻧﺘﻘﺎل از‬ ‫ﻃﺮﻳﻖ ﺷﺒﮑﻪ ﺗﻘ ﺴﻴﻢ ﻧﻤﺎﻳ ﺪ.ﻻﻳ ﻪ ‪ IP‬ﺳﻴ ﺴﺘﻢ ﻣﻘ ﺼﺪ ﻣ ﺴﺌﻮل ﺳ ﺮ ه ﻢ ﺑﻨ ﺪﯼ دوﺑ ﺎرﻩ ﻗﻄﻌ ﺎت اﺳ ﺖ و ﻗﺒ ﻞ از اﻳﻨﮑ ﻪ‬ ‫اﻃﻼﻋﺎت اﻃﻼﻋﺎت ﺑﻪ ﻻﻳﻪ اﻧﺘﻘﺎل ﻋﺒﻮر ﻧﻤﺎﻳﻨﺪ.‬ ‫ﻋﻨﻮان ‪ IP‬دو زﻣﻴﻨﻪ را ﻓﺮاهﻢ ﻣﯽ ﺁورد ﺗﺎ از اﻳﻦ ﻋﻤﻞ ﺗﻘﺴﻴﻢ ﺑﻨﺪﯼ ﭘﺸﺘﻴﺒﺎﻧﯽ ﮐﻨﺪ در اﺑﺘ ﺪا زﻣﻴﻨ ﻪ ‪Fragment‬‬ ‫‪ Offset‬ﺑﻪ دوﺳﻴﺴﺘﻢ ﻣﯽ ﮔﻮﻳﺪ ﮐﻪ در ﮐﺠﺎ ﻣﻨﺪﺟﺎت اﻳﻦ ﻗﻄ ﻪ ﺑﺎﻳ ﺪ وﺟ ﻮد داﺷ ﺘﻪ ﺑﺎﺷ ﺪ،وﻗﺘﯽ ﮐ ﻪ ﮐ ﻞ ﺑ ﺴﺘﻪ از ﻧ ﻮ‬ ‫ﺳﺮ هﻢ ﺑﻨﺪﯼ ﻣﯽ ﺷﻮد.زﻣﻴﻨﻪ ‪ Identification‬ﺑﺎ ﺳﻴﺴﺘﻢ ﺗﻘﺴﻴﻢ ﺑﻨﺪﯼ ﺑﻪ ﻣﻘ ﺪار واﺣ ﺪﯼ ﺗﻨﻈ ﻴﻢ ﻣ ﯽ ﺷ ﻮد ﺗ ﺎ ﺑ ﻪ‬ ‫ﺳﻴﺴﺘﻢ ﻣﻘﺼﺪ ﮐﻤ ﮏ ﻧﻤﺎﻳ ﺪ، ﺑ ﺴﺘﻪ را ﻧ ﻮ ﺳ ﺮ ه ﻢ ﺑﻨ ﺪﯼ ﻧﻤﺎﻳ ﺪ. ﺑﻌ ﻼوﻩ، ﻧ ﺸﺎﻧﻪ ه ﺎﯼ ﻋﻨ ﻮان ‪ IP‬اﻃﻼﻋ ﺎﺗﯽ را در‬ ‫ﻣﻮرد ﺗﻘﺴﻴﻢ ﺑﻨﺪﯼ اﻃﻼﻋﺎت ﻣﺸﺨﺺ ﻣﯽ ﮐﻨﺪ. ﺳﻴ ﺴﺘﻢ ارﺳ ﺎل ﮐﻨﻨ ﺪﻩ ﻣ ﯽ ﺗﻮاﻧ ﺪ اﻳ ﻦ زﻣﻴﻨ ﻪ ه ﺎ را ﻧﺘﻈ ﻴﻢ ﻧﻤﺎﻳ ﺪ ﺗ ﺎ‬ ‫ﻧﺸﺎن دهﺪ ﮐﻪ ﺑﺴﺘﻪ ﻧﺒﺎﻳ ﺪ در هﻨﮕ ﺎم ارﺳ ﺎل از ﻃﺮﻳ ﻖ ﺷ ﺒﮑﻪ ﺗﻘ ﺴﻴﻢ ﺷ ﻮد.اﻟﺒﺘ ﻪ اﮔ ﺮ ﺑ ﺴﺘﻪ اﯼ ﺗﻘ ﺴﻴﻢ ﺷ ﻮد، اﻳ ﻦ‬ ‫ﻧﺸﺎﻧﻪ هﺎ ﻣﺸﺨﺺ ﻣﯽ ﮐﻨﻨﺪﮐﻪ ﺁﻳﺎ ﻗﻄﻌﺎت دﻳﮕﺮﯼ از ﺑﺴﺘﻪ اﺻﻠﯽ هﻨﻮز راﻩ وﺟﻮد دارﻧﺪ ﻳﺎ ﺧﻴﺮ. اﻳ ﻦ دو ﺑﻴ ﺖ ﻣ ﯽ‬ ‫ﺗﻮاﻧﻨﺪ داراﯼ ﻣﻘﺎدﻳﺮ زﻳﺮ ﺑﺎﺷﻨﺪ.‬ ‫1 ‪) Flag Bit‬ﺑﻴﺖ ‪ = 0 : (Don’t Fragment‬اﻣﮑﺎن دارد ﻗﻄﻌﻪ اﯼ وﺟﻮد داﺷﺘﻪ ﺑﺎﺷﺪ. 1 = هﻴﭻ ﻗﻄﻌﻪ اﯼ‬ ‫وﺟﻮد ﻧﺪاردد.‬ ‫1 ‪) Flag Bit‬ﺑﻴﺖ ‪ = 0 : (More Fragment‬ﻗﻄﻌﻪ ﻗﺒ ﻞ هﻨ ﻮز ﺑ ﺎﻗﯽ ﻣﺎﻧ ﺪﻩ اﺳ ﺖ. 1 = ﻗﻄﻌ ﺎت ﺑﻴ ﺸﺘﺮﯼ ﺟ ﺎ‬ ‫ﻣﺎﻧﺪﻩ اﺳﺖ.‬

‫اﺟﺰاﯼ دﻳﮕﺮ ﻋﻨﻮان ‪IP‬‬
‫ﺣﺎل ﮐﻪ ﻣﻌﻨ ﺎﯼ ﺁدرس ‪ IP‬و زﻣﻴﻨ ﻪ ه ﺎﯼ ﺗﻘ ﺴﻴﻢ ﺑﻨ ﺪﯼ را در ﻋﻨ ﻮان ‪ IP‬داﻧ ﺴﺘﻴﻢ. ﻧﮕ ﺎهﯽ ﻣ ﯽ اﻧ ﺪازﻳﻢ ﺑ ﻪ دﻳﮕ ﺮ‬ ‫زﻣﻴﻨﻪ هﺎﻳﯽ ﮐﻪ ﺑﺴﺘﻪ ‪ IP‬از ﺁﻧﻬﺎ ﺳﺎﺧﺘﻪ ﻣﯽ ﺷﻮﻧﺪ. زﻣﻴﻨﻪ هﺎﯼ ﻋﻨﻮان ‪ IP‬ﻋﺒﺎرﺗﻨﺪ از :‬ ‫‪ : Version‬اﻳﻦ ﭼﻬﺎر ﺑﻴﺖ وﺑ ﺮاﻳﺶ ﭘﺮوﺗﮑ ﻞ اﻳﻨﺘﺮﻧﺘ ﯽ ﻣ ﻮرد اﺳ ﺘﻔﺎدﻩ را ﺗﻮﺿ ﻴﺢ ﻣ ﯽ دهﻨ ﺪ. 4 ‪IP Version‬‬ ‫ﻳﮑﯽ از ﻣﺘﺪاوﻟﺘﺮﻳﻦ وﻳﺮاش هﺎﯼ ﻣﻮرد اﺳﺘﻔﺎدﻩ در اﻳﻨﺘﺮﻧﺖ اﺳﺖ.‬ ‫‪ : IHL‬اﻳﻦ زﻣﻴﻨﻪ ‪ ، Internet Header Length‬ﻃﻮل ﻧﻬﺎﻳﯽ ﻋﻨﻮان ‪ IP‬اﺳﺖ.‬ ‫‪ : Service Type‬اﻳﻦ زﻣﻴﻨﻪ ﺑﺎ ﮐﻴﻔﻴﺖ ﺳﺮوﻳﺲ هﻤﺮاﻩ ﻣﯽ ﺑﺎﺷﺪ، و ﺑ ﻪ اﺟ ﺰاﯼ ﺷ ﺒﮑﻪ ﻣﻘ ﺪار ﺣ ﺴﺎﺳﻴﺖ داد و‬ ‫ﺳﺘﺪ دادﻩ هﺎﻳﯽ را ﻧﺸﺎن ﻣﯽ دهﺪ ﮐﻪ ﻣﻤﮑﻦ اﺳﺖ در ﺗﺎﺧﻴﺮهﺎ وﺟﻮد داﺷﺘﻪ ﺑﺎﺷﺪ.‬ ‫‪ : Total Length‬اﻳﻦ زﻣﻴﻨﻪ ﻃﻮل ﻧﻬﺎﻳﯽ ﺑ ﺴﺘﻪ ‪ ، IP‬را ﺗﻌﺮﻳ ﻒ ﻣ ﯽ ﮐﻨ ﺪ ﮐ ﻪ ﺷ ﺎﻣﻞ ﻋﻨ ﻮان ‪ IP‬و دادﻩ ه ﺎﻳﺶ‬ ‫ﻣﯽ ﺑﺎﺷﺪ.‬ ‫‪ : Identification‬اﻳﻦ زﻣﻴﻨﻪ ﺑﺮاﯼ ﭘﺸﺘﻴﺒﺎﻧﯽ از ﺳﺮ هﻢ ﺑﻨﺪﯼ دوﺑﺎرﻩ ﻗﻄﻌﺎت اﺳﺘﻔﺎدﻩ ﻣﯽ ﮔﺮدد.‬ ‫‪ : Fragment Offset‬اﻳﻦ ﻋﺪد ﻧﺸﺎﻧﮕﺮ ﺟﺎﻳﯽ اﺳﺖ ﮐﻪ اﻳﻦ ﻗﻄﻌﻪ در ﮐﻞ ﺑﺴﺘﻪ ﻣﯽ ﻧﺸﻴﻨﺪ.‬ ‫‪: (TTL) Time-to-Live‬اﻳﻦ زﻣﻴﻨﻪ ﺑ ﺮاﯼ ﻧ ﺸﺎن دادن ﺣ ﺪاﮐﺜﺮ ﺗﻌ ﺪاد ﺟﻬ ﺶ ه ﺎﯼ ﻣ ﺴﻴﺮ ﻳ ﺎب ﺑ ﻪ ﻣ ﺴﻴﺮ ﻳ ﺎب‬ ‫ﺑﺴﺘﻪ اﯼ اﺳﺘﻔﺎدﻩ ﻣﯽ ﺷﻮد ﮐﻪ در هﻨﮕﺎم ﻋﺒﻮر ﺑﺴﺘﻪ از ﺷﺒﮑﻪ ﺑﺎﻳﺪ در ﻧﻈﺮ ﮔﺮﻓﺘﻪ ﺷﻮد.‬ ‫‪ : Protocol‬اﻳﻦ زﻣﻴﻨﻪ ﭘﺮوﺗﮑﻠﯽ را ﺗﻮﺿﻴﺢ ﻣﯽ دهﺪ ﮐﻪ ﺑﺎ اﻳﻦ ﺑﺴﺘﻪ ‪ IP‬ﺣﻤﻞ ﻣﯽ ﮔﺮدد و ﻏﺎﻟﺒﺎ ﺑﺮاﺑ ﺮ ﻣﻘ ﺪارﯼ‬ ‫ﻣﯽ ﺑﺎﺷﺪ ﮐﻪ در ارﺗﺒﺎط ﺑﺎ ‪ TCP‬ﻳﺎ ‪ UDP‬ﻣﯽ ﺑﺎﺷﺪ.‬ ‫‪ : Header Checksum‬اﻳ ﻦ اﻃﻼﻋ ﺎت ﺑ ﺮاﯼ ﺣ ﺼﻮل اﻃﻤﻴﻨ ﺎن از اﻳ ﻦ ﻣ ﻮرد ﺻ ﻮرت ﻣ ﯽ ﮔﻴ ﺮد ﮐ ﻪ ﻋﻨ ﻮان‬ ‫ﺗﺨﺮﻳﺐ ﻧﺸﺪﻩ اﺳﺖ و در ﺟﻬﺶ ﻣﺴﻴﺮ ﻳﺎب از ﻧﻮ ﻣﺤﺎﺳﺒﻪ ﻣﯽ ﺷﻮد.‬ ‫- 01 -‬

‫‪Learning TCP/IP‬‬

‫‪BY: Nasser-Desperado‬‬

‫‪ : Source IP Address‬اﻳﻦ زﻣﻴﻨﻪ ﺷﺒﮑﻪ و ﻣﻴﺰﺑﺎﻧﯽ را ﻧﺸﺎن ﻣﯽ دهﺪ ﮐﻪ ﺑﺴﺘﻪ ار ﺁن ﺑﻴﺮون ﻣﯽ ﺁﻳﺪ.‬ ‫‪ : Destination IP Address‬اﻳﻦ زﻣﻴﻨﻪ ﺷﺒﮑﻪ و ﻣﻴﺰﺑﺎﻧﯽ را ﻧﺸﺎن ﻣﯽ دهﺪ ﮐﻪ ﺑﺴﺘﻪ ﺑﻪ ﺁﻧﺠﺎ ﻣﯽ رود.‬ ‫‪ : Options‬اﻳﻦ زﻣﻴﻨﻪ ﻃﻮل هﺎﯼ ﻣﺘﻐﻴﻴﺮ اﻃﻼﻋﺎت ﮔﺴﺘﺮدﻩ ﻻﻳﻪ ‪ IP‬را ﻧﺸﺎن ﻣﯽ دهﻨﺪ. از اﻳﻦ زﻣﻴﻨ ﻪ ﺧ ﺼﻮﺻﺎ‬ ‫در ﻣﺴﻴﺮ ﻳﺎﺑﯽ ﻣﻨﺒﻊ اﺳﺘﻔﺎدﻩ ﻣﯽ ﺷﻮد، ﻋﻤﻠﯽ ﮐﻪ در زﻳﺮ ﺑﺎ ﺟﺰﺋﻴﺎت ﺑﻴﺸﺘﺮ ﺷﺮح دادﻩ ﻣﯽ ﺷﻮد.‬ ‫‪ : Padding‬اﻳﻦ زﻣﻴﻨﻪ ﺑﺮاﯼ ﮔﺮد ﻧﻤﻮدن ﻃﻮل ﻋﻨﻮان ‪ IP‬اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﺷ ﻮد ﺑ ﻪ ﻃ ﻮرﯼ ﮐ ﻪ در ﻣ ﺮز ﺧﻄ ﯽ 23‬ ‫ﺑﻴﺘﯽ ﻗﺮار ﺑﮕﻴﺮد.‬

‫اﻳﻤﻨﯽ در ‪ IP‬ﻗﺪﻳﻤﯽ‬
‫ﺑﻬﺘﺮ اﺳﺖ اﺷﺎرﻩ ﮐﻨﻢ ﮐﻪ ﭘﺮوﺗﮑﻞ ﻗﺪﻳﻤﯽ ﻣﻮرد اﺳﺘﻔﺎدﻩ در اﻳﻨﺘﺮﻧﺖ ، 4 ‪ IP Version‬داراﯼ ﻗﺎﺑﻠﻴﺘﻬﺎﯼ اﺳﺎﺳ ﯽ‬ ‫اﻣ ﺮوزﯼ ﻧﻤ ﯽ ﺑﺎﺷ ﺪ.ﺗﻤ ﺎم اﺟ ﺰاﯼ ﺑ ﺴﺘﻪ در ﻣ ﺘﻦ واﺿ ﺤﯽ ﻗ ﺮار دارﻧ ﺪ، ه ﻴﭻ ﭼﻴ ﺰ رﻣ ﺰﯼ ﻧﻴ ﺴﺖ. ه ﺮ ﭼﻴ ﺰﯼ در‬ ‫ﻋﻨﻮان، ﺣﺘﯽ در ﻗﻄﻌﻪ دادﻩ هﺎ ﺑ ﻪ وﺳ ﻴﻠﻪ هﮑ ﺮ دﻳ ﺪﻩ ﻳ ﺎ اﺻ ﻼح ﺷ ﻮد. ﺑﻌ ﻼوﻩ ﭘﺮوﺗﮑ ﻞ داراﯼ ه ﻴﭻ ﺗﺎﻳﻴﺪﻳ ﻪ ﻧﻤ ﯽ‬ ‫ﺑﺎﺷﺪ. ﺑﻨﺎﺑﺮاﻳﻦ ، هﮑﺮ ﻣﯽ ﺗﻮاﻧﺪ ﺑﺴﺘﻪ هﺎﻳﯽ را ﺑﺎ ﺁدرس ‪ IP‬ﻣﺒﺪا اﻳﺠﺎد ﮐﻨﺪ.‬

‫‪ICMP‬‬
‫ﻋﻨ ﺼﺮ اﺻ ﻠﯽ و ﺑ ﺴﻴﺎر ﻣﻬ ﻢ دﻳﮕ ﺮ ﺧ ﺎﻧﻮادﻩ ‪ TCP/IP‬ﭘﺮوﺗﮑ ﻞ ﭘﻴﻐ ﺎم ﮐﻨﺘ ﺮل اﻳﻨﺘﺮﻧ ﺖ )‪ (ICMP‬ﻣ ﯽ ﺑﺎﺷ ﺪ.‬ ‫‪ ICMP‬ﻣﺜﻞ ﻟﻮﻟﻪ ﮐ ﺶ ﺷ ﺒﮑﻪ ﺁﺑﺮﺳ ﺎﻧﯽ ﻣ ﯽ ﺑﺎﺷ ﺪ. ﮐ ﺎرش اﻧﺘﻘ ﺎل دﺳ ﺘﻮر و ﮐﻨﺘ ﺮل اﻃﻼﻋ ﺎت ﺑ ﻴﻦ ﺳﻴ ﺴﺘﻢ ه ﺎ و‬ ‫اﺟﺰاﯼ ﺷﺒﮑﻪ اﺳﺖ ﺗﺎ اﻧﺘﻘ ﺎل دادﻩ ه ﺎﯼ واﻗﻌ ﯽ را رواج ده ﺪ وﺧﻄﺎه ﺎ را ﮔ ﺰارش ﮐﻨ ﺪ.ﻳ ﮏ ﺳﻴ ﺴﺘﻢ ﻣ ﯽ ﺗﻮاﻧ ﺪ از‬ ‫‪ ICMP‬اﺳﺘﻔﺎدﻩ ﻧﻤﺎﻳﺪ ﺗﺎ ﺗﻌﻴﻴﻦ ﮐﻨﺪ ﮐﻪ ﺁﻳﺎ ﺳﻴﺴﺘﻢ دﻳﮕﺮ ﺑﺎ ارﺳﺎل ﭘﻴﻨ ﮓ هﻮﺷ ﻴﺎر اﺳ ﺖ ﻳ ﺎ ﺧﻴ ﺮ ﮐ ﻪ ﭘﻴﻨ ﮓ ﭘﻴﻐ ﺎم‬ ‫‪ ICMP Echo Reply‬را ارﺳﺎل ﺧﻮاهﺪ ﺧﻮاهﺪ ﮐ ﺮد. ﻣ ﺴﻴﺮ ﻳ ﺎب ﻣ ﯽ ﺗﻮاﻧ ﺪ از ‪ ICMP‬اﺳ ﺘﻔﺎدﻩ ﻧﻤﺎﻳ ﺪ ﺗ ﺎ ﺑ ﻪ‬ ‫ﺳﻴ ﺴﺘﻢ ﻣﺒ ﺪا اﻃ ﻼع ده ﺪ ﮐ ﻪ ﻣ ﺴﻴﺮﯼ ﺑ ﺮاﯼ ﻣﻘ ﺼﺪ ﻣ ﻮرد ﻧﻴ ﺎز ﻧ ﺪارد )ﭘﻴﻐ ﺎﻣﻢ ه ﺎﯼ ‪ICMP Destinat‬‬ ‫‪ . (Unreachable‬ﻣﻴﺰﺑﺎن ﻣﯽ ﺗﻮاﻧﺪ ﺑﻪ ﺳﻴﺴﺘﻢ دﻳﮕ ﺮ اﻃ ﻼع ده ﺪ ﮐ ﻪ ﺗﻌ ﺪاد ﺑ ﺴﺘﻪ ه ﺎﻳﯽ ﮐ ﻪ در ﺣ ﺎل ارﺳ ﺎل را‬ ‫ﮐﺎهﺶ دهﺪ وا ﻳﻦ ﻋﻤﻞ را ﺑﺎ ﻓﺮﺳﺘﺎدن ﭘﻴﻐﺎم ‪ ICMP Source Quench‬اﻧﺠ ﺎم ﻣ ﯽ ده ﺪ. ﺑﻨ ﺎﺑﺮاﻳﻦ، ‪ICMP‬‬ ‫در ﺳﻴ ﺴﺘﻢ ه ﺎ ﺑ ﺮاﯼ ﺗﺒ ﺎدل اﻃﻼﻋ ﺎت در ﻣ ﻮرد روش ﺟﺮﻳ ﺎن ﺳ ﺎزﯼ داده ﺎ )ﻳ ﺎ ﻗﻄ ﻊ ﺟﺮﻳ ﺎن دادﻩ ه ﺎ( از ﻃﺮﻳ ﻖ‬ ‫اﻳﻨﺘﺮﻧﺖ اﺳﺘﻔﺎدﻩ ﻣﯽ ﺷﻮد.‬ ‫‪ ICMP‬از هﻤﺎن ﻓﺮﻣﺖ ﻋﻨﻮان، ﺑﻪ ﺷﮑﻞ ‪ IP‬ﺑﺮاﯼ ﺁدرﺳﻬﺎﯼ ‪ IP‬ﻣﻘ ﺼﺪ و ﻣﺒ ﺪا، ﺗﻘ ﺴﻢ ﺑﻨ ﺪﯼ ﺑ ﺴﺘﻪ ﺑ ﻪ ﻗﻄﻌ ﺎت‬ ‫ﻣﺴﺎوﯼ، و دﻳﮕﺮ ﻋﻤﻠﮑﺮدهﺎ اﺳﺘﻔﺪﻩ ﻣﯽ ﮐﻨﺪ. زﻣﻴﻨﻪ ﭘﺮوﺗﮑ ﻞ ﻋﻨ ﻮان ‪ IP‬ﺑ ﺎ ﻣﻘ ﺪارﯼ ﻣﺘﻨﺎﺳ ﺐ ﺑ ﺎ ‪ ICMP‬ﻧ ﺼﺐ‬ ‫ﻣﯽ ﮔﺮدد. ﭘﺲ از ﻋﻨ ﻮان ‪ ، IP‬در ﺗﺮﮐﻴ ﺐ دادﻩ ه ﺎﯼ ﺑ ﺴﺘﻪ ‪ ICMP،IP‬زﻣﻴﻨ ﻪ اﯼ را اﺿ ﺎﻓﻪ ﻣ ﯽ ﻧﻤﺎﻳ ﺪ ﮐ ﻪ ﺑ ﻪ‬ ‫ﺷﮑﻞ ﻧﻮع ‪ ICMP‬ﺷﻨﺎﺧﺘﻪ ﻣﯽ ﺷﻮد. ﻓﺮﻣﺖ ﺑﺎﻗﻴﻤﺎﻧﺪﻩ ﺑﺴﺘﻪ ‪ ICMP‬ﺑﺴﺘﮕﯽ ﺑﻪ اﻳ ﻦ ﻧ ﻮع ‪ ICMP‬دارد. ﭘﻴﻐ ﺎم‬ ‫هﺎﯼ ‪ ICMP‬ﻋﻨﺎوﻳﻦ زﻳﺎدﯼ دادﻧﺪ.‬

‫هﺪف ار اﻳﻦ ﻧﻮع ﭘﻴﻐﺎم‬
‫اﻳﻦ ﭘﻴﻐﺎم ﺑﺮاﯼ ﭘﺎﺳﺦ ﺑﻪ ﭘﻴﻨﮓ اﺳﺘﻔﺎدﻩ ﻣﯽ ﺷﻮد‬ ‫وﻗﺘﯽ ﺳﻴﺴﺘﻢ هﻮﺷﻴﺎر ﻣﯽ ﺑﺎﺷﺪ‬ ‫اﻳ ﻦ ﭘﻴﻐ ﺎم ﻧ ﺸﺎن ﻣ ﯽ ده ﺪ ﮐ ﻪ ﭘﻴﻐ ﺎم اول ‪ IP‬ﻧﻤ ﯽ‬ ‫ﺗﻮاﻧ ﺴﺘﻪ ﺑ ﻪ ﻣﻘ ﺼﺪش ارﺳ ﺎل ﺷ ﺪﻩ ﺑﺎﺷ ﺪ و اﻳ ﻦ‬ ‫اﺣﺘﻤﺎل وﺟﻮد دارد ﮐﻪ ﻣﺴﻴﺮ ﻳﺎﺑﯽ در ﻃﻮل راﻩ.‬ ‫ﻣ ﺴﻴﺮ ﺗﻌﺮﻳ ﻒ ﺷ ﺪﻩ اﯼ ﺑ ﻪ ﻣﻘ ﺼﺪ ﻧﺪاﺷ ﺘﻪ ﺑﺎﺷ ﺪ.‬ ‫اﻟﺒﺘﻪ، اﮔﺮ دﺳﺘﮕﺎﻩ ﻣﻘﺼﺪ ﻧﺘﻮاﻧﺪ ﺑﺎ ﭘﺮوﺗﮑﻞ ﻣﻨﺎﺳﺐ‬ ‫ﺻ ﺤﺖ ﻧﻤﺎﻳ ﺪ، اﻳ ﻦ ﻧ ﻮع ﭘﻴﻐ ﺎم ﺑ ﺎز ﺧﻮاه ﺪ ﮔ ﺸﺖ.‬ ‫ﺑﺪﻳﻦ ﺷﮑﻞ ﻣﻴﺰﺑ ﺎن ﻣﻘ ﺼﺪ ﻣ ﯽ ﺗﻮاﻧ ﺴﺖ اﻳ ﻦ ﭘﻴﻐ ﺎم‬ ‫را ﺑﺮﮔﺮداﻧ ﺪ اﮔ ﺮ دروازﻩ ‪ TCP‬ﻳ ﺎ ‪ UDP‬ﻣﻘ ﺼﺪ‬ ‫ﺑﺴﺘﻪ ﺑﺎﺷﺪ.‬ ‫ﺳﻴﺴﺘﻢ در ﺣﺎل درﻳﺎﻓﺖ ﺑﺴﻴﺎر ﺳﺮﻳﻊ ﺑ ﺴﺘﻪ ه ﺎ ﻣ ﯽ‬ ‫ﺑﺎﺷﺪ ﺗﺎ ﺁﻧ ﻪ را در ﺻ ﻒ ورودﻳ ﺶ ﭘ ﺮدازش ﮐﻨ ﺪ و‬ ‫ﻣﻤﮑ ﻦ اﺳ ﺖ ﭘﻴﻐ ﺎم اﺳ ﺖ ﭘﻴﻐ ﺎم ‪Source‬‬ ‫‪ Quench‬را ارﺳ ﺎل ﻧﻤﺎﻳ ﺪ ﮐ ﻪ ﺑ ﻪ ارﺳ ﺎل اﻃ ﻼع‬ ‫ﻣﯽ دهﺪ ﺳﺮﻋﺖ اﻧﺘﻘﺎل را ﮐﺎهﺶ دهﺪ.‬

‫ﻣﻘﺪار در زﻣﻴﻨﻪ ﻧﻮع‬ ‫‪ICMP‬‬
‫0‬ ‫3‬

‫ﻧﻮع ﭘﻴﻐﺎم‬
‫‪Echo Reply‬‬ ‫‪Destination‬‬ ‫‪Unreachable‬‬

‫4‬

‫‪Source‬‬ ‫‪Quench‬‬

‫- 11 -‬

‫‪Learning TCP/IP‬‬ ‫اﻳﻦ ﭘﻴﻐﺎم ﺑﻮﺳﻴﻠﻪ ﻣﺴﻴﺮ ﻳﺎب ﻓﺮﺳ ﺘﺎدﻩ ﻣ ﯽ ﺷ ﻮد ﺗ ﺎ‬ ‫ﻧ ﺸﺎن ده ﺪ ﮐ ﻪ ﺗﺮاﻓﻴ ﮏ ﺑﺎﻳ ﺪ در ﻣ ﺴﻴﺮ ﻳ ﺎب دﻳﮕ ﺮ‬ ‫ﺑﺎﺷﺪ ﮐﻪ ﻣﯽ ﺗﻮاﻧ ﺪ ﺗﺮاﻓﻴ ﮏ را ﺑ ﻪ ﻣﻘ ﺼﺪﯼ ارﺳ ﺎل‬ ‫ﻧﻤﺎﻳﺪ ﺗﺎ راﻧﺪﻣﺎن ﺑﺎﻻﺗﺮﯼ دارد.‬ ‫اﻳ ﻦ ﻧ ﻮع ﭘﻴﻐ ﺎم ﺑ ﺮاﯼ ارﺳ ﺎل ﭘﻴﻨ ﮓ اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ‬ ‫ﺷﻮد ﺗﺎ اﺟﺮاﯼ ﺳﻴﺴﺘﻢ را ﺗﻌﻴﻴﻦ ﻧﻤﺎﻳﺪ.‬ ‫اﻳﻦ ﭘﻴﻐﺎم ﻧﺸﺎن ﻣﯽ دهﺪ ﮐﻪ ﺣﺪاﮐﺜﺮ ﺗﻌﺪاد ﭘ ﺮش ه ﺎ‬ ‫در زﻣﻴﻨ ﻪ ‪ Time-to-Live‬ﻋﻨ ﻮان ‪ IP‬از ﺣ ﺪ‬ ‫ﺗﺠﺎوز ﮐﺮدﻩ اﺳﺖ.‬ ‫اﻳﻦ ﻧﻮع ﭘﻴﻐﺎم ﺑﺎ ﺳﻴﺴﺘﻤﯽ در ﭘﺎﺳﺦ ﺑ ﻪ ﺑ ﺴﺘﻪ ‪،IP‬‬ ‫ﺑ ﺎ ﭘ ﺎراﻣﺘﺮ ﺑ ﺪﯼ در ﻳﮑ ﯽ از زﻣﻴﻨ ﻪ ه ﺎﯼ ﻋﻨ ﻮاﻧﺶ‬ ‫ارﺳﺎل ﻣﯽ ﺷﻮد.‬ ‫اﻳ ﻦ ﻧ ﻮع ﭘﻴﻐ ﺎم ﺷ ﺎﻣﻞ زﻣ ﺎن در دﺳ ﺘﮕﺎﻩ ارﺳ ﺎل‬ ‫ﮐﻨﻨ ﺪﻩ ﻣ ﯽ ﺑﺎﺷ ﺪ؛ و زﻣ ﺎن دﺳ ﺘﮕﺎﻩ ﻣﻘ ﺼﺪ را‬ ‫درﺧﻮاﺳﺖ ﻣﯽ ﮐﻨﺪ.‬ ‫در درﻳﺎﻓ ﺖ ﭘﻴﻐ ﺎم ‪، ICMP Timestamp‬‬ ‫ﺳﻴﺴﺘﻢ در زﻣﺎن ﺧﻮدش ﺑﺎ ﺟ ﻮاب ‪Timestamp‬‬ ‫ﭘﺎﺳﺦ ﺧﻮاهﺪ داد‬ ‫اﻳ ﻦ ﭘﻴﻐ ﺎم ﻣ ﯽ ﺗﻮاﻧ ﺪ ﺑ ﻪ وﺳ ﻴﻠﻪ ﻣﻴﺰﺑ ﺎﻧﯽ اﺳ ﺘﻔﺎدﻩ‬ ‫ﮔ ﺮدد ﺗ ﺎ ﺗﻌﻴ ﻴﻦ ﻧﻤﺎﻳ ﺪ ﮐ ﻪ ﺷ ﺒﮑﻪ در ﺣ ﺎل ﮐ ﺎر ﻣ ﯽ‬ ‫ﺑﺎﺷﺪ.‬ ‫اﻳﻦ ﭘﻴﻐﺎم ﺣﺎوﯼ ﭘﺎﺳﺨﯽ ﺑﻪ ﭘﻴﻐ ﺎم ‪Information‬‬ ‫‪ Request‬در ﻣﻮرد ﺁدرس ‪ IP‬ﺷﺒﮑﻪ ﺑﺎﺷﺪ.‬ ‫5‬

‫‪BY: Nasser-Desperado‬‬ ‫‪Redirect‬‬

‫8‬ ‫11‬

‫‪Echo‬‬ ‫‪Time‬‬ ‫‪Exeeedad‬‬ ‫‪Para meter‬‬ ‫‪Problem‬‬ ‫‪Time Stamp‬‬

‫21‬

‫31‬

‫41‬

‫‪Times‬‬ ‫‪Tamp Reply‬‬ ‫‪Information‬‬ ‫‪Request‬‬ ‫‪Information‬‬ ‫‪Replay‬‬

‫51‬

‫61‬

‫ﻋﻨﺎوﻳﻦ دﻳﮕﺮدرﺳﻄﺢ ﺷﺒﮑﻪ‬
‫ﺗﻌﻴﻴﻦ ﻣﺴﻴﺮ ﺑﺴﺘﻪ هﺎ‬
‫ﺑ ﺮاﯼ اﻧﺘﻘ ﺎل ﭘ ﯽ درﭘ ﯽ دادﻩ ه ﺎ ﺑ ﻪ دﻧﺒ ﺎل ه ﻢ از ﻃﺮﻳ ﻖ ﺷ ﺒﮑﻪ ﺑ ﺴﺘﻪ ه ﺎ ﺑﺎﻳ ﺪ از ﻣﺒﺪاءﺷ ﺎن ﺑ ﻪ ﻣﻘ ﺼﺪﺷﺎن‬ ‫ﺣﻤ ﻞ ﺷ ﻮﻧﺪ ﺗﻌﻴ ﻴﻦ ﻣ ﺴﻴﺮ ﻓﺮاﻳﻨ ﺪ اﻧﺘﻘ ﺎل ﺑ ﺴﺘﻪ اﯼ از ﻳ ﮏ ﺷ ﺒﮑﻪ ﺑ ﻪ ﺷ ﺒﮑﻪ دﻳﮕ ﺮ ﺑ ﺎ ه ﺪف ﭘ ﻴﺶ ﺑ ﺮدن‬ ‫ﺑ ﺴﺘﻪ ﺑ ﻪ ﺳ ﻤﺖ ﻣﻘ ﺼﺪش در ﻣ ﺴﻴﺮﯼ ﺑ ﺎ راﻧ ﺪﻣﺎن ﻧ ﺴﺒﯽ ﻣ ﯽ ﺑﺎﺷ ﺪ ﺗﻌﻴ ﻴﻦ ﻣ ﺴﻴﺮ ﺑ ﺎ ﻣ ﺴﻴﺮﻳﺎب ه ﺎ اﺟ ﺮا ﻣ ﯽ‬ ‫ﮔﺮدد ﻣﺴﻴﺮﻳﺎﺑﻬﺎ ﻣﺴﻴﺮﯼ راﺗﻌﻴﻴﻦ‬ ‫ﻣ ﯽ ﻧﻤﺎﻳﻨ ﺪ ﮐ ﻪ ﺑ ﺴﺘﻪ ﺑﺎﻳ ﺪ از ﻃﺮﻳ ﻖ ﺷ ﺒﮑﻪ اﻧﺘﺨ ﺎب ﻧﻤﺎﻳ ﺪ و اﻳ ﻦ ﻣ ﺴﻴﺮ از ﭘﺮﺷ ﯽ ﺑ ﻪ ﭘ ﺮش دﻳﮕ ﺮ ﺗﻌﻴ ﻴﻦ‬ ‫ﻣﯽ ﺷﻮد و‬ ‫ﺑﺴﺘﻪ هﺎ را دﺳﺘﻪ ﺑﻨﺪﯼ و ﺑﺮاﯼ اﻧﺘﻘﺎل از ﻃﺮﻳﻖ ﺷﺒﮑﻪ ﺑﻪ ﻗﻄﻌﺎت ﻣﻨﻈﻢ ﺗﻘﺴﻴﻢ ﻣﯽ ﻧﻤﺎﻳﺪ‬ ‫ﺑﻴ ﺸﺘﺮ ﺷ ﺒﮑﻪ ه ﺎﯼ اﻣ ﺮوزﯼ از ﻣ ﺴﻴﺮﻳﺎﺑﯽ دﻳﻨ ﺎﻣﻴﮑﯽ اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﮐﻨﻨ ﺪ ﮐ ﻪ ﻣ ﺴﺮﻳﺎﺑﻬﺎ ﺧ ﻮد ﻣ ﺴﻴﺮﯼ را‬ ‫ﮐ ﻪ ﺑ ﺴﺘﻪ ه ﺎ اﺳ ﺘﻔﺎدﻩ ﺧﻮاهﻨ ﺪ راﻧﻤ ﻮد را ﺗﻌﻴ ﻴﻦ ﻣ ﯽ ﻧﻤﺎﻳﻨ ﺪ .ﻣ ﺴﻴﺮﻳﺎب ه ﺎ در ﺑ ﻴﻦ ﺧﻮدﺷ ﺎن ﺑ ﺎ اﺳ ﺘﻔﺎدﻩ از‬ ‫ﻣ ﺴﻴﺮﻳﺎﺑﯽ ﺗﺒ ﺎدل اﻃﻼﻋ ﺎت ﻣ ﯽ ﻧﻤﺎﻳﻨ ﺪ و ﺑﻬﺘ ﺮﻳﻦ ﻣ ﺴﻴﺮهﺎ را ﻳ ﺮاﯼ اﻧﺘﻘ ﺎل ﺑ ﺴﺘﻪ ه ﺎ ﺗﻌﻴ ﻴﻦ ﻣ ﯽ ﮐﻨﻨ ﺪ ﺗﻌ ﺪاد‬ ‫زﻳﺎدﯼ از ﭘﺮوﺗﮑﻞ هﺎﯼ ﻣﺴﻴﺮﻳﺎﺑﯽ ﺑﺎ ﭘﻴﭽﻴﺪﮔﯽ هﺎﯼ ﻣﺨﺘﻠﻒ اﺧﺘﺮاع ﺷﺪﻩ اﻧﺪ ﮐﻪ ﻋﺒﺎرﺗﻨﺪ از:‬ ‫‪Border Gateway (BGP),Open Shortest Path First (OSP),Routing‬‬ ‫.)‪Information Protocol (RIP‬‬ ‫ﮔﺰﻳﻨ ﻪ ﻣ ﺴﻴﺮ ﻳ ﺎﺑﯽ دﻳﮕ ﺮ داراﯼ ﻣ ﺴﻴﺮ ه ﺎﯼ ﺛﺎﺑ ﺖ ﻣ ﯽ ﺑﺎﺷ ﻨﺪ. در ﻣ ﺴﻴﺮ ﺛﺎﺑ ﺖ، ﺗﻤ ﺎم داد و ﺳ ﺘﺪ دادﻩ ه ﺎ ﺑ ﺎ‬ ‫هﻤ ﺎن ﺁدرس ﻣﻘ ﺼﺪ هﻤﻴ ﺸﻪ در ﻳ ﮏ ﺟﻬ ﺖ ارﺳ ﺎل ﻣ ﯽ ﮔﺮدﻧ ﺪ )ﺑ ﺪون ﺗﻮﺟ ﻪ ﺑ ﻪ ﺻ ﺪﻣﻪ اﺟﺘﻨ ﺎب ﻧﺎﭘ ﺬﻳﺮ در‬ ‫ارﺗﺒ ﺎط ﺑ ﺎ ه ﺮ ﻣ ﻮرد ﻇﺮﻓﻴ ﺖ دﻳﮕ ﺮ( از ﻣ ﺴﻴﺮهﺎﯼ ﺛﺎﻟ ﺚ ﻏﺎﻟﺒ ﺎ ﺑ ﺮاﯼ ﻣ ﺴﻴﺮ ﻳﺎﺑﻬ ﺎﻳﯽ اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﺷ ﻮد ﮐ ﻪ‬ ‫در ﺁن ﺑ ﻪ ﻧ ﺪرت ﻣ ﺴﻴﺮ ﻳﺎﺑﻬ ﺎﻳﯽ ﺗﻐﻴﻴ ﺮ ﻣ ﯽ ﻧﻤﺎﻳ ﺪ ، و ﻧ ﺴﺒﺖ ﺑ ﻪ ﻣ ﻮارد اﻳﻤﻨ ﯽ ، دﻳﻨ ﺎﻣﻴﮑﯽ ، ﻣ ﺴﻴﺮ ه ﺎﻳﯽ‬

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‫‪Learning TCP/IP‬‬

‫‪BY: Nasser-Desperado‬‬

‫ﻣﻄﻠ ﻮب و دﻟﺨ ﻮاﻩ ﻧﻤ ﯽ ﺑﺎﺷ ﻨﺪ . ﻣ ﺴﻴﺮ ه ﺎﯼ ﺛﺎﻟ ﺚ ﻏﺎﻟﺒ ﺎ در دروازﻩ اﻳﻨﺘﺮﻧﺘ ﯽ را ﻣ ﯽ ﺳ ﺎزﻧﺪ ، ﺑ ﻪ ﺷ ﺪت‬ ‫ﻣﺮزﺑﻨﺪﯼ ﻣﯽ ﺷﻮﻧﺪ.‬ ‫‪ IP‬ﮔﺰﻳﻨ ﻪ ﻣ ﺴﻴﺮ ﻳ ﺎﺑﯽ دﻳﮕ ﺮﯼ را اراﻳ ﻪ ﻣ ﯽ ﻧﻤﺎﻳﺪﮐ ﻪ ﻣ ﺴﻴﺮ ﻳ ﺎﺑﯽ ﻣﺒ ﺪا دﺳ ﺘﮕﺎﻩ ﻣﺒ ﺪا ﺑ ﺴﺘﻪ اﯼ را اﻳﺠ ﺎد‬ ‫ﻣ ﯽ ﻧﻤﺎﻳ ﺪ و ﻣ ﺴﻴﺮﯼ را ﺗﻌﻴ ﻴﻦ ﺧﻮاه ﺪ ﻧﻤ ﻮد ﮐ ﻪ ﺑ ﺴﺘﻪ ه ﺎ ﻣ ﯽ ﺑﺎﺷ ﻨﺪ ﮐ ﻪ ﺑ ﺴﺘﻪ از ﻃﺮﻳ ﻖ ﺁن از درون‬ ‫ﺷﺒﮑﻪ ﻋﺒﻮر ﺧﻮاهﺪ ﻧﻤﻮد.‬

‫ﺗﻔﺴﻴﺮ ﺁدرس ﺷﺒﮑﻪ‬
‫ﺑﻠ ﻮﮎ ﺁدرﺳ ﻬﺎﯼ ‪ IP‬ﺑ ﻪ ﺳ ﺎزﻣﺎﻧﻬﺎﯼ ﻣﺨﺘﻠ ﻒ و ﻓ ﺮاهﻢ ﮐﻨﻨ ﺪﮔﺎن ﺳ ﺮوﻳﺲ اﻳﻨﺘﺮﻧﺘ ﯽ ﮔﻮﻧ ﺎﮔﻮن اﺧﺘ ﺼﺎص‬ ‫دادﻩ ﻣ ﯽ ﺷ ﻮد . ﺳ ﺎﻟﻬﺎ ﻗﺒ ﻞ زﻣ ﺎﻧﯽ ﮐ ﻪ ﭘ ﻴﺶ ﺑﻴﻨ ﯽ اﺗ ﺼﺎل ﺑ ﻪ اﻳﻨﺘﺮﻧ ﺖ ﻧﻴ ﺰ ﻗﺎﺑ ﻞ ﭘ ﻴﺶ ﺑﻴﻨ ﯽ ﺑ ﻮد ، ﻳﮑ ﺴﺮﯼ‬ ‫ﺳ ﺎزﻣﺎﻧﻬﺎ ﺷ ﻤﺎرﻩ ﺁدرس ه ﺎﯼ اﻳﻨﺘﺮﻧﺘ ﯽ ﺗ ﺼﺎدﻓﯽ را اﻧﺘﺨ ﺎب ﮐﺮدﻧ ﺪ و ﺑ ﺎ اﺳ ﺘﻔﺎدﻩ از اﻳ ﻦ ﺁدرس ه ﺎﯼ‬ ‫ﺗ ﺼﺎدﻓﯽ ‪ ، IP‬ﺳ ﺎﺧﺖ ﺷ ﻴﮑﻪ ه ﺎﯼ ‪ IP‬ﺧ ﻮد را ﺁﻏ ﺎز ﻧﻤﻮدﻧ ﺪ و ﺑﻨﻴﺎﻧﮕ ﺬاران ﺷ ﺒﮑﻪ اﯼ را ﺧﻮاهﻴ ﺪ دﻳ ﺪ‬ ‫ﮐ ﻪ از ﺷ ﻤﺎرﻩ دﻟﺨ ﻮاﻩ ﺧ ﻮد اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﮐﻨﻨ ﺪ )ﻣ ﺜﻼ ﻣ ﻦ ﺧ ﻮدم 4 را دوﺳ ﺖ دارم( و ﺷ ﺒﮑﻪ ﮐﻠ ﯽ را ﺑ ﺮ‬ ‫اﺳ ﺎس ﺁن ﺷ ﻤﺎرﻩ ﻣ ﯽ ﺳ ﺎزﻧﺪ ) ﺑ ﻪ ه ﺮ ﻣ ﻮردﯼ ﺁدرس ‪ IP‬ﺑ ﻪ ﺷ ﮑﻞ 4.‪ x.y.z‬ﻣ ﯽ ده ﺪ(. اﻳ ﻦ ﺁدرﺳ ﻬﺎ‬ ‫ﻏﺎﻟﺒ ﺎ ﺑ ﻪ ﺻ ﻮرت ﺁدرﺳ ﻬﺎﯼ ﻣﻨﻄﻘ ﯽ ﻧﺎﻣﮕ ﺬارﯼ ﻣ ﯽ ﮔﺮدﻧ ﺪ ﺑ ﺮاﯼ اﻳﻨﮑ ﻪ ﺑﻄ ﻮر رﺳ ﻤﯽ ﺑ ﻪ ﺳ ﺎزﻣﺎن‬ ‫دﻳﮕ ﺮﯼ اﺧﺘ ﺼﺎص دادﻩ ﻣ ﯽ ﺷ ﻮد. ﻣﺘﺎﺳ ﻔﺎﻧﻪ، اﮔ ﺮ ﮐ ﺴﯽ ﺑ ﺎ اﺳ ﺘﻔﺎدﻩ از ﺁدرﺳ ﻬﺎﯼ ﻣﻨﻄﻘ ﯽ ﺑﺨﻮاه ﺪ ﺑ ﻪ‬ ‫اﻳﻨﺘﺮﻧ ﺖ ﻣﺘ ﺼﻞ ﮔ ﺮدد ، ﺑﺎﻳ ﺪ از دو ﺷ ﺒﮑﻪ در اﻳﻨﺘﺮﻧ ﺖ ﺑ ﺎ ﺁدرﺳ ﻬﺎﯼ ‪ IP‬ﻳﮑ ﺴﺎن اﺳ ﺘﻔﺎدﻩ ﻧﻤﺎﻳ ﺪ. اﻳ ﻦ‬ ‫وﺿ ﻌﻴﺖ ﺑ ﻪ ﻃ ﻮر ﺟ ﺪﯼ در ﻣ ﺴﻴﺮﻳﺎﺑﯽ ﺗﻮﻟﻴ ﺪ اﺷ ﮑﺎل ﻣ ﯽ ﻧﻤﺎﻳ ﺪ. ﺑ ﺮاﯼ اﻳﻨﮑ ﻪ ﻣ ﺴﻴﺮﻳﺎﺑﻬﺎﯼ اﻳﻨﺮﻧﺘ ﯽ ﻧﻤ ﯽ‬ ‫داﻧﻨﺪ ﮐﻪ داد و ﺳﺘﺪ دادﻩ هﺎﯼ اﻳﻦ ﺁدرس دوﺑﻞ ﻣﻘﺼﺪ را ﺑﻪ ﮐﺠﺎ ارﺳﺎل ﻧﻤﺎﻳﻨﺪ.‬ ‫ﺑﻌ ﻼوﻩ ، در ﺗ ﻼش ﺑ ﻪ اﺗ ﺼﺎل ﺑ ﺎ اﻳﻨﺘﺮﻧ ﺖ ، ﻓ ﻀﺎﯼ ﺁدرس ‪ IP‬ﺑ ﺎ ﺑ ﺮاﯼ ه ﺮ ﻓ ﺮد وﺟ ﻮد دارﻧ ﺪ. ﺑﻨ ﺎﺑﺮاﻳﻦ ،‬ ‫‪ IETF‬ﻳﮑ ﺴﺮﯼ ﺷ ﻤﺎرﻩ ﺁدرﺳ ﻬﺎ را ﺑ ﺮاﯼ اﻳﺠ ﺎد ﺷ ﺒﮑﻪ ه ﺎﯼ ﺧ ﺼﻮﺻﯽ ‪ IP‬در ﻣ ﻮرد 9181 ‪RFC‬‬ ‫ﺗﻨﻈ ﻴﻢ ﻧﻤ ﻮد ﻣ ﯽ ﺗﻮاﻧﻴ ﺪ ﺷ ﺒﮑﻪ ‪ IP‬ﺧ ﻮد را ﺑ ﺎ اﺳ ﺘﻔﺎدﻩ از ﺁدرﺳ ﻬﺎﯼ ﺗﻨﻈ ﻴﻢ ﺷ ﺪﻩ ‪ IP‬ﻣﺜ ﻞ‬ ‫‪ 192.168.y.z‬و‪ 10x.y.z‬و‪ yz‬ﻳ ﺎ ، ‪ 172.16.y.z‬در اﻳ ﻦ ﻣﺤ ﻞ ﺑ ﺴﺎزﻳﺪ . اﮔ ﺮ داده ﺎﻳﯽ را ﺑ ﻪ ﻳﮑ ﯽ‬ ‫از ﺁﻳ ﻦ ﺁدرﺳ ﻬﺎ در اﻳﻨﺘﺮﻧ ﺖ ارﺳ ﺎل ﮐﻨﻴ ﺪ ، ﺁن داد ه ﻪ از دﺳ ﺖ ﺧﻮاهﻨ ﺪ رﻓ ﺖ ، ﺑ ﺮاﯼ اﻳﻨﮑ ﻪ اﻳ ﻦ‬ ‫ﺗﻨﻈﻴﻤ ﺎت ﻣﻨﺤ ﺼﺮ ﺑ ﻪ ﻓ ﺮد ﻧﻤ ﯽ ﺑﺎﺷ ﺪ و ﻏﻴﺮﻗﺎﺑ ﻞ ﻣ ﺴﻴﺮ ﻧﺎﻣﻴ ﺪﻩ ﻣ ﯽ ﺷ ﻮﻧﺪ ﺑ ﺮاﯼ اﻳﻨﮑ ﻪ ه ﻴﭻ ﻣ ﺴﻴﺮ ﻳ ﺎﺑﯽ‬ ‫در اﻳﻨﺘﺮﻧﺖ ﻧﺨﻮاهﺪ داﻧﺴﺖ ﮐﻪ ﺑﻪ ﭼﻪ روﺷﯽ ﺑﻪ اﻳﻦ ﺁدرﺳﻬﺎﯼ ﻏﻴﺮ واﺣﺪ دﺳﺖ ﭘﻴﺪا ﻧﻤﺎﻳﻴﺪ.‬ ‫ﭼﻄ ﻮر دﺳﺘﺮﺳ ﯽ ﺑ ﻪ ﺷ ﺒﮑﻪ ﺷ ﺒﮑﻪ را ﭘ ﺸﺘﻴﺒﺎﻧﯽ ﻧﻤ ﺎﻳﻴﻢ ﺑ ﺎ اﺳ ﺘﻔﺎدﻩ ار ﺁدرﺳ ﻬﺎﯼ ﻣﻨﻄﻘ ﯽ ﻳ ﺎ ﺗﻨﻈﻴﻤ ﺎت‬ ‫ﺗﻮﺿﻴﺢ دادﻩ ﺷﺪﻩ در ?8191 ‪RFC‬‬ ‫ﺟ ﻮاب ﺗﺮﺳ ﻢ اﻳ ﻦ ﺁدرﺳ ﻬﺎﯼ ﻣ ﺴﺎﻟﻪ ﺳ ﺎز ﺑ ﻪ ﺁدرﺳ ﻬﺎﯼ ﻣﻌﺘﺒ ﺮ ‪ IP‬در ﻣ ﺴﻴﺮ ﻳ ﺎب ﺷ ﺒﮑﻪ ﻳ ﺎ دﻳ ﻮارﻩ ﺁﺗ ﺶ‬ ‫ﺑ ﺎ اﺳ ﺘﻔﺎدﻩ ازﺗﮑﻨﻴﮑ ﯽ ﻣ ﯽ ﺑﺎﺷ ﺪ ﮐ ﻪ ﺗﻔ ﺴﻴﺮ ﺁأرس ﺷ ﺒﮑﻪ )‪ (NAT‬ﻧ ﺎم دارد. ﺑ ﺮاﯼ اﻧﺠ ﺎم ‪، NAT‬‬ ‫دروازﻩ اﯼ ﺑ ﻴﻦ ﺷ ﺒﮑﻪ ﺑ ﺎ ﺁدرس ﻣﻨﻄﻘ ﯽ ﻳ ﺎ ﺗﻨﻈ ﻴﻢ ﺷ ﺪﻩ و اﻳﻨﺘﺮﻧ ﺖ ﻗ ﺮار ﻣ ﯽ ﮔﻴ ﺮد. وﻗﺘ ﯽ ه ﺮ ﺑ ﺴﺘﻪ از‬ ‫ﺷ ﺒﮑﻪ داﺧﻠ ﯽ ﺑ ﻪ اﻳﻨﺘﺮﻧ ﺖ ﻣ ﯽ رود ، اﻳ ﻦ دروازﻩ ﺁدرس ﻣﻨﻄﻘ ﯽ ﻳ ﺎ ﻏﻴ ﺮ ﻗﺎﺑ ﻞ ﻣ ﺴﻴﺮ ﻳ ﺎﺑﯽ ﺷ ﺒﮑﻪ داﺧﻠ ﯽ‬ ‫در ﻋﻨ ﻮان ﺑ ﺴﺘﻪ را ﺑ ﺎ ﺁدرس ‪ IP‬واﺣ ﺪ و ﻗﺎﺑ ﻞ ﻣ ﺴﻴﺮﻳﺎﺑﯽ ﺗ ﻮﻳﺾ ﻣ ﯽ ﮐﻨ ﺪ. وﻗﺘ ﯽ ﭘﺎﺳ ﺨﻬﺎ ﺑﺮﻣ ﯽ ﮔﺮدﻧ ﺪ‬ ‫، دروازﻩ اﻳ ﻦ ﺑ ﺴﺘﻪ ه ﺎ را درﻳﺎﻓ ﺖ ﺧﻮاه ﺪ ﻧﻤ ﻮد ، و ﺁدرﺳ ﻬﺎﯼ ﻣﻘ ﺼﺪ ‪ IP‬را ﻗﺒ ﻞ از ارﺳ ﺎل از ﻃﺮﻳ ﻖ‬ ‫ﺷﺒﮑﻪ داﺧﻠﯽ ، از ﻧﻮ ﺑﺎزﻧﻮﻳﺴﯽ ﻣﯽ ﮐﻨﺪ.‬ ‫دروازﻩ ﻣﯽ ﺗﻮاﻧﺪ ﺁدرﺳﻬﺎﻳﯽ را ﺑﺮاﯼ ‪ NAT‬ﺑﻄﺮﻳﻖ ﻣﺨﺘﻠﻒ ﻃﺮح رﻳﺰﯼ ﻧﻤﺎﻳﺪ ﮐﻪ ﻋﺒﺎرﺗﻨﺪ از:‬ ‫ﻃ ﺮح رﻳ ﺰﯼ ﺑ ﺮاﯼ ﺁدرس ﻣﺠ ﺰاﯼ ‪ IP‬ﺧ ﺎرﺟﯽ : ﺑ ﺮاﯼ اﻳ ﻦ ﻧ ﻮع ‪ ،NAT‬ه ﺮ ﺑ ﺴﺘﻪ اﯼ ﮐ ﻪ از ﺷ ﺒﮑﻪ‬ ‫داﺧﻠ ﯽ ﺑﻴ ﺮون ﻣ ﯽ ﺁﻳ ﺪ ﺑ ﺮاﯼ ﺁدرس ‪ IP‬ﻣﺠﺰاﻳ ﯽ ﻃ ﺮح ﻣ ﯽ ﺷ ﻮد. در اﻳﻨﺘﺮﻧ ﺖ، ﺗﻤ ﺎم داد وﺳ ﺘﺪهﺎ دادﻩ‬ ‫ه ﺎ از ﺁدرس ‪ IP‬دﺳ ﺘﮕﺎﻩ ‪ NAT‬ﺣﺎﺻ ﻞ ﻣ ﯽ ﮔ ﺮدد. اﻳ ﻦ ﺗﮑﻨﻴ ﮏ ﺁدرس ده ﯽ ﮐ ﻪ راﻧ ﺪﻣﺎن ﺑ ﺎﻻﻳﯽ دارد و‬ ‫ﺑﻄ ﻮر ﻣﺘ ﺪاول ﺑ ﺮاﯼ اﺗ ﺼﺎل ﻳ ﮏ ﺷ ﺒﮑﻪ ﺑ ﺰرگ ﺑ ﻪ اﻳﻨﺘﺮﻧ ﺖ اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﺷ ﻮد، ﭼ ﻮن ﺗﻌ ﺪاد ﻣﺤ ﺪودﯼ از‬ ‫ﺁدرﺳﻬﺎﯼ ‪ IP‬در دﺳﺘﺮس ﻣﯽ ﺑﺎﺷﻨﺪ.‬ ‫ﻃ ﺮح رﻳ ﺰﯼ ﺗ ﮏ ﺑ ﻪ ﺗ ﮏ : دروازﻩ ﻣ ﯽ ﺗﻮاﻧ ﺪ ه ﺮ دﺳ ﺘﮕﺎﻩ روﯼ ﺷ ﺒﮑﻪ داﺧﻠ ﯽ را ﺑ ﻪ ﺁدرس ‪ IP‬ﻣﻌﺘﺒ ﺮ و‬ ‫واﺣ ﺪ هﻤ ﺮاﻩ ﺑ ﺎ ه ﺮ دﺳ ﺘﮕﺎﻩ ﻃ ﺮح رﻳ ﺰﯼ ﻧﻤﺎﻳ ﺪ. ﺑﻨ ﺎﺑﺮاﻳﻦ ، ﺑ ﻪ ﻧﻈ ﺮ ﻣ ﯽ رﺳ ﺪ داد و ﺳ ﺘﺪ دادﻩ ه ﺎ از ﻳ ﮏ‬ ‫ﮔ ﺮوﻩ ﺁدرس ‪ IP‬ﺑ ﻪ وﺟ ﻮد ﻣ ﯽ ﺁﻳ ﺪ. اﻳ ﻦ ﺗﮑﻨﻴ ﮏ ﻏﺎﻟﺒ ﺎ ﺑ ﺮاﯼ ﻃ ﺮح رﻳ ﺰﯼ درﺧﻮاﺳ ﺘﻬﺎﯼ ﮐ ﺎرﺑﺮ از ﻃﺮﻳ ﻖ‬ ‫اﻳﻨﺘﺮﻧﺖ ﺑﻪ ﺳﺮوﻳﺲ هﻨﺪﻩ هﺎﯼ ﺷﺒﮑﻪ ﺟﺎﻧﺒﯽ ﻣﺜﻞ ﺳﺮوﻳﺲ دهﻨﺪﻩ وب اﺳﺘﻔﺎدﻩ ﻣﯽ ﺷﻮد.‬ ‫ﺁدرس اﺧﺘ ﺼﺎﺻﯽ از ﻟﺤ ﺎظ دﻳﻨ ﺎﻣﻴﮑﯽ : دروازﻩ ﻣ ﯽ ﺗﻮاﻧ ﺪ ﺗﻘ ﺴﻴﻢ ﮐﻨﻨ ﺪﻩ ﺗﻌ ﺪاد زﻳ ﺎدﯼ از ﺁدرس ﻏﻴ ﺮ‬ ‫ﻗﺎﺑ ﻞ ﻣ ﺴﻴﺮ ﻳ ﺎﺑﯽ ‪ IP‬ﺑ ﻪ ﺗﻌ ﺪاد ﮐﻤﺘ ﺮﯼ از ﺁدرﺳ ﻬﺎﯼ ﻣﻌﺘﺒ ﺮ ‪ IP‬ﺑﺎﺷ ﺪ. اﻳ ﻦ روش ﺗﮑﻨﻴ ﮏ ه ﺎﯼ دﻳﮕ ﺮ‬ ‫ﻣﺘﺪاول ﺗﺮ اﺳﺖ.‬ ‫ﺑ ﺮاﯼ ﺣﻔ ﻆ ﺁدرﺳ ﻬﺎﯼ ‪ IP,NAT‬اﻣ ﺮوزﻩ در اﻳﻨﺘﺮﻧ ﺖ ﺑ ﺴﻴﺎر ﻣ ﻮرد اﺳ ﺘﻔﺎدﻩ ﻗ ﺮار ﻣ ﯽ ﮔﻴ ﺮد. ﺁﻳ ﺎ ‪NAT‬‬ ‫اﻳﻤﻨ ﯽ را ﺑﻬﺘ ﺮ ﻣ ﯽ ﺳ ﺎزد؟ ﺑ ﻪ ﻣﺨﻔ ﯽ ﺳ ﺎزﯼ ﮐ ﺎرﺑﺮد ﺁدرس داﺧﻠ ﯽ ‪ IP‬ﺷ ﺒﮑﻪ ﮐﻤ ﮏ ﻣ ﯽ ﻧﻤﺎﻳ ﺪ. ﮐ ﻪ ه ﺮﻩ‬ ‫ﻣ ﯽ ﺗﻮاﻧ ﺪ اﺳ ﺘﻔﺎدﻩ ﮐﻨ ﺪ ﺗ ﺎ ﻧﻘ ﺸﻪ ﺗﻮﭘﻮﻟ ﻮژﯼ ﺷ ﺒﮑﻪ را ﺑ ﻪ وﺟ ﻮد ﺁورد. اﻟﺒﺘ ﻪ ، ﺧ ﻮد ‪ NAT‬اﻳﻤﻨ ﯽ‬

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‫‪Learning TCP/IP‬‬

‫‪BY: Nasser-Desperado‬‬

‫ﺑ ﺴﻴﺎرﯼ ﭘﻴ ﺸﻨﻬﺎد ﻣ ﯽ ﮐﻨ ﺪ. در ﺣ ﺎﻟﯽ ﮐ ﻪ هﮑﺮه ﺎ ﻧﻤ ﯽ ﺗﻮاﻧﻨ ﺪ ﺑﻄ ﻮر ﻣ ﺴﺘﻘﻴﻢ ﺑ ﺴﺘﻪ ه ﺎﻳﯽ را از ﻃﺮﻳ ﻖ‬ ‫دروازﻩ ‪ NAT‬ارﺳ ﺎل ﻧﻤﺎﻳﻨ ﺪ. دروازﻩ ‪ NAT‬ﺁدرﺳ ﻬﺎﻳﯽ را از ﺳ ﻮﯼ هﮑ ﺮ ﺗﺮﺳ ﻴﻢ ﻣ ﯽ ﻧﻤﺎﻳ ﺪ. ﺑ ﺪﻳﻦ‬ ‫دﻟﻴﻞ ، اﮔﺮ اﻳﻤﻨﯽ ﻻزم ﺑﺎﺷﺪ ﺗﮑﻨﻴﮑﻬﺎﯼ ‪ NAT‬ﺑﺎﻳﺪ ﺑﺎ اﺟﺮاﯼ دﻳﻮارﻩ ﺁﺗﺶ اﻳﻤﻦ ﺗﺮﮐﻴﺐ ﺷﻮد.‬

‫دﻳﻮارﻩ هﺎﯼ ﺁﺗﺶ: ﻣﺎﻣﻮران ﮐﻨﺘﺮل ﻧﻘﻞ و اﻧﺘﻘﺎل دادﻩ هﺎ ﺷﺒﮑﻪ و دروازﻩ ﺑﺎﻧﻬﺎ‬
‫دﻳ ﻮارﻩ ه ﺎﯼ ﺁﺗ ﺶ ، اﺑ ﺰارﯼ ﻣ ﯽ ﺑﺎﺷ ﻨﺪ ﮐ ﻪ ﺟﺮﻳ ﺎن ﻧﻘ ﻞ و اﻧﺘﻘ ﺎل دادﻩ ه ﺎﯼ ﻋﺒ ﻮرﯼ ﺑ ﻴﻦ ﺷ ﺒﮑﻪ ه ﺎ را‬ ‫ﮐﻨﺘ ﺮل ﻣ ﯽ ﻧﻤﺎﻳ ﺪ. اﻳ ﻦ اﺑ ﺰار در ﻣ ﺮز ﺑ ﻴﻦ ﺷ ﺒﮑﻪ ه ﺎ ﻗ ﺮار ﻣ ﯽ ﮔﻴ ﺮ ، و ﺑ ﻪ ﺻ ﻮرت دروازﻩ ه ﺎﯼ ﻋﻤ ﻞ ﻣ ﯽ‬ ‫ﮐﻨ ﺪ ﮐ ﻪ ﺗ ﺼﻤﻴﻢ ﻣ ﯽ ﮔﻴﺮﻧ ﺪ ﭼ ﻪ ﻧ ﻮع ارﺗﺒ ﺎﻃﯽ ﺑﺎﻳ ﺪ ﻣﺠ ﺎز و از ﭼ ﻪ ارﺗﺒ ﺎﻃﯽ ﺑﺎﻳ ﺪ ﻣﺠ ﺎز ﺑﺎﺷ ﺪ و از ارﺗﺒ ﺎﻃﯽ‬ ‫ﺑﺎﻳ ﺪ اﻣﺘﻨ ﺎع ﺷ ﻮد. ﺑ ﺎ ﻧﮕ ﺎﻩ ﺑ ﻪ ﺳ ﺮوﻳﺲ ه ﺎ ، ﺁدرﺳ ﻬﺎ ، و اﺣﺘﻤ ﺎﻻ ﺣﺘ ﯽ ﮐ ﺎرﺑﺮان ﻣ ﺎﻣﻮر ﻧﻘ ﻞ و اﻧﺘﻘ ﺎل‬ ‫دادﻩ ه ﺎ ، دﻳ ﻮارﻩ ه ﺎﯼ ﺁﺗ ﺶ ﺗﻌﻴ ﻴﻦ ﻣ ﯽ ﻧﻤﺎﻳ ﺪ ﮐ ﻪ اﺗ ﺼﺎﻻت ﺑﺎﻳ ﺪ از ﻃﺮﻳ ﻖ ﺷ ﺒﮑﻪ دﻳﮕ ﺮ ﻣﻨﻘ ﻞ ﮔ ﺮدد. ﺑ ﺪﻳﻦ‬ ‫ﺻﻮرت ، دﻳﻮارﻩ هﺎﯼ ﺁﺗﺶ ﺑﻴﺸﺘﺮ ﻣﯽ ﺗﻮاﻧﺪ ﺑﻪ ﺻﻮرت ﻣﺎﻣﻮران ﺗﺮاﻓﻴﮑﯽ ﺷﺒﮑﻪ ﻋﻤﻞ ﻧﻤﺎﻳﺪ.‬ ‫اﮔ ﺮ دﻳ ﻮار ه ﺎﯼ ﺁﺗ ﺶ ﺑﻄ ﻮر ﺻ ﺤﻴﺢ ﭘﻴﮑﺮﺑﻨ ﺪﯼ ﺷ ﻮﻧﺪ، ﺳﻴ ﺴﺘﻤﻬﺎﯼ ﻳ ﮏ ﺳ ﻤﺖ ﺁن از ﺣﻤﻠ ﻪ هﮑﺮه ﺎ از‬ ‫ﺳ ﻤﺖ دﻳﮕ ﺮ دﻳ ﻮارﻩ ه ﺎﯼ ﺁﺗ ﺶ ﺟﻠ ﻮﮔﻴﺮﯼ ﻣ ﯽ ﻧﻤﺎﻳ ﺪ. هﮑﺮه ﺎ ﺗﻨﻬ ﺎ ﻣ ﯽ ﺗﻮاﻧﻨ ﺪ ﺑ ﻪ ﺳﻴ ﺴﺘﻢ ه ﺎﯼ ﺧﻔﺎﻇ ﺖ‬ ‫ﺷ ﺪﻩ ﺑ ﻪ ﻃﺮﻳﻘ ﯽ دﺳﺘﺮﺳ ﯽ ﭘﻴ ﺪا ﻧﻤﺎﻳﻨ ﺪ ﮐ ﻪ دﻳ ﻮارﻩ ﺁﺗ ﺶ ﺑ ﻪ ﺁﻧﻬ ﺎ اﺟ ﺎزﻩ ﻣ ﯽ دهﻨ ﺪ. ﺳ ﺎزﻣﺎﻧﻬﺎ و ﺷ ﺮﮐﺘﻬﺎ‬ ‫ﺑﻄ ﻮر ﻣﺘ ﺪاول از دﻳ ﻮارﻩ ه ﺎﯼ ﺁﺗ ﺶ ﺑ ﺮاﯼ ﺣﻔﺎﻇ ﺖ ﻓﺮاﺳ ﺎﺧﺘﺎر ﺧ ﻮد از اﻳﻨﺘﺮﻧ ﺖ و از ﺣﻤ ﻼت ارﺗﺒﺎﻃ ﺎت‬ ‫ﺣﺮﻳ ﻒ ﺗﺠ ﺎرﯼ اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﮐﻨﻨ ﺪ. ﺑﻌ ﻼوﻩ، دﻳ ﻮارﻩ ه ﺎﯼ ﺁﺗ ﺶ ﺷ ﺒﮑﻪ داﺧﻠ ﯽ، در ﺣ ﺎل اﻓ ﺰاﻳﺶ و ﺣﻔﺎﻇ ﺖ‬ ‫ﺷﺒﮑﻪ هﺎﯼ ﺣﺴﺎس داﺧﻠﯽ از دﻳﮕﺮ ﺷﺒﮑﻪ هﺎﯼ ﺳﺎزﻣﺎن ﻣﯽ ﺑﺎﺷﻨﺪ.‬ ‫ﻣﻘﺎﻳ ﺴﻪ دﻳﮕ ﺮ ﺑ ﺮاﯼ ﺗﺠ ﺴﻢ دﻳ ﻮارﻩ ﺁﺗ ﺶ، دروازﺑ ﺎن ﺑ ﺎزﯼ ﻓﻮﺗﺒ ﺎل ﻣ ﯽ ﺑﺎﺷ ﺪ. ﮐ ﺎر دروازﺑ ﺎن ﺟﻠ ﻮﮔﺒﺮﯼ‬ ‫از ﮔ ﻞ زدن ﺗ ﻴﻢ ﻣﺨ ﺎﻟﻒ ﻣ ﯽ ﺑﺎﺷ ﺪ. ﺗ ﻮپ ﻓﻮﺗﺒ ﺎل ﭼﻴ ﺰﯼ ﺷ ﺒﻴﻪ ﺑ ﻪ ﺑ ﺴﺘﻪ ﻣ ﯽ ﺳﺎﺷ ﺪ. ﮐ ﺎر دﻳ ﻮارﻩ ﺁﺗ ﺶ‬ ‫ﺟﻠ ﻮﮔﻴﺮﯼ از ارﺳ ﺎل ﺑ ﺴﺘﻪ ه ﺎﯼ ﻧﺎﺧﻮاﺳ ﺘﻪ ﺑ ﻪ داﺧ ﻞ ﺷ ﺒﮑﻪ ﻣ ﯽ ﺑﺎﺷ ﺪ. اﻟﺒﺘ ﻪ ، دروازﺑ ﺎن ﺑﺎﻳ ﺪ اﺟ ﺎزﻩ ده ﺪ‬ ‫ﮐ ﻪ ﺗ ﻮپ از داﺧ ﻞ دروازﻩ ﺑﻴ ﺮون ﮐ ﺸﻴﺪﻩ ﺷ ﻮد ، در ﻧﻬﺎﻳ ﺖ ﻧﻴ ﺰ ﺑ ﺎزﯼ ﭘﺎﻳ ﺎن ﺧﻮاه ﺪ ﻳﺎﻓ ﺖ. دﻳﻮاره ﺎﯼ‬ ‫ﺁﺗ ﺶ ﺑﺎﻳ ﺪ ﻳﮑ ﺴﺮﯼ از ارﺗﺒﺎﻃ ﺎت از ﮐ ﺎر اﻓﺘ ﺎدﻩ ﻧﻴ ﺰ اﺟ ﺎزﻩ ﻋﺒ ﻮر ده ﺪ، ﺑﻨ ﺎﺑﺮاﻳﻦ ﮐ ﺎرﺑﺮان داﺧﻠ ﯽ ﻣ ﯽ‬ ‫ﺗﻮاﻧﻨ ﺪ ﺑ ﻪ ﺷ ﺒﮑﻪ ﺧ ﺎرﺟﯽ دﺳﺘﺮﺳ ﯽ ﭘﻴ ﺪا ﻧﻤﺎﻳﻨ ﺪ ،در ﺣ ﺎﻟﯽ ﮐ ﻪ ﺑﻴ ﺸﺘﺮ ارﺗﺒﺎﻃ ﺎت ورودﯼ رد ﻣ ﯽ ﺷ ﻮﻧﺪ )‬ ‫ﺑﺠﺰ ﺑﺮاﯼ ﺳﺮوﻳﺴﻬﺎﯼ ﺧﺎص(.‬

‫ﻓﻴﻠﺘﺮهﺎﯼ ﻗﺪﻳﻤﯽ ﺑﺴﺘﻪ‬
‫ﻓﻴﻠﺘﺮه ﺎﯼ ﻗ ﺪﻳﻤﯽ ﺑ ﺴﺘﻪ ﺑ ﺮاﯼ ﺑ ﻴﺶ از ﻳ ﮏ ده ﻪ ﻣ ﻮرد اﺳ ﺘﻔﺎدﻩ ﻗ ﺮار ﮔﺮﻗﺘﻨ ﺪ، و ﻣ ﯽ ﺗﻮاﻧﻨ ﺪ روﯼ‬ ‫ﻣ ﺴﻴﺮﻳﺎب ﻳ ﺎ دﻳ ﻮارﻩ ﺁﺗ ﺶ اﺟ ﺮا ﺷ ﻮﻧﺪ. ﺑ ﺮ اﺳ ﺎس ﻧ ﺎم ﺁﻧﻬ ﺎ، ﻓﻴﻠﺘﺮه ﺎﯼ ﺑ ﺴﺘﻪ روﯼ ﺗ ﮏ ﺗ ﮏ ﺑ ﺴﺘﻪ ه ﺎ،‬ ‫ﺗﺤﻠﻴ ﻞ اﻃﻼﻋ ﺎت و ﺟﻬ ﺖ ﻋﻨ ﻮان ﺁﻧﻬ ﺎ ﺗﺎﮐﻴ ﺪ دارد. دﺳ ﺘﮕﺎﻩ ﻗ ﺪﻳﻤﯽ ﻓﻴﻠﺘ ﺮ ﺑ ﺴﺘﻪ ه ﺮ ﺑ ﺴﺘﻪ ﻋﺒ ﻮرﯼ از ﺁﻧ ﺮا‬ ‫ﺗﺤﻠﻴ ﻞ ﻣ ﯽ ﻧﻤﺎﻳ ﺪ ﺗ ﺎ ﺗ ﺼﻤﻴﻢ ﺑﮕﻴ ﺮد ﺁﻳ ﺎ ﺑ ﺴﺘﻪ ﺑﺎﻳ ﺪ از اﻧﺘﻘ ﺎل ﺁن ﺟﻠ ﻮﮔﻴﺮﯼ ﮔ ﺮدد. ﻓﻴﻠﺘﺮه ﺎﯼ ﻗ ﺪﻳﻤﯽ ﺑ ﺴﺘﻪ‬ ‫اﻳﻦ ﺗﺼﻤﻴﻢ را ﺑﺎ اﺳﺘﻔﺎدﻩ از اﻃﻼﻋﺎت زﻳﺮ اﻧﺠﺎم ﻣﯽ دهﺪ.‬ ‫ﺁدرس ‪ IP‬ﻣﺒ ﺪا : ﺁﻳ ﺎ ﺑ ﺴﺘﻪ ﮐ ﻪ از ﺁدرس ‪ IP‬ﻣ ﯽ ﺁﻳ ﺪ، ﺑﺎﻳ ﺪ در هﻨﮕ ﺎم ورود ﺑ ﻪ ﺷ ﺒﮑﻪ ﻣﺠﻮزداﺷ ﺘﻪ‬ ‫ﺑﺎﺷ ﺪ؟ اﻳ ﻦ اﻃﻼﻋ ﺎت از ﻋﻨ ﻮان ‪ HP‬ﺑ ﺴﺘﻪ ﺟﻤ ﻊ ﺁورﯼ ﻣ ﯽ ﺷ ﻮد، دﺳ ﺘﮕﺎﻩ ﻣﺒ ﺪا ﻳ ﺎ ﺷ ﺒﮑﻪ ارﺳ ﺎل ﮐﻨﻨ ﺪﻩ‬ ‫را ﻧﺸﺎن ﻣﯽ دهﺪ.‬ ‫ﺁدرس ‪ IP‬ﻣﻘ ﺼﺪ : ﺁﻳ ﺎ ﺑ ﺴﺘﻪ ﺑ ﻪ ﺳ ﻤﺖ ﺳ ﺮوﻳﺲ ﮐﻨﻨ ﺪﻩ اﯼ ﮐ ﻪ ﺑﺎﻳ ﺪ اﻳ ﻦ ﻧ ﻮع ﻧﻘ ﻞ و اﻧﺘﻘ ﺎل دادﻩ ه ﺎ را‬ ‫درﻳﺎﻓ ﺖ ﻧﻤﺎﻳ ﺪ، ارﺳ ﺎل ﻣ ﯽ ﮔ ﺮدد؟ اﻳ ﻦ زﻣﻴﻨ ﻪ، از ﻋﻨ ﻮان ‪ IP‬ﺑ ﺴﺘﻪ ﻧﻴ ﺰ دﺳ ﺘﮕﺎﻩ ﻣ ﻮرد ﻧﻈ ﺮ ﻣﻘ ﺼﺪ ﻳ ﺎ‬ ‫ﺷﺒﮑﻪ ﺑﺴﺘﻪ را ﻧﺸﺎن ﻣﯽ دهﺪ.‬ ‫دروازﻩ‪ TCP/UDP‬ﻣﺒ ﺪا : درﮔ ﺎﻩ ﻣﺒ ﺪ ﺑ ﺴﺘﻪ ﭼﻴ ﺴﺖ و ﺁﻳ ﺎ ﻧ ﺮم اﻓ ﺰار ﮐ ﺎرﺑﺮدﯼ ﺧﺎﺻ ﯽ دﻻﻟ ﺖ ﻣ ﯽ‬ ‫ﻧﻤﺎﻳﺪ؟ اﻳﻦ اﻃﻼﻋﺎت از ﻋﻨﻮان ‪ TCP‬ﻳﺎ ‪ UDP‬ﺟﻤﻊ ﺁورﯼ ﻣﯽ ﮔﺮدد.‬ ‫ﺁدرس دروازﻩ/‪TCP‬ﻣﻘ ﺼﺪ : دروازﻩ ﻣﻘ ﺼﺪ ؟ ﭼ ﻮن ﺳﺮوﻳ ﺴﻬﺎﯼ ﻣﺘ ﺪاول ﻏﺎﻟﺒ ﺎ از دروازﻩ ه ﺎﯼ‬ ‫ﺷ ﻨﺎﺧﺖ ﺷ ﺪﻩ اﯼ از 0071‪ RFC‬اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﻧﻤﺎﻳﻨ ﺪ، از دروازﻩ ﻣﻘ ﺼﺪ ﺑ ﺮاﯼ ﻓ ﺮاهﻢ ﺁورﯼ اﻣﮑ ﺎن‬ ‫ﮐ ﺎرﺑﺮدﯼ ﺑﻌ ﻀﯽ از ﺳﺮوﻳ ﺴﻬﺎ اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﮔ ﺮدد، در ﺣﺎﻟﻴﮑ ﻪ از ﻣ ﺎﺑﻘﯽ ﺻ ﺮف ﻧﻈ ﺮ ﻣ ﯽ ﮔ ﺮدد. اﻳ ﻦ‬ ‫اﻃﻼﻋﺎت ﻧﻴﺰ از ﻋﻨﻮان ‪ TCP‬ﻳﺎ ‪ UDP‬ﺑﺴﺘﻪ ﺟﻤﻊ ﺁورﯼ ﻣﯽ ﮔﺮدد.‬ ‫ﮐ ﺪ ﺑﻴ ﺖ ‪ : TCP‬ﺁﻳ ﺎ ﺑ ﺴﺘﻪ داراﯼ ﻣﺠﻤﻮﻋ ﻪ ﺑﻴ ﺖ ‪ SYN‬ﻣ ﯽ ﺑﺎﺷ ﺪ. ﺑ ﻪ اﻳ ﻦ ﻣﻌﻨ ﺎ ﮐ ﻪ ﺑﺨ ﺸﯽ از ﺷ ﺮوع‬ ‫ارﺗﺒ ﺎط ﻣ ﯽ ﺑﺎﺷ ﺪ، ﻳ ﺎ داراﯼ ﻣﺠﻤﻮﻋ ﻪ ﺑﻴ ﺖ ‪ ACK‬ﻣ ﯽ ﺑﺎﺷ ﺪ ﮐ ﻪ ﺑﻴ ﺎﻧﮕﺮ ﺑﺨ ﺸﯽ از ارﺗﺒ ﺎﻃﯽ اﺳ ﺖ ﮐ ﻪ‬ ‫ﻗ ﺒﻼ ﺑﺮﻗ ﺮار ﺷ ﺪﻩ اﺳ ﺖ؟ از اﻳ ﻦ اﻃﻼﻋ ﺎت ﻣ ﯽ ﺗ ﻮان در اﻧﺘﺨ ﺎب اﻳﻨﮑ ﻪ ﺑ ﻪ ﺑ ﺴﺘﻪ ه ﺎ ﺑﺎﻳ ﺪ ﻣﺠ ﻮز ﻋﺒ ﻮر‬ ‫دادﻩ ﺷ ﻮد ﻳ ﺎ ﺗ ﺎﺧﻴﺮ اﺳ ﺘﻔﺎدﻩ ﻣ ﯽ ﮔ ﺮدد. اﻟﺒﺘ ﻪ، اﻳ ﻦ دادﻩ ه ﺎ در ﺑ ﺴﺘﻪ ه ﺎﯼ ‪ ، UDP‬ﮐ ﻪ ﻣﻔﻬ ﻮﻣﯽ از‬ ‫ﮐﺪﺑﻴﺖ هﺖ ﻧﺪارد، ﺣﻀﻮر ﻧﺪارﻧﺪ.‬

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‫‪Learning TCP/IP‬‬

‫‪BY: Nasser-Desperado‬‬

‫ﭘﺮوﺗﮑ ﻞ ﻣ ﻮرد اﺳ ﺘﻔﺎدﻩ : ﺁﻳ ﺎ ﺑﺎﻳ ﺪ در ﺷ ﺒﮑﻪ ﺑ ﻪ اﻳ ﻦ ﭘﺮوﺗﮑ ﻞ ﻣﺠ ﻮز ﺑﻬ ﺮﻩ ﺑ ﺮدارﯼ دادﻩ ﺷ ﻮد، ﻓﻴﻠﺘ ﺮ‬ ‫ﺑ ﺴﺘﻪ ﻧ ﺮم اﻓ ﺰارﯼ ﻣﻤﮑ ﻦ اﺳ ﺖ در ﺣ ﺎﻟﯽ ﮐ ﻪ از ﺑﮑ ﺎر رﻓ ﺘﻦ ‪ UDP‬اﺟﺘﻨ ﺎب ﻣ ﯽ ﻧﻤﺎﻳ ﺪ ﺑ ﻪ ﺑ ﺴﺘﻪ ه ﺎﯼ‬ ‫‪ TCP‬اﺟﺎزﻩ اﺳﺘﻔﺎدﻩ دهﺪ ﻳﺎ ﺑﺎﻟﻌﮑﺲ.‬ ‫ﺟﻬ ﺖ : ﺁﻳ ﺎ ﺑ ﺴﺘﻪ ﺑ ﺪاﺧﻞ دﺳ ﺘﮕﺎﻩ ﻓﻴﻠﺘ ﺮ ﺑ ﺴﺘﻪ ﻣ ﯽ اﻳ ﺪ ﻳ ﺎ از ﺁن ﺟ ﺪا ﻣ ﯽ ﺷ ﻮد ﺑ ﻪ دﺳ ﺘﮕﺎﻩ ﻓﻴﻠﺘ ﺮ ﺑ ﺴﺘﻪ ﻣ ﯽ‬ ‫ﺗﻮاﻧﺪ ﺑﺮ اﺳﺎس ﮔﺰﻳﻨﺶ، ﻓﻴﻠﺘﺮ ﻋﺒﻮرﯼ ﺑﺴﺘﻪ و ﺑﺮ ﻣﺒﻨﺎﯼ ﺟﻬﺖ ﺟﺮﻳﺎن ﺑﺴﺘﻪ ﺗﺼﻤﻴﻢ ﺑﮕﻴﺮد.‬ ‫واﺳ ﻄﻪ : ﺁﻳ ﺎاز ﺷ ﺒﮑﻪ ﻣﻄﻤ ﺌﻦ ﻳ ﺎ ﻏﻴ ﺮ ﻣﻄﻤﺌﻨ ﯽ ارﺳ ﺎل ﻣ ﯽ ﺷ ﻮد؟ دﺳ ﺘﮕﺎﻩ ﻓﻴﻠﺘ ﺮ ﺑ ﺴﺘﻪ، ﺑ ﺮ ﻣﺒﻨ ﺎﯼ‬ ‫واﺳ ﻄﻪ اﯼ ﮐ ﻪ ﺑ ﺴﺘﻪ را ﻣﻨﺘﻘ ﻞ ﻣ ﯽ ﮐﻨ ﺪ، ﻣ ﯽ ﺗﻮاﻧ ﺪ ﺑ ﺴﺘﻪ ه ﺎﻳﯽ را ارﺳ ﺎل ﻧﻤﺎﻳ ﺪ ﮐ ﻪ ﺟﻠ ﻮﯼ اﻧﺘﻘ ﺎل دادﻩ ه ﺎ‬ ‫را ﺑﮕﻴ ﺮد. ﻓﻴﻠﺘﺮه ﺎﯼ ﺑ ﺴﺘﻪ )ﻣ ﺴﻴﺮﻳﺎﺑﻬﺎ ﻳ ﺎ دﻳ ﻮارﻩ ه ﺎﯼ ﺁﺗ ﺶ( ﺑ ﺎ ﻳﮑ ﺴﺮﯼ ﻗﻮاﻋ ﺪ ﻓﻴﻠﺘ ﺮ ﮔﻴ ﺮﯼ، ﺑ ﺎ ه ﺮ‬ ‫ﺧ ﻂ در ﻣﺠﻤﻮﻋ ﻪ ﻗﻮاﻋ ﺪ ﭘﻴﮑﺮﺑﻨ ﺪﯼ ﻣ ﯽ ﺷ ﻮﻧﺪ ﮐ ﻪ ﻣ ﺸﺨﺺ ﻣ ﯽ ﻧﻤﺎﻳ ﺪ ﺁﻳ ﺎ ﻧ ﻮع دادﻩ ﺷ ﺪﻩ ﺑ ﺴﺘﻪ ﺑﺎﻳ ﺪ ﻣ ﻮرد‬ ‫ﻗﺒ ﻮل ﻗ ﺮار ﮔﻴ ﺮد ﻳ ﺎ ﺑﺎﻳ ﺪ ﺣ ﺬف ﺷ ﻮد. اﻳ ﻦ ﻗﻮاﻋ ﺪ ﻏﺎﻟﺒ ﺎ ﻟﻴ ﺴﺘﻬﺎﯼ ﮐﻨﺘ ﺮل دﺳﺘﺮﺳ ﯽ )‪ (ACLs‬ﻓﻴﻠﺘ ﺮ ﮔﻴ ﺮﯼ‬ ‫ﺑ ﺴﺘﻪ ﻧﺎﻣﻴ ﺪﻩ ﻣ ﯽ ﺷ ﻮن، ﺑﺨ ﺼﻮص وﻗﺘ ﯽ ﮐ ﻪ ﺑ ﺮ روﯼ ﻣ ﺴﻴﺮﻳﺎﺑﻬﺎ اﺟ ﺮا ﻣ ﯽ ﮔ ﺮدد. ﺷ ﺮﮐﺘﻬﺎ ﺗﻮﻟﻴ ﺪ ﮐﻨﻨ ﺪﻩ‬ ‫ﻧ ﺮم اﻓ ﺰار ه ﺮ ﮐ ﺪام از ﻳ ﮏ ﻧ ﻮع ﻓﻴﻠﺘ ﺮ ﮔﻴ ﺮﯼ ﭘ ﺸﺘﻴﺒﺎﻧﯽ ﻣ ﯽ ﻧﻤﺎﻳ ﺪ ﮐ ﻪ ﺑ ﺮاﯼ اﻳ ﻦ ﻗﻮاﻋ ﺪ، داراﯼ دﺳ ﺘﻮر‬ ‫زﺑ ﺎن ﻣﺨ ﺘﺺ ﺑﺨ ﻮد ﻣ ﯽ ﺑﺎﺷ ﻨﺪ، ﺑ ﺎ ﻳﮑ ﺴﺮﯼ ﺗﻮﻟﻴ ﺪات ﮐ ﻪ زﺑ ﺎن ﺳﻔﺎرﺷ ﯽ را ﻓﺮاهﻤﻤ ﯽ ﺁورﻧ ﺪ و ﻣ ﺎﺑﻘﯽ ﮐ ﻪ‬ ‫‪ GUI‬را ﺑ ﺮاﯼ ﺗﻌﺮﻳ ﻒ ﻗﻮاﻋ ﺪ ﻓﻴﻠﺘﺮﮔﻴ ﺮﯼ ﺑ ﺴﺘﻪ ﻓ ﺮاهﻢ ﻣ ﯽ ﺁورﻧ ﺪ. ﺑﻌ ﻀﯽ از ﻗﻮاﻋ ﺪ ﻣﺘ ﺪاول ﻓﻴﻠﺘﺮﮔﻴ ﺮﯼ‬ ‫ﺑﺴﻪ ﺑﺎ اﺳﺘﻔﺎدﻩ از زﺑﺎن ﺗﻌﺮﻳﻒ ﻗﺎﺑﻞ درﮎ ﻃﺒﻴﻌﯽ ﺷﺮﮐﺖ ﺳﺎزﻧﺪﻩ را ﺗﻮ ﺟﺪول ﻧﻮﺷﺘﻢ.‬ ‫ﮐﺪ ﺑﻴﺖ‬ ‫هﻴﭻ‬ ‫‪ACK‬‬ ‫‪All‬‬ ‫دروازﻩ ﻣﻘﺼﺪ‬ ‫08‬ ‫22

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