3 OSI & TCP/IP Model
OSI model
OSI (open system interconnection) model ko international standardization organization ke liye banaya gaya tha. Jo internationaly network devices ka dekh rekh rakhti thi. Ye model ka kaa main kaam ye hota tha ke jitne bhi network devices banane wali company hai un sab ke device achhe se baki sare diveces ke sath kaam kare. N ke monopoly banake sirf apne model ke devices me ache se kaam kare aur bake comapy ke side karde. Aur security sefty ko bhi dhayn me rakhti thi.
OSI Model 7 layer me kaam karta hai. Koi bhi file in saato layer se one by one pass ho ker aage ke device tak jaati hai. Aur samne bhi yahi 7 layer hote hai.
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In saato layer ko padhne me uper se padhte hai per data kaise jaa raha hai aur aage kis kis process se ho ker gujrata use samthne ke liye physical layer se samthte hai.
In layer ka use kya hai?
Ab ye ek baat to aap samjh gaye ke alag company ke device achhe se kaam kar sake. Ab samjhte hai layer by layer data computer se dusre computer me kaise jata hai!
· Physical - Is layer ka kaam ek device ke duste tak bits ( 0 1 0 0 1 1 0) le jata hai. Jisme cable ka use hota hai. Aur mother bord se file ko bits me network interface card hi ye kaam karte hai. Aur cable ke dusre end per bhi yahi card ise wapas file ki sakal me bana deta hai.
· Data link - ye ke packet(small part of file) ko ek frame me encapsulate karta hai. Ek frame me ek header aur ek tailor hota hai. Jo devices ke connection to susseccfull banata hai. Header me aap tailor par device ka MAC hota hai. Aur tailor me index no. Take kabhi koi packet miss hoto to pata chal sake. Ab is layer me bhi sub layer hote hai.
· Logical Link Control - iska use flow control aur error detection ke liye hota hai.
· Media Access Control - iska use hardware address aur access process ko control kerne ke liye kiya jata hai.
· Network - ye devices ka address, routing aur path fix karta hai. Device(logical) address ka use network par host ki pehchan karne ke liye IP adress ka use kiya jata hai.
· Transport - Yah layer upri layer protocol se aane wale data ke bade hisse ko parts me divide karti hai. Do computer ke bich connection stablish karti hai. Aur end bhi karta hai. Flow control karta hai aur data miss hone per recover bhi karta hai.
· Session - ye do system ke bich ek pul jaise bana deta hai. Aur kaam pura hone per khatam kar deta hai. Aur record rakh leta hai ke is baar kya kaam hua. Aur har baar nayi session id banata hai.
· Presentation - ye data format ko translate ya transform karta hai. Isme compression aur encryption jaise kaam hote hai.
· Application - ye layer user ke sabse karib hai. User apna sara kaam isi layer per karte hai. Jaise browser chalana. Mail karna voice call sare kaam.
