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Klaset e ip adresave

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Klaset e IP adresave paraqesin nje arkitekture per adresim te rrjeteve,e cila perdoret qe nga viti 1981.Kjo metode e ndan hapesiren e adresave te Internet Protocol(IPv4) ne pese klase.Secila klase,e koduar ne 4 bitat e pare,dallon ne numrin e perdoruesve ne rrjete.Klasa E eshte e rezervuar per qellime eksperimentale. Qe nga largimi prej perdorimit,klaset vazhdojne te perdoren ne konfigurimin e disa pajisjeve ne hapesira te vogela

Historik

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Nje 32-bit IPv4 adrese ndahej logjikisht varesisht prej rrjetes,e cila identifikonte ne menyre te veçante perdoruesit e rrjetes.Ky format ishte i mjaftueshem vetem atehere kur ekzistonin disa rrjeta relativisht te medha,sikur ARPANET,e cila kishte numrin e rrjete 10,dhe para ngritjes se rrjetave lokale(LAN).Si pasoje e kesaj arkitekture,hapesira e adresave pranontwe vetem 254(2^8-2) rrjeta te pavarura.Qe ne fillim u verejt se kjo nuk do te ishte e mjaftueshme.

Inkuadrimi i klaseve

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Expansion of the network had to ensure compatibility with the existing address space and the Internet Protocol (IP) packet structure, and avoid the renumbering of the existing networks. The solution was to expand the definition of the network number field to include more bits, allowing more networks to be designated, each potentially having fewer hosts. Since all existing network numbers at the time were smaller than 64, they had only used the 6 least-significant bits of the network number field. Thus it was possible to use the most-significant bits of an address to introduce a set of address classes while preserving the existing network numbers in the first of these classes.

The new addressing architecture was introduced by RFC 791 in 1981 as a part of the specification of the Internet Protocol.[2] It divided the address space into primarily three address formats, henceforth called address classes, and left a fourth range reserved to be defined later.

The first class, designated as Class A, contained all addresses in which the most significant bit is zero. The network number for this class is given by the next 7 bits, therefore accommodating 128 networks in total, including the zero network, and including the existing IP networks already allocated. A Class B network was a network in which all addresses had the two most-significant bits set to 1 and 0. For these networks, the network address was given by the next 14 bits of the address, thus leaving 16 bits for numbering host on the network for a total of 65536 addresses per network. Class C was defined with the 3 high-order bits set to 1, 1, and 0, and designating the next 21 bits to number the networks, leaving each network with 256 local addresses.

The leading bit sequence 111 designated an "escape to extended addressing mode",[2] and was later subdivided as Class D (1110) for multicast addressing,[3] while leaving as reserved for future use the 1111 block designated as Class E.

This addressing scheme is illustrated in the following table:

Rritja eksponenciale e rrjetave duhet te ishte kompatibile me numrin ekzistues te adresave dhe Internet Protocol packet structure,dhe te shmangte rinumerimin e rrjetave ekzistuese.Zgjidhja doli te ishte rritja e numrit te bitave qe percaktonin rrjeten.Kjo mundesoi me shume hapesire per dizajnimin e rrjetave,mirepo duke zvogeluar numrin e perdoruesve per rrjete,problem i cili me vone u zgjidh me ane te subnet-imit.

Arkitektura e re oer adresim ishte bere publike nga RFC 791,ne vitin 1981 si pjese e nje specifikimi te Internet Protokollit.Ky specifikim e ndau hapesiren e adresave ne tri formate,te cilat me pas u quajten Klase te adresave,dhe mbeti nje e katert per tu definuar me vone.

Klasa e pare,e njohur si klasa A,permbante te gjitha adresat ku biti me peshen me te madhe ishte 0.Numri i rrjetes per kete klase fitohet nga 7 bitat e ardhshem,meqe rast mund te fitohet gjithsej 128 rrjeta,duket perfshire zero rrjeten dhe rrjetat e krijuara me pare.Nje rrjet i klases B,dy bitat me peshe me te madhe i kishte 1 dhe 0.Per rrjetet e klases B,numri i rrjetes fitohet nga 14 bitat e ardhshem,meqe rast mbesi 16 bita per numrin e perdoruesve te rrjetes,qe jane 65536.Klasa C eshte definuar me 3 bita me peshe me te madhe 1,1,0,ku mbesin edhe 21 bita per numrin e rrjetes,dhe 256 perdorues per rrjet.

Klasa e cila permban rrjetat me bitat me peshe me te madhe 111 ishte dizajnuar si "ikje ne modin e adresimit te zgjatur",dhe me pas u nda ne dy klasa:D dhe E.

Kjo skeme e adresimit eshte dhene ne tabelen e meposhtme:

Klasa Bitat me peshe me te madhe Madhesia e numrit te rrjetes Madhesia e pjeses se mbetur Numri i rrjetave Numri i adresave Adresat totale Adresa fillestare
Klasa A 0 8 24 128 (27) 16,777,216 (2^24) 2,147,483,648 (2^31) 0.0.0.0 127.255.255.255
Klasa B 10 16 Shembull 16 16,384 (2^14) 65,536 (2^16) 1,073,741,824 (230) 128.0.0.0
Klasa C 110 24 Shembull 8 2,097,152 (2^21) 256 (2^8) 536,870,912 (229) 192.0.0.0
Klasa D 1110 pa definuar pa definuar pa definuar pa definuar pa definuar 268,435,456 (228) 224.0.0.0
Klasa E 1111 pa definuar pa definuar pa definuar pa definuar pa definuar 268,435,456 (228) 224.0.0.0

Numri i adresave te perdorshme per perdorues eshte 2^N-2 se adresat me te gjitha 0 dhe te gjitha 1 kane kuptim te veçante(network id dhe broadcast id respektivisht). Sot te gjitha Ip adresat jane te lidhura me subnet mask.Kjo nuk ishte e nevojshme ne definimin e klaseve pasi qe subnet maska mund te nxirret rrjedhimisht prej klases.

Prezentimi bit-wise

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Ne vijim shpjegohet kuptimi i :

  • n tregon bitin e perdorur per id-n e rrjetit.
  • H tregon bitin e perdorur per id-n e hostit.
  • X tregon bitin pa ndonje kuptim te veçante.

Klasa A 

 0.  0.  0.  0 = 00000000.00000000.00000000.00000000

127.255.255.255 = 01111111.11111111.11111111.11111111 

                 0nnnnnnn.HHHHHHHH.HHHHHHHH.HHHHHHHH

Klasa B 128. 0. 0. 0 = 10000000.00000000.00000000.00000000 191.255.255.255 = 10111111.11111111.11111111.11111111 

                 10nnnnnn.nnnnnnnn.HHHHHHHH.HHHHHHHH

Klasa C 192. 0. 0. 0 = 11000000.00000000.00000000.00000000 223.255.255.255 = 11011111.11111111.11111111.11111111 

                 110nnnnn.nnnnnnnn.nnnnnnnn.HHHHHHHH

Klasa D 224. 0. 0. 0 = 11100000.00000000.00000000.00000000 239.255.255.255 = 11101111.11111111.11111111.11111111 

                 1110XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX

Klasa E 240. 0. 0. 0 = 11110000.00000000.00000000.00000000 255.255.255.255 = 11111111.11111111.11111111.11111111 

                 1111XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX

Zëvendesimi i klasave

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The first architecture change extended the addressing capability in the Internet, but did not prevent IP address exhaustion. The problem was that many sites needed larger address blocks than a Class C network provided, and therefore they received a Class B block, which was in most cases much larger than required. In the rapid growth of the Internet, the pool of unassigned Class B addresses (214, or about 16,000) was rapidly being depleted. Classful networking was replaced by Classless Inter-Domain Routing (CIDR), starting in 1993 with the specification of RFC 1518 and RFC 1519, to attempt to solve this problem.

Before the introduction of address classes, the only address blocks available were what later became known as Class A networks.[4] As a result, some organizations involved in the early development of the Internet received address space allocations far larger than they would ever need.

Nderrimi i pare ne arkitekturen e klaseve e rriti hapesiren e adresave,mirepo nuk mundi te parandaloj harxhimin e ip adresave.Problemi qendronte te web faqet qe kishin nevoje per me shume adresa se sa qe ofronte klasa C,mirepo nuk mund t'i shfrytezonin ne teresi adresat qe i ofronte klasa B.Klasat e adresave u zevendsuan me Classless Inter-Domain Routing (CIDR) qe prej vitit 1993.

Para paraqitjes se klaseve,i vetmi bllok i adresave ishte ai qe me pas u be i njohur si Klasa A.Si rezultat i kesaj disa organizata qe kontribuan ne zhvillimin e Internet Protokollit moren nje hapesire te adresave shume me te madhe se qe ju nevojitej.

Referimet

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[1] Postel, J., ed. (January 1980). "Internet Header Format". DoD standard Internet Protocol. IETF. sec. 3.1. RFC 760. Retrieved November 8, 2013. [2] James Kurose,Kith Ross. "Computer Networking:Top-Down Approach Featuring the Internet, 4thEdition ". June 21, 2007.

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