X.25 yog cov txheej txheem txheej txheem ntawm cov txheej txheem siv rau pob ntawv hloov pauv kev sib txuas lus thoob plaws cheeb tsam network - WAN. Cov txheej txheem yog ib qho kev pom zoo raws li cov txheej txheem thiab cov cai. Ob lub cuab yeej ua raws tib txoj cai tuaj yeem nkag siab ib leeg thiab sib pauv cov ntaub ntawv.
History of X.25
X.25 tau tsim nyob rau xyoo 1970 los nqa lub suab ntawm cov xov tooj sib txuas - xov tooj sib txuas - thiab yog ib qho ntawm cov kev pabcuam qub tshaj plaws. Cov ntawv thov ntawm X.25 suav nrog kev siv lub tshuab qhia tsis siv neeg thiab cov credit card pov thawj tes hauj lwm. X.25 kuj tau txhawb nqa ntau yam ntawm mainframe davhlau ya nyob twg thiab cov ntawv thov neeg rau zaub mov. Xyoo 1980s yog qhov tseem ceeb ntawm X.25 thev naus laus zis thaum nws tau siv los ntawm pej xeem cov ntaub ntawv network Compuserve, Tymnet, Telenet, thiab lwm yam. Nyob rau thaum ntxov 90s, ntau X.25 tes hauj lwm tau hloov los ntawm Frame Relay nyob rau hauv Teb Chaws Asmeskas Qee cov laus pej xeem network sab nraum Teb Chaws Asmeskas tseem siv X.25 mus txog rau tam sim no. Feem ntau cov tes hauj lwm uas ib zaug xav tau X.25 tam sim no siv cov txheej txheem Internet tsis tshua muaj. X-25 tseem siv tau hauv qee lub tshuab ATM thiab credit card pov thawj network.
X.25 Structure
Txhua X.25 pob ntawv muaj txog 128 bytes ntawm cov ntaub ntawv. X.25 network tuav cov pob khoom sib dhos ntawm cov khoom siv, kev xa khoom, thiab kev sib dhos ntawm qhov chaw. X.25 pob ntawv xa khoom siv thev naus laus zis suav nrog tsis yog hloov pauv thiab txheej txheej txheej txheem kev sib txuas nkaus xwb tab sis kuj tseem raug kuaj xyuas thiab rov xa cov logic yuav tsum muaj kev xa khoom tsis tiav. X.25 txhawb ntau qhov kev sib tham ib txhij los ntawm multiplexing packets thiab siv cov kev sib txuas lus virtual.
X.25 muaj peb txheej txheej txheej txheem:
- Lub cev txheej
- Data link txheej
- Packet txheej
X.25 ua ntej hnub tim OSI Reference Model, tab sis cov txheej txheem X.25 yog qhov zoo sib xws rau txheej txheej ntawm lub cev, cov ntaub ntawv txuas txheej thiab txheej txheej txheej txheem ntawm OSI qauv.
Nrog kev lees paub thoob plaws Is Taws Nem raws tu qauv (IP) raws li tus qauv rau kev koom tes hauv tuam txhab, X.25 daim ntawv thov tau tsiv mus rau cov kev daws teeb meem pheej yig dua siv IP raws li cov txheej txheem network txheej txheem thiab hloov cov txheej qis ntawm X.25 nrog Ethernet lossis nrog tshiab ATM hardware.
