YHDLC vs PPP
Ob leeg HDLC thiab PPP yog cov ntaub ntawv txuas txheej txheej txheem. HDLC (High-Level Data Link Control) yog ib qho kev sib txuas lus raws tu qauv siv ntawm cov ntaub ntawv txuas txheej ntawm lub computer network, tsim los ntawm ISO (International Organization for Standardization), thiab tau tsim tawm ntawm IBM's SDLC (Synchronous Data Link Control). PPP yog cov ntaub ntawv txuas txheej txheej raws li HDLC thiab zoo ib yam li HDLC. Ob qho tib si yog WAN (Wide Area Network) raws tu qauv thiab ua haujlwm zoo los txuas cov kab-to-point leased kab.
HDLC yog dab tsi?
HDLC tuaj rau hauv lub neej tsuas yog thaum IBM xa SDLC rau ntau pawg tswj hwm tus qauv thiab ib qho ntawm lawv (ISO) hloov SDLC thiab tsim HDLC raws tu qauv. HDLC yog suav tias yog ib qho superset tshaj ntawm SDLC. Nws yog me ntsis-oriented synchronous raws tu qauv. HDLC txhawb synchronous, puv-duplex ua haujlwm. HDLC muaj kev xaiv rau 32-ntsis checksum thiab HDLC txhawb nqa Point-to-point thiab Multipoint configurations. HDLC txheeb xyuas hom "primary" node, uas tswj lwm qhov chaw nres tsheb uas hu ua "secondary" nodes. Tsuas yog lub hauv paus ntawm qhov yuav tswj tau qhov thib ob ntawm cov nodes. HDLC txhawb peb hom kev hloov pauv thiab lawv yog raws li hauv qab no. Ua ntej ib qho yog Hom Lus Teb Ib txwm (NRM) nyob rau hauv qhov chaw thib ob tsis tuaj yeem sib txuas lus nrog thawj zaug kom txog thaum thawj zaug tau tso cai. Qhov thib ob, Asynchronous Response Mode (ARM) tso cai rau cov nodes thib ob los tham yam tsis muaj kev tso cai thawj zaug. Thaum kawg, nws muaj Asynchronous Balanced Mode (ABM), uas qhia txog kev sib koom ua ke, thiab txhua qhov kev sib txuas lus ABM tshwm sim ntawm cov nodes nkaus xwb.
PPP yog dab tsi?
Raws li tau hais los saum no, PPP yog cov ntaub ntawv txuas txheej txheej raws li HDLC, thiab zoo ib yam li HDLC. Nws yog siv rau kev sib txuas lus ncaj qha ntawm ob lub nodes. Kev sib kis encryption tsis pub leej twg paub, lees paub thiab compression yog muab los ntawm PPP. Kev lees paub yog muab los ntawm PAP (Password Authentication Protocol) thiab feem ntau yog los ntawm CHAP (Challenge Handshake Protocol) raws tu qauv. Nws yog siv rau ntau hom kev tes hauj lwm uas yog tsim los ntawm ntau lub cev nruab nrab xws li lub cev kab, fiber ntau optics, serial cable, xov tooj ntawm tes thiab xov tooj. Nws yog qhov nrov heev ntawm ISPs (Internet Service Providers) ua qhov nruab nrab rau kev muab cov neeg siv khoom siv kev nkag mus rau hauv Is Taws Nem. Txhawm rau muab cov kev pabcuam DSL (Digital Subscriber Line) rau lawv cov neeg siv khoom, cov chaw muab kev pabcuam siv Point-to-Point Protocol hla Ethernet (POPoE) thiab Point-to-Point Protocol dhau ATM (POPoA), uas yog ob daim ntawv encapsulated ntawm PPP. PPP yog siv rau ob qho tib si synchronous thiab asynchronous circuits. Nws ua haujlwm nrog cov txheej txheem sib txawv xws li IP (Internet Protocol), IPX (Internetwork Packet Exchange), NBF thiab AppleTalk. Broadband txuas kuj tseem siv PPP. Txawm hais tias PPP tau tsim me ntsis tom qab thawj HDLC specifications, PPP suav nrog ntau yam ntxiv uas tau muaj nyob rau hauv cov ntaub ntawv sib txuas cov txheej txheem ntawm lub sijhawm ntawd.
Txawm hais tias, HDLC thiab PPP yog qhov zoo sib xws WAN cov ntaub ntawv txuas txheej txheej txheej txheem siv rau kev sib txuas lus taw tes rau-taw tes, lawv muaj qhov sib txawv. Tsis zoo li HDLC, PPP tsis yog tus tswv thaum siv hauv Cisco router. Ntau cov txheej txheem ua haujlwm ua haujlwm ntawm PPP. PPP yog qhov muaj txiaj ntsig zoo nrog kev sib tham hauv xov tooj thiab siv ntau heev los ntawm ISPs los muab Internet rau lawv cov neeg siv khoom. Tsis zoo li HDLC, PPP tuaj yeem siv nrog ob qho tib si synchronous thiab asynchronous sib txuas.
