Routing Technology

[Christos Ricudis]

Hello Linux-greek-users!

  On 27 Jan 99, Linux-greek-users wrote to All with subject "Routing
Technology":

 L> mporei na mou pei kapoios, poies einai oi diafores ,
 L> meionektimata, pleonektimata tou RIP kai tou OSPF ?

To RIP einai ena distance vector prwtokollo. Ka8e node kanei flood se ola ta 
adjacent nodes ena "distance vector" poy dhlwnei thn "apostash" toy (ws pros 
kapoio metric) pros ka8e gnwsto s'ayton proorismo. Ka8e kombos poy lambanei 
ena distance vector apo kapoio neighbour, kanei update to routing table toy me 
thn epipros8eth plhroforia poy ma8ainei apo to distance vector, kai ksanakanei 
flood me ta dika toy distance vectors se olous toys dikous toy neighbours. H 
diadikasia epanalambanetai wspoy kanenas kombos na mhn "ma8ainei" kainouria 
xrhsimh plhroforia. Etsi telika ka8e kombos gnwrizei to kalytero ("syntomotero 
ws pros to metric") next hop gia ka8e dynato destination.

To OSPF anti8etws, einai ena link state protocol sto opoio ka8e kombos 
gnwrizei oloklhrh thn topologia toy diktyou, kanei gnwstes tis allages sthn 
topologia me flooding sta neighbours (me mia diadikasia promoia me thn 
prohgoumenh) kai ypologizei monos toy thn plhrh diadromh mexri ka8e dynato 
destination me kapoion shortest path algori8mo (o algori8mos poy 
xrhsimopoieitai sto OSPF einai o Shortest Path First - o gnwstos algori8mos 
toy Dijkstra. Eks'ou kai to onoma toy prwtokollou). 

Poies einai oi diafores? To kyrio pleonekthma toy RIP einai h aplothta sthn 
analysh kai thn efarmogh toy - o algori8mos ginetai poly eykola katanohtos kai
einai epishs poly aplos sto implementation. To kyrio toy meionekthma einai oti
pasxei apo arketa problhmata toso 8ewrhtika (count-to-infinity, single-metric/
single-path routing ktl) oso kai ofeilomena sta diafora implementations toy
RIP (limited range, adynamia ksexwristou routing se non-byte-boundary subnets 
sto RIP version 1, RIP synchronization problem, kai alla). Egine prospa8eia na 
ly8oyn arketa apo ta problhmata toy me epipleon pros8hkes kai tropopoihseis sto
basiko prwtokollo, pragma poy se kapoio shmeio perissotero dieyryne para elyse 
to problhma. To OSPF anti8etws, einai ena sygxrono kai plhres routing protocol,

me poly pio eksypno routing information dissemination sxhma apo to klassiko 
"flood routing vector every 30 seconds" sxhma toy RIP, yposthrizei sta8ero 
kai taxy loop-less routing, dynatothtes load balancing kai multi-metric 
routing, kai mporei na xrhsimopoih8ei gia thn ylopoihsh ierarxikou routing. To
kyrio meionekthma toy einai h *poly* megalyterh polyplokothta toy toso se 
epipedo ylopoihshs oso kai se epipedo managmenet.

--
Christos Ricudis
"Windows has detected that a gnat has farted near your computer. Press any
 key to reboot". - anonymous in ASR. 	
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