Routing Technology

[Manolis Sifalakis]

Hlias Saxpazidis wrote:
> 
> Geia sas,
> 
> mporei na mou pei kapoios, poies einai oi diafores , meionektimata,
> pleonektimata tou RIP kai tou OSPF ? ( Se genikes grammes ).
> 
> Euxaristo.
> 

Loipon exoume kai leme ...

RIP.
----
 - Einai isws to prwto IGP protokollo, ftaxtikai apo tin Xerox gia XNS, kai egine
port sto TCP/IP apo to Berkeley
 - Einai "distanve vector" protokolo. Ayto epi tis ousias simainei oti i antalagh 
routing pliroforias metaxy routing peers, sunodeuetai apo antalagh tvn routing tables
(eggrafes tis morfis: <network route> --> <metric>). 
 - Ex' aitias toy parapanw algorithmou pou xrisimopoiei, kathws kai tis poly 
aplopoiimenhs ylopoihshs exei ena swro problimata otan to xrisimopoiiseis se 
polyplokes topologies, opou ena route mporei na matheutei apo pola shmeia (blepe
"split horizon", kai "poison reverse").
 - H version 1 tou RIP, pou einai kai h pio xrisimopoihmeni, logo palaiothtas, den 
katalabainei apo Variable subnet masks. H vesion 2 omws diorthwnei kapws ta pragmata 
ston tomea auto.
 - To metric tou RIP anaferetai apokleistika sto hop-count, kai den lambanei ypoyin
to cost (poiothta twn grammwn). Ayto exei san apotelesma mia diadromi pros ena diktyo
proorismou pou pernaei apo mia syndesi 9600, na thewreitai protimoteri apo mia 
diadromi pros ton idio proorismo pou pernaei apo 2 grammes tvn 10 Mbit.
 - Ena diktyo pou brisketai panw apo 15 hops makria, thewreitai unreachable.
 - Dimiourgei arketo traffic sto diktyo sou kathoti ta advertisements ginontai kathe
30'', kai synideuontai apo pliri antalagi routing pliroforias.
 - Einai poly eukolo sto settarisma, ektos an theleis na to xrisimopoiiseis se 
polyplokes topologies opou gia na apofygeis ta problimata prepei na gemiseis ton 
kosmo filtra.
 - einai poly eukolo sto implementation tou kai to briskeis pantou (akoma kai sta NT)
 - einai idaniko gia polu apla kai mikra diktya.
 - ta perissotera *NIX systimata to apokaloun "routed"

OSPF.
-----
 - Ftiaxtikai apo to IETF apokleistika gia TCP/IP, kai einai to bary pyroboliko 
sto Interior routing.
 - Einai "link-state" protokollo to opoio xontrika simainei oti sta advertisements 
den antalasei routing tables, alla apla kathe router anakoinwnei se olous tous 
symetexontes sto routing domain, thn katastash sthn opoia briskontai ta links sta 
opoia syndeetai. Me ayto ton tropo kathe router sto OSPF domain exei topologikh
apoyi toy diktyou, kai apo kei e3agei pliroforia gia na paragei to routing table tou
me ton algorithmo SPF (Djikstra nomizw).
 - Otan antalasei gia proti fora pliroforia me tous peers, anakoinwni tin katastasi 
olwn tvn links pou exei panw tou, kai meta periodika, stelnei mikra paketa LSAs gia
na diapistwsei tin katastasi sta link. Ta updates pou stelnei einai differential se
sxesi me ta proigoumena, kai stelnontai mono se periptwsi pou kati allaxi stin 
topologia tou diktyou. Gia to logo ayto "trwei" ligotero bandwidth.
 - Epeidi exei topologiki apoyi toy dikyou, den yparxei periptwsi (sxedon) pote na 
prokiyoun routing loops, kai diafora alla provlimata pou blepei kaneis me ta 
distance-vector prvtokolla (genika den tha se apogoiteusei pote !) .
 - Trwei polla resources tis mixanis logw tou computation pou xreiazetai gia na 
trexei o SPF algorithmos kathe fora pou anathewrei to routing table. Gi ayto an etrexe se NT poly apla to PC tha itan monimvs kollimeno. Sta *NIX
yparxei mesv toy
gated nomizw, kai apo oti exw akousei sto linux pigainei mia xara !
 - Den xrisimopei metrics alla costs ta opoia lambanoun ypoyin ti poiothta tis
grammis, kai gi ayto den tha deis pote tipota koufes epiloges.
 - H logikh toy basizetai stin ligiki domisi toy routing domain se areas.
 - Yposthrizei VLSMS, kai CIDR.
 - Yposthrixei Multipath selection.
 - Den exei periorismous se hop-counts kai tetoia kai gi ayto mporei na 
xrisimopoiithei se polu megala diktya, akoma kai gia Exterior routing.
 - To configuration toy einai apo yilodyskolo (an den exeis empedwsei thn filosofia 
toy, ews efialths (otan exeis na kaneis me sundiasmo toy me alla IGP kai perierga 
senaria, policy routing, klp). Einai polu eukolo na kaneis lathos kai synithws to 
plirwneis akriba. Parola ayta an to sxediaseis apo thn arxi swsta kai oxi sto podi,
opws mporeis na kaneis me to RIP, tha ekplageis apo ta apotelesmata.

 Ayta se genikes grammes den mou katebainei tipota allo, elpizw na boithisa !!!
An theleis na asxolitheis pio sobara pera apo apli pliroforisi, tha sou proteina
na diavaseis to "Managing IP Networks with CISCO routers" toy S.M.Ballew (ekdoseis
O'reilly). Den einai oti pio plires yparxei gia IGP routing, (oute kai gia EGP)
alla gia arxi einai polu kalo, periektiko, kai apolyta katanohto. To oti epikentrwnei 
sta cisco, min se enoxlei, ta idia isxyoun sxedon pantou !!!

Filika 
Manolis
 (.WILLY)

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 +--------------------------------------------------------+
 |               Sifalakis Manolis  (WILLY)               | 
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