Open Shortest Path First (OSPF) Routing Protocol Simulation

Open Shortest Routing Deepinder Sidhu, Maryland Path First Protocol Tayang Center Fu, for (OSPF) Simulation* Shukri Abdallah and Telecommunications Department of Computer University MD Nairt & Science of Maryland Baltimore, Raj Research — BC 21228 and Institute for Advanced University Computer of Maryland College Park, Rob Studies — MD CP 20742 Coltun Consultant Abstract At each router, tinuously Open Shortest hierarchical routing First routing Election stant time, input buffers, Router(DR) three has a limited for buffers Election and the Flooding Protocols election time and causes an oscillatory *This Defense research at the vie ws and policies, Defense either not in this or implied, the in conof 4000 increases the put document behavior. County. as representing of the of Corporation, 13595 and the of- Department Dnlles buffers the of Technol- network, by for link BI)R ber of unacknowledged within RxmtInterval. works, the input a small Reducing changes the the value bootup-convergence-time at of 20, 50 and speed exceeds the ret ransmissions. from and three of 4000 is due retranstimes packets For Kbps neton the 80 router buffer at high link net- size clras- (3) bootup-convergence-time. of the RxmtInterval in nunl- received impact the in the input the increase to large size has little inThe to 6000 The flooding 80 results: (2) For 20 and 50 router buffer change fail shows three respectively. bootup-convergence-time the is bounded as link two speeds 50 Mbps conIn of overflowing causing the tically 53 the using probability is bounded DR (3) in bootup-convergence-time above work, the A simulation networks, bootup-convergence-time. VA 22071 Permission to copy without fee all or part of this material is granted provided that the copiee ara not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. SIGCOMM’93 - Ithaca, N. Y., USA 19193 ~ 1993 ACM 0-89791-61 9-01931000910053 . ..S 1.50 and Protocol, increases RxmtInterval of Govermnent. Netrix Kbps, DR HelloInterval. Flooding mission The are those the point-to-point increase Department the of instability. the DR-agreement-time (1) For the 50 router the by the OSPF Router-ID causing when by twice router between Baltimore be interpreted expressed address: Herndon, in part of Maryland contained and should or the U.S. t present ogy Dr., University conclusions the authors ficial was supported above (1) number case, the same time, of the results: can be elected a competition worst to support A simulation shows (2) If a router is a dynamic, designed networks. Protocol Designated (OSPF) protocol in TCP/IP OSPF The Path the changes lowers speeds. the 1 Introduction in the list router Open Shortest hierarchical routing ing Path First routing in TCP/IP protocol rithms: Election, Flooding ing information The The Hello, distribute within shortest-path In this it elects rout- in the algo- value and Shortest- synchronize the Election and Flooding tion 2 presents and the itself in Protocols Flooding Protocols. study of the Section of Sec- event 3 contains Election (DR) and of the discrete and Flooding Protocol distribute and among the sages within the is BDR fields each containing among that of the hello router router absence a hello packet terDeadInterval. a bidirectional order At a list a hello X from router of router Y. neighbor X when are eligible routers The are set We also in zero sec- routers was booted is booted and We assume runs tv – t$ is the in the at time at time t. tg such inter-boot-time, at time are booted At seconds, in increasing experiment is repeated for la shows the result for At lb shows the result for At = 30 and la, the increase = 7 seconds, the DR-election-time number of the lb, la, at routers network. to the in Fig. executed explanation Fig. To explain to a broadcast this In DR-election-time of events 40 increases of routers. is constant. the sequence we generalize Then, a network of n routers. At time 7 seconds, it broadcasts time detects Id does not receive seconds. of RouY router delays. Protocol tz, then router 100 routers RouterDeadIn- of each Rv was booted R1 and Rz attached X dis- router elects of input Timer, R. DR-election-time X a period 10 to processing all routers In Fig. we trace Hel- from for the first is booted is to deter- amount router with linear DR packet Router considers X the its Router-Id, Router Y for X Every a hello packet, receives router Fig. linearly A the router respectively. If router of Router-Id. Figure Elec- of Router-Ids Y when Router the using packet. wins of 7, 10, 22, 30 and 40 seconds. and routers is positive. a BDR information Y when from in transmits and covers the X other X has received Within seconds. participate and tu z of mes- information other and state. from Timer the Election and the remaining system. to Router-Priority whom packet number from of t2 – tl,on a broadcast 10 seconds At. The first to information topology a DR Router-Priority a hello the that experiment Wait Hello Initially, that Router (BDR) network. information if its nominates loInterval, its broadcast eligible Protocol and reduces autonomous router router DR to topology a broadcast topology the A tion on needed and hides Router synchronize routers network, a Designated of this The the and the next elects A null absence the winning-DR unlimited propagation DOWN Designated the first at which sizes vary buffers. zero Pro- Protocol a Backup the to the router at which have and onds. The Router-Id Time network assume Election its packet. “winning-DR’). DR-election-time, to 40, 40 and t Ocols. 2.1 inserts hello if net work, terval of the Election sent by a DR(BDR) indicates We refer objective the output the results fields as the The mine The we present simulation two Election itself. Election Simulation this section, In and and t2 be the time conclusions. OSPF packet itself of the and the BDR. all of which 2 declare field these Initial the of OSPF. results to DR(BDR) DR(BDR) the election system. computes a simulation simulation and is said Let tl be the time we present in the hello rout- autonomous algorithm DR and Flood- tree. paper, summary OSPF Election, an A router support interrelated and Shortest-Path-First to The of (SPF). Protocols [1]. a collection the Hello, ing is a dynamic, designed networks is Path-First ‘( OSPF) protocol of Router-Ids Y. and time as enters sees its Router-Id the 14 seconds, the WAIT packet from for router broadcasts state. RI is booted containing state when it router packet WAIT Similarly, the hello 54 a hello enters when Router R2 at time its up, Router- a period of 40 R2 is booted a hello RI upon packet at and receiving 14 seconds estab- lishes one-way seconds, communication the second casts a hello R2. lishes with receiving packet, both communication with munication becoming router the pires when WAIT state or a Backup-Seen A Backup Rx if R. receives Rv such that packet itself in the WAIT as DR state, from 4 g 3rm- A Timer ex- ’2001 router and declares ! .a .g themselves time pires, and 47 seconds, RI elects the Wait R2 as the Timer DR a higher Router-Id. R1 broadcasts elect ion in its packet. hello at RI ex- because R2 has the result of the A Backup ~, , Is or BDR. At S- “~- to be the BDR, declare 607080901CCI Newark Since R1 and .R2 are cannot 1020304Q50 router another itself a BDR. they ‘w 4al - com- at any to be the DR it has not elected .! a hello election. Wait is triggered a hello [.0 RI. is triggered. (1) Rv declares or (2) RV declares that if its event _Seen event router for 1 700- and bidirectional candidates ma R2 estab- R2 broadcasts establish 17 RI broadof RI packet, routers exits router hello 24 seconds, At time the Router-Ids this bidirectional .At time R2. HelloInterval, packet Upon with ~ Iriler-nca SO 60 NeNwuk at R2 is not ing itself when the Wait self as the time, triggered to be DR Timer DR and the Hello gered R2 as the seconds, network is not time BDR. At at R2 expires to run and the itself declares itself by broadcasting DR-election-time for as a BDR a hello At Finally, onds, is trig- cation time to the generalize network RI, R2,. 57 R. Thus, of two routers n routers ... Rn. The boot .,7 * n seconds at each router 40 seconds WAIT cause (1 < i < cation. When the router whom the n – 1) expires, it elects the it established period establish Wait with remains Wait Timer router Timer expires the highest bidirectional elects as the is where At = early because a gered at any Each Election in the time. First, itself as the be- event at of router casts a hello which causes i all 7 x n sec- and expires. As DR.. At time, expires, R.-l election as the and BDR. = 7 x n + 40 – 7, time increases event The communi- of R. – time same lin- cannot be trig- explanation holds 22 seconds. excluding the be triggered as the Timer a Backup_Seen Protocol run time Timer Rn DR The router. router R.-l two & additional Election which other causes one the 11~ and additional packet declaring a Neighbor.Change Second, declaring runs times. a hello routers. packet R.-l Protocol Rn broadcasts DR and itself a Neighbor-Change event R._l as the broadBDR at all other routers. communiat router 7. for At = 10 and Wait Router-Id elect at Wait the Wait – eiection i + 1 is booted, bidirectional all routers seconds, 7xn+ of 40 seconds cannot Networks bidirectional its DR are The at 47,54,61,..., Rn before itself of routers respectively. _Seen event Before routers of these Broadcast is booted the the Router-Ids Each router for the whole Backup router. and both expires respectively. state the by any time for establish Thus, consider with Rn routers with 7wz+40 whole packet. explanation, with 7,14,21,.. Timer the Time router All a result, 54 – 7 = 47 seconds. To 1: Election same R1 selects BDR. a network Figure receives event election. as the the RI 1 K1 it- and R2 broad- When 70 Sue declar- 54 seconds, R2 elects a Neighbor_Change RI DR RI R1 as the of the election. packet, causing RI At at R2 expires, Timer casts the results the hello because or BDR. Fi~ b 60 90 lTir@.e.3Q0r40Jcc 10203040 _Seen event i, Figure this with communication. time 55 lb shows scenario, At 30 seconds. a constant = 30 and Router DR-election-time. router RI Rz is booted In is booted at at time 60 seconds and enters bidirectional RI When the 70 seconds, of the routers, their expires at WAIT state triggers is triggered a and accept the upon re- routers existing lb also under shows a different seconds. The seconds when Wait timer not and the Wait it yet is has hello other packet from RI communication, triggered at R2 forcing and RI triggered elect as the RI and R2 as the order of the the it DR erwise, state of a hello recent HelloInterval (3) boot of at least t&(t~z) newly the in deter- terval seconds terval is the the have Let ing RouterDeadIll- where RouterDeadIn- before is run before ot h- of elec- of the has expired The Hello R. where i = (Router routers packet DR the the are At equal 2a-2c show which the before go- routers should exactly absence at R.’s of the router. to detect and BDR on its groups, of ten mod ex- on the Depending boot G’,, HelloInterval. the RouterDeadInter- router belong Timer depends one – Id * At) of another BDR RouterDeadInHello expiration tdh + seconds. if the when belongs in a group Let the DR at All checks only of each a router and RouterDeadInterval Timer time, All in and tbh + t erval time with time hello absence a router time a tdb). pires. t~b, Figures last < val expiration be broadcast the (td~, tb~ at At down, experiment. be broadcast the de- BDR-agreement-time experiment of this a router router. are brought and td~(t~~) objective DR(BDR)- after period BDR This down The the change. of another the the state (t~z– tbl),for a broadcast elapsed, minimum and of the at which DR(BDR). is measured absence DR boot efficient a degradation the absence time is to determine t~l state be the time detects t& – tdl time a FULL (t~l) be the aft er a t orological However, Dead- information(results will The reach let tdl or- EXCHANGE-START elected experiment RouterDeadInterval event; the in increasing at the same to the groupti time. Gd and Gb respectively. (1) the constant choose two BDR, and the intended least Wait the exactly events Hello-Timer-expiration achieve Priority with detect to performance. lb, enters impacts An these resulting and router respectively. events packet. handles after DR last DR(BDR) is them The Neighbor.Change content the most Fig. router and is event Protocol. neighbors) To and eventually and the BDR. the first the results bidi- its WAIT BDR Change are booted to 7, 10, 22, 30 and 40 seconds. event causing Topological all routers DR(BDR), measured. comreceiving establishes events t ion, new bidirectional one On by assigning to the routers. and DR-agreement-time Wait -Timer-expiration, and the and the Election implementation handles bidirectional routers RouterInterval-expiration, Backup_Seen OSPF that the DR the RI a BDR A Backup-Seen of handling performance mine with tects commu- elect router. R2 to exit DR. and has expired, not which 80 Rl a Backup.Seen at the remaining The Assume 40 = at time Since of RI established any elect expires R1 does with rectional At bidirectional Timer DR. not where of RI established as the munication the Time net work DR-election- R2 is booted. R2 have itself scenario, router nication since a constant can be generalized priorities agreement-time, Figure elects positive of this DR and BDR. time different at which state These result der of Router-Id the results the WAIT the BDR. This Election For each of the remaining from routers. elect is 40 sec- which R2 exits event packet Since it does not packet at R2. as the DR. a hello 80 DR. R1 broadcasts a hello a Backup_Seen ceiving exit in RI as the time the DR-election-time .Seen event and elects of RI itself neighbors, 70 seconds, election Backup R2 at Timer elects a B D R. Therefore, At time RI establishes with Wait RI has no bidirectional onds. state. communication seconds. time the WAIT and the the first before intended Wait Timer, routers assign highest DR Timer DR-election-time and positive Router-Ids, wait booting BDR To calculate to be the intended them two as in and for a period and (4) boot for partition the S3 where S1 is the absence (2) boot the intended wait Routerof at the DR(BDR)-agreement groups of the DR into and the Sz is the set of groups BDR, the DR before they the remaining of the 56 BDR before they BDR which detect and S3 is the set of groups a period three set of groups times, sets, which detect detect Sz and detect at the same detect the the time, the absence the absence which S1, we of of the BDR the absence absence of the 1 25 1 --, BDR C.m&kOll BDR-.-3 -------- ----------- . . . . .. . . . .. . .. -------------- . .. . .. . .. . . . . . ---i 2.0 - BDR-.-3 . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . .. . . . . . .. 1510 2 .. .. . . . . . . . . . . . . . . . . . . . . . ------------DR CMMMWU 3 t ------------- 2 DR CXudtwn 3 --------1 10 - ... . .. . .. . . . .. . .. . . i ‘t I InmPBmI1 Time F 7 aec 1070304050 DR CMAQMI F,,, . ti-Bswt I . . .. . .. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . F,,. Tlmo,= 22 SCGS, 1020304050 607080901W S12C. Nelwaz b 90 607080 New-k ICKI S- 10 t -2 ILI&,PBoot ‘lhnc , 10= 107D304O5O i.. c w muludc 6070 Nelwmk Figure 2: Election Time M901W Sur, after Topological t& DR. To determine consider which time belongs the Hello DR in which a router and BDR Rj to set a group in group Timer the Gk. Let expires down(tjh ~ t~b). Let If condition grOUp Go 1 ~ RouterDeadIntemal. simultaneously equal wise, or both to the HelloInterval, then if z is greater then or equal Gk E 5’2; otherwise, Thus, we determine Gk to the ring t~l and tbl as follows. + group modulo tbh + RouterDeadInterval Gf is the To first non-empty of integers determine 10. At tdz and is a multiple + group modulo tdh, tbh and tdb according (1) zero t~l = val, f if that Gd = Similarly, f causes elect b in tbz, we relate of the HelloInterval, the times or all in and tbz = 57 DR routers belong to = = + Fig. to BDR DR event to and with the run the enter the new DR. DR-agreement-time 2c. After one a hello the Election with tbl + Hellolntewai is 10 seconds which Protocol, the new BDR. the BDR- and as shown all groups is enter the in Fig. belong 2c. to the sets S1 elects EXCHANGE- a new state DR with and enters the new the present BDR DR. the Each to become In HelloInter- packet simultaneously state 2 holds, tdh the run and tbl Each promotes is a new S1 and Sz, and the set S3 is empty. START (2) a broadcasts routers a new If condition conditions: to elect routers state DR agreement-time 10. to one of three new Hence, & condition Neighbor_Change all elect EXCHANGE-START t~l = follows as shown d if Gb = ~ and that A case tdz = tdl @ follows tdl causes Protocol, the all and EXCHANGE-START + b if Gb # ~; otherwise, tb~ = tbh + RouterDeadInterval the ring Election HelloInterval, if Gd # @; otherwise, non-empty of integers S1; other- this td~ = tdh + RouterDeadInterval in the c or Gk <5’3. tdh+RouterDeadInte?’val+d and G~ is the first are greater Each of events holds, S1 z = ijh – Qh and g = tj~ – t~~. If z and g are both HelloInterval, < tdb and BDR. less than the tbh < tdh of the HelloInterval. a sequence and a new first Rj after the at router are brought determines state be the tjh < tbh < tdb, or (3) not a multiple Gk belongs, DR-OTHER Change router router in in Sz the new DR and detects the absence of the BDR piration of its HelloTimer. at which the new DR broadcasts T2 be the last time the absence occur to have state with any group BDR. the Election T2). Protocol tbz = T1. agreement entered times At time for 2a-2b t~l. All to the sets in the a new BDR. DR. Each the S1 and S3, the S1 elect set router After the BDR to one the DR BDR. The There- declared new second new DR and new elected and declares ~dl. Therefore, time to in Figs. than 2a-2b. Let all DR at time that min(T1, tbz = max(T1, In the the at the bounded In checks same above an the OSPF T3). Then, the case, when time, the by twice iden- the queues of RouterDeadInterval packets runs three However, for the same results the hello packets. the packets re- from and buffer. The flooding packets from arriving thus increasing As election the and size of agreement when we introduce sepa- hello and pacli- flooding queues as in Figs. before We strongly at from flooding times. packets packets la 2a. We we processed have the that a separate and should a higher to 10, we and recommend should for hello packets same are dif- results HelloInterval the of the runs priority an con- process than the the other cent rol packets. en- If T3). a router, buffer at the space, identity ceive BDR a hello R, is down. its hello of buffer may new a 58 DR has amount we observe an oscillatory at DR packet from seconds, The DR packets space. and a limited of the terDeadInterval is for and flood- incoming the tot al size of both the queue hello decreases, implementation trol HelloInterval, router is set behavior the agreement OSPF the new the exper- previous hello different input every flooding hello BDR. and the queues processed at which for and increase. input after and a the obtain BDR both of the between routers election times to have two has one input-control- different other packets ets keeping with determine DR-electionThe is full, results prevented the rate DR-agreement-time implementation, hello BDR elected DR the on the of the Pro- of all interfaces la and 2a. This competition if the time queue three each the receiv- +HelloInterval. the in Figs. at the tdz = min(T1, newly from sults After as shown state ferent packets DR-agreement last 2c. = 7 and the size of the & contains If the The hand, are guaranteed about expiration the the to the queues conducted a new other absence T4+HelloInter8al) worst On agree HelloInterval T3 be the S3 detects know BDR. elects a a new DR. the that which packets. newly one HelloInterval the EXCHANGE-START routers fail S1, it one routers BDR. change On the it- elects is to affects Each interface experiment. new DR. the itself all router we expect Therefore, DR new new be less in All and is in itself any group tered not BDR. DR and Flooding experiment are identical except queue We S3 de- declares as a new the absence are dropped. database at which does DR the ing ennew the S3, it it declares declaration, and the in packet new promoted itself time en- the routers the experiments belong and promote continue itself declaration of the newly with to ob- as in Fig. DR(BDR)-agreement-time. settings input-control-packet BDR promotes HelloInterval, first the and to 10 packets. state detect and Protocol DR a new which at the same time of this S2 is empty. with is in T4 be the groups state it is possible of Election Flooding time = 7 and N set of routers objective if the DR(BDR)- a new with DR BDR, Let DR tities the DR, and elected as a new one more the process newly elected of new self ing the HelloInterval, absence new The and in S3 elects synchronization the all EXCHANGE-START tects If then EXCHANGE-START ters BDR. 3 holds, If the RouterDeadInterval HelloInterval, and BDR expires. run imental Routers ter one group Timer tocols 22 seconds. If condition the Interaction 7’2). T1 all routers 2 when its Hello routers min(Tl, the when of checking than of the DR EXCHANGE- show condition tain in S2 detects the and elect Figures is finer and T’l and T2 must from router the granularity time packet, the new DR at time tdz = min(Tl, fore, a hello neighboring ex- T1 be the first one HelloInterval are guaranteed Then, at which of its promoted within START Let at the next may are starts behavior R. If R does the DR within R assumes not being R runs a new of input the that be down in not re- a Routhe DR except that dropped due to lack election and elects synchronization process a wit h the from new DR. Upon the old DR, again(Neighbor.Change tion. receiving 1? assumes a hello that event ) and runs R elects the old DR and starts synchronization Link packet Speed the The elec- objective the a new database with ments, for twenty seconds, a strict example arat e queue performance convergence it is crucial for hello of this impact of link unlimited networks to require- occur Wait within to impIement Timer a sep- packets. all change mechanism within an tion for that rout ers about area have exchange the most pair topology recent all of topology router the the Flooding topological time the link In this that section, measure we describe convergence-time for point-to-point bootup-convergence-time time three all routers and links up The routing-convergence-state in which all routers time at which state. that The and request a topological has reached the next sion and have lists. Let change t be occurs in is the time routing-convergence-st ate is Kbps We use three topologies: (80, 6, 5). In the notation of routers, d is the maximum router induced bias, high values have the same Kbps through degree. diameter To are chosen and minimize a topology To exercise speed 6), (50,6,4) the for chosen 4000 link the bootup-convergence-time speeds above RxmtInterval. flooding packets val. 59 When Ry, of one HelloInFig. Kbps, the in- is 50 seconds, the link In Fig. 3c, increase in by three speed increases, increases large within the speed of 6000 seconds. l?=, receives 3b, is bounded example, is bounded Rz ac- bootup- In Mbps, the 10 is not the 6000 because router time, in get For are received a router, a router, 5 and same of input-buffer-overflow links from the sum to 50 As retransmissions of 56 of respectively. of 10 seconds causing a range the for bootup- a retransmis- we of 20 (50-30) Proto- 2 Gbps. the for the link random All at speeds 3a-3b, Int erval RxmtInterval. with e. of link Figs. bootup-convergence-time probability Let – to. RxmtInterval. for the packet. communication be from an increase times topology- tl RxmtInterval, Flooding d and from e is the list advertisement and RxmtInterval giving and (IV, d, e), IV is the number network we generate interconnections, col, (20,4, twice the request convergence- seconds booted bootup-convergence-time reached. Rxmt Consequently, in the Flooding Kbps, 30 state within speeds twice In the are to by of the state a range bidirectional the link to routing- period 4000 and convergence-time crease interval for 20 terval for down the description over a link and boot up- respond be tl. The time than routers occurs. to action network. ime are If state show the bootup-convergence-time less knowledged a routing-convergence- convergence-time t until is 10 sec- a t orological reach of a link action router’ establish seconds. ate state all they is the state the FULL 50 speeds Since the are initially routing-convergence-st reach retransmission a network from the 3a-3c 10 seconds The between in a network reached. the until networks. Hello to by bringing last as the the and allowed of a database of the last convergence-t and the is the interval brought empty experiments the bootup-convergence-time The convergence-time for tocol. The the DOWN ate, and deletion is measured and Pro- are change is the Figures database have Aft er the network at time routers or the receipt the is measured, The the time in convergence-st convergence-state. new in- are is introduced Protocol learn within the topology using routers to obtains its this neighboring changes A router ex- informa- summaries by synchronizing a neighboring that topology Every system. formation ensures identical area. autonomous with which information routers buffers. and simultaneously. routing- a link. is a reliable All and output are set to 40, 40 and routers are booted change Protocol determine convergence-time respectively. convergence-time Protocol Flooding of input of each router onds reaches The is to on the RouterDeadInterval Initially, Flooding Time experiment speed amount Timer, and 2.2 Convergence and the bootup-convergence-time. process. In and the old DR is up numbers of an RxmtIntera flooding checks if this packet packet 33 Net<%, 6.6 + Bcwmpw_-w, c! BLwulp-ckmver--m, x C4rwnr---rww, 1 Nat<30,6, Rmt = Rxm, . 0 45 - 1 mum “1 I & + Booim@unvcr3-~, o B_Cam_-h . -—TI!W 40 - Rxmt = s , h, = 10 1 fuhm 3s 30 25 20’ - 1.s 15 10 5 s M Om a 600 8al F,& b i Iwo 12CK3 1400 1600 1800 20c4 3500 Link sped (Kbps) (LOW) 45 .+ Boomp&mwgum-nme, lhu,t = s o Bom.#2mvq-’lhre> F.xmt = 10 x ccuva--mnc, 1 fulme 4500 w 45 40 E :~: 33 30 10 - 2.5 s m WI= 0.s 1 1.5 Lmk sped (*) 2 (H@ 40 - .10, Buffer +Rxmt.3.RxInt. s&x XRXM, =1 OSC’-J 3sxl ?5 m 1s %.= ,0 as 1 1.5 Link sp2c.i (lap) Figure 3: Impact of Link Speed, Buffer Size and 60 2 Xlo$ RxmtInterval on 5CUI 5S00 ww (?ntcJ.mdu.) + <20.4.6 so - 0 4CJXI Lmk speed (Kllp) Sue Q&) I 1 acknowledges a packet Therefore, as the Rz increases, on Rz’s size of the the time retransmission to acknowledge RxmtInterval list. retransmission list a packet The in- objective the effect creases. In Figs. 3a-3c, RxmtInterval convergence-time A router which in this a topological OSPF change To explain the does not is bounded by 10 seconds. responds when its Hello value, Timer let time at which the Hello Timers The interval tz – tl is less than this at all routers The Fig. expire. or equal to link of The and objective the Convergence of this impact of input convergence-time. of 20, 50 and T1 (1.544 from as described 3d. not occur The This of size the size of at least 4 times 50 router 20 router the tisements must noisy behavior vertisements a buffer network, for out buffer because than maxi- 3 the buffer Open such con- Protocol in an rate-based as: (1) limit synchronizations, is poten- due to high use inherent of the retransmission a linear performance there Flooding may the number or (2) reduce timer. search Summary and must buffer the t he It is also recom- of the retransmission Conclusions be flooded protocol In this paper, at a buffer Election after time. This buffers, size for the network the 50 router of link-state is large. for Protocol ignated increase occur demonstrates is needed (OSPF) routing link-state the number First erarchical has a higher than Path networks. 50 router more Shortest at a buffer This which network size of 20 or more more can be re- to the otherwise, The memory. that 10 be avoided. the acknowledgment. network send 80 router that and at a higher than per output The network and its occurs 20 router and work. with networks, retransmissions the loss of a packet degree than is vital for mechanisms list timer degradation control from in [1] that networks. Protocol; implementation for speed is observed is reduced retransmission speed all is larger at the link suggestion performance mended an the in an input increases size of 7 in the network of of the aneous shown for reduction timer verifies OSPF value are retransmission of 14 seconds management of simult to on bootup-convergence-time. 50 router because for Output packet. size of 6 in the two does bound is greater requires impact retransmission lower operation routers bootup-convergence-time from the the a router 20 and size has little 20 router tial in or equal result of the Flooding is shown convergence that for of 20 or more size of a flooding results are size is less than implies buffer memory For procedure experiment Consequently, mum Buffer at size is varied experimental this result network three. is fixed the a speedup for high Mbps. of the For example, retransmission setting duced tention if the buffer input buffer buffer For any of the networks, three. The 20. the bootup- for networks speed the to 3. This determine the experiment, the link when above. of the OSPF size and the input results Fig. is to on In this 4 through The experiment buffer 80 routers, Mbps) Time In network bootup-convergence-time speeds. of 100 Mbps, Size 200 value However, link 50 router experiment the the speeds. 25 to this Reducing lowers link 10 seconds. from the The above. size is unlimited. results timer the is to demonstrate is as described we used buffer 3e. higher Buffer Time of the RxmtInterval. procedure speeds and input be the experiment of a low setting experiment, with to expires. t,2 < tl, Convergence of this experimental the implementation bounding HelloInterval, affect and at Router(DR) Des- in constant number of input between the Elec- increases the elec- tion time an oscillatory net- lems, very control and fail Hello bounded A the Router-ID and worst the same above simulation must To processed by twice of the the the these DR prob- in a separate at a higher the At continuously solve be queued case, when time, behavior. of the DR instability. packets queue at causes causing (3) In the 61 elected OSPF Protocols changes networks be (1) The for buffers each router, 80 routers. can results: has a limited a competition the TC!P /IP of the and the Flooding router Clearly, three hi- tion adver- ad- to support a simulation shows (2) If a router is a dynamic, and priority, the BDR DR-agreement-time HelloInterval. OSPF Flooding Protocol is using 20, works shows 50 network, and 80 three as link probability y creases of router results: speed by val for link 50 Mbps two the input flooding For packets 20 and convergence-time. change the For in value of the buffers in- the received impact the and above within on the 80 router Rxmtthe bootup- network, size a drastically (3) Reducing lowers link of unac- networks, buffer RxmtInterval at high is in the bootup- 50 router input in RxmtInter- number the bootup-convergence-time. convergence-time the increase the increase to large size has little change Kbps, retransmissions times The is due (2) buffer small three respectively. knowledged The net50 router of 4000 to 6000 Kbps convergence-time Interval. input from and speeds the 4000 retransmissions. bootup-convergence-time bounded For exceeds overflowing causing point-to-point (1) the bootup- first (OSPF) speeds. References [1] J. Moy. The specification. Network [2] Deepinder open shortest Technical Information Sidhu, Raj Nair, first simulation. and Center, Tayang Rob path Report Coltun. under RFC- 1131, October Fu, Shukri Open SRI 1989. Abdallah, shortest path preparation. 62