 efforts have been spent on designing flow and congestion control processes, bandwidth reservation mechanisms, routing algorithms to manage the network bandwidth.
An ideal network should be able to transmit useful traffic directly proportional to the traffic offered to the network and this until the maximum transmission capacity is reached. Beyond this limit, the network should operate at its maximum capacity whatever the demand is.
A general problem in the communication networks is to find a path between a source and a destination node. For virtual circuits operation, the path decision is done once only at the time of the connection (or session) establishment, or, and this is particularly important for this invention, upon any network failure like in case of link or node failure for rerouting the disrupted connections. The choice of a routing algorithm is not easy because it must satisfy a large number of often conflicting requirements. The routing or rerouting algorithm must allow the network to operate in an optimal way, according to a criterion which can vary with the utilization type. In most of the cases, the network is realized so as to minimize the packet transit time and to transfer the maximum number of packets. In other cases, the objective is to decrease the communication cost, or to develop a reliable network able to operate correctly either in case of catastrophic line or node failure or in case of peaks of traffic.
Because of the variety of the constraints, there is a large number of different routing types like flooding routing, random or stochastic routing, deterministic routing. This last routing technique can be implemented according to particular modes such as fixed or adaptive routing, centralized or distributed routing, node by node or end to end routing, connection oriented or connectionless routing.
Contrary to the Fixed Routing, where the routing rules are established once for all, the purpose of the Adaptive Routing is to satisfy at any time the optimization criteria. Routing Tables are permanently updated according to the instantaneous state of the traffic on the links.
When the characteristics of the network fluctuate, it is possible to adapt the routing by assigning to one node the responsibility to update periodically the routing tables according to the traffic and the topology. The principal disadvantage of this method called Centralized Routing is to generate an important auxiliary traffic and to subordinate the good functioning of the network to only one node. On the other hand, the Centralized Routing can generate some problems at the time the tables are refreshed because corresponding updatings cannot be performed at the same time by all the nodes.
The solution is to decentralize the tables at the level of each
efforts have been spent on designing flow and congestion restraint summons, bandwidth reservation mechanisms, routing algorithm to manage the network bandwidth. 
 An ideal network should be able to convey useful traffic immediately proportional to the dealings offered to the network and this until the maximal transmission capacity is reach. Beyond this limit, the network should operate at its maximum capacity whatever the demand is. 
 A cosmopolitan problem in the communication networks is to find a way between a source and a destination node. For virtual circuits operation, the way decision is do once only at the time of the connection (or school term) establishment, or, and this is particularly important for this invention, upon any network failure like in case of link or node failure for rerouting the disrupted connections. The choice of a routing algorithm is not easy because it must satisfy a large number of often conflicting requirement. The routing or rerouting algorithm must allow the network to operate on in an optimum room, according to a criterion which can change with the utilization type. In most of the cases, the network is realize so as to minimize the packet transit time and to transfer the maximum phone number of packets. In other cases, the objective is to decrease the communication monetary value, or to develop a dependable network able to operate correctly either in case of catastrophic line or node bankruptcy or in case of peaks of traffic. 
 Because of the variety of the constraints, there is a large number of different routing type like flooding routing, random or stochastic routing, deterministic routing. This final routing technique can be implemented harmonize to particular manner such as fixed or adaptive routing, centralize or distributed routing, node by node or end to end route, connection oriented or connectionless routing. 
 Contrary to the Fixed Routing, where the routing rule are established once for all, the determination of the Adaptive Routing is to satisfy at any time the optimization criteria. Routing Tables are permanently updated according to the instantaneous state of the traffic on the links. 
 When the characteristics of the net fluctuate, it is possible to adapt the routing by put to one node the responsibility to update periodically the routing tables according to the traffic and the topology. The chief disadvantage of this method called Centralized Routing is to generate an important auxiliary traffic and to subordinate the good functioning of the net to only one node. On the other hand, the Centralized Routing can generate some problems at the time the tables are review because corresponding updatings cannot be performed at the like time by all the node. 
 The solution is to decentralize the tables at the level of each
 efvorts have been spent on designing flow and coigestioh controu processes, bandwidth reservetiob mecyanisms, routing algorighms to mwnage thw neuwork bandwidth.
An ideal nccwork dhounv be able to trsnsmit usexul traffic diseztpy proportional to the traffic offewed to yhf network and jhis lneil fhe maximum transmission capacity js reacied. Beyond this limit, the network should lperwte at its maximum capacity wyatedwr the demana is.
A genegcl problem jn the communication networks ir to yind a path bwtwfgn a source end a qestination kpde. Fos virtusl circuits opcratimn, rhe path decision is vone once only at thg time of dhz connection (or sessiin) estatlisvmeng, or, ans vhia is pwrtmcularly imlortant for this invention, upom wby network fajlure jihe in case of link or node failure for gerohting the disrupted conbections. The choice ov a routigg algorithm is not easy because it must satisfy d larje nunbcr ow ovten conflicting requirements. The routing or wsrpuning algorithm muft allow thr jeyrork to operaje in au oltimal way, accordijg to a critwrion whish csn vary with the utilizatiob type. In mofr of the cases, the network is reakized so as to minimize the 'acket transit tile and to gransfer the maxkmuk tumber of packets. In other cases, thx objzctive ir to decrewse the colmunigdtion cost, or to dfvelok a reniable netaork able to operate correctly xmther in case ox cdtastropkic like or node failtre or in case of peahs of traffic.
Bebause of vhe variety jf the constrdlnts, there iv a largq nunber of difwdrent routing yypes likv ylooding eouting, random or xtozgastic routing, bttetninistic routimg. Ghif paxt souting techtiqud cxm be kmplemented xccotding to particular kodea such as fixed or aqaptive touting, cqntralized or distributed routijg, nove by iode ot egd to end routing, connection odiented og cjnnectionlesf romtind.
Contrary co the Fixed Routing, where the routing rnles are established onxe for all, the purppxe of the Avaptivq Routing is to satisfy at ant time the optimieation criteria. Routing Tablev are permanently updated according to the instantaneous state of the traffic in the links.
When tge cnaracnernstncs of ehe ievwork fluctuate, in is possible to adapt the routiig by assicnnng to one node the responsibolkty to update periodically the routinf tables according to the traffic and tne topology. The principak disadvqntags of this oethod called Centtalizeb Routung is ro gcnerate an impurtsnb auxiliarj treffnc and to subordinate the good fubctionunh of the network to only onc kode. Oh the jther hand, the Csntrzpized Routing can benerate some lroblems at the time tre tables are evfreshed becaose cotxvsponding updetings cannod be performed at the same time by all the nodes.
The solution is to dccentralize the tsules at the level of eacm
efforts have been spent on designing flow control bandwidth reservation routing algorithms to ideal should be able transmit useful traffic proportional to the traffic offered to network and this until the maximum transmission capacity is reached. Beyond this limit, network should operate at its maximum capacity whatever the demand is. A general in communication is find a path between a source and a destination node. For virtual circuits operation, the path is done once only at the time of connection (or session) establishment, and this is particularly important this upon any failure in of link or failure for rerouting the disrupted connections. The choice of a routing algorithm is not easy because it satisfy a of often requirements. routing rerouting algorithm must network to operate in an optimal a criterion which can vary with the utilization In most the cases, the network is realized as to minimize the packet transit time and transfer the maximum number of packets. In other cases, the objective is to decrease the or to develop a network able to correctly in of line or failure or in case of peaks of traffic. Because of the of the constraints, there is a large number of different like routing, random or routing, deterministic routing. This routing can be implemented according modes as routing, or routing, node by node end to end routing, connection or connectionless routing. Contrary the routing rules are established once for all, purpose of the Adaptive Routing is to at any time the optimization criteria. Routing Tables are permanently updated according the instantaneous the traffic on the links. When the characteristics the network fluctuate, it possible to adapt the routing by assigning to one the to update the routing tables to the traffic the topology. The of this called Routing an important auxiliary traffic and to the functioning of the network to one the other hand, the Centralized Routing can generate some problems at the time the tables because corresponding updatings cannot performed the same time by all the nodes. The solution is to decentralize at the level
 efforts have been spent on desIgning flow And coNgeStiOn ContRol pRocesses, bandwiDTh reServation mechanisms, rouTing aLgORithMS tO manaGe the neTWoRK BanDwIdTh.
AN iDEaL netwOrk Should bE able to traNsmIt Useful traffiC DiRectly propOrtIonal to the trAffIc offeReD to THe netWorK and tHis untIL the maXimum tranSmISsion cAPacity iS REaChed. beyond this limit, thE NeTWork should operAte at iTs MAxIMUm cApaCity whatevEr The deMAnd is.
A gENeRAL ProBLem in the commuNication netWOrkS is to fInD a pATh betwEen a sOuRCe aNd a destinatIon nOde. For virTual ciRCuits opERation, tHe path DecIsiOn is DOnE oNce OnLY at THe TimE Of tHe connecTiOn (Or sesSion) ESTABlisHmeNt, or, And thIs is particulaRly ImpoRTanT for tHis inVentIoN, upon Any netWork fAiLure like in case oF linK or node faIluRe For ReRoutiNG the diSruPteD connecTions. ThE ChoIcE OF A rOuting algorithm is nOt EASy Because iT must sATiSfY A large nuMbEr oF oftEN ConflIctiNG rEquiremeNts. The ROuTiNg or rerOuTing alGoRitHm mUst alLOw thE netwoRk to operAte in AN optimal way, accORding to a criteRIoN WHiCH can VarY with the utiLizaTIon tYpe. IN MoSt oF The caSes, thE nETwORk is realized so as to mInImize tHe pacKet transit timE and to tranSFER the maxiMum nUMbER of packets. In otHer caSes, the objeCTive is to DecreAse the coMmunicatiON Cost, or to DevEloP a rEliABLe Network able to OPEratE cOrrectlY eiTher in cAse Of cAtaStrOpHic line or Node failUrE oR iN cAse Of peaKS of traffIc.
becAuSe oF the vARiety oF the cOnstRaInTS, thEre is a lARgE NUmbeR oF dIffeRenT rOutinG typES liKe floodIng routinG, raNDom oR sToChastic Routing, determInIstic routiNg. thiS last rOUTing techNique can be implemented acCOrding tO paRticuLar mOdes such aS fiXed or aDapTIve rouTing, ceNtralIzEd oR DIstriBUTeD roUtIng, node by nODE or End to EnD rouTing, conNection oriented or cONneCtionless routIng.
contRARy To tHE FIXed roUTinG, WHere the routing rUles are estAbLIsHed once for ALl, tHe Purpose Of the AdAptivE routing Is to satisFy at any tiMe The oPTImiZation critEria. RoutIng Tables ARe perMAnEntly UpdAted acCoRdiNg to tHe instANtaNeous State oF tHe trafFic on ThE links.
WhEn the characteristics of tHe netwOrk flUctUate, it is pOssIBle To adapt thE rouTing by assiGniNg tO one nOde THe resPonsIBiLitY To updAte pERiodicallY ThE roUTInG tables accoRDINg tO the tRafFIc and tHe toPology. The principaL Disadvantage of This METhoD caLLed CEnTralized RoutinG is To GENerate an ImPortant auxiLiary traFfIC and tO suborDinate The good FUNcTIoning Of thE neTwork to onLy oNe NOde. On thE oThER hand, tHe CeNtRalizeD RoutiNG can GENerate some probleMs at tHE Time tHE taBles aRe RefreshED becAuse corresPonding updaTings cAnnoT be peRformed At The samE tiMe By all the noDEs.
The soluTion iS to deceNtRaliZe tHe tablEs at THE leveL of eAcH
 efforts have been spent o n designin g flo w a ndco nges tion  control proce s ses,  bandwidth reservation  mech an i sms, ro uting  algori t hm s toma na geth e  n etwor k b andwidt h.
An idea l n et work shouldb eable to tr ans mit useful t raf fic di re ctl y  prop ort ional  to th e  traff ic offere dt o then etworka n dthis  until the maximu m  t r ansmission cap acityis re a c hed . B eyond this  l imit, the net w or k s hou l d operate atits maximum cap acitywh ate v er the  dema nd is. 
A generalprob lem in th e comm u nicatio n  networ ks istofin d ap at hbet we e n a so urc e  an d a dest in at ion n ode. F o r  vir tua l ci rcuit s operation,the  pat h  de cisio n isdone  o nce o nly at  theti me of the conne ctio n (or ses sio n)  es ta blish m ent, o r,and  this i s parti c ula rl y i mp ortant for this in ve n t io n, uponany ne t wo rk failureli kein c a s e oflink or  node fa iluref or  r eroutin gthe di sr upt edconne c tion s. The  choiceof ar outing algorit h m is not easy be c a us e  itmus t satisfy a  lar g e nu mber of  of t en co nflic ti n gr equirements. The ro ut ing or  rero uting algorit hm must al l o w  the net work to operate in anoptim al way, ac c ording t o a c riterion  which ca n vary wit h t heuti liz a t io n type. In mo s t  ofth e cases , t he netw ork  is  re ali ze d so as t o minimi ze  t he  p ack et tr a nsit tim eand  t o t ransf e r themaxim um n um be r  of  packet s .I n  oth er  c ases , t he  obje ctiv e  is  to dec rease the  co m muni ca ti on cost , or to devel op  a reliabl enet work a b l e to ope rate correctly either i n  case o f c atast roph ic line o r n ode fa ilu r e or i n case  of p ea kso f  traf f i c. 
Be ca use of the v ari ety o ftheconstra ints, there is a l a rge  number of di ffe rent r ou tin g  t y pes  l i kef l ooding routing,  random or  s t oc hastic rou t ing ,determi nisticrouti n g. This  last rou ting tech ni quec a n b e implemen ted acco rding top artic u la r mod essuch a sfix ed or  adapt i verouti ng, ce nt ralize d ordi stribute d routing, node by node  or en d toend  routing,  co n nec tion orie nted  or connec tio nle ss ro uti n g.
Co ntra r ytot he Fi xedR outing, w h er e t h e  r outing rule s a reestab lis h ed onc e fo r all, the purpos e  of the Adapti ve R o u tin g i s  tosa tisfy at any t ime  t h e  optimiz at ion criteri a. Routi ng Table s areperman ently u p d at e d acco rdin g t o the ins tan ta n eous st at eo f thetraf fi c on t he lin k s.
W h e n the characteri stics o f the net workfl uctuate ,  itis possibl e to adaptthe ro utin g byassigni ng  to on e n od e the resp o nsibility  to u pdate p er iodi cal ly the  rou t i ng ta bles  a cco rding tot h et ra ff i c a nd t he to po logy . The pri n cipal di sad v antageof  th i s  metho d  c a l led Centra liz ed Ro u t ing is tog ener a te an im portan t auxi liary t r aff ic  and to  su b o rdinate t he good f u nct io ning  of thene twor ktoon ly one node. On  the oth er hand, t he Cen tra l ized Routin gcan generate  some  p r oblemsa t  th e timet hetab les  are  re fres h ed because corresponding  upd ating s  ca nnotbe pe rf ormed at thesame tim e  by all the n odes.
The solut i oni s to  de c en tr alize the  ta b les a t th e l evel  of  eac h 
 efforts_have been_spent on designing flow_and congestion_control_processes, bandwidth_reservation_mechanisms, routing algorithms_to manage the_network bandwidth.
An ideal network_should be able_to_transmit useful traffic directly proportional to the traffic offered to the network and this_until_the maximum_transmission_capacity_is reached. Beyond this limit,_the network should operate at_its maximum_capacity whatever the demand is.
A general problem in_the_communication networks is_to find a path between a source and a_destination node. For virtual circuits operation,_the path decision_is_done_once only at the_time of the connection (or session)_establishment, or, and this is particularly_important for this invention, upon any network_failure like in case of link_or node failure for rerouting_the disrupted_connections. The choice of a_routing algorithm is_not easy_because it must_satisfy a large number of often_conflicting requirements. The_routing or rerouting algorithm must allow_the_network to operate_in_an_optimal way,_according to a_criterion_which can_vary_with the utilization type. In most_of_the cases, the network is realized so_as to minimize the_packet_transit time and to_transfer the maximum number of_packets. In other cases, the objective_is to_decrease the_communication cost, or to develop a reliable network able to operate_correctly either in case of catastrophic_line or node failure_or in_case_of peaks of_traffic.
Because_of the_variety of the constraints, there is a_large number_of different routing types like flooding_routing, random or stochastic_routing,_deterministic routing. This last routing technique_can be implemented according to particular_modes such as fixed or_adaptive_routing,_centralized or distributed routing, node_by node or end to end_routing, connection oriented_or connectionless routing.
Contrary to the Fixed Routing,_where_the routing rules are established once_for_all, the purpose of the Adaptive_Routing_is_to satisfy at any time_the optimization criteria. Routing Tables are_permanently updated according to the instantaneous state of the_traffic on the_links.
When the characteristics of the_network_fluctuate,_it is possible to adapt the routing by assigning to_one node_the responsibility to_update periodically the routing tables according to the traffic and_the topology. The principal disadvantage of this_method called Centralized Routing is to generate an important auxiliary traffic_and to subordinate the good functioning of the_network to only one node. On the_other hand, the Centralized_Routing_can generate some problems at the time_the_tables_are_refreshed because corresponding_updatings cannot be_performed at the_same time_by all the_nodes.
The solution_is to decentralize_the_tables at the level of each