Net Ne w t ork y La e y r Net Ne w t ork y La e y r Initial motivation: Net Ne w t ork y La e y r Net Ne w t ork y La e y r Net Ne w t ork

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1 None lef! IP6 Iniial moiaion: -bi address space soon o be compleel allocaed. Vin Cerf 67 ddiional moiaion: header forma helps speed processing/forarding header changes o faciliae QoS IP6 gram forma: fied-lengh 40 be header no fragmenaion alloed 68 IP6 Header (Con) Comparison of IP4 and IP6 Priori: idenif priori among grams in flo Flo Label: idenif grams in same flo. (concep of flo no ell defined). Ne header: idenif pper laer proocol for IP4: 0-e head IP6: 40-be head Oher Changes IP4 Checksm: remoed enirel o redce processing ime a each hop Opions: alloed, b oside of header, indicaed b Ne Header field ICMP6: ne ersion of ICMP addiional message pes, e.g. Packe Too ig mlicas grop managemen fncions Transiion From IP4 To IP6 No all roers can be pgraded simlaneosl no flag das Ho ill he neork operae ih mied IP4 and IP6 roers? Tnneling: IP6 carried as paload in IP4 gram among IP4 roers 隧道技术 7 7

2 Tnneling Logical ie: Phsical ie: E F nnel IP6 IP6 IP6 IP6 E F IP6 IP6 IP4 IP4 IP6 IP6 Tnneling Logical ie: Phsical ie: E F nnel IP6 IP6 IP6 IP6 C E F IP6 IP6 IP4 IP4 IP6 IP6 Flo: X Src: Src: es: E Flo: X Src: Src: es: E Flo: X Src: Flo: X Src: 7 -o-: IP6 -o-c: IP6 inside IP4 -o-c: IP6 inside IP4 E-o-F: IP6 74

3 Mobile neork Yanmin Zh eparmen of Comper Science and Engineering Global ISP Home neork Regional ISP Insiional neork Inrodcion Viral circi and gram neorks Wha s inside a roer 4 IP: Inerne Proocol aagram forma IP4 addressing ICMP IP6 Roing algorihms Link sae isance Vecor Hierarchical roing 6 Roing in he Inerne RIP OSPF GP Inerpla beeen roing, forarding Graph absracion roing algorihm local forarding able header ale op link Graph: G = (N,E) ale in arriing packe s header 0 N = se of roers = {,,,,, } E = se of links ={ (,), (,), (,), (,), (,), (,), (,), (,), (,) } Remark: Graph absracion is sefl in oher neork cones Eample: PP, here N is se of peers and E is se of TCP connecions 4 Graph absracion: coss Roing lgorihm classificaion c(, ) = cos of link (, ) - e.g., c(,) = cos cold alas be, or inersel relaed o bandidh, or inersel relaed o congesion Cos of pah (,,,, p ) = c(, ) + c(, ) + + c( p-, p ) Qesion: Wha s he leas-cos pah beeen and? Roing algorihm: algorihm ha finds leas-cos pah Global or decenralied informaion? Global: all roers hae complee opolog, link cos info link sae algorihms ecenralied: roer knos phsicallconneced neighbors, link coss o neighbors ieraie process of compaion, echange of info ih neighbors disance ecor algorihms Saic or dnamic? Saic: roes change slol oer ime namic: roes change more qickl periodic pdae in response o link cos changes 6

4 Link-Sae: ig Picre Inrodcion Viral circi and gram neorks Wha s inside a roer 4 IP: Inerne Proocol aagram forma IP4 addressing ICMP IP6 Roing algorihms Link sae isance Vecor Hierarchical roing 6 Roing in he Inerne RIP OSPF GP 7 Each node measres eer neighbor Each node sends able of neighbors o all nodes Eer node compes roing pah 8 Link-Sae Roing lgorihm ijskra s lgorihm ijksra s algorihm ne opolog, link coss knon o all nodes accomplished ia link sae broadcas all nodes hae same info compes leas cos pahs one node ( sorce ) o all oher nodes gies forarding able for ha node ieraie: afer k ieraions, kno leas cos pah o k des. s Noaion: c(,): link cos node o ; = if no direc neighbors (): crren ale of cos of pah sorce o des. p(): predecessor node along pah sorce o N': se of nodes hose leas cos pah definiiel knon 9 Iniialiaion: N' = {} for all nodes 4 if adjacen o hen () = c(,) 6 else () = 7 8 Loop 9 find no in N' sch ha () is a minimm 0 add o N' pdae () for all adjacen o and no in N' : () = min( (), () + c(,) ) /* ne is eiher old or knon 4 shores pah pls cos o */ nil all nodes in N' 0 ijksra s algorihm: eample ijksra s algorihm: eample () Sep 0 4 N' (),p(),,, (),p(), 4,,, (),p(), (),p(), (),p() 4, 4, 4, Resling shores-pah ree : Resling forarding able in : desinaion link (,) (,) (,) (,) (,)

5 ijksra s algorihm, discssion lgorihm complei: n nodes each ieraion: need o check all nodes,, no in N n(n+)/ comparisons: O(n ) more efficien implemenaions possible: O(nlogn) Oscillaions possible: e.g., link cos = amon of carried raffic +e e C e iniiall +e 0 +e 0 0 C recompe roing 0 +e 0 0 C +e recompe +e 0 +e 0 e C recompe Inrodcion Viral circi and gram neorks Wha s inside a roer 4 IP: Inerne Proocol aagram forma IP4 addressing ICMP IP6 Roing algorihms Link sae isance Vecor Hierarchical roing 6 Roing in he Inerne RIP OSPF GP 4 isance Vecor: Raional ellman-ford eample ellman-ford Eqaion (dnamic programming) efine d () := cos of leas-cos pah o Then d () = min {c(,) + d () } here min is aken oer all neighbors of Node ha achiees minimm is ne hop in shores pah forarding able Clearl, d () =, d () =, d () = -F eqaion sas: d () = min { c(,) + d (), c(,) + d (), c(,) + d () } = min { +, +, + } = 4 6 isance Vecor: ig Picre des cos ne hop U X W Inf - Inf - des V cos ne hop des cos s s s ne hop s disance ecor des cos ne hop inf - inf - inf - 7 isance Vecor lgorihm () = esimae of leas cos o Node knos each neighbor : c(,) Node mainains disance ecor = [ (): є N ] Node also mainains is neighbors disance ecors For each neighbor, mainains = [ (): є N ] 8

6 isance ecor algorihm (4) isance Vecor lgorihm () asic idea: From ime-o-ime, each node sends is on disance ecor esimae o neighbors snchronos When a node receies ne V esimae neighbor, i pdaes is on V sing -F eqaion: () min {c(,) + ()} for each node N Under minor, naral condiions, he esimae () conerge o he acal leas cos d () Ieraie, asnchronos: each local ieraion cased b: local link cos change V pdae message neighbor isribed: each node noifies neighbors onl hen is V changes neighbors hen noif heir neighbors if necessar Each node: ai for (change in local link cos or msg neighbor) recompe esimaes if V o an des has changed, noif neighbors 9 0 node able 0 7 node able node able () = min{c(,) + (), c(,) + ()} = min{+0, 7+} = ime () = min{c(,) + (), c(,) + ()} = min{+, 7+0} = 7 node able 0 7 node able node able () = min{c(,) + (), c(,) + ()} = min{+0, 7+} = ime () = min{c(,) + (), c(,) + ()} = min{+, 7+0} = 7 VR Shorcomings Solion: Spli Horion ih Poison Reerse VR is pre epensie: i rns o o be O(n ) hich is oo high for a fas conergence. In VR, here is he problem of con-oinfini in he presence of node crashes. Unsiable for large neork. Con-o-infini problem Spli Horion (SH): Roer does no ell roer he pah for X if he pah is hrogh SH ih Poison Reerse: Roer ells roer ha he pah for X has a meric of inf. 4 4