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by: Juvenal Beahan


Marketplace > University of Kentucky > ComputerScienence > CS 471G > NETWORKING AND DISTRIB OPERATING SYSTEMS
Juvenal Beahan
GPA 3.92

Zongming Fei

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Zongming Fei
Class Notes
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This 43 page Class Notes was uploaded by Juvenal Beahan on Friday October 23, 2015. The Class Notes belongs to CS 471G at University of Kentucky taught by Zongming Fei in Fall. Since its upload, it has received 12 views. For similar materials see /class/228214/cs-471g-university-of-kentucky in ComputerScienence at University of Kentucky.

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Date Created: 10/23/15
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venue mm UDP cnecksum HaneMew rem D 2r XOR R mathefrgrunllrsz39l 5 new 13m 5 5 nnmx 12m su CRC Example L nk Layer Want D 2 XOR R quot5 a 511mroducnon and a 5 o LmRe ayer swnches mm muva serwces a 57PPP E UVaE f v 7 7 W s r W a 5 2 Error devecnon D OR R m a EqUvaEnry 0 nd correct on a 5 SMMHp z access promoo s a 5 4 LmRewayer Addressmg a 5 5 Ethernet 5 E LmR Wmahzanon MPLS 5 Damn Din 5 s Mulh Ie Access LInks and Protocols Two types of a powevoepow 0 PW for mawp access 0 pmmrmrpmn hnk bevween Ewernev swwcn and has a broadcast snared wwz or mzdmm o u dfasnmned Enema 0 upsfreom HFC 0 80211 WV E ESS LAN 332 21 e AJ quot 1 n n q Mm mew mum mm mm m Wu 5 Mul hgle Access Erofocols D smg z snared broadcast channe or more swmuhanzous transmwsswons by nodes wzrfzrz C o eumsmn mmde recewes ku ur more swgna s av me some v me mUf 2 access mmm a murmured a gomnm mm determmzs new nodes 6 anne 2 determmz when node can transmn a commumcanon about channe snarmg must use channe Hsz o no uufrufrband cnanne for enurdmanun 5 Damn Din 5m Ideal Multiple Access Protocol Broadcast channel of rate R bps 1 when one node wants to transmit it can send at rate R 2 when M nodes want to transmit each can send at average rate RM 3 fully decentralized o no special node to coordinate transmissions o no synchronization of clocks slots 4 simple 5 mm Lilu 519 MAC Protocols a taxonomy Three broad classes El Channel Partitioning o divide channel into smaller quotpiecesquot time slots requency code 0 allocate piece to node for exclusive use El Random Access 0 channel not divided allow collisions 0 quotrecoverquot from collisions El Taking turnsquot 0 nodes take turns but nodes with more to send can take longer turns 5 DauLlnk Lilu 5 2a Channel Partitioninq MAC protocols TDMA TDMA time division multiple access El access to channel in quotroundsquot El each station gets fixed length slot length pkt trans time in eac round El unused slots go idle III example 6station LAN 13 4 have pkt slots 2 5 6 idle 6 slat l frame 4quot ML 5 DabLlnk Lilu 521 Channel Partitioninq MAC protocols FDMA FDMA frequency division multiple access El channel spectrum divided into frequency bands El each station assigned fixed frequency band El unused transmission time in frequency bands go idle El example 6station LAN 13 4 have pkt frequency bands 2 5 6 idle Random Access Protocols El When node has packet to send 0 transmit at full channel datarate R o no aprioricoordination among nodes El two or more transmitting nodes quotcollisionquot El random access MAC protocol specifies 0 how to detect collisions 0 how to recover from collisions 29 via delayed retransmissions El Examples of random access MAC protocols O slotted ALOHA O ALOHA O CSMA CSMACD CSMACA 5 mm Lilu 523 lime mm E 3 FDM cable E NU 5 osmium 522 W Assumptions Operation El all frames same size El when node obtains fresh El time divided into equal from fransmlls lquot quotz d39 i e slots time to 5l transmit 1 frame 0 ifno colision node can El nodes start to transmit and quot5 quot from iquot quotz d39 only slot beginning l El nodes are synchronized O ifCO s ioflv39 quotOde I E if 2 or more nodes retransmlts frame In transmit in slot all 295 SUbgzquzquotl5l nodes detect collision W P P quotquot1quot success 5 DauLlnk Lilu 5 24 Slotted ALOHA Slotted Aloha effluencx Efficiency longrun a max efficiency find new I fraction of successful slots pr 1h le uXimizes We many no es allwtth many p p c s s l a fo manynodes take limit of Npquot1pquotquotquot a supposeN nodes with as N goes to infinity Pm many frames to send gives a single active node can D WHISWHS Wuslmsl 5390 eac transmits in slot Max efficiency ie a7 continuously transmit D idle slots with probability p at full rate of channel D nodes mu b a prob that given node Ar bestchannel a highly decentralized dale 5 39539 quot 39quot 392 has success in a slot sed for use ul only slots in nodes m t39m mm timer transmissions 37 need to e in sync D at quotChronim oquot a prob that anynode has of timel D simple 5y a success NplepNquot 5 onsunever 525 5 Dmunk lever 5 2a Pure unslo t l39ed ALOHA Pure Aloha effluencx u unslotted Aloha simpler no synchronization Psuccess by given node Ptnode transmits a when frame first arrives o transmit immediately D collision probability increases 0 frame sent at tn collides With ot PVlo other node transmits in pnel pg PVlo other node transmits in pnel pg P 143 14 her frames sent n tneLtntl p 1p2 neg v m on i 4 r4 lirvi r e choosing apt mum p and then lettng n nfty e 122 e 1E even warsethan slotted Aloha 5 unaunk lever 5 27 5 Dmunk lever 5 2e le Access CSMA collisions spatial layout at nodes il collisions can still occur propagation delay means If channel sensed idle transmit entire frame 39W0 l s ma each other39s transmission D If channel sensed busy defer transmission collision entire packet transmission l a human analogy don39t interrupt othersl 39 2 WW note role of distance a propagation delay in determining collision probability 5 unaunk lever 5 2v 5 Dmunk lever 5 3n CSMACD Colllswn Defecflonl CSMACD collision defection CSMACD Currier sensing deferral us in CSMA o colllslons deferred llmz Wllhln SHON o collldlng lransmlsslons aborlzd reduclrlg channel waslagz erezua ll collision detection surz slgnal slrznglhs slgrlals 5 NS rzczlvzd slgrlal slr zrlglh cal lransmlsslon slrznglh a human analogy the polite convansallonallsl lefflcull lrlwlrzlzs LA overwhelmed by lo am anon 5 mullx lam 5m 5 mnn on 5a Taklng Turnsquot MAC Ero l ocols Taklng Turnsquot MAC Ero l ocols channzl parllllonlng MAC prolocols 05h Polllrlg are channel Effczrlryarld faryal nlgn load 0 nammnl al low load delay n n El masl 7 C mm mm lrlvllzs slave nodes lN bandWldln allocale even lf only 1 acllvz 39 quotWmquot M 39W nodal a lyplcally used nnn mm d b l d Random access MAC prolocols 1 S 2 W623 Oszlclzrll al low load SlYlng node can fully 5 WW LlllllZZ cnannal 0 pull quota warhead o lcllerl Slave onlgn load ColllSlOYl overhead 0 New PM Bf lakll lg lurns prolocols f ask for bzsl of boln worldsl allure masler 5 mullx lam 5m 5 mnn on 53A Tak39ng Turnsquot MAC Ero l ocols Summa of MAC Ero l ocols Tokznpasslrlg Hokequot asszd I a channzparrrmnmg by llmz frequzno or Code B 2241 nodzpm quotEX o Tlme Dlvlslun Frequency Dlvlslun Soqnonnally a random accamdynamlc a lokzn message WW 0 ALOH a some 5 mm o luken warhead srAloHA M LSMAcb 2 ensng easyl sumelechnuluglesWW2thlrl mnans wlreless o EMACl us Y o slngle palm uf fallure luken o pulllngfmm c2nlrcllsn2luk2n passng 0 Blaalamn FDDI IBM Taken R n9 5 mullx bill 535 5 mnn on 536 LAN Technologies Data link layer so far 0 Services error defecl ioncorrecfion mull39iple e ICC SS Nex l LAN Technologies 0 addressing O thernel O swifches O PPP 5 mm Lava 557 M El 5lIn139roducfion and El 5 6 Linklayer swifches services D 5 7 ppp El 5 2 Error defamequot u 5 8 Link Vir39lualizafion and correcl ion ATM MPLS El 5 3Mul1 iple access profocols El 5 4 LinkLayer Addressing El 5 5 thernel 5 mm Lava 5 5s MAC Addresses and ARP El 32bit IP address 0 networklayer address 0 used To gel dafagram To desfinal ion IP subnel El MAC or LAN or physical or Ethernet address 0 funcfion get frame from one interface 0 anoflrer physicallyconnected interface same nefuork O 48 bil MAC address for mosl LANs burned in NIC kOM also sometimes software seHable 5 mm Lava 555 LAN Addresses and ARP Each adapter on LAN has un que LAN address Broadcast address FFVFFVFFVFFVFFVFF adapter near7297mm 5 mm Lava 5 40 LAN Address g more 1 El MAC address allocal39ion adminisl ered by IEEE El manufacl urer buys porl39ion of MAC address space To assure uniqueness El analogy a MAC address like Social Securify Number l3 IP address like posfal address III MAC flaf address porfabilify O can move LAN card from one LAN to another El IP hierarchical address NOT porfable 0 address depends on IP subnel to which node is attached 5 mm Lava 541 ARP Address Resolu rion Pro rocol Ques on how To defermine El Each IP node hosf MAC address of B roufer on AN has knowing B39s IP address ARP Table III ARP fable IPMAC address mappings for A39ZF39WN39W39AD some LAN nodes 37 96723 WWW lt IP address MAC address TTLgt o a 2 391 5 3 239 9393 as 0 12 ll 3 m ess mapp ng will be forgotten lyp cally 20 min 7quot 5quot quot2 83953 aarzarbIFvznran U r 4rnr FrE3598 137 we 7 Ba 5 mm Lava 5 42 ARP protocol Same LAN network a A wants to send datagram to B and B39s MAC address a A caches saves IPto M not n A39s AkP table Ac addr par I D A broadcasts Akp query P table until information packet containing B39s IP becomes old mes out address 0 soft state39 Information 0 dest MAC address FF that times out 9 25 FFFFFFFFFF away unless refreshed 0 all machines on LAN El ARP is plugandplayquot receive AkP query 0 nodes create their All a B receives AkP packet tables mica repl es to A with its B39s intervention from lief MAC address administrator 0 frame sent loA s MAC address unicasl 5 new Lavei 543 DHCP Dynamic Host Configuration Protocol Goal allow host to dynamicalyobtain its IP address from network server when joining networ 0 support for mobile users joining network 0 host holds address only while connected and on allowing address r O renew address already in use III DHCP overview O 1 host broadcasts DHCP discoverquot ms 0 2 DHCP server responds with DHCP offerquot msg o 3 host requests IP address DHCP requestquot msg O 4 DHCP server sends address DHCP ackquot msg 5 mm Lavei 5 44 DHCP clientserver scenario v ng DHCP chem needs address in this 223 1224 network 5 mm Lavei 545 DHCP clientserver scenario arriving client 22 hsnsseiuniu 654 Lianne 3mm sees in es 2 56 Viadd11223124 hsnsseiuniu ass Lianne 3mm sees Livy 546 Addressing routing to another LAN walkthrough send datagram from A to B via R sume A knows B39s IP address 222222 22222 222222 I 222 w mimic El two ARP tables in router R one for each IP network LAN 5 new Lavei 547 D A creates IP datagram with source A destination B A uses All to get k39s MAC address for 111 111 111110 A creates nklayer frame with It39s MAC address as dest frame contains AtoB IP datagram A39s NIC sends frame R39s NIC receives frame an n an It removes IP datagrarn from Ethernet frame sees its destined to B It uses All to get B39s MAC address It creates frame conta n ng AtoB IP datagram sends to B an Yb Within 5 mm Lavei 5 4e L39 k Laxer39 a 511mroduc11on and a 5 o L1r1kr1ay2r sw11chzs szrvmzs a 5 7 PPP a 5 2 Error 112126110quot 0 5 E L1nW1r1ua11za11on and correcnon ATM and MPLS a 5 3Mu111p12 access pro1oco1s a 5 4 L1nk1ayer Addressmg a 5 5 E1h2rr121 s nauunx 1311 5A9 ther ne r dom1nar11 w1r2d LAN 1zchno1ogy a cheap 20 for NIC a f1rs1 w1d21y used LAN 1zchno1ogy a s1mp1er cheaper Man men LANs and ATM a kep1 up WWW speed race 10 Mbps 7 10 ebps MEMQVE E herne ske1sb s nnunx Din 5m Sfar39 Tagalogx a bus 10p01ogy popmar Waugh m1d 90s 0 c111 nudes 171 some cuH1s1ur1 dumc11r1car1 cuH1d2 Wm each u1h2r a 1oday smr 10p01ogy preva11s o amwe mm 71 cemer 0 each spake runs 0separa12E1h2N121pru1ucu1nud2s du quot11 cuH1d2 Wm each uMer bu saax1a1sab1e W s mm 1311 s51 ther ne r Frame Sfr39ucfur39e Sendmg adap1er encapsmmes 11gt da1agramor omer V121work1ay2r pro1oco1pack21m E1h2rr121 frame Preamb1e a 7 by1zs WWW panem 10101010 foHowzd by one bwz WWW paHzM 10101011 a used 10 synchromzz recewer sender c1ocwa1es s nnunx Din sex ETherneT Frame Sfruc rure more a Addresses o bwzs o 1fc1dap12r recewes frame wnh mmchmg d2s11r1c111ur1 address ur wwh bruadcas1 address egARPpack2111 passes dam 171 frame 1 nekurk 1ayerpm1ueu1 o u1h2rw1s2adap12r d1scc1rds frame a Type 1nd1ca1zs h1gh2r1ay2r pro1oco1mos11yIP bu1 omer poss1b1e e 9 New 1px App zTa k a cRc checked a1 rzczwzr 1f 2rror1s de1ec1ed fram21s dropped W ETherneT Unreliable connec rionless a connzc11on1zss No bandsbamg b21w22r1 sendmg and rzczwmg NICS a unr211ab12r2021v1ng NIC doesm send asks or Hacks 1o sendmg NIC o sweam uf damgmms passed 1 n21wurk 1C1er can have gaps m1ss r19 damgmms o gaps 111 11 d 1f app 1s us1ng TCP o mherw1s2 appw111 see s a E1h2rr121 s MAC pro1oco1 uns1o11ed CSMACD s nnunx Din ss1 ETherneT CSMACD algoriThm 1 NIC receives daTagram from neTwor layer ame 2 If NIC senses channel idle sTarTs rame Transmission If NIC senses channel busy waiTs unTil channel idle Then TransmiTs 3 If NIC TransmiTs enTire frame wiThouT deTecTing anoTher Transmission NIC is done wiTh frame I 4 If NIC deTecTs anoTher Transmission w ile TransmiTTing aborTs and sends jam signal 5 AfTer aborTing NIC enT 39 collision NIC chooses KaT random from 5 mink uyei 555 ETherneT39s CSMACD l more 1 Jam Signal make sure all oTher TrunsmiTTer39s are aware of collision 48 biTs Mbps erne for 3 wait t me is cime 50 msec Exponential Buckoff Soa a t retransmission attempts to estimated current loa 0 heavy load random wait will be longer a f rst collision clioose K from 01 delay is K 512 bit Transmission Times a after second collision clioose K from 0123 a after ten collisions clioose K from o12341023 5 mink one 555 CSMACD efficiency D T max prop delay beTween 2 nodes in LAN P39 P ll Tmquots Time To TransmiT maxsize frame e ciency ll efficiency goes To 1 o as tW goes too t goes to infinity 1 5t mm prop 0 CE 1 beTTer performance Than ALOHA and simple cheap decenTral izedl 5 mink uyei 5m 8023 ETherneT STandards Link amp Physical Layers ll manydifferenT ETherneT sTandards 0 common MAC proTocol and frame formaT O differenT spleeds 2 Mbps 10 Mbps 100 Mbps 6 s 16bps 10 o differenT physical layer media fiber cable naAsEefx tuna sen lDUEASESX lDDEASEEX copper i pair phys cal layer quot I iaaeaserk iaaeasm sier fiber phys cal layer 5 mink one 5m Manc hesTer encoding Moncnesiei Encoding ll used in 10BaseT each biT has a TransiTion DD synchronize To each oTher allows clocks in sending and receiving nodes To a no need for a centralized global clock among nodesl ll Hey This is physicallayer sTuffl 5 mink uyei 555 Link Layer ll 511nTroducTion and serVIces 5 2 Error deTecTion and correcTion 5 3 MulTiple access proTocols El 54 Linklayer Addressing El 5 5 ETherneT D E El 5 6 Linklayer swiTches El 5 7 PPP El 5 8 Link VirTualizaTion ATM MPLS 5 mink one 55 Hubs physicallayer quotdumbquot repeaters 0 bits coming in one link go out aoTher links at same r 0 all nodes connecTed To hub can collide wiTh one another 0 no frame buffering 0 no CSMACD at h 39 hosT NICs deTecT collisions A lwifled pair hub 5 555m Livei 551 Switch El link layer device smarter Than hubs Take acfive role 0 sTore forward Ethernet frames 0 examine incoming frame39s MAC address selectively forward frame To oneormore outgoing links when frame is To be forwarded on segmenT uses CSMACD To access segmenT D fransparenf O hosTs are unaware of presence of swiTches D pLg and pay sef earning O swiTches do noT need To be configured 5 imam Livei 5 52 Switch39 allows mufi e simultaneous Transmissions El hosTs have dedicated C direcT connecTion To swiTch swiTches buffer packets 1 El El Ethernet proTocol used on 6 x a each incomin link but no 5 4 collisions fu duplex C 0 each link is its own collision domain E El switchhngToA39 and B A ToB39 simultaneously Swfch wm SX mferfaces Without collisions 1334156 0 not possible with dumb hub 5 mini Livei 555 Switch Table A El 0 how does swiTch know That A39 reachable via interface 4 C B B39 reachable via interface 5 R El 4 each swiTch has a swiTch or c39 3 table each entry 5 I m 0 MAC address of host interface to reach hos me 5 amp C El looks like a routing Table E El Q how are enTries created A maintained in swiTch Table Witsi Witi m mer aces o something like a rout ng 1334566 I 5 Datum Livei 5 54 Switch selflearnin ilil iiquot El swiTch learnswhich hosTs can be reached Through C B which inTerfaces R 0 when frame received 6 6 3 switch quotlearnsquot location of 4 sender incoming LAN 5 segment C 0 records senderlocation pair n switch table 3 5mm fab2 faiy emp ry 5 555m Livei 555 Switch frame filterinqforwardinq When frame received 1 record link associaTed wiTh sending hosT 2 index swiTch Table using MAC desT address 3 if entry found for desTinaTion then if desT on segmenT from which frame arrived frame then drop the else forward The frame on interface indicated Else flock forward on albuf re interface on which ve frame arrived 5 imam Livei 5 55 Selflearning sgci forwarding examgle D frame destination unknown fmd 5mm fabe Winyawn s mm him 55 Infarconnecfing swt i ches a swncnes can be connected together x5 s c gigs 51 a gsendmg from A to F 7 how f l does 5 know to forward frame destined to F was and s v 3 a szif izammgi works exaciiy the same as m singizrswiich casei s mm Din 5a Self learnin leH39 with exam Ie Suppose c sends frame to I I responds to c x5 51 2i 5 W 4 51llt 6 a ab a gsnow switch mbies and packet forwarding m s 52 53 54 s mm lam sea Insfifufional nefwor k to 2m mi my work s mm Din 5m SwiTch 65 v Rou rers D both siorzrandrforward devices 0 ruuiers neiwurk ictyer devces examine neiwurk iciyer headers o wishes are ink ictyer devices a router s maintain routing iabizs impiemem routing aigoriihms swncnes maintain swncn iabizs impiemem fiiizrmg izarnmg aigoriihms n s mm ham 5 Summary comgar ison hubs traffic no isolation plug 6 play yes optimal no routing cut yes through router s switches s mm way 512 Llnk Layer a 511mroducnon and a 5 6 Hubs and swnchzs szrymzs D 5 7 p D 5 2 Error WWW a 5 E Lmkkuahzanon and corrzcnon ATM a 5 HMMHp z access promoo s a 5 5 Evhzrnzv s mm 13m 511 Pain 1390 Pain Da ra Link Confrol B one sender one PECEWZV one Wk zaswzr than broadcast Mk 0 no MzdxaAcczss CONFO OHDLC Hrgh 2v2 dam w comra Dara W used m be corsrdmd hwgh myer m profoco stacw s nnunx DIM 5H PPP Design Regulr zmznfs RFC 1557 a packet frammg encapsmmmn of rzrworwayzr daragram m dam mkframz Ocarry network ayzr dam of any network ayzr protoco not Just 1P ar same fmz oabmry m demump zx upwards bn rrarsparm musr carry any bn panzm m m dam mm a a error dzvzcnon no correcnon connzcnon hvznzss dmm swgna w fa urz m nszork ayzr nszork ayzr address negonanon Endpomf can zarrcomgurz Bach omzr39s network address a n s mm 13m 515 PPP no egulremen rs a errorcorrzcnonrzcoyzry a no ow comm m cm of order dzhvzry 0K a no need m supporr mmnpow mks 2 9 pong Error recovery ow comm datarzrordzrmg aH r2 2gavzd m hrgmr ayzrs s nnunx DIM 516 PPP Dafa Frame a ag dzhmnzr frammg a Address does rommg on y one opnor a Comm does rommg m rm mmrz posswbb muhwp z comm e ds a Promoo upper ayzr protoco m whmh frame dzhvzrzd zg PPPVLCP IP IPCP 2m m 2m 71ng comm ag mums s mm 13m 5 PPP Dafa Frame a mfo upper ayzr dambzmg carrrzd a chm cychc redundancy mm for error dBVZCHOYV Wm m2 2m Hug mulml ag undress s nnunx DIM 51x Bxfe Sfuff39ng Bxfa Sfuffing u datatransparency rzqmrzmzm 1111111112111 1M1 lt 3 bl b2 a11ow2d 1o1r1c1ud2 ag pa1 m o111111ogt Hugh b4 2 0amp15r2c21v2dlt01111110gtda1aor ag myquot 01111110 01111110 quot 2quot 2 b4 b1 b5 u Sender adds stuffs 2x1ralt o111111ogt by a zr each 1 o111111ogt dam by DRZCZW b5 b4 01111110 01111101 bzbl 01m 01111110 by s m arow d1scard m1 by comma da1 rzczpnon Hmmwmm PM 1 o111111o11 b 1 3111mmquot ost 2 09 y 2 ranxmmed dam 5 am 519 s mu m PPP Dafa Confrol Profocol Link Layer Before exchangmg HENMK 10W dam dam W W a 511mroduc11on and a 5 6 Hubs and sw11chzs 1M1 wvmzs a 57 PPP a con gure PPP 1m max D 5 2 E1101 112126110quot a 5 a 1m y1r1ua11za11on fram212n91h and 601126110quot ATM and MPLS au1h21111ca110 a 5 3Mu111p12 access a 12amcon11gu HENwk PW39OCO S 1ay2r1r1form 11011 D 5 WWW 10 P Carr IPcOn1ro1 Addmsmg Pro 1 ms a 5 5 E1h2rr121 con u 1 51mm 531 mu 512 Virtualization of networks The Inferne r vir ruulizin ne rworks V1Nua11za11on of resources powwm abs1rac11or1 m 197 W P E WWW WWW W Wm Mgmwmg r12 oaddressmg cunven uns oARPAn21 opacm farm a compmmg examp1zsv1r1ua1m2mory v1r1ua1 odamvmm enwm 02W mum dzv czs opackm sa 111 ne1wur1ltA1uba ommmg 0V1r1ua1 111061111123 2 9 Java WW Wynnequ from 196039570395 a 1ay2r1ng of abs1rac11ons dam swzw 1 112111115 of 1h21ow2r1ay2r omy 112111 w11b 10W 1ay2rs abs1rac1 2 sa 111 r121 5 mm 1311 5a 5 nnunx Div 531 The InTerneT virTualizinq neTworks Imernelwork layer 1P a addressing nlernelw appears ingleun Gateway or a embed merneiwork packets n Mom local packet formal or extract 2mm despite underlying local Wm network heterogeneity network of network a mule av mernelwork level lo 5 nzxi gateway saTelliTe net 5 mm Lava 5E5 ATM and MPLS El ATM MPLS separaTe neTworks in Their own righT O differenT service models addressing rouTing from InTerneT El viewed by InTerneT as logical link connecTing IP rouTers OjusT like dialup link is really parT of separaTe neTwork Telephone neTwork El ATM MPLS of Technical inTeresT in Their own righT 5 mm Lava 557 ATM archiTecTure 2nd sysrem mm mm endsysrzm El adapTaTion layer only aT edge of ATM neTwork O daTa segmenTaTionreassembly O roughly analagous To InTerneT TransporT layer El ATM layer quotneTworkquot layer 0 cell swiTching rouTing El physical layer 5 mm Lava 555 Cerf Sl Kahn39s InTerneTwork ArchiTecTure WhaT is virTualized El Two layers of addressing inTerneTwork and local neTwork El new layer IF makes everyThing homogeneous aT inTerneTwork layer underlying local neTwork Technology Oca e E O saTelliTe 0 56K Telephone modem OToday ATM MPLS invisible aT inTerneTwork layer Looks like a link layer Technology To IP 5 mm Lava 5 as Asynchronous Transfer Mode ATM III 199039s00 standard for high speed 155Mbps To 622 Mbps and higher Broadbandfnfegmfed Service Digital Network archiTecTure El Goal infegrafed endend fruitsJeri ofcarry Voice Vi eo daft O meeTing TimingQoS requiremenTs of voice video versus InTerneT besTefforT model 0 nexT generaTionquotTelephony Technical rooTs in Telephone world 0 packeTswiTching fixed lengTh packeTs called cellsquot using virTual circuiTs 5 mm Lava 5 SE ATM neTwork or link layer Vision endToend TransporT ATM from deskTop To deskTopquot 0 ATM isa neTwork ATM Technology quotalwm39k RealiTx used 0 connecT Q IP backbone rouTers 0 IP over ATMquot 0 ATM as swiTched link layer connecTing IP rouTers IP neTwork 5 mm Lava 5 an ATM Adaptation Layer AAL El ATM Adaptation Layer AAL adapts upper layers IP or native ATM applications to ATM layer ow El AAL present only in end systems not in switches El AAL layer segment headertrailer fields data fragmented across multiple ATM cel s O analogy TCP segment in many IP packets elmsystem mm mm endsysfem smmw 59 ATM Adaptation Layer AAL more Different versions of AAL layers depending on ATM service class D AALl for CBR Constant Bit Rate services eg circuit emulation El AALZ for VBR Variable Bit Rate services eg MPEG video El AAL5 for data eg IP datagrams Welgence subldye cm cm ML PW W M plum AA ATMCE l7 ATMCell gl a mum Luym 392 we subloye ATM Layer Service transport cells across ATM network El analogous to IP network layer El very different services than IP network layer rk service Guarantees Netwo Congestion Architecture Model Bandwidth Loss Order Timing feedback Internet best effort none no no no noinferred iao 5 ATM CBR constant yes yes yes no ra congestion ATM VBR guaranteed yes yes yes no ra e congestion ATM ABR guaranteed no yes no minimum ATM UBR none no yes no no 5 DalaLink LEVEV 5793 ATM Layer39 Virtual Circuits El VC transport cells carried on VC from source to dest 0 call setupteardown for each call before data can flow 0 each packet carries VC identif er not destination ID 0 everyswitch on sourcedest path maintain quotstatequot for each passing connection 0 nkswitch resources bandwidth buffers may be alocaredto V6 to get circuitlike perf El Permanent VCs PVCs 0 long lasting connections 0 typically permanent route between to IP routers El Switched VCs SVC O dynamically set up on percall basis 5 DalaLink Layer 5793 ATM VCs El Advantages of ATM VC approach 0 QoS performance guarantee for connection mapped to VC bandwidth delay delay jitter El Drawbacks of ATM VC approach 0 Inefficient support of datagram traffic 0 one PVC between each sourcedest pair does not scale N2 connections nee e O SVC introduces call setup latency processing overhead for short lived connections 5 DalaLink LEVEV 5795 ATM Layer ATM cell El 5byte ATM cell header El 48byte payload 0 Why small payload gt short cellcreation delay for digitized voice 0 halfway between 32 and 64 compromise Cellheader i 39 39 p p 39 ll Cell format 39cll man AL Len Payload mg m l i r unthiiinm M4 SM PD indimlcslnq all AALvLudmnw hiu aIaLink LEVEV 5795 ATM cell header D VCI vlrlual Channel ID lell channgrom llrlklo llrlk inra nei a PT Payload iype 2 g m cellvzrsus daia a cL Cell Loss Prlorlly bii cap 1 implies low prlorlly cell can be discarded if congesiion D HEC Header Error Checksum o cycllc redundancy check cell s mini iaisi ssi ATM Phxsmal Layer more Twaplzczs sublayzrs of physlcal layer a Tl nsrnission Convergence Sublayzr TCS adapis ATM layer above io PM sublayzr below a Pnysical Medlum bependeni depends on physlcal medium being used TCS Fanciions o Header checksuni generaiion E biis CRC 0 Cell delineation o wiin urislruclurzd PMD sublayzr iransrnission of idle cells when no daiacells io send s mini uni 553 ATM Phxsmal Layer Physical Medium Dependeni PMD subluyer D SONE SDH lransmlsslon frame slruclu c ing bl s l 0 several speeds 03 155 52 Mbps 0612 Mbps 0645 s 245 BbpsDCle 9 6 6b s a TITJ i rnission frame siraciare old ielepnone hlzrarchy15 Mbps 45 Mbps a nnStrndnredJuSl cells busyldlz re llkz a 622 08 s mini iaisi see I Ova ATM IP over ATM ClassicIP onl a s mini uni sim IP Over ATM s mini iaisi sini Dafagram Journey n I var ATM Nefwor k a ai Source Hosi 0 IF clyer maps beiween IF ATM aesi aaaress uslng APP 0 passes aaiagrain in AAL5 o AAL5 encapsulclles aaia segrneriis cells passes in ATM clyer a ATM network moves cell along vc io desiinaiion a ai besiinaiion Hosi 0AAL5 reassembles cells inio original daiagrarn o ifcRc OK daiagram is passed io IP s mini uni sin IPOver ATM Issues El IP daTagrarns inTo ATM AAL5 PDUs El from IP addresses To ATM addresses OjusT like IP ad resses To 802 3 AC Ethernet addresses LANS 5 mm Live 5 m5 MulTiQr39oTocol label swiTching lMPLSl III iniTia goal speed up IP forwarding by using fixed lengTh label insTead of IP address To do forwarding o borrowing ideas from Virtual Circuit vc approach 0 but IP duTugr39um still keeps IP address 39 MPLSheader 39i v l Z x 5 mm Live 5 m4 MPLS capable rouTers El aka label swiTched rouTer El forwards packeTs To ouTgoing inTerface based only on label value don39T inspecT IP address 0 MPLS forwarding Table disTincT from IP forwarding Tables El signaling proTocol needed To seT up forwarding SVPTE O forwardin possible along paThs ThaT IP alone would noT allow 9e g sourcespecific rouTing ll 0 use MPLS for Traffic engineering El musT co exisT wiTh IP only rouTers 5 DabLink Live 51D5 MPLS forwarding Tables 5 DaTaLink Live 51m ChopTer 5 Summary El principles behind daTa link layer services e ror deTecTion correction 0 sharing a broudcusT channel multiple access 0 link layer address no El insTanTiaTion and implemenTaTion of various link layer Technologies 0 ETherneT O swiTched LANS o PPP O virTualized neTworks as a link layer ATM MPLS 5 mm Live 51m ChopTer 539 leT39s Take a breoTh El Journey down proTocol sTack campere excepT PHV El solid understanding of neTworking principles pracTice could sTop here buT afs of inTeresTing Topics 0 wireless 0 mulTimedia O securiTy O neTwork managemenT 5 mm Live 51m Chapter 4 Network Layer e ppt siides riotmm on n la 39sl a il39fs39iiuifm Inllil xlamp hxl l l lvlu Hlehle WWW New7W9 amnesiaans anaaimia momma A rap Downppman h E winex se hm WW asi mansi misiu pew Jlm Kuraxe Keitn Rag ana 2392 aquot392 riii i39ii unasi mixing and AddiSDWWBSlWr MW at m M v to M7 Vs mt nimuuoiu nniai almanacW Arnein T m n k l r in Me an 391 Wonk law ei Chapter Network Layer Chapter goals El understand principles behind network layer services 0 network layer service rnodeis o torwarding versus routing 0W a router WOV S o routing patn seiection o deaiing nitn scaie 0 advanced topics IPv6 mobiiit El instantiation implementation in the Internet ankanw c2 Chapter 4 Network Layer a 4 1 Introduction a 4 5 Routing aigoritnms a 4 2 virtual circuit and o Llnk state datagram networks 0 Dlslcmce Veclur a 4 3 What s inside a rou ter a 4 6 Re i i 4 4 IP Internet quot392quot Protocol 0 RIP 0 baragram turmat 0 OSPF 0 IPv4 address rig 59 o ICMP roadcast and o 1va multicast routing anmk Layer u Network layer a transport segment from sen ing to receivtng host a on sending side encapsulates segments into datagrams a on roving side delivers segments to transport layer a network layer protocois in everynost router a router examines neader rieids in all IP datograrns passing through it ankanw u Two Key Network Layer Func l39ons El furwan ngrmove analogy ackets from router39s input to appropriate 339 quotWWW PFPCESS 0 router output planning trip from urce to dest El routingdetermine aken b route i El forwarding process packets from source of Be mg through to dest single interchange o reutrng agerrtnrns anmk Layer cs Inter la between rouf n and forward raan sioniinm lacal termini able Packds reader ankanw ca Connec rion se rug El 3quotd impor39fani39 funci ion in somenefwork archifecfures frame relay X 25 El before dafagrams flow Two end hosfs andini39ervening roufers esi39ablish virfual conneci ion O roufers gef involved El nefwork vs franspori layer conneci ion service 0 nefwork befween fwo hosfs may also involve inervening roufers in case of V s O fransporf befween fwo processes Network tam 4V7 Ne rwork service model Q Whai39 service modefor quotchannelquot franspori ing dafagrams from sender To receiver Example services for Example services for a individual dafa rams flow of dale rams III guaranfeed delivery El inorder dafagram delivery El guarani eed delivery wifh less Than 40 msec D guaranfeed minimum delay bandwidi h To flow El resi39ricfions on changes in infer packei spacing Network tow a Ne rwork layer service models Guarantees 7 Network SeNlCe Congestion Aroniteoture Model BandWidtn Loss Order Tlmll lg teedoaok internet oestenort none no no no no inferred iai i ATM CBR constant yes yes yes no rate oonoestion ATM VBR guaranteed yes yes yes no rate oonoestion ATM ABR guaranteed no yes no yes ini ATM UBR none no yes no no Network Layer w Chapier 439 Ne rwork Layer El 4 lIni39roduci39ion El 4 5 Roufing algorii hms El 4 2 Viri ual circuii and 0 Link slate dafagram nefworks 0 Distance Vector D 4 3 whafrs inside a o Hierarch cal rout ng roufer El 4 6 Roufing in The III 4 4 IP Internet 1mm Profocol 0 up 0 oatagrani format 0 OSPF 0 IPv4 addressing 0 35quot o ICMP El 4 7 Broadcasi and 0 IPv6 mulficasf roufing Network Layer AHEI Ne rwork layer connec rion and connec rionless service El da iagram network provides ne iwork layer connec iionless service El VC network provides ne iwork layer connec iion serv39ce El analogous To The Transpor i layer services but 0 service hosfi ohosi 0 no choice nefwork provides one or The ofher o implemenfafion in nefwork core keivsrk tom 47 Vir rual circui rs sourcefodesf pafh behaves much like Telephone circui quot o performancewise 0 network actions along sourcetodest path caii setup teardovin for each call before data can flow each packet carries vc ideniif er not destination host address an n everyrouier on sourcedesi path mu nia ns state for each pass rig connection ink router resources bandwidth buffers may be alocafedio vc dedicated resources pred ctabie service Neivsrk tam 4712 VC imglemen ra rion a VC consists of pafh from source To desfinafion VC numbers one number for each link along pafh enfries in forwarding Tables in roufers along pafh N 1 packet belonging To VC carries VC number ra rher Than desT address 1 VC number can be changed on each link 0 New VC number comes from forwarding fable Nelwark 13m 4713 Forwardin fable Mm Forwarding Table in Wzgfacz norfhwesf roufer W 239 Incoming interface Incoming vczz l Outh ng merface Outgotngvczz 1 12 3 22 2 63 1 1B 3 7 2 17 1 97 3 E7 Roufers main139ain connecfion sfafe informafionl Nelwark 13m 4714 Vir rual circui rs siqnalinq Dro rocols El used To sefup main139ain feardown VC El used in ATM framerelay X 25 El nof used in Today39s Infernef Nelwark Lam 15 Da rg ram ne rwor ks El no call sefup af nefwork layer El roufers no sfafe abou139 endfoend connecfions o no networklevel concept of quotconnectionquot El packefs forwarded using desfinafion hosf address 0 p kets between some sounce dest pair may take cu different paths Send data Nelwark Lam 471a Forwarding Table Deshnall n Address Range Lmk Interface ll l I l lll IUDIEIEIEIEI UEIEIEIEIEIEIEI mu ll l I l lll UUU1U111 11111111 ll l I l lll IUEIHEIEIEI UEIEIEIEIEIEIEI through ll l UUU1U111 IUEIHEIEIEI 11111111 ll l I l lll I ll l UEIEIEIEIEIEIEI Dug ll l I l lll IUEI11111 11111111 uthervnse 3 Netwm Law 4717 Longes r prefix ma rc hing Pre x Match Lmk lnta39face 11uu1ununun1n111nun1n 11 111101111111 111111111111 101111111111 1 11uu1ununun1n111nun11 z 3 Examples DA11001000 00010111 0001 when merface DA 11001000 00010111 0001 wntcn interface Netwm Law 4718 Dafagr39am or VC nefwar k why Internet damgram ATM vc D dam exchange Mme a evuwee frum fe ephuny cumpmers e a humancunversa un 39 5 mm W o svrwcmengehaany Wequot neqnnenens D W 5W2 0 need furguammeed cumpu ers serwce 0 can adapYperfurm D dumbn endsysmms cumru errur recuvery o vexepnnnes o snnpxe nsnee nekurk d WWW a ween o cump exny nnsn e nekurk a many nnwy p25 0 dwfferem enamae chs o umfurm serwce enmeuw Newark Lnyn m Chagfer 4 Network Laxer39 a 4 llmroducnon a 45 Rourmg a gomhms a 4 2 kua wow and o Lm sfme datagram networks I a 4 3 What s msnde a or mm rum quot9 router a 4 4 IP Internet Provoco 0 RIP 0 Damgmm farmquot 0 05 0 IPv4 addressmg 0 B o ICMP a 47 Broadcast and o 1va muhmasr rommg mme tzn Rou rer Archi rec rure Overview Two key router functions routmga gorwhmsprotocoMRIP 0st BEP a fwwardmgdamgrams from mcommg to outgomg W n n mum on Newark Lnyn m Inpu r Por r Func hons Physmc clyer aneve neeepnun Dam W M Decentralized switchin e g Evnennev see chapfer 5 g a gwen emagmnn des uukup umpm puN usmg furwurdmgmb e m quotpm pmquot memury a new emnpxeve mpm puN prunessmg an we speed a aueu ng w damgrams cwwe fesven Man urwardmg rave mm swnen fabr e mme e22 T hree r es of sw39 ch39n fab crossbar Newark Lnyn e2 Swrrchmg Vla Memory Fwsv generanon D tradquot CONFO uter wom compufers wnn swwchmg under dnem of cw Dpacke copwed to system s me speed ory D hm crossmgs p ned by memory bandwxdvh 2 bus 27 damgnam m n Dunn1 m m 91mm mme e2 switching Via a Bus D datagram from input port memory to output port memory via a shared bus a bus contention switc ing speed limited by bus bandwidth D 32 Gbps bus Cisco 56m sufficient speed for access and enterprise uters mum my 25 Switching Via An Interconnection Network D overcome bus bandwidth limitations Banyan networks other interconnection nets initially developed to connect processors in tiprocessor u advanced design fragmenting datagram into fixed length cells switch cells through the fabric a Cisco 12000 switches 60 Gbps through the interconnection network mum my eel Output Ports u suffeuugrequired when datagrams arrive from fabric faster than the transmission rate a Scheduling wscbiue chooses among queued quot datagrams for transmissio mum my 27 Output port Queueing Ouipul ton Corieniion pus Pockci or has i no letter B buffering when arrival rate via switch exceeds output line speed a queueing delay and loss due fa uufpuf part er a Verfaw mum my max How much buffering El RFC 3439 rule of thumb average buffering equal to quottypicalquot RTT say 250 msec times link capacity C C e C 10 Gps link 2 5 Gbit buffer El Recent recommendation with Nflows buffering equal to mum lay an In ut Port ueuin u Fabric slower than input ports combined gt queueing ay occur at input queues n HeadoftheLine HOL blocking queued datagram at front o queue prevents others in queue from orward mnnni porl coi lnnlloh gmsn packni iui only am led uxauiiunces HOL ulnckiiig as al in pssuai asquot anglened mum my man Chapfer 4 Ne rwork Layer El 4 lInfroducfion El 4 5 Roufing algorifhms El 4 2 Virtual circuil and o Ink 5 a e dafagram nefworks 0 Distance D 4 3 Whafts inside a o H erarchical routlng router El 4 6 Roufingl f a 4 4 IP Internet Wm Profocol 0 up 0 Datagram format 0 OSPF 0 IPv4 address ng 0 35quot Q Ich El 4 7 Broadcasf and 0 IPv6 multicast routing Network layer 4731 The Inferne r Ne rwork layer Hosf roufzr nszork layer funcfions Transport layer TCP L DP Nefwork layer ltnk layer Network layer 4732 Chapfer 4 Ne rwork Layer El 4 lInfroducfion El 4 5 Roufing algorifhms El 4 2 Virtual circuil and 0 Link state dafagram nefworks 0 Distance Vector D 4 3 Whafts inside a o H erarchical routing 139 rou er El 4 6 Roufing in The a 4 4 IP Internet Wm Profocol 0 up 0 OSPF o Datagram format 0 IPv4 address ng 0 35quot o ICMP El 4 7 Broadcasf and 0 IPv6 multicast routing Network layer 4733 IP da ragram forma r IP protocol yerston 32 ms number llolal datagram neader lengtn r Mad ypz of lengtn bytes bytes servlce 24 for type of data 167m WNW fra mettl 3 mber m2 0 upper Wer reassembly WW quot9 hops ltye la er enecksam WWW r39 32 btt source IP address Wm WM pmmm 32 blt dest natlon IP address 39 dB W PW Wd 390 obttons tf any E g ll neslamp PBCOV me how much warhead data mm Wm with TCP variable length MS of WW5 a 20 bytes of TCP vtlcullv a T6 to ytsttl D 20 by of IP or UDP segment D 40 bytes app layer overhead Network layer 4734 IP Fragmen ra rion amp Reassemblx a network nksnayewu max transfer Slzzr largest posstble lnkeleyel frame a large IP datagram dtytded fragmented wttlwt net 0 one datagram becomes ral datagrams o reassembled only at f nal desttnatton 0 IP header blts used to tdenttfy order related fragments Network layer 4735 IP Frgmen ra rion and Reassemblx d One large datagram becomes 9 seyeral smaller datagrams a MTU 1500 bytes 1430 bytes n data fleld D I offset 3quot MEDE Network layer 43o Chapter 4 Network Layer El 4 lIntroduction El 4 2 Virtual circuit and datagram networks El 4 3 What39s inside a router III 4 4 IP Internet Protocol 0 Datagram format 0 IPv4 address ng O ICMP 0 IPv6 El 4 5 Routing algorithms 0 in s u e 0 Distance Vector El 4 7 Broadcast and multicast routing Nelwark mm 4737 IP Addressin introduction 1 IP address 32bit QEIM 11 identifier for host 223 f router interface 2231 1 2 231 2 a El interface connection 2231 2 2 between hostrouter 223113 22313 27 I o router39s typ cally have multiple interfaces 223131 22313 2 o host typ cally has one nterface IP addresses associated With each 22311 111a11111aaaaaaa1aaaaaaa1aaaaaaa1 nterface 1 1 223 1 Nelwark mm 4733 Subnets III IP address 0 subnet part high der bits 0 host part low order bits El Whats a subnzf 7 0 device interfaces with same su net part OH 0 can physically reach each he without intervening router network consisi Ylg of 3 subneis Newark Law 4739 Subnets Recipe El To determine the subnets detach each interface from its host or router creating islands of isolated networks Each isolated network is called a subnet 223 1 3W2 Subnet mask 24 Network Lam Mn Subnets How many Newark Law 4741 IP addressing CI DR CIDR39 Classless InterDomain Routing O subnet portion of address of arbitrary length 0 address format ab c dx where x is bits in subnet portion of address hosi subnei par pan 11001000 00010111 00010000 00000000 200 23 16023 Network Law 4742 IP addresses how To ge r one Q How does has ge i IP address El hardcoded by sysi em admin in a file 0 Winfel confrolpanegtne1 workgtconfigurafion gtcpipgtproperies O UNIX efcrc config a DHCP Dynamic Hosf Configurafion Profocol dynamically gef address from as server 0 plugandplayquot Neiwark Layer 4743 DHCP Dynamic Host Confiqura rion Protocol Goal allow hosf To dynamicaIyobfain ifs IP address from nefwork server when if joins nefwor Can renewiis lease on address in use Allows reuse of addresses only hold address while connected an quotonquot Support for mobile users who want iojoin network more shortly DHCP overview O hosf broadcasi s DHCP discoverquot msg O DHCP server responds wifh DHCP offerquot msg o hosi requesi s IP address DHCP requesfquot msg O DHCP server sends address DHCP ackquot msg Neiwark Layer 4744 DHCP clien rserver scenario Client needs address in this Neiwark Low 4745 DHCP clien rserver scenario arriving clieni 22 liansaetianib 554 meme 3mm secs nn es 2 manual 24 liansaetianib 655 meme 3mm secs Low 44o IP addresses how To ge r one Q How does nefwork ge i subne i part of IP addr ge is alloca ied portion of its provider ISPs address space iSP s black iiEIEIiEIEIEI EIEIEIiEIiii EIEIEIiEIEIEIEI EIEIEIEIEIEIEIEI ZEIEI 2316 EIZEI Organizatiun El iiEIEIiEIEIEI EIEIEIiEIiii EIEIEIiEIEIEIEI EIEIEIEIEIEIEIEI ZEIEI 2316 ms Organizatiunl iiEIEIiEIEIEI EIEIEIiEIiii EIEIEIiEIEIiEI EIEIEIEIEIEIEIEI ZEIEI 2318 ms Organizatiunz iiEIEIiEIEIEI EIEIEIiEIiii EIEIEIiEIiEIEI EIEIEIEIEIEIEIEI ZEIEI 23 2D EIZa Organizatiun7 iiEIEIiEIEIEI EIEIEIiEIiii EIEIEIMMEI EIEIEIEIEIEIEIEI ZEIEI 23 3D EIZa Nsiwonk Low 4747 Hierarchical addressinq route aqqreqa rion H erarch cal address ng allows Effic em odvomsomom of rout ng nformaiion Organizaiian n Send me anyvhing wnn addresses beginning znn 23 Mil2U ernei Send me anything wnn addresses beginning m 31H nio Newark Low 4748 routes ISPseReUs has a more specmc route to Organization 1 o 52nd rne anyvhtng witr addresses oeainnina In 23 to nzu ternet 52nd rne anythth witn addresses oeainnina m 31D and or zuu 23 18 023 Network Lawn 4749 NAT Network Address Transla rion rest of lt local network Internet eghome tie 0 w 13E76297 Alduiugrums eownoiooai Datagrarns with source or network have s s ngle source destination in this network N dress 1387629 have 10 24 address for different source port numb source dest nation as usual 1 ers Network Lawn eat NAT Network Address Transla rion Implementation NAT roufer must 0 outgoing dafagrams repace source IP address porf 1 of evegg oufgoing dafagram To NAT IP address orf remofe clienfsservers will respond usintg NAT IP address new port 1 as desfinafion ad r new 0 remember in NA T fruitsaria fabg every source IP address port 1 To NAT IP ad ress new porf 1 franslafion i O incoming dafagrams repace NAT IP address new orf 1 in desf fields of ever incoming dafa w ram ifh correspondin source I address port gt sfored in NAT fabsle Network Lawn 453 IP addressing The last word Q How does an ISP ge i block of addresses ICANN Infernef Corporafion for Assigned Names and Numbers 0 allocafes addresses 0 manages DNS 0 assigns domain names resolves dispufes Network Lawn Ivan NAT Network Address Transla rion El Mofivafion local nefwork uses jusf one IP address as far as oufside world is conc d 0 range of addresses nof needed from ISP jusf one IP address for all devices 0 can change addresses of devices in local nefwork wifhouf nofifying oufside l O can change ISP wifhouf changing addresses of devices in local nefwork 0 devices inside local nef nof explicifly addressable visible by oufside world a securify plus Network Lawn 4752 NAT Network Address Translation NAT router Lhost10001 sends datagram to 12E 119 4013630 5 l nLaCMS o IZXHVAHIXA on if dest addr from 133762975001 13E76297 5001 to 100013345 Network Lawn 454 NAT NeTwark Address Translation D16biT portnumber field 0 so 000 simulTaneaus cannecTians virn a single LANside add essl D NAT is controversial QrauTers sneuld anly pracess up Ta layer 3 Qviala i es endreend argumenT NAT pussibiiiiy rnusibeia designers eg P2P applieaii ken inia aeeauni by app uns Qaddress sl39iarTage sl39iauld insTead be salved by IPv6 ruiva Lnyn ess NAT Traversal Eroblem u elienr viian Ta cannecT Ta server inirn address 10 o 01 0 server address 10 0 01 iueai rimquot in LAN eiieni can i use ii as desiinaiiun addr o uniy une exiernally vis bie NATied address 13876 297 7 u saluTlan 1 s l t lc ll my 323 eanfigure NAT Ta W war d 39 lricamlrig cannecTian requesTs aT given parT Ta server 0 e g 123 7b 29 7 puri 2500 always furwarded in 10 0 01 puri 25000 anwk Lnyn tsa NAT Traversal Eroblem D saluTian 2 Universal Plug and Play 0w InTerneT EaTeway m n M Device 15D PraTacal Allaws NATred nssr Ta39 s learn public I address 13 5 7e 29 7 enumeraTe eXisring parT 752953 rnappings ad e ave parT rnappings inirn lease Times ie auTamaTe srarie NAT parT rnap esnrigurarisn ruiva Lnyn m NAT Traversal Eroblem D saluTian 3 relaying used in Skype o NATed server esrapiisnes cannecTianTa relay 0 EXTer nal clienT cannecTs Ta rela y o relay bridges packeTs beTween Ta cannecTians a i eunneeiiun is relay niiiaied v by NAned nusi ism 2i7 NAT euier 2 eunneeiiuniu sins relay niiiaied rpyeiieni 3 reiayng clieni esiabiisned ankanyn tsx ChaETer 4 NeTwork Layer D 4 IInTraducTian D 45 RauTlng aigsrirnrns D 4 2 VirTual circuiT and o Llnk siaie daT rn ne 0 DlsianceVeciur D 4 3 Wpapis mm a o Herarenieairauiing rauTer D 4 6 RauTlng in rlie u 4 4 IP InTerneT WW PraTacal o baiagrarn fu ai 0 05 0 IPv4 address ng 5 o 1ch D 47 BreadcasT and o 1va mulTicasT rauTlng ruiva Lnyn tsv ICMP InTerneT CanTral Message PraTacal a used pynusis e ruuiers is cammunicme neiwarkrlevel W M W WNWquot u u eena ieriv ring 3 u uesi n Mikunveamable 2 WWWquot 3 l des1 nns1 unieacnable quotMCWBW quotWW 3 2 desrimamiuniesenspie ca 3 3 u ri unresenspie o eenu requesirepiyused 3 5 951 My W M bvr n9 3 7 ues nus unknown a neiwarkrlayer hbaveWP a u eeauenemeangesiian o 1ch msg mrried nIP SUV eaniiai rnm used dai agra n 8 n ecnn venues Ping s n mue sunniseneni Di gpygfggplggmdjym m in n mueiuisen iy mm mm 9 ii 0 inemiied g 12 I pad lP neader ankanyn ten Traceroute and ICMP a Suurce sends ser es at UDP segments to aest o rttst as m a wnen ICMP message GNWBS sauree ealeulates RTT 0 Second nas TT 2 et a Traceruule dues tnts 3 o Unlikelypmt numoet ttmes a wnen ntn datagram arrlves SluEE ng erttertan a UDP segment eventualty arrlves at aesttnattan nast a Desllnallun returns ICMP S w i nast unreaenable packet code u type 3 eaae a a wnen sauree gets tnts ICMP stops 0 Message include name ot toutete ID addtess anotk Layn c a 4 lIntroductton a 4 2 Vlrlual ctrcutt and datagram networks a 43 Wlnat39s tnstde a a 4 4 IP Internet 0 1va Chagter Network Laxer router a 46 Routtng tn tlne Internet Protocol 0 RIP 0 batagram farm t 0 05 0 IPv4 addressng 0 B o ICMP a 47 Broadcast and a 45 Roullrlg algorttnms o Hteraren eal rout ng multtcast routtng unwrap toz IPv6 ll Initial motivation 32bit address space soon o be completely allocated ll Additional motivation oneader tormat nelps speed pro oneader cnanges to tactlttate Q 1on datagram formal ottxedelengtn 40 byte neader o no tragmentatton allowed cesstngtorwardtng OS anotk Layn so IPv6 Header Cont prtartty identity priorle among datagrams tn tlow FawLab2 lderlllfy datagrams in same flow concept of flow not well dettned Nextleader lderlllfy upper layer protocol tor data unwrap so Other Changes from IPv4 El Citessum removed entirely to reduce processing time at each ho El Options allowed but outside of header indicated by Next Headerquot field El ICMPl r new version of ICMP oaddtttonal message types e g Packet Too Big omulttcast group management tuncttons anotk Layn us ll Not all routers can be up Ono Ylagda s 1on route s datagram among IPv4 rou Transition From IPv4 To IPv6 Q How will the nelworkoperule with mixed IPv4 and p 7 El fuming 1va carried as payload in IPv4 tars graded simultaneous unwrap no Tunneling A B E F Log ca v 2w 3 39 quotquot9 mo 1on 1on 1on A B F Phys ca wew E IPv6 Pm IPv4 pm Pm Pm Wmark mm 447 Tunneling A B E F Logwca wew WVWE g v3 1on 11m 1 pm A B c D E F WWW mwee 1 11m IPv4 IPv4 Pm v6 Pm I BrturC Evert E39 IPv mswde Ipv mwde IPv4 IPv4 Nemark Law We Chap rer39 4 Ne rwor k Layer El 4 lInfr39oducfion El 4 5 Roufing algorifhms El 4 2 Virtual circuif and 0 Ll k state dafagram nszor39ks 0 Distance Vector D 4 3 Whars inside a o H erarchical routing roufzr39 El 4 6 Roufing in The a 4 4 IP Infernzf 1mm Profocol 0 up 0 butugrum format 0 OSPF 0 IPv4 address ng 0 35quot o ICMP El 4 7 Broadcasf and 0 IPv6 mulficasf r oufing wvwark Law 449 Inferplay be rween r ou rinq forwardinq mmme amumhm ucaHquadmmame ue umpm hnk 3 vame m amvmg packers neade Newark Lam 47m Graph abs rr39ac rion Graph 3 NE N set ufruuters u v w x y z E set uf hnks u v u gtlt v x v vv X WL my my w zy 11 Remark Graph abstracnon s usz m other network contexts Examp z P2P where N s 52 of peers and E s 52 of TCP COHHZCHOHS vaark mm 4771 Graph abs rr39ac rion cos rs cgtltgtltj cos of hhh my 72gcwz5 OS C u a S hversey rehne v or mverseh r2 med congesnoh o d May b21or d obandwwdvh To Cost of path x x2 x3 xp cgtltgtlt2 cgtlt2gtlt3 cxprxp Quest s Wh the za osv path between u and z 7 Rouing algorifhm algorifhm ha finds Izasfcosf pah Newark mm 4772 Routing Algorithm classification Global or decentralized information Global u all routers have complete topology link cost nfo a link statequot algorithms Decentralized a router knows phys cally connected neighbors lnk u distance vectorquotalgorithms Static or dynamic Static El routes change slowly over t39me Dynamic III routes change more quickly 0 periodic update 0 in response to link cost changes Network toyer 73 Chapter 439 Network Layer El 4 1 Introduction El 4 5 Routing algorithms El 4 2 Virtual circuit and 0 Link state m networks datagra 0 Distance Vector D 4 3 whaf39s inside a o Hierarch cal rout ng router El 4 6 Routing In the III 4 4 IP Internet Wm Protocol 0 up 0 Datagram format 0 OSPF 0 IPv4 addressing 0 35quot Q Ich El 4 7 Broadcast and 0 IPv6 multicast routing Network toyer 4774 A LinkState Routing Algorithm D iJ39 kstra39s algorit hm a net topology lnk costs known to all nodes 0 accomplished via link state broadcastquot 0 all nodes have same nfo computes least cost paths from one node sourcequot to all other nodes n 0 gives forwarding table for that node iterative fter k iterat now least cost p st39s n ions k ath to k de U U Notation El cxy Ink cost from node y m if not direct ors Dv current value of cost of path from source to dest v pv predecessor node along path from source tov N39 set of nodes whose least cost path definitively known Network Layer 4775 Di 39sktra s Algorithm 1 Initialization 2 N Li 3 forall l lodes v 4 iiy adlaceniio u 5 enDyeuy 6 else Dv 7 8 Loop 9 iindwnot in N suchlhalDWlsamlnlmum to add Wto N it update Dy forall y adlaeent to w and not in N mll l Dv DW t cwv i3 new cost to y is either old 00 tto y orkrlowrl shortest path cost to w plus cost from w to y v is until all nodes in N39 Network Layer we Di 39kstra s al orithm exam le Network toyer 4777 l lm exam le 2 Resulting shoriesirgaih tree from u 95 Result rig forwarding table in u desi nation link Network toyer mu Di 39ks rra s algorithm discussion Chapler 4 Ne rwork Layer Algorifhm complexify n nodes El each iferafion need in check all nodes w noi in N E39 4 11quotquot0dud390quot D 4 5 Rouhng algorlfhms El nn12 comparisons 0n2 El 4 2 Virfual circui and 0 Lin sin e u more efficieni implemeniaiions possible 0nlogn dafagram quotefworks 0 35 Velma Oscillafions possible39 D 4 3 Whal39s inside 0 406 gm cu m quot9 39 1 El oufin in f e e 9 link cosf amounf of carried Traffic D 0 Infzmzf Infzmzf 9 Profocol 0 HP 0 Duiugram format 0 OSPF 0 IPv4 addressing 0 35quot Q ICMP El 4 7 Broadcasf and I1quot 1 1quot 39 I PECOmPuie recompuie recompute 0 IPv6 mu icas rou mg M iv Dunn Neiwank mm 4779 Nelwark Lam ran Dis rance Vec ror Algori rhm BellmanFord example Bellman Ford Egua lion dynamic programming Define dxy cost of leas l cos l path from x To y Clearly dvz 5 dxz 3 dWz 3 BF equafion says duz min cu v dvz 6 Then V 7 cuwd 2 5 dxiy min cm dim 13 4 Node fhaf achieves minimum is next where min is Taken over all neighbors v of x hop in shor39fzsf Pafh gt forwarding fable Neiwk Linen Hi Newark Linen 4782 Dis rance Vec ror Algori rhm Dis rance vec ror algori rhm 141 El Dxy es lima le of least cost from x To y Basic idea lj Node x knows 5051 10 each neighbor V El Each node periodically sends ifs own disfance C V vecfor esfimafe To neighbors El When a node x receives new DV esfimafe from D Node gtlt main rains disfance VCC FOI Dx neighbor ii updafes iis own DV using BF equafion Dxy y e N 1 El Node x also maintains its neighbors39 0x0 quot vcX 39 0 for WM quotMWE N d39STance vealor s El Under minor nafural condifions The esfimafe 0 For each neighbor v x mainfains DXy converge 0 re acfua Izasf cost dxy DV Dvy y a N Neiwi linen Ha Newark linen 4784 Distance Vector Algorithm 51 Iterative asynchronous Each node each local iteration caused wait forchange in local link a local link cost change cost ormsg from neighbor D DV update message from neighbor Distributed recompute eSllmaleS D each node notifies neighbors onywhen its ov Chm ib h f it Dv to any deal has neig ors t en noti y MW Wghbm f changed notifyneighbors ssary Network layer 4785 node We mln yj o cx 2 t 0le 70 a DAY m quotCXiv DYW CXiz 39 Dom in M20 71 2 node x table Network Layer 4787 Distance Vector link cost changes Link cost changes a bad news travels slow count to infinity39 problem D 44 iterations before algorithm stabilizes see text Poisoned reverse a If 2 routes through v to get to X o z tells v its Z s distance to X is nflnlte so v won39t route to X vlaz a will this completely so ve I count to infinity problem Network layer 4789 x table Z oooo to node ztable S m V DAV mmldxv Dyw CXiz Dom m n2t0 71 2 0J2 m quotifXV t D I CXJ DJIJ mn2 1703 tme Network layer teuo Distance Vector link cost changes Link cost chan es an a if ov changes notify neighbors 9 node detects local link cost change updates routing nfo recalculates distance vector lme ty ydelecls the llnkrcosl change updates its bv l bors ne gh At t and informs lls 5quot Alllme t e r zrecelves the update from yand updates its table It computes anew least cost to x and sends its neighbors lts D zyreceives 2 s update and updates its distance table s least costs do not change and hence y does notsend any Network Layer 4788 Comgarlson of LS and DV algorithms Message complexity a Ewith n nodes E links OnE msgs sent a DV exchange between neighbors on o convergence time varies S eed of Convergence on algorithm requires OnE msgs n 0 may have oscillations y convergence time varies 0 may be routing ps 0 countto nfinity problem a Robustness what happens if router malfunctions g node can advertise incorrect linkcost each node computes only its om table 0 DV node can advertise incorrect pom cost each node39s table used by others 0 error propagate thru network Network layer mu El 4 lIntroduction El 4 2 Virtual circuit and datagram networks El 4 3 What39s inside a router III 4 4 IP Internet Protocol 0 Dutugrum format 0 IPv4 address ng O ICMP 0 IPv6 Chapter 4 Network Layer El 4 5 Routing algorithms 0 in s u a El 4 7 Broadcast and multicast routing Network Layer ml Hierarchical Routing Our routing study thus far idealization I all routers identical El network flat39 noftrue in practice scale with 200 million d administrative autonomy estlnatlons f a internet ne work o a 39 networks routing tables a each network admin mu routing table exchange want to control routing in its would swamp llnksl Wquot quotE WW a Network Layer 4792 regions autonomous systemsquot A 5 El same routing protocol 0 quotintroASquot routing protocol 0 routers in different A5 can run i erent intru AS routing protocol El aggregate routers into routers in same A5 run Hierarchical Routing Gateway router El Direct link to router in another A5 Network Low 4793 Interconnected ASes routing algorithm 0 introAS sets entries for internal dests Network Low 4794 InterAS tasks El suppose router in A51 receives datagram dest outside of A51 0 router should forward packet to gateway router but whic A51 must 1 learn which dests reachable through A52 which through A53 2 propagate this reachability info to all routers in A51 Job of interA5 routing Newark Low ma Exam le Settin forwardin table in router 1d El suppose A51 learns via interA5 protocol that subnet Xreachable via A53 gateway 1c but not via A52 El interA5 protocol propagates reachability info to all internal routers El router 1d determines from intraA5 routing info that its interface I is on t e least cost pat to 1c 0 installs forwarding table entry 9139 Nslwonk Low we Example Choosinq amonq mulTiple ASes Example Choosinq amonq mulTiple ASes El now suppose A51 learns from inTerA5 proTocol ThaT El now suppose A51 learns from inTerA5 proTocol ThaT su neT XlS reachable from A53 andfrom A52 su neT XlS reachable from A53 andfrom A52 El To configure forwarding Table rouTer 1d musT El To configure forwarding Table rouTer 1d musT de ermine Towards which gaTeway iT should forward de ermine Towar s which gaTeway iT should forward packeTs for d sT x packeTs for d sT x O This is also job of inTerA5 rouTing proTocoll 0 This is alsojob of inTerA5 rouTing proTocoll u hoT poTaTo rouTing send packeT Towards closesT of Two rouTers Leavn 1mm mews U59 WW W Hm potato mulmg quotW S cruussme galan 51 Thai haslhe Eupth B Each smalles eas cus1 Pmlucui in delevrnine multiple ualevvavs disassch NeTwork mm 4797 Nelwark mm ma ChapTer NeTwork Layer InTra AS RouTing El 4 lInTroducTion El 4 5 RouTing algoriThms El also known as InTerior GaTeway ProTocols IGP El 4 2 VirTual circuiT and 0 Li k 5 El mosT common InTraA5 rouTing proTocols daTagram neTworks 0 Distance Vector El 4 3 WhaT39s inside a 0 H arm39Cl icul quot quot quotB 0 RIP RouTing InformaTion ProTocol rouTer 5 Il6 R lquot9 lquot 5 0 O5PF Open 5horTesT PaTh FirsT u 4 4 IP InTerneT quotmm ProTocol 0 11 o IGRP InTerior GaTeway RouTIng ProTocol CISCO o DaTagram human 0 OSPF proprieTary 0 IPv4 address ng 0 35quot o ICMP El 4 7 BroadcasT and 0 IPv6 mulTicasT rouTing Newark Law 4799 Newark Lam 47mm ChapTer 4 NeTwork Layer RIP RouTinq InformaTion ProTocol El 4 lInTroducTion El 4 5 RouTing algoriThms El disTance vecTor algoriThm El 4 2 VirTual circuiT and 0 Link sTuTe El included in BSDUNIX DisTribuTion in 1982 daTagram neTworks 0 D39S m Vec W n disTance meTric 1 of hops max 15 hops D 4 3 Whars inside a o H erarchlcal rouTing mm D 4 6 Rou ng lquot H39z From router A m subsets u 4 4 IP InTerneT mm 39 destination m ProTocol 0 k1 U 1 o DaTagram human 0 OSPF VW S 0 IPv4 address ng 0 35quot x a o ICMP El 4 7 BroadcasT and y 3 0 IPv6 mulTicasT rouTing z 2 Newark mm mm Newark mm Hue RIP adver risemen rs El disfance vecfors exchanged among neighbors every 30 sec via Response Message also called adver risemen r El ech adverTisemen r lisT of up To 25 desTinaTion neTs wiThin AS Newark Lemmas RIP39 Example equot 9339 Destination Network Nux39 Romu Num of hops to dust A 2 y B 2 z B 7 x 1 Rowing table in D Nelwark mm 471m Advar scmun39 m A to C Institution anork NIX Router Num of hops to d39 A 2 y B 2 z XA X5 x 1 Rour rig table n D wlwark LayerIHEIE eggan RIP39 Link Failure and Recovery If no adverfisemenf heard offer 180 sec gt neighborlink declared dead 0 roufes via neighbor invalidafed 0 new adverfisemenfs senf To neighbors O neighbors in furn send ouf new adverfisemenfs if fables changed 0 link failure info quickly propagafes To enfire nef poison reverse used To prevenf pingpong loops infinife disfance 16 hops Newark mm Hue RIP Table processing III RIP roufing fables managed by application level process called roufed daemon El adver39i39isemenfs senf in UDP packefs periodically repeafed routed routed remark LayeNHEV Chap rer 439 Ne rwork Layer El 4 lInfroducfion El 4 5 Roufing algorifhms El 4 2 Virfual circuif and 0 Link slate dafagram nefworks 0 Distance Vector D 4 3 whafrs inside a o Hierarch cal rout ng roufer El 4 6 Roufing in The a 4 4 IP Infernef 1mm Profocol 0 up 0 outugram format 0 OSPF 0 IPv4 addressing 0 35quot o ICMP El 4 7 Broadcasf and 0 IPv6 mulficasf roufing Newark mm m OSPF Ogen Shortest Path F rst a quotopenquot publicly available u uses Link State algorithm 0 LS packet dlssemlnallun o lupulugy map at each nude 0 ruule cumpulahun usng Dleslra39s algumlhm a OSPF advertisement carries one entry per neighbor router a advertisements disseminated to entire AS via looding 0 carried n OSPF messages dlreclly aver IP rather than TCP ur UDP Nam LuyIrALl V OSPF advanced features not n RIP ent malicious intrusion a multiple samecost paths allowed only one path in III a security all 0er messages authenticated to prev 39 a For each link multiple cost metrics for different Tos e g satellite link cost set Iovll39 for best effort high for rea time a integrated uni and multicast su port 0 lviulticast OSPF MOSPF uses same topology data base as OSPF a hierarchical OSPF in large domains Nam hiya Min Hierarchical OSPF J boundolylolilel backbcnelollel Nam luya 4m Hierarchical OSPF o Linkstate advertisements only n 0 each nodes has detailed area topology only know direction shortest path to nets in other areas a oreaborderroufe 39 summarize distances to nets in own area advertise to other Area Border routers a backbone routers run OSPF routing limited to backbone a boundarzroufersrconnect to other AS39s e n t Nam hiya A112 Chagter 4 Network Layer a 4 11ntroduction a 4 5 kouting algorithms D 42 rtual circuit and 0 Link stale atagram ne works 0 Dlslance Veclur D 4 3 What39s inside a o H erarchlcal ruulmg router a 4 6 kouting in the a 44 IP Internet Mamet Protocol RIP 0 balagram furmal OSPF o IPv4address ng o ICMP D 4 7 Broadcast and o 1on multicast routing Nam luya 4m Internet inter AS routing BGP ll BGP Border Gateway Protocol the de facto stan ard ll BGP provides each AS a means to 1 Obtain subnet reachability information from neighboring A s 2 Propagate reachability information to all AS internal routers 3 Determine quotgoodquot routes to subnets based on reachability information and poli ll allows subnet to advertise its existence to rest of Internet quotI amlrere Nam hiya 4114 BGP basics El pairs of rouTers BGP peers exchange rouTing info emipermanenT CP connecTions BGP sessions 0 sessions need noT correspond To physical In 5 El when A52 adverTises prefix To A5139 0 A52 promises iT will forward daTagrams Towards ThaT pref any addresses ix 0 A52 can aggregaTe prefixes in iTs adverTisemenT 2w session iEPsessian Newark mm 4415 PaTh aTTribuTes amp BGP rouTes El adverTised prefix includes BGP aTTribuTes O prefix aTTribuTes quotrouTequot El Two imporTanT aTTribuTes O ASPATH conTains A5s Through which prefix adverTisemenT has passed e g A5 67 A517 0 NEXTHOP indicaTes specific inTernalA5 rouTer To nexThop A5 ma be mulTiple links from currenT A5 To nexT opA5 El when gaTeway rouTer receives rouTe adverTisemenT uses imporT policy To accepTdecline Newark Law 4417 BGP messages El BGP messages exchanged using TCP u BGP messages 0 OPEN opens TCP connecTion To peer and auThenTicaTes sender 0 UPDATE adverTises new paTh or wiThdraws old 0 KEEPALIVE keeps connecTion alive in absence of UPDATES also ACKs OPEN requesT O NOTIFICATION reporTs errors in previous msg also used To close connecTion Nmm Law 4419 DisTribuTing reachabiliTy info Ix reachabiliTy info To A5 c can Then use iBGP do disTribuTe new prefix info To all rouTers in A51 01b can Then readverTise new reachabiliTy info To A52 over 1bTo2a eBGP sessi El when rouTer learns of new prefix creaTes enTry for prefix in iTs forwarding Table El usin1g eBGP session beTween 3a and 1c A53 sends pre 39 1 01 236v session Nelwark mm 471m BGP rouTe selecT ion El rouTer may learn abouT more Than 1 rouTe To some prefix RouTer musT selecT rouTe El eliminaTion rules local preference value aTTribuTe policy decision 2 shorTesT A5PATH a closesT NEXTHOP rouTer hoT poTaTo rouTing 4 addiTional criTeria Nelwark Law 4418 BGP rouTing policy le end rovider39 9 CW cusTomer neTwork 0 El A BC are provider neTworks El X W Y are cusTomer of provider neTworks III X is dualhomed aTTached To Two neTworks O X does noT wanT To rouTe from B via X To C 0 so X will noT adverTise To B a rouTe To C Newark Law 4712 BGProuTin olic 2 le end rovider39 9 Clem cusTomer neTwor39 El A adverTises paTh AW To B El B adverTises paTh BAW To X El Should B adverTise paTh BAW To C O No way B geTs no quotrevenuequot for rouTing CBAW since neiTher W nor C are B39s cusTomers O B wanTs To force C To rouTe To w via A O B wanTs To rouTe onyTofrom iTs cusTomersl Newark Layer 442i Whv differenT InTra and InTer AS rouTinq Policy El InTerAS admin wanTs conTrol over how iTs Traffic rouTed who rouTes Through iTs neT El InTraAS single admin so no policy decisions needed Scale El hierarchical rouTing saves Table size reduced updaTe Traffic Performance El InTraAS can focus on performance El InTerAS policy may dominaTe over performance Nelwark Layer 4422 ChopTer 4 NeTwork Layer El 4 lInTroducTion El 4 5 RouTing algoriThms El 4 2 VirTual circuiT and 0 Ll k sTuTe daTagram neTworks 0 Distance Vector D 4 3 Whaps inside a o H erurchicul rouTing rouTer El 4 6 RouTing in The III 4 4 IP InTerneT 1mm ProTocol 0 up 0 DuTagrum human 0 OSPF 0 IPv4 address ng 0 35quot o ICMP El 4 7 BroadcasT and 0 IPv6 mulTicasT rouTing Newark LayeNHZS BroadcasT RouTin El deliver packeTs from source To all oTher nodes El source duplicaTion is inefficienT duvllcale siesasnmsnsnssisn source lnrnetvvurk dupllcatlun dupllcatlun El source duplicaTion how does source deTermine recipienT addresses Newark Layer 4424 InneTwork duglicaTion El flooding when node receives brdcsT pckT sends copy To all neighbors 0 Problems cycles di broadcasT sTorm El conTrolled flooding node only brdcsTs ka if iT hasn39T brdcsT same packeT before 0 Node keeps Track of pckT ids already brdcsTed 0 Or reverse paTh forwarding RPF only forward pckT if iT arrived on shorTesT paTh beTween node an urce El spanning Tree 0 No redundanT packeTs received by any node Newark lawman Spanning Tree El FirsT consTrucT a spanning Tree El Nodes forward copies only along spanning Tree 5 5 a BroadcasT initiated at A b BroadcasT initiated at in Newark lam seize S annin Tree39 Crea rion El Cenfer node El Each node sends unicasl39 join message To cenfer node 0 Message forwarded uniii ii arrives at a node already e belonging to spanning ire a Stepwise construction b Constructed spanning ofspanning tree tree Wlwark Laper4ei27 Mul ricos r Rou rinq Problem S ra remen r El Seal find a Tree or Trees connec ling rou lers having local mcas l group members 0 free not aii paths between nouiens used 0 sourcebased different tree from each sender to rcvrs o sharedfree same inee used by aii group members Shared lree Sourcerbased trees Approaches for building mcos r Trees Approaches El source based free one free per source 0 shor39iesf pafh Trees 0 reverse pafh forwarding El group shared free group uses one Tree 0 minimal spanning Sfeiner O cenferbased frees we firsf look of basic approaches Then specific profocols adopfing These approaches Shor res r Pa rh Tree El mcas l forwarding free free of shortest path routes from source To all receivers O Dijksfra39s algorifhm LEGEND 5 source quot R n n d rouler Wll allac 2 group member rouler Wilh no attached Q group member Q link used for forward ng l k ndieaies order iin added by algorilhm Reverse Pa rh Forwarding El rely on rou ler39s knowledge of unicas l shor les l path from ii To sender El each router has simple forwarding behavior if mcasf dafagram received on incoming link on shorfesf pai39h back To cenfer their flood dafagram onfo all oufgoing links else ignore dafagram Reverse Pa rh Forwardin exam le S source 70 LEGEND rouier Wiin allached group member rouier Wiin no allached 9 group member dalagram Will be forwar e ddalagram Will nor be orwarded resulf is a sourcespecific reverse SPT may be a bad choice wifh asymmefric links Reverse PaTh Forwardin 39 runin El forwarding Tree conTains subTrees wiTh no mcasT group mem ers 0 no need To forward daTagrams down subTree O prune msgs senT upsTream by rouTer wiTh no downsTream group members 5 source quot3 LE END router Wllh attached groupmember router with no attached V group member P prune message links Wilh mullicasi forward ng SharedTree STeiner Tree El STeiner Tree minimum cosT Tree connecTing all rouTers wiTh aTTached group members El problem is NP compleTe El excellenT heurisTics exisTs El noT used in pracTice O compuTaTional complexiTy O informaTion abouT enTire neTwork needed 0 monoliThic rerun whenever a rouTer needs To joinleave CenTerbased Trees El single delivery Tree shared by all El one rouTer idenTified as quotcenferquotof Tree El To Join O edge rouTer sends unicasT joinr1155 addressed To cenTer rouTer Ojoinmsy quotprocessedquot by inTermediaTe rouTers and forwarded Towards cenTer OjoinmsyeiTher hiTs exisTing Tree branch for This cenTer or arrives aT cenTer O paTh Taken byjoinmsybecomes new branch of Tree for This rouTer CenTerbased Trees an example Suppose R6 chosen as cenTer LEGEND router Wllh attached group member Q router Wilh no attached group member gt path order n whichJom neraied InTerneT MulTicasTing RouTing DVMRP El DVMRP disTance vecTor mulTicasT rouTing proTocol RFC1075 El ood andprLne reverse paTh forwarding source based Tree 0 RPF Tree based on DVMRP39s own rouTing Tables consTrucTed by communicaTing DVMRP rouTers 0 no assumpTions abouT underlying unicasT O iniTial daTagram To mcasT group flooded everywhere via RPF O rouTers noT wanTing group send upsTream prune msgs DVMRP conTinued El soff sfafe DVMRP rouTer periodically 1 min forgeTs branches are pruned39 O mcasT daTa again flows down unpruned branch 0 downsTream rouTer reprune or else conTinue To receive daTa El rouTers can quickly regrafT To Tree 0 following IGMP join aT leaf El odds and ends 0 commonly implemenTed in commercial rouTers O Mbone rouTing done using DVMRP Tunneling Q How To connect quotislandsquot of mul iicas i rouTers in a sea of unicas i rouTers x phys cal lopology logical lopology moaut datagrarr encapsulated inside quotnormalquot nonmulticast addressed datagrarr u normaIIP daiugram sent thru iunnequotvia regular IP unicast to receiv ng mcus router in receiv ng mcast router unencapsulates to get mcast datagram PIM Protocol Independent Multicas r of dependenf on any specific underlying unicasf III n roufing algorifhm works wifh all El Two differenf mulficasf disfribufion scenarios Dense Sparse El group members El nefworks wifh group densely packed in mem ers small wrf close proximify inferconnecfed nefworks El bandwidfh more D group members widely plenfiful dispersedquot El bandwidfh nof plenfiful of SparseDense P39 39 Dense Sparse El group membership by El no membership unfil roufers assumedunfil roufers explicifly join roufers explicifly prune III receiver driven El damdriven consfrucfion consfrucfion of mcasf on mcasf free e g RPF free e g cenferbased El bandwidfh and non El bandwidfh and nongroup grouproufer processing roufer processing profquiz conserva le PIM Dense Mode flood and prune RPF similar To DVMRP bu i El underlying unicasf profocol provides RPF info for incoming da agram El less complicafed less efficienf downsfream flood 139han DVMRP reduces reliance on underlying roufing algori139hm D has profocol mechanism for roufer To defecf if is a leafnode roufer PIM Sparse Mode El cenferbased approach El roufer sendsoil msg To rendezvous poinf RF 0 nterrnediate routers update state and El a er joining via RP roufer can swifch To sourcespecific free all data mutt cast 0 ncreased performance from rendezvous less concentration shorter put 5 rendezvous pow PIM Sparse Mode sender s El unicasf dafa To RP which disfribufes down RProofed free El RP can extend mcasf free upsfream To source I RP can send sfop msg if no aHac ed receivers all data mull cast from rendezvous rendezvous a 0quotquot o no one s llstenlng quot Chag rer 4 summary El 4 lInfr39oducfion El 4 5 Roufing algorifhms El 4 2 Virtual circuif and o in sin e dafagr am nszor39ks o Dlstunce Ve D 4 3 Whars inside a o H erurchicul routing roufzr39 El 4 6 Rouhn f u 4 4 IP Infernzf Wm Profocol 0 up 0 OSPF o Dutugrum format 0 IPv4 address ng 0 35quot Q ICMP El 4 7 Broadcasf and 0 IPv6 mulficasf r oufing Newark mmwm


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