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Class Note for COSC 4377 at UH


Class Note for COSC 4377 at UH

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This 22 page Class Notes was uploaded by an elite notetaker on Friday February 6, 2015. The Class Notes belongs to a course at University of Houston taught by a professor in Fall. Since its upload, it has received 19 views.

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Date Created: 02/06/15
6056 4377 Spring 2001 Chapter 4b IP da ragram forma r IPpmmca versmn number header engm Md r We a engm bms mes semee 79 39 m we a 390 WWW a New fragmenmhan maxnumb2r mm m upper Imerne WWW d remmmng guys We 0 2r checksum faj fmgs 32 km murce I address 32 bwdeshnmmn I address upper awr pramca m dehverpaybad m owns 0 any E9 u23 mp dam mkewecw varmb e engm hgy af raumrs vypmw a TCP m WSW ur UDP segmem o ankamr m mm dmagram a IP Fm men ra hon amp Reassembl nemm mks We Mm max vransfer sue r argesv passxb e hnMevex frame 0 dxfferem w 39ypes dxfferem MTUS arge IPdmagmm dmded hemmed Wmquot n2 0 arm dmagram became severa damgrams remxemhv o reassemh2d anym nd desvmmmn o IPheader hwsused m denm arder rehved E fragmems o anmk Lew m fragmemm m m am mgedmagrau am a ma er damgrau 4401 COSC4377SpNng2001Chamer4b IP Fragmentation and Reassembly length ED fragflag offset 4000 gtlt 0 0 One large da tagram becomes several smaller datagrams length ED fragflag offset 21500 2X 1 0 length ID fragflag offset 21500 2X 1 1480 1040 gtlt length ED fragflag offset 0 2960 4 Network Layer 4173 ICMP Internet Control Message Protocol used by hos rs rou ters gateways To communication network level information 0 error reporting unreachable hos r network port protocol 0 echo requestreply used by Ping network layer quotabovequot IP 0 ICMP msgs carried in IP datagrams ICMP message Type code plus first 8 bytes of IP datagram causing error Tm Code description echo reply ping dest network unreachable dest host unreachable dest protocol unreachable dest port unreachable dest network unknown dest host unknown source quench congestion control not used echo request ping route advertisement router discovery TTL expired bad IP header bmmmmmmo OVQQM OO 10 11 12 00000 4 Network Layer 4174 4401 6056 4377 Spring 2001 Chapter 4b 4401 Roufing in The Infernef u The Global Internet consists of Autonomous Systems AS interconnected with each other 0 Stub A5 smciH curpurmiun o Munitonad A5 icirge curpurmiun nuiransii 0 Transit A5 pruvider a Twolevel routing o IntroAs aaninisiraiur is responsibie fur enuiee o InterA5 unique sianaara o anmk iowi om Internet AS Hierarchy InfraAS border exterior gateway routers InterAs interior gateway routers o anmk iowi M cosc 4377 Spring 2001 Chap rer39 4b 4401 InfraAS Rou ring CI Also known as In rer39ior39 Ga reway Pr o rocols IGP CI Mos r common IGPs 0 RIP Rou ring Infor ma rion Pr o rocol O OSPF Open Shor fes r Pa rh Fir s r O IGRP In rer39ior39 Ga reway Rou ring Pr o rocol Cisco propr 4 Nefwork Layer 4b7 RIP Rou rinq Information Pr39o rocol D Dis rance vec ror algor i rhm CI Included in BSDUNIX Dis rr ibu rion in 1982 Dis rance me rr ic of hops max 15 hops 0 Can you guess why D CI Dis rance vec ror s exchanged every 30 sec via Response Message also called advertisement CI Each adver risemen r r ou re ro up To 25 des rina rion ne rs 4 Nefwork Layer 4178 6056 4377 Spring 2001 Chapter 4b RIP Routing Information Profocol M unmwmwcmg mu m mx bn nybne M A m mm add A D B c has ation Network Next Router Numof Mps odest w A z y a z x a 7 x 1 Rouhng mm m I WWW M quotWm EmmmpanmWWW mng 5 3quot RIPmaSi l Oldmnrguhk avmush M 7 A 33 g g z 2 C Net 9 C 5 E F Net S C m a 1 me a r M3 E m a r was as Wham my 1w mm 1xe m mam mx lwn m bycmmdu mm and m M Dmmmm M 1m Wang and m o anork my mu 4401 6056 4377 Spring 2001 Chapter Ab 4401 MR 1 1mm mun mm ismszulanamaussy em o mme mu MR 13 3 mm mun mm m m Prevmu Wm 39 o anmk my m 6056 4377 Spring 2001 Chapter 4b 4401 RI Link Failure and Recovery If no advertisement heard after 180 sec gt neighborlink declared dead 0 routes via neighbor invalidated 0 new advertisements sent to neighbors o neighbors in turn send out new advertisements or tables changed 0 link failure info quickly propagates to entire net 0 poison reverse used to prevent pingpong loops infinite distance 16 hops o anmk Law gt13 RIP Table processing u m routing tables managed by application level process called routed daemon u advertisernents sent in UDP packets periodically repeated hnsponluo 1 n napanlunP v 39 v nemrkllP arm 33 netwurkllF one unv eon inn phyilul pnysnsi o anmk Law 6h cosc 4377 Spring 2001 Chap rer39 4b 4401 RIP Table example con rinued Rou rer girofeeeurocomfr Destination Flags Ref Use Interface 127001 0 1921682 19216825 U 2 13 faO 19355114 193551146 U 3 58503 1e0 1921683 19216835 U 2 25 qaaO 224000 193551146 U 3 0 1e0 default 19355114129 U6 0 143454 CI Thr ee a r rached class C ne rwor ks LANs CI Rou rer only knows r ou res ro a r rached LANs CI Defaul r r ou rer used To go upquot CI Rou re mul ricas r address 224000 CI Loopback in rer face for debugging 4 Nefwork Layer 4b15 Figux613710 Slow convergence 0 seconds 15 seconds n X 15 seconds Netn 1 4 Nefwork Layer 41716 cosc 4377 Spring 2001 Chapter 4b 4401 Figure 13711 Hop counts Netn 1 C C I A Total hop coum shouldbe less than 16 I 4 Network Layer 4b17 OSPF Open Shortest Path First CI quotopenquot publicly available CI Uses Link State algorithm 0 LS packet dissemination O Topology map at each node 0 Route computation using Dijkstra39s algorithm CI OSPF advertisement carries one entry per neighbor router CI Advertisements disseminated to entire AS via flooding 4 Network Layer 41718 case 4377 Spring 2001 cliapter 4b OSPF advanced features not in RIP a Security all OSPF messages autlienticated to prevent malicious intrusion TCP connections used a Multiple samecost patlis allowed only one path in m a For each link multiple cost metrics for different T05 29 satellite link cost set lovll39 for best effort high for real time u Integrated uni and multicast support 0 Mulllcasl OSPF MOSPF uses same lupulugy dam base as 0st D Hierarchical OSPF in large domains o minimum My Hierarchical OSPF boulldoly olisi backbone iouier area x 4 harder iouieis o minimum ma 4401 10 COSC 4377 Spring 2001 Chapter 4b Hierarchical OSPF CI Twolevel hierarchy local area backbone O Linkstate advertisements only in area 0 each nodes has detailed area topology only know direction shortest path to nets in other areas CI Area border routers summarizequotdistances to nets in own area advertise to other Area Border routers CI Backbone routers run OSPF routing limited to backbone CI Boundary routers connect to other A55 4 Network Layer 4b21 IGRP Interior Gateway Routing Protocol CI CISCO proprietary successor of RIP mid 805 CI Distance Vector like RIP CI several cost metrics delay bandwidth reliability load etc CI uses TCP to exchange routing updates CI Loopfree routing via Distributed Updating Alg DUAL based on diffused computation 4 Network Layer 4b22 4401 11 6056 4377 Spring 2001 Chapter 4b Infer A S rou ring o anmk low m Inferne r infer AS rou ring BGP u as BorderGateway Protocol fhudrz racto standard a pati Vukr protocol 0 similar to Distance Vcctor protocol 0 cacl Border satcway broadcast to neighbors peers unfiru patlr 1c scqucrcc of A55 to destination 0 Eg satcway X may send its pain to desl 2 Path XZ X 1 2 3Z o anmk low mo 4401 12 6056 4377 Spring 2001 Chapter 4b Inferne r infer AS rou ring BGP Suppasu gateway X send its path to peer gateway W a w may or may not select patli offered by x 0 cost policy don39t route via competitors AS loop prevention reasons a If Wselects patli advertised by x then Patli wz w Patti xz a Note X can control incoming traffic by controling it route advertisements to peers o eg don39t want to route traffic to z gt don39t advertise any routes to Z c anmk low ms mm is u can vezlar portal 1 A32 l 5 W lm in is Ase isi l w R as L l ASA A33 c anmk low mo 4401 13 COSC 4377 Spring 2001 Chap rer 4b Infernef inferAS routing BGP CI BGP messages exchanged using TCP CI BGP messages 0 OPEN opens TCP connec rion ro peer and au rhen rica res sender 0 UPDATE adver rises new pa rh or wi rhdraws old 0 KEEPALIVE keeps connec rion alive in absence of UPDATES also ACKs OPEN reques r o NOTIFICATION repor rs errors in previous msg also used To close connec rion 4 Nefwork Layer 4M7 Why differen r In rra and InterAS rou rinq Policy El In rerAS admin wan rs con rrol over how i rs Traffic rou red who rou res Through i rs ne r El InfraAS single admin so no policy decisions needed Scale El hierarchical rou ring saves rable size reduced upda re Traffic Performance CI InfraAS can focus on performance CI In rerAS policy may domina re over performance 4 Nefwork Layer 41728 4401 14 6056 4377 Spring 2001 Chapter Ab 4401 Rou rer Archi rec rure Overview Two key router fundions a run routing algorithmsprotocol 121 OSPF as u swifching daiagrams from incoming to outgoing link cutpu par switching fabric niiipui purl EH muiing processor o anmk Loni mo InELIT PorT FLI ncT ions new use Wink ioiiraiiiino W mum V Wquot mm IIIIIIII g uenmiaiien We quot Pnysiecii iciyer biirievei reeepiion Maw We Ducnmliud s ikhing egEinernei a given damgram eesi uukup ouipui pori see enepier 5 using rouiingicibie in inpui pori memury a gocii eompieie inpui pori prucessmg cii hne speed a queuing if damgrams arrive fusier incin furwardmg raie inio sWiien fabric o anmk Loni mu 15 6056 4377 Spring 2001 Chapter 4b In LIT Port LIeLIin u Fabric slowentiiat input ports combined gt queueing may occur at input queues u HeqdortneLine HOL blocking queued detagnun at from of queue prevents others in queue from moving forward u quuuuing duluy and lass due to input buffur awr aw swimh iabnc dam 133135 mile Don Eonlbmia at umc i 7 my anc ieq Fackd tan xm uunctcncu green Packet exvenences HOL blucki o anmk tow mi Three TXEes of switching fabrics W ling m memur crossbar 5 3 o anmk tow mo 4401 16 6056 4377 Spring 2001 Chapter 4b Switching Memorx rst generation routers u packet copied by system39s single cw u speed limited by memory bandwidth 2 bus crossings per datagram my Mural WP Pm Pm mama Modem routers u inpn port processor performs lockup copy into memory a Cisco Catalyst 3500 WWW m Switching Via Bus u datagram from input port memory to output port memory via a shared bus u bus contention switching speed limited by bus bandwidth D 1 Gbps bus Cisco 1900 sufficient speed for access and enterprise routers not regional or backbone o anmk low but 4401 17 6056 4377 Spring 2001 Chapter 4b Switching Via Ari Interconnection Network D overcome bus bandwidth limitations u Banyan networks other interconnection nets initially developed to connect processors in multiprocessor u Advanced design fragmenting datagram into fixed length cells switcli cells through the fabric D Cisco 12000 switches Gbps through the interconnection network o rumor Law gt35 Output Ports dale ian processing ipiaiooal decapsuiallurl line leiminalwu u suffering required when datagrams arrive from fabric faster than the transmission rate u scheduling discipline cliooses among queued datagrams for transmission o rumor Law No 4401 18 cosc 4377 Spring 2001 Chapter 4b Output port Queueing E E 334 wEkgl odlpni Poll Conleni lon One Pockel ol Time I limo lalsi Swllcll Fubl D buffering Mien arrival rate via switch exceeeds ouput line speed a queueingmelay and loss due to nutputpnr39t bu ffer overflow a Namwk layr mi IPv6 ll Initial motivation 32bit address space completely allocated by 2008 El Additional motivation O header format helps speed processingforwarding o header changes to facilitate Q05 0 new anycastquot address route to quotbestquot of several replicated servers ll IPv6 datagram format 0 fixedlength 40 byte header 0 no fragmentation allowed a Namwk layr em 4401 19 6056 4377 Spring 2001 Chapter 4b 4401 IPv6 Header Cont Privrify identify priority among datagrams in flow FlamLabel identify datagrams in same flow concept of flowquot not well defined Nuxf header identify upper layer protocol for data o anork Law om Other Changes from IPv4 lI Checksumi removed entirely To reduce processing Time at each hop lI OPTans allowed buf oufside of header indicafed by Next Headerquot field El ICMPl new version of ICMP 0 additional message types eg quotPacket Too Big 0 multicast group management functions o anork Law ohm 6056 4377 Spring 2001 Chapter 4b 4401 Transifion From IPv4 To IPv6 El Nof all roufzr39s can be upgraded simulfanzous o no flag daysquot 0 How will the network operatewith mixed IPv4 and IPv6 router39s El Two proposed approaches 0 DunStack some router39s with dqu stuck v6 v4 can translate between formats 0 Tunnellny39IPv6 curried es payload n IPv4 dutugrum among IPv4 router39s o anmk Law mu Dual S rack Aggroach Wm M m M M M quotx r quot rquot rquot r quot39 rquot A BJ QuHD x b 4 4 rm x Sawm39A Saulcc39A Haw 22 Scum A Day I pm Saute A Day r Des r duh dam my dam A oB EraC mar nor HM um um M o anmk Law an COSC 4377 Spring 2001 Chap rer 4b 4401 Tunneling mm wew m m 7 Uta MN m l I IPv6 inside IPv4 Minere needed M m m M M m H r r x r rquot xA Br tCJ kDrx xEJf E 4 4 4 M y s a Source A Dcsr E Des E Dequot F How X How X A game A dam D45 F Dem f dam me m duh W M M Emc awe W M mow nlwg snmpw nhng M M 4 Nefwurk Layer 4142


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