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Computer Networks

by: Jacey Olson
Jacey Olson

GPA 3.69


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Class Notes
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This 6 page Class Notes was uploaded by Jacey Olson on Thursday October 22, 2015. The Class Notes belongs to CSE 123 at University of California - San Diego taught by Staff in Fall. Since its upload, it has received 40 views. For similar materials see /class/226791/cse-123-university-of-california-san-diego in Computer Science and Engineering at University of California - San Diego.

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Date Created: 10/22/15
Final CSE 122 Check Studentlink to be sure but believe that its m 39 39 Graduate Networklng June 11 3 6pm In thIs room Closed book Spring 2003 You can bring on 85x11 sheet of paper and you Last Lemme potpourri can do just about anything to that piece of paper you want ie write on both sides print on it etc You can t tape yourtektbook to the sheet of oaperthough Oryourtaptop Same style as midterm Fw You Stefan Savage may be asked questtons about project 4 m min on wow Review session Stuff we ll look at today Monday June 9 quot 400530pm in APampM 4301 Skim wi also be available on the 10 h from 2330 v M normal class hours PSec Or by apporntment Actwe Networks SensorNetworks A bit more detail Network measurement Router destng chnn mam wow YlalxxhNuWemumxomaxmu 4znn chnn mam MW Security at lowest layer IP Security Association SA binds AH and ESP Framework for security The assoctatton oennes a set ofsecurtty sentoes between Setect dtfferent encryptton atgonthms securtty orotocots e d p 5 WW New Setect secunty servrces e g tntegnty authenttcatton etc 39 S mp ex 0W demed 0 9 9 d rect o Setect granutanty e g connectton aH enoeoomt ows N99d M0 form d red om 0 5 comem Two parts NegotIatIon uthenttcatton Header AH tntemet Securtty Assoctatton and Key Management tSAkMP Access controt tntegrtty authenttcatton anttereptay ngectzdureg d Encapsutatmg Secunty Paytoad ESP on enttahtytn addttton to above ehes upon an encryptton atgonthm formats to estabhsh negottate modtfy securtty assoctattons Again a framework tntemetkey Exchange sbecrnc orotocot for ekchangmg keys 4znn chnn mam wow YlalxxhNuWemumxomaxmu 4znn chnn mam MW I PV6 4 m cxinn mt MW Originally motivated by crisis in IP address space 2 bits not enough if everything gets an iP address Subnetting and GDP heiped aiot but not a ioi39igcterm soiution mobile p ones Solution Increase the size of IP addresses Originaiiyto 64 then to in bits Requires changesto P header If we re going to change the header might as well change other aspects of IP Rule of thumb IPv6 IPv4 big addresses IPSEC Mobile IP DHCP ARP improvements to these IPv6 2 4 m cxinn mt MW IP addresses are 128 bits Unicast muiticast iocai etc i234 ABCD i234 ABCD i234 ABCD i234 ABCD Registry proyider subscriber subnetworx interface interface iD used as lowest 6 bytes Simplified headers 40 bytes 20 for iPwi Use header extensions foroptions Autocon guration iviuitipie addresses per host iii ikciocai address FlowLabel priority security mobility IPv6 and IPv4 Interoperabl Ity 4 m cxinn mt MW Dualstack operation iPys nodes that support both Pwi and PW Tunneling iPys paciltets encapsuiated within iPwi paciltets Endpoints speailt Pys but use iPwi packet to use standard internet routing Easy mapping if iPys embeds iPwi address otherwise need to configure a table Active Networks Problem How can we change the network without replacing the network Routing algorithms muiticast queueing discipiines WFO obiiity measurement etc Approach Active Networks Maxe routers programmable Example Packets carry programs or pointers to programsi Programs executed on arrival of paciltets Need iatforrn execution enyironment resource controi security stora e etc 7 essentially a whole new os Many different incarnations some srn aii testbeds Controversial security management oyerhead A point in the design space of i39ioi39iJCiiei39ilservei39 modeis 4o cxinn mum MW m aNbiiIemelhlxaniaxmx Sensor Networks 4 m cxinn mt MW Scena o reds orthousands of iowcpowered wireiess sensors distributed haphazardiy over an area Applications to environmental monitoring obiecttracxing etc Research problems How to communicate information through networilt eficientiy and with ioweroyeraii power applicationspeci c muitihop How to locate nodes and provide time sync among them How to write an application forsuch a networilt Network Measurement 4 m cxinn mt em The Internet is an artifact of sufficient complexity that we don t understand 39t Difficuitto measure many things directiy egt inference easure all or it sampling difficult A whole communit focused on these problems Pacxet characteristics application usage dynamic behayioror existing protocols Path characteristics delay ioss rategueuing bandwidth endetueend ys hopebyehup Networxtopoiogy connections between routers between iSF39s graph analysis or internet topologies Big challenge no support formeasurement For example How to measure oneway network path measurements eg packet loss rate Cnttcai fornetwork performance anaiysts Requrres measurement from both endoornts Remote hosts are indifferent to problem Unrealistic to debtoy new sottware Remote nosts may biock measurements 4m em mum MW Hamhwuwamumxamaxmu Key idea Exploit services needed by remote host Web Ermati news rue transfer etc AH use Transmrssbn ControProtocoTCP Rehabie meorder data transrerorotocot Exploit standard protocol behavior TCP nas ncn specmcatron Can be teyeraged to perform measurements 4m cxinn mum MW mm aNuWamumxamaxmx Simple example Deducing oneway loss rate Send TCP data packets to remote host What we know Number of data packets sent Number of acknowiedgm ents receryed What we need to know How many data packets were received Extract from ACKS TCP rs a rehabte orotocot How many acknowiedgm ents were sent Arrange tnat one ACK sent roreacn data packet 4m em mum MW Yumhwuwamumxamaxmu How TCP reveals packet loss Data packets ordered by sequence s ACK packets specify next seq expected E Nothing lost Data lost ACK lost 1 1 Loss deduction example Measurement Loss deduction i taSent 3 dataLost 1 ackReceived 1 dataReceivedackSent 2 Lossdm1 dataReceiveddataSent 33 Lossm1 ackReceivedackSent 50 4m em mum MW Hamhwuwamumxamaxmu Experimental finding Packet loss is highly asymmetric 25 Popular Web servers Tu Web seryer Cumulative fraction FrumWeb seryer D DDS D1 D15 D2 D25 D3 4m cmm Lessrmum What s in a router how to make a very fast router Physical components 0 One or more input interfaces that receive packets 0 One or more output interfaces that transmit packets o A chassis box power to hold it all Functions 0 Forward packets 0 Drop packets congestion security Q08 0 Delay packets Q08 0 Transform packets Encapsulation Tunneling June 3 2003 CSE 222A Lecture 16 Potpourri Thanks to Nick Weaver for some slides What a router does the normal case Receive incoming packet from link input interface Lookup packet destination in forwarding table 0 destination output ports Validate checksum decrement ttl update checksum Buffer packet in input queue Send packet to output interface interfaces Mcast Buffer packet in output queue Send packet to output interface link June 3 2003 CSE 222A Lecture 16 Potpourri Thanks 0 Nick Weaver for some s ides What a router looks like Cisco 2500 Linksys DEFSR81 19 8 Capacity lt10Mbps Capacity lt1 OMbps June 3 2003 CSE 222A Lecture 16 Potpourri Thanks to Nick Weaver for some slides What a router looks like 2 Cisco GSR 12416 Juniper M160 19 Capacity 39 80Gbs 2 Power 26kW 6ft June 3 2m uaE 222A Lecture 16 Potpourri Thanks 0 Nick Weaver for some s ides What a router looks like 3 Pluris Teraplex 20 w7 Racks 7 Capacity gt 1 Tbs Power 45kW 250 homes 1 room June 3 2003 CSE 222A Lecture 16 Potpourri Thanks to Nick Weaver for some slides Highperformance routers Geared to core and distribution service needs 0 Requirements high speed amp high density Why do we care 0 Moore s Law slowerthan link speed growth and BW demand OC480 2 SGbps now 128nspacket OC192C 1OGbps in deployment 33nspacket OC7680 4OGbps 20023 8nspacket Need high densitylow powerto manage POP complexity 20100k amp 24OOW per port 50 ports frequently for internal connectivity DWDM can help with the former but requires more interfaces June 3 2003 CSE 222A Lecture 16 Potpourri Thanks 0 Nick Weaver for some s ides Functional architecture Control Plane mplex 39 Percontrol action Romlng May be slow Table Forwarding f Table 3 Data plane g Sim Perpacket Must be fast mm mm m momma Packet classi cation Forwarding Longest pre x match of destlrlatlorl agalrlst torwardlrlg table Returns output ports Nextrhop MAC header tuple George Will talk about Hi5 rlexttlrne QoS tagging Certalrl tramc tagged Wlth Higherprlorliy Per ow src lo src ports dst lo dst pori ore source ordest prefix perprotocol Napster etc Firewall rules Block access to TOP packets With dst port l 80 Mum chnn mums Wm mm aNthmtlhlxamtxmx Interconnect architecture Input amp output connected via switch fabric lnput output Kinds of switch fabric Bus Crossbar SharedMemory How to deal with transient contention unammcomblnatlon cmm mums vacuum mmnmwmumxmuluu First Generation Routers 5Ingle CPU and s em Al classlrlcatlorl by mam cPu mu mm min may ls Fawwm Second Generation Routers Table Shared auslsl mummy cxznn mum s mum Vmmmummmuu Th rd Generat on Routers swltcll Fabrlc ed mmnnest Fu forwarding table m line card leed cells Mimi mu mm min may ls Fawwm Output queuing Input queuing Output interfaces buffer packets Inputinterfaces buffer Input Output packets Pro Pro Strnpte atgontnrns Stngte congestton potnt Stngte congestton potnt St Con mpte to destgn atgontnrns Con N tnputs may send to tne same output Requtres speedup ofN gtgt Utth hmtted to 2 2A pmm mun ts vapsustt mm s m Wemumxame xtau t a mu pmm mun ts vapsustt Headof Line Blocking Virtual Output Queues come y 39 4 mm m mun ts vapsustt IQ V rtual Output Queuing Switch schedul ng Inputinterfaces buffer packets in peroutput virtual queues Problem Input output Matcn tnputs and outputs Resotve contenttons O Sotves btocktng proptern Do tt tn constant ttrne Many algorithms for uniform traffic assumption More resources Demon E g TDM Maxtmum stze ptparttte ma 0 mptex arptter Approxtmate answers e 9 SH submaxtmat matcn stttt ttrntted bytnputoutput Recentresu39 Dai 9 3 2000 contentton seneduter 11e Maxtmat stze matcnt g speedup oftwo guarantees 100 uttttzatton for most tramp assurn pttons pmm mun ts vapsustt mm s m Wemumxame xtau t a mu pmm mun ts vapsustt


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