9/4/2015 1R. Smith - University of St Thomas - Minnesota CISC Class Today RecapRecap Project TopicsProject Topics Quality of ServiceQuality of Service LAN TechnologyLAN Technology

Recap GradingGrading ExamExam Recap on ProxiesRecap on Proxies Internet PhonesInternet Phones RoutingRouting –Tell your neighbors everything –Tell everyone about your neighbors 9/4/2015 2R. Smith - University of St Thomas - Minnesota

9/4/2015 3R. Smith - University of St Thomas - Minnesota Quality of Service Elastic vs Inelastic servicesElastic vs Inelastic services –A familiar concept, different terms –Possibly elastic/inelastic properties ThroughputThroughput DelayDelay Delay variationDelay variation Packet lossPacket loss Differentiated Services (DS)Differentiated Services (DS) –Uses a field in IP packet to identify different handling needs –Can simply be “priority” Send it ahead of lower priority trafficSend it ahead of lower priority traffic Discard other packets before this one if space is tightDiscard other packets before this one if space is tight –Routers can provide “guaranteed service” for selected DS settings (at UST, CLIC service has a small guaranteed bandwidth)

9/4/2015 4R. Smith - University of St Thomas - Minnesota LAN concepts, Chapter 9 Types of LAN applicationsTypes of LAN applications “Guided” Transmission Media“Guided” Transmission Media –LAN Technology – wired, copper –LAN Technology – optical LAN ProtocolsLAN Protocols

9/4/2015 5R. Smith - University of St Thomas - Minnesota Types of LAN applications PC LANsPC LANs –Whatever is cheapest, requiring minimal hardware –Low cost wire Higher level office LANsHigher level office LANs –Higher speed to support movement of large files –Graphics applications, CAD – moving large files Back end/Storage Area NetworksBack end/Storage Area Networks –Connect CPUs with large storage systems –High data rate, high speed i/f, distributed access –Short distances, limited number of devices Backbone LANsBackbone LANs –Connects other LANs together –Reliability, capacity, cost

9/4/2015 6R. Smith - University of St Thomas - Minnesota Tiered architectures Tier 1 – Back end LANTier 1 – Back end LAN Tier 2 – Backbone LANTier 2 – Backbone LAN Tier 3- Office LANsTier 3- Office LANs Generally reflected in LAN geographyGenerally reflected in LAN geography

9/4/2015 7R. Smith - University of St Thomas - Minnesota LAN Technology – wired, copper Performance ConsiderationsPerformance Considerations –Bandwidth –Transmission impairments (attenuation) –Interference (noise from nearby sources, wires) –Number of receivers (attenuation += attachments) UTP – Unshielded Twisted PairUTP – Unshielded Twisted Pair –“Category 5” – what we still often use 100baseT –Cat 6 is taking over (supports gigibit rates) STP – Shielded Twisted PairSTP – Shielded Twisted Pair –Better properties but much more expensive Coaxial Cable – “Coax”Coaxial Cable – “Coax” –Like cable TV cable – great properties, but expensive

9/4/2015 8R. Smith - University of St Thomas - Minnesota LAN Technology – optical Performance CharacteristicsPerformance Characteristics –Greater capacity –Smaller size, lighter weight –Lower attenuation –Electromagnetic isolation Transmission rates HzTransmission rates Hz (note section on Structured Cabling in Ch. 9)(note section on Structured Cabling in Ch. 9)

9/4/2015 9R. Smith - University of St Thomas - Minnesota LAN Protocol Link Layer FormatLink Layer Format –Packet type/MAC control –MAC addresses –Data –CRC ServicesServices –Unacknowledged connectionless –Connection mode service –Acknowledged connectionless

9/4/ R. Smith - University of St Thomas - Minnesota Ethernet The first wildly popular LANThe first wildly popular LAN AlohanetAlohanet –Radio broadcast between islands –Unreliable packets, used higher level end-to-end retransmission –Carrier sense multiple access (CSMA) First EthernetFirst Ethernet –Supported Alto – first PC with modern GUI –“Radio broadcast” on a coaxial cable –CSMA + collision detection: CSMA/CD

9/4/ R. Smith - University of St Thomas - Minnesota Modern Ethernet Based on twisted pair wiresBased on twisted pair wires –10baseT – early model, 10Mb/sec –100baseT – 1990s, 100Mb/sec –1000baseT – latest, Gigabit/sec Wiring through special equipmentWiring through special equipment –Specially designed plugs, sockets –Special equipment for wiring plugs, sockets Connecting devicesConnecting devices –Hubs – broadcast all packets to all connected devices –Switches – make connections to pairs of devices –Crossovers – wiring is directional: can’t connect 2 computers directly together with older wiring (OK with Gigabit: autosense)

Network Address Translation (“NAT”) A strategy to connect more machines to the Internet with a limited number of V4 addresses

Working Routing Problems Given a network layoutGiven a network layout –Wires, switches, hubs, routers Tell which devices can reach whichTell which devices can reach which

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