Presentation on theme: "3 LAN Design Basics Computernetze 1 (CN1) Prof. Dr. Andreas Steffen"— Presentation transcript:
13 LAN Design Basics Computernetze 1 (CN1) Prof. Dr. Andreas Steffen Institute for Internet Technologies and Applications
2Lesestoff im Ethernet Buch Kapitel 6 Ethernet Internals, Seiten6.1 Längenbeschränkung im EthernetKapitel 8 Ethernet-Komponenten, Seiten8.1 Netzwerkkarten8.2 Repeater und Hubs8.3 Switches8.4 MedienwandlerSelbststudiumErarbeiten Sie als Vorbereitung für die Übung 4selbständig das Thema “Spanning Tree Protocol”mit Hilfe des Cisco Tutorials von Dan DiNicolo unddes Kapitels 4 des CN1 Foliensatzes.
3LAN and LAN DevicesLANs make it possible for businesses that use computer technology to efficiently share such items as files and printers and to make possible communications such as .LANs are designed to do the following:operate within a limited geographic area or buildingallow many users to access high-bandwidth mediaprovide full time connectivity to local servicesconnect physically adjacent devices
4The Beginning of LAN Design Initial idea: shared media LANBus structure; CSMA/CD was access methodCoax cable; transmission rate up to 10 Mbit/s, half-duplex
6RepeaterThe purpose of a repeater is to amplify and retime network signals at the bit level.Repeaters can be single-port "in" and single-port "out" devices, though more often now, they are stackable (modular), or multi-port repeaters, better known as hubs.Repeaters are classified as layer 1 devices, in the OSI model, because they act only on the bit level and look at no other information.
7Hub Used in 10BASE-T and 100BASE-T networks Is equivalent to a multi-port repeaterHubs come in three basic types:passive – no traffic and signal manipulation, used only to share the mediaactive – amplifies the incoming signalintelligent – (smart hub) same function as an active hub, additionally includes a controller chip and diagnostic capabilities
9BridgeThe purpose of a bridge is to filter traffic on a LAN, to keep local traffic local, yet allows connectivity to other parts (segments) of the LAN for traffic that has been directed there.The bridge makes its decisions based on MAC addresses.The bridge is a layer 2 device.
11Bridge: Flooding or Filtering (destination address) Error-free frame received on port xnoyesDestinationaddress found in forwardingdatabase?Forward frame to all ports (except port x)Is destination again on port x?noyesForward frameto port yDiscard frameFloodingFiltering1
12Bridge: Learning (source address) 1noyesSource addressfound in forwarding database?Add address with portand age value to theforwarding databaseUpdate portand age valueLearningendTypical address aging value: 300 s
13Learning / Flooding LAN 1 LAN 3 p1 p1 MAC A MAC F MAC B MAC G bridge 1 SA DAAFL2dataAFL2dataLAN 1LAN 3learn Aflood Fp1p1MAC AMAC FMAC BMAC Gbridge 1bridge 2MAC Cp2p2flood Flearn ALAN 2AFL2datatable of bridge 1table of bridge 2p1p2p1p2AA
14Learning / Filtering LAN 1 LAN 3 p1 p1 MAC A MAC F MAC B MAC G DA SAAL2dataLAN 1LAN 3learn Fp1p1MAC AMAC FMAC BMAC Gbridge 1bridge 2MAC Cp2p2filter ALAN 2table of bridge 1table of bridge 2p1p2p1p2AAF
15Learning / Flooding LAN 1 LAN 3 p1 p1 MAC A MAC F MAC B MAC G bridge 1 dataDA SAFGL2dataLAN 1LAN 3flood Gp1p1MAC AMAC FMAC BMAC Gbridge 1bridge 2MAC Cp2p2flood Glearn FLAN 2FGL2datatable of bridge 1table of bridge 2p1p2p1p2AAFF
16Learning / Forwarding LAN 1 LAN 3 p1 p1 MAC A MAC F MAC B MAC G dataDA SAGFL2dataLAN 1LAN 3forward Flearn Gp1p1MAC AMAC FMAC BMAC Gbridge 1bridge 2MAC Cp2p2learn Gforward FLAN 2GFL2datatable of bridge 1table of bridge 2p1p2p1p2AGGAFF
17Segmentation with Bridges Bridges split a LAN into several workgroups with smaller collision domains -> reduces whole LAN trafficOne "broadcast domain"half-duplex collision domains
18SwitchThe purpose of a switch is to concentrate connectivity, while guaranteeing bandwidth.It switches packets from incoming ports (interfaces) to outgoing ports, while providing each port with full bandwidth.The switch uses the MAC address to make its switching decisions. You might think of each port on a switch as a micro-bridge, which makes it a layer 2 device.
20Switch Forwarding Principles ** delays computed for 10 Mbit Ethernet
21Switch Forwarding Principles Early-Cutonly usable when finished learningforwards nearly all faulty framesCut-Throughreads destination and source addressforwards many faulty framesFast-Forward (Fragment Free)detects runts and collisionscan filter specific EthertypesStore-and-Forwarddetects CRC-errorscan do filtering based on higher-layer Information
22Switching Fabric cross-connect any two switch ports Port 1 Port 0
23Non-Blocking Switching Fabric 10 Gbps10 Gbps10 Gbps60 Gbps FabricBrief overview on basic concept of non-blocking switchesAnatomy of a switch, good or bad?Importance of buffers & queuesWill learn more about how this is implemented per Cisco platform in our product sessions10 GbpsBandwidth of Fabric > Ingress + Egress
24Blocking Switching Fabric 10 Gbps10 Gbps10 Gbps20 Gbps FabricHeart of a switch or router, must work or nothing will10 GbpsBandwidth of Fabric < Ingress + Egress
25Shared Memory Architecture General Purpose CPU(CISC older or RISC newer)CPUForwarding TablesBuffersQueuesPointersHeadersIOS Image/FilesPacket MemoryCPU MemorySystem BuffersProcessor QueuesData/Address/ Control BusesInterfaceInterfaceInterfaceInterfaceInterfaceInterfaceInterfacePhysical Media Interfaces(Fixed or Modular)
26Cross Bar Switch Architecture CPU Memory(DRAM)CPU(C) ForwardingTableMultiple conflict free pathsTypically higher bandwidthSignaling and scheduling is more complexCPUInterfaceCard(D) FTPacket MemoryTxRxCPUInterfaceCard(D) FTPacket MemoryTxRxCPUInterfaceCard(D) FTPacket MemoryTxCPUInterfaceCard(D) FTPacket MemoryRxCross Bar ASIC
27RouterThe purpose of a router is to examine incoming packets, choose the best path for them through the network, and then switch them to the proper port.Routers make their path selection decisions based on layer 3 information - the network addresses therefore they are considered layer 3 devices.Routers can connect different layer 2 tech-nologies, such as Ethernet, Token-ring, or FDDI.