1 / 27

Computernetze 1 (CN1)

Computernetze 1 (CN1). 3 LAN Design Basics. Prof. Dr. Andreas Steffen Institute for Internet Technologies and Applications. Lesestoff im Ethernet Buch. Kapitel 6 Ethernet Internals, Seiten 189-214 6.1 Längenbeschränkung im Ethernet

moya
Download Presentation

Computernetze 1 (CN1)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Computernetze 1 (CN1) 3 LAN Design Basics Prof. Dr. Andreas Steffen Institute forInternet Technologies and Applications

  2. Lesestoff im Ethernet Buch • Kapitel 6 Ethernet Internals, Seiten 189-214 6.1 Längenbeschränkungim Ethernet • Kapitel 8 Ethernet-Komponenten, Seiten 275-329 8.1 Netzwerkkarten 8.2 Repeater und Hubs 8.3 Switches 8.4 Medienwandler • Selbststudium ErarbeitenSiealsVorbereitungfür die Übung 4 selbständig das Thema “Spanning Tree Protocol” mitHilfe des Cisco Tutorials von Dan DiNicolo und des Kapitels 4 des CN1 Foliensatzes.

  3. LAN and LAN Devices • LANs 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 e-mail. • LANs are designed to do the following: • operate within a limited geographic area or building • allow many users to access high-bandwidth media • provide full time connectivity to local services • connect physically adjacent devices

  4. The Beginning of LAN Design • Initial idea: shared media LAN • Bus structure; CSMA/CD was access method • Coax cable; transmission rate up to 10 Mbit/s, half-duplex

  5. Repeater

  6. Repeater • The purpose of arepeater 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 1devices, in the OSI model, because they act only on the bit level and look at no other information.

  7. Hub • Used in 10BASE-T and 100BASE-T networks • Is equivalent to a multi-port repeater • Hubs come in three basic types: • passive – no traffic and signal manipulation, used only toshare the media • active – amplifies the incoming signal • intelligent – (smart hub) same function as an active hub,additionally includes a controller chip and diagnostic capabilities

  8. Ethernet StrukturierungCollision Domain

  9. Bridge • The purpose of abridgeis 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.

  10. MAC Layer Bridge (Transparent Bridge)

  11. Destination address found in forwarding database? no yes Forward frameto all ports (except port x) Is destination again on port x? no yes Forward frame to port y Discardframe Bridge: Flooding or Filtering (destination address) Error-free frame received on port x Flooding Filtering 1

  12. Source address found in forwardingdatabase? no yes Add address with port and age value to the forwarding database Update port and age value Bridge: Learning (source address) 1 Learning end Typical address aging value: 300 s

  13. SA DA data data A A F F L2 L2 data A F L2 Learning / Flooding LAN 1 LAN 3 flood F learn A p1 p1 MAC F MAC B MAC G MAC A bridge 1 bridge 2 MAC C p2 p2 flood F learn A LAN 2 table of bridge 1 table of bridge 2 p1 p2 p1 p2 A A

  14. DA SA L2 A F data filter A Learning / Filtering LAN 1 LAN 3 learn F p1 p1 MAC A MAC F MAC B MAC G bridge 1 bridge 2 MAC C p2 p2 LAN 2 table of bridge 1 table of bridge 2 p1 p2 p1 p2 A A F

  15. DA SA data F G L2 L2 G F data data F G L2 Learning / Flooding LAN 1 LAN 3 flood G p1 p1 MAC A MAC F MAC B MAC G bridge 1 bridge 2 MAC C p2 p2 flood G learn F LAN 2 table of bridge 1 table of bridge 2 p1 p2 p1 p2 A A F F

  16. DA SA L2 F G data data G F L2 L2 F G data Learning / Forwarding LAN 1 LAN 3 forward F learn G p1 p1 MAC A MAC F MAC B MAC G bridge 1 bridge 2 MAC C p2 p2 learn G forward F LAN 2 table of bridge 1 table of bridge 2 p1 p2 p1 p2 A G G A F F

  17. half-duplex collision domains Segmentation with Bridges • Bridges split a LAN into several workgroups with smaller collision domains -> reduces whole LAN traffic • One "broadcast domain"

  18. Switch • The 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.

  19. Ethernet Strukturierung Broadcast Domain (IP-Subnet)

  20. Switch Forwarding Principles * * delays computed for 10 Mbit Ethernet

  21. Early-Cut only usable when finished learning forwards nearly allfaulty frames Cut-Through reads destination andsource address forwards manyfaulty frames Fast-Forward (Fragment Free) detects runts and collisions can filter specific Ethertypes Store-and-Forward detects CRC-errors can do filtering based onhigher-layer Information Switch Forwarding Principles

  22. Switching Fabric Port 1 Port 2 Port 0 Port 3 cross-connect any two switch ports

  23. Non-Blocking Switching Fabric 10 Gbps 10 Gbps 10 Gbps 60 Gbps Fabric 10 Gbps Bandwidth of Fabric > Ingress + Egress

  24. Blocking Switching Fabric 10 Gbps 10 Gbps 10 Gbps 20 Gbps Fabric 10 Gbps Bandwidth of Fabric < Ingress + Egress

  25. CPU Interface Interface Interface Interface Interface Interface Interface Shared Memory Architecture General Purpose CPU (CISC older or RISC newer) Forwarding Tables Buffers Queues Pointers Headers IOS Image/Files Packet Memory CPU Memory System Buffers Processor Queues Data/Address/Control Buses Physical Media Interfaces (Fixed or Modular)

  26. CPU CPU CPU CPU CPU Packet Memory Packet Memory Packet Memory Packet Memory Interface Card Interface Card Interface Card Interface Card Tx Tx (D) FT (D) FT (D) FT (D) FT Rx Rx Cross Bar Switch Architecture CPU Memory (DRAM) (C) Forwarding Table • Multiple conflict free paths • Typically higher bandwidth • Signaling and schedulingis more complex Tx Rx Cross Bar ASIC

  27. Router • The 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 consideredlayer 3 devices. • Routers can connect different layer 2 tech-nologies, such as Ethernet, Token-ring, or FDDI.

More Related