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Steffen/Stettler, 03.10.2013, 3-LAN_Design_Basics.ppt 1 Computernetze 1 (CN1) 3 LAN Design Basics Prof. Dr. Andreas Steffen Institute for Internet Technologies.

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Presentation on theme: "Steffen/Stettler, 03.10.2013, 3-LAN_Design_Basics.ppt 1 Computernetze 1 (CN1) 3 LAN Design Basics Prof. Dr. Andreas Steffen Institute for Internet Technologies."— Presentation transcript:

1 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 1 Computernetze 1 (CN1) 3 LAN Design Basics Prof. Dr. Andreas Steffen Institute for Internet Technologies and Applications

2 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 2 Lesestoff im Ethernet Buch Kapitel 6 Ethernet Internals, Seiten Längenbeschränkung im Ethernet Kapitel 8 Ethernet-Komponenten, Seiten Netzwerkkarten 8.2 Repeater und Hubs 8.3 Switches 8.4 Medienwandler Selbststudium Erarbeiten Sie als Vorbereitung für die Übung 4 selbständig das Thema “Spanning Tree Protocol” mit Hilfe des Cisco Tutorials von Dan DiNicolo und des Kapitels 4 des CN1 Foliensatzes.

3 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 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 . 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 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 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 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 5 Repeater

6 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 6 Repeater The 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.

7 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 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 to share 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 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 8 Ethernet Strukturierung Collision Domain

9 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 9 Bridge The 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.

10 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 10 MAC Layer Bridge (Transparent Bridge)

11 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 11 Bridge: Flooding or Filtering (destination address) Error-free frame received on port x 1 FloodingFiltering Discard frame Forward frame to port y noyes Destination address found in forwarding database? Is destination again on port x? noyes Forward frame to all ports (except port x)

12 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 12 Bridge: Learning (source address) Learning 1 end Add address with port and age value to the forwarding database noyes Source address found in forwarding database? Update port and age value Typical address aging value: 300 s

13 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 13 A A Learning / Flooding table of bridge 1table of bridge 2 p1p2 SA DA AFL2data MAC A MAC F MAC C MAC BMAC G bridge 1 bridge 2 p1 p2 p1 p2 LAN 1 LAN 2 LAN 3 learn A flood F learn A flood F AFL2dataAFL2data p1p2

14 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 14 F Learning / Filtering F DA SA AL2data MAC F MAC C MAC BMAC G bridge 1 bridge 2 p1 p2 p1 p2 LAN 1 LAN 2 LAN 3 learn F filter A MAC A A table of bridge 1 p1p2 A table of bridge 2 p1p2

15 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 15 F Learning / Flooding MAC F MAC C MAC BMAC G bridge 1 bridge 2 p1 p2 p1 p2 LAN 1 LAN 2 LAN 3 flood G FGL2data DA SA learn F flood G MAC A F A table of bridge 1 p1p2 A table of bridge 2 p1p2 FGL2dataFGL2data

16 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 16 GG Learning / Forwarding MAC F MAC C MAC BMAC G bridge 1 bridge 2 p1 p2 p1 p2 LAN 1 LAN 2 LAN 3 learn G forward F learn G forward F GFL2data DA SA MAC A F A table of bridge 1 p1p2 F A table of bridge 2 p1p2 GFL2dataGFL2data

17 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 17 Bridges split a LAN into several workgroups with smaller collision domains-> reduces whole LAN traffic One "broadcast domain" half-duplex collision domains Segmentation with Bridges

18 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 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 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 19 Ethernet Strukturierung Broadcast Domain (IP-Subnet)

20 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 20 Switch Forwarding Principles * delays computed for 10 Mbit Ethernet *

21 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 21 Switch Forwarding Principles Early-Cut only usable when finished learning forwards nearly all faulty frames Cut-Through reads destination and source address forwards many faulty frames Fast-Forward (Fragment Free) detects runts and collisions can filter specific Ethertypes Store-and-Forward detects CRC-errors can do filtering based on higher-layer Information

22 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 22 Switching Fabric Port 0 Port 3 Port 2 Port 1 cross-connect any two switch ports

23 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 23 Non-Blocking Switching Fabric 10 Gbps 60 Gbps Fabric Bandwidth of Fabric > Ingress + Egress

24 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 24 Blocking Switching Fabric 10 Gbps 20 Gbps Fabric Bandwidth of Fabric < Ingress + Egress

25 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 25 CPU Memory Data/Address/ Control Buses Packet Memory Buffers Queues Pointers Headers IOS Image/Files System Buffers Forwarding Tables Processor Queues Interface CPU General Purpose CPU (CISC older or RISC newer) Physical Media Interfaces (Fixed or Modular) Shared Memory Architecture Interface

26 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 26 Tx Rx Tx Rx Tx Rx CPU Memory (DRAM) (C) Forwarding Table CPU Interface Card (D) FT Packet Memory CPU Interface Card (D) FT Packet Memory CPU Interface Card (D) FT Packet Memory CPU Interface Card (D) FT Packet Memory Cross Bar ASIC Multiple conflict free paths Typically higher bandwidth Signaling and scheduling is more complex Cross Bar Switch Architecture

27 Steffen/Stettler, , 3-LAN_Design_Basics.ppt 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 considered layer 3 devices. Routers can connect different layer 2 tech- nologies, such as Ethernet, Token-ring, or FDDI.


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