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chapter 5 devices for connecting networks n.
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  1. Chapter 5 Devices for Connecting Networks Hands-on Networking Fundamentals

  2. Uses of LAN transmission equipment • Connecting devices on a single network • Creating and linking multiple networks or subnetworks • Setting up some enterprise networks • Connecting devices that will be discussed • repeaters, • MAUs, • hubs, • bridges, • routers • switches, • gateways LAN Transmission Devices

  3. OSI Physical Layer device • Connects two or more cable segments • Retransmits incoming signal to all other segments • Cable segment is run within IEEE specifications • Performs four Physical layer functions • Filter out signal disturbance caused by EMI and RFI • Amplify and reshape incoming signal • Retime the signal (in Ethernet applications) • Reproduce the signal on all cable runs Repeater

  4. Uses of repeaters • Extend cable segments • Increase number of nodes beyond segment • Sense network problem and shut down segment • Connect to components in other network devices • Amplify and retime signals • Connect segments using different media • Increase communication distance of T-carrier lines • Collision domain: segments where collisions occur • Caused by two or more nodes transmitting at once Repeater (continued)

  5. Two kinds of repeaters • Class I: only one can be used between two end nodes • Class II: one or two between two end nodes Repeater (continued)

  6. Central network device connecting nodes in star • Functions of a hub • Centrally connect multiple nodes into one network • Consolidate the network backbone • Provide connections for several different media types Hub

  7. Workgroup hubs: form participants into workgroup • May be connected to another device (switch, router) • Are stackable (stacked on top of each other) • Intelligent (managed) hub • Gathers information about network performance • Enables remote shut down of port or entire hub • Hubs can partition network segments (like repeaters) Hub (continued)

  8. Network device connecting LAN segments • Functions of a bridge • Extend LAN when maximum connection limit reached • Example: the 30-node limit on an Ethernet bus • Extend a LAN beyond the length limit • Example: beyond 185 meters for a Thinnet segment • Segment LANs to reduce data traffic bottlenecks • Prevent unauthorized access to a LAN • Examine frame's physical destination address • Occurs at MAC sub layer of OSI Data Link layer Bridge

  9. Three frame scenarios • Destination on same segment as source • Bridge drops frame, since no forwarding needed • Destination on another segment known to bridge • Bridge transmits frame to the known segment only • Destination segment not known to bridge • Bridge transmits frame to all segments but source • Protocol independent • Look only at MAC address • May forward different protocols on same network Bridge (continued)

  10. Translational bridge • Converts frame to new access method and media type • Example: from Token Ring to Ethernet • Discards addressing information not used in Ethernet • Three primary bridge functions • Learning: learn network topology and device addresses • Information stored in a bridging table • Filtering: do not flood certain frames, discard others • Enables bridge to used for security purposes • Forwarding: transmit frames to destination • Based on data built-in to bridging table Bridge (continued)

  11. Multiport bridges tie several LANs into one network • Advantages of bridge over repeaters and hubs • Ability to segment network traffic • May serve as a firewall to keep intruders out • Two types of bridges • Local: directly connects two LANs in close proximity • Also used to segment traffic to reduce bottlenecks • Remote: join distant networks • Used to join networks in different cities or states • Wireless bridges: a subclass of local bridges • Link to nodes equipped with wireless NIC (WNIC) Bridge (continued)

  12. Dual purpose • To provide bridging capacity • To increase bandwidth • Bridge-like characteristics of switch • Operates at Data Link MAC sub layer • Uses table information to filter and forward traffic Switch

  13. Reduces collisions and improves bandwidth on Ethernet • Example: hub with eight 100 Mbps segments • Has capacity of 8 x 100 (800) Mbps • Managed switches have intelligence options • Options similar to those of managed hub Switch (continued)

  14. Multistation access unit (MAU or MSAU) • Central hub on a token ring network • May have intelligence built-in to detect problems • Smart multistation access unit (SMAU) • Tasks performed by MAU • Connect nodes in a logical ring upon a physical star • Move the token and frames around the ring • Amplify data signals • Expand token ring network by daisy-chain connections • Provide for orderly movement of data • Shut down ports to malfunctioning nodes Multistation Access Unit

  15. Functions at OSI Physical and Data Link layers • Can interconnect in daisy-chain fashion • Ring in (RI), ring out (RO) ports linked with patch cable • Control Access Unit (CAU): stacks multiple MAUs into one logical unit Multistation Access Unit (continued)

  16. Source-route bridges used in token rings • Perform routing at the OSI Networklayer • Store and forward packets indicated by specified route • Process of sending a packet • Explorer packet travels to destination, returns to source • Path taken by real packet determined by three factors • Route taken by explorer packet received back • Minimum number of hops to destination • Path that can enable the largest packet size • Hop: packet transfer between networks • Route selected based on fewest hops (shortest path) Token Ring Source-Route Bridge

  17. Software or hardware interface • Enables two networked or software systems to link • Functions of a gateway • Convert common protocols to specialized type • Convert message formats from one format to another • Translate different addressing schemes • Link a host computer to a LAN • Provide terminal emulation for connections to host • Direct electronic mail to the right network destination • Connect networks with different architectures • Can function at any OSI layer Gateway

  18. Table 5 – 2: See Textbook for Details