I.S. 4123 Introduction to Telecommunication in Business

1. I.S. 4123Introduction to Telecommunication in Business Chapter 6 Network Hardware Components Dr. Jan Clark FALL, 2002

2. Repeaters • Provide both physical and electrical connections • Function - regenerate and propagate a signal • Extend distance covered • Receives signal from one cable segment, regenerates and transmits signal to one or more cable segments • Source of propagation delay in a network

3. Types of Hubs • Repeater hub - simplest connection • Switching hub - does not broadcast to all nodes • Bridging hub - can connect dissimilar networks • Stackable Repeater Hub - two or more LANS daisy chained together

4. Multislot Repeater Hub

5. Stackable Hubs

6. Repeater or Switch Hub?

7. Which is Better?

8. Bridge • Interconnects two or more LANs or LAN segments • Operate at Data Link Layer • Physical Layer transparent • Usually connect like networks, but can bridge unlike (e.g. Ethernet to Token Ring) - MAC Layer bridge • Rely upon Data Link Layer address - monitor messages and forward when appropriate

9. The LAN user is often unaware that a bridge exists. They do not experience performance degradation and are allowed access to any station on either network (within security reasons)

10. Broadcast Storms • Bridges pass broadcast frames from one network to another. • Broadcast storm occurs when several broadcasts are transmitted at the same time - can cause a network to crash or shut down.

11. Bridges are Store-and-Forward • They capture an entire frame before deciding whether to filter or forward the frame • CRC computed by bridge - if invalid, frame is dropped

12. A user on one LAN can address another LAN as though it were another node in their network. This is done without signing onto a communication device, dialing through a modem, or learning any new software commands or menus

13. "NEW" Bridge Definition

14. Bridge Standards • Transparent - Broadcast, multicast frames always forwarded. If not broadcast or multicast, creates "learned" address table when frames sent. • Source Routing (Token Ring only) - source address must know if destination address is on a different network. If so, provides routing info with message

15. When Does a Bridge Forward Data?

16. Source Routing Bridge

17. Which Would You Select for Interconnecting Networks - Bridge or Repeater?

18. Switches • Operate at the Data Link, Network, or Transport Layers (depending upon type of switch) • Connect two or more computers or network segments. • Ethernet switch - Layer 2 (Data Link) • Designed for shared media LANs • Permits multiple, simultaneous data transmission between different paths • Static switching

19. Switch Types • Store-and-forward switches copy the incoming packet into memory before processing the destination address - may hold for longer periods if destination is busy - performs CRC • Cut-through switches examine the destination of the incoming packet and immediately connect the port with the incoming message to the correct outgoing port (hardware based). No waiting, no error checking (great if not busy or error free, BUT…) • Hybrid - works either way. When error rates fall below a certain range, switch act as cut-through. If above the range, switch acts as store-and-forward.

20. Store-and-Forward Switch

21. Cut-Through Switch

22. Cut-Through Backplane Switch

23. How Can Collisions Occur on a Switched Ethernet Network?

24. Latency • Amount of time a frame spends inside a network device such as a bridge or a switch • The lower the latency, the faster a device processes a data frame • Network can time out with high latency • Which has higher latency - store-and-forward, or switch-through?