1. Larger Site Networks Chapter 8 Copyright 2001 Prentice-Hall

2. Orientation Chapters 6 & 7 –Single-hub or Single- Switch Ethernet LANs Chapter 8 –Multi-hub Ethernet LANs –Ethernet Switched Site Networks –Congestion, Latency, and solutions –ATM LANs –Routers, Layer 3, and Layer 4 Switches

3. Multi-hub LANs Multiple hubs Multiple hubs in 10Base-T Multiple hubs in 100Base-TX Multiple hubs in Gigabit Ethernet

4. Hubs Chapter 7 –Single-hub or single-switch LAN –200 meter maximum distance span between farthest two stations with UTP 100 m X Y 200 m

5. Hubs Chapter 8 –Multiple-hub LANs –To increase maximum distance span 100 m

6. Two Hubs in 802.3 10Base-T Station X transmits bit to Hub A –Hub operates at the physical layer (one bit at a time) 1 A B X Y

7. Two Hubs in 802.3 10Base-T 2. Hub A broadcasts bit out all ports 2 A B X Y

8. Two Hubs in 802.3 10Base-T 3. Uplink Port sends bit to Hub B –Uplink ports are marked by an “X” 3 A B X Y Uplink Port

9. Two Hubs in 802.3 10Base-T 4. Hub B broadcasts bit to all attached stations, including Y Note that all stations on both hubs receive the bit broadcast almost simultaneously 4 A B X Y

10. Multiple Hubs in 10Base-T Farthest stations in 10Base-T can be five segments (500 meters apart) –100 meters per segment –Separated by four hubs 100m 500m, 4 hubs 10Base-T hubs

11. Multiple Hubs in 10Base-T No loops allowed –Only one possible path between any two stations No Loops A B C 1 2 3 4 5 6 AB=1,2,3,4,5 AC=1,2,3,4,6 BC=5,4,6 First two have too many hubs No!

12. Multiple Hubs in 10Base-T No loops allowed –If hub or link fails, network is divided No Loops A B C 1 2 3 4 5 6 No!

13. Multiple Hubs in 10Base-T Practical Limit in 10Base-T is Number of Stations –Degradation of service beyond 100 stations –Unacceptable service beyond 200 stations –Maximum possible span normally embraces more than 200 stations –In 10Base-T, the number of stations is the real limit to distance spans –Still, it is possible to have a LAN with more than a 200 meter maximum span

14. Multiple Hubs in 100Base-TX Limit of Two Hubs in 100Base-TX –Must be within a few meters of each other –Maximum span is 200 meters –Shorter maximum span than 10Base-T 100m 2 Collocated Hubs 100Base-TX Hubs ~200 m

15. Multiple Hubs with 1000Base-T Limit of One Hub in Gigabit Ethernet –Maximum span is 200 meters –Same limit as 100Base-TX –Shorter maximum span than 10Base-T 100m

16. Multiple Hubs in Perspective 10Base-T Hubs –500 meter maximum distance span with UTP –Farther with some optical fiber links –However 10Base-T is limited by the number of stations it can support –So the maximum practical distance span is really much smaller 100Base-TX Hubs and Gigabit Ethernet Hubs –200 meter maximum distance span

17. Switched Ethernet Site Networks No Maximum Distance Spans Hierarchies and Single Possible Paths High Speeds and Low Prices

18. Ethernet Switched Networks There are Distance Limits Between Pairs of Switches –100 meters with UTP –Longer with optical fiber Maximum Separation 100 m with UTP Longer with optical fiber Ethernet Switch

19. Ethernet Switched Networks But There is No Limit on the Number of Switches Between the Farthest Stations –So there is no maximum distance span No Limit On Number of Switches or Span Ethernet Switch