1. 3COM SuperStack 2 10/100 Baseline Switch 3C16465A Naomi Avigdor October 25, 2001

2. CSMA/CD Carrier Sense Multiple Access with Collision Detection Bus topology – shared media Half Duplex - CSMA/CD states –Idle –Transmission –Contention: if no collision occurs before the end of the period, then complete transmission of the frame

3. Half Duplex MAC (think conference call) CS – Carrier Sense (Is someone already talking?) –If not – then transmit if you have data –If yes - wait MA – Multiple Access (everyone hears everyone) –Jim: “Hey Scott, This is Jim, what is the weather in Chicago?” –Tony: “Hey Susan, This is Tony, would you marry me?” CD – We are both talking –“everybody stop, we have a collision”

4. Collision Domain Twice the maximum network end to end propagation delay Defines Network diameter Defines minimum frame size

5. Full Duplex – Ethernet Switch UTP – Unshielded twisted pair Transmit pair separate from receive pair Point-To-Point only Media not shared, no collision domain Aggregate throughput is doubled Transmit and receive simultaneously Each switch port own MAC

6. Switch Internals Shared RAM –“Store & Forward” or “Cut Through” Input queuing versus Output queuing –Head-of-Line (HOL) blocking Scheduling: –Port priority –Round Robin –Global FIFO

7. Individual Switch Write Performance

8. Aggregate Switch Write Performance

9. Flow Control Ok to mix port speed Use MAC “Pause Frame” for flow control

10. Channel Bonding Network Interface Cards (NICs) bonded for outgoing load balancing Does it bond for incoming traffic???

11. References http://www.iol.unh.edu/training/ge/Ethernet _Evolution_files/frame.htmhttp://www.iol.unh.edu/training/ge/Ethernet _Evolution_files/frame.htm IEEE 802.3 standards doc. Computer Networks Third Ed.by Andrew S. Tanenbaum