1. Outlines Received due 13 March 2000 6%

2. MID-TERM n Wednesday, 1 March n Start studying NOW! n Work 4 of 5 pages n 1-2 pages of the previous midterm will be on the upcoming exam n Anything in the notes and reading assignment is fair game n Equations are provided

3. Ethernet Performance n Heard that Ethernet Throughput = 4 Mbps? Take it with a grain of salt. Simulations show Heavy Load throughput is a lot larger. n Simulations also show that Average Delay to move a packet at head of queue is small, even under heavy load conditions.

4. Token Ring Performance n Token Ring Efficiency No Load = 1/(1 + 2*NPD + TranTK/TranPK) Heavy Load = 1/(1 + (N+1)*NPD/N + TranTK/TranPK) = 1/(1 + NPD) ( under certain conditions )

5. Ethernet & Token Ring Efficiency 1.0 0.5 0.0.01.10 1.0 10.0 100 NPD

6. Performance Issues n Slow Speed Network? Both Ethernet & Token Ring work well n Borderline Network? Token Ring offers clearly superior performance n High Speed Network? Both stink. n Token Ring and Ethernet MAC’s don’t scale well to long distances or high speeds

7. ANSI FDDI n Covers OSI Layers 1 & 2 n 100 Mbps Line Speed n Originally Dual Counter-Rotating Rings n MAC is Timed Token Ring using RAT n Data traffic can only be passed if TRT < TTRT, and then only for TTRT-TRT seconds n Has Priorities. n MMAT = 2*TTRT

8. FDDI Performance n FDDI Efficiency No Load = TranPK/(1 + NPD + TranTK/TranPK) Heavy Load = (TTRT - Prop - N*TranTK)/TTRT

9. FDDI Status n ‘Looked down upon’ in trade pubs u Still an important protocol u Sees more use than is commonly acknowledged n Used mostly as a backbone u Roughly 50-60% corporate networks u Internet NAP’s & MAE’s u Bell Atlantic n New use declining - Glory days are over

10. Hi Speed LAN’s & MAN’s (Jan 1994) n FDDI

11. Hi Speed LAN’s & MAN’s (January 2000) n FDDI n ATM n 100 Mbps Ethernet n 100 Mbps Token Ring n 1 Gbps Ethernet Medium Distance Connectivity Short Distance Connectivity

12. Multiplexing n Splitting a chunk of Bandwidth up into channels n Channel can carry one conversation n FDM, TDM, & StatMux

13. FDM frequency time Different channels use some of the frequency all of the time. 12345

14. TDM frequency time 1 2 3 1 etc. Different channels use all of the frequency some of the time.

15. StatMux frequency time 1 3 1 2 Different channels use all of the frequency some of the time, at random, as needed.

16. StatMux vs. TDM & FDM n uses bandwidth more efficiently for bursty traffic n requires more overhead n has more variable deliveries n requires more complex & expensive hardware

17. Switching: How Long will a user get to use a channel? n For the duration of the conversation? Circuit Switching n For a tiny, variable length, portion of the conversation? Packet Switching n Circuit vs. Packet Switching Circuit has less end-to-end delay Circuit is less complex & cheaper Packet is more efficient for Bursty Traffic

18. StatMuxTDMFDM Circuit Packet Cell MULTIPLEXING SWITCHING common for voice common for data

19. Repeater or Hub n Operates at OSI Level 1 n ‘Electric Cable’ Traffic arriving at an input is immediately copied to all outputs.