1. ECEN5553 Telecom Systems Week #3 Read [4a] "High Speed Ethernet: A Planning Guide" [4b] "What If Ethernet Failed?" [4c] "8 Ethernet Predictions for 2014" [5a] "Is Your Ethernet Fast Enough?" [5b] "Showdown Coming on Ethernet Standard to Serve Faster Wi-Fi" [6a] "Browse at Your Own Risk" [6b] "The Data Brokers: Selling Your Personal Information" Exam #1 Lecture 15, 21 September (Live) No later than 28 September (Remote DL) Outline 7 October 2015, Lecture 22 (Live) No later than 14 October (Remote DL)

2. Outlines Received due 7 October (local) 14 October (remote) 0 %

3. 802.3 MAC Flow Chart Packet to Send? No Yes Set Collision Couter = 0 Traffic on Network? Yes No Send Packet Collision? No Jam Yes Bump Collision Counter by +1 16th Collision? Drop Packet. Notify Higher Layer Yes Back-Off No

4. Major Drawbacks of CSMA/CD n MMAT equals infinity (No guaranteed Bandwidth) n No Priorities These make 802.3 Ethernet marginal, at best, for Multimedia Traffic.

5. 802.3 Packet Format PreSFD Destination Address Source Address LenCRCData + Padding Bytes: 7 1 6 6 2 46-1500 4

6. Preamble time +1 volts 0 T 0 0 Logic One Logic Zero Series of pulses generated at receiver T seconds apart & in middle of each symbol.

7. Transmitting a File n Broken into smaller packets n Initial packets from Layer 5 Open Logical Connection n Packets from Layer 7 “Data” Contains Layer 7 traffic “Data” Contains Layer 3-6 info n Packets from Layer 4 Acknowledgements n Final packets from Layer 5 Close Logical Connection

8. 10Base5 & 10Base2 (Obsolete) PC Printer Logical & Physical Bus All nodes monitor traffic Nodes share 10 Mbps Coax Cable 10Base5 "Vampire Tap" 10Base2 "T" connection Images from Wikipedia

9. 10BaseT & Shared Hub PC Hub Logical Bus & Physical Star Shared hub (OSI Level 1) copies input bits to all outputs. All nodes monitor traffic. 4 nodes share 10 Mbps. Twisted Pair

10. 10BaseT & Switched Hub PC Switch Logical Bus & Physical Star Switched Hub (OSI Level 1 & 2) copies packet to proper output. Only the destination monitors traffic. This example system can move up to 20 Mbps provided the packet source & destinations differ.

11. 10BaseT & Switched Hub PC Switched Hub Logical Bus & Physical Star Each node shares 10 Mbps with the Switched Hub.

12. 10BaseT & Switched Hub PC Switched Hub Using Half Duplex 10BaseT, a collision occurs if PC & Switched Hub simultaneously transmit. reception is screwed up

13. IEEE 802.3u 100 Mbps Fast Ethernet n Preserves CSMA/CD n Preserves Packet Format n Maximum End-to-End Lengths (a.k.a. Collision Domain) reduced to keep Normalized Propagation Delay low n Sales exceed 10 Mbps as of ‘98

14. Ethernet Switch Port Sales Source: "A Roadmap to 100G Ethernet at the Enterprise Data Center" IEEE Communications Magazine, November 2007

15. Back around 1994 to 1995… n Two 100 Mbps "Ethernets" introduced n Version A u CSMA/CD MAC, Ethernet Frames n Version B u Demand Priority MAC, Ethernet Frames n IEEE said Version A is Ethernet u IEEE 802.3u Fast Ethernet n IEEE said Version B is not Ethernet u IEEE 802.12 100VG-AnyLAN n 802.12 is currently Dead RIP

16. IEEE 802.3z 1 Gbps Ethernet (1998) n Uses an extended version of CSMA/CD, including "Frame Bursting" n Best performance uses full duplex connections & switched hubs u CSMA/CD included so it can be called Ethernet n Collision Domain same as Fast Ethernet n Preserves Packet Format n Fiber or Cat6 Cables

17. Full Duplex System PC Switched Hub All > 10 Gbps, most 1 Gbps, & many 100 Mbps systems are Full Duplex. Net IC’s are designed to simultaneously transmit & receive. Line no longer shared. No Collisions. No need for CSMA/CD.

18. IEEE 802.3ae 10 Gbps “Ethernet” (2002) n Standard as of June 2002 n Does not use CSMA/CD u Uses switched hubs & full duplex connections u Uses Ethernet frame format n Initial available products used fiber u Copper cabling now an option

19. IEEE 802.3ba 40 & 100 Gbps “Ethernet” (2010) n Standard as of June 2010 n Does not use CSMA/CD u Uses switched hubs & full duplex connections u Uses Ethernet frame format n Copper cabling an option u 7-10 m, 10 twisted pairs required n Mostly uses fiber

20. IEEE 802.1p Priority Tags n 8 priorities n MAC protocols remain unchanged n Used by 802.1p enabled switches u Allows interactive voice or video to receive preferential treatment on an Ethernet LAN

21. Many Ethernet Physical Layer Standards Exist source: "Evolution of Ethernet Standards in the IEEE 802.3 Working Group", IEEE Communications Magazine, August 2013

22. LAN Throughput n Average bit transmission rate actually available for use n Throughput = Efficiency * Line Speed n Shared Half Duplex Network u No Load Efficiency: ≈ 100% F Actually a little less since frames can't be transmitted back-to-back u Heavy Load Efficiency: ≈ 1/(1+5*NPD) F Shared network: apply to entire network F Switched network: apply between switched hub & end device n Switched Full Duplex Network Efficiency u ≈ 100% These are Estimates.

23. 10BaseT & Shared Hub PC Hub Logical Bus & Physical Star Shared hub (OSI Level 1) copies input bits to all outputs. All nodes monitor traffic. 4 nodes share 10 Mbps. Max end-to-end distance is 79 meters. 53 m 26 m 8 m 17 m

24. 10BaseT & Switched Hub PC Switch Logical Bus & Physical Star Switched hub (OSI Level 1 & 2) is packet & MAC aware. Nodes don't see all traffic. Line shared between node & switch. η Distance to use is PC to Hub specific. 53 m 26 m 8 m 17 m

25. Ethernet Performance n Simulations show CSMA/CD is very efficient for slow speed Networks. u Shared Ethernet efficiency equation reasonably accurate. n Simulations also show that Average Delay to move a packet at head of queue is usually small, even under heavy load conditions.

26. Shared 802.3 LAN Efficiencies n 500 m end-to-end Heavy Load Conditions n 100 B packets: Formula =.8809 efficiency 5 nodes:.9986 simulated 50 nodes:.6980 simulated n 1500 B packets: Formula =.9911 efficiency 5 nodes:.9953 simulated 50 nodes:.9532 simulated n Conclusion: Heavy Load η reasonably accurate

27. Head of Line Performance n 185 m end-to-end, 130 byte packets n 5 nodes > 90% of packets do not collide Average collisions/packet =.05 Average delay to transmit = 51 microsec. Maximum delay to transmit = 11.3 msec. n 50 nodes > 45% collide one or more times (2% 16x) Average collisions/packet =.93 Average delay to transmit = 340 microsec. Maximum delay to transmit = 236 msec

28. LAN History IEEE 802.5 Token Ring n Based on early 1980’s technology n Covers OSI Layers 1 & 2 n 4 or 16 Mbps Line Speed n Logical Ring n A ‘Token’ is passed around the ring Node must have the Token to transmit n Guaranteed Bandwidth n Has Priorities

29. IEEE 802.5 Token Ring n Technically Superior to shared Ethernet n Similar evolution to Ethernet u Logical & Physical Ring u Logical Ring, Shared Physical Star u Logical Ring, Switched Physical Star n 100 Mbps products available in ’98 u 3 years after Fast Ethernet n Sales have crashed. 802.5 is dead. RIP

30. Ethernet & Token Ring Shared Network Efficiency 1.0 0.5 0.0.01.10 1.0 10.0 100 NPD Efficiencies Token Ring 1/(1 + NPD) Ethernet 1/(1 + 5*NPD)

31. Shared Network 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

32. Shared Ethernet Efficiency Designed to operate as "Low Speed" 1.0 0.5 0.0.01.10 1.0 10.0 100 NPD Standard CSMA/CD

33. Low Speed Network? This configuration... PC Server Hub 10BaseT & Shared Hub

34. ... is as good as this one... PC Server Switched Hub 10BaseT & Switched Hub n...IF traffic mostly going to/from same machine n Switched Hub better if diverse traffic flow

35. This configuration is even better. PC Server Switch n Server on a higher speed line. 100 Mbps10 Mbps 1 Gbps

36. Shared Ethernet Efficiency Gbps has higher NPD 1.0 0.5 0.0.01.10 1.0 10.0 100 NPD 101.1

37. High Speed Network? This configuration has horrible throughput. PC Server Shared Hub 1 or 10 Gbps & Shared Hub Under heavy load, too much time spent recovering from collisions.

38. Ethernet (Shared) Hub n Operates at OSI Level 1 n ‘Electric Cable’ Traffic arriving at an input is immediately copied to all other ports on a bit-by bit basis. n Used on LAN's. Pretty much obsolete. n Repeater = single input & single output hub u Not used much on Ethernet any more u Generally now only used on WAN long haul F May be different protocol than Ethernet

39. Black Box Performance... OSI Level 1 LAN Hub Two packets simultaneously show up at input... From Node A Node B Node C To Node A Node B Node C

40. Black Box Performance...... will overwrite each other, i.e. garbage out. a.k.a. Shared Hub OSI Level 1 LAN Hub From Node A Node B Node C To Node A Node B Node C

41. Black Box Performance... Two packets simultaneously show up at input... OSI Level 1-2 (Switch) or 1-3 (Router)

42. Black Box Performance...... one will be transmitted (when allowed by MAC), the other momentarily buffered... OSI Level 1-2 (Switch) or 1-3 (Router)

43. Black Box Performance...... and then transmitted. OSI Level 2/3 Switch or Router

44. 10BaseT & Shared Hub PC Hub One big collision domain. 53 m 26 m 8 m 17 m

45. 10BaseT & Half Duplex Switch PC Switch Four smaller collision domains. 53 m 26 m 8 m 17 m

46. Example World 7 Users 7 Users Hub 1 Hub 2 If Box 1 & 2 are Level 1 Hubs One Big Collision Domain 15 Nodes share 10 Mbps Each node gets average of 10/15 Mbps 10BaseT Right Side to World gets 7/15th of available BW, on average.

47. Example World 7 Users 7 Users Sw 1 Sw 2 If Box 1 & 2 are Level 2 Switches Each node shares 10 Mbps with Switch Right Hand Side is on one 10 Mbps line. 10BaseT Right Side to World gets _____ of available BW. 1/8th (Was 7/15th) Right hand side sees increased delays. Can be alleviated with 100 Mbps Box 1 ↔ Box 2 link.

48. Switched Hubs or Bridge n On Power Up know nothing n When a packet arrives at an input port... u Look-Up Table consulted u Source MAC address not in table? F Table Updated: MAC address & Port matched u Destination MAC address not in table? F Packet broadcast to all outputs (a.k.a. flooding) u Destination MAC address in table? F Packet shipped to proper output n Look-up Table update is dependent on packet arrivals

49. Router n Operates at OSI Layers 1, 2, & 3 n Capable of making complex routing decisions u ‘peers into’ packets and examines Layer 3 address n Very useful on Large Networks with multiple end-to-end paths n Routers frequently exchange connectivity info with neighboring Routers u Routing Algorithms used to update Routing (Look-Up) Tables u Tables updated independently of traffic

50. Bridging versus Routing n Ethernet Bridge, Switch, or Switched Hub u Uses Layer 2 MAC Address u Unknown Destination? Flooded u Look-up Table updates are packet dependent n Router u Uses Layer 3 Internet Protocol Address u Unknown Destination? Default location u Look-up Tables updated independently of traffic n Small Network? Doesn't matter n Big Network? Floods not a good idea.

51. Ethernet Switch PreSFD Destination Address Source Address LenCRCData + Padding Bytes: 7 1 6 6 2 46-1500 4 Uses MAC Source Address to populate Look-Up Table Uses MAC Destination Address & Table for I/O Decision

52. Router MAC Destination Address MAC Source Address CRCData + Padding Bytes: 7 1 6 6 2 20 20 6-1460 4 IPv4TCP Populates Look-Up table independently of traffic. Uses Destination IP Address & Table for I/O Decision