1. ECEN5553 Telecom Systems Week #3 Read: [3] "A Roadmap to 100 Gbps Ethernet" [4a] "What if Ethernet Failed?" thru [4d] "Showdown Coming on Ethernet Standard" Exam #1: Lecture 14, 16 September (Live) No later than 23 September (Remote DL) Outline: Lecture 22, 5 October (Live) No later than 12 October (Remote DL)

2. Outlines Received due 5 October (local) 12 October (remote)
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3. Power Lines act as Antennas
Source:

4. Power Line Communications
Transformers don't pass high frequency signals.
Image Source
Wikipedia

5. Home Power Line Networks
Possible using home wiring
Outside Step Down Transformer blocks further wired transmission
Signal radiates off internal house wiring
Netgear claims 500 Mbps

6. Normalized Propagation Delay
NPD = End-to-End Propagation Delay Average time to inject a Packet
NPD > 1 1 or more packets can simultaneously be in transit
If NPD = 5, 5 average sized packets can be physically on the line
NPD < 1 Packet front end hits far side before back end transmitted
High Speed Low Speed
Transmitter
Receiver

7. Types of Traffic...
Computer Data Bursty Highly sensitive to errors Not as time sensitive as voice or video
Interactive Voice/Video Fixed Rate (if not compressed) *Not very sensitive to errors Fixed or Variable Rate (if compressed) *Sensitive to errors Time Sensitive

8. IEEE Institute for Electrical & Electronics Engineers
Largest Technical Organization in the World
Promotes betterment of Electrical Engineering
Journals & Magazines
Conferences
Standards

9. IEEE 802.3 Ethernet Based on late 1970’s technology
Covers OSI Layers 1 & 2
10 Mbps Line Speed
Logical Bus
Designed to move Computer Data
The various flavors dominate the wired LAN

10. Serial Bit Stream: NRZ Coding
Logic
One
Logic
Zero T
volts
Called ‘Non Return to Zero’
because voltage never dwells
on zero volts. +1
time -1 T

11. Ethernet Uses Manchester Coding
Logic
One
Logic
Zero
All symbols
have a transition
in the middle.
volts +1
time -1 T

12. Ethernet Uses Manchester Coding
volts +1
time -1 T
High Pass Filters Emphasize Change

13. High Pass Filter Output+1
time -1

14. Rectify (Absolute Value)+1 T
time -1
Result always has pulses T seconds apart.
Useful for receiver synchronization.

15. What is CSMA/CD? Polite Conversation One node active at a time
No deliberate interruptions
Collisions sometimes occur after a pause

16. 802.3 Back-Off Algorithm
choose random number 1st Collision 0, 1 2nd Collision 0, 1, 2, 3 3rd Collision 0, 1, ..., 6, 7 4th Collision 0, 1, ..., 14, th Collision 0, 1, ..., 1022, th Collision 0, 1, ..., 1022, th Collision Punt
Wait (Random Number* ) seconds

17. 802.3 MAC Flow Chart No Packet to Send? Drop Packet.
Notify Higher Layer
Yes
Yes No
Set Collision Couter
= 0
16th Collision?
Back-Off
Yes
Traffic on
Network?
Bump Collision
Counter by +1 No
Send Packet
Yes
Collision?
Jam No

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

19. 802.3 Packet Format Bytes: 7 1 6 6 2 Pre SFD Destination Address
Source
Len
CRC
Data + Padding

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

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

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

23. 10BaseT & Shared Hub PC PC Twisted Pair Hub PC PC
Logical Bus & Physical Star
Shared hub (OSI Level 1) copies input bits to all outputs.
All nodes monitor traffic. 4 nodes share 10 Mbps.

24. 10BaseT & Switched Hub Switch PC PC PC PC 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.

25. Logical Bus & Physical Star with the Switched Hub if Half Duplex.
10BaseT & Switched Hub PC PC
Switched
Hub PC PC
Logical Bus & Physical Star
Each node shares 10 Mbps
with the Switched Hub if Half Duplex.

26. 10BaseT & Switched Hub PC PC reception is screwed up Switched Hub PC
Using Half Duplex 10BaseT,
a collision occurs if PC & Switched Hub
simultaneously transmit.

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

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

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

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

31. Full Duplex System PC PC Switched Hub PC PC
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.

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

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

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

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

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

37. 10BaseT & Shared Hub PC 53 m PC 8 m Hub PC PC 26 m 17 m
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.

38. 10BaseT & Switched Hub Switch PC 53 m PC 8 m PC PC 26 m 17 m
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.

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

40. Shared 802.3 LAN Efficiencies
500 m end-to-end Heavy Load Conditions
100 B packets: Formula = efficiency 5 nodes: simulated 50 nodes: simulated
1500 B packets: Formula = efficiency 5 nodes: simulated 50 nodes: simulated
Conclusion: Heavy Load η reasonably accurate

41. Head of Line Performance
185 m end-to-end, 130 byte packets
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.
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

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

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

44. Ethernet & Token Ring Shared Network Efficiency
1.0
Efficiencies
Token Ring 1/(1 + NPD)
Ethernet 1/(1 + 5*NPD)
0.5
0.0
NPD

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

46. Shared Ethernet Efficiency Designed to operate as "Low Speed"
1.0
Standard CSMA/CD
0.5
0.0
NPD