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)

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

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

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

802.3 Packet Format PreSFD Destination Address Source Address LenCRCData + Padding Bytes:

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.

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

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

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

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.

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

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

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

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

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 VG-AnyLAN n is currently Dead RIP

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

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.

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

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

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

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

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.

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

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

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.

Shared 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

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

LAN History IEEE 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

IEEE 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 is dead. RIP

Ethernet & Token Ring Shared Network Efficiency NPD Efficiencies Token Ring 1/(1 + NPD) Ethernet 1/(1 + 5*NPD)

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

Shared Ethernet Efficiency Designed to operate as "Low Speed" NPD Standard CSMA/CD

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

... 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

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

Shared Ethernet Efficiency Gbps has higher NPD NPD 101.1

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.

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

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

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

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

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

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

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

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

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.

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.

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

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

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.

Ethernet Switch PreSFD Destination Address Source Address LenCRCData + Padding Bytes: Uses MAC Source Address to populate Look-Up Table Uses MAC Destination Address & Table for I/O Decision

Router MAC Destination Address MAC Source Address CRCData + Padding Bytes: IPv4TCP Populates Look-Up table independently of traffic. Uses Destination IP Address & Table for I/O Decision