ecen5553 telecom systems dr. george scheets week #8 readings: [18a] "trading at the speed of...
DESCRIPTION
Packet Switch StatMux Trunking Pure Internet (or Ethernet) Model Router Fixed Rate Traffic Bursty Data Traffic Assumptions: All Fixed Rate Traffic is packetized. All traffic is Statistically Multiplexed onto the trunk BW. SONET & OTN (Ethernet)TRANSCRIPT
ECEN5553 Telecom SystemsDr. George ScheetsWeek #8
Readings:[18a] "Trading at the Speed of Light"[18b] "Is The U.S. Stock Market Rigged?"
Optional: "Flash Boys"[16] "Voice over the Internet: A Tutorial"
Outline 7 October 2015, Lecture 22 (Live)No later than 14 October (Remote DL)
No Class Friday (Fall Break)
OutlinesReceived
due 7 October (local)14 October (remote)
44 %
Packet Switch StatMux TrunkingPure Internet (or Ethernet) Model
RouterFixed Rate Traffic
Bursty Data Traffic
Assumptions: All Fixed Rate Traffic is packetized. All traffic is Statistically Multiplexed onto the trunk BW.
SONET & OTN(Ethernet)
Internet Service Provider Backbone
Router
TrunksLeased LinePacketAware
StatMux, Packet Switched Network, Full Duplex Trunks.Access lines mostly attach to routers.
ATM Trunking(In Nineties, claimed as Tomorrow's Network Model)
ATMSwitch
Fixed Rate Traffic
Bursty Data Traffic
Assumptions: Fixed Rate Traffic gets CBR Virtual Circuits. CBR traffic gets near-TDM like service. Data Traffic is StatMuxed onto the remaining trunk BW.
SONET OC-N
ATM Backbone
ATM SwitchATM Switch
TrunksLeased LineCell
Aware
StatMux/TDM, Cell Switched Network, Full Duplex Trunks.Access lines mostly attach to ATM switches, and "ATM capable"
routers, FR switches, TD Muxes, & cross connects.
Circuit Switch TDM Trunking(Eighties 'Private Line' Network Model)
TDMSwitch
Fixed Rate Traffic
Bursty Data Traffic
Assumptions: All Traffic receives trunk bandwidth based on peak input rates. No aggregation. Data traffic consists of many slower speed, relatively lightly loaded circuits.
Fiber, Cable, & Microwave
Carrier Leased Line Backbone
Cross-ConnectCross-Connect
TrunksLeased LineByte
Aware
TDM, Circuit Switched Network, Full Duplex Trunks.Access lines mostly attach to routers, FR & ATM
switches, TD Muxes, & cross connects of other carriers.
Hybrid TDM Trunking(Network Model for older Carriers)
TDMSwitch
Fixed Rate
Bursty DataPacketSwitch
Assumptions: Bursty Data Traffic is all StatMuxed onto a common fabric (such as Frame Relay). Aggregate streams are TDM cross connected onto SONET. Trunk BW assigned based on peak rates.
SONET
Hybrid Network
Cross-ConnectCross-Connect
TrunksLeased LineByte
Aware
Fixed Rate Traffic: CSTDM bandwidth based on Peak RatesBursty Traffic: Access lines aggregated onto higher load trunk.
Packet Switch StatMux Trunks are CSTDM.
Voice Quality vs. Bit Rate
Bit Rate (Kbps)
QualityG.728 G.711G.726
8 16 32 64
G.729
G.723.1
Switched Network Carrying CapacitiesHigh Speed Trunk
Carrying Capacity
Circuit Switch TDM
Packet Switch StatMux
Cell Switch StatMux
Hybrid
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed RateOffered
Traffic Mix
Switched Network Carrying CapacitiesHybrid Network
Carrying Capacity
Circuit Switch TDM
Hybrid
all bursty data traffic groomed onto packet network
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed RateOffered
Traffic Mix
Switched Network Carrying CapacitiesHybrid Network
Carrying Capacity Hybrid
no data traffic groomed onto packet network
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed RateOffered
Traffic Mix
Switched Network Carrying CapacitiesHybrid Network
Carrying Capacity
real world network
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed RateOffered
Traffic Mix
Switched Network Carrying CapacitiesConvergence
Carrying Capacity
Circuit Switch TDM
Packet Switch StatMux
Cell Switch StatMux
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed RateOffered
Traffic Mix
70’s & 80’s Fixed Rate Voice Dominates
Voice
Data
time70’s & 80’s
Switched Network Carrying CapacitiesConvergence
Carrying Capacity
Circuit Switch TDM
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed RateOffered
Traffic Mix
Turn of the CenturyA Mixed Traffic Environment
Voice
Data
time2000
Switched Network Carrying CapacitiesConvergence
Carrying Capacity
Cell Switch StatMux
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed RateOffered
Traffic Mix
By 2005, Data Dominated
Voice
Data
time
2005
Switched Network Carrying CapacitiesConvergence
Carrying Capacity
Packet Switch StatMux
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed RateOffered
Traffic Mix
What's the impact of Video? Video #1 since 2010, is a packet switched statmux network best?Video #1 since 2010, is a packet switched statmux network best?
Yes. Most video coders are variable rate.Yes. Most video coders are variable rate. Two changes to make the network more video friendly… Two changes to make the network more video friendly…
Might be a good idea to increase Ethernet's maximum packet size.Might be a good idea to increase Ethernet's maximum packet size. All packets with bit errors shouldn't be droppedAll packets with bit errors shouldn't be dropped
Voice/Video dropped packet = lower qualityVoice/Video dropped packet = lower quality Better quality possible if payload deliveredBetter quality possible if payload delivered
Carrying Capacity... Got Got bursty data bursty data traffictraffic to move?to move?
A A packet switched system packet switched system using using statistical statistical multiplexing multiplexing will allow you to service the most will allow you to service the most users given a fixed chunk of bandwidth. users given a fixed chunk of bandwidth.
GotGot fixed rate fixed rate traffic to move?traffic to move?A A circuit switched circuit switched system will allow you to system will allow you to service the most customers given a fixed chunk service the most customers given a fixed chunk of bandwidth.of bandwidth.
WAN Trends 60's - Fixed Rate Voice Dominates60's - Fixed Rate Voice Dominates
Voice Network moving data on the sideVoice Network moving data on the side Mid to Late 90's – Mixed Traffic EnvironmentMid to Late 90's – Mixed Traffic Environment
New Carriers – ATMNew Carriers – ATM Older Carriers – HybridOlder Carriers – Hybrid
Early 00's - Mostly Bursty TrafficEarly 00's - Mostly Bursty Traffic Data Networks moving voice on the sideData Networks moving voice on the side
10's - Mostly Video10's - Mostly Video Data Networks moving video Data Networks moving video
Data & voice on the sideData & voice on the side
Example) Coding aMicrophone Output
time (sec)
m(t) volts (air pressure)
Energy from about 500 - 3,500 Hz.
A/D Convertor
time (sec)
m(t) volts (air pressure)
Step #1)Sample the waveform at rate > 2*Max Frequency.Telephone voice is sampled at 8,000 samples/second.
1/8000 second
A/D Convertor Legacy Wired Telephone System uses PCMLegacy Wired Telephone System uses PCM
Pulse Code ModulationPulse Code Modulation One of N possible equal length Code One of N possible equal length Code Words is Words is assigned to each Voltageassigned to each VoltageN Typically a Power of 2N Typically a Power of 2LogLog22N bits per code wordN bits per code word Wired Phone System: N = 256 & 8 bits/wordWired Phone System: N = 256 & 8 bits/word Compact Disk: N = 65,536 & 16 bits/wordCompact Disk: N = 65,536 & 16 bits/word
A/D Convertor. 1 bit/sample.
time (sec)
Example) N = 2. Assign 0 or 1 to voltage.
0 < Voltage < +5v, Assign Logic 1-5v < Voltage < 0, Assign Logic 0
3.62 v, output a 1
t1
Bit Stream Out = 1111110000111...
A/D Convertor. 1 bit/sample.Example) N = 2. Assign 0 or 1 to voltage.
Far side gets... 1111110000111 (13 samples)Needs to output 13 voltages.What does a 1 represent? A 0?
Receive a 1? Output +2.5 v (mid-range)Receive a 0? Output -2.5 v (mid-range)
Hold the voltage until next sample
0 < Voltage < +5v, Assign Logic 1-5v < Voltage < 0, Assign Logic 0
A/D Convertor. 1 bit/sample.
Input to the transmitter.Output at the receiver.
Considerable Round-Off error exists.
+2.5 v
-2.5 v
time (sec)
Example) N = 4. Assign 00, 01, 10 or 11.
2.5 < Voltage < 5 , Assign 110 < Voltage < 2.5, Assign 10-2.5 < Voltage < 0, Assign 00-5 < Voltage < -2.5, Assign 01
3.62 v, Assign 11
t1
Bit Stream Out =11111011111100 000000101011...
+2.5 v
-2.5 v
A/D Convertor. 2 bits/sample
A/D Convertor. 2 bits/sample.
Input to the transmitter.Output at the receiver.
Receive 11? Output 3.75vReceive 10? Output 1.25vReceive 00? Output -1.25vReceive 01? Output -3.75vReduced Round-Off error exists.
+3.75 v
+1.25 v
-1.25 v
-3.75 v
Circuit Switched Voice (POTS) Bandwidth ≈ 3,500 HertzBandwidth ≈ 3,500 Hertz A/D ConverterA/D Converter
samples voice 8,000 times/secondsamples voice 8,000 times/second rounds off voice to one of 256 voltage levelsrounds off voice to one of 256 voltage levels transmits 8 bits per sample to far sidetransmits 8 bits per sample to far side
D/A ConverterD/A Converter receives 8 bit code wordreceives 8 bit code word outputs one of 256 voltage levels for 1/8000th secondoutputs one of 256 voltage levels for 1/8000th second
64,000 bps (1 byte, 8000 times/second)64,000 bps (1 byte, 8000 times/second)
Compact Disk Bandwidth ≈ 20,000 HertzBandwidth ≈ 20,000 Hertz A/D ConverterA/D Converter
samples voice 44,100 times/secondsamples voice 44,100 times/second rounds off voice to one of 65,536 voltage levelsrounds off voice to one of 65,536 voltage levels transmits 16 bits per sample to far sidetransmits 16 bits per sample to far side
D/A ConverterD/A Converter receives 16 bit code wordreceives 16 bit code word outputs one of 65,536 voltage levels for 1/44100th secondoutputs one of 65,536 voltage levels for 1/44100th second
705,600 bps705,600 bps
Sampling & Quantizing Examples fs = 16 KHzfs = 16 KHz
4096 quantiles4096 quantiles 256 quantiles (approximate phone quality)256 quantiles (approximate phone quality) 32 quantiles32 quantiles 4 quantiles (generally 2 levels used!)4 quantiles (generally 2 levels used!)
4096 quantiles4096 quantiles fs = 16 KHzfs = 16 KHz fs = 8 KHz (some interference)fs = 8 KHz (some interference) fs = 2 KHzfs = 2 KHz fs = 1 KHzfs = 1 KHz
1/8th Second of Voice
1/8th Second of Voice
1/8th Second of Voice
Sources of POTS delay
Local Loop
PCMCoder TDM Trunk
POTSTSI
POTSTSI
IntermediateDigitalVoice
Switches
...
TDM TrunkLocal Loop
PCMCoder
Trunk resources are dedicatedto each voice call via TDM.
Source CO
Destination CO
Sources of VoIP delay
VoiceCoder
PacketSwitch
PacketSwitch
IntermediatePacket
Switches...
StatMuxTrunks
VoiceDecoder
Trunk resources are randomly assigned to each voice call via Statistical Multiplexing.
PacketAssembler
TransmissionBuffer
ReceiverBuffer
Voice (Video) on LAN (WAN) More complex system than circuit switched More complex system than circuit switched
voicevoice Packet AssemblerPacket Assembler Transmitter BufferTransmitter Buffer Receiver BufferReceiver Buffer
End-to-End Delays > Circuit Switch TDMEnd-to-End Delays > Circuit Switch TDM Delay Variability > Circuit Switch TDMDelay Variability > Circuit Switch TDM