ecen5553 telecom systems dr. george scheets week #8 readings: [16] "voice over the internet: a...
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ECEN5553 Telecom SystemsDr. George ScheetsWeek #8Readings:[16] "Voice over the Internet: A Tutorial"[17a] "Rapidly Recovering from Catastrophic Loss… "
[17b] "How IT Leaders Can Best Plan For Disaster"[18a] "Trading at the Speed of Light" [18b] "Is The U.S. Stock Market Rigged?"Outline
8 October 2014, Lecture 22 (Live)No later than 15 October (Remote DL)
Exam #1 Results (90 points)Hi = 84.2, Low = 43.8, Ave = 67.22, σ = 10.37A > 78, B > 64, C > 55, D > 46
ECEN5553 Telecom SystemsDr. George ScheetsWeek #8Readings:[16] "Voice over the Internet: A Tutorial"[17a] "Rapidly Recovering from Catastrophic Loss… "
[17b] "How IT Leaders Can Best Plan For Disaster"[18a] "Trading at the Speed of Light" [18b] "Is The U.S. Stock Market Rigged?"Outline
8 October 2014, Lecture 22 (Live)No later than 15 October (Remote DL)
Exam #1 Results (90 points)Hi = 84.2, Low = 43.8, Ave = 67.22, σ = 10.37A > 78, B > 64, C > 55, D > 46
OutlinesReceived
due 8 October (local)
15 October (remote)
OutlinesReceived
due 8 October (local)
15 October (remote)
61 %
802.3 Ethernet Packet Format802.3 Ethernet Packet Format
MACDestination
Address
MACSource
Address
CRCData + Padding
Bytes: 6 6 2
20 20 6-1460 4
IP TCP
Provider Backbone BridgeCarrier Ethernet Packet (Simplified)
Provider Backbone BridgeCarrier Ethernet Packet (Simplified)
MACDestination
Address
MACSource
Address
CRCData + Padding
Bytes: 6 6 2 6 6 2
20 20 6-1460 4
IP TCP
Carrier MACDestination
Address
Carrier MAC Source
Address
Carrier Edge switches prepend customer Ethernet frames with Carrier Edge switches prepend customer Ethernet frames with provider frames.provider frames. # Carrier MAC addresses = # Carrier edge switches# Carrier MAC addresses = # Carrier edge switches
Carrier VLAN
Tag
LAN
LAN
Carrier Ethernet WAN/MANCarrier Ethernet WAN/MAN
E1
EthernetEthernetSwitchSwitch
LANLAN
LAN
LAN
Every Carrier Switch is an Edge Switch here. Every Carrier Switch is an Edge Switch here.
Edge Switches learn MAC addresses of serviced end devices. E1 Edge Switches learn MAC addresses of serviced end devices. E1 must learn must learn YellowYellow & & OrangeOrange MAC & VLAN addresses. MAC & VLAN addresses.
LAN
LAN
LAN
Carrier Ethernet Switching (Simplified) Carrier Ethernet Switching (Simplified) Unicast packet arrives with unknown customer Unicast packet arrives with unknown customer
destination MAC addressdestination MAC address Source Carrier Edge SwitchSource Carrier Edge Switch
ExaminesExamines Customer VLAN tag & source MAC address Customer VLAN tag & source MAC address Maps toMaps toCarrier VLAN tag Carrier VLAN tag Carrier Edge Switch MAC addressCarrier Edge Switch MAC addressAppendsAppends Carrier Header Carrier Header
Destination Carrier Edge SwitchDestination Carrier Edge SwitchExamines & Removes Examines & Removes Carrier HeaderCarrier HeaderForwardsForwards based on Customer MAC address based on Customer MAC address
Carrier Ethernet Switching (Simplified) Carrier Ethernet Switching (Simplified) Broadcast packet arrivesBroadcast packet arrives
Source Carrier Edge SwitchSource Carrier Edge SwitchExaminesExamines Customer VLAN tag & source MAC address Customer VLAN tag & source MAC address Maps toMaps toCarrier VLAN tag Carrier VLAN tag Carrier Edge Switch MAC address(es)Carrier Edge Switch MAC address(es)AppendsAppends Carrier Header Carrier HeaderSelectively FloodsSelectively Floods
Destination Carrier Edge SwitchDestination Carrier Edge SwitchExamines & Removes Examines & Removes Carrier HeaderCarrier HeaderForwardsForwards based on Customer VLAN based on Customer VLAN
Carrier Ethernet StatusCarrier Ethernet Status
2009 U.S. Market Revenue $1.5 Billion2009 U.S. Market Revenue $1.5 Billion 2010 $3.2 Billion2010 $3.2 Billion 2013 $5.5 Billion2013 $5.5 Billion 2016 $11.1 Billion (projected)2016 $11.1 Billion (projected) 2018 $13 Billion (projected)2018 $13 Billion (projected)
Backhaul from wireless cell sites a major Backhaul from wireless cell sites a major growth areagrowth area
source: www.accedian.comwww.telecompetitor.com
MAN/WAN Connectivity OptionsMAN/WAN Connectivity Options Carrier EthernetCarrier Ethernet
Switches are Ethernet frame awareSwitches are Ethernet frame aware I/O decisions based on Layer 2 Ethernet AddressI/O decisions based on Layer 2 Ethernet Address
Virtual Circuits can be usedVirtual Circuits can be used StatMuxStatMux
BW required based more so on BW required based more so on averageaverage input rates input rates
Pricing function of peak rate, CIR, priority, and maybe Pricing function of peak rate, CIR, priority, and maybe distancedistance
On the way in.On the way in. 21st century version of Frame Relay21st century version of Frame Relay
Carrying CapacityCarrying Capacity
Line Speed
Active Idle
Application Traffic Overhead
Carrying Capacity = Traffic(bps)/Line Speed(bps)
Goodput = Application Traffic Carried (bps)
Queue LengthQueue Length
100,000,000 bps output trunk100,000,000 bps output trunk 100,000,001 bps average input100,000,001 bps average input Average Input rate > Output rateAverage Input rate > Output rate Queue Length builds upQueue Length builds up
(without bound, in theory)(without bound, in theory)
Queue LengthQueue Length
100,000,000 bps output trunk100,000,000 bps output trunk 99,999,999 bps average input99,999,999 bps average input Average Input rate < Output rateAverage Input rate < Output rate Queue Length not infinite...Queue Length not infinite...
...but ...but veryvery large large
Queue Length @ 100% LoadOutput capacity = 7 units
Input = 7 units on average (two dice rolled)
Queue Length @ 100% LoadOutput capacity = 7 units
Input = 7 units on average (two dice rolled)
t1: input = 4, output = 4, queue = 0t1: input = 4, output = 4, queue = 0 t2: input = 5, output = 5, queue = 0t2: input = 5, output = 5, queue = 0 t3: input = 4, output = 4, queue = 0t3: input = 4, output = 4, queue = 0 t4: input = 7, output = 7, queue = 0t4: input = 7, output = 7, queue = 0 t5: input = 11, output = 7, queue = 4t5: input = 11, output = 7, queue = 4 t6: input = 10, output = 7, queue = 7t6: input = 10, output = 7, queue = 7 t7: input = 6, output = 7, queue = 6t7: input = 6, output = 7, queue = 6 t8: input = 5, output = 7, queue = 4t8: input = 5, output = 7, queue = 4 t9: input = 8, output = 7, queue = 5t9: input = 8, output = 7, queue = 5 t10: input = 11, output = 7, queue = 9t10: input = 11, output = 7, queue = 9
This queue will tend to get very large over time.This queue will tend to get very large over time.
Queue Length @100% LoadWill tend to increase w/o Bound.
Queue Length @100% LoadWill tend to increase w/o Bound.
0 2 105 4 105 6 105 8 105 1 1060
2000
40003.409 10
3
0
queue5 j
1 1060 j 5
0 2 105 4 105 6 105 8 105 1 1060
1000
20001.983 10
3
0
queue5 j
1 1060 j 5
"Die Roll" Queue Lengths"Die Roll" Queue Lengths
0 2 105 4 105 6 105 8 105 1 1060
2000
40003.409 10
3
0
queue5 j
1 1060 j 5
100% Load
101% Load
99% Load, Average Queue = 44.46
Real vs Artificial TraceReal vs Artificial Trace
10 SecondsReal Traffic 10 Seconds
Artificial M/M/1 Traffic
Source: Willinger et al, "Self-Similarity through High Variability", IEEE/ACM Transactions on Networking, February 1997.
Real vs Artificial TraceReal vs Artificial Trace
100 SecondsReal Traffic 100 Seconds
Artificial M/M/1 Traffic
Real vs Artificial TraceReal vs Artificial Trace
16.7 MinutesReal Traffic 16.7 Minutes
Artificial M/M/1 Traffic
Real vs Artificial TraceReal vs Artificial Trace
167 MinutesReal Traffic 167 Minutes
Artificial M/M/1 Traffic
Real vs Artificial TraceReal vs Artificial Trace
27.78 HoursReal Traffic 27.78 Hours
Artificial M/M/1 Traffic
Infinite Length Queue (Classical StatMux Theory)Infinite Length Queue (Classical StatMux Theory)
0% 100%Trunk Offered Load
Probability of dropped packets
Average Delay fordelivered packets
Finite Length Queue (Real World StatMux)Finite Length Queue (Real World StatMux)
0% 100%Trunk Offered Load
Probability of dropped packets
Average Delay fordelivered packets
Cla
ssic
al
Self
-Sim
ilar
You could fully load StatMux trunk lines... but yourcustomers would be screaming at you due to lousy service.
Switched Network Carrying CapacitySwitched Network Carrying Capacity
Line SpeedLine Speed: Traffic injection speed: Traffic injection speed EfficiencyEfficiency: Ability to use that Line Speed: Ability to use that Line Speed ThroughputThroughput: bps of traffic (+ overhead) moved: bps of traffic (+ overhead) moved
= Efficiency * Line Speed= Efficiency * Line Speed Carrying CapacityCarrying Capacity: Ability to : Ability to usefullyusefully use Line Speed use Line Speed
Accounts for packet overheadAccounts for packet overhead Accounts for inability to fully load trunk lines with Accounts for inability to fully load trunk lines with
StatMux'd traffic & still have a usable connectionStatMux'd traffic & still have a usable connection Goodput: Goodput: bps of application traffic movedbps of application traffic moved
= Carrying Capacity * Line Speed= Carrying Capacity * Line Speed
Carrying CapacityCarrying Capacity
Line Speed
Active Idle
Traffic Overhead
Carrying Capacity = (%Trunk Load) * (%Traffic) = Traffic(bps)/Line Speed(bps)
Packet Switch StatMux Trunking(Pure Internet Model)
Packet Switch StatMux Trunking(Pure Internet 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
Internet Service Provider BackboneInternet 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)
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 BackboneATM Backbone
ATM SwitchATM Switch
TrunksLeased LineCell
Aware
StatMux/TDM, Cell Switched Network, Full Duplex Trunks.Access lines mostly attached to ATM switches, and "ATM capable"
routers, FR switches, TD Muxes, & cross connects.
Circuit Switch TDM Trunking(Eighties 'Private Line' Network Model)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 BackboneCarrier 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)
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 NetworkHybrid 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 RateVoice 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
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 Rate
OfferedTraffic Mix
Switched Network Carrying CapacitiesHybrid Network
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 Rate
OfferedTraffic Mix
Switched Network Carrying CapacitiesHybrid Network
Switched Network Carrying CapacitiesHybrid Network
Carrying Capacity Hybrid
no data traffic groomed onto packet network
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed Rate
OfferedTraffic Mix
Switched Network Carrying CapacitiesHybrid Network
Switched Network Carrying CapacitiesHybrid Network
Carrying Capacity
real world network
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed Rate
OfferedTraffic Mix
Switched Network Carrying CapacitiesConvergence
Switched Network Carrying CapacitiesConvergence
Carrying Capacity
Circuit Switch TDM
Packet Switch StatMux
Cell Switch StatMux
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed Rate
OfferedTraffic Mix
70’s & 80’s Fixed Rate Voice Dominates70’s & 80’s Fixed Rate Voice Dominates
Voice
Data
time70’s & 80’s
Switched Network Carrying CapacitiesConvergence
Switched Network Carrying CapacitiesConvergence
Carrying Capacity
Circuit Switch TDM
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed Rate
OfferedTraffic Mix
Turn of the CenturyA Mixed Traffic EnvironmentTurn of the CenturyA Mixed Traffic Environment
Voice
Data
time2000
Switched Network Carrying CapacitiesConvergence
Switched Network Carrying CapacitiesConvergence
Carrying Capacity
Cell Switch StatMux
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed Rate
OfferedTraffic Mix
Switched Network Carrying CapacitiesConvergence
Switched Network Carrying CapacitiesConvergence
Carrying Capacity
Packet Switch StatMux
0% Bursty 100% Bursty100% Fixed Rate 0% Fixed Rate
OfferedTraffic Mix
A Resolving Unknown...What impact will Video have?A Resolving Unknown...What impact will Video have? As video becomes dominant, is a packet switched statmux network best?As video becomes dominant, 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
• Having a few bits in error is better than a loss of 1460 bytesHaving a few bits in error is better than a loss of 1460 bytes
Carrying Capacity...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 TrendsWAN 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 – ATMOlder Carriers – HybridOlder Carriers – Hybrid
10's – Mostly Bursty Traffic10's – Mostly Bursty TrafficData Networks moving voice on the sideData Networks moving voice on the side
Example) Coding aMicrophone Output
Example) Coding aMicrophone Output
time (sec)
m(t) volts (air pressure)
Energy from about 500 - 3,500 Hz.
A/D ConvertorA/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 ConvertorA/D Convertor Telephone System uses PCMTelephone 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.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.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.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/sampleA/D Convertor. 2 bits/sample
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)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 bps64,000 bps
Compact DiskCompact 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 outputs one of 65,536 voltage levels for 1/44100th
secondsecond 705,600 bps705,600 bps
Sampling & Quantizing ExamplesSampling & 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
Sources of POTS delaySources 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 delaySources 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)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