ECEN5553 Telecom Systems
Dr. George Scheets
Week #8
Readings:
[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 = 10.37
A > 78, B > 64, C > 55, D > 46
Outlines
Received
due
8 October (local)
15 October (remote)
61 %
802.3 Ethernet Packet Format
Bytes: 6
MAC
Destination
Address
6
2
MAC
Source
Address
20
20
6-1460
4
IP
TCP
Data + Padding
CRC
Provider Backbone Bridge
Carrier Ethernet Packet (Simplified)
Bytes: 6
6
2
Carrier MAC
Carrier
Carrier
Destination MAC Source VLAN
Address
Address
Tag

6
6
2
MAC
MAC
Destination Source
Address Address
20
20
6-1460
4
IP
TCP
Data + Padding
CRC
Carrier Edge switches prepend customer
Ethernet frames with provider frames.
#
Carrier MAC addresses = # Carrier edge switches
Carrier Ethernet WAN/MAN
LAN
LAN
LAN
LAN
Ethernet
Switch
E1
LAN
LAN
LAN
LAN
Every Carrier Switch is an Edge Switch here.
LAN
Edge Switches learn MAC addresses of serviced end devices. E1
must learn Yellow & Orange MAC & VLAN addresses.
Carrier Ethernet Switching (Simplified)

Unicast packet arrives with unknown
customer destination MAC address
 Source
Carrier Edge Switch
Examines
Customer VLAN tag & source MAC address
Maps to
Carrier VLAN tag
Carrier Edge Switch MAC address
Appends Carrier Header
 Destination Carrier Edge Switch
Examines & Removes Carrier Header
Forwards based on Customer MAC address
Carrier Ethernet Switching (Simplified)

Broadcast packet arrives
 Source
Carrier Edge Switch
Examines
Customer VLAN tag & source MAC address
Maps to
Carrier VLAN tag
Carrier Edge Switch MAC address(es)
Appends Carrier Header
Selectively Floods
 Destination Carrier Edge Switch
Examines & Removes Carrier Header
Forwards based on Customer VLAN
Carrier Ethernet Status

2009 U.S. Market Revenue $1.5 Billion
 2010
$3.2 Billion
 2013 $5.5 Billion
 2016 $11.1 Billion (projected)
 2018 $13 Billion (projected)

Backhaul from wireless cell sites a major
growth area
source: www.accedian.com
www.telecompetitor.com
MAN/WAN Connectivity Options

Carrier Ethernet
 Switches
 I/O
are Ethernet frame aware
decisions based on Layer 2 Ethernet Address
 Virtual
Circuits can be used
 StatMux
 BW
required based more so on average input rates
 Pricing
function of peak rate, CIR, priority, and
maybe distance
 On the way in.
 21st
century version of Frame Relay
Carrying Capacity
Line Speed
Active
Idle
Application Traffic Overhead
Carrying Capacity = Traffic(bps)/Line Speed(bps)
Goodput = Application Traffic Carried (bps)
Queue Length
100,000,000 bps output trunk
 100,000,001 bps average input
 Average Input rate > Output rate
 Queue Length builds up
(without bound, in theory)

Queue Length
100,000,000 bps output trunk
 99,999,999 bps average input
 Average Input rate < Output rate
 Queue Length not infinite...
...but very large

Queue Length @ 100% Load
Output capacity = 7 units
Input = 7 units on average (two dice rolled)










t1: input = 4, output = 4, queue = 0
t2: input = 5, output = 5, queue = 0
t3: input = 4, output = 4, queue = 0
t4: input = 7, output = 7, queue = 0
t5: input = 11, output = 7, queue = 4
t6: input = 10, output = 7, queue = 7
t7: input = 6, output = 7, queue = 6
t8: input = 5, output = 7, queue = 4
t9: input = 8, output = 7, queue = 5
t10: input = 11, output = 7, queue = 9
This queue will tend to get very large over time.
Queue Length @100% Load
Will tend to increase w/o Bound.
34000
3.40910
queue5  j2000
0
0
0
0
2 10
4 10
5
5
6 10
8 10
5
j 5
1 10
6
110
5
6
32000
1.98310
queue5  j1000
0
0
0
0
2 10
5
4 10
5
6 10
5
j 5
8 10
5
1 10
6
110
6
"Die Roll" Queue Lengths
101% Load
34000
3.40910
100% Load
queue5  j2000
99% Load, Average Queue = 44.46
0
0
0
0
2 10
5
4 10
5
6 10
5
j 5
8 10
5
1 10
6
110
6
Real vs Artificial Trace
10 Seconds
Real 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 Trace
100 Seconds
Real Traffic
100 Seconds
Artificial M/M/1 Traffic
Real vs Artificial Trace
16.7 Minutes
Real Traffic
16.7 Minutes
Artificial M/M/1 Traffic
Real vs Artificial Trace
167 Minutes
Real Traffic
167 Minutes
Artificial M/M/1 Traffic
Real vs Artificial Trace
27.78 Hours
Real Traffic
27.78 Hours
Artificial M/M/1 Traffic
Self Similar Behavior
Infinite Length Queue
(Classical StatMux Theory)
Probability of
dropped packets
Average Delay for
delivered packets
0%
Trunk Offered Load
100%
Finite Length Queue
(Real World StatMux)
Probability of
dropped packets
Average Delay for
delivered packets
0%
Trunk Offered Load
100%
You could fully load StatMux trunk lines... but your
customers would be screaming at you due to lousy service.
Switched Network
Carrying Capacity
 Line Speed: Traffic injection speed
 Efficiency: Ability to use that Line Speed
 Throughput: bps of traffic (+ overhead) moved
 = Efficiency * Line Speed
 Carrying Capacity: Ability to usefully use Line Speed
 Accounts for packet overhead
 Accounts for inability to fully load trunk lines with
StatMux'd traffic & still have a usable connection
 Goodput: bps of application traffic moved
 = Carrying Capacity * Line Speed
Carrying Capacity
Line Speed
Active
Traffic
Idle
Overhead
Carrying Capacity = (%Trunk Load) * (%Traffic)
= Traffic(bps)/Line Speed(bps)
Packet Switch StatMux Trunking
(Pure Internet Model)
Fixed Rate Traffic
Bursty Data Traffic
Router
SONET & OTN
Assumptions:
All Fixed Rate Traffic is packetized.
All traffic is Statistically Multiplexed onto the trunk BW.
Internet Service Provider Backbone
Packet
Aware
Router
StatMux, Packet Switched Network, Full Duplex Trunks.
Access lines mostly attach to routers.
ATM Trunking
(In Nineties, claimed as Tomorrow's Network Model)
Fixed Rate Traffic
Bursty Data Traffic
ATM
Switch
SONET OC-N
Assumptions:
Fixed Rate Traffic gets CBR Virtual Circuits.
CBR traffic gets near-TDM like service.
Data Traffic is StatMuxed onto the remaining trunk BW.
ATM Backbone
Cell
Aware
ATM Switch
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)
Fixed Rate Traffic
TDM
Switch
Bursty Data Traffic
Fiber, Cable,
& Microwave
Assumptions:
All Traffic receives trunk bandwidth based on peak
input rates.
No aggregation. Data traffic consists of many slower
speed, relatively lightly loaded circuits.
Carrier Leased Line Backbone
Byte
Aware
Cross-Connect
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)
Fixed Rate
Bursty Data
Packet
Switch
TDM
Switch
SONET
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.
Hybrid Network
Byte
Aware
Cross-Connect
Fixed Rate Traffic: CSTDM bandwidth based on Peak Rates
Bursty Traffic: Access lines aggregated onto higher load trunk.
Packet Switch StatMux Trunks are CSTDM.
Voice Quality vs. Bit Rate
Quality
G.729
G.728
G.726
G.711
G.723.1
8
16
32
Bit Rate (Kbps)
64
Switched Network Carrying Capacities
High Speed Trunk
Hybrid
Carrying
Capacity
Cell Switch
StatMux
Packet Switch
StatMux
Circuit Switch
TDM
0% Bursty
100% Fixed Rate
Offered
Traffic Mix
100% Bursty
0% Fixed Rate
Switched Network Carrying Capacities
Hybrid Network
Carrying
Capacity
all bursty data traffic groomed onto
packet network
Hybrid
Circuit Switch
TDM
0% Bursty
100% Fixed Rate
Offered
Traffic Mix
100% Bursty
0% Fixed Rate
Switched Network Carrying Capacities
Hybrid Network
Carrying
Capacity
Hybrid
no data traffic groomed onto
packet network
0% Bursty
100% Fixed Rate
Offered
Traffic Mix
100% Bursty
0% Fixed Rate
Switched Network Carrying Capacities
Hybrid Network
Carrying
Capacity
real world network
0% Bursty
100% Fixed Rate
Offered
Traffic Mix
100% Bursty
0% Fixed Rate
Switched Network Carrying Capacities
Convergence
Carrying
Capacity
Cell Switch
StatMux
Packet Switch
StatMux
Circuit Switch
TDM
0% Bursty
100% Fixed Rate
Offered
Traffic Mix
100% Bursty
0% Fixed Rate
70’s & 80’s Fixed Rate Voice Dominates
Data
Voice
70’s & 80’s
time
Switched Network Carrying Capacities
Convergence
Carrying
Capacity
Circuit Switch
TDM
0% Bursty
100% Fixed Rate
Offered
Traffic Mix
100% Bursty
0% Fixed Rate
Turn of the Century
A Mixed Traffic Environment
Data
Voice
2000
time
Switched Network Carrying Capacities
Convergence
Carrying
Capacity
0% Bursty
100% Fixed Rate
Cell Switch
StatMux
Offered
Traffic Mix
100% Bursty
0% Fixed Rate
Today, Data Dominates
Data
Voice
time
2012
Switched Network Carrying Capacities
Convergence
Carrying
Capacity
Packet Switch
StatMux
0% Bursty
100% Fixed Rate
Offered
Traffic Mix
100% Bursty
0% Fixed Rate
A Resolving Unknown...
What impact will Video have?

As video becomes dominant, is a packet switched
statmux network best?
 Yes.

Most video coders are variable rate.
Two changes to make the network more video
friendly…
 Might
be a good idea to increase Ethernet's maximum
packet size.
 All packets with bit errors shouldn't be dropped
 Voice/Video dropped packet = lower quality
 Better quality possible if payload delivered
• Having a few bits in error is better than a loss of 1460 bytes
Carrying Capacity...
 Got bursty data traffic to move?
A packet switched system using statistical
multiplexing will allow you to service the most
users given a fixed chunk of bandwidth.
 Got fixed rate traffic to move?
A circuit switched system will allow you to
service the most customers given a fixed chunk
of bandwidth.
WAN Trends
 60's
- Fixed Rate Voice Dominates
 Voice Network moving data on the side
 Mid to Late 90's – Mixed Traffic Environment
 New Carriers – ATM
 Older Carriers – Hybrid
 10's – Mostly Bursty Traffic
 Data Networks moving voice on the side
Example) Coding a
Microphone Output
m(t) volts (air pressure)
time (sec)
Energy from about 500 - 3,500 Hz.
A/D Convertor
m(t) volts (air pressure)
1/8000 second
time (sec)
Step #1)
Sample the waveform at rate > 2*Max Frequency.
Telephone voice is sampled at 8,000 samples/second.
A/D Convertor

Telephone System uses PCM

Pulse Code Modulation
One of N possible equal length Code
Words is assigned to each Voltage
N Typically a Power of 2
Log2N bits per code word
 Wired
Phone System: N = 256 & 8 bits/word
 Compact Disk: N = 65,536 & 16 bits/word
A/D Convertor. 1 bit/sample.
Example) N = 2. Assign 0 or 1 to voltage.
3.62 v, output a 1
t1
time (sec)
0 < Voltage < +5v, Assign Logic 1
-5v < Voltage < 0, Assign Logic 0
Bit Stream Out = 1111110000111...
A/D Convertor. 1 bit/sample.
Example) N = 2. Assign 0 or 1 to voltage.
0 < Voltage < +5v, Assign Logic 1
-5v < Voltage < 0, Assign Logic 0
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
A/D Convertor. 1 bit/sample.
Input to the transmitter.
Output at the receiver.
+2.5 v
-2.5 v
Considerable Round-Off error exists.
A/D Convertor. 2 bits/sample
Example) N = 4. Assign 00, 01, 10 or 11.
3.62 v, Assign 11
+2.5 v
time (sec)
t1
2.5 < Voltage < 5 , Assign 11
0 < Voltage < 2.5, Assign 10
-2.5 < Voltage < 0, Assign 00
-5 < Voltage < -2.5, Assign 01
-2.5 v
Bit Stream Out =
11111011111100
000000101011...
A/D Convertor. 2 bits/sample.
Input to the transmitter.
Output at the receiver.
+3.75 v
+1.25 v
-1.25 v
Receive 11? Output 3.75v
Receive 10? Output 1.25v
Receive 00? Output -1.25v
Receive 01? Output -3.75v
Reduced Round-Off error exists.
-3.75 v
Circuit Switched Voice (POTS)
 Bandwidth
≈ 3,500 Hertz
 A/D Converter
 samples
voice 8,000 times/second
 rounds off voice to one of 256 voltage levels
 transmits 8 bits per sample to far side
 D/A
Converter
 receives
8 bit code word
 outputs one of 256 voltage levels for 1/8000th
second
 64,000
bps
Compact Disk
 Bandwidth
≈ 20,000 Hertz
 A/D Converter
 samples
voice 44,100 times/second
 rounds off voice to one of 65,536 voltage levels
 transmits 16 bits per sample to far side
 D/A
Converter
 receives
16 bit code word
 outputs one of 65,536 voltage levels for
1/44100th second
 705,600
bps
Sampling & Quantizing Examples
 fs
= 16 KHz
 4096
quantiles
 256 quantiles (approximate phone quality)
 32 quantiles
 4 quantiles (generally 2 levels used!)
 4096
 fs
quantiles
= 16 KHz
 fs = 8 KHz (some interference)
 fs = 2 KHz
 fs = 1 KHz
1/8th Second of Voice
1/8th Second of Voice
1/8th Second of Voice
Sources of POTS delay
Source CO
POTS
TDM Trunk TSI
Trunk resources are dedicated
to each voice call via TDM.
PCM
Coder
...
Local Loop
PCM
Coder
POTS
Local Loop
TDM Trunk TSI
Destination CO
Intermediate
Digital
Voice
Switches
Sources of VoIP delay
Voice
Packet Transmission
Coder Assembler
Buffer
Packet
Switch
...
Trunk resources are randomly assigned to
each voice call via Statistical Multiplexing.
Voice
Decoder
Receiver
Buffer
StatMux
Trunks
Intermediate
Packet
Switches
Packet
Switch
Voice (Video) on LAN (WAN)
 More complex system than circuit switched
voice
 Packet Assembler
 Transmitter Buffer
 Receiver Buffer
 End-to-End Delays > Circuit Switch TDM
 Delay Variability > Circuit Switch TDM