The document discusses optical burst switching (OBS) network principles and key technologies, including burst assembly, signaling and resource reservation protocols, scheduling algorithms, and contention resolution methods. It covers topics such as timer-based and burstlength-based assembly, TAW, TAG, and offset-based signaling approaches, and scheduling algorithms like LAUC, Min-SV, and Best-Fit. The document provides an overview of the technical challenges in developing OBS networks.

1. OBS
Network principles
& key technologies
Shaozhong Zheng 2010-10-18
Dept. of Electronic Engineering, Tsinghua Univ.
Dept. of EE, Tsinghua Univ.
Laboratory of Broadband optical network
Tel: 86-10-62773197
zhengsz04@gmail.com

2. Outline
1. 2.
Background Principles
4. 3.
News Key technologies
2

3. Outline
1. 2.
Background Principles
4. 3.
News Key technologies
3

4. Outline
Background
OFC 2005
UC Davis
Optical Label Switching
Network testbed
2.5Gb/s
multicast and unicast
video streaming
4

5. Outline
Background
OBS
5

6. Outline
Background
OPS
6

7. Outline
Optical Background
Packet
Switch
OPS
Why we need OPS?
7

8. IP Router Outline
Peer Routing Background
ATM Swtich
PVC Mesh
SONET
ADM Ring A typical data network
4-layer
Using Telecomm. Network
Shortcomings :
DWDM 1、complicated, bad flexibility
Point-point 2、 bandwidth bottlenecks
3、 High energy consumption
8

9. Outline
Background
Power Consumption in Routers
9

10. Outline
Background
Power Consumption in Routers
Through-put 92Tbps
1.2Tbps >1Mw
Power
Consumption Google Data Center
15kw >100Mw
10

11. Outline
Background
IP/MPLS
ATM IP/MPLS
SONET SONET IP/MPLS
WDM WDM WDM
Time
Flat network architecture
IP over WDM
11

12. Outline
Another Trend… Background
ASON
Added complex electronic
Optical
control layer Packet
Wavelength Switching
Representative : SDH routing
Optical technologies Wavelength
Network Function
only Used for transport conversion
OXC and DXC
co-existence
Colored section
rings
Dynamic OADMs
DWDM STM1 on demand
e-g-
point-to-multipoint
Static
Point-to-point
WDM &DWDM
Optical
amplifiers
Packet-level
High-capacity Optical Networking Flexibility
1994 2000 2007 Time
12

13. Outline
Another Trend… Background
ASON
Added complex electronic
Optical
control layer Packet
Wavelength Switching
Representative : SDH routing
OPS
Optical technologies Wavelength
Network Function
only Used for transport conversion
OXC and DXC
co-existence
Colored section
All-Optical Routing
Dynamic OADMs
rings
Optical Packet
DWDM STM1 on demand
e-g-
point-to-multipoint
Point-to-point
WDM &DWDM
Flexible & Efficient
Static
Optical
amplifiers
Packet-level
High-capacity Optical Networking Flexibility
1994 2000 2007 Time
13

14. Outline
Background
14

15. Outline
Optical Background
Packet
Switch
15

16. Outline
Optical Background
Burst
Switch
Challenge:
High-speed Optical switch
Optical RAM
16

17. Outline
Optical Background
Burst
Switch
Solution:
Packet-aggregating
Separation of
Data& Control signals
17

18. Control
Unit Outline
Background
OPS
Switch Speed: n s
Control
Unit
OBS
Switch Speed: m s
18

19. Control
Unit Outline
Background
OPS
Switch Speed: n s
Proponent of OBS, S. J. B. Yoo:
Optical burst switching (OBS) is implemented
either as a fast reconfiguring optical circuit
Control
Unit
switching (OCS) or as OPS with large aggregated
packets.
OBS
Switch Speed: m s
19

20. Outline
1. 2.
Background Principles
4. 3.
News Key technologies
20

21. Outline
Core Node Edge Node OpticalBurst Background
Principle
1010101
1010101
21

22. Outline
Background
Principle
Control : Burst head
Transport: Burst
22

23. Outline
de M Background
mu
x
U
X
Principle
Switch
Matrix
Optical
Label
process FDL Buffer
Burst Transmitter Burst Receiver
Electronic
Framing Defaming
Buffer
Burst Assembly/Disassembly Unit
23

24. Outline
1. 2.
Background Principles
4. 3.
News Key technologies
24

25. Outline
Background
Principle
Technologies
Burst Assembly Contention Resolution
Signaling &
Resource Reservation Key QoS Technologies
Technologies
Scheduling Switching
25

26. Outline
Background
Principle
1. Burst Assembly Technologies
The procedure of aggregating packets
from various sources into bursts.
Burst Assembly/Disassembly.
Timer-based
Burstlength-based
Mixed timer/burstlength-based
26

27. 1. Burst Assembly Outline
Background
Burst Assembly Unit Principle
Technologies
Class 1
Packets to
……
the same
Class n
destination
Assembly
algorithms
…… Principles
Arriving Data …… ……
……
of Edge
streams
Nodes
Switch Unit
27

28. Outline
1.1. Timer-based Background
Principle
Technologies
Advantages: guarantee on the assembly delay
Disadvantages: No guarantee on the burst length
Burst
Length
Other Other
SONET
SONET
ATM ATM ATM ATM
GbE GbE GbE GbE GbE
IP IP IP IP IP IP Time
T
28

29. Outline
1.2. Burstlength-based Background
Principle
Technologies
Other2
Other1
SONET Advantages: guarantee on the burst length
Burst ATM Disadvantages: No guarantee on the assembly delay
Length GbE
IP
Other2
L
Other1 Other1
SONET SONET SONET
ATM ATM ATM ATM
GbE GbE GbE GbE GbE
IP IP IP IP IP IP Time
29

30. Outline
1.3. Mixed timer Background
Principle
/burstlength-based Technologies
Burst
Length
L Other1
Other1
SONET
SONET SONET
ATM ATM ATM ATM
GbE GbE GbE GbE GbE
IP IP IP IP IP IP Time
T
30

31. Outline
1.3. Mixed timer Background
Principle
/burstlength-based Technologies
Burst
Length
Address the deficiency associated
with the assembly algorithms
L
mentioned above SONET
Other 1
Other 1
SONET SONET
ATM ATM ATM ATM
GbE GbE GbE GbE GbE
IP IP IP IP IP IP Time
T
31

32. Outline
1.4. Impact of burst length Background
Principle
Technologies
32

33. Outline
1.4. Impact of burst length Background
Principle
Technologies
Generally,
the average length of burst is
40Kbyte,
approximately
33

34. Outline
Background
Principle
2. Signaling & Technologies
Resource Reservation
Generation and transmission of a burst
header packet to reserve network resources
and to configure switches
JET protocol
JIT protocol
34

35. Outline
2.1. Signaling Background
Principle
Generation and transmission Technologies
of a burst header packet
Destination Node
Burst length
……
TAW approach
TAG approach
offset-based approach
35

36. Outline
2.1. Signaling - TAW Background
Principle
TAW : Tell and wait Technologies
Low efficiency T
Source Time
Destination
Time
Burst Head Acknowledgement Burst
36

37. Outline
2.1. Signaling - TAW Background
Principle
TAW : Tell and wait Technologies
Low efficiency T
Source Time
Advantage: Low Burst-loss rate
Disadvantage: High delay, low
bandwidth-efficient
Destination
Time
Burst Head Acknowledgement Burst
37

38. Outline
2.1. Signaling - TAG Background
Principle
TAG：Tell and go Technologies
Source Time
Buffer
the Burst
Destination
Time
Burst Head Burst
38

39. Outline
2.1. Signaling - TAG Background
Principle
TAG：Tell and go Technologies
Source Time
Advantage: Low Delay
Disadvantage: No guarantee on reservation,
Buffer
the Burst
Optical buffer
Destination
Time
Burst Head Burst
39

40. Outline
2.1. Signaling - Offset Background
Principle
The header and burst are separated Technologies
by an offset time.
Offset time T
Source Time
Destination
During the offset time, intermediate Time
nodes process the header and
configure the switch prior to the
burst’s arrival.
Burst Head Burst
40

41. Outline
2.1. Signaling - Offset Background
Principle
The header and burst are separated Technologies
by an offset time.
Offset time T
Source Time
A balance
Hard to determine an perfect
Destination
offset time
During the offset time, intermediate Time
nodes process the header and
configure the switch prior to the
burst’s arrival.
Burst Head Burst
41

42. TAW approach TAG approach Offset-time
•The Burst is sent •The Burst and the •The Burst and the
only after resource head are sent head is separated by
reservation is together. an offset time.
successful.
•Advantage •Advantage •A balance between
Low burst-loss rate Low delay; Simple; network delay and
the burst-loss rate.
•Disadvantage •Disadvantage
High network delay; Low delay;
Low efficiency. Simple;
42

43. Outline
2.2. Reservation Background
Principle
The reservation technique determines Technologies
the starting time of the reservation and
determines how and when the reservation
should be released.
Delayed reservation: reserves the resources
starting from the point in time at which the burst
is expected to arrive at the node.
Immediate reservation: reserves the resources
immediately after the burst header is processed.
43

44. Outline
Reservation Protocol Background
Principle
JET Protocol & JIT Protocol Technologies
JET = Time-offset + Delay Reservation
Just Enough Time
JIT = TAG + Immediate reservation
Just In Time
44

45. Outline
Background
Principle
3. Scheduling Technologies
A scheduler chooses a proper wavelength taking
into consideration the existing reservations and
make a new reservation on this selected channel.
LAUC
Min-SV
Min-EV
Best-Fit
45

46. LAUC: latest available unscheduled channel Outline
Background
New Burst
Principle
Technologies
C1
s1 t1
C2
s2 t2
C3
s3
C4
s4 t4
C5
s5 t5
Time
46

47. LAUC: latest available unscheduled channel Outline
Background
Principle
Technologies
C1
C2
C3
C4
C5
Time
47

48. LAUC: latest available unscheduled channel Outline
Background
Principle
Technologies
C1
C2
Advantages: simple C 3
Disadvantage: Low bandwidth efficiency
C 4
Make use of the voids among bursts
C5
Time
48

49. LAUC –VF:带空隙填充的LAUC Outline
Background
New Burst
Principle
Technologies
C1
s1 t1
C2
s2 t2
C3
s3
C4
s4 t4
C5
s5 t5
Time
49

50. LAUC –VF:带空隙填充的LAUC Outline
Background
New Burst
Principle
Technologies
C1
s1 t1
C2
s2 t2
C3
s3
Optimized
using computer
C4
t4 graphics
s4
O(WlogM) ->
O(logM) C5
s5 t5
Time
50

51. Min-SV Outline
A faster LAUC-VF Background
Principle
Technologies
New Burst C1
s1 t1
C2
s2 t2
C3
s3
C4
s4 t4
C5
s5 t5
Time
51

52. Min-EV Outline
Background
New Burst
Principle
Technologies
C1
s1 t1
C2
s2 t2
C3
s3
C4
s4 t4
C5
s5 t5
Time
52

53. Best-Fit Outline
Background
New Burst
Principle
Technologies
C1
s1 t1
C2
s2 t2
C3
s3
C4
s4 t4
C5
s5 t5
Time
53

54. New Burst LAUC-VF
Outline
/Min-SV Background
C1
Principle
s1 t1
Technologies
C2
s2 t2
LAUC
C3 /Horizon
s3
C4 Min-EV
s4 t4
C5 Best-Fit
s5 t5
Time
54

55. Outline
Comparison Background
Principle
Technologies
Algorithms Time complexity Bandwidth Utilization
LAUC O(W) Low
LAUC-VF O(WlogM) High
Min-SV/EV O(logM) High
Best-Fit O(log2M) High
W: Number of wavelengths at each output port
M: Maximum number of data bursts (or reservations) on all channels
55

56. Outline
Background
4. Contention Principle
Technologies
Resolution
Owing to the one-way reservation mechanism,
bursts that contend for the same resources may
end up being lost.
Node level: conflict resolution
System level: reduce the conflict
Network level: avoid conflict
56

57. Outline
4.1. Background
Principle
conflict resolution Technologies
Optical buffer
Store and Forward
A challenge to develop an mature Optical RAM
Wavelength conversion
Multi-wavelength resolution
Much lower burst loss
Immature and expensive technology
57

58. Outline
Background
4.1. Principle
Technologies
Contention Resolution
Deflection Routing
diverts bursts to alternate available
output ports when contention occurs
Out of order arrivals;
Possible instability;
Optical buffers needed.
58

59. Outline
4.2. Background
Principle
Reduce conflict Technologies
Slotted OBS network
Synchronizing network;
Mechanisms to provide synchronization
at each node;
fixed-length bursts
Contention control
Attempt to prevent contention
59

60. Outline
4.4. Background
Principle
Avoid Conflict Technologies
Zero-burst-loss OBS
Buffer the data in edge nodes
Network structure: Ring and Star
60

61. Outline
Background
Principle
5. QoS Technology Technologies
QoS mechanisms typically provide differentiation
with respect to data loss or delay.
Assembly process
Signaling Mechanism
Scheduling algorithms
Contention resolution
61

62. Outline
Background
Principle
QoS Technology Technologies
Assembly process
Changing the assembly thresholds will affect the
delay experienced by packets, allowing for delay
differentiation.
Resource Reservation
Longer interval between head and burst, lower
burst-loss rate
62

63. Outline
Background
QoS Technology Principle
Technologies
Scheduling algorithms
Preemption mechanisms allow high-priority bursts to preempt
already scheduled low-priority bursts;
Early drop mechanisms prevent the scheduling of low-priority
bursts;
Wavelength allocation schemes restrict the number of wave-
length channels that can be used for bursts of a given priority.
Contention Resolution
Drop the low-priority bursts
63

64. Outline
Background
Principle
6. Switching Technologies
A critical component in OBS is the
optical switch fabric.
Space Switching
Wavelength conversion
64

65. Outline
6.1. Switching-Space Background
Principle
Using the Optical Switch Matrix Technologies
to exchange optical bursts.
Optical
Input Switch
Matrix
MEMs
SOA
Output
65

66. Outline
6.1. Switching-MEMs Background
Principle
Matrixes consist of numbers of Technologies
tiny lenses.
MEMs： microelectromechanical systems
66

67. Outline
6.1. Switching-MEMs Background
Principle
Matrixes consist of numbers of Technologies
tiny lenses.
MEMs： microelectromechanical systems
Advantages: Mature IC technologies;
Disadvantages: Slow switching speed,
1~10ms
67

68. Outline
6.1. Switching-SOA Background
Principle
SOA： semiconductor optical amplifier Technologies
Input Optical
SOA Output Optical
power power
Injection
current
High-speed Optical swtich 68

69. Outline
6.2. Switching-AWG Background
Using wavelength technologies to exchange Principle
optical bursts. Technologies
AWG: Arrayed Waveguide Grating
Principle: Using star coupler and AWG to separate different
wavelengths into different outputs.
n non-coupled linear array of waveguides
Star Star
coupler coupler
l 1 .... N
l l 1 .... N
l
input output
69

70. Outline
6.2. Switching-AWG Background
Using wavelength technologies to exchange Principle
optical bursts. Technologies
AWG + Wavelength conversion = Wavelength Switching
70

71. Outline
Background
Principle
Other Technologies
TCP over OBS
OBS multicast
OBS grid calculation
……
71

72. Outline
1. 2.
Background Principles
4. 3.
News Key technologies
72

73. Outline
Background
Principle
News Technologies
News
Key elements
New network structures
Important test beds around the world
73

74. Key elements - Optical integration
Outline
Background
2010, Larry A. Coldren (UCSB university, USA) has Principle
demonstrated an 8x8 InP-based monolithic tunable Technologies
optical router capable of 40 Gbps operation per port. News
74

75. Key elements - Optical integration
Outline
Background
Integrated Optical switches Principle
The COBRA Research Institute, Eindhoven University of Technologies
Technology, Netherlands, developed an integrated SOA- News
based optical switches.
Integrate 4
SOA optical
switches;
160Gbit/s;
75

76. Key elements- Optical buffer Outline
Background
Principle
Optical RAM，K. Kitayama， ACP 2009 Technologies
News
Developed optical Flip-Flops based on optical Bistability
using high-Q photonic crystal nano-cavity.
Transform energy: 30 fJ/bit
Minimum optical bias power: 40μW
Storage time 150 ns (Under the bias power 250 μW)
76

77. Thank you!
Shaozhong Zheng
Dept. of Electronic Engineering, Tsinghua Univ.
2010-10-18
Dept. of EE, Tsinghua Univ.
Laboratory of Broadband optical network
Tel: 86-10-62773197
zhengsz04@gmail.com