Opportunities and Challenges for
Optical Burst- and Packet- switching-
S. J. Ben Yoo, Fei Xue, et al.
Optical Switching and Communications Systems Lab
University of California, Davis
yoo@ece.ucdavis.edu
Progress in Optical Networks
Optical Add/Drop
Capacity
Optically Amplified
Optical Packet Switching
Optical Packet
Function
Optical Burst Switching
Dynamic
WDM
Single
ChannelCircuit Switching
Optical
Pt-to-Pt
Ring
Static
Mesh
Topology
2
Optical Burst Switching
3
Diff Serve OBS Performance
4
Throughput comparison OBS vs. OCS
Under the same network conditions, OBS networks can achieve
20%~30% more throughput than those in OCS networks.
5
Motivations for Optical Packet Switching
• Data-centric + High-Bandwidth
 Packet
+ Optical
• Sub-wavelength granularity
• Cost-effective service delivery and flexibility
• Avoid electrical RAM and O/E/O bottleneck
– DRAM getting faster only by 7%/year
– O/E/O conversion consumes power and space
• Scalability for future bandwidth growths
• Use optical parallelism for simpler switching
fabric
• From ATM/SONET to IP/WDM paradigm
6
Next Generation Network Overview
Optical Core Network
Edge
router
OLS
switches
OLS
switches
Edge
router
OLS
routers
Legacy
MAN
MAN
MAN
Edge router
Star Coupler
Wireline
O-CDMA LAN
7
Star Coupler
Free Space and Wireline
O-CDMA LAN
SENSOR
Networks
Legacy
LAN
DEMUX
Label Processing Module-TI
(LP-TI)
label
reader
Switch Controller
w/ Forwarding
Look-up Table
NC&M
Switching
Fabric
Label Processing
Modules-CI
(LP-CI)
OLS
Edge Router
fiber
delay
CI
CI
OLE OLR OLEOLR OLE OLR
IP Router
8
CI
UNAS
ATM
Client Machine
Conventional Electronic Packet Switches
controller
MAC
MAC
MAC
MAC
MAC
MAC
MAC
MAC
Buffer
Buffer
Memory
Buffer
Memory
Buffer
Memory
Memory
Buffer
Buffer
Memory
Buffer
Buffer
Memory
Buffer
Buffer
Memory
Memory
Buffer
Buffer
Memory
Memory
Buffer
Memory
Memory
Memory
• Buffer, Schedule, and Forward
• Electronic RAM--Diverse Functions
• Contention Resolution, Queuing, etc in Time
TIME
9
SPACE
Optical Switch Fabric used in UCDavis OLS core Routers
Tunable
Wavelength
Converters
controller
switch
control
l-router
(AWGR)
Fixed
Wavelength
Converters
T_WC
F_WC
T_WC
F_WC
T_WC
F_WC
T_WC
F_WC
WAVELENGTH
SPACE
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TIME
Rapid Tuning (~ 1 nsec) of T_WC
to achieve switching in
Wavelength, Time, Space domains
Scalable to 42 Petabit/sec capacity
32*(2562x2562) connectivity
Contention Resolution Algorithm
packet arrives
no
contention ?
yes
l cont. res.?
no
time cont. res.?
no
yes
yes
yes
space cont. res.?
no
Send to Edge Router
for cont. res. or drop
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forward
•S. Yao, S. J. B. Yoo, and B. Mukherjee, “A
comparison study between slotted and
unslotted all-optical packet-switched
network with priority-based routing,” OFC
2001, #TuK2
•S. Yao, S. J. B. Yoo, B. Mukherjee, S. Dixit,
“Hybrid contention resolution for an
optical packet-switched network with selfsimilar IP traffic,” APOC 2001 #4585-04.
• S. Yao, B. Mukherjee, S. J. Ben Yoo, and
S. Dixit, “All-optical Packet-switching for
Metropolitan Area Networks: Opportunities
and Challanges,” IEEE Comm. Magazine,
vol.39, p.142-8 (2001)
•S. J. B. Yoo, Y. Bansal, Z. Pan, J. Cao, V. K.
Tsui, S. K. H. Fong, Y. Zhang, J. Taylor, H.
J. Lee, M. Jeon, V. Akella, K. Okamoto, S.
Kamei, “Optical-Label Switching based
Packet Routing System with Contention
Resolution Capabilities in Wavelength,
Time, and Space Domains,” OFC 2002,
paper #WO2 (2002).
OLS Core and Edge Routers
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Optical Packet Assembly Mechanism
• Assemble a larger optical packet from IP
packets based on destination and QoS
• The creation of an optical packet:
– Reach the Maximum Payload Size (MPS)
– Expiration of Assembly Time-out Period (T)
MPS
13
Optical Packet Assembly Mechanism
• Assemble a larger optical packet from IP
packets based on destination and QoS
• The creation of an optical packet:
– Reach the Maximum Payload Size (MPS)
– Expiration of Assembly Time-out Period (T)
MPS
14
Optical Packet Assembly Mechanism
• Assemble a larger optical packet from IP
packets based on destination and QoS
• The creation of an optical packet:
– Reach the Maximum Payload Size (MPS)
– Expiration of Assembly Time-out Period (T)
MPS
15
Optical Packet Assembly Mechanism
• Assemble a larger optical packet from IP
packets based on destination and QoS
• The creation of an optical packet:
– Reach the Maximum Payload Size (MPS)
– Expiration of Assembly Time-out Period (T)
MPS
16
Optical Packet Assembly Mechanism
• Assemble a larger optical packet from IP
packets based on destination and QoS
• The creation of an optical packet:
– Reach the Maximum Payload Size (MPS)
– Expiration of Assembly Time-out Period (T)
MPS
17
Optical Packet Assembly Mechanism
• Assemble a larger optical packet from IP
packets based on destination and QoS
• The creation of an optical packet:
– Reach the Maximum Payload Size (MPS)
– Expiration of Assembly Time-out Period (T)
MPS
18
Traffic Shaping at the Edge Routers
Packet length distribution at the Client and at the Core
client
19
transport
Packet-loss rates for networks with various number of l
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IP Client-to-IP Client with Cascaded Operation of OLSRs
Edge Router
Ingress
Path
Egress
Path
Encapsulation
Label processing Unit
Data bus traffic controller
AOLS Interface
Physical Layer Interface
Optical Label Switching Network
L1, L2
P1, P2
Label
Core
Router
Payload
L1
P1
Data Bus
SONET
Physical Layer Interface
P1,P2, P3
POS Interface
Data bus traffic controller
PPP
Core
Router
L1, L2, L3
P1, P2, P3
L3
P3
Edge
Router
Core
Router
L2
P2
Edge
Router
P1
IP Client
Network
IP Client
Network
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Possible Network Evolution Scenario
Electronic
ATM Network
Electronic
IP Network
LAN
22
Electronic
IP Network
LAN
Possible Network Evolution Scenario
Electronic
MPLS
Network
Electronic
IP Network
LAN
23
Electronic
IP Network
LAN
Possible Network Evolution Scenario
MPLambdaS
Network
Electronic
MPLS Network
LAN
24
Electronic
MPLS Network
LAN
Possible Network Evolution Scenario
Optical Label
Switched
Network
Electronic
MPLS Network
LAN
25
Electronic
MPLS Network
LAN
Possible Network Evolution Scenario
Electronic
MPLS Network
MPlS Network
Electronic
MPLS Network
Optical Label
Switched
Network
GMPLS II
Electronic
MPLS Network
Electronic
MPLS Network
LAN
LAN
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LAN
Summary
• Optics provides capacity, packet switching
provides flexibility and fine granularity
• Optical Label Switching Provides
interoperability in Packet, Burst, and Circuit
switching
• Unified contention resolution in wavelength,
time, and space domain.
• Edge router function critical in performance
enhancement and traffic shaping
• Seamless network evolution from today’s
circuit-switching to tomorrow’s burst- and
packet- switching
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