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Segmentation Based
Nonpreemptive Channel
Scheduling Algorithms for Optical
Burst-Switched Networks
Adviser : Ho-Ting Wu
Speaker : Chih-Hao Tseng
Outline
Introduction
Optical Burst Switched (OBS)
Segmentation-Based Nonpreemptive
Scheduling Algorithms with FDL
Conclusion
Future Optical Networks
Amount of network data traffic exceeded
that of video/voice traffic
Currently being developed to satisfy an
increasing diversity of users with greatly
differing service requirements
Evolution of transport and service bit
rates.
Requirement
2000->2003, the volume of data grew from
3 billion to 24 billion
93% being born digitally
Traditional services and industries move
from analog to digital. (eg. TV
broadcasting , movie making ….)
Residential, business users, scientific
users…
RESIDENTIAL SERVICE
REQUIREMENTS
Convergence of Service
 Transmission and Switching might be based on
optics
 Realization of optical amplifiers allowing
 Economic deployment of wavelength division
multiplexing (WDM)
 Demonstration of an OXC enabling the rapid
reconfiguration of light-paths based on
wavelength channels
 Convergence of service and transport
transmission rate
Schematic of telecommunications
network.
OOO/
Move Toward Pervasive and Ubiquitous
networks --- Regional Plans
Ubiquitous network society = Ambient
intelligence
The ability and flexibility to interface and
integrate multiple technologies and service
requirement
Reliability and Security
Evolution Toward National Optical
Telecommunication Networks
Transmission Speed
Network Switching
Access PONs (Passive Optical Network)
attempt to eliminate the "last mile" gap between
many businesses and high-speed optical
networks
a set of splitters chops wavelengths of light into
time slots so that each wavelength can be
shared by a number of end users
Network evolution.
Desired technology
All-optical regeneration/conversion
Optical monitoring
Fast optical switch fabrics
Optical buffers
Increased level of integration
Outline
Introduction
Optical Burst Switched (OBS)
Segmentation-Based Nonpreemptive
Scheduling Algorithms with FDL
Conclusion
Key Network Technology
Optical Circuit Switching
Optical Packet Switching
OCDMA
Optical Burst Switching
Optical Circuit Switching (OCS)
Node design like ROADMs based on
WSSs
Control planes for dynamic networking,
channel provisioning, management based
on IP/MPLS solutions.
Optical Packet Switching (OPS)
A WDM optical packet network consists of
optical packet switches interconnected by
WDM fiber links.
Optical packet switches operate in a
slotted manner.
An optical packet are fixed-sized in time,
but the actual transmission rate may vary,
i.e., the packet size may vary
Optical Packet Switching (OPS)
 A WDM optical packet switch consists of the
following four parts:
input interfaces
the switching fabric
output interfaces, and
the control unit.
hdr
payload
CPU
hdr
payload
hdr
payload
Wavelength i
input port j
Re-combined
Wavelength i
output port j
Optical
packet
Optical switch
OCDMA
Optical Code Division Multiple Access
An Alternative networking solution able to
increase passively the number of users
per wavelength
Other solution is OTDM, but this requires
active processing.
Optical Burst Switching (OBS) 1/6
 Based on the ATM block transfer(ABT)
＊Connection-oriented packet-switched
＊Fixed cell size of 48+5 byte
Header
Pay load
5 bytes
48 bytes
＊No error protection on a link by link
＊No flow control on a link by link
＊Delivers cells in the order in which they were transmitted
 Optical burst switching is a new technology that it is
currently under study. It has not as yet been
commercialized.
 Unlike optical packet switching, it does not require
optical buffering.
 It can be seen as lying between optical packet
switching and wavelength-routing networks.
Optical Burst Switching (OBS) 2/6
 An OBS network consists of OBS nodes interconnected
with WDM fiber in a mesh topology.
 An OBS node is an OXC which has a very low
configuration time, due to the fact that connection do not
stay up for a long time.
Control Unit
Input
WDM
fibers
Switch
fabric
Output
WDM
fibers
OBS transport network architecture
Optical Burst Switching (OBS) 3/6
End-device
End-device
A
SETUP
B
Burst
SETUP
Burst
offset
time
Main features of OBS networks
Optical Burst Switching (OBS) 4/6
SETUP
SETUP ACK
KEEP ALIVE
RELEASE
CONNECT
FAILURE
A
B
SETUP
SETUP
ACK/FAILURE
SETUP
SETUP
Burst
Time
RELEASE
(Optional)CONNECT RELEASE
RELEASE
Optical Burst Switching (OBS) 5/6
(For persistent connection)
 SESSION DECLARATION
 DECLARATION ACK
 SESSION RELEASE
A
B
SESSION
SESSION
DECLARATION
DECLARATION
Persistent
SESSION
connection setup
DECLARATION
SESSION ACK
SESSION ACK
SESSION ACK
KEEP ALIVE
KEEP ALIVE
Data transfer
KEEP ALIVE
SESSION
RELEASE SESSION
SESSION
RELEASE
RELEASE
Tear down
Optical Burst Switching (OBS) 6/6
In order to mainly offer in creased
bandwidth utilization and reduced
overhead.
Set-up and tear down a path dynamically.
It can be bufferless, but it also needs a
switch reconfiguration speed in the order
of μsec.
Key Subsystems and Technologies
Optical Switching
Optical Monitoring
Optical Encryption
All-Optical Wavelength Conversion and
Regeneration
Optical memory
Introduction
Optical Burst Switched (OBS)
Segmentation-Based Nonpreemptive
Scheduling Algorithms with FDL
Conclusion
Nonpreemptive v.s. preemptive
 Nonpreemptive
Existing channel assignments are not altered
The BHP of the segmented unscheduled burst can be
immediately updated with the corresponding change in
the burst length and arrival time
 Preemptive
Preempted bursts my be rescheduled or dropped
 Tail dropping v.s. Head dropping
Be observed while incorporating QoS into channel
scheduling
 L b：
 tub：
 W：
Unscheduled burst length duration.
Unscheduled burst arrival time.
Maximum number of outgoing data
channels.
 Nb：
Maximum number of data bursts
scheduled on a data channel.
 Di：
ith outgoing data channel.
 LAUTi： LAUT of the ith data channel, i =
1,2, . . . , W, for non-void-filling
scheduling algorithms.
 S(i,j) and E(i,j) ： Starting and ending times of each scheduled burst
j
on every data channel i for void-filling scheduling algorithms.
 Gapi：If the channel is available, gap is the difference between tub
and LAUTi for scheduling algorithms without void filling, and is
the difference between tub and E(i,j) of previous scheduled
burst j for scheduling algorithms with void filling. If the channel
is busy, Gapi is set to 0. Gap information is useful to select a
channel for the case in which more than one channel is free.
 Void(i,k)：Duration of the kth void on the ith data channel. This
information is relevant to voidfilling algorithms. A void is the
duration between the S(i,j+1) and E(i,j) on a data channel.
Void information is useful in selecting a data channel in case
more than one channel is free.
Non-void-filling v.s. void-filling
Non-void-filling algorithms (FFUC & LAUC)
Void-filling algorithms (FFUC-VF & LAUC-VF)
FFUC & LAUC(Horizon)
 FFUC
Keeps track of the LAUT on every data channel
Searches all the channels in a fixed order and assigns
the first available channel for the new arriving burst
Time complexity is O(logW)
 LAUC
Keeps track of the LAUT on every data channel and
assigns the data burst to the latest available
unscheduled data channel
Time complexity is O(W)
FFUC-VF & LAUC-VF
FFUC-VF
The starting and ending times for each
scheduled data burst on very data channel
Utilize voids between two data-burst
assignments.
Time complexity is O(WlogNb)
LAUC-VF
Same with FFUC-VF
 Overlapi：Duration of overlap between the unscheduled
burst and scheduled burst(s). Overlap is used
in non-voidfilling channel scheduling
algorithms. The overlap is 0 if the channel is
available, otherwise, the overlap is the
difference between LAUTi and tub.
 Lossi：Number of packets dropped due to the
assignment of the unscheduled burst on the
ith data channel. The primary goal of all
scheduling algorithms is to minimize loss;
hence, loss is the primary factor for choosing a data
channel. In case the loss on more than one channel
is the same, then other channel parameters are
used to reach a decision on the selection of data
channel.
Nonpreemptive Minimum Overlapping
Channel (NP-MOC)



NP-MOC ALGORITHM (tub)
tempOverlap ← INFINITY;
tempGap ← INFINITY;
tempChannel←−1;
for each i ∈ Data Channel {
if (Overlapi is ZERO) and (Gapi < tempGap) {
tempGap ← Gapi;
tempChannel ← i;
}
}
if (tempChannel − 1) {
Schedule the Unscheduled Burst on Di;
Stop;
}
else {
for each i ∈ Data Channel {
if (Overlapi < tempOverlap)
tempOverlap ← Overlapi;
tempChannel ← i;
}


}
if (tempChannel <> −1) {
Resolve Contention using NP-Segmentation
Schedule the Unscheduled Burst on Di;
Stop;
}
else {Drop Unscheduled Burst;
Stop;
NP-MOC with void filling
Same structure with NP-MOC
Parameter Overlapi -> Lossi
tempOverlap -> tempLoss
NP-DFMOC v.s. NP-DFMOC-VF
 NP-DFMOC
calculates the overlap on every channel and then
selects the channel with minimum overlap.
scheduled on the free channel with minimum gap.
Time complexity is O(W)
 NP-DFMOC-VF
calculates the delay until the first void on every channel
and then selects the channel with minimum delay.
scheduled on the free channel with minimum gap.
Time complexity is O(WlogNb)
NP-SFMOC v.s. NP-SFMOC-VF
 NP-SFMOC
calculates the overlap on every channel and then
selects the data channel with minimum overlap.
scheduled on the free channel with the minimum Gapi.
Time complexity is O(W)
 NS-SFMOC-VF
calculates the loss on every channel and then selectsthe
channel with minimum loss.
scheduled on the free channel with minimum gap.
Time complexity is O(WlogNb)
Outline
Introduction
Optical Burst Switched (OBS)
Segmentation-Based Nonpreemptive
Scheduling Algorithms with FDL
Conclusion
Conclusion
 Considered burst segmentation and FDLs for burst
scheduling in optical burst-switched networks
 A number of channel scheduling algorithms for OBS
networks
 Perform better than the existing scheduling algorithms
with and without void filling in terms of packet loss
 The delay-first algorithms are suitable for transmitting
packets that have higher delay tolerance and strict loss
constraints, while the segment-first algorithms are
suitable for transmitting packets that have higher loss
tolerance and stric delay constrants.
 Proposed to support QoS.
Global heterogeneous optical network.
Reference
 “Future Optical networks”, Journal of Lightwave Technolog, Vol. 24, NO. 12,
December 2006, Michael J. O’Mahony, Senior Member, IEEE, Christina
Politi, Student Member, IEEE, Dimitrios Klonidis, Member, IEEE, Reza
Nejabati, Member, IEEE, and Dimitra Simeonidou, Member, IEEE
 “Segmentation-Based Nonpreemptive Channel Scheduling Algorithms for
Optical Burst-Switched Networks”, Vinod M. Vokkarane, Member, IEEE, and
P. Jue, Senior Member, IEEE, Journal of light wave technology, vol.23, NO.
10 October 2005
 “Connection-Oriented networks, SONET/SDH, ATM, MPLS and Optical
Networks”, Perros, Harry G. 2005
 http://www.networkworld.com/details/521.html, PON