Segmentation Based Nonpreemptive Channel Scheduling Algorithms for Optical Burst-Switched Networks Adviser : Ho-Ting Wu Speaker : Chih-Hao Tseng

Segmentation Based Nonpreemptive Channel Scheduling Algorith

ms for Optical Burst-Switched Networks

Adviser : Ho-Ting Wu

Speaker : Chih-Hao Tseng

Outline

IntroductionOptical Burst Switched (OBS)Segmentation-Based Nonpreemptive Sche

duling Algorithms with FDLConclusion

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 digitallyTraditional services and industries move fr

om 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 SpeedNetwork SwitchingAccess 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/conversionOptical monitoring Fast optical switch fabricsOptical buffersIncreased level of integration

Outline



Key Network Technology

Optical Circuit SwitchingOptical Packet SwitchingOCDMAOptical 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.

payload hdr

Wavelength iinput port j

Opticalpacket

hdr CPU

Optical switch

payload

payload hdr

Re-combinedWavelength ioutput port j

OCDMA

Optical Code Division Multiple AccessAn 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

＊ 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.

Header Payload

5 bytes 48 bytes


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

Output WDM fibers

…

Switch fabric

…

…

…

…

…

OBS transport network architecture

A

B

End-device

End-deviceSETUP

Burst

SETUP

Burst

offset

time


Main features of OBS networksMain features of OBS networks


SETUP SETUP ACK KEEP ALIVE RELEASE CONNECT FAILURE

TimeBurst

A

SETUP

SETUP

SETUP

SETUPACK/FAILURE

RELEASE

RELEASE

RELEASE

(Optional)CONNECT

B


(For persistent connection) SESSION DECLARATION DECLARATION ACK SESSION RELEASE

SESSION DECLARATION

SESSION ACK

KEEP ALIVE

SESSION RELEASE

Data transfer

Tear down

SESSION DECLARATION

SESSION DECLARATION

SESSION ACK

KEEP ALIVE

KEEP ALIVE

SESSION RELEASE

SESSION RELEASE

SESSION ACK

BA

Persistent connection setup


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 swi

tch reconfiguration speed in the order of μsec.

Key Subsystems and Technologies

Optical SwitchingOptical MonitoringOptical EncryptionAll-Optical Wavelength Conversion and

RegenerationOptical memory



Nonpreemptive v.s. preemptive

Nonpreemptive Existing channel assignments are not altered The BHP of the segmented unscheduled burst can be i

mmediately 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 sche

duling

Lb ： Unscheduled burst length duration. tub ： Unscheduled burst arrival time. W ： 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 chann

el 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 t

he first available channel for the new arriving burst Time complexity is O(logW)

LAUC Keeps track of the LAUT on every data channel and ass

igns 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 schedul

ed data burst on very data channel Utilize voids between two data-burst assignmen

ts. 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 us

ed in non-voidfilling channel scheduling algorithms. The overlap is 0 if the channel i

s 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-MOCParameter Overlapi -> Lossi

tempOverlap -> tempLoss

NP-DFMOC v.s. NP-DFMOC-VF

NP-DFMOC calculates the overlap on every channel and then select

s 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 select

s the data channel with minimum overlap. scheduled on the free channel with the minimum Gap i. Time complexity is O(W)

NS-SFMOC-VF calculates the loss on every channel and then selectsth

e channel with minimum loss. scheduled on the free channel with minimum gap. Time complexity is O(WlogNb)

Outline



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

Documents

Segmentation Based Nonpreemptive Channel Scheduling Algorithms for Optical Burst-Switched Networks Adviser : Ho-Ting Wu Speaker : Chih-Hao Tseng