Multimedia applications and

Optical networks

Sitaram Asur, Sitha Bhagvat, Mohammad Kamrul Islam ,Rajkiran Panuganti 

Overview

Optical Networks - Advantages & Overheads

Requirements of Multimedia Applications

Issues Protocol –level Network –level

Scheduling & QoS Circuit switching OBS OLS

Optical Networks

Can provide very high bandwidth ( > 20TB/s per fiber)

Traditional optical networks are circuit switched Transition to packet switched Wavelength Div Multiplexing (WDM) or TDM

Multiparty communication possible – required in multimedia appl.

Not easy to integrate with current Internet• No efficient O/E or E/O conversion is present.

No Optical RAM no buffering

WDM (Wavelength Div Multiplexing)

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FibersIn

FibersOut

-Mux

Add ports Drop ports

OpticalSpace Switch

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OpticalSpace Switch

2

OpticalSpace Switch

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The challenge of multimedia

Support for continuous media

Quality of service management Packet Delay – delay sensitive Jitter Bandwidth Packet-loss ratio guarantee But, loss tolerant

Multiparty communication Requires ’multicast’ support Different requirement of QoS

Protocols

Traditional Protocols like TCP cannot utilize all the available Bandwidth

New Protocols - Fast, Fair, Friendly High utilization of the abundant bandwidth Intra-protocol fairness TCP friendly

Common Issues solved by New Protocols Acknowledgement Congestion control Bandwidth Estimation – necessary to utilize it

efficiently

UDT (UDP-based Data Transport)

Acknowledgement UDT uses timer-based selective acknowledgement

Congestion control AIMD - Does not meet efficiency objective UDT uses modified AIMD algorithm to use 90% of the

available Bandwidth

Bandwidth Estimation – necessary to utilize it efficiently Link capacity estimation and available BW estimation UDT uses packet-pair method for bandwidth estimation

Avoiding Congestion collapse Cause :- from increasing control traffic - costs both

substantial BW and CPU time• Occurs if processing time is large

UDT increases expiration time to avoid congestion collapse

Scheduling in Circuit Switching

Scheduling necessary for high bandwidth utilization in Lambdas

Circuit switched networks – fixed bandwidth allocation

Fixed bandwidth allocation low bandwidth utilization

Solution – Use knowledge of data sizes to ‘schedule’ calls

What rate should network assign for a particular transfer?

Varying-Bandwidth List Scheduling (VBLS)

Input Known data size Maximum bandwidth limit Desired start time

The scheduler returns a time-range capacity allocation vector assigning varying bandwidth levels in different time ranges for the transfer

VBLS

CircuitSwitch

S3

Shared single link

Ch. 1

Ch. 2

S1

S2 Ch. 3

Ch. 4

D

t=1 t=2 t=3 t=4 t=5)(t

time

1

2

3

4

:Available time ranges

)2,1,2( 1max

11 RTF req

TRC1

)2,1,2( 2max

22 RTF req

TRC2

)3,3,5( 3max

33 RTF req

TRC3

Advantages of VBLS

Time-Range-Capacity vector allocation for vectors

Allows Scheduler to backfill holes

VBLS allows users to take advantage of subsequent availability of network

VBLS better than Packet Switching in ease of implementation, management of pricing mechanisms for resource allocation

Disadvantage – need to reprogram the circuit switch multiple times

Static

Highly Dynamic

Point-to-PointOptical Transport

Point-to-PointOptical Transport

ReconfigurableOptical NetworksReconfigurable

Optical Networks

Optical Label/BurstSwitching

Optical Label/BurstSwitching

Optical Provisioning, Reconfiguration, and Switching Strategies

Netw

ork

Effi

cie

ncy

Present FuturePast

DynamicReconfigurable

Optical Networks

DynamicReconfigurable

Optical Networks

Inflexible reconfigurabilityHigh Management Complexity

Evolution of Optical Networking

True Convergence of IP and Optical Layer

Addresses carrier needs*:• Bandwidth utilization• Provisioning time• Scalability

*RHK Carrier Survey

Next Generation Optical Network

IP over all-optical Wavelength Division Multiplexing (WDM) layer

Optical Burst Switching (OBS)

Combines the best of packet and circuit switching and avoid their shortcomings.

First a control packet is sent using a separate (control) channel (wavelength).

Configure the intermediate node and reserves BW.

Without waiting for the reservation ACK, data “burst” follows the control packet but using different channel.

How OBS works At ingress Edge router E/O conversion occurs. At Edge router, IP packets are assembled into a data

burst. From Edge router, Control packet sent to Core router to

setup a path Data burst sent in the same path using different

wavelength.

Edge Router (CA)

Edge Router (NY)

Legacy Interface (IP)

Legacy Interface (IP)1 Burst

assembly

2 Control packet

3 Switch Configuration

4 Burst forwarding

5 Burst disassembly

Core (TX)

Core (OH)

Scheduling at OBS Core Two basic scheduling algorithms: LUAC ( Latest available unscheduled channel)

Illustration of LAUC algorithm, (a) channel 2 is selected, (b) channel 3 is chosen.

Fiber Delay Lines (FDLs)

Scheduling at OBS Core

LUAC is simple but inefficient channel usage due to gaps/voids. LUAC –VF (LUAC with void Filling)

Illustration of LAUC-VF algorithm.

Buffer allocation at Edge Router

Buffering is required when creating a data burst by assembling the IP packets of same class.

How long assembling continues: till maximum threshold burst size or timeout.

If finds available wavelength, send it.

If not, the scheduler keeps the buffer till it gets an available channel or maximum buffering time .

High priority packets have longer buffering time and hence experience less dropping.

Bandwidth Allocation at Core Switch

Bandwidth allocation of class N at time t Bn(t)& Bandwidth allocation ratio Rn

Higher priority packets has larger value of Fn and hence lower Rn.

When a data burst of class X found no free channel at the output port: Scheduler looks a channel with higher Rn value. It preempts that channel and schedule the burst of class X If no such channel is found, it drops the burst.

Observations: Multimedia applications with larger Fn have smaller dropping probability.

Optical Label Switching (OLS) OLS enables packet switching and multiplexing in the optical

domain Packet forwarding is based on an optical header

Header is sub-carrier multiplexed with the optical data The “label” field in the optical header determines packet forwarding Data is delayed while the header is examined Routers erase and re-insert the label in the optical header

Enable optical time slot switching and multiplexing in subwavelength domain independent of packet protocols

No need for end-to-end network synchronization

Optical Header Extraction Unit

High Bit RateOptical Packet

Low Bit RateSubcarrier Label

Label Extractedfor Processing

Label and PacketForwarded

Fiber

Only low cost electronics required to

process the label in parallel

Advantages of OLS

Only the optical label needs to be converted.

Payload stays optical, which provides transparency to packet bit-rate and data format

Enables dynamic optical switching and routing from the optical circuit to the packet level of granularity Convergence of both types to a single platform

Routers can be shrunk to chip-sized elements that consume two to three orders of magnitude less power than their electrical counterparts

Facilitates support for quality of service (QOS), class of service (COS) and traffic engineering.

Applications

Next Generation Internet; Data exchange communications; Virtual Private Networking (VPN); Analog/digital communications; Voice over Internet Protocol (VoIP); and Broadcasting and video conferencing.

Modern Features of OLS Routers

Multicast contention resolution To support multicast of multimedia applications

Optical Time to Live Weighted TTL - OSNR

Label generation and packet classification based on QoS/CoS requirements

Multicast Contention Resolution in OLS

Multimedia conferencing and streaming are growing fast

Multicast in router saves network resources

Absence of optical logical circuits and buffers to generate copies

Solution : Extra ports on OLS core routers to handle multicast Port contains Multi-Wavelength Converter

Contention resolution and arbitration a challenge

Solution: Multicast Contention Resolution Algorithm

Multicast Contention Resolution

Sad

Label generation and packet Classification

OLS edge routers implement packet aggregation and label processing

Edge routers provide different QoS/CoS policies to client applications.

Label includes the packet length, CoS, source address, destination address etc.

Edge routers at the end points de-aggregates the packets, classifies and maps the packets to different QoS policies.

References

Phuritatkul, J., Ji, Y., “Buffer and Bandwidth Allocation Algorithms for Quality of Service Provisioning in WDM Optical Burst Switching Networks”, Lecture Notes in Computer Science, Vol.3079, pp.912-920, 2004

Qiao, C., Yoo, M., Dixit, S., “OBS for Service Differentiation in the Next-Gen Optical Network”, IEEE Commu. Magazine, Feb. (2001) 98-104

Zhong Pan, Haijun Yang et al, “Advanced Optical-Label Routing System Supporting Multicast, Optical TTL, and Multimedia Applications”, IEEE Journal of Lightwave Technology, Vol 23, No 10, October 2005

R. Ramaswami and K. Sivarajan, Optical Networks: A Practical Perspective, Morgan Kaufmann Publishers, 1998

B. Mukherjee, Optical Communication Networks, McGraw Hill, 1997

THANK YOU

Helper Slides

Helper - Raj