multimedia applications and optical networks
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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)
...
...
......
......
FibersIn
FibersOut
-Mux
Add ports Drop ports
OpticalSpace Switch
1
OpticalSpace Switch
2
OpticalSpace Switch
160
...
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
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