Multimedia applications and Optical networks Sitaram Asur, Sitha Bhagvat, Mohammad Kamrul Islam,Rajkiran Panuganti

Overview r Optical Networks - Advantages & Overheads r Requirements of Multimedia Applications r Issues m Protocol –level m Network –level r Scheduling & QoS m Circuit switching m OBS m OLS

Optical Networks  Can provide very high bandwidth ( > 20TB/s per fiber)  Traditional optical networks are circuit switched m Transition to packet switched m 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)... Fibers In Fibers Out -Mux Add portsDrop ports Optical Space Switch 1 Optical Space Switch 2 Optical Space Switch

The challenge of multimedia r Support for continuous media r Quality of service management m Packet Delay – delay sensitive m Jitter m Bandwidth m Packet-loss ratio guarantee m But, loss tolerant r Multiparty communication m Requires ’multicast’ support m Different requirement of QoS

Protocols r Traditional Protocols like TCP cannot utilize all the available Bandwidth r New Protocols - Fast, Fair, Friendly m High utilization of the abundant bandwidth m Intra-protocol fairness m TCP friendly r Common Issues solved by New Protocols m Acknowledgement m Congestion control m Bandwidth Estimation – necessary to utilize it efficiently

UDT (UDP-based Data Transport) r Acknowledgement m UDT uses timer-based selective acknowledgement r Congestion control m AIMD - Does not meet efficiency objective m UDT uses modified AIMD algorithm to use 90% of the available Bandwidth r Bandwidth Estimation – necessary to utilize it efficiently m Link capacity estimation and available BW estimation m UDT uses packet-pair method for bandwidth estimation r Avoiding Congestion collapse m Cause :- from increasing control traffic - costs both substantial BW and CPU time Occurs if processing time is large m UDT increases expiration time to avoid congestion collapse

Scheduling in Circuit Switching r Scheduling necessary for high bandwidth utilization in Lambdas r Circuit switched networks – fixed bandwidth allocation r Fixed bandwidth allocation  low bandwidth utilization r Solution – Use knowledge of data sizes to ‘schedule’ calls r 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 Circuit Switch S3S3 Shared single link Ch. 1 Ch. 2 S1S1 S2S2 Ch. 3 Ch. 4 D t=1t=2t=3t=4 t=5 time : Available time ranges TRC 1 TRC 2 TRC 3

Advantages of VBLS r Time-Range-Capacity vector allocation for vectors r Allows Scheduler to backfill holes r VBLS allows users to take advantage of subsequent availability of network r VBLS better than Packet Switching in ease of implementation, management of pricing mechanisms for resource allocation r Disadvantage – need to reprogram the circuit switch multiple times

Static Highly Dynamic Point-to-Point Optical Transport Point-to-Point Optical Transport Reconfigurable Optical Networks Reconfigurable Optical Networks Optical Label/Burst Switching Optical Label/Burst Switching Optical Provisioning, Reconfiguration, and Switching Strategies Network Efficiency PresentFuturePast Dynamic Reconfigurable Optical Networks Dynamic Reconfigurable Optical Networks Inflexible reconfigurability High 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 r IP over all-optical Wavelength Division Multiplexing (WDM) layer

Optical Burst Switching (OBS) r Combines the best of packet and circuit switching and avoid their shortcomings. r First a control packet is sent using a separate (control) channel (wavelength). r Configure the intermediate node and reserves BW. r Without waiting for the reservation ACK, data “burst” follows the control packet but using different channel.

How OBS works r At ingress Edge router E/O conversion occurs. r At Edge router, IP packets are assembled into a data burst. r From Edge router, Control packet sent to Core router to setup a path r Data burst sent in the same path using different wavelength. Edge Router (CA) Edge Router (NY) 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 r Two basic scheduling algorithms: r 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 r LUAC is simple but inefficient channel usage due to gaps/voids. r LUAC –VF (LUAC with void Filling) Illustration of LAUC-VF algorithm.

Buffer allocation at Edge Router r Buffering is required when creating a data burst by assembling the IP packets of same class. r How long assembling continues: till maximum threshold burst size or timeout. r If finds available wavelength, send it. r If not, the scheduler keeps the buffer till it gets an available channel or maximum buffering time. r High priority packets have longer buffering time and hence experience less dropping.

Bandwidth Allocation at Core Switch r Bandwidth allocation of class N at time t B n (t)& Bandwidth allocation ratio R n r Higher priority packets has larger value of F n and hence lower R n. r When a data burst of class X found no free channel at the output port: m Scheduler looks a channel with higher Rn value. m It preempts that channel and schedule the burst of class X m If no such channel is found, it drops the burst. r Observations: Multimedia applications with larger F n have smaller dropping probability.

OLS Optical Network

Optical Label Switching (OLS) r OLS enables packet switching and multiplexing in the optical domain r Packet forwarding is based on an optical header m Header is sub-carrier multiplexed with the optical data m The “label” field in the optical header determines packet forwarding m Data is delayed while the header is examined m Routers erase and re-insert the label in the optical header r Enable optical time slot switching and multiplexing in subwavelength domain independent of packet protocols m No need for end-to-end network synchronization Optical Header Extraction Unit High Bit Rate Optical Packet Low Bit Rate Subcarrier Label Label Extracted for Processing Label and Packet Forwarded Fiber Only low cost electronics required to process the label in parallel

Optical-Label Switching for Packet Routing WDM Label IP Data Time WDM Wavelength i TDM Label Label features IP Header SCM features Label

Advantages of OLS r Only the optical label needs to be converted. r Payload stays optical, which provides transparency to packet bit- rate and data format r Enables dynamic optical switching and routing from the optical circuit to the packet level of granularity m Convergence of both types to a single platform r Routers can be shrunk to chip-sized elements that consume two to three orders of magnitude less power than their electrical counterparts r Facilitates support for quality of service (QOS), class of service (COS) and traffic engineering.

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

Modern Features of OLS Routers r Multicast contention resolution m To support multicast of multimedia applications r Optical Time to Live m Weighted TTL - OSNR r Label generation and packet classification m based on QoS/CoS requirements

Multicast Contention Resolution in OLS r Multimedia conferencing and streaming are growing fast r Multicast in router saves network resources r Absence of optical logical circuits and buffers to generate copies r Solution : Extra ports on OLS core routers to handle multicast m Port contains Multi-Wavelength Converter r Contention resolution and arbitration a challenge r Solution: Multicast Contention Resolution Algorithm

Multicast Contention Resolution Sad

Optical Time to Live r OLS core routers monitor the OSNR of each packet r The label signal quality is used to estimate the payload signal quality. r OSNR degrades as the packet travels through OLS router hops and links. r When the OSNR goes below a threshold, the router will drop the packet.

Label generation and packet Classification r OLS edge routers implement packet aggregation and label processing r Edge routers provide different QoS/CoS policies to client applications. r Label includes the packet length, CoS, source address, destination address etc. r Edge routers at the end points de-aggregates the packets, classifies and maps the packets to different QoS policies.

References r 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 , 2004 r Qiao, C., Yoo, M., Dixit, S., “OBS for Service Differentiation in the Next-Gen Optical Network”, IEEE Commu. Magazine, Feb. (2001) r 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 R. Ramaswami and K. Sivarajan, Optical Networks: A Practical Perspective, Morgan Kaufmann Publishers, 1998 r B. Mukherjee, Optical Communication Networks, McGraw Hill, 1997

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