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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 l-Mux Fibers Out Optical Space Switch l160 ... Add ports ... ... ... ... Optical Space Switch l2 ... Fibers In Optical Space Switch l1 ... WDM (Wavelength Div Multiplexing) Drop ports 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 :Available time ranges S1 TRC1 S2 2 ( F 2 2, Treq2 1, Rmax 2) TRC2 3 ( F 3 5, Treq3 3, Rmax 3) S3 Shared single link 1 1 ( F 1 2, Treq 1, Rmax 2) TRC3 Circuit Switch Ch. 1 Ch. 2 D Ch. 3 Ch. 4 (t ) t=1 t=2 t=3 t=4 t=5 4 3 2 1 time 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 Evolution of Optical Networking Network Efficiency Optical Provisioning, Reconfiguration, and Switching Strategies True Convergence of IP and Optical Layer Static Highly Dynamic Optical Label/Burst Switching Dynamic Reconfigurable Optical Networks Addresses carrier needs*: Reconfigurable • Bandwidth utilization Optical Networks • Provisioning time Point-to-Point Optical Transport Past • Scalability Inflexible reconfigurability High Management Complexity Present Future *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. 3 Switch Configuration 4 Burst forwarding Core (TX) Edge Router (NY) 1 Burst assembly Legacy Interface (IP) Edge Router (CA) 2 Control packet Core (OH) 5 Burst disassembly Legacy Interface (IP) Scheduling at OBS Core Two basic scheduling algorithms: LUAC ( Latest available unscheduled channel) Fiber Delay Lines (FDLs) Illustration of LAUC algorithm, (a) channel 2 is selected, (b) channel 3 is chosen. 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 High Bit Rate Optical Packet Low Bit Rate Subcarrier Label Label and Packet Forwarded Fiber Optical Header Extraction Unit Label Extracted for Processing 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