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Infrastructure Design for IPTV Services

Explore the technical challenges, service architecture, and design choices for delivering reliable IPTV services over backbone networks. Compare various design instances and cost analyses for optimal solutions.

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Infrastructure Design for IPTV Services

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  1. Infrastructure Design for IPTV Services IPTV Asia November 8-9, 2006 Grand Copthorne Waterfront Hotel, Singapore Sue Moon Joint Work with Meeyoung Cha (KAIST) W. Art Chaovalitwongse (Rutgers/DIMACS) Gagan Choudhury, Zihui Ge, Aman Shaikh, Jenniver Yates (AT&T)

  2. Push behind IPTV • TV service over IP • Replacement of TV distribution networks • Core service of “Triple Play” (voice, data, video) and “Quadruple Play” (+wireless/mobile) • Evolution Path • Controversy over distinction between broadcasting and communication • Bundled vs blended services • As seen here so far! 

  3. Technical Challenges of IPTV • Distribution network • WAN, MAN, and access technologies • Resilient design required • QoS guarantee • Same level of quality as today’s TV offers • Platform • Standardizations: AV coding, EPG/ESG (eletronic programming/service guide), device mgmt, ... • Middleware, settop box • DRM (digital rights mgmt) • Today’s conditional access system not enough

  4. Talk Outline • Service Architecture Overview • Comparison of Design Choices [Cha06-1] • Path Protection Routing in WDM Mesh Networks [Cha06-2] • Efficient and Scalable Algorithms [Cha06-3]

  5. Service Architecture of IPTV SHO Super Hub Offices (SHO) Backbone Distribution Network VHO How can we provide reliable IPTV servicesover the backbone network? Regional Network Broadcast TV VoD VHO Regional Network Video Hub Office (VHO) Regional Network customers 2 SHOs and 40 VHOs across the US

  6. IPTV Traffic • Type • Broadcast TV: realtime, 1-3Gb/s • Popular VoD: non-realtime download to VHOs • Niche (esoteric) VoD: realtime, 0-3 Gb/s per VHO • Characteristics • Uni-directional and high-bandwidth • High traffic variability expected for VoD • Multicast for broadcast TV / unicast for VoD

  7. Comparison of Design Choices

  8. Design Space • Technology: layer 1 optical vs. layer 3 IP/MPLS • Service layer topology: hub-and-spoke vs. meshed (ring-based) • Access connections: dual-homed vs. ring Backbone Backbone VHO Dual-homed Ring

  9. Design Space • Reliability • Goal: resilient to single SHO/router/link failures • Mechanisms: Fast-failover + routing protocols Failure working path Src working path Failure Dst Src Dst protection path switching Optical layer SONET protection IP layer fast-reroute (FRR)

  10. Potential IPTV Designs • New dedicated IP backbone for IPTV • Integrating with existing IP backbone • Dedicated overlay over existing IP backbone • Directly inter-connect IP routers (no backbone) • Integrating with existing optical backbone IP designs Optical design

  11. Alt #1: Integrate With Existing IP Backbone • Support IPTV as multicast application (VoD as unicast) • VHO receives single stream from the nearest SHO • Single network to manage • Backbone links are shared (careful QoS) • Various access connections, fast-failover schemes SHO SHO Backbone VHO VHO

  12. Alt #2: Dedicated Overlay of Existing IP Backbone • Inter-connect common backbone routers with dedicated links • Backbone links are dedicated for IPTV (no QoS) • Overhead for managing overlay • Various access connections, fast-failover schemes SHO SHO Backbone VHO VHO

  13. Alt #3: Flat IP (No Backbone) SHO SHO VHO Long haul links VHO • Connect geographically close VHOs into regional rings • Inter-connect rings with long haul links • Security is higher than using IP backbone • No access part • Fast-failover • Meshed topology (carry “through” traffic)

  14. Alt #4: Integrating with Existing Optical Backbone • Multicast capabilities at optical nodes (new technology) • SHOs establish multicast trees, VHO receiving single best stream • Fast-failover is not yet supported in optical multicasting SHO SHO L1 network VHO

  15. Review: Design Choices IP or optical Technology Hub-and-spoke or highly meshed Service layer topology Link capacity Dedicated or shared Access Fast-failover Dual-homed or ring SONET links, fast-reroute, or physically diverse paths

  16. Design Instances Alt #1 Alt #2 Alt #3 Alt #4

  17. Cost Analysis: Capital Expense vs Traffic Loads Ma+Ub: multicast a Gb/s + unicast b Gb/s Multicast Multicast Unicast Multicast Multicast Unicast + + • Increase in VoD loads has significant impact on the overall cost. → Having highly accurate VoD load forecasts is important!

  18. Capital Expense Across Designs (Broadcast TV) • Optical designs are more economical than IP-based ones. • Cost is dominated by access part (except for flat IP designs). • For IP designs, FRR is economical then using SONET links.

  19. Access Structure vs Traffic Loads Ring Dual-homed multicast only multicast + VoD Ring access Dual-homed access • Ring access is more economical when only multicast traffic is considered. Dual-homed is better for VoD (no through traffic). • Flat IP design becomes expensive when VoD considered. multicast only multicast + VoD

  20. Summary • Explore potential IPTV designs in backbone network • Comparison across different architectural alternatives (use realistic capital cost model) • Design instances generated based on real topologies • Significant benefits of using multicast for broadcast TV • Optical design more economical than IP designs • Ring access attractive for broadcast TV • Dual-homed access attractive for VoD

  21. Path Protection RoutinginWDM Mesh Networks

  22. Motivation • Optical design known most economical [cha06-01] • Fast fail-over not yet available in optical multicast Provisioning approach in optical backbone [SRLG] - Design multicast trees (from SHOs to VHOs) in a failure-resilient and cost-effective manner

  23. What is SRLG (Shared Risk Link Group)? • Layered architecture Link failure in one layer →multiple failures in the upper layer Two disjoint links may belong to a common SRLG

  24. Examples of SRLGs two sources conduit path risks bridge, tunnel multiple destinations

  25. IPTV Backbone Design Goals Service Requirements of IPTV • Fault Tolerance • Customers expect “always-on” service • Resiliency against SRLG failures Use redundant SRLG diverse paths from SHOs to VHOs • Low Cost • To be competitive in the market • Each link associated with port / transport cost Find minimum cost multicast trees

  26. Path Protection Routing Problem Path Protection Routing Problem SHO SHO Backbone VHO VHO VHO VHO VHO • How to create two multicast trees such that (1) provisioning costis minimized and (2) VHOs have physically disjoint paths to SHOs?

  27. Link-Diverse vs SRLG-Diverse Multicast path by s1 unused Multicast path by s2 risk1 risk1 d1 s2 d1 s2 s1 d2 s1 d2 risk2 risk2 d3 d3 (a) Link-diverse routing, cost=8 (b) SRLG-diverse routing, cost=9

  28. An SRLG-Diverse Solution: Active Path First 1. Construct a minimum spanning tree from one source 2. Remove all SRLG links of the first tree 3. Build the second minimum spanning tree with remaining links risk1 d1 s2 d1 s2 s1 d2 s1 d2 risk2 d3 d3 First tree from s1 Second tree from s2 (reduced graph) (a) Active Path First routing, cost=10

  29. Trap Situation of APF risk1 d1 s2 d1 s2 s1 d2 s1 d2 risk2 d3 d3 First tree from s2 Fail to find second tree from s1 (b) Active Path First routing, trap situation

  30. Our Provisioning Approach • Include SRLG-diverse constraints and solve the problem thru Integer Programming (IP) • Compare against • APF (Active Path First) heuristic • Less resilient source-diverse design • Less resilient link-diverse design

  31. Integer Programming Formulation Minimize total cost Flow conservation SRLG diversity

  32. Applying Our IP Formulation • Dataset2 SHO and 40 VHO locations in the US • IP formulation amenable to realistic topologies!

  33. Cost Comparison Across Designs ILP design more economical than heuristic. Cost for increased reliability affordable. Most reliable Reduced reliability Most Reliable Reduced reliability cost

  34. Summary • First work on supporting IPTV on optical mesh network with SRLG constraints • Compact Integer Programming formulation • Minimum design cost • SRLG-diversity shown affordable

  35. Efficient and Scalable Algorithmsfor Large Network Topologies

  36. Motivation • Improve path quality • Set maximum latency • Limit # of intermediate nodes and links • Solving an ILP exact algorithm not scalable Net3

  37. New Heuristic Approach • Divide-and-Conquer technique for large network topologies: • Partition the problem into smaller ones • Solve each small problem • Integrate the solutions “well”

  38. Proposed Heuristics • Greedy Local (GL) • Divide into subgraphs with two sources and a destination • Solve for each graph, and consolidate solutions • Improved Greedy Local (IGL) • Do GL and find the minimum cost graph • Fix the shorter of the two paths and solve the rest • Adaptive Search • Use any routing algorithm to find initial tree • Find SRLG-diverse paths; for those w/o such, run baseline ILP. • Modified Active Path First • Build one MST first; then for each destination, check if a SRLG-diverse path exists. • If yes, then fix the path; otherwise, run baseline ILP.

  39. Greedy Local (GL) • Step1: For each VHO, find redundant SRLG diverse paths by ILP • Step2: Consolidate solutions SHO SHO SRLGdiverse SRLGdiverse Consolidate! SRLGdiverse VHO VHO VHO

  40. Improved Greedy Local (IGL) • Step1: Run GL • Step2: For each VHO, fix the shorter path • Step3: Find missing paths all together using ILP SHO SHO Leave onlyshorter paths Solution from GL Find missing paths VHO VHO VHO

  41. Adaptive Search (AS) • Step1: Use any initial routing scheme to find paths • Step2: For each VHO, make sure paths are SRLG-diverse SHO SHO Initial routing paths VHO SRLG-diverse? Yes! Then, fix as solution. VHO VHO SRLG-diverse? No! Then, replace with SRLG diverse paths.

  42. Modified Active Path First (MAPF) • Step1: Find minimum spanning tree from one source • Step2: For each VHO, make sure SRLG counterpart part path exists • Step3: Find the missing paths all together using ILP SHO SHO Not possible! Find missing paths w/ ILP Minimumspanningtree SRLGdiverse SRLGdiverse VHO Does SRLG-diversecounterpart path exist? Yes! Then, fix as solution. VHO VHO Does SRLG-diverse counterpart path exist? No! Then, replace with SRLG diverse paths.

  43. Capital Expense Comparison Net5 (800sec) Net6 (2sec)

  44. CAPEX Scalability Analysis Net5

  45. Computation Time Analysis Net5

  46. Summary • Additional quality improvements of SRLG-diverse paths • latency limits • # of intermediate nodes and links • per-path upper bound of SRLGs • Efficient and scalable solutions for realistic network topologies

  47. Implications for Other Networks • Cross-layer optimization • Optical + IP layer info combined • Topological constraints • Mesh vs star • WAN vs MAN • Cost constraints • OXC port vs router port

  48. IPTV Service Monitoring [Kerpez] • Elements of IPTV Service Assurance • Subscriber management • Billing, subscriptions, AAA, DRM • Video headend • Converged services, VoD, Broadcast • Transport network • IP/MPLS, Ethernet, DSLAM/OLT, Gateways

  49. References [Cha06-1] Cha et al., “Case study: resilient backbone design for IPTV services,” IPTV Workshop (WWW 2006), Edinburgh, May, 2006. [Cha06-2] Cha et al., “Path protection routing with SRLG constraints to support IPTV in WDM mesh networks,” 9th IEEE Global Internet Symposium, Barcelona, April, 2006. [Cha06-3] Cha et al., “Efficient and scalable provisioning solutions for always-on multicast streaming services,” (in submission). [SRLG] Sebos et al., “Auto-discovery of shared risk link groups,” IEEE OFC, March 2001. [APF] Xu et al., “On the complexity of and algorithms for finding the shortest path with a disjoint counterpart,” IEEE/ACM ToN, 14(1):147-158, 2006. [Kerpez] K. Kerpez et al., “IPTV Service Assurance,” IEEE Communications, September, 206

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