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Infrastructure Design for IPTV Services
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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 Regional Network Video Hub Office (VHO) 2 SHOs and 40 VHOs across the US customers Regional Network Backbone Distribution Network Super Hub Offices (SHO) VHO VHO Broadcast TV VoD Regional Network How can we provide reliable IPTV services over the backbone network?
  • 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
    Dual-homed Ring Backbone Backbone VHO
  • 9. Design Space
      • Reliability
        • Goal: resilient to single SHO/router/link failures
        • Mechanisms: Fast-failover + routing protocols
    working path Src Dst Failure switching Optical layer SONET protection Src Dst working path protection path IP layer fast-reroute (FRR) Failure
  • 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 SHO SHO Backbone VHO VHO
    • 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
  • 12. Alt #2: Dedicated Overlay of Existing IP Backbone Backbone SHO SHO VHO VHO
    • 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
  • 13. Alt #3: Flat IP (No Backbone)
    • 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)
    Long haul links SHO SHO VHO VHO
  • 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 Technology Service layer topology Fast-failover Link capacity IP or optical SONET links, fast-reroute, or physically diverse paths Dedicated or shared Hub-and-spoke or highly meshed Access Dual-homed or ring
  • 16. Design Instances Alt #1 Alt #2 Alt #3 Alt #4 Disjoint paths Dual-homed Time-divisioned Optical Opt-Switched SONET links Fast re-route None .. Dedicated .. Optical .. P2P-DWDM P2P-DWDM-FRR SONET links Fast re-route SONET links Fast re-route Dual-homed .. Ring .. Dedicated .. .. .. IP .. .. .. Ded-IP-HS Ded-IP-HS-FRR Ded-IP-Ring Ded-IP-Ring-FRR SONET links Fast re-route SONET links Fast re-route Dual-homed .. Ring .. Shared .. .. .. IP .. .. .. Int-IP-HS Int-IP-HS-FRR Int-IP-Ring Int-IP-Ring-FRR Fast-Failover Access Type Link-Capacity Layer Design
  • 17. Cost Analysis: Capital Expense vs Traffic Loads M a +U b : multicast a Gb/s + unicast b Gb/s
    • Increase in VoD loads has significant impact on the overall cost.
    • -> Having highly accurate VoD load forecasts is important!
    Multicast Multicast Unicast + Multicast Unicast + Multicast
  • 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 access Dual-homed access multicast only multicast + VoD multicast only multicast + VoD
    • 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.
    Dual-homed Ring
  • 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 Routing in WDM 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 multiple destinations risks path conduit bridge, tunnel
  • 25. IPTV Backbone Design Goals
    • 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
    Service Requirements of IPTV
  • 26. Path Protection Routing Problem SHO SHO VHO VHO VHO VHO Backbone VHO Path Protection Routing Problem How to create two multicast trees such that (1) provisioning cost is minimized and (2) VHOs have physically disjoint paths to SHOs?
  • 27. Link-Diverse vs SRLG-Diverse d1 s2 s1 d2 d3 d1 s2 s1 d2 d3 (a) Link-diverse routing, cost=8 (b) SRLG-diverse routing, cost=9 risk1 risk2 risk1 risk2 unused Multicast path by s1 Multicast path by s2
  • 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 d1 s2 s1 d2 d3 d1 s2 s1 d2 d3 First tree from s1 Second tree from s2 (reduced graph) (a) Active Path First routing, cost=10 risk1 risk2
  • 29. Trap Situation of APF d1 s2 s1 d2 d3 d1 s2 s1 d2 d3 First tree from s2 Fail to find second tree from s1 (b) Active Path First routing, trap situation risk1 risk2
  • 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 SRLG diversity Flow conservation
  • 32. Applying Our IP Formulation
    • Dataset 2 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 Most Reliable cost Reduced reliability Reduced reliability
  • 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 Algorithms for Large Network Topologies
  • 36. Motivation
    • Improve path quality
      • Set maximum latency
      • Limit # of intermediate nodes and links
    • Solving an ILP exact algorithm not scalable
  • 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) SHO SHO VHO VHO VHO
      • Step1: For each VHO, find redundant SRLG diverse paths by ILP
      • Step2: Consolidate solutions
    SRLG diverse SRLG diverse SRLG diverse Consolidate!
  • 40. Improved Greedy Local (IGL) SHO SHO VHO VHO VHO
      • Step1: Run GL
      • Step2: For each VHO, fix the shorter path
      • Step3: Find missing paths all together using ILP
    Leave only shorter paths Solution from GL Find missing paths
  • 41. Adaptive Search (AS) SHO SHO VHO VHO VHO SRLG-diverse? Yes! Then, fix as solution. SRLG-diverse? No! Then, replace with SRLG diverse paths.
      • Step1: Use any initial routing scheme to find paths
      • Step2: For each VHO, make sure paths are SRLG-diverse
    Initial routing 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 VHO VHO VHO Does SRLG-diverse counterpart path exist? Yes! Then, fix as solution. Does SRLG-diverse counterpart path exist? No! Then, replace with SRLG diverse paths. Not possible! SRLG diverse SRLG diverse Minimum spanning tree Find missing paths w/ ILP
  • 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,” 9 th 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