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 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 Broadcast TV VoD Regional Network How can we provide reliable IPTV services over the backbone network? Service Architecture of IPTV

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

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-homedRing 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 IP designs Optical design 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

11 SHO Backbone 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 Alt #1: Integrate With Existing IP Backbone

12 Backbone SHO 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 Alt #2: Dedicated Overlay of Existing IP Backbone

13 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) Alt #3: Flat IP (No Backbone) Long haul links SHO 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 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 DesignLayerLink-CapacityAccess TypeFast-Failover Int-IP-HS Int-IP-HS-FRR Int-IP-Ring Int-IP-Ring-FRR IP.. Shared.. Dual-homed.. Ring.. SONET links Fast re-route SONET links Fast re-route Ded-IP-HS Ded-IP-HS-FRR Ded-IP-Ring Ded-IP-Ring-FRR IP.. Dedicated.. Dual-homed.. Ring.. SONET links Fast re-route SONET links Fast re-route P2P-DWDM P2P-DWDM-FRR Optical.. Dedicated.. None.. SONET links Fast re-route Opt-SwitchedOpticalTime-divisionedDual-homedDisjoint paths 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 Increase in VoD loads has significant impact on the overall cost. → Having highly accurate VoD load forecasts is important! Multicast Unicast + Multicast Unicast + Multicast

18 Capital Expense Across Designs (Broadcast TV) 1. Optical designs are more economical than IP-based ones. 2. Cost is dominated by access part (except for flat IP designs). 3. For IP designs, FRR is economical then using SONET links.

19 Access Structure vs Traffic Loads Ring accessDual-homed access multicast only multicast + VoD multicast onlymulticast + 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

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

24 Examples of SRLGs two sources multiple destinations riskspath conduit bridge, tunnel

25 Service Requirements of IPTV 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

26 SHO 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? Path Protection Routing Problem

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 s1Second 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 s2Fail 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 reliableMost Reliable cost 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

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 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) SHO VHO  Step1: For each VHO, find redundant SRLG diverse paths by ILP  Step2: Consolidate solutions SRLG diverse Consolidate!

40 Improved Greedy Local (IGL) SHO 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 GLFind missing paths

41 Adaptive Search (AS) SHO 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 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 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, [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, [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 [APF] Xu et al., “On the complexity of and algorithms for finding the shortest path with a disjoint counterpart,” IEEE/ACM ToN, 14(1): , [Kerpez] K. Kerpez et al., “IPTV Service Assurance,” IEEE Communications, September, 206