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Transcript
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) 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! 2 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 3 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] 4 Service Architecture of IPTV Super Hub Offices (SHO) SHO Backbone Distribution Network VHO How can Regional Network we provide reliable IPTV services TV over the backboneBroadcast network? VoD VHO Video Hub Office (VHO) Regional Network Regional Network customers 2 SHOs and 40 VHOs across the US 5 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 6 Comparison of Design Choices 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 8 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 switching Optical layer SONET protection Dst protection path IP layer fast-reroute (FRR) 9 Potential IPTV Designs IP 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 Optical design 10 Alt #1: Integrate With Existing IP Backbone Support IPTV as multicast application (VoD as unicast) VHO receives single stream from the nearest SHO SHO SHO Backbone VHO VHO Single network to manage Backbone links are shared (careful QoS) Various access connections, fast-failover schemes 11 Alt #2: Dedicated Overlay of Existing IP Backbone Inter-connect common backbone routers with dedicated SHO links SHO VHO Backbone Backbone links are dedicated for IPTV (no QoS) Overhead for managing overlay Various access connections, fast-failover schemes VHO 12 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 SHO SHO Meshed topology (carry “through” traffic) VHO VHO Long haul links 13 Alt #4: Integrating with Existing Optical Backbone Multicast capabilities at optical nodes (new technology) SHOs establish multicast trees, VHO receiving single best stream SHO SHO L1 network VHO Fast-failover is not yet supported in optical multicasting 14 Review: Design Choices IP or optical Technology Hub-and-spoke or highly meshed Link capacity Service layer topology Dedicated or shared Fast-failover SONET links, fast-reroute, or physically diverse paths Access Dual-homed or ring 15 Design Instances Design Layer Link-Capacity Access Type Fast-Failover Int-IP-HS Alt #1 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 Alt #2 Ded-IP-HS Ded-IP-HS-FRR Ded-IP-Ring Ded-IP-Ring-FRR IP .. .. .. Dedicated .. .. .. Dual-homed .. Ring .. SONET links P2P-DWDM Alt #3 Optical P2P-DWDM-FRR .. Dedicated .. None .. Fast re-route Opt-Switched Alt #4 Optical Time-divisioned Dual-homed Disjoint paths Fast re-route SONET links Fast re-route SONET links 16 Cost Analysis: Capital Expense vs Traffic Loads comparison demands b Gb/s Ma+Ub: Cost multicast a across Gb/straffic + unicast 20.0 Relative cost Int-IP-HS-FRR Opt-Switched 15.0 access 10.0 backbone Multicast Multicast + Unicast Multicast M3+U3 M2+U2 M1+U1 M3+U0 M2+U0 M1+U0 M3+U3 M2+U2 M1+U1 M3+U0 M2+U0 0.0 M1+U0 5.0 Multicast + Unicast Increase in VoD loads has significant impact on the overall cost. → Having highly accurate VoD load forecasts is important! 17 Capital Expense Across Designs (Broadcast TV) Multicast 3Gbps + Unicast 0Gbps 6.0 Relative cost 5.0 4.0 acces s backbone 3.0 2.0 1. 2. 3. Opt-Switched P2P-DWDM-FRR P2P-DWDM Int-IP-Ring-FRR Int-IP-Ring Int-IP-HS-FRR Int-IP-HS Ded-IP-Ring-FRR Ded-IP-Ring Ded-IP-HS-FRR 0.0 Ded-IP-HS 1.0 Optical designs are more economical than IP-based ones. Cost is dominated by access part (except for flat IP designs). 18 For IP designs, FRR is economical then using SONET links. Access Structure vs Traffic Loads Multicast 3Gbps + Unicast 0Gbps multicast only Multicast 3Gbps + + Unicast 3Gbps multicast VoD Ring access 40.0 Relative cost 5.0 4.0 acces s backbone 3.0 2.0 Relative cost 6.0 Dual-homed access 30.0 access 20.0 backbone 10.0 multicast only Opt-Switched P2P-DWDM-FRR P2P-DWDM Int-IP-Ring-FRR Int-IP-Ring Int-IP-HS-FRR Int-IP-HS Ded-IP-Ring-FRR Ded-IP-Ring Ded-IP-HS-FRR Ded-IP-HS multicast + VoD Ring access is more economical when only multicast traffic is considered. Dual-homed is better for VoD (no through traffic). Ring 0.0 Opt-Switched P2P-DWDM-FRR P2P-DWDM Int-IP-Ring-FRR Int-IP-Ring Int-IP-HS-FRR Int-IP-HS Ded-IP-Ring-FRR Ded-IP-Ring Ded-IP-HS-FRR 0.0 Ded-IP-HS 1.0 Dual-homed Flat IP design becomes expensive when VoD considered. 19 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 20 Path Protection Routing in WDM Mesh Networks 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 22 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 23 Examples of SRLGs two sources path risks conduit bridge, tunnel multiple destinations 24 Requirements of IPTV IPTVService 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 25 Protection Routing Routing Problem Path Path Protection Problem SHO SHO Backbone VHO VHO VHO VHO VHO How to create two multicast trees such that (1) provisioning cost is minimized and (2) VHOs have physically disjoint paths to SHOs? 26 Link-Diverse vs SRLG-Diverse Multicast path by s1 unused Multicast path by s2 risk1 d1 s1 risk1 s2 d2 d1 s1 risk2 d3 (a) Link-diverse routing, cost=8 s2 d2 risk2 d3 (b) SRLG-diverse routing, cost=9 27 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 s1 d2 d1 s1 s2 d2 risk2 d3 d3 First tree from s1 Second tree from s2 (reduced graph) (a) Active Path First routing, cost=10 28 Trap Situation of APF risk1 d1 s1 s2 d2 d1 s1 s2 d2 risk2 d3 d3 First tree from s2 Fail to find second tree from s1 (b) Active Path First routing, trap situation 29 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 30 Integer Programming Formulation Minimize total cost Flow conservation SRLG diversity 31 Applying Our IP Formulation Dataset 2 SHO and 40 VHO locations in the US IP formulation amenable to realistic topologies! 32 Cost Comparison Across Designs Most reliable Reduced reliability Most Reliable Reduced reliability cost ILP design more economical than heuristic. Cost for increased reliability affordable. 33 Summary First work on supporting IPTV on optical mesh network with SRLG constraints Compact Integer Programming formulation Minimum design cost SRLG-diversity shown affordable 34 Efficient and Scalable Algorithms for Large Network Topologies Motivation Improve path quality Set maximum latency Limit # of intermediate nodes and links Solving an ILP exact algorithm not scalable Net3 36 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” 37 Proposed Heuristics Greedy Local (GL) 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 Divide into subgraphs with two sources and a destination Solve for each graph, and consolidate solutions 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 SRLGdiverse path exists. If yes, then fix the path; otherwise, run baseline ILP. 38 Greedy Local (GL) Step1: For each VHO, find redundant SRLG diverse paths by ILP Step2: Consolidate solutions SHO SHO SRLG SRLG Consolidate! SRLG diverse diverse diverse VHO VHO VHO 39 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 only FindLeave Solution missing from paths GL shorter paths VHO VHO VHO 40 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 SRLG-diverse? VHO Yes! Then, fix as solution. VHO VHO SRLG-diverse? No! Then, replace with SRLG diverse paths. 41 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 Minimum paths w/ ILP SRLG spanning diverse treeSRLG VHO Does SRLG-diverse diverse counterpart path exist? VHO Yes! VHO Then, fix as solution. Does SRLG-diverse counterpart path exist? No! Then, replace with SRLG diverse paths. 42 Capital Expense Comparison Net5 (800sec) Net6 (2sec) 43 CAPEX Scalability Analysis Net5 44 Computation Time Analysis Net5 45 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 46 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 47 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 48 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 49