Infrastructure Design for IPTV Services

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 (ATT)

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 todays TV offers
• Platform
• Standardizations AV coding, EPG/ESG (eletronic
  programming/service guide), device mgmt, ...
• Middleware, settop box
• DRM (digital rights mgmt)
• Todays 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)

• 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
MaUb multicast a Gb/s unicast b Gb/s
Multicast Unicast
Multicast
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
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
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 cost is 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, cost8
(b) SRLG-diverse routing, cost9
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, cost10
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
Most reliable
Most Reliable
Reduced reliability
Reduced reliability
cost

• ILP design more economical than heuristic.
• Cost for increased reliability affordable.

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