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Infrastructure Design for IPTV Services
IPTV AsiaNovember 8-9, 2006
Grand Copthorne Waterfront Hotel, Singapore
Sue MoonJoint 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 “Quadr
uple Play” (+wireless/mobile)
Evolution Path Controversy over distinction between broadcasting and co
mmunication 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 guaranteeSame level of quality as today’s TV offers
Platform Standardizations: AV coding, EPG/ESG (eletronic program
ming/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
Regional Network
Video Hub Office (VHO)
2 SHOs and 40 VHOs across the US
customers
Regional Network
Regional Network
Backbone Distribution Network
Super Hub Offices (SHO)
VHO
VHO
Broadcast TVVoD
Regional Network
Regional Network
How can we provide reliable IPTV servicesover 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
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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 pathSrc
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
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SHOSHO
BackboneVHO 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 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
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
SHO
VHO
VHO
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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
SHOSHO
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
AccessDual-homed or ring
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Design Instances
Design Layer Link-Capacity Access Type
Fast-Failover
Int-IP-HSInt-IP-HS-FRRInt-IP-RingInt-IP-Ring-FRR
IP......
Shared......
Dual-homed
..Ring
..
SONET linksFast re-routeSONET linksFast re-route
Ded-IP-HSDed-IP-HS-FRRDed-IP-RingDed-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-Switched Optical Time-divisioned Dual-homed
Disjoint paths
Alt #1
Alt #2
Alt #3
Alt #4
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Cost Analysis: Capital Expense vs Traffic Loads
Cost comparison across traffic demands
0.0
5.0
10.0
15.0
20.0
M1+
U0
M2+
U0
M3+
U0
M1+
U1
M2+
U2
M3+
U3
M1+
U0
M2+
U0
M3+
U0
M1+
U1
M2+
U2
M3+
U3
Rel
ativ
e co
st
access
backbone
Int-IP-HS-FRR Opt-Switched
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!
MulticastMulticast
Unicast+
Multicast
Unicast+Multicast
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Capital Expense Across Designs (Broadcast TV)
Multicast 3Gbps + Unicast 0Gbps
0.0
1.0
2.0
3.0
4.0
5.0
6.0
Ded
-IP
-HS
Ded
-IP
-HS
-FR
R
Ded
-IP
-Rin
g
Ded
-IP
-Rin
g-F
RR
Int-
IP-H
S
Int-
IP-H
S-F
RR
Int-
IP-R
ing
Int-
IP-R
ing-
FR
R
P2P
-DW
DM
P2P
-DW
DM
-FR
R
Opt
-Sw
itche
d
Rel
ativ
e co
st
accessbackbone
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 LoadsMulticast 3Gbps + Unicast 0Gbps
0.0
1.0
2.0
3.0
4.0
5.0
6.0
Ded
-IP
-HS
Ded
-IP
-HS
-FR
R
Ded
-IP
-Rin
g
Ded
-IP
-Rin
g-F
RR
Int-
IP-H
S
Int-
IP-H
S-F
RR
Int-
IP-R
ing
Int-
IP-R
ing-
FR
R
P2P
-DW
DM
P2P
-DW
DM
-FR
R
Opt
-Sw
itche
d
Rel
ativ
e co
st
access
backbone
Multicast 3Gbps + Unicast 3Gbps
0.0
10.0
20.0
30.0
40.0
Ded
-IP
-HS
Ded
-IP
-HS
-FR
R
Ded
-IP
-Rin
g
Ded
-IP
-Rin
g-F
RR
Int-
IP-H
S
Int-
IP-H
S-F
RR
Int-
IP-R
ing
Int-
IP-R
ing-
FR
R
P2P
-DW
DM
P2P
-DW
DM
-FR
R
Opt
-Sw
itche
d
Rel
ativ
e co
st
access
backbone
Ring access Dual-homed accessmulticast 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
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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 Routingin
WDM Mesh Networks
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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
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Layered architecture
Link failure in one layer → multiple failures in the upper layerTwo disjoint links may belong to a common SRLG
What is SRLG (Shared Risk Link Group)?
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Examples of SRLGs
two sources
multiple destinations
riskspath conduit
bridge, tunnel
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Service Requirements of IPTVIPTV 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
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SHOSHO
VHO
VHO
VHOVHO
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
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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
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An SRLG-Diverse Solution: Active Path First
1. Construct a minimum spanning tree from one source2. Remove all SRLG links of the first tree3. 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
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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
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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
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Integer Programming Formulation
Minimize total cost
SRLGdiversity
Flowconservation
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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 Most Reliablecost
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
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-divers
e path exists. If yes, then fix the path; otherwise, run baseline ILP.
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Greedy Local (GL)
SHOSHO
VHO
VHO
VHO
Step1: For each VHO, find redundant SRLG diverse paths by ILP
Step2: Consolidate solutions
SRLGdiverse
SRLGdiverse
SRLGdiverseConsolidate!
40
Improved Greedy Local (IGL)
SHOSHO
VHO
VHO
VHO
Step1: Run GL Step2: For each VHO, fix the shorter path Step3: Find missing paths all together using ILP
Leave onlyshorter paths
Solution from GLFind missing paths
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Adaptive Search (AS)
SHOSHO
VHO
VHO
VHOSRLG-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
SHOSHO
VHO
VHO
VHODoes SRLG-diversecounterpart path exist?
Yes!Then, fix as solution.
Does SRLG-diverse counterpart path exist?No!
Then, replace with SRLG diverse paths.
Not possible!
SRLGdiverse SRLG
diverse
Minimumspanning
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
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IPTV Service Monitoring [Kerpez]
Elements of IPTV Service Assurance Subscriber management
Billing, subscriptions, AAA, DRM
Video headendConverged services, VoD, Broadcast
Transport networkIP/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