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Title: The SAHARA Project: Composition and Cooperation in the New Internet


1
The SAHARA ProjectComposition and
Cooperationin the New Internet
  • Randy H. Katz, Anthony Joseph, Ion Stoica
  • Computer Science Division
  • Electrical Engineering and Computer Science
    Department
  • University of California, Berkeley
  • Berkeley, CA 94720-1776

2
Presentation Outline
  • Service Architecture Opportunity
  • SAHARA Project Motivation
  • SAHARA Reference Architecture
  • Mechanisms for Service Composition
  • Summary and Conclusions

3
Presentation Outline
  • Service Architecture Opportunity
  • SAHARA Project Motivation
  • SAHARA Reference Architecture
  • Mechanisms for Service Composition
  • Summary and Conclusions

4
Traditional View of Networking
  • All about protocols and the OSI layers
  • Protocol details link-state vs. distance vector,
    TCP
  • Protocol layering
  • Multiaccess technology
  • Switching and routing
  • Naming
  • Error control
  • Flow control scheduling
  • Special topics like multicast and mobility

5
The New Opportunity
  • New things you can do inside the network
  • Connecting end-points to services with
    processing embedded in the network fabric
  • Not protocols but agents, executing in places
    in the network
  • Location-aware, data format aware
  • Controlled violation of layering necessary!
  • Distributed architecture aware of network
    topology
  • No single technical architecture likely to
    dominate think overlays, system of systems

6
Distributed Service Architectures for Converged
Networks
  • Converged Networks
  • Public Switched Telephone Network (PSTN)
  • Internet/Public Switched Data Network (PSDN)
  • Mobile Internet
  • Converged Structure?
  • Distributed Service Architecture
  • Services
  • -Ility connectivity
  • Rich call new call features
  • Infrastructure services proxies, search,
    commerce
  • Enablers for distributed apps event content
    distribution

7
Services in Converged Networks
8
Services in Converged Networks
9
New Kind of Communications-Oriented Service
Architecture
  • Emerging, still developing, in a highly
    heterogeneous environment
  • Rapid development/deployment of new services
    apps
  • Delivered to radically different end devices
    (phone, computer, info appliance) over diverse
    access networks (PSTN, LAN, Wireless, Cellular,
    DSL, Cable, Satellite)
  • Exploiting Internet-based technology core
    clients/server, applications level routers,
    TCP/IP protocols, Web/XML formats
  • Beyond traditional call processing model
    client-proxy-server plus application-level
    partitioning
  • Built upon a new business model being driven by
    the evolution of the Internet traditional
    managed networks and services versus emerging
    overlay networks and services structured on top
    of and outside of the above
  • Composition via cooperation or brokering to
    achieve enhanced performance and reliability

10
Presentation Outline
  • Service Architecture Opportunity
  • SAHARA Project Motivation
  • SAHARA Reference Architecture
  • Mechanisms for Service Composition
  • Summary and Conclusions

11
Scenario ServiceComposition
12
The Sahara Project
  • Service
  • Architecture for
  • Heterogeneous
  • Access,
  • Resources, and
  • Applications

13
Sahara Research Focus
  • New mechanisms, techniques for end-to-end
    services w/ desirable, predictable, enforceable
    properties spanning potentially distrusting
    service providers
  • Tech architecture for service composition
    inter-operation across separate admin domains,
    supporting peering brokering, and diverse
    business, value-exchange, access-control models
  • Functional elements
  • Service discovery
  • Service-level agreements
  • Service composition under constraints
  • Redirection to a service instance
  • Performance measurement infrastructure
  • Constraints based on performance, access control,
    accounting/billing/settlements
  • Service modeling and verification

14
Problems and SolutionsThe Network Effect
  • Creating and deploying new services
  • Development and deployment expense
  • Cost of 3G licenses and networks
  • Even if I had 1 billion and set up 1000s of
    locations, I could never in my network have a
    completely ubiquitous footprint.Sky Dayton,
    founder of Boingo
  • Composition, cooperation, overlays
  • Achieving desirable end-to-end properties
  • Control of the end-to-end path
  • Cooperation, peering, overlays (brokering)
  • Evolving network services
  • Difficult to change global operational
    infrastructure
  • Overlays, cooperation

15
Internet Connectivity and Processing
16
Interconnected WorldAgile or Fragile?
  • Baltimore Tunnel Fire, 18 July 2001
  • The fire also damaged fiber optic cables,
    slowing Internet service across the country,
  • Keynote Systems says the July 19 Internet
    slowdown was not caused by the spreading of Code
    Red. Rather, a train wreck in a Baltimore tunnel
    that knocked out a major UUNet cable caused it.
  • PSINet, Verizon, WorldCom and AboveNet were some
    of the bigger communications companies reporting
    service problems related to peering, methods
    used by Internet service providers to hand
    traffic off to others in the Web's
    infrastructure. Traffic slowdowns were also seen
    in Seattle, Los Angeles and Atlanta, possibly
    resulting from re-routing around the affected
    backbones.
  • The fire severed two OC-192 links between
    Vienna, VA and New York, NY as well as an OC-48
    link from, D.C. to Chicago. Metromedia routed
    traffic around the fiber break, relying heavily
    on switching centers in Chicago, Dallas, and
    D.C.

17
Internet Service Composition
18
Competition vs. Cooperation
  • Internet Service Providers Competition
  • Peering for packet transport BGP protocol
  • Charging based on traffic volumes

ISP A
Hot Potato Routing
ISP B
19
Composition and CooperationMobile Virtual
Network Operator
  • MVNO has everything but its own physical network

20
Mobile Virtual Network OperatorComposition and
Cooperation
21
GPRS Transit Peering, Cooperation, Composition
Per Johannson, Ericsson Research
22
PeeringPolicy-Based Routing
  • Multi-homing
  • Reliability of network connectivity
  • Traffic discrimination

Primary Transit Network
End Network
Berkeley Campus
Dorm Traffic
Alternative Transit Network
Research Traffic
Fail-over
Peer Network
Peer Network
Peer Network
Peer Networks
CalREN
23
OverlaysCreating New Interdomain Services
  • Deploy new services above the routing layer
  • E.g., interdomain multicast management and
    peering
  • E.g., alternative connectivity for performance,
    resilience

Isolated Intra-cloud service
Traditional unicast peering
Steve McCanne
24
OverlaysBrokered Resources for Applications
  • Examples
  • Multicast management and peering at application
    level
  • Implement performance qualities at overlay level

Steve McCanne
25
CompositionWireless ISPs (wISPs)
  • T-Mobile Wireless Broadband (MobileStar), WayPort
  • Traditional network ISP, subscription-based
    services in public places
  • Hotels (Wayport), airports (Wayport _at_ SJ
    airport), airport clubs (T-Mobile _at_ AA Admirals
    Club), and cafes (T-Mobile _at_ Starbucks)
  • Diverse billing models e.g., 24-hour
    subscription at a hotel
  • Boingo, Joltage, hereUare, NetNearU
  • Aggregator of access, e.g., Boingo aggregates
    Wayport, hereUare
  • Client s/w including network sniffer/location
    finder, back-end authentication/secure
    VPN/settlement services
  • Revenue sharing with micro ISPs/single local
    network (SLN)
  • Diverse billing models subscriptions as well as
    pay per use
  • Sputnik
  • Cooperative wireless neighbor-to-neighbor
    networks
  • Ipass, GRIC
  • Secure remote access for mobile employees
  • Simplify connection establishment and login,
    wireless VPN support

26
Composition of Wireless Infrastructure Services
Billing, ECommerce Authentication Inter-site
Mobility
Full Service Network Operator
Premises-based Access
27
Presentation Outline
  • Service Architecture Opportunity
  • SAHARA Project Motivation
  • SAHARA Reference Architecture
  • Mechanisms for Service Composition
  • Summary and Conclusions

28
Technical Challenges
  • Trust management and behavior verification
  • Meet promised functionality, performance,
    availability
  • Adapting to network dynamics
  • Actively respond to shifting server-side
    workloads and network congestion, based on
    pervasive monitoring measurement
  • Awareness of network topology to drive service
    selection
  • Adapting to user dynamics
  • Resource allocation responsive to client-side
    workload variations
  • Resource provisioning and management
  • Service allocation and service placement
  • Interoperability across multiple service
    providers
  • Interworking across similar services deployed by
    different providers

29
Service Composition Models
  • Cooperative
  • Individual component service providers interact
    in distributed fashion, with distributed
    responsibility, to provide an end-to-end composed
    service
  • Brokered
  • Single provider, the Broker, uses functionalities
    provided by underlying service providers,
    encapsulates these to compose an end-to-end
    service
  • Examples
  • Cooperative roaming among separate mobile
    networks
  • Brokered JAL restaurant guide

30
Service Composition Models
31
Layered Reference Model for Service Composition
End-User Applications
Applications Services
Application Plane
Middleware Services
End-to-End Network With Desirable Properties
Enhanced Paths
Connectivity Plane
Enhanced Links
IP Network
32
Layered Reference Modelfor Service Composition
Composed Service at Layer i
33
Layered Reference Modelfor Service Composition
  • Connectivity Plane
  • End-to-end network with desirable properties
    composed on top of commodity IP network
  • Enhanced Links Paths QoS and protocol
    verification within and between connectivity
    service providers
  • Applications Plane
  • Services strategically placed and actively
    managed within the network topology
  • Applications and Middleware Services end-client
    oriented vs. infrastructure oriented

34
Presentation Outline
  • Service Architecture Opportunity
  • SAHARA Project Motivation
  • SAHARA Reference Architecture
  • Mechanisms for Service Composition
  • Summary and Conclusions

35
Mechanisms for Service Composition
  • Measurement-based Adaptation
  • Examples
  • General-purpose third party end-to-end Internet
    host distance monitoring and estimation service
  • Universal In-box Application-specific middleware
    measurement layer to exchange network and server
    load using link-state algorithm
  • Content Distribution Networks measurement-based
    DNS-based server selection to redirect client to
    closest service instance

36
Mechanisms for Service Composition
  • Utility-based Resource Allocation Mechanisms
  • Examples
  • Auctions to dynamically allocate resources
    applied for spectrum/bandwidth resource
    assignments to MVNO from underlying competiting
    MNOs
  • Congestion pricing influence user behavior to
    better utilize scarce resources applied in
  • Voice port allocation to user-initiated calls in
    H.323 gateway/Voice over IP service management
  • Wireless LAN bandwidth allocation and management
  • H.323 gateway selection, redirection, and load
    balancing for Voice over IP services

37
Mechanisms for Service Composition
  • Trust Mgmt/Verification of Service Usage
  • Authentication, Authorization, Accounting
    Services
  • Authorization control scheme w/ credential
    transformations to enable cross-domain service
    invocation
  • Federated admin domains with credential
    transformation rules based on established peering
    agreements
  • AAA server makes authorization decisions,
    liberating providers from preparing rules for
    each affiliated domain
  • Service Level Agreement Verification
  • Verification and usage monitoring to ensure
    properties specified in SLA are being honored
  • Border routers monitoring control traffic from
    different providers to detect malicious route
    advertisements

38
Mechanisms for Service Composition
  • Policy Management
  • Visibility into local policies to better
    coordinate global policies among (cooperating)
    service providers
  • Developing inter-AS architecture for load
    balancing, performance and failure mode policies
    to be applied throughout the network
  • Internet topology discovery through AS
    relationship map of the Internet plus measurement
    infrastructure
  • Policy agent framework for inter-AS negotiation
    to manage incoming traffic

39
Mechanisms for Service Composition
  • Interoperability through Transformation
  • Interoperability of data, protocols, policies
    among composed service providers
  • Example
  • Broadcast federation global multicast service
    composed from multicast implementations in
    different provider domains
  • Protocol transformation gateways between admin
    domains employing non-interoperable multicast
    protocol implementations

40
Presentation Outline
  • Service Architecture Opportunity
  • SAHARA Project Motivation
  • SAHARA Reference Architecture
  • Mechanisms for Service Composition
  • Summary and Conclusions

41
Summary and Conclusions
  • Goal Evolve (mobile) Internet architecture to
    better support multi-network/multi-service
    provider model
  • Dynamic environment, location-based implies
    larger numbers of service providers service
    instances
  • Status architectural specification driven by
    selected applications and underlying wide-area
    services
  • Focus
  • Composition across confederated vs. independent
    service providers peer-to-peer vs. brokering
  • Explore new techniques/technologies
  • Market-based mechanisms
  • Trust management, SLA verification, perf.
    monitoring

42
Recent Publications
  • C. Chuah, L. Subramanian, A. D. Joseph, R. H.
    Katz, QoS Provisioning Using A Clearing House
    Architecture, 8th International Workshop on
    Quality of Service (IWQOS 2000), Pittsburgh, PA,
    (June 2000).
  • S. Zhuang, B. Zhao, A. Joseph, R. H. Katz, J.
    Kubiatowicz, Bayeux An Architecture for
    Wide-Area, Fault-Tolerant Data Dissemination
    Protocol, ACM NOSSDAV 2001, New York, (June
    2001).
  • Z. Mao, W. So, R. H. Katz, Network Support for
    Mobile Multimedia Using a Self-Adaptive
    Distributed Proxy, ACM NOSSDAV 2001, New York,
    (June 2001).
  • Y. Chen, A. Bargteil, R. H. Katz, Quantifying
    Network Denial of Service A Location Service
    Case Study, Third International Conference on
    Information and Communication Security
    (ICICS2001), Xian, China, (November 2001).

43
Recent Publications
  • J. Shih, R. H. Katz, Pricing Experiments for a
    Computer-Telephony-Service Usage Allocation,
    IEEE Globecom 2001, San Antonio, TX, (November
    2001).
  • Y. Chen, R. H. Katz, J. Kubiatowicz, Replica
    Placement for Scalable Content Delivery,
    Proceedings First International Conference on
    Peer-to-Peer Systems (IPTPS02), Cambridge, MA,
    (March 2002).
  • T. Suzuki, R. H. Katz, An Authorization Control
    Framework to Enable Service Composition Across
    Domains, Proceedings Eleventh World Wide Web
    Conference (WWW2002), Honolulu, HI, (May 2002).
  • M. Caesar, D. Ghosal, R. H. Katz, Resource
    Management for IP Telephony Networks,
    Proceedings 10th International Workshop on
    Quality of Service (IWQoS), Miami Beach, FL, (May
    2002).
  • S. Machiraju, M. Seshadri, I. Stoica, A Scalable
    and Robust Solution for Bandwidth Allocation,
    Proceedings 10th International Workshop on
    Quality of Service (IWQoS), Miami Beach, FL, (May
    2002).

44
Recent Publications
  • Y. Chawathe, M. Seshadri, Broadcast Federation
    An Application-layer Broadcast Internet,
    Proceedings Network and Operating System Support
    for Digital Audio and Video (NOSSDAV02), Miami
    Beach, FL, (May 2002).
  • L. Subramanian, V. Padmanabhan, R. H. Katz,
    Geographic Properties of Internet Routing,
    USENIX Conference, Monterey, California, (June
    2002).
  • Z, Mao, C. Cranor, F. Douglis, M. Rabinovich, O.
    Spatscheck, J. Wang, A Precise and Efficient
    Evaluation of the Proximity between Web Clients
    and their Local DNS Servers, USENIX Conference,
    Monterey, California, (June 2002).
  • L. Subramanian, S. Agarwal, J. Rexford, R. H.
    Katz, Characterizing the Internet Hierarchy from
    Multiple Vantage Points, IEEE Infocomm
    Conference, New York, NY, (June 2002).

45
Recent Publications
  • J. Shih, R. H. Katz, Evaluating Tradeoffs of
    Congestion Pricing for Voice Calls, Extended
    Abstract, ACM Sigmetrics Conference, San Diego,
    California, (July 2002).
  • J. Shih, R. H. Katz, Evaluating the Tradeoffs of
    Congestion Pricing for Voice Calls, 2002
    International Symposium on Performance Evaluation
    of Computer and Telecommunication Systems (SPECTS
    2002), San Diego, California, (July 2002).
  • B. Raman, R. H. Katz, Emulation-based Evaluation
    of an Architecture for Wide-Area Service
    Composition, 2002 International Symposium on
    Performance Evaluation of Computer and
    Telecommunication Systems (SPECTS 2002), San
    Diego, California, (July 2002).
  • Z. Mao, R. Govindan, S. Shenker, R. H. Katz,
    Route Flap Damping Exacerbates Internet Routing
    Convergence. ACM SIGCOMM Conference, Pittsburgh,
    PA, (August 2002).

46
Recent Publications
  • B. Raman, S. Agrawal, Y. Chan, M. Caesar, W. Cui,
    P. Johannson, K. Lai, T. Lavian, S, Machiraju, Z.
    Mao, G. Porter, T. Roscoe, M. Seshadri, J. Shih,
    K. Sklower, L. Subramanian, T. Suzuki, S. Zhuang,
    A. D. Joseph, R. H. Katz, I. Stoica, The SAHARA
    Model for Service Composition across Multiple
    Providers, Pervasive Computing 2002, Zurich,
    Switzerland, (August 2002).
  • Z. Mao, R. H. Katz, A Framework for Universal
    Service Access using Device Ensembles, CRA Grace
    Murray Hopper Celebration of Women in Computer
    Science Conference, Vancouver, BC, (October
    2002).

47
SAHARA A Revolutionary Service Architecture for
Future Telecommunications Systems
  • Randy H. Katz, Anthony Joseph, Ion Stoica
  • Computer Science Division
  • Electrical Engineering and Computer Science
    Department
  • University of California, Berkeley
  • Berkeley, CA 94720-1776

48
Work in Progress
  • Enhanced Links
  • Enhanced Paths
  • Middleware Services
  • Applications Services

49
Work in Progress
  • Enhanced Links
  • Congestion Pricing for Access Links
  • Auction-based Resource (Bandwidth) Allocation
  • Traffic Policing/Verification of Bandwidth
    Allocation

50
Congestion Pricing at Access Links
  • Setup
  • 10 users
  • 3 QoS (Slow-going, Moderate, Responsive)differ
    on degree of traffic smoothing
  • 24 tokens/day, 15 minutes of usage per charge
  • Acceptable
  • Users make purchasing decision at most once every
    15 minutes
  • Feasible
  • Changing prices cause users to select different
    QoS
  • Effective
  • If entice half of users to choose lower QoS
    during congestion, then reduce burstiness at
    access links by 25

51
Auction-based Resource Allocation
  • Problem
  • Efficiently and effectively allocate resources
    according to applications dynamic requirements
  • Approach
  • Leveraging auction schemes and work-load
    predictions
  • Features
  • Bidders can place bids based on application
    requirements and contention level.
  • Bidders can place bids for near future resource
    requirements based on recent history.
  • Bidders can express both utility and priority to
    auctioneer.
  • Auctioneer can dynamically change applications
    priority by changing the token allocation rate.
  • Status
  • On-going work
  • First application bandwidth allocation in ad hoc
    wireless networks

52
Bandwidth Allocation
R1 attaches new certificate to the refresh message
  • Problem scalable (stateless) and robust
    bandwidth allocation
  • Control Plane
  • Soft state
  • Per-router per-period certificates for robustness
    without per-flow state
  • Random sampling to prevent duplicate refreshes
  • Data Plane
  • Monitor aggregate flows
  • Recursively split misbehaving aggregates

misbehaving aggregate split it
53
Work in Progress
  • Enhanced Paths
  • BGP Route Flap Dampening
  • BGP Policy Agents
  • Backup Path Allocation in Overlay Networks
  • Host Mobility
  • Multicast Interoperation

54
BGP Stability vs. Convergence
  • Problem
  • Stability achieved through flap dampingRFC2439
  • Unexpectedflap damping delays convergence!
  • Topology clique of routers
  • Solution selective flap damping sigcomm02
  • Duplicate suppression
  • Ignore flaps caused by transient convergence
    instability
  • Still contains stability
  • Eliminates undesired interaction!

55
Policy Management for BGP
  • 3-15 minute failover time
  • Slow response to congestion
  • Unacceptable for Internet service composition
  • Lack of distributed route control
  • Need distributed policy management
  • Explicit route policy negotiation
  • Identified current routing behavior
  • Inferred AS relationships, topology
  • Next gather traffic data, finish code, emulate

56
Backup Path Allocation in Overlay Networks
  • Challenge
  • Disjoint primary and backup path in the overlay
    network may share underlying links because the
    overlay network cannot control underlying links
    used by a path
  • Problem
  • Find a primary and backup path pair with minimal
    failure probability based on correlated overlay
    link failures
  • Approach
  • Decouple backup path routing from primary path
    routing
  • Route backup paths based on failure probability
    cost which measures the incremental path failure
    probability caused by using a link in the path
  • Status
  • Finished work, submitted to ICNP02

57
Host Mobility Using an Internet Indirection
Infrastructure
  • The Problem
  • Internet hosts increasingly mobileneed to
    remain reachable
  • Flows should not be interrupted
  • IP address represents unique host ID net
    location
  • ROAM (Robust Overlay Architecture for Mobility)
  • Leverages i3 overlay network triggers forward
    packets
  • Efficiency, robustness, location privacy,
    simultaneous mobility
  • No changes to end-host kernel or applications
  • Cost i3 infrastructure, and proxies on
    end-hosts
  • Simulation Experimental Results
  • Stretch lower than MIP-bi ? able to choose nearby
    triggers
  • 50-66 of MIP-tri when 5-28 domains deploy i3
    servers
  • Even 4 handoffs in 10 seconds have little impact
    on TCP performance

(ID, data)
(ID, R)
Sender (S)
(ID, data)
(ID, R)
Receiver (R)
58
Multicast Broadcast Federation
  • Goal compose different non-interoperable
    multicast domains to provide an end-to-end
    multicast service.
  • Should work for both IP and App-layer protocols.
  • Approach overlay of Broadcast Gateways (BGs)
  • BGs establish peering between domains.
  • Inside a domain, local multicast capability is
    used.
  • Clustered gateways for scalability.
  • Independent data flows and control flow.

Source
Broadcast Domains
CDN
IP Mul
SSM
Clients
BG
Peering
Data
  • Implementation
  • Linux/C event-driven program
  • Easily customizable interface to local multicast
    capability (700 lines)
  • Upto 1 Gbps BG thruput with 6 nodes.
  • Upto 2500 sessions with 6 nodes.

59
Work in Progress
  • Middleware Services
  • Measurement and Monitoring Infrastructure
  • Robust Service Composition
  • Authorization Interworking

60
Internet Distance Monitoring Infrastructure
  • Problem N end hosts in different administrative
    domains, how to select a subset to be probes, and
    build an overlay distance monitoring service
    without knowing the underlying topology?
  • Solution Internet Iso-bar
  • Clustering of hosts perceiving similar
    performance
  • Good scalability
  • Good accuracy stability
  • Tested with NLANR
  • AMP Keynote data
  • Small overhead
  • Incrementally deployable
  • SIGMETRICS PAPA 02
  • CMG journal 02

Cluster C
Cluster B
Cluster A
Monitor
Distance from monitor to its hosts
Distance measurements among monitors
End Host
61
Availability in Wide-AreaService Composition
Text to audio
  • Issue Multi-provider ? WA composition
  • Poor availability of Internet path ? Poor service
    availability for client

Text to audio
  • gt15sec outage
  • Note BGP recovery could take several minutes
    Labovitz00
  • Fix detect and recover from failures using
    service replicas
  • Highlight of results
  • Quick detection (2sec) possible
  • Scalable messaging for recovery (can handle
    simultaneous failure recovery of 1000s of
    clients)
  • See SPECTS02 paper
  • More recent results on load balancing across
    service replicas
  • End-to-end recovery in about 3.6sec 2sec
    detection, 600ms signaling, 1sec state
    restoration

WA setup UCB, Berk. (Cable), SF (DSL), Stan.,
CMU, UCSD, UNSW (Aus), TU-Berlin (Germany)
62
Authorization Control Across Administrative
Domains
Trusted third party
Domain 1
Should grant access?
Authorization Authority
Service
Decision
Request - certificates - credentials
Verification
Policy compliance check
Certificates Credentials
Credential transformation
Domain 2
User
Trust peering agreement - credential
transformation rule
  • Authorization authority
  • Provides authorization decision service.
  • Manages different verification methods and
    credentials.
  • Trust peering agreement
  • Credential transformation rule
  • Acceptable verification method

63
Work in Progress
  • Applications Services
  • Voice Over IP
  • Adaptive Content Distribution
  • (Universal In-Box)

64
IP Telephony Gateway Selection
LS
ITG
LS
ITG
LS
ITG
  • Results
  • Congestion sensitive pricing decreases
    unnecessary call blocking, increases revenue, and
    improves economic efficiency
  • Hybrid redirection achieves good QoS and low
    blocking probability
  • Goal High quality, economically efficient
    telephony over the Internet
  • Questions How to
  • Perform call admission control?
  • Route calls thru converged net?

65
SCAN Scalable Content Access Network
  • Problem Provide content distribution to clients
    with small latency, small of replicas and
    efficient update dissemination
  • Solution SCAN
  • Leverage P2P location services to improve
    scalability and locality
  • Simultaneous dynamic replica placement
    app-level multicast tree construction

data plane
data source
  • Close to optimal of replicas wrt latency
    guarantee
  • Small latency bandwidth for sending updates
  • IPTPS 02
  • Pervasive 02

Web server
SCAN server
network plane
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