The SAHARA Project: Composition and Cooperation in the New Internet

The SAHARA Project:Composition and Cooperation

in the New Internet

Randy H. Katz, Anthony Joseph, Ion StoicaComputer Science Division

Electrical Engineering and Computer Science DepartmentUniversity of California, Berkeley

Berkeley, CA 94720-1776

Presentation Outline

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



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

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

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

Services in Converged Networks

Services in Converged Networks

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



Sprint

UserSalt Lake

City

Scenario: ServiceComposition

JAL

BabblefishTranslator

Zagat Guide

UI

User

NTTDoCoMo

RestaurantGuide Service

Tokyo

The “Sahara” Project

• Service• Architecture for• Heterogeneous• Access,• Resources, and• Applications

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

Problems and Solutions“The 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

AccessNetwork

s

Core Networks

Internet Connectivity and Processing

Transit Net

Transit Net

Transit Net

PrivatePeering

NAP

PublicPeering

InternetDatacenter

PSTNRegional

WirelineRegionalVoiceVoice

CellCell

Cell

CableModem

LAN

LAN

LAN

Premises-based

WLAN

WLAN

WLAN

Premises-based

Operator-based

H.323Data

Data

RAS

Analog

DSLAM

H.323

Interconnected World:Agile 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.”

Global Packet Network Internetworking

(Connectivity)

ISPCLEC

Internet Service Composition

Application-specificOverlay Networks

(Multicast Tunnels, Mgmt Svrcs)

Applications(Portals, E-Commerce,

E-Tainment, Media)

Application-specific Servers(Streaming Media, Transformation)ASP

InternetData Centers

Appl Infrastructure Services(Distribution, Caching,

Searching, Hosting)

AIPISV

Competition vs. Cooperation

• Internet Service Providers: Competition– Peering for packet transport: BGP protocol– Charging based on traffic volumes

ISP A

ISP B

Hot PotatoRouting

PeeringPoint

PeeringPoint

Composition and Cooperation:Mobile Virtual Network Operator

MVNO has everything but its own physical network

Mobile Virtual Network Operator:Composition and Cooperation

one2one

one2one

1-to-1 Relationship

InterCall

M-to-N Relationships

Competition

GPRS Peering Network

GRXDNS

R

R

Operator C

SGSN

DNSBG

Operator C

SGSN

DNSBG

Per Johannson, Ericsson Research

GPRS Transit: Peering, Cooperation, Composition

R

R

Operator B

SGSN

DNSBG

Operator A

GGSNBG

DNS

GRXR

R

R

DNS

GRXR

R

R

DNS

GRXR

R

R

DNS

GPRS Peering Network

DNS.gprs

PeeringPolicy-Based Routing

• Multi-homing– Reliability of network connectivity– Traffic discrimination

End Network

PrimaryTransit

Network

AlternativeTransit

NetworkPeer

NetworkPeer

NetworkPeer

NetworkPeer

Networks

BerkeleyCampus

CalREN

ResearchTraffic

DormTraffic

Fail-over

New PrimaryTransit

IsolatedIntra-cloud

service

Traditionalunicastpeering

Administrativedomain

Admindomain

Administrativedomain

Admindomain

Admindomain

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

Steve McCanne

OverlaysBrokered Resources for Applications

• Examples: – Multicast management and peering at application

level– Implement performance qualities at overlay level

Steve McCanne

Composition:Wireless ISPs (wISPs)

• T-Mobile Wireless Broadband (MobileStar), WayPort– Traditional network ISP, subscription-based services in public places– Hotels (Wayport), airports (Wayport @ SJ airport), airport clubs (T-

Mobile @ AA Admirals Club), and cafes (T-Mobile @ 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

Single LocationNetwork Operator

(SLN)Single LocationNetwork Operator

(SLN)CooperativeNetworking

Full ServiceNetworkOperator

Full ServiceNetworkOperator Premises-based

Access

Composition of Wireless Infrastructure Services

Full ServiceNetworkOperator

Single LocationNetwork Operator

(SLN)

SLN Aggregator

WISP Aggregator

RevenueSharing

Single Sign-onUnified Billing

Billing, ECommerceAuthentication

Inter-site Mobility

Private Brand NetOperator (MVNO)

VPN Operator, Client-Software



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

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

Service

Negotiation & control path

Service Composition Models

Service Service

Data flow

Cooperative

BrokeredNegotiation & control path

Broker

Service ServiceService

Data flow

Layered Reference Model for Service Composition

IP Network

Enhanced Links

Enhanced Paths

End-to-End NetworkWith Desirable Properties

Middleware Services

Applications Services

End-User Applications

Connect

ivit

yPla

ne

Applic

ati

on

Pla

ne

Serv

ice

Com

posi

tion

Layered Reference Modelfor Service Composition

Services at Layer i-1Services at Layer i-1Services at Layer i-1

Services at Layer i-1Other Servicesat Layer iComponent Services

Composed Service at Layer i

PolicyManagement

Dynamic ResourceAllocation

InteroperabiltyMeasurement-based

Adaptation

Trust Management/Verification

UnderlyingCompositionTechniques

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



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


• 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


• 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


• 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


• 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



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

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 (ICICS’2001), Xi’an, China, (November 2001).

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 (IPTPS’02), 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).

Recent Publications

• Y. Chawathe, M. Seshadri, “Broadcast Federation: An Application-layer Broadcast Internet,” Proceedings Network and Operating System Support for Digital Audio and Video (NOSSDAV’02), 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).

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).

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).

SAHARA: A Revolutionary Service Architecture for Future Telecommunications Systems

Randy H. Katz, Anthony Joseph, Ion StoicaComputer Science Division

Electrical Engineering and Computer Science DepartmentUniversity of California, Berkeley

Berkeley, CA 94720-1776

Work in Progress

• Enhanced Links• Enhanced Paths• Middleware Services• Applications Services

Work in Progress

• Enhanced Links– Congestion Pricing for Access Links– Auction-based Resource (Bandwidth)

Allocation– Traffic Policing/Verification of Bandwidth

Allocation

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%

Internet

Local Area

Network

Computer Acces

s Route

rQoSCompute

r$

Auction-based Resource Allocation

• 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 application’s priority by

changing the token allocation rate.• Status

– On-going work– First application: bandwidth allocation in ad hoc wireless networks

• Problem– Efficiently and effectively allocate

resources according to application’s dynamic requirements

• Approach– Leveraging auction schemes and

work-load predictionsResource

AuctioneerBidder

Application

Bandwidth Allocation

• 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

misbehavingaggregate – split it

R1 attaches new certificateto the refresh message

Work in Progress

• Enhanced Paths– BGP Route Flap Dampening– BGP Policy Agents– Backup Path Allocation in Overlay Networks– Host Mobility– Multicast Interoperation

BGP: Stability vs. Convergence• Problem:

– Stability achieved through flap damping[RFC2439]– Unexpected:flap damping delays convergence!

Solution: selective flap damping [sigcomm02]

Duplicate suppression: Ignore flaps caused by transient convergence instability Still contains stability

Eliminates undesired interaction!

Topology: clique of routers

8898 AS’s

971 AS’s

897 AS’s

129 AS’s

20 AS’s

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

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 ICNP’02

The Underlying Network

The Overlay Network

Host Mobility Using an Internet Indirection Infrastructure

• The Problem– Internet hosts increasingly mobile;

need 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, R)

(ID, data)

(ID, data)

(ID, R)

Receiver (R)

Sender (S)

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.

• 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.

Source

Clients

BG

Broadcast Domains

PeeringData

CDN

IP Mul

SSM

Work in Progress

• Middleware Services– Measurement and Monitoring Infrastructure– Robust Service Composition– Authorization Interworking

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?

Cluster A

End Host

Cluster B

Monitor Distance from monitor to its hosts

Distance measurements among monitors

Cluster C• 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]

TextTexttoto

audioaudio

TextTexttoto

audioaudio

Text Source

Text Source

WA setup: UCB, Berk. (Cable), SF (DSL), Stan., CMU, UCSD, UNSW (Aus), TU-Berlin

(Germany)

• >15sec outage• Note: BGP recovery could take

several minutes [Labovitz’00]

• End-to-end recovery in about 3.6sec: 2sec detection, ~600ms signaling, ~1sec state restoration

• 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 SPECTS’02 paper• More recent results on load

balancing across service replicas…

• Issue: Multi-provider WA composition

• Poor availability of Internet path Poor service availability for client

Availability in Wide-AreaService Composition

Authorization Control Across Administrative Domains

• Authorization authority– Provides authorization decision service.– Manages different verification methods and credentials.

• Trust peering agreement– Credential transformation rule– Acceptable verification method

Trusted third party

Domain 2

Domain 1

Service

User

AuthorizationAuthorizationAuthorityAuthority

Request - certificates - credentials

Should grant access?

Decision

Trust peering agreementTrust peering agreement - credential transformation ruleTrust peering agreementTrust peering agreement - credential transformation rule

VerificationPolicy compliance

check

Credentialtransformation

CertificatesCredentials

Work in Progress

• Applications Services– Voice Over IP – Adaptive Content Distribution– (Universal In-Box)

IP Telephony Gateway Selection

ITG

Load Advertisement

Call Session

LS

Gateway (ITG)IP TerminalLocation Server (LS)

ITG

LS

ITG LS

ITG LSCall Blocking Probability

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Relative Weight of Congestion Sensitivity

Blo

ckin

g P

roba

bilit

y

Random RedirectionCongestion and QoS Redirection

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?

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• Close to optimal #

of replicas wrt latency guarantee

• Small latency & bandwidth for sending updates

• [IPTPS 02] & [Pervasive 02]

data plane

network plane

datasource

Web server

SCAN server

client

replica

always update

adaptivecoherence

cache

Tapestry mesh

The SAHARA Project: Composition and Cooperation in the New Internet

Documents

service compositionsummary

new internetrandy

new business model

network fabricnot protocols

converged networksservices

distributed apps

tcpip protocols

diverse access networks