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The SAHARA Four-Layer Model;Case-studies in Composition
Bhaskaran Raman, Jimmy Shih, Randy H. Katz,
SAHARA, EECS, U.C.Berkeley
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
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
• Capabilities– 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
Mobile Virtual Network Operator:Composition and Cooperation
one2one
one2one
1-to-1 Relationship
InterCall
M-to-N Relationships
Competition
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• Main Result
– Can be 20-30% more robust compared to shortest disjoint path allocation• 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-Area
Service 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
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
Evaluation: Emulation Testbed
• Idea: Use real implementation, emulate the wide-area network behavior (NistNET)
• Opportunity: Millennium cluster
App
LibNode 1
Node 2
Node 3
Node 4
Rule for 12
Rule for 13
Rule for 34
Rule for 43
Emulator
Also have limited (8-node) wide-area testbed