The impact of the peer-to-peer paradigm increases both in research and in industry. Still, serious applications for P2P-based systems are rare. On the other hand, Emergency Call Handling (ECH) is (or will be) a mandatory function for VoIP services. In this paper we investigate international legal and technical requirements of ECH and present ECHoP2P, a solution that fulfills these requirements. Based on Globase.KOM and HiPNOS.KOM, ECHoP2P provides the functionality to determine the closest and (geographically) responsible Emergency Station to a calling peer. Further, Emergency Calls are processed with highest priority in the overlay, so that quality of service guarantees are given. We evaluated ECHoP2P thoroughly and present the quality and costs analysis, identified tradeoffs and effects of optimization parameters. ECHoP2P provides a fully evaluated solution for Emergency Call Handling and for further location-aware applications.
ECHoP2P: Emergency Call Handling over Peer-to-Peer Overlays
Kalman Graffi, Aleksandra Kovacevic, Kyra Wulffert, Ralf Steinmetz
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Outline
Motivation
Legal and Technical Requirements
Solution: ECHoP2P• Globase.KOM: Location Based Search
• SOS Area Search• SOS Jurisdiction Search• SOS Jurisdiction Search Extended
• HiPNOS.KOM: QoS for Overlay Flows
Evaluation
Conclusion and Impact
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Emergency Call Handling is Crucial
Observation:VoIP telephony is replacing primary phone service
Emergency Call Service:• Core feature of (classic) telephone networks• Limited support by VoIP Providers• No support by any P2P Internet telephony network
End User License Agreement
„No Emergency Calls: by entering into this Agreement You acknowledge and agree that the Skype Software does not and does not intend to support or carry emergency calls.“
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Scalable all-IP based ECH needed: P2P can help!
Policies governing Voice over IP are rapidly evolving• Emergency Call Support becomes mandatory around the world
Network technologies are converging
• Next Generation Networks• P2P over UMTS and GPRS/GSM All-IP paradigm
IP-based telephony requires Emergency Call Support !• P2P-based architecture is a good candidate• P2P solution can be applied on any IP enabled network• P2P systems: scalable, robust and load balanced (if done well)
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Outline
Motivation
Legal and Technical Requirements
Solution: ECHoP2P• Globase.KOM: Location Based Search
• SOS Area Search• SOS Jurisdiction Search• SOS Jurisdiction Search Extended
• HiPNOS.KOM: QoS for Overlay Flows
Evaluation
Conclusion and Impact
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Legal and technical requirements
1. Provision of the caller’s number for call backs and identification2. (Fast) provision of the caller’s geographical position3. Identification of the calling person (EU and Japan)4. Provision of call back opportunities and call up keeping5. Dispatching the call to ES responsible for the caller’s location6. Highest delay priority for emergency calls: low delay bounds7. Provision of stable communication even under network congestion
Location critical service:• Routing: contact the closest or the responsible ES
Quality of service is crucial: • Emergency Calls are privileged user traffic• Contact the ES as soon as possible• In case of congestion: keep less relevant traffic back
Can peer-to-peer systems fulfill these requirements?
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Outline
Motivation
Legal and Technical Requirements
Solution: ECHoP2P• Globase.KOM: Location Based Search
• SOS Area Search• SOS Jurisdiction Search• SOS Jurisdiction Search Extended
• HiPNOS.KOM: QoS for Overlay Flows
Evaluation
Conclusion and Impact
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EC Routing: Implementation in Globase.KOM
Problem: Location-based search requirements
Solution: Globase.KOM - Geographical LOcation BAsed SEarch• More details:
• IEEE P2P ’07 • ACM Transactions on Multimedia ‘07
• Developed for the requirements of location based services
• A logical neighbour is a geographical neighbour• Like in CAN• But: Tree structure enables search/lookup in O(log N)
• Extended with following search mechanisms:• Closest peer (Emergency Station ES)• Peer fulfilling a specific criteria (responsibility)
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Globase.KOM: Geographical LOcation BAsed SEarch
A
= peers= superpeers
A
B
B
Lower boundL1
Upper boundL2
Superpeer load Split zone to reduce load
J
D
K E
H
GC
FC D E
F G H I JKI
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EC Routing: Implementation in GLOBASE.KOM
Problem: Which is the proper Emergency Station?
Solutions for GLOBASE.KOM:
• SOS Area Search
• Focus on neighboring peers to caller’s location
• Find closest Emergency Station
• SOS Jurisdiction Search
• Emergency Stations with Coverage Area
• Find responsible Emergency Services Station
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Outline
Motivation
Legal and Technical Requirements
Solution: ECHoP2P• Globase.KOM: Location Based Search
• SOS Area Search• SOS Jurisdiction Search• SOS Jurisdiction Search Extended
• HiPNOS.KOM: QoS for Overlay Flows
Evaluation
Conclusion and Impact
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Closest Emerg. Station: SOS Area Search
r
rnew
SOSO
A
BD
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SOS
SOS
SOS
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SOS
H
Emergency Stations
GH
Peer
Super Peer
Emergency station
F
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SOS
G
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Responsible ES : SOS Jurisdiction Search
SOSO
A
BD
E
G
H
I SOS
SOS
SOS
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SOSI
Emergency Stations
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SOS Peer
Super Peer
Emergency station
Emergency st. coverage area
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Discussion to Presented Search Mech.
SOS Area Search:• Finds closest peer with attribute X (= Emerg. Station)• But only few (what if destroyed?)
SOS Jurisdiction Search• Finds (jurisdictionally) responsible peer • But only one (same problem)
List of close ES may be useful in catastrophe scenarios
Solution: If responsible Emergency Station in not available,
then contact the next closest Emergency Station
SOS Jurisdiction Search Extended
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List of ESs: SOS Jurisdiction Search Extended
SOSO
A
BD
E
G
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SOS
SOS
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SOS
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Emergency Stations
GHI
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SOS Peer
Super Peer
Emergency station
Emergency st. coverage area
J
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Outline
Motivation
Legal and Technical Requirements
Solution: ECHoP2P• Globase.KOM: Location Based Search
• SOS Area Search• SOS Jurisdiction Search• SOS Jurisdiction Search Extended
• HiPNOS.KOM: QoS for Overlay Flows
Evaluation
Conclusion and Impact
12.04.23
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Scheduling and Active Queue Management
Mechanisms to provide QoS in network layer
• Scheduling• Reorder tasks/messages in queue• Reference: First-in-First-Out
• Active Queue Management • Active upon congestion of queue• Reference: Drop Tail
• For loss – criticality (1 byte)• For delay – criticality (1 byte)
Active Queue Management solution:• If buffer size exceeded:
• Drop message with lowest loss-prio.
Scheduling solution• If bandwidth available:
• Pick message with highest latency-prio.
Avoid starvation• Periodically increase delay-prio. of queued messages
HiPNOS.KOM: Sched. and AQM of Overlay Flows
In-from overlay
Insert msg in buffer
Apply AQM mech.
Timeout
Pick next msg (SCHED)
Out to underlay
Bandwidth available?
Receive message
yesno
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Outline
Motivation
Legal and Technical Requirements
Solution: ECHoP2P• Globase.KOM: Location Based Search
• SOS Area Search• SOS Jurisdiction Search• SOS Jurisdiction Search Extended
• HiPNOS.KOM: QoS for Overlay Flows
Evaluation
Conclusion and Impact
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PEvaluation: Simulation Scenarios
Alabama Emergency Zones. Source: NENAAlabama Density Population. Source: US censusSnapshop of the simulated scenarios
PeerfactSim.KOM:
P2P Systems Simulator
www.PeerfactSim.com
General parameters• 10,000 peers• Without churn and failures
Built scenarios• SOS Area Search• SOS Jurisdiction Search• SOS Jurisdiction Search Extended
Metrics:• Operation duration• # of contacted peers• Distance to the closest found ES• Ratio of responsible ES• Message type distribution
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Evaluation: Efficiency
Metrics Operation Duration Contacted peer
Scenarios SOS search algorithms
Experiment size 10.000 peers
• Operation durationCompared to SOS Jurisdiction Search
• SOS Jurisdiction Search Ext.
~ 43% more efficient• SOS Area Search
~ 28% more efficient
• Contacted peers per operation Compared to SOS Jurisdiction Search Ext.
• SOS Jurisdiction Search
~ 3 times less• SOS Area Search
~ 2 times less
SOS Calls Normalized Distribution
Op
era
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ura
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ms
]
SOS Calls Normalized Distribution
Co
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d P
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Evaluation: Efficiency
Metrics Distance, Responsible ES %
Scenarios SOS search algorithms
Experiment size 10.000 peers
• Distance Compared to SOS Jurisdiction Search
• SOS Jurisdiction Search Ext.
~ 13% more efficient• SOS Area Search
~ 28% more efficient
• Percentage of responsible ES• SOS Jurisdiction Search ~ 100%• SOS Jurisdiction Search Ext. ~ 25%• SOS Area Search ~ 21%
Dis
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[p
ixe
l]R
es
po
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ES
[%
]
SOS Calls Normalized Distribution
SOS Calls Normalized Distribution
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Evaluation: Summary of Results
SOS Area Search SOS Jurisdiction Search
SOS Jurisdiction Search Extended
Cost: Operation time Medium High Low
Cost: Contacted peers Medium Low High
Cost: SOS traffic Medium Low High
Metric: Distance to ES Low High Medium
Metric: # of results Medium Low High
Successful operations 98% 100% 100%
Suitable for everyday emergency scenarios?
No, resp. areas needed
Yes Yes
Suitable forcatastrophe scenarios?
Yes, only few results
No, if the responsiblestation collapses
Yes
not good / good / very good
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Outline
Motivation
Legal and Technical Requirements
Solution: ECHoP2P• Globase.KOM: Location Based Search
• SOS Area Search• SOS Jurisdiction Search• SOS Jurisdiction Search Extended
• HiPNOS.KOM: QoS for Overlay Flows
Evaluation
Conclusion and Impact
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Conclusion and Impact
Problem: Emergency Call Handling needed for P2P-based VoiP
ECHoP2P: • Built on
• Globase.KOM: Geographical LOcation BAsed Search• HiPNOS.KOM: provides QoS to overlay flows
• Presented protocols:• Search for the closest Emergency Station ES (Area Search)• Lookup the responsible ES (Jurisdiction Search)• Search for list of ES in the near (Jurisdiction Search Ext.)
Evaluation:• Solutions fulfill requirements for ECH in VoIP• Tradeoffs identified, application areas named
Impact:• “Serious” P2P application presented• Need for QoS in P2P systems pointed out
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Questions?
Kalman Graffi
Peer-to-Peer Research Group
Dept. of Electrical Engineering and Information TechnologyMultimedia Communications Lab · KOM
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