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Service QoE Monitoring in the Access Network
Bart De VleeschauwerGhent University – IBBT-IMECDepartment of Information [email protected]
03.10.2006 — 2
Muse Project
> MUlti Service access Everywhere
> “The overall objective of MUSE is the research and development of a future, low cost, multi-service access network. The access network should provide secure connectivity between end-user terminals and edge nodes in a multi-provider environment. It should be suited for the ubiquitous delivery of broadband services to every European citizen.”http://www.ist-muse.org
> Service QoE is of prime importance
> Goal of our contribution to MUSE: a knowledge plane in the access network that is responsible for autonomous QoE management.
03.10.2006 — 3
Outline
> Access network overview
> Access network services
> Knowledge plane• Motivation• A two layered architecture
> Access node monitoring and actions• RTP/RTCP monitoring• QoE restorative actions
> Conclusion
03.10.2006 — 4
Access Network Overview
Service Providers
Service Edge
Aggregation Network
Access Node
Residential
Gateway
End Device
User
Home Network
03.10.2006 — 5
Motivation
> Access network services:• VOIP• Video on demand• IPTV• High Speed Internet
> For all these services, QoE is essential
> Packet loss, delay, jitter have huge impact
> Goal:• Autonomous access network QoE management• Monitor the QoE• Enable QoE restorative action• Proactive and reactive QoE monitoring and restoration
03.10.2006 — 7
State of the art> Monitoring the access network
• SNMP (Simple Network Management Protocol)• RMON MIBs• Raqmon• DSLForum
– Protocol described in TR-69– Object models in various working texts
• IPFIX/Netflow• Active monitoring
> Monitor data analysis• “Sketch-based change detection: methods, evaluation, and applications”, Krishnamurthy,
B., Sen, S., Zhang, Y., Chen, Y., 2003• “What’s new: finding significant differences in network data streams”, Cormode, G.,
Muthukrishnan, S., 2005• Database sliding window techniques
> Knowledge plane actions• Retransmissions• Forward error correction• Interleaving
03.10.2006 — 8
Monitoring Plane
MP/KP Responsibilities
Data Reduction
Monitored Data
Sampling Sliding Window Sketch
Knowledge Plane
Reduce data to manageable size
Anomaly Detection
Sketch Test 2Threshold Sketch Test 1
Diagnosis and Solution
Alert diagnosis component
Detect problem root cause and find solution
Analyze data
03.10.2006 — 9
A distributed Knowledge Plane
Monitoring Plane
Knowledge Plane
Knowledge Plane
Monitoring Plane
03.10.2006 — 10
Monitoring Plane
Data Reduction
Knowledge plane – Monitoring plane interaction
Knowledge Plane
Active: e.g. generate additional ICMP ping requests
Passive: e.g. additional threshold in RMON MIB
Anomaly Detection
Diagnosis and Solution
Additional queries over available data
Initialize new anomaly detection modules
Additional info might be needed for accurate fault recovery
Initiate new monitor probes
Anomaly is detected
03.10.2006 — 11
Central role of the access node
> Access node:• Under control of access network provider• Crossing point between aggregation network and last mile + home
network• All data of the same user passes this point
> Ideal place for user/service monitoring and restorative action
> Dedicated protocol monitoring
Knowledge Plane
Monitoring Plane
03.10.2006 — 13
RTP/RTCP
> RFC 3550: RTP: A Transport Protocol for Real-Time Applications
> Two protocols• RTP protocol for data packets• RTCP protocol for control traffic
> RTP packets contain data• Sequence number• Timestamps (Sampling instant of first octet in the RTP data
packet)
> RTCP packets contain control & feedback information
03.10.2006 — 14
RTCP Messages
> SDES, source description items
> BYE, end of participation
> APP, application specific
> SR, Sender Report
> RR, Receiver Report
Report Block
03.10.2006 — 15
Monitor Plane
Streaming Video Services
Goal:• Determine end-to-end QoE• Determine Access-node end-device QoE
RTPSR
RR
Track Sequence NumbersTrack SR timesInspect RRs
03.10.2006 — 16
RTP/RTCP loss estimation
> Receiver calculates the number of packets it expects and the number it has received in an interval
> Fraction lost between two report blocks is reported together with cumulative number of lost packets
> Cumulative number lost = # expected - # received
> Fraction lost = fraction lost since last RR
03.10.2006 — 17
Access node home network loss detection
•Access node keeps track of packets that were sent to end-device
•Access node keeps track of highest sequence numbers in RR
•Access node keeps track of reported fraction lost / number lost packets
Access node can estimate how many packets were lost between access node and end-device
03.10.2006 — 18
RTP/RTCP interarrival Jitter estimation
> Interarrival jitter: variance in interarrival timeServer
End-Device
Sl
time
> End-to-end interarrival jitter is calculated:• Calculate interarrival time between two packets
• D(k,l) = (Rk – Rl) - (Sk – Sl) = (Rk – Sk)- (Rl – Sl)• Jitter estimation• J(k)=J(k-1)+(|D(k,k-1)|- J(k-1) )/16
> Jitter is reported in RR
> Do analogous calculations to determine Server – AN jitter
> Compare end-to-end jitter (RR) and Server-AN jitter
Sk
Rl Rk
03.10.2006 — 19
RTP/RTCP RTT estimation
> RTCP Report block contains fields for• LSR: Last SR timestamp• DLSR: Delay Since last SR
> This allows us to estimate the RTT whenever a RR is received
> Time when SR passes access node: t1
> Time when RR passes access node : t2
> RTT est. = t2-t1-DLSRSender
Access Node
End Device
DLSR
t1 t2
SR
RR
03.10.2006 — 20
Access Node QoE Restorative Action
> Trigger application specific actions when packet loss is detected
• Forward error correction• Interleaving• Intercept retransmission requests at the access node and send
retransmissions– Faster retransmission– Less network load
> Inform higher layers of QoE decrease
> Adapt stream to better suite client specifications
> Dynamic content proxying according to an observed demand pattern
03.10.2006 — 21
Conclusion
> There is a clear need for access network QoE management
> Three goals• QoE monitoring• QoE problem detection• Problem solution
> A two layered solution• Monitor plane• Knowledge plane
> A distributed architecture is able to locate/solve QoE decreases at the appropriate location
> The access node plays a central role in the distributed knowledge plane