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QoS-aware Traffic Protection for Access Rings Srivas Chennu Kai Habel Klaus-Dieter Langer.

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Presentation on theme: "QoS-aware Traffic Protection for Access Rings Srivas Chennu Kai Habel Klaus-Dieter Langer."— Presentation transcript:

1 QoS-aware Traffic Protection for Access Rings Srivas Chennu Kai Habel Klaus-Dieter Langer

2 S. Chennu, K. Habel, K.-D. Langer A Brief Outline > Link layer architecture for protected access rings > The Fast Access Ring Protection Protocol (FARPP) > QoS-awareness in the access ring > Simulative evaluation of FARPP > Conclusions

3 S. Chennu, K. Habel, K.-D. Langer Access Ring Protection Architecture > Design philosophy: Centralized network management Operates at the link layer Exploits uneven breakup of responsibilities Simplifies design Leads to lower cost devices (reduced investment) in the field Provides for reduced latency times for reconfiguration Affords better control over traffic distribution in ring Borrows ideas from existing standards and protocols > Two dissimilar protocol entities Relatively complex HUB entity at the CO Simple ONU entity at end user

4 S. Chennu, K. Habel, K.-D. Langer The HUB Entity > ‘Intelligent' component in control of network operator > Responsible for key network management tasks > Has 2 ring ports and an external MAN/WAN port > Lookup table stores topology view HUB MAN/WAN port Ring port 2Ring port 1 Ring section 1Ring section 2 > Records ring port providing least-cost path to ONU in table > This port is used for forwarding data to ONU > HUB regularly checks connectivity status of ring > Reacts to faults reported by ONUs by updating lookup table > Uses alternate path to ONUs to route around faults

5 S. Chennu, K. Habel, K.-D. Langer The ONU Entity > Designed to be a simple, low-cost device > Two ring ports and one LAN port > Each ring port assigned a cost > Has a unique ID used for addressing it within the ring ONU End user/LAN port Ring port 2Ring port 1 > Registers itself with the HUB on initialization > Labels its ring ports as PRIMARY and SECONDARY > PRIMARY port provides least-cost default path to HUB > Periodically pings HUB to report status and notify detected faults > ONUs affected by a fault switch to using their SECONDARY port > Failed ONUs are eventually removed from the HUB lookup table

6 S. Chennu, K. Habel, K.-D. Langer A Brief Outline > Link layer architecture for protected access rings > The Fast Access Ring Protection Protocol (FARPP) > QoS-awareness in the access ring > Simulative evaluation of FARPP > Conclusions

7 S. Chennu, K. Habel, K.-D. Langer ONU Registration > ONU sends out JOIN messages on both ports on initialization > Path cost stored in messages incremented by each downstream ONU > HUB computes least-cost path to ONU using received JOINs > Registers ONU in lookup table and replies with JOIN ACK on least- cost path > ONU registers port providing least- cost path as PRIMARY HUB PRI SEC PRI SEC PRI SEC PRI SEC PRI JOIN JOIN ACK

8 S. Chennu, K. Habel, K.-D. Langer Event-based Fault Detection > Link layer receives interrupts from physical layer > Affected ONU reconfigures itself > Sends out FAULT frames on working port > FAULT frames trigger reconfiguration at ONUs along downstream path > HUB updates its topology on reception of FAULT frames > Secondary Timers-based mechanism as fallback > Configurable number of timer expiries control fault detection latency HUB PRI SEC PRI SEC PRI SEC PRI SEC PRI FAULT

9 S. Chennu, K. Habel, K.-D. Langer Frame reflection > ONUs neighboring a fault reflect frames instead of forwarding > Such frames are marked as REFLECTED_FRAME > And returned to the HUB > HUB marks them as DATA_FRAME and forwards them on alternate path > Frames reach recipient out of sequence and delayed > QoS-aware reflection reduces frame loss for high priority traffic during fault recovery HUB PRI SEC PRI SEC PRI SEC PRI SEC PRI DATA REFLECTED DATA

10 S. Chennu, K. Habel, K.-D. Langer A Brief Outline > Link layer architecture for protected access rings > The Fast Access Ring Protection Protocol (FARPP) > QoS-awareness in the access ring > Simulative evaluation of FARPP > Conclusions

11 S. Chennu, K. Habel, K.-D. Langer Background: QoS classes in MUSE > Borrows from recommendations by ITU and 3GPP > 4 QoS classes proposed > Classifies data streams based on two primary differentiators Elasticity Interactivity > Further differentiators (Symmetry, Bandwidth requirement) can be used to construct complete QoS class tree ElasticityInteractivityTraffic ClassApp Example Elastic Non-interactiveBackground (BKG)File Download InteractiveInteractive (INT)Web browsing Inelastic Non-interactiveStreaming (STR)VoD, Radio InteractiveConversational (CON)VoIP, Gaming

12 S. Chennu, K. Habel, K.-D. Langer QoS Awareness > VLAN ID (IEEE 802.1Q) and Priority bits (IEEE 802.1p) encode QoS information in data frames > ONU has to efficiently multiplex transit data with incoming and outgoing data > Ring interface queue at ONU classifies and queues frames according to traffic class > Queuing policy determines scheduling order > Priority queuing (Non-preemptive) has been adopted > Has been shown to be a simple and cost-effective solution > During faults, in case of background class traffic is preferentially dropped in favor of higher priority traffic

13 S. Chennu, K. Habel, K.-D. Langer A Brief Outline > Link layer architecture for protected access rings > The Fast Access Ring Protection Protocol (FARPP) > QoS-awareness in the access ring > Simulative evaluation of FARPP > Conclusions

14 S. Chennu, K. Habel, K.-D. Langer Simulation Setup > Uses NS-2 to simulate network stack using modular components > Simulation scenarios create worst-case conditions for 100 Mbps links > Bandwidth allocated per ONU and per traffic class > Queues dimensioned using estimates from Queuing Theory

15 S. Chennu, K. Habel, K.-D. Langer Path Restoration Time (PRT) Scaling > PRT is end-to-end restoration delay > Plotted against increasing ring size > Measured with traffic distribution between traffic classes > In 100-ONU Ring: ~20 ms for CON and STR classes ~ 32 ms for INT class ~60 ms for BKG class

16 S. Chennu, K. Habel, K.-D. Langer Per-ONU Queuing Delay > Queuing delay at most heavily-loaded link in a 50-ONU ring > Measured during normal operation and faults > Probability distribution for each traffic class plotted > Only BKG traffic class sees big increase during faults

17 S. Chennu, K. Habel, K.-D. Langer A Brief Outline > Link layer architecture for protected access rings > The Fast Access Ring Protection Protocol (FARPP) > QoS-awareness in the access ring > Simulative evaluation of FARPP > Conclusions

18 S. Chennu, K. Habel, K.-D. Langer Conclusions and Future Work > A QoS-aware link layer protection scheme for access rings outlined > Centralized network management model exploits natural breakdown of responsibilities between HUB and ONU > Performance of FARPP in mediating low-latency fault detection and recovery demonstrated To Do > Detailed study of operational and dimensioning parameters to optimize operation of FARPP in a real access network > Translation of user-level fairness into bandwidth allocation scheme at ONUs

19 Thank You

20 S. Chennu, K. Habel, K.-D. Langer Existing Protection Schemes and FARPP Feature ► Scheme ▼ CostSpeed Suitability for Bursty Traffic FlexibilityComplexity Inter- operability Optimality for Access Rings SDH–<50 ms––o+– RSTP+2 – 30 s++++– RPR–<50 ms++–+– EAPS RFER T-Metro o<50 ms+++o– FARPP ms +++o+

21 S. Chennu, K. Habel, K.-D. Langer Fault reporting > ONUs encode link state information in HELLO and FAULT frames > Sent out at regular intervals and in response to faults > HUB can collate reported status to build a complete picture of ring topology > Topology view and changes can be reported to suitable management layer HUB PRI SEC PRI SEC PRI SEC PRI SEC PRI FAULT(DOWN:UP) FAULT(UP:DOWN) HELLO(UP:UP) FAULT(UP:UP)

22 S. Chennu, K. Habel, K.-D. Langer FARPP Message Passing > FARPP frames carry administrative messages in the ring > Header format follows Ethernet compliant structure > Maintains interoperability and minimizes protocol overhead > VLAN ID (IEEE 802.1Q) and Priority bits (IEEE 802.1p) encode QoS information in data frames > Header inserted/removed into/from data frames at entry/exit points to/from ring Dest MAC Addr (48) Source MAC Addr (48) FARPP Type (3) ONU ID (32) FARPP Protocol Specific Information (32) Reflected Bit (1)Unused (12)Ethernet Type (16) Timestamp (64)


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