Nobel-WP3 QoS management

1. Nobel-WP3QoS management Miroslaw Klinkowski Davide Careglio Josep Solé-Pareta NOBEL meeting, Munich

2. QoS in OBS The elements of QoS provisioning • Signaling • absolute QoS by wavelength reservation in 2-way reservation mode • QoS routing • Techniques for QoS management in nodes • Edge nodes • Offset-time differentiation • Varying burst assembly parameters • Class based queuing • Core nodes • Mechanisms in contention resolution • Priority scheduling of control packets • Definition of Classes of Services • Admission Control • both in Edge and Core nodes NOBEL meeting, Munich

3. QoS in OBS Mechanisms in contention resolution • Reservation schemes with thresholds – reservation of a different number of resources for High and Low priority traffic • with -threshold • with FDL threshold • Intentional dropping – initiated according to either loss rate measure or traffic profile to guarantee burst loses on defined levels • Burst preemption • of all bursts • partially with the segmentation NOBEL meeting, Munich

4. blocking Long burst Short bursts reservation l1 l2 l3 l4 t Contention Resolution Burst Length Differentiation • Considerable burst lengths result in an increase of the burst contention probability in the network what produces higher burst losses. • Long bursts are more susceptible to contention than the short ones since the later have much more chances to fill voids between the bursts already stored and/or to access to the FDL buffers (if present). • Therefore in order to assist the contention resolution problem as well as for QoS purposes the application of burst length differentiation (BLD) that for different classes of traffic assigns different classes of burst lengths is considered. NOBEL meeting, Munich

5. Contention Resolution Burst Length Differentiation • Considerable burst lengths result in an increase of the burst contention probability in the network what produces higher burst losses. • Long bursts are more susceptible to contention than the short ones since the later have much more chances to fill voids between the bursts already stored and/or to access to the FDL buffers (if present). NOBEL meeting, Munich

6. Control packets • FDLs • Bursts • IN • OUT • Reservation Unit Burst Length Differentiation QoS assistance • Edge node • Core node • IP packets • classifier • assembler • Both HP and BE classes can use mixed time/burst-length assembly algorithm in the edge nodes to build burst units • Nonetheless, in the BLD strategy the high priority bursts are aggregated with lower timer and maximum burst length thresholds than the low priority ones. • HP • BE • OBS network NOBEL meeting, Munich

7. Burst Length Differentiation Traffic model • The traffic is uniformly distributed between all input and output ports with mean load per input channel (wavelength) equal to 0.8 Erlang. The percentage of HP bursts over the total traffic is called . • The mean size of HP bursts (MBLHP) can be 5 or 10 kbytes while it is 40 kbytes for the BE bursts (MBLBE). • The IATs are Gaussian distributed. For scenarios without BLD a mean IAT is equal to 51.79ms. When BLD is applied the IAT depends on actual  parameter. The distributions of IAT and the burst length; 1) IAT on the output of the aggregation unit (normal distributed), 2) IAT in the link (quasi-gamma distributed) and 3) burst lengths (the sum of 2 normal distributions NOBEL meeting, Munich

8. Burst Length Differentiation Evaluation • BLD does not bring any significant profit in scenarios without FDLs • some class isolation ratio is achieved with FDLs applied • shorter HP Mean Bursts Length (MBLHP=5kB) offer better BLPTotal in comparison to both BLD with MBLHP=10kB and no-BLD scenarios • since BLD alone does not provide high class isolation ratio, the study on BLD combined with other QoS mechanisms will be performed NOBEL meeting, Munich

9. QoS mechanisms Offset-Time Differentiation Time Control Packets • An additional offset-time (OT) is assigned to high priority bursts, what results in an earlier reservation, in order to favors them while the resources reservation • Extra QoS offset have to be in the order of a few burst durations of lower priority bursts • Pros: This technique keeps constant the total blocking probability while reduces the loss probability of high priority bursts • Cons: The main disadvantages are sensitivity of high priority class to both burst length characteristics and offset-time distributionsas well as propagation delay basic OT LP burst basic OT extra OT HP burst blocking resources reservation Data Bursts Existing reservations NOBEL meeting, Munich

10. QoS mechanisms Burst Preemption • QoS is provided in the core switch by preempting low priority burstreservation • partial: with burst segmentation • full: without burst segmentation • Cons: • The pre-emption introduces signaling overhead – downstream nodes has to be informed about preemption in order to update their reservation ‘database’ • A segmentation technique, which first was introduced in order to decrease burst loss probability in OBS networks and then to assist the QoS introduces additional complexity NOBEL meeting, Munich

11. Comparison of QoS mechanisms The objectives • Evaluation of performance characteristics of QoS techniques under the same simulation scenario in order to recognize their pros and cons • Two different classes of service: • High Priority (HP) – to transport loss/delay sensitive traffic like real-time voice; • Best Effort (BE) – for regular data traffic are considered. • Application of both JET reservation protocol with a void-filling scheduling algorithm and FDLs for contention resolution is considered • performance results for the nodes without FDL buffering are usually poor • Following techniques are studied: • Offset-Time Differentiation (OTD) • Burst Preemption (BP) without segmentation • Each HP burst is allowed to preempt at most one BE burst in case there is no free wavelength resources to be allocated • Burst Length Differentiation (BLD) as an assistant technique NOBEL meeting, Munich

12. Comparison of QoS mechanisms Node scenario • LAUC-VF_MIN-SV scheduling algorithm -derived from the LAUC-VF. Aims in minimization voids introduced between new scheduled bursts and the preceding one • A general OBS node architecture with full connectivity and wavelength conversion, acting as an output queuing switch is considered. The switch has 4x4 input/output ports and 4 wavelengths per port, each one operating at 10 Gbps. • The OBS switch uses a feed-forward FDL configuration with 4 delay lines. The delays provided are linearly increasing with a granularity G = 1 expressed as a fraction of the MBLBE. • Evaluated metrics: • The throughput • The burst loss probability(BLP) obtained for both HP (BLPHP) and BE (BLPBE) traffic in the function of  (percentage of HP traffic load) … also • effective byte transfer • preemption rate • 10-6= max.  (relative HP traffic load) that guarantees BLPHP < 10-6 will be studied NOBEL meeting, Munich

13. Comparison of QoS mechanisms OTD vs. BP: BLPs • In each scenario the FDLs has been introduced • BLD improves the performance in both OTD and BP scenarios when we compare the results with the BLD-less case. • When decreasing the HP traffic load ratio its BLP decreases as well, what seems to be obvious for QoS schemes that doesn´t implement early burst dropping algorithms (or not ?). • Comparing the results obtained for both OTD and BP in BLD and BLD-less scenarios, we can see that the BP benefits much more from the BLD then the OTD. Moreover, BLD improves BP scheme providing fine QoS differentiation without affecting the throughput. NOBEL meeting, Munich

14. Comparison of QoS mechanisms Conclusions • The Burst Length Differentiation technique where each class of traffic is aggregated with different buffer size thresholds has been studied • When applied alone, it does not provide high class isolation ratio • BLD improves the overall QoS performance of the OBS networks when applied together with other QoS mechanisms like Offset-Time Differentiation or Burst Preemption. • In particular, combined BLD with BP scheme seems to introduce less complexity than in the preemption with segmentation scenario. • In order to check if the BLD&BP without segmentation could substitute BP with segmentation the next step in this study will be an evaluation and comparison of the performance of both scenarios. NOBEL meeting, Munich

15. Nobel-WP3Routing in OBS Miroslaw Klinkowski Davide Careglio Josep Solé-Pareta NOBEL meeting, Munich

16. Two different approaches • Put the traffic where the bandwidth is • Routing approach • Need adaptive routing mechanism • Put the bandwidth where the traffic is • Planning / dimensioning approach • Need simple shortest path algorithm or similar NOBEL meeting, Munich

17. Routing in OBS General assumptions • Network study • JET resources allocation • Nodes equipped with FDLs • Resource assignment based on: • Horizon scheme: MINGAP, MINLEN • Void Filling scheme: VF, VF-start, VF-maxmatching NOBEL meeting, Munich

18. Routing in OBS A critical feature • Set of the offset-time in the control packet Offset-time is calculated in the edge node on base of a sum of processing times in all consecutive nodes lying on the path the burst is transmitted on. In order to calculate optimal (minimal) value of offset-time the number of nodes the burst is going through should be know. Deflection routing scheme allowed only if offset-time is high enough Note: for small processing times (tens of [ns] ?) these constraints may not be so significant NOBEL meeting, Munich

19. Routing in OBS Contribution to the D23 • Connection-oriented environment with LSP paths and source-base routing • Shortest path (SP) routing • Isolated routing based on bypass based routing (BBR) • Connection-less environment with hop-by-hop decisions • Isolated routing based on hot potato mechanism NOBEL meeting, Munich

20. Routing in OBS Contribution to the D23 • Topologies • Simple 6-nodes • NSFNet • EON • Results • Burst Loss Probability • End-to-end delay NOBEL meeting, Munich

21. Routing in OBS Contribution to the D32 • Distributed mechanism based on some feedbacks on the states of the nodes (like Internet) • Feasible approach for both connection-oriented and connection-less environments NOBEL meeting, Munich

22. Routing in OBS Ideas • Taken from ATM networks, e.g. from [Pareta95]: • a number of paths (e.g. k-shortest paths) pre-established between every pair of nodes • path selection according to the probabilities assigned to the paths • the probabilities are dynamicaly updated (every specific period of time) according to the feedback information from the network about congestion on the paths • Possibility of using the BBR concept [Masip03] with multipath routing • a number of path pre-established • a feedback information about congested links on the paths obtained from the network (every period of time) • congested links = OSL links • an information about OSL links included into the proces of path reconfiguration; reconfigured path will by-pass the congested links [Pareta95]J. Sole-Pareta, D. Sarkar, J. Liebeherr, I.F. Akyildiz, “Adaptive multipath routing of connectionless traffic in an ATM network”, ICC 95 Seattle “Gateway to Globalization” 1995 IEEE International Conference , vol. 3, pp.1626 – 1630, 18-22 Jun. 1995. [Masip03]X. Masip-Bruin, S. Sanchez-López, J. Solé-Pareta, J. Domingo-Pascual, “QoS routing algorithms under inaccurate routing information for bandwidth constrained applications”, in Proc. IEEE 2003 International Conference on Communications (ICC 2003), Anchorage, AL, May. 2003, pp. 1743-1748. NOBEL meeting, Munich

23. Routing in OBS General assumptions • Assumptions for the routing problem • Source-based – the routing decision at the edge node • Connection-oriented network like MPLS is considered • Multipath - a number of LSP paths pre-established • Adaptive • adaptation of weights assigned to LSPs • dynamic LPSs reconfiguration on base of the network state information • Per-burst routing decision (path selection) NOBEL meeting, Munich

24. Edge node Link state information DB LSP’s statere-calculation 2 4 5 6 3 1 Link BLP … Core node 1-2 10-4 Dynamic re-configuration 2-3 10-3 Sending of either a periodical or accidental information towards the edge nodes Maintaining LSPs 2-5 10-4 Update … The selection of pre-established LSP from the table is performed for each new burst A feedback (e.g. periodical with links’ state inf. or incidental like when burst dropped, …) LSPs’ table Dest LSP Prob. … A feedback information from the network 1-2-3-4 0.7 4 1-2-5-6-4 0.25 … Routing in OBS General architecture NOBEL meeting, Munich

25. Routing in OBS Signalization • Feedback information from the network • Periodical – with information about state of the links (BLPs, resources occupancy, …) or • Accidental – in case of lost of the burst • This information could contain the label of LSP path, the node in which the burst lost has occurred, class of the burst, … • Such information could be send only towards the edge node where the lost burst has been sent from • A mixed application of the schemes has to be justified yet NOBEL meeting, Munich

26. Routing in OBS Solutions • A way of representation the network state information could be as following • Assigned to the links: BLP, link load, wavelengths occupancy, … • Assigned to the LSPs: probabilities for LSP selection, … • Proper formulas have to be defined in order to translate the information obtained from the network into the parameters in the state tables • The networks state information as well as parameters in the tables could represent state of the network seen by different CoSs NOBEL meeting, Munich

27. Workplan NOBEL meeting, Munich