Analytical Approach to Dynamic Bandwidth Allocation Algorithm used in LRPON MS Thesis Defense + PhD Qualifiers Anu Mercian Committee Members: Martin Reisslein (Chair) Michael McGarry Cihan Tepedelenlioglu Yanchao Zhang

Agenda Passive Optical Networks (PON) Long-Range PON (LRPON) Dynamic Bandwidth Allocation (DBA) Part 1: Multi-threading Polling Part 2: Parallel Polling Part 3: Multi-polling techniques Conclusion Future Works

INTRODUCTION We live in a bandwidth-hungry world with services demanding superior performance in voice, data and video services

Passive Optical Networks When the physical layer is Optic Fibers, bandwidth obtained in the higher layers is promising © wikipedia

Structure of PON Downstream Traffic Upstream Traffic © [20] G. Kramer, G. Pesavento. Ethernet Passive Optical Network(EPON): Building a next Generation Optical Access Network

Evolution of PON APON – ATM passive optical networks BPON – Broadband PON (~622Mbps) EPON – Ethernet PON (more widespread(easy overlay)) GPON – higher bandwidth (larger variable length packets) (ITU G.984) GEPON – within the Ethernet, gigabit availability LRPON – long-reach to allow >20km (~100km) © Glen Kramer, Gerry Pesavento; Ethernet Passive Optical Network(EPON): Building a Next Generation Opitcal Access Network

Importance of LRPON High CapEx and OpEx involved in PON deployment to cover large area with a OLT/Central office for every 20Km of distribution LRPON covers 100Km reducing CapEx and OpEx Reduction in active sites leads to larger distances

Multi Point Control Protocol IEEE 802.3ah standard © Michael P.McGarry, Martin Reisslein, Martin Maier; Ethernet Passive Optical Network Architectures and Dynamic Bandwidth Allocation Algorithms

Dynamic bandwidth allocation Static Bandwidth Allocation – Each link is given a standard BW allocated. Disadvantages of SBA Necessity of Dynamic Bandwidth Allocation – Statistical Multiplexing Design Space [22]: –Grant scheduling framework –Grant sizing schemes –Scheduling Policies © [22] M.P. McGarry; M. Reisslein. Investigation of the DBA Algorithm Design Space for EPONs

Grant Scheduling framework Online or IPACT(Interleaved Polling with Adaptive Cycle time) Offline

Grant sizing schemes Fixed Gated Limited

Scheduling Policies Shortest Propagation Delay Shortest Grant or Shortest Processing Time First(SPT) Where τ is the half RTT

Problem Statement I LRPON promises less OpEx and CapEx but the large propagation delay gives poor delay performance. A Solution – Multi-thread polling (MTP)[16]. Discrepancies in MTP: MTP gives good delay performance when compared to offline scheduling framework. But is it better than online technique? © [16] H. Song et. al. Multi-thread polling: A Dynamic Bandwidth Distribution Scheme in LPON

Delay Analysis Polling delay Granting delay Queuing Delay Channel Utilization[22]

Multi-Thread Polling Idea is to send request before the previous Gate message is received creating a new thread © [16] H. Song et. al. Multi-thread polling: A Dynamic Bandwidth Distribution Scheme in LPON

Features of MTP Tuning Multiple Threads Inter-thread Scheduling Achieving Fairness

Reduced Delay in MTP Polling delay Granting Delay Queuing delay

MTP: Analysis MTP based on design space is (multiple-offline, excess) Polling delay for MTP is less because it has another opportunity in the same cycle Granting delay for IPACT is less because IPACT is online, and does not involve wait time Overall delay for IPACT is lower

Experiment Settings Simulator used: Simulator developed using CSIM discrete event simulation library Channel settings –Channel Capacity C = 1 Gbps –Number of ONUs M = 16 –Max Grant size = 7688bytes Self-similar traffic –Quad model packet size distribution –60% 64bytes, 4% 300bytes, 11% 580bytes, 25% 1518bytes Same distance between ONU and OLT

Results Distance between ONU and OLT = 100Km Overall Delay

Results Channel UtilizationOverall Delay Distance between ONU and OLT = 20 Km

Problem Statement II Offline technique was extended to obtain a multi- thread process which gave delay performance better than offline but not as good as IPACT. What if online was extended as a multi-process?

Concept of Parallel Polling Multiple online processes in parallel Motivation: –IPACT performs better than Multiple-offline threads so multi-online could be even better –Issues in Multi-thread process: Problem of wait time or idle time –Fairness Issue –Void formation

Parallel Polling: A possible solution Each cycle time has two threads in parallel with each one services as online

Advantages of PP PP is based on online grant scheduling framework, therefore low idle time and hence high utilization No issue of fairness issue as GRANT is given as per REPORTed Thread tuning will be required and compared between the effective cycle load Easy and simple implementation

Delay performance of PP Polling delay Granting delay Queuing delay

Delay Comparison Polling delay of PP will be slightly less than MTP as the cycle length of online process is less than the offline Granting delay for PP is very less when compared to MTP because of online technique Queuing delay is same for same simulator settings Therefore,

Results Distance between ONU and OLT = 100Km Overall Delay Channel Utilization

Results Distance between ONU and OLT = 20Km Channel Utilization Overall Delay

Problem Statement III MTP is better than offline scheduling framework PP is better than online scheduling framework So multiple polling of OLT is advantageous for LRPON?

Multiple polling techniques Multi-thread polling[16] Parallel Polling Double Phase polling[2], can be also called Multi- group polling © [2] S.Y. Choi et. al. Double Phase Polling Algorithm Based on Partitioned ONU Subgroups for High Utilization in EPONs

Results Distance between ONU and OLT = 100Km Channel Utilization Overall Delay

Results Distance between ONU and OLT = 20Km Overall Delay Channel Utilization

Conclusions MTP is good for LRPON when compared to offline but not when compared to online PP gives comparatively best delay performance for LRPON Multiple polling techniques in one cycle time gives promising results for LRPON with QoS awareness Channel utilization of PP and IPACT are high when compared to Multi-group, offline and MTP

Future Work Can scheduling policies be useful for techniques based on offline grant scheduling framework? Can fairness be achieved in PP using online excess bandwidth distribution (OEBD) PP a new technique and can be explored further. will it be promising for GPON as well? Can multiple polling techniques be of use to LRPON Consideration of performance of Real-time polling with respect to current multi-polling techniques

How will these DBA schemes perform with video and voice traffic. What if distances between ONU and OLT are random, how will the techniques perform? How can delay performance for PP be improved for SRPON.

THANK YOU and Questions?

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BACK UP

Basis study Availability of many DBA schemes in research brings a need to classify these DBA schemes based on their importance

Classification Description Existent classifications cover QoS aware and unaware but their usability is not explicitly mentioned Connecting scheduling framework to user traffic type and demand –Direct –Predictive –Intelligent

EPON-LRPON Classification

Usability Direct – User’s that require high throughput but do not compensate on fairness Predictive – User’s that have a flexible requirement Intelligent – When user’s of high load and low load are combined

Results: Poisson Channel Utilization Overall Delay 20Km 100Km

Results: Poisson 20Km 100Km Channel Utilization Overall Delay

Results: Poisson 20Km 100Km Channel UtilizationOverall Delay

Design Space Equations Offline Online DPP

MTP PP

Idle time Equations

Multi-thread Polling

Parallel Polling