We compile and classify the research work conducted for Ethernet passive optical networks. We examine PON architectures and dynamic bandwidth allocation algorithms. Our classifications provide meaningful and insightful presentations of the prior work on EPONs. The main branches of our classification of DBA are: grant sizing, grant scheduling, and optical network unit queue scheduling. We further examine the topics of QoS support, as well as fair bandwidth allocation. The presentation allows those interested in advancing EPON research to quickly understand what already was investigated and what requires further investigation. We summarize results where possible and explicitly point to future avenues of research.

Ethernet passive optical network architectures and dynamic bandwidth allocation algorithms

A survey of dynamic bandwidth allocation algorithms for Ethernet Passive Optical Networks

We present an experimental analysis of on-off patterns in voice over IP (VoIP), where we study the talk-spurt/gap distribution produced by two modern silence detectors: ITU G.729 Annex B Voice Activity Detector (VAD) and NeVoT Silence Detector (SD). The results indicate that spurt/gap distributions are fairly sensitive to both the sound volume and the type of silence detectors, but all showed that the traditional assumption of exponential distribution does not always fit well with the audio sessions we recorded. Both the spurt and gap distributions are more "heavy-tailed" than the exponential curve. In particular, the gap distribution deviates much more strongly from the exponential model, even when "hangover" is applied. To estimate how such deviation affects VoIP applications, we investigate the performance of voice traffic multiplexing. In particular, we look at the probability of having a out-of-profile packet (p/sub o/) when a token bucket filter is placed at the multiplexing end. We ran a series of simulations under three increasingly accurate settings: the exponential model, the real CDF, and the raw silence detector outputs. The token bucket results are robust with regard to the details of the distribution. This is particularly true when the multiplexing factor N is large and the token buffer size B is not too big. When N is small and/or B is big, however, the estimated p/sub o/ under the real CDF is about 30% to 200% larger than under the exponential model. The relative difference between the raw silence detector outputs and the real CDF is generally much smaller than between the real CDF and the exponential model. Therefore, the data traffic in VoIP has a small temporal correlation and a secondary effect on the multiplexer performance.

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Analysis of on-off patterns in VoIP and their effect on voice traffic aggregation

Building on the Ethernet Passive Optical Network (EPON) and Gigabit PON (GPON) standards, Next-Generation (NG) PONs (i) provide increased data rates, split ratios, wavelengths counts, and fiber lengths, as well as (ii) allow for all-optical integration of access and metro networks. In this paper we provide a comprehensive probabilistic analysis of the capacity (maximum mean packet throughput) and packet delay of subnetworks that can be used to form NG-PONs. Our analysis can cover a wide range of NG-PONs through taking the minimum capacity of the subnetworks forming the NG-PON and weighing the packet delays of the subnetworks. Our numerical and simulation results indicate that our analysis quite accurately characterizes the throughput-delay performance of EPON/GPON tree networks, including networks upgraded with higher data rates and wavelength counts. Our analysis also characterizes the trade-offs and bottlenecks when integrating EPON/GPON tree networks across a metro area with a ring, a Passive Star Coupler (PSC), or an Arrayed Waveguide Grating (AWG) for uniform and non-uniform traffic. To the best of our knowledge, the presented analysis is the first to consider multiple PONs interconnected via a metro network.

Capacity and Delay Analysis of Next-Generation Passive Optical Networks (NG-PONs)

We analyze the mean packet delay in an Ethernet passive optical network (EPON) with gated service. For an EPON with a single optical network unit (ONU), we derive (i) a closed form delay expression for reporting at the end of an upstream transmission, and (ii) a Markov chain-based approach requiring the numerical solution of a system of equations for reporting at the beginning of an upstream transmission. Reporting at the beginning, which has not been previously examined in detail, achieves significantly smaller delays than reporting at the end of an upstream transmission for a small number of ONUs. Both of these analyses are fundamentally different from existing polling system analyses in that they consider the dependent switchover times of the EPON. We extend the analysis for reporting at the beginning of an upstream transmission to approximate the mean packet delay in an EPON with multiple ONUs and verify the accuracy of the analysis with simulations. Overall, our numerical results indicate that for utilizations up to ~75%, the mean packet delay is close to its minimum of four times the one-way propagation delay.

Delay analysis of Ethernet passive optical networks with gated service

This paper proposes a new dynamic bandwidth allocation system for Ethernet Passive Optical Networks (EPONs), subject to requirements of fairness, efficiency, and cost. An Optical Line Terminal (OLT)-centric bandwidth allocation model is proposed which employs a credit pooling technique combined with a weighted-share policy to partition the upstream bandwidth among different classes of service, and to prevent Optical Network Units (ONUs) from monopolizing the bandwidth. The OLT-centric model allows global optimization of network resources, a characteristic which is not found in many earlier proposals. Supported by the new bandwidth allocation, the paper proposes a joint-ONU interval-based packet scheduling algorithm, referred to herein as COPS (Class-of-service Oriented Packet Scheduling), that meets the requirements set out above. We compare COPS with another well-known scheduling algorithm which employed a standard priority-based bandwidth sharing. We show that COPS is superior in terms of network utilization and maximum packet delay, with the consequence of an increase in average packet delay for the premium traffic. This drawback is overcome by combining COPS with a rate-based optimization scheme.

A joint-ONU interval-based dynamic scheduling algorithm for ethernet passive optical networks

Dynamic bandwidth allocation (DBA) schemes in Ethernet passive optical networks (EPONs) have been studied by several investigators. However, most of these schemes cannot provide efficient network utilization while supporting fair, deterministic service to end-users. In this letter, a novel OLT-based bandwidth allocation model is proposed that employs a credit pooling technique to partition the network bandwidth among different classes of service. High network utilization is achieved by embedding ONU scheduling decisions in time and by eliminating the channel idle-time overhead, associated with many earlier DBA schemes.

A fast class-of-service oriented packet scheduling scheme for EPON access networks

Through comprehensive simulation studies, we have evaluated the ATM layer end-to-end performance of a constant bit rate (CBR) MPEG2 connection. For most practical cases that we have considered, a cell delay variation (CDV) value of 160 /spl mu/sec is obtained (using 155 Mbps OC-3 rate), well below the 1 msec worst case stated in prior studies. The results also indicate that the uniform distribution proposed in the ATM Forum provides a pessimistic model for the cell delay variation. We demonstrate that a gamma distribution adequately models the cell delay and delay variation (CDV). We also study the effect of various network/source parameters (such as the background load, the number of background sources, the number of hops, and the link-speed) on the variances of CDV and the end-to-end delay of the reference connection. Finally, we examine the variation in the cell delay correlation of a reference connection with the above parameters. We show that the correlation is a decreasing non-periodic/periodic function if the reference CBR is multiplexed with the same/other classes of CBR connections.

A simulation study of delay and delay variation in ATM networks .I. CBR traffic

Status of This Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as " work in progress. " To view the entire list of current Internet-Drafts, please check the " 1id-abstracts.txt " listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). Abstract We study the performance of the Constant Bit Rate (CBR) and the interpolated ON-OFF voice over the differentiated services Internet. Both the Premium and Assured services are tested, and their relative performance is investigated. Using these services, at the DS3 rate, the call handling capacity can be doubled, at the expense of packetization delay and a few milliseconds packet delay. Also, at a reasonable load level, if the Assured flows are smooth their playout delay could be limited to a few milliseconds. This is true even in the presence of the higher-priority Premium flows. The loss rate of the Assured packets at the RIO buffer is observed to be within the order of 10 ?06 , where as the best effort packet loss rate is within the order of 10 ?02. Finally, shaping the Premium traffic draft-naser-voice-diffserv-eval-00.pdf 2 reaches diminishing returns; shaping could often exceedingly increase the end-to-end delay and jitter of the Premium traffic.

Voice over Differentiated Services

This chapter studies the rich feature set of the IEEE 802.3 family of standards for the control of information transfer and for supporting dynamic bandwidth allocation in Ethernet passive optical networks (EPONs). We will study a medium access control protocol, known as multi-point control protocol (MPCP), which arbitrates access to the upstream channel and supports bandwidth allocation in EPON. The precise format of the MPCP messages as well as their processing will be given. The concept of threshold queue reporting will be presented, which is used by the end-user devices (ONUs) to report detailed information regarding the status of the individual queues to the network. The ranging process and automatic discovery of newly connected or off-line ONU stations will also be given.

Hassan Naser

Papers

A joint-ONU interval-based dynamic scheduling algorithm for ethernet passive optical networks

A fast class-of-service oriented packet scheduling scheme for EPON access networks

A simulation study of delay and delay variation in ATM networks .I. CBR traffic

Voice over Differentiated Services

Dynamic Bandwidth Allocation for Ethernet Passive Optical Networks