MAC Layer Algorithms for PON and Hybrid PON Access Networks

PhD Comprehensive Exam: March 5th , 2014

Anu Mercian

Committee Members:

Martin Reisslein (Chair)

Michael McGarry

Cihan Tepedelenlioglu

Yanchao Zhang

Agenda• Introduction• Passive Optical Networks• Dynamic Bandwidth Allocation (DBA)• Extension-DBA: Multi-thread Polling• Remote Message Scheduling • Roadmap to Dissertation• PON-DSL• PON-Wireless or FiWi (Fiber-Wireless)• Conclusion

Introduction

• Basic PON structure: – EPON IEEE 802.3ah (1Gbps), IEEE 802.3av (10Gbps)– GPON ITU-T G.984, ITU-T G.987

OLT

ONUsplitter

ONU

ONU

0-15Km

0-5Km

PON Analysis• Importance of PON MAC Layer Analysis: Upstream Traffic

Modeling • What changes can we bring in and where: Central Office for

effective DBA. Other functions can be Routing, Load Balancing, Controllability

• PON Cycle: REPORT and GRANT

DBAs and their importance• Grant Scheduling Framework: Offline and Online.• Grant Sizing Framework: Gated, Limited, Excess• Grant scheduling Policy: SPD

Offline Scheduling

Online Scheduling

Long-Reach PON• Long range PON, advantageous - Multi- thread polling[1]. The

original technique was based on “Offline” and we introduced a complementary DBA for LRPON, called Online MTP with much lower delay.

OLT

ONUsplitter

ONU

ONU

90-100Km

[1] Huan Song; Byoung-Whi Kim; Mukherjee, B., "Multi-thread polling: a dynamic bandwidth distribution scheme in long-reach PON," Selected Areas in Communications, IEEE Journal on , vol.27, no.2, pp.134,142, February 2009

Extensive Analysis of MTP*

• Offline MTP[1] : Multi-thread polling with stop– OLT waits end of each thread for REPORTs from all ONUs. – Therefore, Interleaving the RTT for LRPON.

• Online MTP : Mutli-thread polling with online scheduling framework. – OLT processes each bandwidth request immediately. Avoids 2г waiting time– Achieves much lower delay than MTP Offline

• Average Delay and Channel Idle time analysis• Implementation of Online Excess Bandwidth Distribution (OEBD) • MTP Extension to GPON

* Anu Mercian, Michael P. McGarry, and M. Reisslein. Offline and Online Multi-Thread Polling in Long-Reach PONs: A Critical Evaluation,  IEEE/OSA Journal of Lightwave Technology, 31(12):2018-2028, June 2013. 

MTP Offline & Online

Quantitative AnalysisDifference of MTP On and MTP Off

Online Excess Bandwidth

Thread Tuning: To balance the threads from one thread monopolizing the cycle bandwidth

Idle time Evaluation

Simulation Set-up

• IEEE 802.3ah, REPORT and GRANT – 64 Bytes, tg = 1us• ITU-T G.984, DBRu and BW Maps – 4 Bytes every 125us, tg = 30ns• Capacity (C) = 1Gbps• Self-similar packet generation, Long-tail distribution with Hurst

parameter 0.75• Quad Mode packet distribution – 60% 64 bytes, 4% 300 bytes, 11%

580 bytes, 25% 1518 bytes, CSIM based C Simulator for EPONSIM

Online Excess Algorithm

Bounded excess pool Online Excess: Pool size

Simulation ResultsAverage Delay for Z=2ms Average Delay for Z=4ms

Average Delay for Z=8ms

𝑈=𝑍

𝑍+2𝜏

MTP Offline and MTP online

MTP offl. and STP off. exc

STP off. Exc and MTP off

STP on lim and MTP off.

Observation Parameters for Z=4ms1. Average Cycle Time (Z)2. Average Grant Duration (G)3. Average Idle Time (I)

Grant size of MTP off > Grant size of MTP on

Idle time for MTP off & on are same

Avg cycle time of STP off. Exc Gated are slightly higher.

GPON Results

• Delay slightly higher only for Z=2ms, but the delay performance is very similar to EPON.

• Higher delay is because of static periodic signaling of bandwidth requests and upstream transmission window in GPON frame.

Average Delay for Z=2ms

MTP Online Conclusions

• MTP online reduces channel idle time compared to MTP offline• Offline MTP gives lower delay than offline STP but not online

STP for LRPON. • MTP online, STP online excess and DPP excess gives

somewhat similar and lowest delay performance.• For Z = 8ms, DPP and STP online excess will be sufficient so

that the extra overhead and complexity of MTP Online can be avoided.

PON Control Messages• For EPON (IEEE 802.3ah, IEEE 802.3av) – Standard

has 64 bytes Control messages are GRANT and REPORT. • (IEEE) No specific scheduling of Control Messages.

– GRANT (OLT ONU) – REPORT (ONU OLT)

• For XGPON (ITU-T G.984 and ITU-T G.987) – Control message sent every 125us of (4 Bytes)

• Control Messages are sent at the beginning of Upstream TX. – T-CONT (Transmission Container) (OLT ONU) – DBRu (Dynamic Bandwidth Rate Upstream) (ONU OLT)

• Literature considers REPORT sent only at the end of upstream transmission mostly.

Report Message Scheduling#

• RMS can be done in three different ways:• 1. Sent at the beginning of payload transmission – scheduling

decision can be taken and grant sent before the packet upstream transmission

• 2. Sent at the end of payload transmission – can report newly arrived packets in-between packet upstream transmission

• 3. Dynamic Optimization of RMS: (Offline Scheduling Framework) – Report sent at the end for O-1 ONUs and sent at the beginning for the Oth ONU.

# Anu Mercian, Michael P. McGarry, Martin Reisslein. Impact of Report Message Scheduling (RMS) in 1G/10G EPON and GPON, Optical Switching and Networking, 12:1-13, April 2014.

Quantitative Analysis

Time instant of end of arrival of upstream transmission:

Now, we can say that scheduling instant (γ) for beginning is always less or equal to end:

Idle time evaluation:

Dynamic RMS Scheduling

• Effect of Number of ONUs – Lesser number of ONUs, more effect of “Report in the beginning” vs “Report in the end”

• Dynamic RMS and Report in the beginning give very similar performance.

Simulation ResultsSimilar simulation set-up as earlier.

Average Delay for Z=2ms

Z=4ms

Z=8ms

S off. limand S off. exc

S Off gat

STP on. Lim and excMTP on.

DPP

Average Idle Time (I)

Z=2msZ=4ms

Z=8ms

Average Delay for Z = 4ms for xGPON Average Idle Time for Z = 4ms for xGPON

Average Delay for C=10Gbps ChannelZ=2ms

Z=4ms

Z=8ms

Average Idle Time for C=10Gbps ChannelZ=2ms

Z=4ms

Z=8ms

Average Delay for C=10GbpsZ = 4ms for xGPON

Average Channel Idle Time for C=10GbpsZ = 4ms for xGPON

Conclusions to RMS

• Report in the beginning lower delay for Offline framework• 10Gbps performance analysis• Analysis for xGPON• Online STP and MTP and DPP – The RMS is not a problem.

Publications

• Anu Mercian, Michael P. McGarry, Martin Reisslein. Impact of Report Message Scheduling (RMS) in 1G/10G EPON and GPON, Optical Switching and Networking, 12:1-13, April 2014.– Impact of Report Message Scheduling (RMS) in 1G/10G EPON and GPON (Extended Version

)

A Mercian, MP McGarry, M Reisslein - arXiv preprint arXiv:1312.0994, 2013

• Anu Mercian, Michael P. McGarry, and M. Reisslein. Offline and Online Multi-Thread Polling in Long-Reach PONs: A Critical Evaluation, IEEE/OSA Journal of Lightwave Technology, 31(12):2018-2028, June 2013. – Offline and Online Multi-Thread Polling in Long-Reach Pons: A Critical Evaluation (Extended

Version)

A Mercian, M McGarry, M Reisslein - Arizona State University, Tech. Rep., Feb, 2013

Roadmap to Dissertation

• Hybrid PON Access Networks• Compatibility with transmission medium such as

Copper Cables and Wireless. • Therefore, extended research of PON in tandem with

DSL and Wireless

PON DSL• PON back-haul networks with existent DSL cables would reduce

additional installation costs• FTTdp – Fiber to the drop point• Drop point – ONU-DSL Unit that bridges copper and fiber

transmissions.

OLT

ONU Droppointsplitter

ONUDropPoint

ONUDropPoint

Short Range orLong Range

0-5Km

Flow Control to PON-DSL

• Current Ethernet standard for Flow Control – PAUSE frame

[3] M.P. McGarry, Y. Luo, and E. Gurrola "On the Reduction of ONU Upstream Buffering for PON/xDSL Hybrid Access Networks", IEEE Global Communications Conference, Atlanta, Georgia, December 9-13, 2013

DBA based Flow Control• A recent flow control technique introduced: GATED

Flow Control [3]• The OLT decides the polling of the DSL-CPE• Advantages:

– Reduced packet loss, – Lowers ONU Buffering thus reduced costs, – stable delay performance, – reduced delay performance for LRPON

• Future directions: DSL Overhead is higher than PON, thus there is Grant sizing problems and differential grant sizing

PON-Wireless or FiWi

OLT

ONUsplitter

ONU

ONU

0-10Km

GW

GW

WLAN

200 m

0-5Km

Configuration• ONUs [1-4] Wireless Traffic• ONUs [5-8] Wired Traffic

PON DBA with FiWi

• Motivation: Net Utility of ONU connected to WLAN < Maximum Utility of WLAN (IEEE 802.11g) – 54Mbps

• Thus, (ONU-WiFi) Є Underloaded ONUs• Unused bandwidth of ONU-WiFi can be used for Overloaded

ONUs with wired Traffic. • Therefore, DBAs like Excess Bandwidth Division will be very

useful for FiWi Architecture.

Concluding notes

• MTP online, excess – on average the best performing DBA • Remote Message Scheduling – Our optimum scheme (Report in

the end for O-1 ONUs and report in the beginning for Oth ONU for Offline techniques)

• PON-DSL Flow Control and grant sizing issues• PON-Wireless – DBA for better BW utilization

Publications & References• [1] Huan Song; Byoung-Whi Kim; Mukherjee, B., "Multi-thread polling: a dynamic bandwidth distribution

scheme in long-reach PON,"  Selected Areas in Communications, IEEE Journal on , vol.27, no.2, pp.134,142, February 2009

• [2] Michael P. McGarry and Martin Reisslein. Investigation of the DBA Algorithm Design Space for EPONs, IEEE/OSA Journal of Lightwave Technology 30(14):2271-2280, July 2012.

• [3] M.P. McGarry, Y. Luo, and E. Gurrola "On the Reduction of ONU Upstream Buffering for PON/xDSL Hybrid Access Networks",IEEE Global Communications Conference, Atlanta, Georgia, December 9-13, 2013

THANK YOU

Prof. Martin ReissleinDr. Michael McGarry

Dr. Cihan Tepedelenlioglu Dr. Yanchao Zhang

My sister, AnjuLab mates: Yousef, Revak, Xing, Po, Ziyad

Friends: Chris, Rushil and Suhas

Thank you for taking time to attend my Comprehensive