C Design and Implementation of GEPON Architecture in Laboratory Testbed

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Abstract—This paper presents a proposition of GEPON

architecture for the didactic purpose. The GEPON architecture is implemented in access networks laboratory testbed. The paper includes a brief description of GEPON standardization, a description of laboratory GEPON equipment architecture and a short presentation of proposed laboratory exercises. The exemplary performance results are included.

The proposition of GEPON architecture testbed enables students to investigate Passive Optical Network (PON) architecture, services and maintenance of the system. The aim of proposed architecture is to familiarize the students with PON solution and cooperation PON solution with xDSL systems in access network or with METRO network. The proposed testbed architecture as a part of Next Generation Network is well inscribed in the needs of information society. For this reason its design and implementations is crucial in the didactic process of the technical university.

Index Terms—PON, GEPON, access network, ONU, OLT

I. INTRODUCTION

ONTEMPORARY society demands concerned with

high-definition HDTV, e-learning, online games, sophisticated multimedia services, require high capacity in the access network. Typical Digital Subscriber Line (DSL) solutions with one copper pair per user, with few kilometers distance and a speed limitation are not sufficient to satisfy information society requirements.

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The better proposition in such case is point-to-point (P2P) optical access network solution with dedicated fibers from Central Office (CO) to each end user subscriber. That approach from economic aspects is expensive due to the fact that it requires dedicated fiber deployment and optical transponders.

To reduce fiber installation cost and resolve traffic aggregation problem remote switch should be placed in the neighborhood of end users. Related to previous approach in this solution seriously limitation is requirement of electrical power supply.

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Manuscript received November 12, 2012. PON access network equipment, described in this paper was supported by the Regional Operational Program for Pomorskie Voivodeship for 2007-2012 years, Poland, under the Project "Technical infrastructure modernization of student labs at the Faculty of Electronics, Telecommunications, and Informatics at Gdansk University of Technology."

The authors are with the Department of Teleinformation Networks, Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, Gabriela Narutowicza 11/12 Street, 80-233 Gdansk, (e-mail: magdam@eti..pg.gda.pl, lechsm@eti.pg.gda.pl)

Switch replacement by low-cost passive optical element additionally minimizes the amount of optical transceivers, terminations, with no need to power supply. This solution named as Passive Optical Network (PON) [1] is generally considered to be the best in aspect of operating expenditures (OPEX) and capital expenditures (CAPEX).

In the article basics of design and implementation of Gigabit Ethernet Passive Optical Network (GEPON) architecture are presented. The paper is organized as follows. General information about GEPON architecture standardization and laboratory testbed are depicted in section II. Section III is devoted to proposition GEPON laboratory testbed for the didactic purpose. The exercises in laboratory GEPON network are proposed in section IV. Section V presents performance tests results. Section VI concludes the paper.

II.GEPON ARCHITECTURE STANDARDIZATION

There are two major organizations involved in PON standardization: Institute of Electrical and Electronics Engineers (IEEE) and Telecommunication Standardization Sector of the International Telecommunication Union (ITU-T). Both organizations publish standards dedicated to PON. This section is a brief description of evolutionary of PON toward GEPON.

First recommendations concerned with Access Network (AN) are presented in [1], [2], [3]. The recommendations define basic elements of PON. The reference configuration shown in Fig. 1 includes AF (block of Adaptation Function), ONU (Optical Network Unit), ODN (Optical Distribution Network), OLT (Optical Line Termination), references points, management interface (Q3).

The AF block is responsible for providing DSL transmission over copper to the end user. ODN consists of only passive elements splitters, connectors and fiber optics.

The ONU acts as an optical interface on the ODN side and implements the UNI interfaces at the end user side. The OLT is defined by core shell, common shell and service shell functions. The core shell functions include digital cross connects functions, transmission multiplex function, ODN interface function. The common shell is responsible for power supply and Operation and Maintenance (OAM) function. Due to service shell OLT is able to support two or more different services. The conception of PON architecture refers to all

Design and Implementation of GEPON

Architecture in Laboratory Testbed

Magdalena Młynarczuk, Lech Smoleński

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PON solution presented in Fig 2.

The first PON solution is All Passive Optical Network (APON). The APON has appeared in the conception of Full Service Access Network (FSAN) as a PON-based network that uses asynchronous transfer mode (ATM) [1].

The extended functionally of APON offers Broadband Passive Optical Network (BPON) architecture. Apart from APON, BPON [3] offers higher symmetric transmission speed, up to 622Mb/s downlink and uplink.

The EPON (Ethernet Passive Optical Network) is an optical network, able to carry on data encapsulated in Ethernet frames. The EPON standard has been introduced in the 802.3ah document. The basic configuration of EPON is defined in the [4]. In downstream direction Ethernet frames converted to optical form are transmitted by the OLT, pass through a 1:N splitters until reach ONU. ODN splitting ratio is typically from 4 to 64. In upstream direction data frames from all ONUs are transmitted through ODN towards OLT. Communication with another ONU is possible only via OLT switch.

GEPON supports 1 Gbit/s symmetric data rate. Apart from GEPON, 10G-EPON [5] offers EPON both symmetric 10Gbit/s downstream and upstream, and asymmetric 10Gbit/s downstream and 1Gbit/s upstream data rates [6].

The Gigabit Passive Optical Network (GPON) recommended in [7] also support Gigabit speeds but GPON

has a downstream capacity of 2.488 Gb/s and an upstream capacity of 1.244 Gbp/s that is shared among users. Encryption is used to keep each user's data secured and private.

Apart from GEPON the management of GPON is solved by using of new separate channel, where the GEPON management uses SNMP protocol.

Although there are other technologies that could supply fiber to the home, passive optical networks (PONs) like GPON and GEPON are generally considered the strongest candidate for widespread deployments. The rest of the paper is devoted to GEPON implementation, which is used in the laboratory.

III. GEPON LABORATORY TESTBEDAND ITS FUNCTIONALITY

The network topology was implemented in accordance with the principles of GEPON recommendations for ODN. Its architecture is presented in Fig. 3. GEPON architecture was implemented in purpose to familiarize students with GEPON solutions. The architecture consists of: OLT, five ONU, ODN, two PC computers, WWW/FTP + Video server (see Fig. 3).

The OLT is based on Raisecom GEPON (ISCOM5504) [8]. The OLT provides a single PON optical interface (1 of 4) for communicated with ONU_1- ONU_5.

For management purpose the OLT module is additionally equipped with out-of band management Ethernet port and console port serial interface (RS-232). All of the commands, including remote ONU management’s configuration commands are carried out at the OLT configuration side in encryption mode.

The ODN is implemented according to optical access network requirements. The ODN is built with two levels of splitters and attenuators for modeling fiber optics power loss.

The ONU is represented by Raisecom ISCOM5101 [9], which is stand-alone ONU device with one EPON interface, one Ethernet interface and one console interface. All devices are placed in GEPON architecture in laboratory testbed, implemented as point-to-multipoint (P2MP) access network (see Fig. 3). During labs ODN can be easily reconfigured into point-to-point (P2P) configuration. Due to limited number of PON interfaces in P2P configuration only four ONU can be installed (see Fig. 4).

Apart from basic functionality GEPON architecture could be implemented in cooperation with xDSL (one of FITL topology) and METRO access network, as it presents Fig. 5.

The GEPON laboratory testbed presented in Fig. 5 enables students to examine broadband services realization for various types of FITL access network solutions as Asymetric Digital Subscriber Line (ADSL) as well as Very high speed Digital Subsriber Line (VDSL) for the “first mile” distance.

Adittionaly the testbed presented in Fig. 5 can integrate GEPON network with METRO DWDM network. Such cooperation requires additional equipment between servers and GEPON OLT, such as devices for Carrier Ethernet 2

Fig. 1. Reference configuration for the PON [1].

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service demarcation, extension and aggregation (in Fig. 5 depicted as GbE/Opt) with optical links. to optical add/drop multiplexers and GEPON OLT.

IV. EXERCISESIN LABORATORY GEPON NETWORK

In general student can act in this laboratory as user of broadband services or as network OAM operator. This section focuses on presentation exemplary exercises performed by students during labs.

First of the GEPON laboratory functions is presentation of optical access for broadband services as video distribution. There are fixed parameters configured in SLA (for example FIR, CIR, PIR). For this item main observations are subjective video quality evaluation and in addition passive

monitoring of downstream transmission parameters.

More advanced version of GEPON functionality testing is interactive choice of GEPON transmission parameters on the basis of video service quality with optimization of system resources usage. Because of need for OLT management access this possibility is limited to only one student team and can disturb another active links in GEPON.

The most advanced GEPON configuration case is usage of VPN and QoS managing with data streams for different CoS. The application of QoS can deal with certain kind of data priority or adopts specifically management schedule strategy to make the network performance predictable and the management of bandwidth more efficient. QoS of ONU has three parts to implement: classification, tag and queue 3 8 7 6 5 T T T T T T T T T T T T _ ( ) / + _ 8 8 4 M _1 _2 _3 _4 _5 8 7 6 5 _ ( ) / + _ M T _{_1} T _{_2} T _{_3} T _{_4} 8 7 6 5 _ ( ) / + _ M _1 _2 _3 -C 2 -R -R _ _2 / / / +

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> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < scheduling. The OLT model supports remark functions based

on port ID, MAC address, VLAN, IEEE 802.1 priority, DiffServ and IP ToS. The students as users have an opportunity to compare service quality in different network conditions and topologies limitations.

Another topic for practice is GEPON network Operation, Administration and Maintenance (OAM). One of main function is remote fault indication. With maintenance port is possible to get actual parameters and statistics for OLT and ONU interfaces (optical and Ethernet) and also data transmission volume and quality information. Another OAM function is link loopback test which evaluates the quality and performance of link.

Apart from functional and performance testing students have an opportunity for plug and play testing. Manual configuration from P2MP to P2P is very crucial in aspect of practical knowledge.

V. PERFORMANCETESTS RESULTS EXAMPLES

This section presents some examples of laboratory tests results from OAM terminal in command line interface mode. These examples present typical answers for EPON global configuration mode (fttx).

Fig. 6 presents informations for ODN, such as distances and signal delay and ONU activity.

Raisecom(fttx)#show interface onu 0/5/1-4 online-information Distance

ONU ID State LLID RTT(TQ) (m) Login Date ---0/5/1 online 5 54 12 2012-10-01,08:00 0/5/2 online 1 50 6 2012-10-01,08:00 0/5/3 online 3 48 3 2012-10-01,08:00 0/5/4 online 4 54 12 2012-10-01,08:00

Fig. 6 Round trip time and distance information for online ONUs

Fig.7 is an example of service level agreement for uplink, without priority differentiation.

Raisecom(fttx)#show interface onu 0/5/1 sla FIR: Fixed information rate

CIR: Commited information rate PIR: Peak information rate

ONU ID FIR (Kbps) CIR(Kbps) PIR(Kbps) Priority ---0/5/1 0 64 30720 0

Fig. 7 Service level agreement configuration parameters for ONU_1

Fig. 8 shows policing configuration in both directions for ONU_1 Ethernet port from Fig. 3 network topology.

Raisecom(fttx)#show interface onu 0/5/1 uni ethernet policing Port ID: 0/5/1/1

Ingress policing : disable Ingress policing CIR: 4836 Kbps Ingress policing CBS: 4194304 Bytes Ingress policing EBS: 1514 Bytes Egress policing : disable Egress policing CIR : 4836 Kbps Egress policing PIR : 64022 Kbps

Fig. 8 Policy configuration of ONU_1.

PON statistic information query for ONU_1 performance is presented on Fig. 9. This command presents performance statistics for receive/send (in/out) single cast, multicast and broadcast package as well as receive/send (in/out) bytes of good packets, errors, discards.

Raisecom(fttx)#show interface onu 0/5/1 pon statistic ONU ID: 0/5/1 InUnicast : 33,994 InMulticasts : 11,217,440 InBroadcasts : 16 InGoodOctets : 2,221,358,768 InGoods : 11,251,450 InErrors : 0 InDiscards : 0 OutUnicast : 18,676 OutMuliticasts: 11,103,726 OutBroadcasts : 356 OutGoodOctets : 824,298,252 OutGoods : 11,122,758 OutErrors : 0 OutDiscards : 0

Fig. 9 Performance statistic information of ONU_1.

Fig. 10 is an example result of byte and frame error monitoring for uplink data transmission.

Raisecom(fttx)#show interface onu 0/5/1 statistics link-quality

US : upstream FER : frame error rate

US Errored US BER US Errored US FER ONU ID Bytes in 1e-9 Frames in 1e-9 ---0/5/1 0 0 0 0

Fig. 10 Uplink quality statistic for ONU_1

VI. CONCLUSION

In the paper GEPON architecture in laboratory testbed is presented. The possibility of GEPON network testbed development toward cooperation with xDSL systems and METRO network is presented. The propositions for students’ labs are presented. Exemplary results are also included.

The presented didactics laboratory GEPON architecture is a valuable illustration of practical GEPON realization. It is complementary to the theoretical view on optical access networks. It enables students to get familiarized with GEPON conception and its typical applications, it gives an opportunity to configuration, broadband services testing, and practice OAM functions.

REFERENCES

[1] ITU-T Recommendation G.982, Optical access networks to support

services up to the ISDN primary rate or equivalent bit rates, November

1996.

[2] ITU-T Recommendation G.983.1, Broadband optical access systems

based on Passive Optical Networks (PON), January 2005

[3] ITU-T Recommendation G.983.3, A broadband optical access system

with increased service capability by wavelength allocation, March 2001

[4] http://standards.ieee.org/findstds/standard/802.3ah-2004.html

[5] K. Tanaka, A. Agata, Y. Horiuchi, IEEE 802.3av 10G-EPON

Standardization and Its Research and Development Status, Journal of

Lightwave Technology, vol. 28, February 2010, pp.651-661.

[6] Z..A. Manaf, K. Khairi,, R. Mohamad, Z . Lambak, D. Adriyanto, D. Tarsono, .The challenge for active and passive components design in

CWDM PON system co-exist in GEPON and 10 GEPON architecture,

Photonics ICP, Conference Publication IEEE, 17-19 October 201.

[7] ITU-T Recommendation G.984.1, Gigabit-capable passive optical networks (GPON), General statistics, March 2008.

[8] EPON Configuration Guide, www.raisecom.com

[9] EPON Configuration Guide, Remote ONU Device Management www.raisecom.com