Next Generation OTN Transport Solution

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Next Generation OTN Transport Solution

Tel:+44 (0)1242 530630 Fax: +44 (0) 1242 530660 E-Mail [email protected] www.horsebridge.netHorsebridge Network Systems Ltd, 1 Pate Court, North Place, Cheltenham, GL50 4DY England.


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Next Generation OTN Transport Solution

White Paper

December, 2008

Copyright by ECI Telecom, 2008. All rights reserved worldwide.

The information contained in the documentation and/or disk is proprietary and is subject to all relevant copyright, patent, and other lawsprotecting intellectual property, as well as any specific agreement protecting ECI Telecom's rights in the aforesaid information. Neitherthis document nor the information contained in the documentation and/or disk may be published, reproduced, copied, modified ordisclosed to third parties, in whole or in part, without the express prior written permission of ECI Telecom. In addition, any use of thisdocument, the documentation and/or the disk, or the information contained therein for any purposes other than those for which it wasdisclosed, is strictly forbidden. ALL RIGHTS NOT EXPRESSLY GRANTED ARE RESERVED BY ECI TELECOM.

Any representation(s) in the documentation and/or disk concerning performance of ECI Telecom product(s) are for informationalpurposes only and are not warranties of product performance or otherwise, either express or implied. ECI Telecom's standard limitedwarranty, stated in its sales contract or order confirmation form, is the only warranty offered by ECI Telecom.

The documentation and/or disk is provided AS IS and may contain flaws, omissions, or typesetting errors. No warranty isgranted nor liability assumed in relation thereto, unless specifically undertaken in ECI Telecom's sales contract or orderconfirmation. Information contained in the documentation and in the disk is periodically updated, and changes will beincorporated in subsequent editions. If you have encountered an error, please notify ECI Telecom. All specifications aresubject to change without prior notice.


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CONTENTS

ECI Telecom Ltd. Proprietary iii

Contents

Introduction......................................................................................................................5Optical Transport Networks........................................................................................... 6OTN Hierarchy ................................................................................................................. 7Main Advantages.............................................................................................................9

Better Switching Scalability................................................................................... 9Transparent Transport of Client Signals ........................................................... 10Enhanced FEC Mechanism .................................................................................10More TCM Levels...................................................................................................11OAM&P Capabilities .............................................................................................12

ECI's Total OTN Solution.............................................................................................. 13End-to-End OTN Solution ....................................................................................13Delivery over a Single Platform........................................................................... 14Transparent Transport of Client Signals ........................................................... 15Unique 10G LAN Transmission Solution........................................................... 16Powerful ROADM Metro Solution .......................................................................17FEC Types..............................................................................................................18

Summary ........................................................................................................................19Abbreviations.................................................................................................................20About ECI Telecom .......................................................................................................21


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CONTENTS

iv ECI Telecom Ltd. Proprietary

List of Figures

Figure 1: OTN hierarchy.................................................................................................... 8

Figure 2: OTN network domains and layers..................................................................8Figure 3: ODU multiplexing concept...............................................................................10Figure 4: TCM in OTN network.......................................................................................11Figure 5: OTH unified service layer for lambda and sublambda services.....................14Figure 6: XDM transmission layer and technologies......................................................15Figure 7: OTN transparency for SONET/SDH services.................................................16Figure 8: 10G LAN PHY over OTN.................................................................................17Figure 9: Advanced ROADM metro solution..................................................................18


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INTRODUCTION

ECI Telecom Ltd. Proprietary 5

Introduction

For several decades, traditional PTTs essentially dominated the

telecommunications environment. Telephone service was the main offering andrevenue generator. Eventually, business leased line service and high speed Internet

started to take their share. Cable TV operators and Multimedia Service Operators

(MSOs) also entered the telecommunication carrier arena, developing networks

that originally provided only TV and video services to households. Cellular

operators evolved as well, from pure voice services to video and Internet services

over mobile phones, as well as business connectivity to the Enterprise market.

Deregulation in the telecom market and competition between incumbent and

competitive carriers have pushed both cable television and telecommunication

operators to provide triple play services (telephone service, high speed Internet,

VoD, and broadcast TV). The premise was that bundled services would increase

business opportunity while offering attractive prices to the end-customer. Theoperators have been focusing on the triple play business aspects rather than on

technical issues.

The support of triple play and advanced services requires network migration. This

includes migration from 64 Kbps and 2 Mbps to broadband access technologies,

from circuit switched voice to VoIP, Enterprise marked migration towards

Ethernet-based services, and the support of the increasing number of storage

systems deployed in medium and large businesses.

The common hurdles for migration are the support of an increased amount of

packet-based services/applications and high-capacity transport pipes. The existing

SDH/SONET transport network does not provide the optimized solution for both

issues. SDH/SONET was developed to support low-order services at E1/DS-1rates, and high-order services at VC-3/STS-1 and VC-4/STS-3c rates. It was not

optimized to handle pipes with a capacity beyond 150 Mbps (for example 1, 2.5,

and 10 Gbps services).

A new transport technology is required to provide a converged transport solution

for TDM and packet-based services. The Optical Transport Network (OTN)

technology introduces such a solution, while offering flexibility for new services.


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OPTICAL TRANSPORT NETWORKS

6 ECI Telecom Ltd. Proprietary

Optical Transport Networks

The Optical Transport Hierarchy, OTH, is a new transport technology developed

by the ITU for utilizing the experience and benefits of SONET/SDH and DWDMtechnologies. It enables the transfer of client signals (packet-based and legacy

TDM services) over multiservice transport networks. It has all the capabilities to

monitor, manage, and control each particular wavelength in the network.

OTN is specified in several ITU standards.

Architecture is defined in ITU T G.872 - the Architecture of Optical Transport

Networks.

Interfaces and framing are defined in ITU T G.709 - Interfaces for the OTN

and ITU T G.959.1 - OTN physical layer interfaces.

Equipment function is defined in ITU T G.798 - Characteristics of optical

transport network hierarchy equipment functional blocks, ITU T G.873.1 -OTN: Linear Protection and ITU G.8251 - the control of jitter and wander

within the OTN.

Network management is defined in ITU G.874 - Management aspects of the

optical transport network element, ITU G.874.1 - OTN protocol neutral

management information model for the network element view and ITU G.875 -

OTN management information model for the network element view.


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OTN HIERARCHY


OTN Hierarchy

OTH is also known as a "digital wrapper" because of its ability to enclose any

service in digital optical containers. It has hierarchical layers, similar toSDH/SONET. The OTN is composed of OTH and the optical layers (OMS, OTS)

with the addition of a supervisory channel for management purposes.

The OTH layers are as follows:

The OPU (Optical Payload Unit) maps (encapsulates, digitally wrapping) the

Client signal (e.g. SONET/SDH, IP-packets, ATM cells, Ethernet frames) and

performs rate justification, if needed.

The ODU (Optical Channel Data Unit) consists of the OPU and the ODU

overhead. The ODU overhead functionality is similar to the path overhead in

SONET/SDH. It provides multiplexing, protection switching, end-to-end path

supervision, tandem connection monitoring, BIP for signal quality supervision,

maintenance signals, and data communication channels.

The OTU (Optical Channel Transport Unit) is the highest layer in the electrical

domain. Its functionality is similar to the Section Overhead in SONET/SDH

and includes BIP calculation, Trail Trace ID, and Forward Error Correction

(FEC).

The OCh (Optical Channel) performs electrical to optical signal conversion

and modulates the DWDM wavelength (ITU-T grid) carrier.

The OMS (Optical Multiplex Section) multiplexes several wavelengths, each

carrying one OCh into one fiber. The OMS layer refers to the section between

an optical multiplexer and demultiplexer.

The OTS (Optical Transmission Section) exists between each of the in-line

optical amplifier units.


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OTN HIERARCHY


Figure 1: OTN hierarchy

The OTN defines two interfaces:

Inter domain interface (IrDI) the interface between different operatordomains or between different vendors in the same operator domain.

Intra domain interface (IaDI) the interface between a single vendor's network

equipment in a single operator domain.

Figure 2: OTN network domains and layers


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MAIN ADVANTAGES


Main Advantages

OTN offers several advantages over SONET/SDH.

Better Switching Scalability

Over time, the new IP based service rates have increased while the SONET/SDH

switching rates remained fixed at VC-12/VT-1.5 to VC-4/STS-1 granularity. The

gap between the new services and switching bitrate has grown. Contiguous and

virtual concatenation functionality has been introduced to enable transmitting new

services, requiring a higher switching rate, over the SONET/SDH network.

Support of 10 GbE services, for example, requires virtual concatenation to 64

VC-4s/STS-3c in order to transmit them through the network. This method is very

complicated to process within the NEs, not to speak of management and operation.

Another transmission method for these signals would be directly over wavelength,but this cannot provide a flexible switching rate and wastes network bandwidth.

For example, a network that uses 10G DWDM wavelength channels will waste

75% or 90% of the bandwidth when transmitting 2.5G or 1GbE services,

respectively. On the other hand, a network that uses 2.5G wavelength DWDM

channels cannot support 10 GbE services without upgrading the relevant

wavelengths to 10 GbE, which is expensive and inefficient.

OTH was introduced in order to overcome these problems. It defines new entities

(similar to virtual containers, VCs/VTs, in SDH/SONET), which provide end to

end containers and switching rates. OTH defines three switching rates:

ODU 1, ~2.50 Gbps

ODU 2, ~10.00 Gbps

ODU 3, ~40 Gbps

The corresponding Optical Channel Transport Unit (OTU) bitrates are:

OTU 1, ~2.67 Gbps

OTU 2, ~10.71 Gbps

OTU 3, ~43.02 Gbps

The OTN multiplexing function is similar to PDH. Four ODU 1 signals are

multiplexed into ODU 2, and four ODU 2 signals are multiplexed into ODU 3

(additional combinations are supported as well).


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MAIN ADVANTAGES


Figure 3: ODU multiplexing concept

Transparent Transport of Client Signals

SDH/SONET signals are mapped directly into OTN, while data traffic is mapped

to OTN using Generic Framing Procedure (GFP). Client signals may be

PDU-oriented (e.g. IP/PPP or Ethernet MAC) or block code oriented constant

bitrate streams, such as ESCON, FICON, or Fiber Channel (FC). PDU-oriented

signals are mapped to ODU using frame-mapped GFP (GFP-F). Block codeoriented signals, which require very low latency, are mapped to ODU using

transparent GFP (GFP-T).

One of the important benefits of this feature is that OTN can transmit SDH/SONET

services via the OTN network, without terminating the signal in each NE.

SDH/SONET service transmission is entirely transparent (including the clock and

overhead bytes). This capability is important for the customer in Carrier of Carriers

(CoCs) applications where the client signal must be transmitted as a fully

transparent service. For example, an STM-16/OC-48 signal will be transmitted

transparently from one NE to another through the CoC network, maintaining the

original clock of the NEs.

Enhanced FEC Mechanism

SDH/SONET already has Forward Error Correction (FEC) capability, but uses

undefined SOH bytes to transmit the FEC information, limiting capability and

performance.

OTH, however, uses a Reed-Solomon algorithm (RS255239), which adds 7%

overhead on the line rate. This improves Signal to Noise Ratio (SNR) by 5 dB to 6

dB. The result is an increased maximum span length, saving 3R regeneration sites

and enabling more OADM nodes deployed along the signal path without 3R

regeneration. This makes it more efficient to evolve from point-to-point and mesh

to OADM and ROADM topologies.


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MAIN ADVANTAGES


More TCM Levels

OTH supports six levels of independent Tandem Connection Monitoring (TCM),

allowing nested and cascaded domain monitoring. This capability permits parallel

monitoring for a path transmitted over multiple administrative domains/carriers anddifferent segments of the path. In contrast, SDH/SONET only allows cascaded

monitoring (one level).

Figure 4: TCM in OTN network


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MAIN ADVANTAGES


OAM&P Capabilities

The OTH provides Operation, Administration, Maintenance, and Provisioning

(OAM&P) functionality. It adapts many capabilities that have been developed for

the SDH/SONET technology and expands it for the OTH electrical layers.

Several protection schemes are available; OCh 1+1, OCh-SPRING, ODU-1+1

linear, ODU-SNC/I, ODU-SNC/N, ODU-SNC/S, and ODU-SPRING.

A mesh restoration and recovery mechanism can also be used, based on ASTN

(Automatically Switched Transport Network) standards.

The maintenance capabilities are available at both the electrical and the optical

levels. The OTN enables monitoring of the full ODU path or any section in the

network, providing advanced capabilities to monitor, troubleshoot, and isolate any

fault in the network. This includes:

Tandem Connection Monitoring (TCM), discussed previously

The Trail Trace Identifier (TTI) at OTU and ODU levels, providing

functionality similar to J0 and J1 in SDH/SONET

Bit Interleaved Parity (BIP-8), used for error detection

Backward Detect Indication (BDI), which provides information on failure in

the upstream direction

Status bits for indication of the maintenance signal (STAT)

Others

The management information can be transmitted inband over General

Communications Channel (GCC) bytes or over the Optical Supervisory Channel

(OSC).

The GCC0 resembles the DCC (Data Communications Channel) from

SONET/SDH. It can also be used to transmit the signaling of the control plane.

The OSC is used mainly to manage optical in-line amplifiers and can also carry

overhead information of associated OCh, OMS, and OTS signals.


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ECI'S TOTAL OTN SOLUTION


ECI's Total OTN Solution

XDM

platforms feature an all-range architecture that supports metro, regional,

and long-haul applications in a single platform. The XDM provides a complete andflexible optical solution, powered by cutting-edge Wavelength Selective Switch

(WSS) ROADMs, tunable lasers, and modular card design, with easy installation

and automatic operation.

The XDM is the only truly converged platform that combines SDH/SONET, data

(ATM, Ethernet, and MPLS), and C/DWDM functionality in a single shelf. ECI

Telecom is an innovator of true platform convergence. The XDM is the first system

that can add/drop an E1 to/from a lambda in a single shelf, and the only system to

provide top-of-the-line seamless performance for all converged platform elements.

Based on network requirements, the XDM can be equipped with a variety of

C/DWDM cards and modules. This wide range of optical elements enables the

implementation of efficient, high-performance, low-cost networks for virtuallyevery telecommunication need.

XDM provides the flexibility that service providers seek for migration to next

generation OTN-based networks, managed end-to-end via a unified carrier-class

management system.

End-to-End OTN Solution

OTN transponders and combiners are available in the entire XDM product line,

starting from the XDM-40 and all the way up to the XDM-1000 and XDM-2000.

This provides a full end-to-end OTN solution, from the CPE and metro-access, up

to regional and long-haul core. It is specifically designed to address the growingdemand for both triple play service delivery and broadband business data transport.

This gives service providers the flexibility to take full advantage of their existing

networks while providing a smooth and fully supported migration to IP over

Optics, at the same time significantly reducing transport costs.

The solution is managed end-to-end from the optical layer via ECI's LightSoft

network management system, enabling service providers to easily manage and

provision new services using advanced GMPLS capabilities.


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Figure 5: OTH unified service layer for lambda and sublambda services

Delivery over a Single Platform

The unique XDM architecture allows XDM to support all service types over a

single platform. Cellular backhauling, triple play and business services, as well asCoC services are handled in their native environments and locations in the

network.

TDM and SDH/SONET services are handled in the SDH/SONET matrix, while

data services are groomed at L1 and L2 on a variety of data cards (ATM, Ethernet,

and MPLS) each in its native environment. All services are transmitted to the

optical layer via OTN mapping, acquiring the advantages of this technology as

described in the previous section.

The entire XDM product line uses the same optical OTN universal modular service

card. This unique card enables in-field configuration to support any service, at both

the line and client sides, rendering the XDM easy to deploy, operate, and maintain.

Combined with ECIs unique compact full C-band tunable lasers for 2.5 G and 10G wavelengths, the XDM also offers unrivaled savings in spare parts.


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Figure 6: XDM transmission l ayer and technologies

Transparent Transport of Client Signals

In the current telecommunications marketplace where infrastructure is costly, many

customers prefer to lease services via CoCs rather than build their own. They

demand much more than simple, rigid, point-to-point services. They require

multiple services, bitrates, and protocols in their POPs, as well as convergence of

all services over a single leased transmission pipe. In addition, major customersseeking higher quality services are shifting from monitored leased lines, which

cannot be managed directly, to fully managed Customer Managed Networks

(CMNs) and VPNs.

CoCs lease services over their transmission infrastructure to a variety of operators,

such as ISPs, Inter-Exchange Carriers (IXCs), and cellular operators. Since each

type of operator requires different services, the CoC must support a variety of

leasing options.

XDM supports all leasing options starting from E1 to SDH/SONET, Ethernet

connectivity, and wavelength. XDM can also provide transparent SDH/SONET

connectivity, including the timing clock and overhead bytes. For example, four

different SDH/SONET signals can be multiplexed to the same 10G wave withoutdamaging any of the four timing clock sources, thanks to ODU-1 mapping and

multiplexing capability.

Managed by the innovative LightSoft network management system, the XDM

enables CoCs to offer CMN services with transmission resources. This includes

virtual topology views and service provisioning. CMN clients have complete

visibility of their networks and can monitor, control, and maintain them, or change

connectivity as needed, responding in real time to frequently changing needs and

requirements.


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Figure 7: OTN transparency f or SONET/SDH services

Unique 10G LAN Transmission Solution

10G LAN transmission has become widely used for connecting core IP routers and

as a service for high-profile business customers. There are a number of ways to

carry 10G LAN signals over DWDM. The following are some of the most common

methods:

Direct coloring of the 10G LAN signal (with no additional mapping or

framing). This solution is not OTN-compliant and has no server layer

whatsoever. Hence, the 10G LAN service cannot be monitored by the

transmission layer. Moreover, since FEC is not added, this solution is verylimited in reach.

Overclocking the 10G LAN client to an 11.1 Gbps line with 7% FEC. In this

solution, the addition of FEC increases the reach, and proprietary PM is

feasible. However, this is not an OTN-compliant solution and the operator

cannot benefit from standard ODU-2/OTU-2 PM. In addition, such services

cannot be regenerated by standard OTU-2 regenerators, thereby forcing the use

of proprietary 11.1 Gbps regenerators as well when required. Although there

have been attempts to standardize a new type of ODU-2 container, called

ODU-2**, to accommodate 10G LAN services, this has not materialized and

may not emerge in the foreseeable future.

Mapping 10G LAN to ODU-2 using rate adaptation. In this method the rate

gap between 10G LAN and ODU-2 is bridged by mapping the excess preamble

and SFD bytes in the Ethernet frame into interpacket gaps in the Ethernet

payload. Using this method, the operator enjoys standard ODU-2/OTU-2 PM.

However, there is a compromise in the Ethernet service which is not

transparent, and not all throughputs or frame formats are supported.

The ECI solution overcomes the problems described in the options above. It is

based on GFP-F mapping of the 10G LAN payload to standard ODU-2 containers,

while translating the excess preamble and SFD bytes onto unused bytes in the

OPU2 frame, as shown in the diagram below.


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The 10G LAN is transported transparently at full rate in all frame formats

(including jumbo frames and 0% IPG). On the line side, the operator enjoys fully

standard ODU-2/OTU-2 for PM, interoperability, and the like. If regeneration is

required, a standard OTU-2 regenerator is used.

Figur e 8: 10G LAN PHY over OTN

Powerful ROADM Metro Solution

In heavy traffic networks, C/DWDM-based optical infrastructure must be built

from day one to provide connectivity for triple play. The same optical

infrastructure provides connectivity to business customers and to other wholesale

clients. It is expected that the optical network will have the same flexibility and

manageability as SDH/SONET-based networks. The XDM's ROADM capabilities,

together with the OTN technology, offer service providers greater flexibility by

providing any wavelength to any node connectivity ("any-to-any") without the

need to predefine traffic demands.

XDM incorporates the most advanced ROADM, based on Wavelength Selective

Switch (WSS) technology, which provides solutions for various topologies. A new

range of high-power optical amplifiers optimized for ROADM sites completes the

offering, and positions the XDM as an unbeatable solution for flexible all-range

OTN networks.

It provides:

Colorless operation - any channel to any port

Full n-degree operation for multiple ring, subtended ring, star, and full mesh

topologies

Low insertion loss for through channels


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Figure 9: Advanced ROADM metro solution

FEC Types

For better performance, XDM transponders also support 7% out-of-band FEC,

based on the following operation modes:

Encode only in the transmit transponder

Decode only in the receive transponder

Decode and encode - when the transponder acts as a regenerator

Encoding and decoding disabled - FEC is not required

The XDM also supports Enhanced Forward Error Correction (EFEC). EFEC

function has greater correction capability than the G.709 RS (255239) code.

Standard FEC provides a coding gain of 5 dB to 6 dB, while G.975 I4 EFEC/Super

FEC provides a coding gain of 8 dB to 9 dB.


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SUMMARY


Summary

In today's dynamic telecom environment, where bandwidth demand is rapidly on

the rise for all types of applications, service providers are looking for a transporttechnology that can provide smooth migration to the next generation network.

OTN has proven to be the technology that supports legacy as well as new advanced

services, while retaining the benefits and capabilities of SDH/SONET and DWDM

technologies.

The XDM family includes a variety of NEs to accommodate the needs of the

different network layers. Products range from small units at the edge of the

network to large MSPPs/MSTPs at the network core. The operator can use the

XDM product line in the different network layers, with the added advantage of a

single management system for end-to-end management.

The entire XDM line is designed to support smooth migration for next generation

networks with a variety of OTN plug-in cards for introducing new services and

functionality.

XDM's next generation WDM offers:

Single All-Range WDM system, covering Access to Regional/LH

Full suite of G.709 OTN features for advanced PM, interoperability, unified

lambda/sublambda management, and transparency

Integration of CWDM and DWDM

Proven converged technologies: SDH/SONET, L1/L2 switching, and optical

capabilities all in a single system

Flexible and modular solution using ROADM and tunable lasers

Ready for future 40G lambdas


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ABBREVIATIONS


Abbreviations

CMN Customer Managed Network

CoC Carrier of Carrier

DCC Data Communication Channel

FEC Forward Error Correction

GCC General Communication Channel

GFP Generic Framing Procedure

IaDI Intra-Domain Interface

IrDI Inter-Domain Interface

ISP Internet Service Provider

MSO - Multimedia Service OperatorsMSPP Multi Service Provisioning Platform

MSTP multi Service Transport Platform

OCh Optical Channel

ODU Optical data Channel Unit

OMS Optical Multiplex Section

OPU Optical Payload Unit

OSC Optical Supervisory Channel

OTH optical Transport Hierarchy

OTN Optical Transport Networks

OTS Optical Transmission Section

OTU Optical channel Transport Unit

ROADM Reconfigurable Optical Add/Drop Multiplexer

SNR Signal to Noise Ratio

VoD Video on Demand

VoIP Voice over IP

WSS Wavelength Selective Switch


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ABOUT ECI TELECOM


About ECI Telecom

ECI Telecom is a leading global provider of intelligent infrastructure, offering

platforms and solutions tailored to meet the escalating demands of tomorrow'sservices. Our comprehensive 1N approach defines ECIs total focus on optimal

transition to Next-Generation Networks, through the unique combination of

innovative and multi-functional network equipment, fully integrated solutions and

all-around services.

For more information, please visit http://www.ecitele.com.
http://www.ecitele.com/http://www.ecitele.com/


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1Net defines ECIs total focus on facilitating our customers' optimal transition

to Next-Generation Networks, through the unique combination of innovative and

multi-functional network equipment, fully integrated solutions and all-around services

Documents

Next Generation OTN Transport Solution