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Comput er I nst i t ut e Kazaure, Jigawa State, Nigeria Comput put er Net wor k and I nt er net net ( CNW201) 01) Pr oj ect Docum cument at i on ON

Synchronous Optical Network (SONET)

By

 Yu  Yusif Suleiman 2308-0703-0223

Supervis visor/lecturer:

Mr. Nu Nura Tij Tijjani Abubakar Date: 20th June, 2012 i

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CERTIFICATION OF WORK

This is to certify that, the Computer Network and Internet project documentation titled: Synchronous Optical Network (SONET), is a personal work done originally by Yusif  Suleiman in the process of obtaining International Advance Diploma Certificate in Computer and Cyber Security, at Informatics Institute Kazaure (JSIIT), Jigawa State,  Nigeria.

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ACKNOWLEDGEMENT All Praise be to Allah, the exalted and the most highly Gracious, lord of the world the  beneficent, the t he merciful, blessings of Allah upon his Prophet Muhammad (SAW). I want to use this medium to thank my Parents, entire family, friends, relatives and well wishers for support given throughout this course of study, my regard also to my lecturer/supervisor Mr. Nura Tijjani Abubakar to whom I received much guidance during accomplishment of this course, I also thanks all my colleagues of Informatics Institute Kazaure, and IT students around the globe.

 Yusif Suleim an 2308-0703-0223

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Table of Contents CONTENT

PAGES

Cover ……………………………………………… ………………………………………………………………………… …………………………………..i ………..i Certification of Work……………………… Work……………………………………………… ………………………………………….ii ………………….ii Acknowledgement…………………………………………………………………....iii Table of Contents……………………… Contents………………………….………………………… ….……………………………………….....iv …………….....iv List of Figures………………… Figures…………………………………………………… ………………………………………………………vi ……………………vi List of Diagram…………………………………………… Diagram……………………………………………………………………… …………………………..vi ..vi List of Tables……………………… Tables……………………………………………………… ………………………………………………….vi ………………….vi 1.0 Introduction…………………...………………… Introduction…………………...………………….……….…………………….…1 .……….…………………….…1 1.1 Objective………………..………………………………..………………………..2 1.1.1 High Transmission Transmiss ion rate…………………… rat e…………………………………………… …………………………………..5 …………..5 1.1.2 Simplified Add and Drop Function………………………….………………..5 Function………………………….………………..5 1.1.3 High Availability and Capacity Maching……………………..……………… Mac hing……………………..……………….6 .6 1.1.4 Reliability………………………………………………………..……………..6 1.1.5 Future-Proof Platform for New Services……………………………..………..7 Services……………………………..………..7 1.1.6 Interconnection………………………………………………….……………..8 1.2 The History…………………………………… History………………………………………………………………………..11 …………………………………..11 1.3 Current Technology…………… Technology…………………………………………… ……………………………………….…………13 ……….…………13 1.3.1 Asynchronous………………………………………………..……………….13 1.3.2 Synchronous…………………………………………………………………..14 1.3.3 Optical……………………………………………………….……………….14 1.4 Benefits of SONET…………………………… SONET……………………………………………… …………………………………17 ………………17 1.4.1 Advantages of o f SONET………………………………………………..……..20 SONET………………………………………………..……..20 1.4.2 Disadvantage of SONET………………………… SONET………………………………………………… ………………………….20 ….20 2.0 Application and Network Configurations………………….……………………21 2.1 Application Area…………………………………………………………………22 Area…………………………………………………………………22 2.2 SONET Network Topology…… To pology…………………………………..……………… ……………………………..………………….23 ….23 2.3 Network Architecture…………………………………………………………….25 Architecture…………………………………………………………….25 2.3.1 Liner Automatic Auto matic Protection Switching…………………………….…………...26 Switching…………………………….…………...26 2.3.2 Undirectional Path Switched Ring………………………….………………….27 Ring………………………….………………….27 2.3.3 Bidirectional Line Switched S witched Ring……………………………………………...28 Ring……………………………………………...28 3.0 Implementation……… Implementation……………………………… ……………………………………………… ……………………………………..30 ……………..30 iv

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3.1 Technical Contents………………………………………………………………..31 Contents………………………………………………………………..31 3.2 Cost and Benefit Bene fit Analysis…………………………………………………..…….34 Analysis…………………………………………………..…….34 3.3 Conclusion…………… Conclusion…………………………………………… ……………………………………………………… …………………………..38 …..38 4.0 References………………………………… References………………………………………………………………… ……………………………………...39 ……...39 5.0 Appendices.………………… Appendices.…………………………………………… ………………………………………………… ………………………….42 ….42 5.1 Appendix A: Acronyms…………… Acronyms…………………………………………… ……………………………………………...42 ……………...42 5.2 Appendix B: G lossary…………………………………………… lossary……………………………………………………………..49 ………………..49 5.3 Appendix C: Internet Addresses of Standard Bodies and Forums………………...66 5.4 Appendix D: Reco mmendation……………………………………… mmendation……………………………………………………66 ……………66

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List of Figures 1. Figure 1:

SONET Physical Network Connection……………….3 Connection……………….3

2. Figure 2:

Simplified Add/Drop Function………………………..5 Function………………………..5

3. Figure 3:

SONET Network HUB…………………… HUB………………………………..8 …………..8

4. Figure 4:

SONET Multiplex Hierarchy…………………………19 Hierarchy…………………………19

5. Figure 5:

Typical SONET Network Mgt Com Architecture……25

6. Figure 6:

Add/Drop Liner Configuration……………………….26 Configuration……………………….26

7. Figure 7:

Enterprise Application with USPR……………………27

8. Figure 8:

Enterprise Application with BLSR…….……………..28

List of Diagrams 1.

Diagram 1:

SONET Ring Network………………………… Network………………………………..7 ……..7

2. Diagram 2:

Dual Ring Interworking (DRI)………………… (DRI)………………………..9 ……..9

3. Diagram 3:

Multiservice SONET Network…………………… Network……………………….18 ….18

4. Diagram 4:

SONET Automatic Switching Ring Network………..23

5. Diagram 5:

Fundamental SONET Difference Service Delivery…..33

List of Table 1. Table 1:

SONET Signal Bit Rate & SDH Signal Equivalent……..2

2. Table 2:

Virtual Tributaries……………………………………….31 Tributaries……………………………………….31

3. Table 3:

SONET/SDH Hierarchies…………………...…………..32 Hierarchies…………………...…………..32

4. Table 4:

Market Revenue Forecast……………………………… Forecast……………………………….35 .35

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A. INTRODUCTION

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1.0 INTRODUCTION Before SONET, fiber optic systems in the public telephone network employed many different proprietary architectures, equipment, line codes, multiplexing formats, and  maintenance procedures. Users of fiber optic systems--including the Regional Bell Operating Companies and interchange carriers (IXCs) in the US, Canada, Korea, Taiwan and Hong Kong--needed a standard that would connect these proprietary systems' equipment to one another. In Europe, SONET is referred to as SDH (Synchronous Digital Hierarchy). The first level in the SDH (Synchronous Digital Hierarchy) is STM-1 (Synchronous Transport Mode 1) having a line data rate of 155 Mb/s approximately which is equivalent to SONET's STS-3c. The table below show the bits rates

Table 1.

SONET is the communication protocol, as well as the generic all-purpose transport container, for transmission of all types of digital data including voice, text, image and  video. Unlike a typical frame-oriented data transmission, like in the ethernet networks where the header of the frame, payload and trailer (CRC data) is transmitted in a sequence, SONET is the part of header and the payload is interleaved on transmission.

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As the population expanded and communication demands grew, copper--once the transmission material of choice--ceased to be economical or practical to carry the huge number of calls nationwide. Copper also was highly prone to electrical spikes from storms and other electrical interference. SONET was born out of necessity, now data that once required hundreds of copper cables could be directed down a glass fiber only slightly thicker than a human hair. Carriers jumped on this technology and tried to one-up each other in the amount of fiber each had. To keep up with carriers' needs, vendors created complex systems to multiplex traffic onto these tiny strands. The figure show how users connect using multiplexer to SONET ring network.

Figure 1

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Yusif Suleiman2308-0703-0223 OBJECTIVE

It took roughly 10 years for the transport network industry to migrate from PDH to SONET. As this technology swap comes to an end, WDM technology is dawning,  promising to revolutionize revo lutionize the network industry, with the possibility po ssibility of transport bit rates above 10 Gb/s as well as transparency to signal encodings. However, a new wave of  equipment upgrade is unlikely to happen as current SONET equipment is just beginning to pay off for its large investment. Thus, in years to come, SONET technology, the current standard for optical fiber access, will have to make room for WDM technology in a gradual way. On its part, WDM equipment must be developed to be backward  compatible with SONET technology. With some 800 million telephone connections in use today and the number of Internet users continuing to grow rapidly, network providers have been faced with the task of  trying to deal effectively with increased telephone and data traffic. In response to the ongoing growing market needs, a number of methods and technologies have been developed within the last 60 years to address these market needs. Towards the end of the 1980s, the synchronous optical network (SONET) was introduced, paving the way for a worldwide, unified network structure. SONET is ideal particularly for network providers, as it delivers an efficient, economical network management system that can be easily adapted to accommodate the demand for “bandwidth-hungry” applications and services. In response to the demand for increased bandwidth, reliability, and high-quality service, SONET developed steadily during the 1980s eliminating many of the disadvantages inherent in DSn. In turn, network providers began to benefit from the many technological and economic advantages this new technology introduced including:

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1.1.1 HIGH TRANSMISSION RATES

Transmission rates of up to 40 Gb/s can be achieved in modern SONET systems making it the most suitable technology for backbones – the superhighways in today’s telecommunications networks.

1.1.2 SIMPLIFIED ADD AND DROP FUNCTION

Compared to the older DSn system, low bit rate channels can be easily extracted from and inserted into the high-speed bit streams in SONET. It is now no longer necessary to apply the complex and costly procedure of demultiplexing then remultiplexing the  plesiochronous structure.

Figure 2.

A single-stage multiplexer/demultiplexer can multiplex various inputs into an OC–N signal. Figure show that an add/drop site, only those signals that need to be accessed are dropped or inserted. The remaining traffic continues through the network  element without requiring special pass-through units or other signal processing. In rural

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applications, an ADM can be deployed at a terminal site or any intermediate location for  consolidating traffic from widely separated locations. SONET enables drop and repeat (also known as drop and continue)—a key capability in both telephony and cable TV applications. With drop and repeat, a signal terminates at one node, is duplicated  (repeated), and is then sent to the next and subsequent nodes.

1.1.3 HIGH AVAILABILITY AND CAPACITY MATCHING

With SONET, network providers can react quickly and easily to the requirements of their  customers. For example, leased lines can be switched in a matter of minutes. The network   provider can use standardized network elements (NE) that can be controlled and  monitored from a central location via a telecommunications management network (TMN) system.

1.1.4 RELIABILITY

Modern SONET networks include various automatic back-up circuit and repair  mechanisms which are designed to cope with system faults and are monitored by management. As a result, failure of a link or an NE does not lead to failure of the entire network. Even if the optical fiber is cut, the transmission path is backed-up and restored  within 50ms. Diagram 1 shows an example of SONET ring network.

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Diagram 1. The SONET Rings

A SONET transmission network is composed of several pieces of equipment, including:



Terminal multiplexer (TM)



Add-drop multiplexer (ADM)



Repeater 



Digital cross-connect system (DCS)

1.1.5 FUTURE-PROOF PLATFORM FOR NEW SERVICES

SONET is the ideal platform for a wide range of services including POTS, ISDN, mobile radio, and data communications (LAN, WAN, etc.). It is also able to handle more recent services such as video on demand and digital video broadcasting via ATM. It also assume to accommodates unexpected growth and change more easily than simple point-to-point networks see figure3.

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Figure 3

The following are two possible implementations of this type of network: 

Using two or more ADMs, and a wideband cross-connect switch, which allows cross-connecting the tributary services at the tributary level



Using a broadband digital cross-connect switch, which allows cross connecting at  both the SONET level and the tributary level

1.1.6 INTERCONNECTION

SONET makes it much easier to set up gateways between different network providers and to SDH systems. The SONET interfaces are globally standardized, making it possible to combine NEs from different manufacturers into a single network thus reducing equipment costs.

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The trend in transport networks is toward ever-higher bit rates, such as OC-768 (time division multiplex, TDM). The current high costs of such NEs however are a restricting factor. The alternative lies in dense wavelength division multiplexing (DWDM), a technology enabling the multiple use of single-mode optical fibers. As a result, a number  of wavelengths can be used as carriers for the digital signals and transmitted  simultaneously through the fibers. The Dual Ring Interworking configuration allows multiple rings sharing t raffic to be resilient from a SONET multiplexer node failure. If a catastro phe takes out a SONET S ONET multiplexer system, traffic will be routed through the operational SONET multiplexer. The benefit to the user is that continuous network operation is maintained, and business continues as usual even though a failure has occurred. This is all transparent to the user. This type of configuration is typically t ypically deployed deployed in central office topologies. Diagram 2 illustrates a DRI configuration.

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Due to SONET's essential protocol neutrality and transport-oriented features, SONET was the obvious choice for transporting Asynchronous Transfer Mode (ATM) frames. It quickly evolved mapping structures and concatenated payload containers to transport ATM connections. In other words, for ATM (and eventually other protocols such as Ethernet), the internal complex structure previously used to transport circuit-oriented  connections was removed and replaced with a large and concatenated frame (such as OC3c) into which ATM cells, IP packets, or Ethernet frames are placed. p laced.

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Yusif Suleiman2308-0703-0223 THE HISTORY

Before the birth of Synchronous Optical Network (SONET), the transmission system widely deployed in the telecommunications industry was known as the Plesiochronous Digital Hierarchy (PDH). Plesiochronous means the timing of signals across the network  is almost but not precise, and there is not a centralized timing source since each node has its own clock. As more and more channels were multiplexed together into higher layers of the PDH hierarchy, each frame need to be completely demultiplexed in order to select an individual channel as the timing across all the nodes was not totally the same. Another   problem occurred where different networks with relatively wide differences in timing met, such as between Europe and the U.S. The SONET standard was designed in the mid  1980’s to alleviate these problems. It is more widely used in North America. The International Telecommunications Union later generalized SONET into the SDH in order  to accommodate the PDH rates in use outside North America, mainly deployed in Europe and Asia-Pacific Countries.

SONET/SDH standardized the line rates, coding schemes, bit-rate hierarchies, and  operations and maintenance functionality. SONET/SDH also defined the types of   Network Elements (NEs) required, network architectures that t hat vendors could implement, and the functionality that each node must perform. A typical SONET/SDH network  utilizes the Section Data Communications Channels (DCC). Briefly, one or more Operations Systems (OSs) manages the SONET/SDH NEs and the connectivity between them is achieved through a Data Communications Network (DCN). Open System Interface (OSI) was selected as the standard for SONET Section DCC because OSI

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 protocols were accepted as the basis for the larger set of Telecommunications Management Network (TMN) standards. Compared to OSI, the Simple Network  Management Protocol (SNMP) layers are much simpler. In SNMP, the network  management applications consist of vendor-specific modules such as fault management, log control, security and audit trails and they map the SNMP management traffic instead  of OSI headers into the DCC fields or the payload areas for onward transmission to the management process. Because of the simplicity and similarity of the SNMP network  management process, service providers have begun to request that SONET/SDH products support an IP protocol stack on their OS/NE interface (Ethernet), since many service  providers did not want to implement an OSI-based DCN or deploy mediation devices. G.7712 is the standard for Architecture and Specification of the Data Communications network (DCN). G.7712 is important for the telecommunication industry since it enables intelligent optical networks with combined IP-managed and OSI-managed equipment. It is also crucial for vendors of network edge devices as it allows for easy transport of  network management traffic to these devices via the core optical switches without the need to create expensive and complicated overlay networks.

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Yusif Suleiman2308-0703-0223 CURRENT TECHNOLOGY

In the early 1980s, a revolution in telecommunications networks was ignited by the use of  a relatively unassuming technology, fiber-optic cable. Since then, the consequential increase in network quality and tremendous cost savings have led to many advances in technologies required for optical networks. Many of these benefits have yet to be realized. The digital communications network has evolved through three fundamental stages: Asynchronous, Synchronous, and Optical.

1.3.1 ASYNCHRONOUS

Traditional digital telecommunications services such as T1/DS1s were designed to aggregate analog telephone lines for more efficient transport between central offices. Twenty four digitized voice lines (DS0s) were carried over a DS1 using time-division multiplexing (TDM). To review, in a TDM architecture, multiple channels (24 for DS0) share the circuit basically in rotation, with each DS0 having its own assigned time slot to use or not as the case may be. As each channel is always found in the same place no address is needed to demultiplex that channel at the destination. Twenty-eight (28) DS1s are TDM aggregated into a DS3 in the same manner. The older DS1/DS3 system is known as the Plesiochronous Digital Hierarchy (PDH), as the timing of signals across the network is Plesiochronous, which means almost but not precisely. Data communications networks such as Ethernet are asynchronous, as there is not a centralized timing source and each node has its own clock.

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As more and more channels are multiplexed together into higher layers of the PDH hierarchy, a number of problems arise. Since the timing on various DS1s going into a DS3 may differ slightly, bit-stuffing is required to align all within the DS3 frame. Once this is done, the individual DS1s are no longer visible unless the DS3 is completely demultiplexed. In order to select an individual channel, the whole DS3 frame must be torn down to extract out the DS1 and then subsequently rebuilt back into the DS3. The equipment required to do this is expensive. Another problem arises with interoperability of different networks with relatively wide differences in timing, such as those in Europe and the U.S. Expensive E xpensive equipment that also adds latency is required for the interface.

1.3.2 SYNCHRONOUS

To alleviate these problems, the Synchronous Optical Network (SONET) standardized  line rates, coding schemes, bit-rate hierarchies, and operations and maintenance functionality. SONET/SDH also defined the types of network elements required, network  architectures that vendors could implement, and the functionality that each node must  perform. Network providers could now no w use different vendor's optical equipment equ ipment with the t he confidence of at least basic interoperability interoperability

1.3.3 OPTICAL

The one aspect of SONET/SDH that has allowed it to survive during a time of  tremendous changes in network capacity needs is its scalability. Based on its open-ended  growth plan for higher bit rates, theoretically no upper limit exists for SONET/SDH bit rates (The current maximum bit rate deployed is 40 Gbps). However, as higher bit rates

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are used, physical limitations in the laser sources and optical fiber begin to make the  practice of endlessly increasing the bit rate on each signal an impractical solution. Additionally, connection to the networks through access rings has also had increased  requirements. Customers are demanding more services and options and are carrying more and different types of data traffic. To provide full end-to-end connectivity, a new  paradigm was needed to meet all the high-capacity and varied needs. Optical networks  provide such bandwidth and flexibility flexibility to enable end-to-end wavelength services. Opt ical networks began with wavelength division multiplexing (WDM), which arose to provide additional capacity on existing fibers. Like SONET/SDH, defined network elements and  architectures provide the basis of the optical network. However, unlike SONET/SDH, rather than using a defined bit-rate and frame structure as its basic building block, the optical network will be based on wavelengths. The components of the optical network  will be defined according to how the wavelengths are transmitted, groomed, or  implemented in the network. Viewing the network from a layered approach, the optical network requires the addition of an optical layer. To help define network functionality, networks are divided into several different physical or virtual layers. The first layer, the services layer, is where the services such as data traffic enter the telecommunications network. The next layer, SONET/SDH, provides restoration, performance monitoring, and provisioning that is transparent to the first layer. Emerging with the optical network  is a third layer, the optical layer. Standards are being developed and essentially can  provide the same functionality as the SONET/SDH SONET /SDH layer, while operating entirely e ntirely in the optical domain.

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The optical network also has the additional requirement of carrying varied types of high  bit-rate non-SONET/SDH optical signals that bypass the SONET/SDH layer altogether. a ltogether. Just as the SONET/SDH layer is transparent to the services layer, the optical layer will ideally be transparent to the SONET/SDH layer, providing restoration, performance monitoring,

and

provisioning

of

individual wavelengths

instead

of

electrical

SONET/SDH signals.

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Yusif Suleiman2308-0703-0223 BENEFITS OF SONET

In 1984, the Exchange Carriers Standards Association (ECSA) formulated the required  standard named SONET for the American National Standards Institute (ANSI (ANSI), ), which is responsible for setting telecommunications industry standards in the US. And it proposed  a method to interconnect the fiber optic systems from multiple vendors. Bellcore extended the original ECSA idea in 1985 and proposed what we now know as SONET. In 1988, the initial SONET standards were approved as ANSI documents T1.105-1988, which described optical rates and data format, and T1.106-1988, which described the  physical interface.

The key features and benefits ben efits of Multiservice SONET include:



Standards-Based – ensures compatibility across spans and between vendors



Deterministic & Predictable – robust, voice-centric heritage extends high

quality of service to all traffic 

Multiservice Capable – equally effective at carrying TDM and packet-based 

traffic including ATM, Ethernet and MPLS 

Fault Tolerant – protected rings provide 50 msec recovery from node and span

failures 

Mature Technology – well known technology and provisioning model



Price/Performance – one of the most cost effective architectures up to 10 Gbps

SONET provides an excellent network infrastructure (see diagram 3 for SONET multiservice network) for all types of mission critical cr itical traffic

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Diagram 3

SONET is slowly moving into everyday business life as bandwidth requirements within the enterprise increase. SONET, or Synchronous Optical Network, is the standard for  transmitting synchronous data on optical-electrical media. It allows the entire contents of  a 650-MB CD-ROM to move from coast to coast in less than one second. Businesses that can't contain their entire workforce in a single building are adding SONET rings to interconnect offices in MANs (metropolitan area networks), and Packet-Over-SONET has the potential to supplant ATM in a local area network and across a wide-area network. SONET signals are referenced re ferenced in two ways: STS (synchronous transport signal) is the electrical portion, and OC (optical carrier level) is the optical portion. Although SONET was designed to eliminate the electrical transmission of data, STS is used for very short distances, usually only within a switch cabinet. Until pure optical switching is available, the electrical equivalent is necessary.

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STS-x describes frame generation within a switch, since it is done electrically; OC-x describes transmission of the signal from point to point. Because SONET sends 8,000 STS frames per second--or one frame every 125 microseconds, the same frame rate that has been around since the DS-1 was invented--it's easy to incorporate current transmission timings. Bandwidth ranges from 51.84 Mbps at the OC-1 level to 9953.28Mbps at OC-192. There are specifications for higher bandwidths, with some vendors talking about OC-768 products--equivalent to seven CD-ROMs transmitted in one second--but these specifications have not been finalized. At the physical OC-x level, data travels in one of two ways--WDM (wave-division multiplexing) or DWDM (densewave-division multiplexing). WDM pulses a single laser to transmit data. The faster this laser can be pulsed, the more bandwidth that can be pushed through the fiber. WDM can effectively pulse a laser at OC-48 speeds. To reach higher bandwidths, however, the size of the pipe must be increased. Enter DWDM, which achieves a higher bandwidth by combining multiple OC-48 WDM lasers (each operating at a different wavelength)-essentially using the same pipe but enlarging it by transmitting more wavelengths of  light. The figure below show the t he multiplex SONET hierarchy.

Figure 4

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1.4.1 ADVANTAGES OF SONET

Some of the advantages of SONET are: • Currently used by all major Telecommunications Carriers (such as MCI (WorldCom), Qwest Communications, American Telephone and Telegraph (AT&T), and Verizon) • Very well-developed standards, both bot h international and domestic • Synchronous multiplexing format that greatly simplified simplified interfacing to other equipment • Precise performance monitoring and fault detection, facilitating centralized fault isolation • Creation of a set of generic standards to interconnect different vendors’ equipment.

1.4.2 DISADVANTAGES OF SONET

Some of SONET’s disadvantages are: • Limited flexibility to provide lines of varying speeds. For example, if a client needs 70Megabits of capacity, SONET can only provide either 51Megabits or 103Megabits  based on concatenation of STS-1 frames. The client would be required to purc hase more then he actually needs. • Requires significant equipment, at the carriers’ premises, to make the network run • Slow provisioning of the network elements often adds weeks to the completion of 

circuits.

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B. APPLICATION AND NETWORK  CONFIGURATIONS

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2.0 APPLICATION AND NETWORK CONFIGURATIONS 2.1

APPLICATION AREA

Since SONET was originally designed for the public telephone network. In the early 1980's, the forced breakup of AT&T in the United U nited States created numerous regional reg ional telephone companies, and these companies quickly encountered difficulties in networking with each other. Fiber optic cabling already prevailed for long distance voice traffic transmissions, but the existing networks proved unnecessarily expensive to build and  difficult to extend for so-called long haul data and/or video traffic. The American  National Standards Institute (ANSI) successfully devised SONET as the new standard for  these applications. Like Ethernet, SONET provides a "layer 1" or interface layer technology (also termed physical layer in the OSI model). As such, SONET acts as carrier of multiple higher-level application protocols. For example, Internet Protocol (IP)  packets can be configured to flow flow over SONET. In present day SDH and SONET networks, the networks are primarily statically configured. When a client of an operator  requests a point-to-point circuit, the request sets in motion a process that can last for  several weeks or more. This process is composed of a chain of shorter administrative and  technical tasks, some of which can be fully automated, resulting in significant improvements in provisioning time and in operational savings.

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Yusif Suleiman2308-0703-0223 SONET NETWORK TOPOLOGY

The most common architecture for the deployment of SONET is the ring. Multiple ADMs can be placed in a ring configuration. A primary benefit of the ring architecture is its survivability. The topology can be set up either as a ring or as a point-to-point system. In most networks, the ring is a dual ring, operating with two or more optical fibers. As noted, the structure of the dual ring topology permits the network to recover  automatically from failures on the channels and in the channel/machine interfaces.

One of SONET's most interesting characteristics is its support for a ring topology. Figure illustrates the concept of a SONET ring. Normally, one piece of fiber -- the working ring -- handles all data traffic, but a second piece of fiber -- the protection ring remains on standby. Should the working ring fail, SONET includes the capability to automatically detect the failure and transfer control to the protection ring in a very short period of  time... often in a fraction of a second. For this reason, SONET can be described as a selfhealing network technology.

Diagram 4

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Rings normally will help SONET service to reach the "five nines" availability level. However, the usefulness of rings also depends on their physical location. Imagine in this case two strands of fiber set only a few feet apart from each other... possibly even in the same trench! The likelihood of one problem disabling both fiber strands increases dramatically, effectively defeating the advantage of SONET rings. Note that SONET does not require rings: many SONET networks have been deployed in single-strand linear  architectures.

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Yusif Suleiman2308-0703-0223 NETWORK ARCHITECTURE

SONET have a limited number of architectures defined. These architectures allow for  efficient bandwidth usage as well as protection (i.e. the ability to transmit traffic even when part of the network has failed), and are fundamental to the worldwide deployment of SONET for moving digital traffic. Every SONET connection on the optical Physical layer uses two optical fibers, regardless of the transmission speed. Below figure shows the typical SONET Architecture.

Figure 5

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2.3.1 LINEAR AUTOMATIC PROTECTION SWITCHING

Linear Automatic Protection Switching (APS), also known as 1+1, involves four fibers: two working fibers (one in each direction), and two protection fibers. Switching is based  on the line state, and may be unidirectional (with each direction switching independently), or bidirectional (where the network elements at each end negotiate so that both directions are generally carried on the same pair of fibers).

In the asynchronous digital signal hierarchy environment, every time a d igital igital signal is accessed the entire signal needs to be multiplexed/demultiplexed, costing time and money at each site along a given path. However, a Linear Add/Drop configuration (see below figure) enables direct access to VTS/STS channels at each intermediate site along a fiber  optic path. Therefore the Linear Add/Drop configuration eliminates the need to process (multiplex/demultiplex) (multiplex/demultiplex) the t he entire optical signal for pass-through traffic.

Figure 6

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2.3.2 UNIDIRECTIONAL PATH-SWITCHED RING

In unidirectional path-switched rings (UPSRs), two redundant (path-level) copies of   protected traffic are sent in either direction around aro und a ring. A selector at the egress node determines which copy has the highest quality, and uses that copy, thus coping if one copy deteriorates due to a broken fiber or other failure. UPSRs tend to sit nearer to the edge of a network, and as such are sometimes called collector rings. Because the same data is sent around the ring in both directions, the total capacity of a UPSR is equal to the line rate N of the OC-N ring. For example, in an OC-3 ring with 3 STS-1s used to transport 3 DS-3s from ingress node A to the egress node D, 100 percent of the ring  bandwidth (N=3) would be consumed by nodes A and D. Any other nodes on the ring could only act as pass-through nodes. The SDH equivalent of UPSR is subnetwork  connection protection (SNCP); SNCP does not impose a ring topology, but may also be used in mesh topologies.

Figure 7

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2.3.3 BIDIRECTIONAL LINE-SWITCHED RING

Bidirectional line-switched ring (BLSR) comes in two varieties: two-fiber BLSR and  four-fiber BLSR. BLSRs switch at the line layer. Unlike UPSR, BLSR does not send  redundant copies from ingress to egress. Rather, the ring nodes adjacent to the failure reroute the traffic "the long way" around the ring on the protection fibers. BLSRs trade cost and complexity for bandwidth efficiency, as well as the ability to support "extra traffic" that can be pre-empted when a protection switching event occurs. In four-fiber  ring, either single node failures, or multiple line failures can be supported, since a failure or maintenance action on one line causes the protection fiber connecting two nodes to be used rather than looping loop ing it around the ring.

Figure 8

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BLSRs can operate within a metropolitan region or, often, will move traffic between municipalities. Because a BLSR does not send redundant copies from ingress to egress, the total bandwidth that a BLSR can support is not limited to the line rate N of the OC-N ring, and can actually be larger than N depending upon the traffic pattern on the ring. In the best case, all traffic is between adjacent nodes. The worst case is when all traffic on the ring egresses from a single node, i.e., the BLSR is serving as a collector ring. In this case, the bandwidth that the ring can support is equal to the line rate N of the OC-N ring. This is why BLSRs are seldom, if ever, deployed in collector rings, but often deployed in inter-office rings. The SDH equivalent of BLSR is called Multiplex Section-Shared  Protection Ring (MS-SPRING)

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C. IMPLEMENTATION

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3.0 IMPLEMENTATION

As the speed and bandwidth requirements of communications systems continue to increase, the adoption of fiber optic-based systems has never been more widespread than now. Fiber-based communication systems, including SONET (Synchronous Optical  Networking) provide the bandwidth necessary to enable reliable data communications across a wide area at high speeds (Gbps).

3.1

TECHNICAL CONTENTS

SONET is a grouping of physical layer specifications based on a signaling speed  hierarchy called STS or synchronous transport signals. SONET also defines sub levels of the STS-1 format. It is possible for STS-1 signals to be subdivided into segments called virtual tributaries. Virtual tributaries are synchronous s ignals that are used for the transport of lower-speed transmissions. Table 2 below contains a listing of virtual tributaries and their sizes.

Table 2. -Virtual Tributaries

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In order to compensate for frequency and phase variations, a concept known as "pointers" is used. Pointers allow the transparent transport of synchronous payload envelopes (either  STS or virtual tributaries) across plesiochronous boundaries, which are between nodes with separate network clocks having almost the same timing). Pointers are useful in helping avoid delays and data loss. SONET. When SONET was originally developed by Bellcore Labs in 1984, it was designed for use in domestic U.S. networks. However, SONET has been implemented for private LANs and WANs as well. SONET is a standard for the United States and Canada. It should be pointed out that although SONET and SDH are similar there are some fundamental differences; therefore the two standards don’t really interoperate. SONET is based on the STS-1 at 51.84 Mbps, which makes it an affective carrier of T3 signals. There is no STS-1 level for SDH. SDH starts at STS-3, which is also known as STM-1 (Synchronous Transport Module-1) equal to 155.52 Mbps, which makes SDH more suited for the carrying of E4 signals. The fundamental differences in SONET and SDH are mainly a result of different current rates in Europe and North America.

SONET/SDH Hierarchies

Table 3

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The future of SONET service delivery is bright and compares well with other  technologies for a variety of enterprise needs as shown in Diagram 5.

Diagram 5

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Yusif Suleiman2308-0703-0223 COST AND BENEFIT ANALYSIS

Cost Benefit Analysis can be defined as a decision making process or a process that aids in taking decisions and involves assessing the costs and benefits of one or more actions in order to choose the best and the most profitable option in the implementation of  network(system) architecture. The benefits must outweigh the costs for a project or idea to materialize. The analysis requires that the costs and benefits associated with the project  be expressed e xpressed in term t erm with the requirement for the purpose of assessing a ssessing the suitability o f  the project. One of the most important considerations in performing the cost benefit analysis is to ensure that all costs and benefits are identified identified and quantified qua ntified to it values.

In spite of the increasing interest towards newer and innovative technologies such as Ethernet and Internet protocol/multi-protocol label switching (IP/MPLS), synchronous optical network (SONET) still remains to be a preferred for metro and long distance services. This is expected to maintain its position as the leading transport technology in  North America for some time. Even though most opportunities for SONET technology are likely to emerge from wireless carrier customers, Internet service providers (ISPs), and content delivery providers, the industry faces a significant challenge i.e. competing services from IP/Ethernet. Eventually, many customers will slowly migrate to such nextgeneration technologies. This shift, for the most part, is driven by the quick growth of  data applications. The world SONET/SDH related test equipment market generated  revenues of $156.4 million in2007, with a growth rate of 2.8 percent over 2006. In 2014, the revenues are expected to reach$199.8 million (see table 4). The compound annual growth rate (CAGR) from 2007 to 2014 20 14 is estimated at3.6 percent.

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Table 4

Ethernet as a current alternative to SONET reduces the demand for SONET services. In the metro, Ethernet has many opportunities since standards development has been happening in that area, and carrier class features and reliability have been developed as well. Packet traffic continues to increase, but is still largely transported over legacy networks designed for voice traffic, meaning over SONET. IP VPNs are being offered  through SONET also. However, since IP is better suited to Ethernet, the demand for  Ethernet as a transport layer, replacing SONET, is growing. Ethernet offers the lowest cost interface for customers to connect to data services. Ethernet is widely used for   business transparent LANs, Internet access, and VPNs and is slowly replacing SONET elements in access networks. Ethernet services provisioned today in North America

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reveal, however, that they are still delivered over SONET. Using Generic Framing Procedure (GFP), Link Capacity Adjustment Scheme (LCAS) and Virtual Concatenation (VCAT) now allows SONET equipment to add native Ethernet interfaces to SONET multi-service provisioning platforms (MSPPs). As Ethernet standards are continuingly developing, increasing migration to carrier Ethernet or Ethernet over WDM is expected, as packetized traffic such as VoIP, data and video become a greater part of the traffic mix. Metro Ethernet networks currently have this capability, as do Ethernet access networks. SONET's longevity is also largely due to its quality, reliability and   performance, which have still not been entirely replicated even with the advances in Ethernet technology. With SONET deployments in North America, Asia, and Europe, and the large ATM and Frame Relay market that continues to exist (although declining), carriers are not expected to replace their many SONET network elements anytime soon. However, Ethernet services provisioning will continue to grow, in access and metro markets especially. Ethernet over SONET will continue to be the preferred method of   providing such services and it is viewed as a step to Ethernet or Ethernet over WDM migration in the future. Ethernet is the biggest threat to the SONET/SDH technology. The more Ethernet continues to develop carrier grade reliability, the more it will affect the growth of the SONET/SDH and OTN markets. Ethernet has already achieved dominance at the access level. It has not replaced SONET/SDH on a core network yet, but it expected to pose a threat to that technology over time. Currently, there only OTN and  SDH technologies that can perform higher bit (40G) transportation. At this point of time, there it is only one choice available for end users. There is a growing demand for 40G  bandwidth from router-to-router connections. Currently, 40 Gig test equipment costs

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more than 10 gig test equipment. This cost difference is hindering the development of the 40 gig test equipment market. The process of implementing 40gig on routers and SONET switches is currently not that cost-effective, when compared to the 10Gig application. There are limited investments to upgrade the networks to higher bit rates. Also operators and

manufacturers

are

uncertain

about

the

future

direction

of

the

market,

whether SONET/SDH is to be retained or overcome by pure Ethernet/IP. Moreover, from a field test equipment perspective, the transition to higher speed on the OTN for a field  unit, this adds technical challenges that have to be taken into consideration in order to make the field equipment manageable, especially for hand-held equipment types.

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Yusif Suleiman2308-0703-0223 CONCLUSION

The insatiable desire for increased bandwidth led to the development and deployment of  optical technology. However the potential of this technology has not been fully exploited. Currently, SONET sets the standard for optical communications with bit rates of up to 9.8 Gbps per wavelength channel. Although wavelength division multiplexing (WDM) has  been deployed, the number of wavelength channels per fiber is relatively small at the current time. Dense WDM that better utilizes the fiber capability further boosts the SONET capacity, along with the next generation bit rate of 40Gbps. Current research and  development in this area is utilizing this high bandwidth availability for future integrated  data transmissions, such as packets over SONET, broadcast TV, video on demand, and  video conferencing. These applications in turn induces fundamental impact on SONET itself, which leads to a new generation of technologies evolving from SONET, such as MPLS. Finally, SONET is consider as powerful protocol which is extensively used for  large and high performance networks. The cost appears to match its power. It is not something you will find running in a local insurance agency or doctor's office. It is, however, the solution chosen by the Department of Defense to run the DISN, a large wide area network for data, voice and video and on a smaller scale it is the network  chosen by Time Warner, Inc. to implement their "Full Service Network". SONET's compatibility with ATM, its network management capabilities, and its ability to support survivable topologies make the future importance of SONET as a data transport likely. the future of SONET is bright as the appropriate foundation for the breadth of service delivery and infrastructure consolidation needs.

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Yusif Suleiman2308-0703-0223 REFERENCES

1. Harry Newton, “Newton’s Telecom Dictionary,” CMP Books, New York, NY, 2002. 2. David Greenfield, “The Essential Guide to Optical Networks,” Prentice Hall, Upper Saddle River, NJ, 2002. 3. Uyless Black, “Optical Networks, Third Generation Transport Systems,” Prentice Hall, Upper Saddle River, NJ, 2002. 4. M. Scholten, et al, “Data Transport Applications Using GFP”, IEEE Communications Magazine, May 2002, pages 96 - 103. 5. Ieee xplore digital library, Cavendish, D. C&C Res. Communications Magazine, Labs.,

USA

Volume:

38,

Issue:

6,

Pages:

164



172

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=846090&url=http%3A%2 F%2Fieeexplore.ieee.org%2Fiel5%2F35%2F18353%2F00846090.pdf%3Farnum  ber%3D846090 6. Gigabit Ethernet for Metro Area Networks, Paul Bedell. 2003. Page 329. 7. Dale Barr, JR., Peter M. Fonash: Internet Protocol over Optical Transport  Networks; National Communication Technologies, Inc. Dec 2003. Page 9, 43 to 47. 8. Lucent Technologies, Frank Hiatt, SONET Synchronous Optical Networking: Technical Review, Bell Labs Innovations. Jan 1999. Page 6 to 11, 16 to 18. 9. Werner Habisreitinger, Acterna Germany GmbH 2004. SONET Fundamental and  Testing. Page 4 to 9, and 69. www.jdsu.com

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10. D. Cavendish et al, “New Transport Services for Next-Generation SONET/SDH Systems”, IEEE Communications Magazine, May 2002, Pages 80 to 87. 11. M. Scholten, et al, “Data Transport Applications Using GFP”, IEEE Communications Magazine, May 2002, Page 96 to 103. 12. G.709 – Uniphase Corporation, Andreas Schubert, The Optical Transport  Network(OTN) 2008, Page 9 to 12. 13. Tektronix, SONET web proForum tutorials: the international Engineering Consortium. Page 21 to 37. http://www.iec.org 14. NPS, 14. NPS, Kaun Chou Loh, Simulation and Performance Analysis of Routing in SONET/SDH Data Communications Network(DCN). Dec 2006. Page 2 to 18. 15. G.7712, G.7712, “Vertel “Vertel Supports, Latest Optical Network Management Standard”, Embedded Stars, last accessed 23 September 2006. http://www.embeddedstar.com/press/content/2003/3/embedded7896.html,, http://www.embeddedstar.com/press/content/2003/3/embedded7896.html 16. ECI Lightsoft Network Management Solutions General Description Handbook, 2nd Edition, ECI, June 2006. 2006. Page 64. 17. Making Ethernet over  SONET, D. Frey, F. Moore, “A Transport Network  Operations Model”, Proceedings NFOEC, 2003. Page 29.

18. Generic Framing Procedure (GFP), P. Bonenfant and A. Rodriguez-Moral, “The Catalyst for Efficient Data over Transport”, IEEE Communications Magazine, May 2002, Page 72 to 73. 19. New 19. New Transport Services for Next-Generation SONET/SDH Systems, D. Cavendish, “IEEE Communications Magazine”, May 2002, Page 80 to 83.

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20. Data Transport Applications Using GFP, M. Scholten, “IEEE Communications Magazine”, May 2002, Page 96 to 99. 21. Hybrid Transport Solutions for TDM/Data Networking Services, E. HernandezValencia, “IEEE Communications Magazine”, May 2002, Page 104 - 112.

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Yusif Suleiman2308-0703-0223 APPENDICES

5.1 APPENDIX A

ACRONYMS

DESCRIPTION

A ADM:

Add-Drop Multiplexer 

ANSI

American National Standards Institute

ARIN

American Registry for Internet Numbers

AS

Autonomous System

ASN

Autonomous System Number 

ASIC

Application-Specific Integrated Circui Circuitt

ATM

Asynchronous Transfer Mode

B BGP4

Border Gateway Protocol Version 4

BGP

Border Gateway Protocol

C COTS

Commercial Off The Shelf 

CR-LDP

Constraint Based Routed-Label Distribution Protocol

CAPEX

Capital Expense

CORBA

Common Object Request Broker Archi Architecture tecture

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D DCS

Digital Cross-connect System

DSX

Digital Signal Cross-connect

DVB-ASI

Digital Video Broadcast – Asynchronous Serial Interface

DCC

Data Communications Channel

DWDM

Dense Wavelength Division Multiplexing

E EGP

Exterior Gateway Routing Protocol

EMS

Element Management System

EOP

Executive Office of the President

F FEC

Forward Equivalence Classes

FOA

Fiber-Optic Amplifier 

FOTS

Fiber-optic Transmission System

FSC

Fiber Switch Cable

G Gbps

Gigabits per second 

GFP

Generic Framing Protocol

GHz

Gigahertz

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Yusif Suleiman2308-0703-0223 Generalized Multi Protocol Label Switching

H HF

High Frequency

I IDN

Integrated Digital Digital network 

IEEE

Institute of Electrical and Electronics Engineers

IGP

Interior Gateway Routing Protocol

IETF

Internet Engineering Task Force

ILEC

Incumbent Local Exchange Carrier 

IOF

Interoffice Facilities

IXC

Interexchange Carrier 

IP

Internet Protocol

IPv4

Internet Protocol Version 4

IPv6

Internet Protocol Version 6

IS-IS

Intermediate System to Intermediate System Protocol

ISO

International Organization for standards

ITU

International Telecommunication Union

ITU-T

ITU Telecommunications Standardization Sector 

L L2SC

Layer 2 Switched Capable

L2

Layer 2

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L3

Layer 3

LCAS

Link Capacity Adjustment Scheme

LAN

Local Area Network 

LDP

Label Distribution Protocol

LER

Label Edge Router 

LSC

Lambda Switch Capable

LSP

Label Switched Path

LSR

Label Switched Router 

M MAN

Metropolitan Area Network 

Mbps

Megabits per second 

MEMS

Micro Electromechanical System

MONET

Multiwavelength Optical Networking

MPOA

Multi Protocol over ATM

MPOE

Minimum Point of Entry

MPLS

Multi Protocol Label Switching

MSO

Multiple System Operator 

MSPP

MultiService Provisioning Platform

N  NCS

National Communications System

 NE

Network Element

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 NG

Next-Generation

 NMS

Network Management System

nm

Nanometer 

 NNI

Network to Network Interface

 NS/EP

National Security and Emergency Preparedness

O OA

Optical Amplifier 

OADM

Optical ADM

OAM

Operations, Administration and Management

OCh

Optical Channel

OMNCS

Office of the Manager, National Communications System

OMS

Optical Multiplex Section

OSC

Optical Supervisory Channel

OSPF

Open Shortest Path First Protocol

OTN

Optical Transport Network 

OTS

Optical Transmission Section

OLT

Optical Line Terminal

OPEX

Operational Expense

OSS

Operational Support System

OXC

Optical Cross Connect

P

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PCS

Personal Communications Service

PDI-P

Payload Defect Indicator – Path

PDI-V

Payload Defect Indicator – Virtual

PDN

Packet Data Network 

PON

Passive Optical Network 

PHY

Physical Layer 

PM

Physical Medium

PMD

Polarization Mode Dispersion

PN

Public Network 

PSN

Public Switched Network 

PPP

Point-to-Point Protocol

PVC

Permanent Virtual Circuit

PVP

Permanent Virtual Path

Q QoS

Quality of Service

R RDI

Remote Defect Indication

RFC

Request For Comment

R&D

Research and Development

RSVP

Resource Reservation Protocol

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S SAN

Storage Area Network 

SDH

Synchronous Data Hierarchy

SONET

Synchronous Optical Network 

STS

Synchronous Transport Signal

T TCP

Transmission Control Protocol

TCP/IP

Transmission Control Protocol/Internet Protocol

TDM

Time Division Multiplexing

TIB

Technical Information Bulletin

U UNI

User Network Interface

V VPN

Virtual Private Network 

W WADM

Wavelength Add-Drop Multiplexer 

WAN

Wide Area Network 

WDM

Wavelength Division Multiplexing

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5.2 APPENDIX B GLOSSARY Add/drop

The process where a part of the information carried in a transmission system syste m is demodulated (dropped) at an intermediate point po int and different information is entered (added) for subsequent transmission; t ransmission; the remaining traffic passes straight through the multiplexer without additional processing Add/drop multiplexer (ADM)

The process where a part of the information carried in a transmission system syste m is demodulated (dropped) at an intermediate po int and different information information is entered (added) for subsequent transmission; t ransmission; the remaining traffic passes straight through the multiplexer without additional processing Alarm indicating signal (AIS)

A code sent downstream indicating an upstream failure has occurred; SONET defines the following four categories of AIS: line AIS, STS path AIS, VT path p ath AIS, DS–n AIS Alternate mark inversion (AMI)

The line-coding format in transmission systems where successive ones (marks) are alternatively inverted (sent with polarity opposite that o f the preceding mark) American National Standards Institute (ANSI)

A membership organization that develops U.S. industry standards and  coordinates U.S. participation in the International St andards Organization (ISO)

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Asynchronous

A network where transmission system payloads are not synchronized, and each network terminal runs on its own clock  Asynchronous transfer mode (ATM)

A multiplexing or switching technique in which information is organized into fixed-length cells with each cell consisting cons isting of an identification header field and an information field; the transfer mode is asynchronous in the sense that the use of  the cells depends on the required or instantaneous bit rate Attenuation

Reduction of signal magnitude or signal loss, usually expressed in decibels Automatic protection switching (APS)

The ability of a network element to detect a failed working line and switch sw itch the service to a spare (protection) line; line; 1+1 APS pairs a protection line with each working line; 1:n APS provides one protection line for every n working lines Bandwidth

Information-carrying capacity of a communication channel; analog bandwidth is the range of signal frequencies that can be transmitted by a communication channel or network  Bidirectional

Operating in both directions; bidirectional APS allows protection switching to be initiated by either end of the line Binary N-zero suppression (BNZS)

Line coding system that replaces N number of zeros with a special code to

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maintain pulse density required for synchronization; N is typically 3, 6, or 8 Bit error vs. block error

Error rate statistics play a key role ro le in measuring the performance of a network; as errors increase, user payload pa yload (especially data) must be retransmitted; the end  effect is creation of more (nonrevenue) traffic in the network  Bit interleaved parity (BIP)

A parity check that groups all the bits in a block into units (such as byte), then  performs a parity check for each bit position in a group Bit interleaved parity–8 (BIP–8)

A method of error checking in SONET that allows a full set of o f performance statistics to be generated; for example, a BIP–8 creates eight-bit (one-byte) groups, then does a parity check for each of the eight-bit positions in the byte Bit 7

One binary digit; a pulse of data Bit stuffing

In asynchronous systems, a technique used to synchronize asynchronous signals to a common rate before multiplexing Bit synchronous

A way of mapping payload into VTs that synchronizes all inputs into the VTs, but does not capture any framing information or allow access to subrate channels carried in each input; for example, bit synchronous mapping of a channeled DS–1 into a VT1.5 does not provide access to the DS–0 channels carried by the DS–1 Bits per second (bps)

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The number of bits passing a point every second; the transmission rate for digital information Block error rate (BLER)

One of the underlying concepts of error performance is the notion of errored   blocks—blocks in which one o ne or more bits are in error; er ror; a block is a set of the International Internat ional Engineering Consortium consecutive bits associated with the path or section monitored   by means of an error detection code (EDC), such as bit interleaved parity (BIP); block  error rate (BLER) is calculated with the foll fo llowing owing formula: BLER = (errored blocks received)/(total blocks sent) Broadband

Services requiring 50–600 Mbps transport capacity Broadband integrated services digital network (BISDN)

A single ISDN that can handle voice, data, and eventually video services Byte interleaved

Bytes from each STS–1 are placed in sequence in a multiplexed or concatenated  STS–N signal; for example, for an STS–3, the sequence of bytes from contributing STS–1s is 1, 2, 3, 1, 2, 3, etc. Byte synchronous

A way of mapping payload into VTs that synchronizes all inputs into the VTs, captures framing information, and allows access to subrate channels carried in each input; for example, byte synchronous mapping of a channeled DS–1 into a VT1.5 provides direct access to the DS–0 channels carried by the DS–1 CCITT

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The technical organs of the United Nations specialized agency for  telecommunications, now the International Telecommunications Union—  Telecommunications; they function through international committees of  telephone administrations and private operating agencies Channel

the smallest subdivision of o f a circuit that provides a type of communication co mmunication service; usually a path with only one direction Circuit

A communications path or o r network; usually a pair of channels providing  bidirectional communication Circuit switching

Basic switching process whereby a circuit between two users is opened on demand and maintained for their exclusive use for the duration of the transmission Coding violation (CV)

A transmission error detected by the difference d ifference between the transmitted and the locally calculated bit-interleaved parity Concatenate

The linking together of various data structures—for example, two bandwidths  joined to form a single bandwidth Concatenated STS–Nc

A signal in which the STS envelope capacities from the N STS–1s have been combined to carry an STS–Nc STS –Nc SPE; it is used to transport signals that do not fit fit

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Into an STS–1 (52 Mbps) payload  Concatenated VT

A VT x Nc that is composed of N x VTs combined; its payload is transported as a single entity rather than separate signals Cyclic redundancy check (CRC)

A technique for using overhead bits to detect transmission errors Data communications channels

OAM&P channels in SONET that enable communications between intelligent controllers and individual network nodes as well as internode communications Defect

A limited interruption in the ability of an item to perform perform a required requ ired function Demultiplexing

A process applied to a multiplex signal for recovering signals combined within it and for restoring the distinct individual channels of the signals Digital cross-connect system (DCS)

An electronic cross-connect that has access to lower-rate channels in higher-rate multiplexed signals and can electronically rearrange (cross-connect) those channels Digital signal

An electrical or optical signal that varies in discrete steps; electrical signals are coded as voltages; optical signals are coded as pulses of light DSX–1

May refer to either a cross-connect for DS–1 rate signals or the signals crossconnected 

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at an DSX–1 DSX–3

May refer to either a cross-connect for DS–3 rate signals or the signals crossconnected  at an DSX–1 Envelope capacity

the number of bytes the payload envelope of a single frame can carry; the SONET STS payload envelope is the 783 bytes of the STS–1 frame available to carry asignal; each VT has an envelope capacity defined as the number of bytes in the VT less the bytes used by VT overhead  European Conference of Postal and Telecommunications Administrations (CEPT)

The CEPT format defines the 2.048–Mbps European E1 signal made up of 32 voice-frequency channels Exchange Carrier Standards Association (ECSA)

An organization that specifies telecommunications te lecommunications standards for ANSI Failure

A termination of the ability of an item to perform a required function; a failure is caused by the persistence of a defect Far end block error (FEBE)

A message sent back upstream that receiving network element is detecting errors, usually a coding violation Far end receive failure (FERF)

a signal to indicate to t he transmit site that a failure has occurred at the receive

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site Fixed stuff 

A bit or byte whose function is reserved; fixed-stuff locations, sometimes so metimes called  reserved locations, do not carry overhead or payload  Floating mode

A VT mode that allows the VT synchronous payload envelope to begin anywhere in the VT; pointers identify the starting st arting location of the VT SPE; VT SPEs S PEs in different superframes may begin at different different locations Framing

Method of distinguishing digital channels that have been multiplexed together  Frequency

The number of cycles o f periodic activity that occur in a discrete amount of time Grooming

Consolidating or segregating traffic for efficiency Interleave

The ability of SONET to mix together and transport different types of input Signals in an efficient manner, thus allowing higher transmission rates Isochronous

All devices in the network netwo rk derive their timing signal directly or indirectly from the same primary reference clock  Jitter

Short waveform variations caused by vibration, voltage fluctuations, control system instability, etc.

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Line

One or more SONET sections, including network elements at each end, capable of  accessing, generating, and processing line overhead  Line alarm indication signal (AIS −L)

AIS–L is generated by section terminating equipment (STE) upon the detection of a loss of o f signal or loss of frame defect, on o n an equipment failure; AIS–L maintains operation of the downstream do wnstream regenerators and therefore prevents generation of unnecessary alarms; a larms; at the same time, data and orderwire communication is retained between the regenerato rs and the downstream line terminating equipment (LTE) Line overhead (LOH)

18 bytes of overhead accessed, generated, and processed by line terminating equipment; this overhead supports functions such as locating the SPE in the frame, multiplexing or concatenating signals, performance monitoring, automatic protection switching, and line maintenance Line remote defect indication (RDI–L)

A signal returned to the transmitting line terminating ter minating equipment (LTE) upon detecting a loss of signal, loss of frame, or AIS–L defect; RDI–L was previously known as line FERF Line terminating equipment (LTE)

 Network elements such as add/drop multiplexers or digital cross-connect systems that can access, generate, and process line overhead  Locked mode

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A VT mode that fixes the starting location of the VT SPE; locked mode has less  pointer processing than floating mode Map/demap

A term for multiplexing, implying more visibility inside the resultant multiplexed   bit stream than available with conventional asynchronous techniques Mapping

The process of associating each bit transmitted by a service into the SONET  payload structure that carries the service; for example, mapping a DS–1 service into a SONET VT1.5 associates each bit of the DS–1 with a location in the VT1.5 Mesochronous

A network whereby all nodes are timed to a single clock c lock source; thus, all timing is exactly the same (truly synchronous) Multiplex (MUX)/demultiplex (DEMUX)

Multiplexing allows the transmission of two or o r more signals over a single channel; demultiplexing is the process of separating previously combined signals and restoring the distinct individual channels o f the signals Multiplexer

a device for combining co mbining several channels to be carried by one o ne line or fiber  Narrowband

Services requiring up to 1.5–Mbps transport capacity Network element (NE)

Any device that is part of a SONET transmission path and serves one or more of  the section, line, and path-terminating path-t erminating functions; in SONET, the five basic

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network elements are as follows: follows: • add/drop multiplexer  • broadband digital cross-connect • wideband digital cross-connect • digital loop carrier  • switch interface Operations, administration, maintenance, and provisioning (OA&M or OAM&P)

Provides the facilities and personnel required to manage a network  Operations system (OS)

Sophisticated applications software that overlooks the entire network  Optical carrier level N (OC–N)

The optical equivalent of an STS–   N signal Orderwire

A channel used by installers to expedite the provisioning of lines OSI seven-layer model

A standard architecture for data communicati co mmunications; ons; layers define hardware and  software required for multivendor information-processing equipment to bemutually compatible; the seven layers from lowest to highest are physical, link, network, transport, session, presentation, and application Overhead

Extra bits in a digital stream used to t o carry information besides traffic signals; orderwire, for example, would be considered o verhead information

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Packet switching

An efficient method for breaking down do wn and handling high-volume traffic in a network; a transmission technique that segments and routes information into discrete units; packet switching allows for efficient sharing of network resources as packets from different sources can all be sent over the same channel in the same bitstream Parity check

An error-checking scheme that examines the number of transmitted bits in a  block that hold the value one; for even parity, an overhead parity bit is set to either one or zero to make the total number of transmitted ones an even number; for odd parity, the parity bit is set to make the total number of o f ones transmitted  an odd number. Path

A logical connection between a point where an STS or VT is multiplexed to the  point where it is demultiplexed  Path overhead (POH)

Overhead accessed, generated, and processed by path-terminating equipment; POH includes 9 bytes of STS POH and, when the frame is VT–structured, 5 bytes of VT POH Path terminating equipment (PTE)

 Network elements, such as fiber-optic terminating systems, which can access, generate, and process POH Payload

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The portion of the SONET signal available to carry service signals such as DS–1 and DS–3; the contents of an STS SPE or VT SPE Payload pointer

Indicates the beginning of the synchronous payload envelope (SPE) Photon

The basic unit of light ttransmission ransmission used to define the lowest (physical) layer in the OSI seven-layer model Plesiochronous

a network with nodes timed by separate clock sources with almost the same timing Point of presence (POP)

A point in the network netwo rk where interexchange carrier facilities like DS–3 or OC–N meet with access facilities managed by telephone companies or other service  providers Pointer

A part of the SONET overhead that locates a floating payload structure; STS  pointers locate the SPE; VT pointers locate floating mode VTs; all SONET frames use STS pointers; only floating mode VTs use VT pointers Poll

An individual control message from a central controller to an individual station on a multipoint network inviting that station to send  Regenerator

device that restores a degraded digital signal for continued transmission; also

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called a repeater  Remote alarm indication (RAI)

A code sent upstream in a DS–n network netwo rk as a notification that a failure condition has been declared dec lared downstream; RAI signals were previously referred to as yellow signals Remote defect indication (RDI)

A signal returned to the transmitting terminating equipment equ ipment upon detecting a loss of signal, loss of frame, or AIS defect; RDI was previously known as FERF Remote error indication (REI)

An indication returned to a transmi t ransmitting tting node (source) that an errored block has  been detected at the receiving node (sink); this indication was formerly known as far end block error (FEBE) Remote failure indication (RFI)

A failure is a defect that t hat persists beyond the maximum time allocated to the transmission system protection mechanisms; when this situation occurs, an RFI is sent to the far end and will initiate a protection switch if this function has been enabled  Section

The span between two SONET network elements capable of accessing, generating, and processing only SONET section overhead; this is the lowest layer of the SONET protocol stack with overhead  Section overhead

 Nine bytes of overhead accessed, generated, and processed by section terminating

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equipment; this overhead supports functions such as framing the signal and   performance monitoring Section terminating equipment (STE)

Equipment that terminates the SONET section layer; STE interprets and modifies or creates the section overhead  Slip

An overflow (deletion) or underflow (repetition) of one frame of a signal in a receiving buffer  Stratum

Level of clock source used to categorize accuracy STS path remote defect indication (RDI–P)

A signal returned to the transmitting STS path terminating equipment (PTE) upon detection of certain defects on the incoming path STS path terminating equipment (PTE)

Equipment that terminates the SONET STS path layer; STS PTE interprets and  modifies or creates the STS POH; an NE that contains STS PTE will also contain LTE and STE STS POH

 Nine evenly distributed POH bytes per 125 microseconds starting at the first byte of the STS SPE; STS POH provides for communication between the point of  creation of an STS SPE and its point of disassembly Superframe

Any structure made of multiple frames; SONET recognizes superframes at the

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DS–1 level (D4 and extended superframe) and at the VT (500 µs STS superframes) Synchronous

A network where transmission system payloads are synchronized to a master  (network) clock and traced to a reference clock  Synchronous digital hierarchy (SDH)

The ITU–T–defined world standard of transmission whose base transmission level is 52 Mbps (STM–0) and is equivalent to SONET's STS–1 or OC–1 transmission rate; SDH standards were published in 1989 to address interworking between the ITU–T and ANSI transmission hierarchies Synchronous optical network (SONET)

A standard for optical transport that defines o ptical carrier levels and their  electrically equivalent synchronous transport signals; SONET allows for a multivendor environment and positions the network net work for transport of new services, synchronous networking, and enhanced OAM&P Synchronous payload envelope (SPE)

The major portion of the SONET frame format used to transport payload and STS POH; a SONET structure that carries the payload (service) in a SONET frame or  VT; the STS SPE may begin anywhere in the frame's payload envelope; the VT SPE may begin anywhere in a floating mode VT but begins at a fixed location in a locked-mode VT Synchronous transfer module (STM)

An element of the SDH transmission hierarchy; STM–1 is SDH's base-level

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transmission rate equal to 155 Mbps; higher rates of STM–4, STM–16, and STM–  48 are also defined  Synchronous transport signal level 1 (STS–1)

The basic SONET building block signal transmitted at 51.84–Mbps data rate Synchronous transport signal level N (STS–N)

The signal obtained by multiplexing integer multiples multiples ( N ) of STS–1 signals together  T1X1 subcommittee

A committee within ANSI that specifi spec ifies es SONET optical op tical interface rates and  formats Virtual tributary (VT)

A signal designed for transport and switching of sub–STS–1 payloads VT group

A 9-row by 12-column 12-co lumn structure (108 bytes) that carries one or more VTs VT s of the same size; seven VT groups can be fitted into one STS–1 payload  VT path remote defect indication (RDI–V)

A signal returned to the transmitting VT PTE upon detection of certain defects on the incoming path VT path remote failure indication (RFI–V)

A signal, applicable only to a VT1.5 with the byte-synchronous DS–1 mapping, that is returned to the transmitting VT PTE P TE upon declaring certain failures; the RFI–V signal was previously known as the VT path yellow signal VT path terminating equipment (VT PTE)

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Equipment that terminates the SONET VT path layer; VT PTE interprets and  modifies or creates the VT POH; an NE that contains VT PTE PT E will also contain STS PTE, LTE, and STE POH VT POH

Four evenly distributed POH bytes per VT SPE starting at the first byte o f the VT SPE; VT POH provides for communication between the point of o f creation of an VT SPE and its point of disassembly Wander

Long-term variations in a waveform Wideband

Services requiring 1.5− to 50−Mbps transport capacity

5.3 APPENDIX C INTERNET ADDRESSES OF STANDARDS BODIES AND FORUMS International Telecommunications Union: http://www.itu.int/

Internet Engineering Task Force: http://www.ietf.org/home.html Optical Internetworking Forum: http://www.oiforum.com/ Telecommunications Industry Association (TIA): www.tiaonline.org International Electrical Electronic Engineers (IEEE) www.ieee.org

5.4 APPENDIX D: RECOMMENDATION

I recommend this Project to my fellow IT students to go through and do some research over it, so that the t he project will serve as a guide gu ide to them during their own leaning, assignments and projects.

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