Computer Network & Internet

JSIIT Yusif Suleiman2308-0703-0223

i IADNCS Computer Network & Internet (CNW201)

Computer Institute Kazaure, Jigawa State, Nigeria

Computer Network and Internet(CNW201) Project Documentation

ON

Synchronous Optical Network (SONET)

By

Yusif Suleiman

2308-0703-0223

Supervisor/lecturer: Mr. Nura Tijjani Abubakar

Date: 20th June, 2012


ii IADNCS Computer Network & Internet (CNW201)

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.


iii IADNCS Computer Network & Internet (CNW201)

ACKNOWLEDGEMENT All Praise be to Allah, the exalted and the most highly Gracious, lord of the world the

beneficent, the 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 Suleiman 2308-0703-0223


iv IADNCS Computer Network & Internet (CNW201)

Table of Contents CONTENT PAGES Cover …………………………………………………………………………………..i

Certification of Work………………………………………………………………….ii

Acknowledgement…………………………………………………………………....iii

Table of Contents………………………….……………………………………….....iv

List of Figures…………………………………………………………………………vi

List of Diagram………………………………………………………………………..vi

List of Tables………………………………………………………………………….vi

1.0 Introduction…………………...………………….……….…………………….…1 1.1 Objective………………..………………………………..………………………..2 1.1.1 High Transmission rate………………………………………………………..5 1.1.2 Simplified Add and Drop Function………………………….………………..5 1.1.3 High Availability and Capacity Maching……………………..……………….6 1.1.4 Reliability………………………………………………………..……………..6 1.1.5 Future-Proof Platform for New Services……………………………..………..7 1.1.6 Interconnection………………………………………………….……………..8

1.2 The History………………………………………………………………………..11

1.3 Current Technology…………………………………………………….…………13 1.3.1 Asynchronous………………………………………………..……………….13 1.3.2 Synchronous…………………………………………………………………..14 1.3.3 Optical……………………………………………………….……………….14

1.4 Benefits of SONET………………………………………………………………17 1.4.1 Advantages of SONET………………………………………………..……..20 1.4.2 Disadvantage of SONET…………………………………………………….20 2.0 Application and Network Configurations………………….……………………21 2.1 Application Area…………………………………………………………………22 2.2 SONET Network Topology…………………………………..………………….23 2.3 Network Architecture…………………………………………………………….25 2.3.1 Liner Automatic Protection Switching…………………………….…………...26 2.3.2 Undirectional Path Switched Ring………………………….………………….27 2.3.3 Bidirectional Line Switched Ring……………………………………………...28 3.0 Implementation……………………………………………………………………..30


v IADNCS Computer Network & Internet (CNW201)

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


vi IADNCS Computer Network & Internet (CNW201)

List of Figures 1. Figure 1: SONET Physical Network Connection……………….3

2. Figure 2: Simplified Add/Drop Function………………………..5

3. Figure 3: SONET Network HUB………………………………..8

4. Figure 4: SONET Multiplex Hierarchy…………………………19

5. Figure 5: Typical SONET Network Mgt Com Architecture……25

6. Figure 6: Add/Drop Liner 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………………………………..7

2. Diagram 2: Dual Ring Interworking (DRI)………………………..9

3. Diagram 3: Multiservice SONET Network……………………….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

3. Table 3: SONET/SDH Hierarchies…………………...…………..32

4. Table 4: Market Revenue Forecast……………………………….35


IADNCS Computer Network & Internet (CNW201) 1

A. INTRODUCTION



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.



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



1.1 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 the network industry, with the possibility 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:



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



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.



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.



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.



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 traffic to be

resilient from a SONET multiplexer node failure. If a catastrophe takes out a SONET

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 deployed in central office topologies.

Diagram 2 illustrates a DRI configuration.



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 OC-

3c) into which ATM cells, IP packets, or Ethernet frames are placed.



1.2 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 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



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.



1.3 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.



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 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 use different vendor's optical equipment with the

confidence of at least basic 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



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 to enable end-to-end wavelength services. Optical

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 layer, while operating entirely in the

optical domain.



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.

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.



1.4 BENEFITS OF SONET

In 1984, the Exchange Carriers Standards Association (ECSA) formulated the required

standard named SONET for the American National Standards Institute (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 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 traffic



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 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.



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 (dense-

wave-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 multiplex SONET hierarchy.

Figure 4



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 international and domestic

• Synchronous multiplexing format that greatly 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 purchase 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.



B. APPLICATION AND NETWORK

CONFIGURATIONS



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 States created numerous regional

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 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.



2.2 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 self-

healing network technology.

Diagram 4



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.



2.3 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



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 digital 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) the entire optical signal for pass-through traffic.

Figure 6



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 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



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 it around the ring.

Figure 8



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)



C. IMPLEMENTATION



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 signals 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



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



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



3.2 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 in term with the requirement for the purpose of assessing the suitability of

the project. One of the most important considerations in performing the cost benefit

analysis is to ensure that all costs and benefits are identified and quantified 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 next-

generation 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 is estimated at3.6 percent.



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



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



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.



3.3 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.



4.0 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



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, 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, “Vertel Supports, Latest Optical Network Management Standard”,

Embedded Stars, last accessed 23 September 2006.

http://www.embeddedstar.com/press/content/2003/3/embedded7896.html,

16. ECI Lightsoft Network Management Solutions General Description

Handbook, 2nd Edition, ECI, June 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 Transport Services for Next-Generation SONET/SDH Systems, D.

Cavendish, “IEEE Communications Magazine”, May 2002, Page 80 to 83.



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. Hernandez-

Valencia, “IEEE Communications Magazine”, May 2002, Page 104 - 112.



5.0 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 Circuit

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 Architecture



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



GMPLS Generalized Multi Protocol Label Switching

H

HF High Frequency

I

IDN Integrated 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



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



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



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



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



5.2 APPENDIX B

GLOSSARY

Add/drop

The process where a part of the information carried in a transmission system is

demodulated (dropped) at an intermediate point and different information is

entered (added) for subsequent transmission; 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 is

demodulated (dropped) at an intermediate point and different information is

entered (added) for subsequent transmission; 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 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 of 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 Standards Organization (ISO)



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 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 the

service to a spare (protection) 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



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 in measuring the performance of a network; as

errors increase, user payload (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 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)



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 or more bits are in error; a block is a set of the International

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 following 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



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 a circuit that provides a type of communication

service; usually a path with only one direction

Circuit

A communications path or 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 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 SPE; it is used to transport signals that do not fit



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 a required 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



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 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 the transmit site that a failure has occurred at the receive



site

Fixed stuff

A bit or byte whose function is reserved; fixed-stuff locations, sometimes 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 location of the VT SPE; VT SPEs in

different superframes may begin at different locations

Framing

Method of distinguishing digital channels that have been multiplexed together

Frequency

The number of cycles of 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 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.



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 signal or loss of frame defect, on an equipment failure; AIS–L

maintains operation of the downstream regenerators and therefore prevents

generation of unnecessary alarms; at the same time, data and orderwire

communication is retained between the regenerators 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 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



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 source; thus, all timing is

exactly the same (truly synchronous)

Multiplex (MUX)/demultiplex (DEMUX)

Multiplexing allows the transmission of two or more signals over a single

channel; demultiplexing is the process of separating previously combined signals

and restoring the distinct individual channels of the signals

Multiplexer

a device for combining several channels to be carried by one 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 functions; in SONET, the five basic



network elements are as 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 communications; 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 carry information besides traffic signals;

orderwire, for example, would be considered overhead information



Packet switching

An efficient method for breaking down 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 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



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 transmission 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 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



called a repeater

Remote alarm indication (RAI)

A code sent upstream in a DS–n network as a notification that a failure condition

has been declared downstream; RAI signals were previously referred to as yellow

signals

Remote defect indication (RDI)

A signal returned to the transmitting terminating equipment 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 transmitting 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 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



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



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 optical carrier levels and their

electrically equivalent synchronous transport signals; SONET allows for a

multivendor environment and positions the network 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



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 (N) of STS–1 signals

together

T1X1 subcommittee

A committee within ANSI that specifies SONET optical 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 structure (108 bytes) that carries one or more VTs 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 upon declaring certain failures; the

RFI–V signal was previously known as the VT path yellow signal

VT path terminating equipment (VT PTE)



Equipment that terminates the SONET VT path layer; VT PTE interprets and

modifies or creates the VT POH; an NE that contains VT PTE will also contain

STS PTE, LTE, and STE POH

VT POH

Four evenly distributed POH bytes per VT SPE starting at the first byte of the VT

SPE; VT POH provides for communication between the point of 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 project will serve as a guide to them during their own leaning,

assignments and projects.



THIS PAGE INTENTIONALLY LEFT BLANK

Computer Network & Internet

Documents

Transcript of Computer Network & Internet