White Paper

 

PM_v1.0_20_Mar_2002

Performance Monitoring

 

Author: Vikas M. Valsang

 

1.    Summary

 

With the advent of Optical Networks, the enterprise market started growing exponentially. Intranet and Internet explosion and Bandwidth hungry applications are evolving. And with FTTX technology is rapidly growing the ability to carry data at higher bit rates has virtually caused a revolution in digital transmission. This required the equipments to support optical standards for line rates, coding schemes, bit-rate hierarchies, and OAM functionality as part of Performance Management.

 

While core optical network are more robust, the last mile and edge are turning towards becoming more flexible, provide Fast Provisioning, and enable to handle Redundancy while trying to preserve the legacy applications.

 

More and more users are looking forward to get better Service and Performance for what they pay for. Performance Management is very essential and critical in providing the demand for High Quality of Service (QoS).

 

2.    Introduction

 

Though today’s network are much more intelligent than the traditional, the development of Synchronous Optical NETwork has spurred the drive towards increased Performance Monitoring.

 

Synchronous transport signal level 1 (STS-1), which provides the framing for transmission of control information along with the customer traffic, is the most basic element of the SONET standards.

 

SONET has four optical interface layers. They are:

 

1.      Photonic Layer

2.      Section Layer

3.      Line Layer

4.      Path Layer

 

Photonic Layer

 

Photonic Layers main deals with the transportation of bits across the physical medium. Its main function is the conversion between STS signal and OC signals like:

 

v      Wavelength

v      Pulse Shaping

v      Power Levels

 

Section Layer

 

The Section layer deals with the transport of an STS-N frame across the physical medium. Its main functions are:

 

v      Framing

v      Scrambling

v      Error Monitoring

v      Section Maintenance

 

Line Layer

 

The line layer deals with the transport of the path layer payload and it overhead across the physical medium. Line Layer provides synchronization and performs multiplexing for the path layer. Its main functions are:

 

v      Protection Switching

v      Synchronization

v      Multiplexing

v      Line maintenance

v      Error Monitoring

 

Path Layer

 

The Path Layer deals with the transport of services between the PTE. The main function of the Path Layer is to map the signals into a format required by the line layer

 

v      Reads the payload

v      Interprets the payload

v      Modifies the path overhead for performance and automatic protection switching.

 

Performance Management deals with the Error Monitoring, Protection Switching at each of the Layers. Performance Monitoring in any network or Self-healing Networks are most often used to help the Service Providers to Manage the Network Equipment itself, thus safeguarding the data it is carrying.

 

While, each network that is installed, Service Provides must ensure that all the equipment are operational and functionally correct. However, they need to constantly keep tuning the network and test the performance as new customers keep adding up.

 

3.    What is Performance Monitoring?

 

Performance Management (hereafter called as PM) provides functions to evaluate and report upon the behavior of telecommunication equipment and the effectiveness of the network or network element. Its role is to gather and analyze statistical data for the purpose of monitoring and correcting the behavior and effectiveness of the network, NE’s or other equipment and to aid in planning, provisioning, maintenance and the measurement of quality. According to ITU M.3400, Performance management includes Performance Monitoring, Performance Control and Performance Analysis.

 

Performance Monitoring deals with the Overhead of SONET Frames. Each layer in the SONET signal provides alarm and error monitoring capabilities between various terminating points in the network. Similar to DS3 and DS1 signals, parity is calculated and stored in the transmitted signal. The parity is recalculated by the receiver and verified against the stored value to determine if an error occurred during transmission. Every layer in the SONET signal has its own Bit Interleaved Parity (BIP) calculation. The sidebar on the next page shows how BIP checks are performed in SONET. When an error is detected in a C-bit DS3 signal, a far-end block error (FEBE) is returned to the sender. SONET uses the same algorithm, using a layered approach. If an LTE receives some number of line BIP errors, it transmits the same number of line FEBE errors back to the originator. PTE use the same approach in the path layer of overhead.

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1: End-to-End SONET Connection

Managed Object Class is used to provide Performance Managed services. These are the objects for which the performance measurements are collected. To provide these services, following functions are required to be performed:

 

Data Collection Functions: This refers to the ability for the NE to collect various PM data related to a single monitored entity. This involves

 

1.      Assign PM Collection interval (15 Minutes, 24 hr)

2.      Suspend / Resume PM data collection

3.      Reset PM data

4.      Schedule PM data collection

 

Data Storage functions: This involves

 

1.      PM history duration

2.      Read PM data Storage

3.      Remove PM history data

 

Threshold functions: This involves

 

1.      Assign PM threshold

2.      Report PM threshold violation

 

Data reporting functions: This involves

 

1.      Request PM data

2.      Report PM data

3.      Allow / Inhibit PM data reports

4.      Screen PM data report

 

Monitored Object contains the measurement for the resource or NE being monitored for a specific time interval. These will also have a pointer to the Threshold data. If any thresholds are violated then an alarm notification is emitted.

 

Threshold Data Object is used for establishing thresholds. These contain a set of threshold values which correspond to a set of measurements defined for one or more classes of Current Data.

 

A typical architecture of various modules

 

Figure 2: PM Modules

Performance Management is done at various transmission layer namely the Section Layer, Line Layer and the Path Layer.

 

Section overhead


The section overhead informs the transport of the optical channel information between adjacent SONET equipment (at each end of a fiber). Services mapped to the section overhead include framing, channel trace, performance monitoring, voice, and an overlay Data Communications Channel (DCC). The section overhead fields are used as follows:

 

v      A1 and A2 delineate the actual physical STS-1 frames. The BellCore SONET transport specifications (GR-253) identify the criteria for monitoring the framing and accumulating defect statistics when framing failures occur.

 

v      J0/Z0 is also referred to as the trace/growth field and is used as a mechanism to positively identify the connection between two adjacent pieces of SONET equipment, and quickly identify and report mis-configured interconnects. The Z0 bytes are reserved to support future growth.

 

v      B1 is sent in the first STS-1 transmission. The B1 byte field contains parity information used to detect transmission errors. This field is used to accumulate performance-monitoring (PM) information that describes the behavior and reliability of the physical channel.

 

v      E1 carries local voice orderwire between various section-terminating equipment and is used by the operators during maintenance activities.

 

v      F1, the section user channel, terminates at all section equipment, and can be applied to special applications.

 

v      D1, D2 and D3 (DCC), when combined, provide a single 192-kbps channel to support the overlay communications network operations administration, maintenance, and provisioning (OAM&P) traffic. Depending on the equipment, the management protocols are likely to take one of two general forms: transaction language 1 (TL1) or telecommunications management networks (TMN).

Line overhead

The line overhead services concentrates on the alignment and delivery of information between terminals and add/drop multiplexing equipment. The fields involved in the line overhead include:

 

v      H1 and H2 STS payload pointer bytes are used to indicate the offset into the STS frame at which the SPE begins. They account for possible differences in the timing of the various interfaces on the network. In some cases, they are also used for the path alarm signal management (AIS-P).

 

v      H3 pointer action bytes can be used to carry an extra SPE byte, if there is a negative pointer action.

 

v      B2 line BIP-8, like the B1 byte, is used for line-error monitoring.

 

v      K1 and K2 are automatic protection switch (APS) channels used for applications where line level protection switching is employed. These fields control automatic fail-over algorithms. One of the important features provided by the K1 and K2 fields is that of alarm state signaling. The AIS-L and RDI-L signals can signal that a line defect of some sort has been detected, allowing downstream equipment to suppress alarm reports and aid in alarm correlation and fault isolation.

 

v      D4 through D12 line DCC fields support the transmission of OAM&P traffic at an aggregate data rate of 576 kbps, as in the case of the section DCC.

 

v      S1 is for synchronization status, contained in the first STS-1 of an STS-N. Bits 5 through 8 of S1 describe the synchronization status of the transmitting network element (NE).

 

v      Z1 represents growth and is reserved for future use.

 

v      M0 STS-1 line remote error indication (REI-L) is intended for only OC-1 rates. This field contains the error count detected by the transmitting line termination equipment (LTE).

 

v      M1, STS-N REI-L, is for higher rate signals (OC-3). The M1 field, in the third STS-1, in the STS-N, is used to support the REI-L function.

 

v      Z2 is for growth and is reserved.

 

v      E2 is for order-wire. It supports an express voice order-wire between LTE. Regenerators ignore it, as they have no active role in the line process.

 

This basic framework provides the information needed to support the interaction between standard SONET LTEs.

Path overhead

With the line and section services providing the mechanisms needed to frame and deliver the STS-1 frames, the SPE contains a combination of path overhead and payload traffic. The Path overhead fields are used as follows:

 

v      J1, or path trace, contains a repeating 64-byte message used to verify the distant end of a connection.

 

v      B3 STS path BIP-8 contains a parity calculation of the contents of the SPE, regardless of pointer adjustments. This is used to determine if any transmission errors have occurred over the path in question.

 

v      C2 path signal label indicates the actual content held within the SPE, including the payload status.

 

v      G1, path status, provides an end-to-end monitoring service that can include an accumulated count of the number of detected errors.

 

v      F2, path user channel, is used for user applications between path end-points.

 

v      H4, virtual tributary (VT) multi-frame indicator, provides control information to describe the structure of the payload traffic.

 

Transport Overhead

Framing

A1

Framing

A2

Trace/growth (STS-ID)
J0/Z0

Section Overhead

BIP-8

B1 / Undefined

Order-wire

E1 / Undefined

User

F1 / Undefined

 

Data Communication

D1 / Undefined

Data Communication

D2 / Undefined

Data Communication

D3 / Undefined

 

Pointer

H1

Pointer

H2

Pointer Action

H3

 

BIP-9

B2

APS

K1 / Undefined

APS

K2 / Undefined

Line Overhead

Data Communication

D4 / Undefined

Data Communication

D4 / Undefined

Data Communication

D4 / Undefined

 

Data Communication

D4 / Undefined

Data Communication

D4 / Undefined

Data Communication

D4 / Undefined

 

Data Communication

D4 / Undefined

Data Communication

D4 / Undefined

Data Communication

D4 / Undefined

 

Sync Status / Growth

S1 / Z1

REI-L / Growth

M0 or M1 / Z2

Order-wire

E2 / Undefined

 

Trace
J1

BIP-8
B3

Signal label
C2

Path status
G1

User channel
F2

Indicator
H4

Growth
Z3

Growth
Z4

Tandem connection
Z5

 

4.    Measurements

 

Performance monitoring is the process of continuous collection, analysis and reporting of performance data. Performance parameters are normally gathered under in service and non-failure condition.

 

Performance parameters are derived by the processing (Counting) of the performance primitives. Primitives are basically Defects, Anomalies and Failures. Performance parameters are accumulated over 15 minute and one day accumulation period.

 

The various parameters to be measured at different layers are given below. All the Parameters related to Section Layer and Line Layer (near-end and far-end) are measured for STS-3 objects. STS Path Layer (near-end and far-end) should be measured for only VC3 current data objects. VT Path Layer (near-end and far-end) parameters should be measured for VC11. Measurements for DS3 object (Normal and C bit Parity mode) are derived from the specification of TMC chip.

Section Layer Parameters (for STS-3 only)

The following Section Layer PM parameters are defined in SONET. At the same time, NO far-end parameters are defined for the SONET Section Layer.

1.      Section Code Violations (CV-S): CV-S is the basic parameter that will be indicated from HW. The CV-S parameter is a count of BIP-8 errors (B1 byte) detected at the Section layer. Up to 8 BIP errors can be detected per STS-3 frame, with each error incrementing the CV-S counter.

 

2.      Background Block Error (BBE-S): BBE-S is the count of STS-3 section blocks for which the number of BIP-8 error ³ 1. BBE-S is calculated using BIP-8 error in the B1 byte.

 

3.      Section Errored Seconds (ES-S): An Errored Second is one second period with one or more Section layer BIP error was detected or an SEF or LOS defect was present.

 

4.      Section Errored Seconds Type A (ESA-S): ESA-S is the count of 1 second intervals containing 1 BIP error (B1 byte), and no SEF or LOS defects.

 

5.      Section Errored Seconds Type B (ESB-S): ESB-S is the count of 1 second intervals containing more than 1 but less than 2500 BIP errors (B1 byte), and no SEF or LOS defects.

 

6.      Section Severely Errored Seconds (SES-S): An SES is a one second period which contains 2500 or more BIP errors or an SEF or LOS defect was present.

 

7.      Section Severely Errored Framing Seconds (SEFS-S): The SEFS-S parameter is a count of seconds during which an SEF defect was present.

 

8.      Loss of Signal Seconds (LOSS-S): LOSS-S is a count of 1 second intervals containing one or more LOS defects.

 

The following Table shows the various parameters.

 

PM Parameters

Anomalies

Parameters

Code Violation

Count of BIP-8 errors

(B1 byte)

CV-S

Background Block Error

Count of blocks with BIP-8 errors ³ 1

(B1 byte)

BBE-S

Errored Seconds

B1 OR SEF OR LOS

ES-S

Errored Seconds - Type A

B1 = 1 AND SEF = 0 AND LOS = 0

ESA-S

Errored Seconds - Type B

2 £ B1 < 2500 AND

SEF = 0 AND LOS = 0

ESB-S

Severely Errored Seconds

B1 ³ 2500 OR SEF OR LOS

SES-S

Severely Errored Framing Seconds

SEF

SEFS-S

Loss of Signal Seconds

LOS ³ 1

LOSS-S

Table 1: Section Layer PM Parameters

Line Layer Parameters (for STS-3 only)

For Line Layer, the parameters are defined for near-end and far-end.

Near-end Line Layer Parameters

The near-end Line layer parameters defined in SONET are:

 

1.      Near-end Line Code Violations (CV-L): CV-L parameter is the count of BIP errors (B2 byte) detected at the Line layer. Up to 8*N (N=3 in case of STS3) BIP errors can be detected per STS-3 frame, with each error incrementing the CV-L counter.

 

2.      Near-end Line Background Block Error (BBE-L): BBE-L is a count of STS-1 line block errors. BBE-L is equivalent to CV-L only in the Line layer.

 

3.      Near-end Line Errored Seconds (ES-L): An Errored Second is one second period with one or more Line layer BIP error was detected or AIS-L defect was present.

 

4.      Near-end Line Errored Seconds Type A (ESA-L): ESA-L is the count of 1 second intervals containing 1 BIP error (B2 byte), and no AIS defects.

 

5.      Near-end Line Errored Seconds Type B (ESB-L): ESB-L is the count of 1 second intervals containing more than 1 but less than 2500 BIP errors (B2 byte), and no AIS defects.

 

6.      Near-end Line Severely Errored Seconds (SES-L): An SES-L is a one second period which contains 2500 or more BIP errors or an AIS-L defect was present.

 

7.      Near-end Line Unavailable Seconds (UAS-L): The UAS-L parameter is a count of the seconds during which the Line was considered unavailable. A Line becomes unavailable at the onset of 10 consecutive seconds that qualify as SES-Ls and continues to be unavailable until the onset of 10 consecutive seconds that do not qualify as SES-Ls. Refer section Error! Reference source not found. for more details about UAS.

 

8.      Near-end Line Failure Counts (FC-L): The FC-L parameter is a count of the number of near-end line failure events. A failure event begins when the AIS-L failure is declared, and ends when the AIS-L failure is cleared. A failure event that begins in one period and ends in another period is counted only in the period in which it begins. Refer section Error! Reference source not found. for more details about AIS.

 

9.      Protection Switching Counts (PSC): This is applicable only is Line Level Protection Switching is used. For a working line, the PSC is a count of the number of times that service has been switched from the monitored line to the protection line, plus the number of times it has been switched back to the working line. For a protection line, the count of number of switching from any working line to the protection line, plus the number of times the service has been switched back to the working line.

 

10.  Protection Switching Duration (PSD): For a working line, the PSD parameter is a count of the seconds that service was being carried on the protection line. For the protection line, it is a count of the seconds that the line was being used to carry service. The PSD parameter is only applicable, if revertive line level protection switching is used.

 

11.  STS Pointer Justifications (STS PJ): The STS PJ parameter is accumulated for a non-terminated STS path. It is defined to be a count of the STS pointer adjustments created or absorbed by an NE. If an incoming pointer adjustment does not directly cause an outgoing pointer adjustment, or if an outgoing pointer adjustment is not directly caused by an incoming pointer adjustment, then the STS PJ current second register is incremented by 1. Otherwise, the STS PJ count is not incremented. Certain number of STS PJs is expected during normal operations, however excessive STS PJs may indicate a synchronization problem.

 

12.  Alarm Indication Signal Second (AISS-L): AISS-L is the count of 1 second intervals containing one or more AIS defects.

Far-end Line Layer Parameters

Far-end Line layer performance is conveyed back to the near-end LTE via the K2 byte (RDI-L) and the M0 or M1 byte (REI-L). The far-end Line layer parameters defined in SONET are:

 

1.      Far-end Line Code Violations (CV-LFE): CV-LFE parameter is the count of BIP errors detected by the far-end LTE and reported back to the near-end LTE, using REI-L indication in the line overhead. Up to 8*N  (N=3 in case of STS-3) BIP errors can be detected per STS-3 frame using REI-L.

 

2.      Far-end Line Background Block Error (BBE-LFE): BBE-LFE is a count of STS-1 line block errors. BBE-LFE is equivalent to CV-LFE only in the Line layer.

 

3.      Far-end Line Errored Seconds (ES-LFE): The ES-LFE is a count of the seconds during which at least one line BIP error was reported by the far-end LTE (using REI-L indication) or an RDI-L defect was present.

 

4.      Far-end Line Errored Seconds Type-A (ESA-LFE): ESA-LFE is the count of 1 second intervals containing 1 REI-L error and no RDI-L defects.

 

5.      Far-end Line Errored Seconds Type-B (ESB-LFE): ESB-LFE is the count of 1 second intervals containing more than 1 but less than 2500 REI-L errors and no RDI-L defects.

 

6.      Far-end Line Severely Errored Seconds (SES-LFE): An SES-LFE is a one second period which contain 2500Error! Bookmark not defined. or more BIP errors where reported by the far-end LTE or an RDI-L defect was present.

 

7.      Far-end Line Unavailable Seconds (UAS-LFE): The UAS-LFE parameter is a count of the seconds during which the Line is considered unavailable at the far-end. A Line becomes unavailable at the far-end at the onset of 10 consecutive seconds that qualify as SES-LFEs and continues to be unavailable until the onset of 10 consecutive seconds that do not qualify as SES-LFEs. Refer section Error! Reference source not found. for more details about UAS.

 

8.      Far-end Line Failure Counts (FC-LFE): The FC-LFE parameter is a count of the number of far-end line failure events. A failure event begins when the RFI-L failure is declared, and ends when the RFI-L failure is cleared. A failure event that begins in one period and ends in another period is counted only in the period in which it begins. Refer section Error! Reference source not found. for more details about RFI.

 

9.      Far-end Alarm Indication Signal Second (AISS-LFE): AISS-LFE is the count of 1 second intervals containing one or more RDI-L defects.

 

The following Table shows the various parameters for near-end and far-end.

 

PM

Parameters

Near-End Defect

Near-End Parameters

Far-End Defect

Far-End Parameters

Code Violation

Count of BIP-8 errors

(B2 byte)

CV-L

REI-L

(M0 byte)

CV-LFE

Background Block Error

Count of blocks with BIP-8

BBE-L

REI-L

(M0 byte)

BBE-LFE

Errored Seconds

B2 OR AIS-L

ES-L

REI-L OR RDI-L

ES-LFE

Errored Seconds - Type A

B2 = 1 AND AIS = 0

ESA-L

REI-L = 1 AND RDI-L = 0

ESA-LFE

Errored Seconds - Type B

2 £ B2 < 2500 AND

AIS-L = 0

ESB-L

2 £ REI-L < 2500 AND

RDI-L = 0

ESB-LFE

Severely Errored Seconds

B2 ³ 2500 OR AIS-L

SES-L

BIP errors ³ 2500 or RDI-L

SES-LFE

Unavailable Seconds

10 consecutive SES-L

UAS-L

10 consecutive SES-LFE

UAS-LFE

Failure Counts

AIS-L

FC-L

RFI-L

FC-LFE

Protection Switching Counts

 

PSC

---

---

Protection Switching Duration

 

PSD

---

---

STS Pointer Justifications

 

STS PJ

---

---

Alarm Indication Signal Second

AIS-L ³ 1

AISS-L

RDI ³ 1

AISS-LFE

Table 2: Line Layer PM Parameters

STS Path Layer Parameters (for VC3 only)

For STS Path Layer, the parameters are defined for near-end and far-end.

Near-end STS Path Layer Parameters

The near-end STS Path layer parameters defined in SONET are:

 

1.      Near-end STS Path Code Violations (CV-P): CV-P parameter is the count of BIP errors (B3 byte) detected at the STS Path layer. Up to 8 BIP errors can be detected per STS-3 frame, with each error incrementing the CV-P current second register.

 

2.      Near-end STS Path Background Block Error (BBE-P): BBE-P is a count of STS Path block errors for which the number of BIP-8 errors ³ 1, using B3 byte located in the STS Path overhead.

 

3.      Near-end STS Path Errored Seconds (ES-P): The ES-P is one second period with at least one STS Path layer BIP error was detected or an AIS-P or LOP-P defect was present.

 

4.      Near-end STS Path Errored Seconds Type-A (ESA-P): ESA-P is the count of 1 second intervals containing 1 BIP error (B3 byte), and no AIS-P and LOP-P defects.

 

5.      Near-end STS Path Errored Seconds Type B (ESB-P): ESB-P is the count of 1 second intervals containing more than 1 but less than 2400 BIP errors (B3 byte), and no AIS-P or LOP-P defects.

 

6.      Near-end STS Path Severely Errored Seconds (SES-P): An SES-P is a one second period which contain 2400 or more BIP errors were detected or an AIS-P or LOP-P defect was present.

 

7.      Near-end STS Path Unavailable Seconds (UAS-P): The UAS-P parameter is a count of the seconds during which the STS Path was considered unavailable. An STS Path becomes unavailable at the onset of 10 consecutive seconds that qualify as SES-Ps and continues to be unavailable until the onset of 10 consecutive seconds that do not qualify as SES-Ps. Refer section Error! Reference source not found. for more details about UAS.

 

8.      Near-end STS Path Failure Counts (FC-P): The FC-P parameter is a count of the number of near-end STS Path failure events. A failure event begins when the AIS-P or LOP-P failure is declared, and ends when these failures are cleared. A failure event that begins in one period and ends in another period is counted only in the period in which it begins.

 

9.      VT Pointer Justifications (VT PJ): The VT PJ parameter is accumulated for a non-terminated VT path. It is defined to be a count of the VT pointer adjustments created or absorbed by an NE. If an incoming pointer adjustment does not directly cause an outgoing pointer adjustment, or if an outgoing pointer adjustment is not directly caused by an incoming pointer adjustment, then the VT PJ current second register is incremented by 1. Otherwise, the VT PJ count is not incremented. Certain number of VT PJs is expected during normal operations, however excessive VT PJs may indicate a synchronization problem.

Far-end STS Path Layer Parameters

Far-end STS Path layer performance is conveyed back to the near-end STS Path via bits 1 through 4 (REI-P) and 5 through 7 (RDI-P) of the G1 byte. The far-end STS Path layer parameters defined in SONET are:

 

1.      Far-end STS Path Code Violations (CV-PFE): CV-PFE parameter is the count of BIP errors detected by the far-end STS PTE and reported back to the near-end STS PTE, using REI-P indication in the STS path overhead. Up to 8 BIP errors can be detected per STS-3 frame using REI-P.

 

2.      Far-end STS Path Background Block Error (BBE-PFE): BBE-PFE is a count of STS Path block errors for which the number of REI-P errors ³ 1, using G1 byte located in the STS Path overhead.

 

3.      Far-end STS Path Errored Seconds (ES-PFE): The ES-PFE is a count of the seconds during which at least one STS path BIP error was reported by the far-end STS PTE (using REI-P indication), a one bit RDI-P defect was present or (if enhanced RDI-P is supported) an RDI-P server defect was present.

 

4.      Far-end STS Path Errored Seconds Type A (ESA-PFE): ESA-PFE is the count of 1 second intervals containing 1 REI-P error (G1 byte), and no RDI-P defects.

 

5.      Far-end STS Path Errored Seconds Type B (ESB-PFE): ESB-PFE is the count of 1 second intervals containing more than 1 but less than 2400 REI-P (G1 byte), and no RDI-P defects.

 

6.      Far-end STS Path Severely Errored Seconds (SES-PFE): An SES-PFE is a one second period which contains 2400 or more BIP errors where reported by the far-end STS PTE, or a one bit RDI-P defect was present or an RDI-P server defect was present.

 

7.      Far-end STS Path Unavailable Seconds (UAS-PFE): The UAS-PFE parameter is a count of the seconds during which the STS Path is considered unavailable at the far-end. An STS Path becomes unavailable at the far-end at the onset of 10 consecutive seconds that qualify as SES-PFEs and continues to be unavailable until the onset of 10 consecutive seconds that do not qualify as SES-PFEs. Refer section Error! Reference source not found. for more details about UAS.

 

8.      Far-end STS Path Failure Counts (FC-PFE): The FC-PFE parameter is a count of the number of far-end STS path failure events. A failure event begins when the RFI-P failure is declared, and ends when the RFI-P failure is cleared. A failure event that begins in one period and ends in another period is counted only in the period in which it begins. Refer section Error! Reference source not found. for more details about RFI.

 

The following Table shows the various parameters for near-end and far-end.

 

PM

Parameters

Near-End Defect

Near-End Parameters

Far-End Defect

Far-End Parameters

Code Violation

B3

CV-P

REI-P

CV-PFE

Background Block Error

Count of blocks with BIP-8 ³ 1

(B3 byte)

BBE-P

REI-P ³ 1

(G1 byte)

BBE-PFE

Errored Seconds

B3 OR AIS-P OR LOP-P

ES-P

REI-P OR RDI-P

ES-PFE

Errored Seconds - Type A

B3 = 1 AND

AIS-P = 0 AND

LOP-P = 0

ESA-P

REI-P = 1 AND

RDI-P = 0

ESA-PFE

Errored Seconds - Type B

2 £ B3 < 2400 AND

AIS-P = 0 AND

LOP-P =0

ESB-P

2 £ REI-P < 2400

AND

RDI-P = 0

ESB-PFE

Severely Errored Seconds

B3 ³ 2400 OR

AIS-P ³ 1 OR

LOP-P ³ 1

SES-P

REI-P ³ 2400 OR

RDI-P ³ 1

SES-PFE

Unavailable Seconds

10 consecutive SES-P

UAS-P

10 consecutive SES-PFE

UAS-PFE

Failure Counts

AIS-P or LOP-P

FC-P

RFI-P

FC-PFE

VT Pointer Justifications

TBC

VT PJ

---

---

Table 3: STS Path Layer PM Parameters

VT Path Layer Parameters (for VC11 only)

For VT Path Layer, the parameters are defined for near-end and far-end.

Near-end VT Path Layer Parameters

The near-end VT Path layer parameters defined in SONET are:

 

1.      Near-end VT Path Code Violations (CV-V): CV-V parameter is the count of BIP errors (using bits 1 and 2 of the V5 byte in the incoming VT Path overhead) detected at the VT Path layer. Up to 2 BIP errors can be detected per VT super frame, with each error incrementing the CV-V current second register.

 

2.      Near-end VT Path Background Block Error (BBE-V): BBE-V is a count of VT Path block errors for which the number of BIP-2 errors ³ 1, using V5 overhead byte of the floating VT.

 

3.      Near-end VT Path Errored Seconds (ES-V): The ES-V is one second period with at least one VT Path layer BIP error was detected or an AIS-V or LOP-V defect was present.

 

4.      Near-end VT Path Errored Seconds Type-A (ESA-V): ESA-V is the count of 1 second intervals containing 1 BIP error (V5 byte), and no AIS-V and LOP-V defects.

 

5.      Near-end VT Path Errored Seconds Type-B (ESB-V): ESB-V is the count of 1 second intervals containing more than 1 but less than 600 BIP errors (V5 byte), and no AIS-V or LOP-V defects.

 

6.      Near-end VT Path Severely Errored Seconds (SES-V): An SES-V is a one second period which contain 600 or more BIP errors were detected or an AIS-V or LOP-V defect was present.

 

7.      Near-end VT Path Unavailable Seconds (UAS-V): The UAS-V parameter is a count of the seconds during which the VT Path was considered unavailable. A VT Path becomes unavailable at the onset of 10 consecutive seconds that qualify as SES-Vs and continues to be unavailable until the onset of 10 consecutive seconds that do not qualify as SES-Vs.

 

8.      Near-end VT Path Failure Counts (FC-V): The FC-V parameter is a count of the number of near-end VT Path failure events. A failure event begins when the AIS-V or LOP-V failure is declared, and ends when these failures are cleared. A failure event that begins in one period and ends in another period is counted only in the period in which it begins.

Far-end VT Path Layer Parameters

Far-end VT Path layer performance is conveyed back to the near-end VT PTE via bit 3 of the V5 byte (REI-V) and either bits 5 through 7 of the Z7 byte or bit 8 of the V5 byte (RDI-V). The far-end VT Path layer parameters defined in SONET are:

 

1.      Far-end VT Path Code Violations (CV-VFE): CV-VFE parameter is the count of BIP errors detected by the far-end VT PTE and reported back to the near-end VT PTE, using REI-V indication in the VT Path overhead. Note that only one BIP error can be detected per VT super frame using REI-V.

 

2.      Far-end VT Path Background Block Error (BBE-VFE): BBE-VFE is a count of VT Path block errors for which the number of REI-V errors ³ 1, using V5 byte.

 

3.      Far-end VT Path Errored Seconds (ES-VFE): The ES-VFE is a count of the seconds during which at least one VT Path BIP error was reported by the far-end VT PTE (using REI-V indication), a one bit RDI-V defect was present or an RDI-V server defect was present.

 

4.      Far-end VT Path Errored Seconds Type-A (ESA-VFE): ESA-VFE is the count of 1 second intervals containing 1 REI-V error (V5 byte), and no RDI-V defects.

 

5.      Far-end VT Path Errored Seconds Type-B (ESB-VFE): ESB-VFE is the count of 1 second intervals containing more than 1 but less than 600 REI-V errors (V5 byte), and no RDI-V defects.

 

6.      Far-end VT Path Severely Errored Seconds (SES-VFE): An SES-VFE is a one second period which contains 600Error! Bookmark not defined. or more BIP errors where reported by the far-end VT PTE, a one bit RDI-V defect was present or an RDI-V server defect was present.

 

7.      Far-end VT Path Unavailable Seconds (UAS-VFE): The UAS-VFE parameter is a count of the seconds during which the VT Path is considered unavailable at the far-end. A VT Path becomes unavailable at the far-end at the onset of 10 consecutive seconds that qualify as SES-VFEs and continues to be unavailable until the onset of 10 consecutive seconds that do not qualify as SES-VFEs. Refer section Error! Reference source not found. for more details about UAS.

 

8.      Far-end VT Path Failure Counts (FC-VFE): The FC-VFE parameter is a count of the number of far-end VT Path failure events. A failure event begins when the RFI-V failure is declared, and ends when the RFI-V failure is cleared. A failure event that begins in one period and ends in another period is counted only in the period in which it begins. Refer section Error! Reference source not found. for more details about RFI.

 

The following Table shows the various parameters for near-end and far-end.

 

PM

Parameters

Near-End Defect

Near-End Parameters

Far-End Defect

Far-End Parameters

Code Violation

V5

CV-V

REI-V

CV-VFE

Background Block Error

Count of blocks with BIP-2 ³ 1 (V5 byte)

BBE-V

REI-V ³ 1

BBE-VFE

Errored Seconds

V5 OR AIS-V OR LOP-V

ES-V

REI-V OR RDI-V

ES-VFE

Errored Seconds - Type A

V5 = 1 AND

AIS-V = 0 AND

LOP-V = 0

ESA-V

REI-V = 1 AND

RDI-V = 0

ESA-VFE

Errored Seconds - Type B

2 £ V5 < 600

 AND

AIS-V = 0 AND

LOP-V =0

ESB-V

2 £ REI-V < 600

AND

RDI-V = 0

ESB-VFE

Severely Errored Seconds

V5 ³ 600 or AIS-V or LOP-V

SES-V

BIP errors ³ 600 or RDI-V

SES-VFE

Unavailable Seconds

10 consecutive SES-V

UAS-V

10 consecutive SES-VFE

UAS-VFE

Failure Counts

AIS-V or LOP-V

FC-V

RFI-V

FC-VFE

Table 4: VT Path Layer PM Parameters

DS3 Parameters

For DS3, the parameters are defined for near-end and far-end according to the specification of TMC chip. M13 mapping has 2 modes, one is Normal mode and the other is C bit Parity mode. For each mode, the parameters are defined separately. These modes can be set by the operator while creating the Configuration Object corresponding to the CDO. To change the M13 mapping mode, the operator should delete the existing Configuration Object and create newly with the desired mode.

Near-end DS3 Parameters

Normal Mode

The near-end DS3 parameters for Normal Mode, defined in SONET are:

 

1.      Near-end Code Violations (CVP-P): CVP-P parameter is the count of P bit parity errors. P bit parity error occurs when the received two P bits doesn’t match the locally calculated parity.

 

2.      Near-end Errored Second (ESP-P): ESP-P is the count of one second interval of P bit parity errors or one or more SEF defects or one or more AIS defects.

 

3.      Near-end Errored Second Type-A (ESAP-P): ESAP-P is the count of one second interval containing one P bit parity error and no AIS or SEF defects.

 

4.      Near-end Errored Second Type-B (ESBP-P): ESBP-P is the count of one second interval containing more than one and less than 45 P bit parity errors and no AIS or SEF defects.

 

5.      Near-end Severely Errored Second (SESP-P): SESP-P is the count of one second interval containing more than 45 P bit parity errors or one or more SEF defects or one or more AIS defects.

 

6.      Near-end SEF/ AIS Second (SASP-P): SASP-P is the count of one second interval containing one or more SEF or one or more AIS defects.

 

7.      Near-end AIS Second (AISSP-P): AISSP-P is the count of one second interval containing one or more AIS defects.

 

8.      Near-end Unavailable Second (UASP-P): UASP-P is the count of 10 contiguous SESP-Ps.

C bit Parity Mode

The near-end DS3 parameters for C bit Parity Mode, defined in SONET are:

 

1.      Near-end Code Violations (CVCP-P): CVCP-P parameter is the count of CP bit parity errors. CP bit parity error occurs when majority voting of the CP bits doesn’t match the calculated parity.

 

2.      Near-end Errored Second (ESCP-P): ESCP-P is the count of one second interval of CP bit parity errors or one or more SEF defects or one or more AIS defects.

 

3.      Near-end Errored Second Type-A (ESACP-P): ESACP-P is the count of one second interval containing one CP bit parity error and no AIS or SEF defects.

 

4.      Near-end Errored Second Type-B (ESBCP-P): ESBCP-P is the count of one second interval containing more than one and less than 45 CP bit parity errors and no AIS or SEF defects.

 

5.      Near-end Severely Errored Second (SESCP-P): SESCP-P is the count of one second interval containing more than 45 CP bit parity errors or one or more SEF defects or one or more AIS defects.

 

6.      Near-end SEF/AIS Second (SASCP-P): SASCP-P is the count of one second interval containing one or more SEF or one or more AIS defects.

 

7.      Near-end AIS Second (AISSCP-P): AISSCP-P is the count of one second interval containing one or more AIS defects.

 

8.      Near-end Unavailable Second (UASCP-P): UASCP-P is the count of 10 contiguous SESCP-Ps.

Far-end DS3 Parameters

Normal Mode

No far-end DS3 parameters for Normal Mode are defined.

C bit Parity Mode

The far-end DS3 parameters for C bit Parity Mode, defined in SONET are:

 

1.      Far-end Code Violations (CVCP-PFE): CVCP-PFE parameter is the count of 3 FEBE (far-end block error) bits in M-frame. FEBE is not ‘all 1’ pattern received on the C bits.

 

2.      Far-end Errored Second (ESCP-PFE): ESCP-PFE is the count of one second interval of three FEBE bits in M-frame.

 

3.      Far-end Errored Second Type-A (ESACP-PFE): ESACP-PFE is the count of one second interval containing three FEBE bits in M-frame and no far-end AIS defects or SEF defects.

 

4.      Far-end Errored Second Type-B (ESBCP-PFE): ESBCP-PFE is the count of one second interval containing more than one and less than 45 three FEBE bits in M-frame and no far-end AIS or SEF defects.

 

5.      Far-end Severely Errored Second (SESCP-PFE): SESCP-PFE is the count of one second interval containing more than 45 three FEBE bits in M-frame or one or more SEF defects or one or more AIS defects.

 

6.      Far-end SEF/AIS Second (SASCP-PFE): SASCP-PFE is the count of one second interval containing one or more SEF or one or more AIS defects.

 

7.      Far-end Unavailable Second (UASCP-PFE): UASCP-PFE is the count of 10 contiguous SESCP-PFEs.

 

PM

Parameters

Near-End Defect

Near-End Parameters

Far-End Defect

Far-End Parameters

Normal Mode

Code Violation

P bit

CVP-P

---

---

Errored Seconds

P bit OR

SEF ³ 1 OR AIS ³ 1

ESP-P

---

---

Errored Seconds - Type A

1 P bit AND

 SEF = 0 AND AIS = 0

ESAP-P

---

---

Errored Seconds - Type B

1 < P bit < 45 AND SEF = 0 AND AIS = 0

ESBP-P

---

---

Severely Errored Second

P bit ³ 45 OR SEF ³ 1 OR AIS ³ 1

SESP-P

---

---

SEF/ AIS Second

SEF ³ 1 OR AIS ³ 1

SASP-P

---

---

AIS Second

AIS ³ 1

AISSP-P

---

---

Unavailable Second

10 consecutive SESP-P

UASP-P

---

---

C bit Parity Mode

Code Violation

CP bit

CVCP-P

Count of 3 FEBE bits

CVCP-PFE

Errored Seconds

CP bit OR

SEF ³ 1 OR AIS ³ 1

ESCP-P

3 FEBE bits

ESCP-PFE

Errored Seconds - Type A

1 CP bit AND

 SEF = 0 AND AIS = 0

ESACP-P

3 FEBE bits AND AIS = 0 AND

SEF = 0

ESACP-PFE

Errored Seconds - Type B

1 < CP bit < 45 AND

SEF = 0 AND AIS = 0

ESBCP-P

1 < 3 FEBE bits < 45 AND AIS = 0 AND

SEF = 0

ESBCP-PFE

Severely Errored Second

CP bit ³ 45 OR SEF ³ 1 OR AIS ³ 1

SESCP-P

3 FEBE bits ³ 45 OR

AIS ³ 1 OR SEF ³ 1

SESCP-PFE

SEF/ AIS Second

SEF ³ 1 OR AIS ³ 1

SASCP-P

SEF ³ 1 OR AIS ³ 1

SASCP-PFE

AIS Second

AIS ³ 1

AISSCP-P

---

---

Unavailable Second

10 consecutive SESCP-P

UASCP-P

10 consecutive SESCP-PFE

UASCP-PFE

Table 5: DS3 PM Parameters

 

5.    Standards

 

In 1985, BellCore proposed the idea of an optical carrier-to-carrier interface that would allow the inter-connection of different manufacturers’ optical equipment. This was based on a hierarchy of digital rates, all formed by the interleaving of a basic rate signal. The idea of a SONET attracted the interest of carriers, Regional Bell Operating Companies (RBOC), and manufacturers alike and quickly gained momentum. Interest in SONET by CCITT (now International Telecommunication Union – ITU-T) expanded its scope from a domestic to an international standard, and by 1988 the ANSI committee had successfully integrated changes requested by the ITU-T, and were well on their way toward the issuance of the new standard. Today, the SONET standard is contained in the ANSI specification T1.105 Digital Hierarchy – Optical Interface Rates & Formats Specifications recommendations are found in Data Interface (FDDI), in addition to existing DS3 and DS1 services. Another major advantage of SONET is that the operations, administration, maintenance, and provisioning (OAM&P) capabilities are built directly into the signal overhead to allow maintenance of the network from one central location.

 

Standards Bodies

 

 

6.    Conclusion

 

SONET/SDH is here to stay for long time.  It is an international standard that is being widely adopted.  SONET/SDH can transport all signals currently defined and that’s why it’s very important and has been selected as Transmission Technology for B-ISDN.

 

The definition and implementation of performance monitoring was part of the original concept behind SONET and ATM standards. One of the basis and fundamental reason to develop Performance Monitoring was to enable quick detection of Equipment Failures. Performance monitoring has fulfilled its many promises, and earlier protocols such as DS-1 and DS-3 have evolved to include many testing capabilities. Each of these has some overhead available for the detection of errors and the reporting of upstream alarms.

 

7.    References

 

1.      ITU M.3400 TMN Management Functions

2.      ITU Q.822 Performance Management

3.      GR-253-CORE Issue 2, December 1995 - SONET Transport Systems Common Generic Criteria

4.      ANSI T1.231 - Digital Hierarchy  Layer 1 - Digital Transmission Performance Monitoring

 

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