Acterna FST-2310 ATM Testing Application Note

8/6/2019 Acterna FST-2310 ATM Testing Application Note

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ATM Testing Application Note

Acterna FST-2310


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Over the pastfew years, there has been

an explosion in the growth of Internet

usage. As more users gain accessto

high-speed connections and more

applications requiring large amounts

of bandwidth are developed, the

demand for fast, reliable communica-

tionsbetween end users increases. The

rapid deployment of Intranets,

Extranets, and Virtual Private Networks

(VPNs) isalso driving demand for com-

munications technologies to connect

multiple users in different geographi-

calareas.

AsynchronousTransfer Mode (ATM)

was developed to answer the need for

increased bandwidth, seamless inter-networking, and a common formatfor

services with different bandwidth

requirements. ATM is a method of for-

matting, switching, and multiplexing

information using fixed-length cells.

Thistechnology allows for the simulta-

neous transmission of voice, video,

and data over the same network.

Because itgrew from Broadband Inte-

grated Services Data Network(B-ISDN)

standards, ATM operates on existing

transport technologies worldwide. It is

currently an international standard

administered bythe ITU, ANSI, and the

ATM Forum.

OVERVIEW

2

Traditionalcommunication networks

(Figure 1) dedicate separate technolo-

giesand systemsto each application.

Frame relay, used for data communica-

tions, requires specific frame relay

switching equipment. Traditional voice

networks use one type ofswitch, while

video networks typically require other

typesof equipment. In traditionalnet-

works, installing, provisioning,

maintaining, and interconnecting mul-

tiple networks is both complex and

costly.

An ATM network, on the other hand,

hasmanyadvantagesover other tech-

nologies because it combinesall types

of traffic and applications into a singlenetwork (Figure 2). ATM makes it possi-

ble for LANs and WANsto use a

common technology with minimal

adjustmentswhen changesor

improvements are needed. ATM traffic

is scaleable to higher speeds and can

operate over a DS1, DS3, or high-speed

SONET backbone without modifying

the cellformat. Because ATM is asyn-

chronous, voice, video, and data

applications can run simultaneously.

Combining applications allows the net-

workto allocate bandwidth on-demand

for greater efficiency.


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Router RouterFrame Relay

T-Carrier SONET NetworkMux Mux

ISDN PRI Line

Video Conferencing Video Conferencing

ATM/LAN

Router

ATM/LAN

Router

Video Conferencing Video Conferencing

Mux

LAN LAN

ATM ATM

ATM

ATM ATMATM Network IAD

gure 1. Traditional networksuse differenttechnologiesfor each application.

gure 2. The ATM network combinestechnologies.


4/224

ATM FUNDAMENTALS

ATM Cell StructureAn ATM networkconvertsa bit stream

of data (voice and video are also con-sidered data) into discrete cellsfor

transmission, and then itreassembles

the data into itsoriginal form when it

reaches its destination. ATM cells are

based on a fixed-length, 53-byte cell.

An ATM cell followsa route to its desti-

nation that is mapped by the ATM

switchesit passes through.

Two cell structures are used in an ATM

network, including the User Network

Interface (UNI) and the Network to

Node Interface (NNI). UNI cellstrans-

port data between the customer

premises equipment and an ATM net-

workswitch. NNI cellscarry data

between ATM switches within a net-

work. The firstfive bytesof both types

of ATM cell structurescontain address,

error checking, and control informa-

tion. These five bytesare referred to as

header space. The remaining 48 bytes

are allocated to the customers pay-load, which can be voice, video, or data

signals. The structure of a UNI cell is

illustrated in Figure 3, and the purpose

of each field in the header is identified.

8 7 6 5 4 3 2 1

1

2

3

4

5

6

5 3

G F C V P I

V P I

V C I P T C L P

V C I

V C I

H E C

Information

Payload

(48 bytes)

ATM UNI Cell

Notes: GFC: Generic Flow Control

VPI: Virtual Path Identifer

VCI: Virtual Channel Identifer

PT: Payload Type

CLP: Cell Loss Priority

HEC: Header Error Control

Byte

Figure 3. The ATM UNI cell.


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Elements of an ATM UNI CellGenericFlow Control

As of the time of thisprinting, stan-dards are being developed for the

Generic Flow Control (GFC) field. The

GFCfield isused to prioritize and con-

trol traffic flow when multiple devices

share a common access.

VirtualPath Identifier and Virtual

ChannelIdentifier

The VirtualPath Identifier (VPI) and Vir-

tualChannel Identifier (VCI) fields

identify specific cell addresses thatwill

be used for cell switching. The VPI and

VCI structure within the carrier signal is

shown in Figure 4. The carrier signal is

the physicaltransport signal (SONET,

DS3, or DS1) used to transportATM

cells between Network Elements (NEs).

An ATM cell mayhave several different

VPI/VCI addressesas it is transported

through a network since each ATM

switch can assign a new addressto the

cellas it passes through the switch.

Thisnew address is significantto thatspecific ATM switch. Therefore, the ATM

celladdressdoesnot necessarily indi-

cate the source or destination of the

data.

Carrier signal

Virtual path

Carrier channel

Figure 4. The carriersignal containing virtual

paths and virtual channels.

Payload Type Identifier

The Payload Type Identifier (PTI) indi-cateswhether the cell payload

contains user data cellsor Operation,

Administration, and Maintenance

(OAM) cells. The PTI also carries traffic

congestion notification information.

The table below contains the defini-

tionsof the differentPTI values.

Cell Loss Priority

The Cell LossPriority (CLP) field is usedfor trafficcontrol and isset to either 0 or

1. When it is setto 1, the cellhas a low

priority, allowing switches to drop the

cellif the networkbecomescongested.

Header Error Control

The Header Error Control (HEC) field is

used for error detection and allows for

some error correction capability. HEC is

calculated from the firstfour bytes of the

header and not from the payload. A cor-

rectable HECerror occurs when a single

error existsin the header. Cellswith a

correctable HECerror should be correct-

ed by the ATM switch. A non-correctable

HECerror occurs when multiple errors

exist in the header. Cells with non-cor-

rectable HEC errorsshould be dropped

by the ATM switch.

P TI D ef in it io n

Value

000 User cell, no congestion encountered, user-to-user

001 indication = 0

010 User cell, no congestion encountered, user-to-user011 indication = 1

100 User cell, congestion encountered, user-to-user

101 indication = 0

110 User cell, congestion encountered, user-to-user

111 indication = 1

OAM end-to-end associated cell

OAM end-to-end associated cell

Reserved for future use


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Elements of an ATM NNI CellAn NNI cell contains the same informa-

tion as a UNI cell, butit has a slightly

different cell structure. Instead of the

GFCfield, the NNI cell adds four bits to

the VPI field.

ATM Cell AlignmentThe purpose of cellalignmentis to

allow the receiving networkelement

the ability to synchronize with the fram-

ing of the incoming transportsignal so

that it can extractthe cellsfrom the bit

stream for processing. Cell alignment is

also referred to ascell delineation. In

addition to the two ATM cell structures,

two typesof cell alignment are used in

an ATM network, Header Error Control

(HEC) alignment and PhysicalLayer

Convergence Protocol (PLCP) align-

ment. HECalignment places ATM cells

directly within the DS1 or DS3 payload

without allocating any extra overhead.

As discussed in the section on UNI cell

structure elements, HEChaslimited

error correction capability. PLCP align-

mentrequires more overhead bytes

than HEC, providing additionalerror

checking capability. With PLCP align-ment, ATM cellsare first aligned with a

PLCP frame, then they are mapped into

the payload of a DS1 or DS3 frame

before transporting. OC-3c and OC-12c

ATM can only support HECcell align-

ment. DS1 and DS3 ATM support both

HECand PLCP cell alignment.

ATM Cell PayloadThere are several ATM cell payload cat-

egories. The two most common

categories are user cells and OAM cells.

User cellscontain live customer infor-

mation in the payload. OAM cells

include Alarm Indication Signal (AIS),

Remote DefectIndication (RDI), and

loopbackcells, which are used for net-

workfault management. AIS and RDI

cells indicate alarmsin the same man-

ner asSONET carrier signals. Ifa switch

port is not configured properly or loses

service, AIScells are sentto indicate

the address with the anomaly. RDI is

the response that other switchessend

to incoming AIS alarms. RDI alarms are

sent on the return address. Loopback

cellsmay be transmitted to a switch in

order to determine ifa return path has

been established. Ifan ATM switch

responds to a loopbackcell, the cell is

returned on the return address. Unliketraditional loopbacks, the entire chan-

nel is not looped up, justthe loopback

cell itself.

6

ATM Network ComponentsATM is a service that requires a back-

bone transportsignal such as DS3 or

SONET. The customers traffic (voice,

video, or data) isconverted into ATM

cells by means of an ATM edge device.The traffic is then switched through an

ATM edge switch or sentdirectly to the

DS3 or SONET transportsignal. An ATM

backbone switch in the central office

mayfurther switch ATM cells as wellas

provide a connection to other service

providers. Figure 5 illustrates the com-

ponents of an ATM networktransported

over a SONET backbone.

Figure 5. Components of an ATM network.

ATM

Switch

ATM

Switch

OC-12

Ring

ATM Backbone Switches Installed at COATM Edge Switches Installed at network edge

New Tork EastLos Angeles West

OC-3c

OC-3cATMT1

Video

FrameRelay

ATMOC-3c

OC-3c

ATM

Switch

ATM

Switch

OC-3c

OC-3c

ATM

Switch

ATM

Switch

T1

Video

FrameRelay

ATM

Edge

Device

ATM

Edge

Switch

ATM

Switch

ATM

Switch

ATM

Switch

ATM

Edge

Device

ATM

Switch

ATM

Switch


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A Layered Testing StrategyThisapplication note is the second

comprehensive guide for serviceproviders using the Acterna FST-2310

to installand maintain telecommunica-

tions networks. Both application notes

contain specific testsand a trou-

bleshooting appendixto isolate

common problemsassociated with the

transport network. Ifyou have difficulty

with anyof the tests, please contact

Acternas Technical Assistance Center

(TAC) at 1-800-638-2049. The TACstaff

would also appreciate hearing from

you regarding additional tipsto

enhance the troubleshooting appen-

dix.

The testing strategy outlined in these

application notes is an efficient, bot-

tom-up testing approach designed to

systematicallyeliminate problems

found at the transport testing layer that

may affect higher-layer services. Unlike

the layers in the Open Systems Inter-

connection (OSI) Basic ReferenceModel, which describe protocol rela-

tionships, the testing layers thatare

referred to in thisdocument represent

categoriesof common problems and

solutions gathered from numerous

field installation and maintenance

calls. Figure 6 identifies the layers used

in these testing applications.

7

Physical layer testing identifiesa vari-

ety of problems caused by improperline build-out, connector or cabling

faults, repeater failure, optical reflec-

tions, and optical loss. Testsinclude

pulse shape, jitter, signal measure-

ments, BERT, optical return loss, and

optical insertion loss. These tests are

performed primarilyat DS3 demarca-

tion pointsas wellas in the optical

backbone. Since physical layer prob-

lemscommonlycause intermittent and

hard-to-find problems at higher layers,

it is critical to verify DS3 and optical

backbone operation during installation

to prevent callbacks.

SONET configuration layer testing elim-

inates common problems associated

with SONET circuitsetup. Testsinclude

SONET timing, SONET path configura-

tion, error and alarm reporting, and

concatenated signal configuration.

These tests, detailed in the SONET Test-

ing with the Acterna FST-2310application note, ensure that the signal

is properly installed for the desired

service. SONET configuration layer test-

ing willresult in reduced turn-up time

and fewer maintenance calls.

ATM configuration layer testing verifies

ATM Virtual Path/VirtualChannel(VP/VC) configuration. Specifictests

include ATM switch configuration, end-

to-end channelsetup, DSLAM

configuration, alarm and error report-

ing, errored cell handling, throughput,

and priority configuration. These tests

are performed during the installation of

the backbone ATM transport network or

during the configuration of ATM serv-

ice. Itis important to include in-service

testing since data transport problems,

such as delayvariation and conges-

tion, can only be roughlysimulated

during out-of-service testing. The

unpredictable nature of data networks

can cause problemsto surface even

after out-of-service simulationshave

functioned properly. The in-service

tests include monitoring ATM conges-

tion, alarms, errors, and delay

variation. Thisapplication note thor-

oughly testsand verifies ATM transport

configuration to ensure trouble-freeservice turn-up.

ATM TESTING OVERVIEW

ATM Configuration Layer

SONET Configuration Layer

Physical LayerTestingStrategy

Figure 6. Transport testing layers.


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ATM Network TestingCustomersexpect error-free deliveryof

data, voice, and video services. ATM

service quality depends not onlyon

error-free transmission facilities, but it

also dependson error-free perform-ance ofthe ATM networkelements. ATM

network elements, unlike those in

SONET networks, support very little

switch-to-protectcircuit redundancy.

Also, since ATM networks are designed

for speed, the underlying assumption

is thatthe physical layer will perform

flawlessly. Because of this assump-

tion, ATM switches do notre-transmit

cells. Instead, the ATM network places

the responsibilityfor re-transmission

on the application using ATM. As a

result, less-than-perfect physical layer

performance causes excessive re-

transmission, which ultimatelycauses

network congestion, more dropped

cells, and more cellre-transmission.

To avoid thisspiraling effect, this appli-

cation note presentsfour tests that

verifydifferentelements in the ATM

network, provide an end-to-end check

of the network, perform in-servicemonitoring, and verify adequate Quali-

ty ofService (QoS) metrics. It is strongly

recommended that allof these tests

are performed to ensure proper opera-

tion of the ATM network. The tests are

briefly described as follows.

(1) ATM Switch Verification Test- Veri-

fies proper installation and

provisioning of the ATM switch. This

testis vital, as the ATM switch isthe

entrypointfor customer traffic into the

ATM network.

(2) End-to-End ATM Network Perfor-

mance Test - Verifies the proper

operation of all of the elements in the

ATM network. Thistest simulatescus-

tomer traffic to ensure proper routing of

traffic and proper configuration of the

network elements.

(3) In-Service ATM Monitoring Test -Helps maintain proper operation of the

ATM network after customer trafficis

applied. This testprovidescontinuing

information on networkstatus and per-

formance without affecting customer

traffic.

(4) DSLAM Provisioning Test - Used to

verify proper installation and configu-

ration of the DSLAM for Digital

Subscriber Line (DSL) service.

8


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GENERAL SETUP

Required Equipment and OptionsIn order to perform the testsdescribed

in this application note, the following

equipment is required: Fiber OpticCleaning Kit (Part#2550)

Two FST-2310s test sets with the

following options: TB2310-OC12 SONET OC-12 TX/RX

(may be required if test access is OC-12)

TB2310-OC3 SONET OC-1/3/3c Transmitter

and Receiver

TB2310-ATM-OC12, ATM Analysis for

OC-12 and/or

TB2310-ATM-OC3, ATM Analysis for

OC-3 and/or

TB2310-ATM-DS3, ATM Analysis for

DS3 and/or

TB2310-ATM-DSN, ATM Analysis for

DS1 and DS3

For OC-3cor OC-12c ATM: three fiber

opticcables (single mode or

multi-mode depending on the

configuration) with the proper

connector (FC/PC, ST, or SC on the

FST-2310 top panel)

For DSLAM provisioning: one

Acterna DSL-350 test set

Configuration ParametersThe Acterna FST-2310sATM functionality supports the configuration of the

following settings:

9


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Test Setup for ATM Testing at a DS1

Access Point

1. Select the DS1 ATM test as follows:

On the Application Bar, tap the Term button.

Select Terminate T1.

Select T1 ATM.Select QoS.

2. Configure the DS1 signal as follows:

Tap the Setup button.

Set T1 Framing to ESF, Timing to Internal, and

PLCP to On or Off (as appropriate for the network

being tested).

Select OK.

3. Examine the DS1 Primary LEDs:

Verify that no red LEDs are illuminated.

Verify that the following DS1 Primary LEDs are illu-

minated (green): Signal, Frame.

4. After the expected testing time, access the

results as follows:

For each results pane, tap the Result Group button,

and then select T1 Pri.

On the left results pane, tap the Result Category

button, and then select Summary.

Verify that the left results pane indicates Results

OK.

Test Setup for ATM Testing at aDS3 Access Point

1. Select the DS3 ATM test as follows:

On the application bar, tap the Term button.

Select Terminate DS3.

Select the appropriate ATM payload being tested.

Select QoS.

2. Configure the DS3 signal as follows:


Set DS3 Framing to M13 or C-BIT, Timing to

Internal, and PLCP to On or Off (as appropriate for

the network being tested).

Select OK.

4. Examine the DS3 Primary LEDs:


Verify that the following DS3 Primary LEDs are illu-

minated (green): Signal, Frame.


results as follows:

For each results pane, tap the Result Group button,

and then select DS3 Pri.




OK.

10

Configuring the FST-2310 TestPadfor Different Access Rates


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Test Setup for ATM Testing ata SONET

Access Point

1. Select the SONET ATM test as follows:


Select the appropriate rate for the carrier signal

being accessed.Select the appropriate ATM payload being tested.

Select QoS.

2. If testing DS3 ATM, configure the DS3 signal by

following step 2 of Test Setup for ATM Testing at a

DS3 Access Point.

3. Configure the SONET transmit signal as follows:


Set Timing to Internal, and then select the appro-

priate transmit wavelength for the network being

tested.

Where applicable, select the channel(s) mapped

for the ATM payload. Verify that Tx=Rx is checked.Select OK.

Verify that Laser On is illuminated.

4. Examine the SONET LEDs:


Verify that the following SONET LEDs are illuminat-

ed (green): Signal, Frame, Path Ptr.

If testing DS3 ATM or DS3 Muxed ATM, verify that

the following DS3 LEDs are illuminated (green):

Signal, Frame.

If testing DS3 Muxed ATM or VT1.5 ATM, verify that

the following DS1 LEDs are illuminated (green):

Signal, Frame.


results as follows:

On the left results pane, tap the Result Group but-

ton, and then select SONET Pri.




OK.


button, and then select Signal.

Verify that the SONET Rx Frequency is within

range, depending on the test access.

NOTE: Appendix D lists SONET line rates and their

associated frequencies.


button, and then select Line.

Verify the following results:

Path Ptr Just = 0

Path Ptr Value = stable, anywhere from 0 to 782

#1: ATM Switch Verification TestThe ATM Switch Verification Test, per-

formed during out-of-service testing,

verifies the proper provisioning of the

mostcritical element in an ATM net-

work. Symptomsof an improperlyprovisioned ATM switch include mis-

routed, dropped, or incorrectly

prioritized cells. These symptomscan

prevent cells from arriving attheir des-

tinations and/or corruptanother

users data. Consequently, one or

more customers mayexperience lost

data, echoing during voice conversa-

tions, or jitter during a video

transmission. In addition, failure of

the ATM switch to regenerate cor-

rectable ATM cellsor drop

non-correctable ATM cells can result in

unnecessary re-transmission or mis-

routing. The purpose of thistest is to

verify that each switch in the ATM net-

workhas been properly provisioned in

order to isolate potential service prob-

lemsbefore live traffic is applied. The

objectivesof thistestare to verify:

Routing table configuration

Correction (bythe switch) of

correctable errors Dropping of non-correctable errors

Proper handling of ATM AIS and

RDI alarms

Proper BIP error operation

Configuring the FST-2310 TestPad

1. Configure the FST-2310 for the correct carrier

signal as follows:



being accessed.

Select the appropriate ATM payload being tested.

Select QoS.


Select Internal timing, set the appropriate framing

format, and set PLCP to On or Off (as appropriate

for the network being tested).

For testing at a SONET access point, select the

channel(s) mapped for the ATM payload. Verify

that Tx=Rx is checked.

2. Configure the ATM transmit channel addresses

as follows:

Set the Correlation Tag to 2310 and the Tx/Rx Cell

Type to TTC 1.

Set the Interface to UNI, select Profile 1 and

select the desired address of the VPI and VCI

being tested.

Note: PTI and CLP are normally set to 0 unless

testing special network functions.

Select Profile P2, P3, or P4 to program additional

background traffic or other addresses that require

testing. Program these profiles in the same man-

ner as described above. If additional traffic is not

desired, leave these background profiles at all

zeros (idle cells).

3. Select the foreground transmit channel in the

Pri Tx Profile box.

Select the background transmit channel in the Sec

Tx Profile box.

4. Select the bandwidth as follows:

Set the Bit Rate to Variable.

Note: This test can also be performed using a

Constant Bit Rate.

Select the Continuous Bandwidth and Burst Gap

desired.

Select the Peak Bandwidth and Burst Length

desired.

Select the Background Bandwidth desired in the

Secondary Profile Tx Cells. Select OK.

Note: When the background and foreground total

less than 100%, the remaining cell traffic sent bythe FST-2310 is idle.

Connecting the FST-2310 to the Circuit

1. For fiber jumpers, clean all fiber connectors and

test set connectors.

2. Connect the cables to the FST-2310 and the ATM

network device as shown in Figure 8.

Note: Perform the appropriate pre-test setup,

equipment verification, and carrier signal proce-

dures before proceeding.

ATM

Switch

FST-2310

Figure 8. Connecting the FST-2310 to an ATM Switch.


12/22

Performing the ATM Switch

Verification Test


Verify that the green Signal and Frame LEDs are

illuminated for the carrier signal being accessed.

For testing at a SONET access point, verify the fol-

lowing results:

The carrier signal frequency is within the allowed

range.

Path Ptr Just = 0

Path Ptr Value = stable, anywhere from 0 to 782

Note: Appendix D lists SONET line rates and their

associated frequencies.

a) Verify proper routing table configuration

Tap the Restart button.

In the left results pane, tap the Results Group but-

ton, and then select ATM.

Tap the Results Category button, and then select

Summary.


OK.

Verify the results in the following results categories:

ATM LEDs

No red LEDs are illuminated.

ATM STATS

Mask Cells = The number of cells being

transmitted from the FST-2310

Total Utilization % < 100%

Total Congestion % = 0.00%

Mask Congestion % = 0.00%

Correlation Tag = 2310

% Mask CLP = 0%

ATM QoS

Mis-inserted Cells = 0

Out-of-Sequence Cells = 0

Lost Cells = 0

ATM ERRORS

HEC Errors = 0

Correctable HEC Errors = 0

Non-Correctable HEC Errors = 0

For DS3 PLCP framing, also verify:

PLCP Frame Word Errors = 0

PLCP BIP Errors = 0

PLCP FEBEs = 0

b) Verify proper non-correctable HEC error

operation

Note the following results on the network ATM

switch.

Number of Correctable HEC Errors

Number of Non-Correctable HEC Errors

Note: The ATM switch may not have these results.

Set the Error Type to HEC (Noncorr).

Tap the Noncorr HEC Error button to insert one non-

correctable error.


ton, and then select ATM.Tap the Results Category button, and then select

Errors.

Verify that Non-Correctable HEC Errors = 1.


QoS.

Verify that Lost Cells = 1.

Verify the following results on the network ATM

switch:

Correctable HEC Errors value does not increment

from previous result.

Non-Correctable HEC Errors value increments by 1

from previous result.

c) Verify proper correctable HEC error operation

Set the Error Type to HEC (Corr).

Tap the Correctable HEC Error button to insert one

correctable error.

Verify that Lost Cells = 1 (remaining from Step 3).

Verify that Correctable HEC Errors = 1.


switch:

Correctable HEC Errors value increments by 1 from

previous result.

Non-correctable HEC Errors value does not incrementfrom previous result.

d) Verify proper ATM alarm operation

Set the OAM Type to Segment and the Alarm Type to

VC AIS (F5).


If the ATM network device does not support AIS/RDI

alarms, then verify that the ATM alarms are passed

through.

Tap the VC AIS (F5) Alarm button.

In the results category of the left results pane, select

LED.

Verify that the VC AIS (F5) LED is illuminated.Tap the VC AIS (F5) Alarm button again to cancel

the AIS alarm.

Verify that the VC AIS (F5) history LED is illuminated.

Set the Alarm Type to VC RDI (F5).

Tap the VC RDI (F5) Alarm button.

Verify that the VC RDI (F5) LED and the VC AIS (F5)

history LED are illuminated.

Tap the VC RDI (F5) Alarm button again to cancel

the RDI alarm.

Verify that the VC RDI (F5) history LED is illuminat-

ed.

If the ATM network device supports AIS/RDI alarms,

then verify that ATM alarms are handled properly.Tap the VC AIS (F5) Alarm button.

Verify that the VC RDI (F5) LED is illuminated.

Verify that the ATM device reports the AIS alarm.

Tap the VC AIS (F5) Alarm button again to cancel

the AIS alarm.

Verify that the VC RDI (F5) history LED is illuminat-

ed.

Set the Alarm Type to VC RDI (F5).

Tap the VC RDI (F5) Alarm button.

Verify that the VC RDI (F5) LED is illuminated.

Tap the VC RDI (F5) Alarm button again to cancel

RDI alarm.

e) Verify BIP error operation

Note: Perform the following steps for DS3/DS1 PLCP

ATM only.

Note the following result on the network ATM switch:

Number of PLCP BIP Errors

Note: The ATM switch may not have this result.


Set the DS3 or T1 Error Type to BIP.

Tap the Error Insert button to send one BIP error.

Verify the BIP results as follows:


PLCP FEBEs = 1

Note: The switch may not support FEBEs. Therefore,

this result may be 0.


switch.

PLCP BIP Error increments by 1 from previous result.

Note: The ATM switch may not have this result.

Refer to Appendix C for results interpretation. If any

of the tests result in a failed response, refer to

Appendix B for troubleshooting tips.

12


13/22

#2: End-To-End ATM NetworkPerformance TestThe End-to-End ATM NetworkPerfor-

mance Testverifies the end-to-end

setup and configuration of allof the ATM

elements responsible for transmitting

cells. These elements include ATMswitches, SONET network elements, and

SONET cross-connectdevices. This out-

of-service test simulatescustomer ATM

addressesand bandwidths, verifiesthe

proper configuration of allof the

devices, and verifiesthatthe destina-

tion properlyreceivesthe transmitted

ATM cells. The objectives ofthe testare

to verify:

Proper cellrouting through the

ATM network

Compliance ofQoSmeasurements

to SLAs

Proper handling of loopbackcells


1. Place an FST-2310 at each end of the circuit and

arbitrarily identify them as East and West. If only

one FST-2310 is available (East), the far end (West)

will be looped back using a jumper cable.

2. At East and West, configure the ATM transmit

channel addresses as follows:


Set the Tx/Rx Cell Type to O.191 and the Interface to

UNI, and then select Profile P1

Select the desired address of the VPI and VCI being

tested.

Note: PTI and CLP are normally set to 0 unless test-

ing special network functions.

Select PROFILE P2, P3, or P4 to program additional


testing. Program these profiles in the same manner

as described above. If additional traffic is not

desired, leave these background profiles at all zeros

(idle cells).

3. At East and West, select the foreground transmitchannel in the Pri Tx Profile box.


Tx Profile box.

4. At East and West, select the bandwidth as fol-

lows:



Constant Bit Rate.


desired.


desired.

Select the Background Bandwidth desired in theSecondary Profile Tx Cells box.

Note: When the background and foreground total

less than 100%, the remaining cell traffic sent by

the FST-2310 is idle.

5. At East, set the Correlation Tag to 2310.

6. At West (ignore if loopback), set the Correlation

Tag to 1212.

7. Select OK.


1. For fiber cables, clean all fiber connectors and


2. At East and West, connect the cables as shown in

Figure 9. If only one FST-2310 is available (East),

loopback the far end (West) using a jumper cable.

Note: Perform the appropriate pre-test setup, equip-

ment verification, and carrier signal procedures

before proceeding.

Performing the End-to-End ATM Net-

workPerformance Test

a) Verify proper cell routing and QoS measure-

ments


At East and West, allow the test to run for the

expected testing time, and then verify the test

results as follows:




Summary.Verify that the left results pane indicates Results OK.

Verify the results in the following results categories:

ATM LEDs


ATM STATS


transmitted from the FST-2310.



% Mask CLP = 0 %

ATM QoS


Out-of-Sequence Cells = 0

Lost Cells = 0

Avg. Delay Variation (ms), Max. Delay Variation

(ms), Avg. Round Trip Delay (ms), Max. Round

Trip Delay (ms) conform to the established SLAs.

ATM ERRORS

HEC Errors = 0



For DS3 PLCP framing, also verify:PLCP Frame Word Errors = 0

PLCP BIP Errors = 0

PLCP FEBEs = 0

If a loopback exists at West, verify the following East

result:

Correlation Tag = 2310

If a loopback does not exist at West, verify the fol-

lowing results:

Correlation Tag = 2310 at West

Correlation Tag = 1212 at East

b) Verify proper handling of loopback cells1. At East, configure the test set for the appropriate

signal rate and payload as follows:



being tested.

Select the appropriate payload being tested.

Select Stats.

Complete the Configuring the FST-2310 TestPad

section above.

2. Tap the Setup button.

Set OAM Loopback Type to VC Loopback.

Select OK.


3. Tap the Insert Loopback button to insert the

desired number of loopback cells.

4. Verify the test results as follows:




Stats.


Loopback Cells = The number of loopback cells

transmitted by the FST-2310

Timed-Out Loopback Cells = 0




13

FST-2310

West or

DS3 or OC-3c

ATM Connections East

FST-2310

ATM

Switch

ATM

SwitchTransport

Network

Figure 9. Connecting two FST-2310sfor end-to-end testing.


14/22

#3: In-Service ATM MonitoringTest

The In-Service ATM Monitoring Test is a valuable tool

for maintaining proper ATM network operation with-

out affecting customer traffic. Since ATM network

utilization is difficult to predict, ATM network per-formance can be compromised even after end-to-

end simulations pass testing. Sometimes, the only

way to determine how a network is performing is to

monitor it in-service. This test provides early detec-

tion of service degradation and indicates delay vari-

ation, congestion, and overall utilization of the cir-

cuit. Installing test access monitoring points using

splitters, monitor jacks, or dedicated ATM test

access points allows proactive problem correction

and isolation before network performance is degrad-

ed. The objectives of the test are to:

Locate congested VPI/VCIs

Identify low-priority traffic that may be dropped

Obtain an indication of the total utilization ofthe circuit

Locate AIS or RDI alarms

Monitor ATM results and bandwidth utilization

Monitor Quality of Service metrics


1. Configure the test set for the appropriate signal

rate and payload as follows:

On the Application Bar, tap the MON/THRU button.


being tested.


Select Stats.

2. Configure the ATM receive primary channel

address as follows:


Select Summary.

Set Timing to Recovered and ATM Search Type to

Live Traffic Cells.

Select OK.




2. Connect the cables to the

Performing the In-Service ATM

Monitoring Test

a) Locate the congested VPI/VCIs and AIS/RDI

alarms

Locate all active addresses as follows:

Tap the Start Search button.

Tap Next VPI/VCI.

Note: The results for each address found can be

viewed in the left results group

Tap Next VPI/VCI to find other VPI/VCI addresses.

Note any addresses that indicate AIS or RDI alarms

and refer to Appendix B to correct these alarms.

Tap Save VPI/VCI to Rx Profile.

Set the Rx Profile to Rx P.





Summary.

Verify that the left results pane indicates Results OK.


ATM LEDs


ATM STATS

Total Utilization % < 100%



% Mask CLP = 0.00%

ATM ERRORS

HEC Errors = 0



For DS3 PLCP alignment, also confirm the following:


PLCP BIP Errors = 0

PCLP FEBEs = 0

Repeat this procedure until all alarms and congest-

ed addresses are found and corrected.

b) Monitor Quality of Service metrics

For addresses that correspond to constant bit rate

(CBR) service:

Tap Save VPI/VCI to Rx Profile.

Set the Rx Profile to Rx P.On the Application Bar, tap the MON/THRU button.


being tested.


Select QoS.





Summary.


OK.


ATM QoS


(ms), Avg. Round Trip Delay (ms), Max. Round Trip

Delay (ms) conform to the established SLAs.




#4: DSLAM Provisioning Test

The DSLAM Provisioning Testverifies the

proper installation and configuration of

the DSLAM. The test simulatesincoming

trafficfrom the ATM network in order to

identifyproblems(before customer traf-

fic isapplied) that mayarise during the

turn-up ofthe DSLAM, such asfaulty

connections, low throughput, and inad-

equate QoSmetrics. The objectives of

the testare to verify:

Proper cabling connectionsto

the DSLAM

Acceptable throughput

Compliance to the established QoS

Configuring the FST-2310 TestPad and

the DSL-3501. Configure the ATM transmit channel addresses as

follows:


Set the Correlation Tag to 2310 and the Tx/Rx Cell

Type to TTC 1.

Set the Interface to UNI, select Profile P1, and then

select the desired address of the VPI and VCI being

tested.

Note: PTI and CLP are normally set to 0 unless test-

ing special network functions.

Select PROFILE P2, P3, or P4 to program additional


testing. Program these profiles in the same manner

as described above. If additional traffic is not

desired, leave these background profiles at all zeros

(idle cells).

2. Select the foreground transmit channel in the PriTx Profile box.


Tx Profile box.

3. Select the bandwidth as follows:



Constant Bit Rate.


desired.


desired.

Select the Background Bandwidth desired in the

Secondary Profile Tx Cells box.Note: When the background and foreground total

14

ATM

Switch

ATM

Switch

FST-2310

Figure 10. Connecting the FST-2310 to the ATM

switch.


15/22

less than 100%, the remaining cell traffic sent by

the FST- is idle.

4. Configure the DSL-350 350+ as follows:


Tap the Scroll Menu button until Mode is highlight-

ed.

Tap the + button until ATM Loopback is displayed.

Tap the Accept button.

Tap the Scroll Menu button to return to the main

ADSL setup menu.

Tap the Loopback button.

Connecting the FST-2310 and DSL-350

to the Circuit



2. Connect the cables to the FST-2310 and the DSL-

350 as shown in Figure 11.

Note: Perform the appropriate pre-test setup, equip-ment verificqtion, and carrier signal procedures

before proceeding.

Performing the DSLAM Provisioning

Test

a) Verify proper connection of the DSLAM to the

network


After the expected testing time, verify the following

results on the DSL-350

Verify that the ATM Sync LED is illuminated.

b) Verify acceptable throughput

Verify that the Cells Received on the DSL-350

matches the Cells Transmitted on the FST-2310.




Summary.


OK.


ATM LEDs


ATM STATS



ATM QoS

Lost Cells = 0


Errored Cells = 0

c) Verify compliance to established QoS


ATM QoS


(ms), Avg. Round Trip Delay (ms), Max. Round Trip

Delay (ms) conform to the established SLAs.

15

FST-2310

DSLAM

DSL-350

Figure 11. Connecting the FST-2310 to the DSLAM.


16/22

This appendix provides a list of items to check if your test setup or test results do not show the expected

results as described in this application note.

Rx Pulseson the top panelconnector does not illuminate.

Replace the possiblydefective opticalpatch cord.

Clean the optical fiber and testset connector.

Verify that the optical connector keys are lined up atboth ends of the jumper cable.

Verify carrier signal test setup.

Verify physical layer and SONET configuration.

SignalLED on the frontpaneldoesnot illuminate.


Verify that the proper line rate is selected and that testconnections are correct.

Verify physical layer and SONET configuration.

SONET payload isAuto or Unknown after the test starts.


Verify that the proper line rate is selected and that testconnections are correct.

If alarm conditions exist on the FST-2310 LEDs, reconfigure the SONET networkelement(NE) for a concatenated signal (OC-

3c ATM payload) or a non-concatenated signal (DS3 ATM payload).

Verify SONET configuration.

Summarycategory indicates Path Pointer Size

Thisindicatesthatthe SONET NEis incorrectlyconfiguring the pointer size bits of the H1 byte in the SONET overhead.

Interconnecting thissignal with other vendors equipmentmay cause some SONET NEsand ATM switches to alarm with Lossof Pointer (LOP).

SONET BIP Errorsexist.

Thisindicatesthat the end-to-end carrier signal is suffering parity errors. Thiscan cause DS3 Parity Errors, excessive re-

transmission of ATM traffic, and ultimately a congested network. Verify the physical and configuration test layers.

For an optical carrier signal, checkinsertion loss and return loss to verifyfiber performance iswithin specifications.

OC-n Rx Frequency is displayed in Summary.

DS3 RxFrequency is displayed in Summary.

DS1 RxFrequency is displayed in Summary.

Path Ptr LED is illuminated.

Path Ptr Just isnot equal to 0.

Thisindicatesthatthe carrier signal is not timed properly, causing problems in the asynchronous ATM network. Verify the

physicaland configuration test layers.

Checktiming source configuration on the NEto verifythat the configuration is External.

Verify that the SONET NE is not configured for non-revertive holdover.

Data Syncon the frontpanel isnotilluminated.

For an opticalcarrier, verify thatthe ConcatLED isilluminated in the SONET LEDs category. Ifnot illuminated, reconfigure the

ATM NE for concatenated signaltransmission (if applicable).


Checkthe Summary category for physical layer errorscorrupting the ATM payload. If found, re-verify the carrier signal.

16

Appendix A: Troubleshooting Tips for SONET, DS3, and DS1

Carrier Signal Testing


17/2217

This appendix provides a list of items to check when your test setup or test results do not match what is

described in this application note during the carrier signal test setup.

HECErrorsis notequal to 0.

PLCP BIP Errorsis notequal to 0.

PLCP Frame Errorsis notequal to 0.

PLCP FEBEsis notequal to 0.

Checkthe Summarycategory for carrier errors. If found, re-verify the carrier signal.

ostCells isnot equalto 0.

Verifythatthe channel isproperly mapped through the ATM NEs.

Verify thatNon-Correctable Errors are notbeing generated on the far side of the channelconnection, causing the switch to

drop the cells.

Examine the congestion result, Total Congestion %. If thisresultis non-zero, then the switch may be congested, causing itto

drop cells. Ifthe % MaskCLP result isalso non-zero (thisaddresshasa low priority), then these cells should be dropped. If

the % MaskCLP resultis zero, then high prioritytraffic is being dropped. To correctthe congestion problem, determine

which addressesare exceeding their bandwidth and correct problemson those channels.

Verify thatthe addressisnot exceeding itsallowable bandwidth. Reduce the simulated bandwidth in the ATM Txsetup. If

the LostCellsresultstops incrementing ata lower utilization, note the maximum rate thatcan be supported.

Verifythatthe port isconfigured for the proper data rate.

Correlation Tag isnotequal to the transmitted value.

Checkfor physicalloopbackson the switch or network.

CheckATM switchesto identify internal loopbacks.

Use AnyTTCTest Cellmode in the ATM Search Type function to locate other Acterna testcells thatmaybe on the network.

Mis-inserted Cells isnotequalto 0.

Thisindicatesthatthe FST-2310 isreceiving cells with the same addressas programmed in the ATM RxProfile, but some of

the incoming cellsare not Acterna test cells.

Ensure that the ATM Rx Profile has the correctaddressprogrammed asthe maskand thatthisaddress excludes other

possible active celladdresses. Thiscan be accomplished by removing the X (dontcare) from the GFC, VPI, or VCI fields

and programming specificaddresses.

Verify thatthe ATM Txbackground celladdressesare not configured to transmit the same addressas the primarytest cell.

Verify thatthe ATM switch willdrop Non-Correctable HECErrors asdescribed in the ATM Switch Verification Test. Otherwise,

the ATM switch may incorrectly route a cellbased on an errored VPI/VCI address.

Verify thatthe routing table in the ATM switch doesnot have anyconflicting destination addresses.

Out-of-Sequence Cellsis notequal to 0.

Contact the switch manufacturer.

TotalCongestion % isnot equalto 0.

MaskCongestion % isnot equalto 0.

Thisindicatesthatan ATM switch issending outcongestion indications. Ifthe TotalCongestion % ismuch larger than the

MaskCongestion %, then the problem isprobablylocalto the ATM switch under test. Ifthe MaskCongestion % and the Total

Congestion % are smalland very close together, then the congestion problem is probably originating from an ATM switch

downstream. Backtrackto find the ATM switch, which is the source ofthe ATM celladdress corresponding to the receive mask.

Verify thatthe transmitted cellsare notconfigured with congestion indicationsbyensuring thatthe PTI field is setto 0.

Correct the ATM switch congestion problem byanalyzing active channels and rerouting addresses, as necessary.

Appendix B: Troubleshooting Tips for ATM Testing


18/22

Total Utilization percentishigh or is 100%.

When examined in-service, thisindicatesthatthe circuitdoes nothave any excesscapacityto handle bursts ofdata or

additionalcapacity. Thissituation can place addresseson the circuitat risk, particularly those addresseswith CLP=1.

ATM resultsare unavailable.

Verifythe carrier signal test setup. The FST-2310 is notreceiving ATM cellsor isreceiving ATM cells thatdo notmatch the ATM RxProfile. Verifyaddresssetup.

LostCellsis unavailable.

Mis-inserted Cellsis unavailable.

Out-of-Sequence Cellsis unavailable.

Correlation Tag is unavailable.

Errored Cellsis unavailable.

The FST-2310 isnot receiving Acterna testcells. Use AnyTTCTest Cellin the ATM Search Type function to locate and use

these cells.

ATM categoriesdisplay ResultsUnavailable.

Verifythe carrier signal test setup.

For Min./Max./Avg. DelayVariation results, the ATM test mustbe configured for QoS.

DelayVariation results are notapplicable (N/A) ifthe receive maskisconfigured with an X (dontcare) in the GFC, VPI, or VCI

fieldsin the ATM RxProfile. Thisconfiguration allows for the analysis ofmultiple cellsand willgive a confusing result. Remove

the Xfrom each of the fields and program specificaddresses.

% MaskCLP isnot equalto 0.

Verify thatthe specificaddressbeing analyzed isintended to have a low priority. Idle cells(address 0) will often have a CLP=1.

Verify thatthe addressis not exceeding its allocated bandwidth, causing the switch to markit as eligible to drop. Measure

utilization using MaskCellsand compare thisresult to the configured ATM switch portand the customersbandwidth.

DelayVariation displaysUnavailable. Wait a few moments for the result to stabilize.

Cellrate is too low to accuratelymeasure delayvariation.

Message window displaysSearch: Match Not Found.

In Preview mode, thisindicatesthatno active addresses were found on the circuit. Verify ATM NE configuration.

In Search mode, thisindicatesthatthe specified search parameter was not found. Specified search parametersinclude both

Acterna test cells and AIS/RDI alarms. VerifyATM NEconfiguration. Some ATM NEs do not supportthese alarms.

AISand RDI alarmsexist.

OAM AISalarms indicate thatan addresscoming into the switch hasbeen lost. Use AISCells mode in the ATM Search Type

function to identify the address with the alarm. Verify thisaddress on the ATM switch aswell as on the corresponding incoming

signalfor proper configuration.

OAM RDI alarms indicate thata switch is responding to an OAM AISalarm. Use RDI Cellsmode in the ATM Search Type function

to identifythe address with the alarm. Thisaddresswillbe the return path for an address coming into the switch. Examine that

incoming addressfor alarmsand configuration.

18


19/2219

This appendix provides an explanation of the various results that you may see during testing, helping you

to understand the effect of certain test results on network services and to determine the source of net-work problems.

MaskCells

These results indicate the number of cells that match the current ATM Rx Profile. The bandwidth should be the same as that


Total Congestion %

MaskCongestion %

A single bitin the PTI field is used by ATM equipment to indicate congestion. Congested switchesset thisbit when theyare

overloaded. Since overloaded switches drop cells, the TotalCongestion % and Mask Congestion % results are crucial to deter-

mine the state ofthe ATM network. These two results should remain low on lightly loaded ATM switchesor networks.

% MaskCLP

The CLP resultsprovide a percentage and count of cells which have a CLP equal to 1 (for mask cells only). This result is impor-

tant because ATM switches, if overloaded, can drop cellswith CLP=1. Switchescan also change CLP from 0 to 1 if the cell traffic

exceedscontracted levelsor if the switch isoverloaded. Thus% MaskCLP indicatesthe percentage of cells thatcould be

dropped by the switch or network.

HECErrors

HECError Rate

The HECerror count and rate results will indicate seriousbit error problemson the line. Correctable HECErrors are single bit

errors that occur within the ATM header. Although these errors can be corrected byATM switches, they indicate biterror prob-

lemson a SONET line. Non-Correctable HECErrorsare two or more bit errorsin an ATM header. Cells with these errorswill bedropped by network equipment.

Min. DelayVariation

Max. Delay Variation

Avg. DelayVariation

Delay variation is the difference between the actualarrival timesof ATM cellsfrom their expected arrival times. The result is

measured in milliseconds(ms). Min. DelayVariation isthe measurementof the late arrivalof cells from their expected arrival

time (-0.01 ms late, for example). The cell thatarrived last is displayed. This number isalways a negative value. Max. Delay

Variation is the measurement of the early arrivalof cells from their expected arrival time. The cell thatarrived the earliest is dis-

played. Avg. Delay Variation is a variable average of the absolute value of the cells thatarrived early and late. For constant bit

rate (CBR) service, these results should be very low.

Appendix C: Results Interpretation


20/2220

Appendix D: SONET Line Rates and Frequencies

Line Rate Minimum Frequency (Hz) Maximum Frequency (Hz)

STS-1/OC-1 51,838,963 51,841,037

OC-3 155,516,890 155,523,110

OC-12 622,067,558 622,092,442

OC-48 2,448,270,234 2,488,369,766


21/2221


22/22

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Acterna FST-2310 ATM Testing Application Note