troubleshooting ip telephony networks—part ii ip telephony networks—part ii ... • call routing...

Copyright © 2003, Cisco Systems, Inc. All rights reserved. Printed in USA.7991_05_2003_c2

111© 2003, Cisco Systems, Inc. All rights reserved.VVT-30117991_05_2003_c2


Troubleshooting IP Telephony Networks—Part II

VVT-3011



Session Objectives

• Understand the Cisco CallManager Call Routing and Digit Analysis

• Understand Echo and steps to resolve Echo in IPT Networks

• Understand and Troubleshoot Cisco CallManager Directory and Integrations


What You Should Know

• CCM configuration and operation

• Basic understanding of Voice Gateways, LDAP Protocol

• Understanding of Cisco CallManager DC Directory



Agenda

• Call Routing in Cisco CallManager

• Troubleshooting Echo

• Troubleshooting Directory Integrations


Agenda






Call Routing—Digit Analysis

• The heart of Call Routing in Cisco CallManager is Digit Analysis

• Primary job: select the destination whose address is the best match for a sequence of dialed digits

• Secondary job: modify the caller ID/called number before extending the call to the selected destination


Elements of Call Routing

• Route Patterns

• Route Filters

• Transformations

• Translation Patterns

• Partitions and Calling Search Spaces

• Call Routing Common Problems



Route Patterns

• A route pattern is an numerical address

• Some addresses, such as directory numbers, match only one dialed digit string (1000, 2000, 561212, etc…)

• Other addresses, such as gateway route patterns, match a range of dialed digit strings (1XXX, [2-9]XXXXXX, 9.@, etc…)


Wildcards: Range Matching

DescriptionWildcardMatch exactly one digit0, 1, 2, 3, 4, 5,

6, 7, 8, 9, *, #Any single digit in the range 0-9X

One occurrence of any of the digits in the brackets[xyz…]

One occurrence of any digit from x to y[x-y]

Any digit that is not between x and y.[^x-y]

One or more digits in the range 0-9!

Zero or more occurrences of the previous wildcardwildcard?

One or more occurrences of the previous wildcardwildcard+

Matches the NANP - discussed later@



Pattern Examples

1111

*1*1

12XX

13[25-8]6

13!#

Matches numbers between 1200 and 1299

Matches 1326, 1356, 1366, 1376, 1386

Matches any number that begins with 13, is followed by one or more digits, and ends with #;135# and 13579# are example matches

Matches 1111

Matches *1*1

13[^3-9]6 Matches 1306, 1316, 1326, 13*6, 13#6


Closest-Match Routing

• CallManager matches dialed digits to the route pattern that is the most explicit match

• CallManager performs digit analysis on a digit-by-digit basis

• CallManager has a concept of matches and potential matches

A match means the dialed digits match a configured route pattern (i.e. 1000 matches 1XXX, 100X, 1000, etc…)

A potential match is a route pattern that might match given thedialed digits if more digits are dialed to complete the match(i.e. If you dial 10 then 1XXX is a potential match)

• A call is extended when there is a match and there are no more potential matches (or the inter-digit timeout expires)—with the exception of urgent priority route patterns



Example 1: Closest Match Routing

1111

1211

1[23]XX

131

13!

13[0-4]X

User’s dial string:

CallManager actions:

Configured Route Patterns



1111

1211

1[23]XX

131

13!

13[0-4]X

User’s dial string: Might match

Might match

Might match

Might match

Might match

Might match

Provide dial toneWait


<off hook>


Digit analysis: match(fqcn="9195555644", cn="15644", pss="PA:Line1:Cisco:Local:Long Distance:International", dd="")

Digit analysis: potentialMatches=PotentialMatchesExist




1111

1211

1[23]XX

131

13!

13[0-4]X


Might match

Might match

Might match

Might match

Might match

Break dial toneWait


1


Digit analysis: match(fqcn="9195555644", cn="15644", pss="PA:Line1:Cisco:Local:Long Distance:International", dd=”1")




1111

1211

1[23]XX

131

13!

13[0-4]X

User’s dial string: Doesn’t match

Might match

Might match

Doesn’t match

Doesn’t match

Doesn’t match

Wait


12







1111

1211

1[23]XX

131

13!

13[0-4]X


Might match

Might match

Doesn’t match

Doesn’t match

Doesn’t match

Wait


121






1111

1211

1[23]XX

131

13!

13[0-4]X


Match!

Match!

Doesn’t match

Doesn’t match

Doesn’t match

No other patterns couldmatch; extend call to thebest match


1211



Digit analysis: potentialMatches=NoPotentialMatchesExist




1111

1211

1[23]XX

131

13!

13[0-4]X


Match!

Match!

Doesn’t match

Doesn’t match

Doesn’t match

1211

Matches 1 digit string

Matches 200 digit strings






1111

1211

1[23]XX

131

13!

13[0-4]X


Match!

Match!

Doesn’t match

Doesn’t match

Doesn’t match

1211

Matches 1 digit string


Select as closest match







1111

1211

1[23]XX

131

13!

1[0-4]XX


Might match

Might match

Might match

Might match

Might match

Provide dial toneWait


<off hook>


Digit analysis: match(fqcn="9195555644", cn="15644", pss="PA:Line1:Cisco:Local:Long Distance:International", dd=”")




1111

1211

1[23]XX

131

13!

1[0-4]XX


Might match

Might match

Might match

Might match

Might match

Break dial toneWait


1







1111

1211

1[23]XX

131

13!

1[0-4]XX


Doesn’t match

Might match

Might match

Might match

Might match

Wait


13






1111

1211

1[23]XX

131

13!

1[0-4]XX


Doesn’t match

Might match

Match!

Might match

Match! and might match

Keep waiting; moredigits might cause adifferent pattern to match


131







1111

1211

1[23]XX

131

13!

1[0-4]XX


Doesn’t match

Match!

Doesn’t match

Match!

Match!

Extend call to the bestmatch


1311<timeout>




1111

1211

1[23]XX

131

13!

1[0-4]XX


Doesn’t match

Match!

Doesn’t match

Match!

Match!

1311<timeout>



Matches ∞ digit strings, However for the purposes of closest match routing in this case, this matches 100 digit strings because you only consider the number of potential strings given the number of digits dialed





1111

1211

1[23]XX

131

13!

1[0-4]XX


Doesn’t match

Match!

Doesn’t match

Match!

Match!

1311<timeout>



Matches ∞ digit strings, However for the purposes of closest match routing in this case, this matches 100 digit strings because you only consider the number of potential strings given the number of digits dialed




|PretransformCallingPartyNumber=15644|CallingPartyNumber=15644|DialingPartition=|DialingPattern=13!|DialingRoutePatternRegularExpression=(13X+)|DialingWhere=|PatternType=Enterprise|PotentialMatches=PotentialMatchesExist|DialingSdlProcessId=(2,84,7)|PretransformDigitString=1311|PretransformTagsList=SUBSCRIBER|PretransformPositionalMatchList=1311|CollectedDigits=99915644|UnconsumedDigits=|TagsList=SUBSCRIBER|PositionalMatchList=1311



Special Wildcards

• ‘.’ denotes a portion of a route pattern that can be stripped when the pattern matches

• @ wildcard is a macro for many patterns that encompass the North American Numbering Plan (NANP)


Using ‘.’ With Digit Discarding Instructions

• Use digit discarding instructions (DDI) to strip initial digits

• With the exception of NoDigits and PreDot, DDIs only apply to patterns that contain the @ wildcard

PBX

Cisco CallManager Match: 9.8XXX

Discard: PreDot

User dials: 98123

Called party: 8123



@ Wildcard

• A macro that causes the Cisco CallManager to add 166 patterns for the NANP

• Use digit discarding instructions to control which digits are sent as the called number

• Use route filters to add fewer patterns and restrict outside dialing


@ Wildcard: Digit Discarding Instructions

• Use digit discarding instructions to discard whole sections of the dialed number

User dials: 9101028812145551212

Called party: 12145551212

PSTN

Cisco CallManager

Match: 9.@Discard:

PreDot 10-10-Dialing



Digit Discarding Instructions

Used forDialed/Discarded DigitsInstructions

Trailing-#

10-10-Dialing

IntlTollBypass

11D→10D

11D/10D→7D

PreAt

PreDot

PSTN compatibility98 1010321 011 33 1234 #

Suppressing carrier selection

98 1010321 1 214 555 1212

Toll bypass98 1010321 011 33 1234 #

Toll bypass98 1010321 1 214 555 1212

Toll bypass98 1010321 1 214 555 1212Access codes98 1 214 555 1212

Access codes98 1 214 555 1212

If the pattern is 9.8@…



• Route Patterns

• Route Filters

• Transformations






Route Filters: Limiting The @ Wildcard

• Eliminates or constrains route patterns added by the @ pattern

• Relies on tags, named substrings of the dial plan file

• Uses three operators: Exists, Does not exist, and == <value>

• Operators connected with AND and OR


Route Filters—NANP File

To see all the route pattern that encompass the @ wildcard when using the NANP, open the file C:\Program Files\Cisco\DialPlan\NANP



Route Filters

9 [2-9]11

9 [2-9]XX XXXX

9 [2-9]XX [2-9]XX XXXX

9 011 3[0-469] !

Assume that adding pattern 9.@ with no route filter causes these individual patterns to get added…

9 1 [2-9]XX [2-9]XX XXXX

311, 611, 911 SERVICEs

7-digit dialing by OFFICE CODE

10-digit local dialing byLOCAL AREA CODE

11-digit long distance dialing byAREA CODE

International dialing by COUNTRY CODE


Example 1: Route Filters

9 [2-9]11

9 [2-9]XX XXXX

9 [2-9]XX [2-9]XX XXXX

9 011 3[0-469] !

If we add 9.@ with route filter SERVICE EXISTS, this happens…

9 1 [2-9]XX [2-9]XX XXXX

Added: contains SERVICE

Not added: no SERVICE




9 [2-9]XX XXXX

9 [2-9]XX [2-9]XX XXXX

9 1 [2-9]XX [2-9]XX XXXX

9 011 3[0-469] !




9 [2-9]11

9 [2-9]XX XXXX

9 [2-9]XX [2-9]XX XXXX

9 011 3[0-469] !

If we add 9.@ with route filter COUNTRY-CODE DOES-NOT-EXIST, this happens…

9 1 [2-9]XX [2-9]XX XXXX

Added: no COUNTRY-CODE




Not added: contains COUNTRY-CODE9 011 3[0-469] !



9 [2-9]11

9 [2-9]XX XXXX

9 [2-9]XX [2-9]XX XXXX

9 011 3[0-469] !

If we add 9.@ with route filter AREA CODE == 900, this happens…

9 1 [2-9]XX [2-9]XX XXXX

Not added: no AREA-CODE


Not added: no AREA-CODE (It contains LOCAL-AREA-CODE)

Added: AREA-CODE constrained to 900


9 [2-9]XX XXXX

9 [2-9]XX [2-9]XX XXXX

900

9 011 3[0-469] !

9 [2-9]11



Tags in the NANP Dial Plan

The escape sequence used for entering a long distance carrier co de101 0321 1 214 555 1212TRANSIT-NETWORK-ESCAPE

Long distance carrier code101 0321 1 214 555 1212TRANSIT-NETWORK

A particular extension served by a given exchange1 214 555 1212SUBSCRIBER

Access to local telephony provider services1 411SERVICE

A specific value associated with calls to the satellite country code01 1 881 4 1234 #SATELLITE-SERVICE

The office or exchange code of a North American call1 214 555 1212OFFICE-CODE

The national number component of an international call01 1 33 123456 #NATIONAL -NUMBER

The initial 0 required for operator-assisted long-distance calls0 214 555 1212LONG -DISTANCE-OPERATOR

The initial 1 required for long distance direct-dial calls1 214 555 1212LONG -DISTANCE-DIRECT-DIAL

The initial 0 required for operator-assisted local calls0 555 1212LOCAL -OPERATOR

The initial 1 required by some 7-digit calls1 555 1212LOCAL -DIRECT-DIAL

The area code in a 10-digit local call214 555 1212LOCAL -AREA-CODE

The digit that denotes the operator component of an international call01 0INTERNATIONAL OPERATOR

The digit that denotes the direct-dial component of an international call01 1 33 123456 #INTERNATIONAL -DIRECT-DIAL

The initial 01 of an international call01 1 33 123456 #INTERNATIONAL -ACCESS

The #, which cancels inter-digit timeout in international calls01 1 33 123456 #END-OF-DIALING

The country code in an international call01 1 33 123456 #COUNTRY-CODE

The area code in an 11-digit long distance call1 214 555 1212AREA-CODE

DescriptionExample numberTag Name


Important Points: @ Wildcard and Route Filters

• Closest match routing works on the individual patterns of an @ pattern, not on the pattern as a whole

• Route filters don’t block calls in and of themselves; they restrict which patterns are added to digit analysis at initialization time




• Route Patterns

• Route Filters

• Transformations





Transformations

• Digit analysis’ secondary job is to change the caller ID and/or called party number before extending a call to a device

• Calling party transformations change the caller ID

• Called party transformations change the called party number



Calling Party Transformations

• Use Calling Party’s External Phone Number Mask checkbox• Calling party transformation mask• Prefix digits to Calling Party Number (as of Cisco

CallManager 3.2)• Can restrict presentation (Private Number) by setting the

Calling Party Presentation to Restricted (in Cisco CallManager 3.3 and later)


Calling Party Transformations

• Calling Party Number Presentation can be overridden on the Gateway Configuration page.

• Calling Party Number can be overridden by the ‘Caller ID DN’ parameter on the Gateway Configuration page.



About Masks

• Can contain digits 0-9, *, # and X

• Mask is applied to a number in order to extend or truncate it

• If the result of a mask operation still contains wildcards, the whole number is discarded

45000972813XXXX

972813500045XXX

9728135000

45000

An X in a MaskLets Digits PassThrough

Digits in MasksReplace Number Digits

Blanks BlockNumber Digits

_____


Use Calling Party’s External Phone Number Mask Checkbox

• When checked, Cisco CallManager masks two phone parameters to determine the caller ID

Match: 9.@Use Calling Party’s External Number

Mask

External Calling PartyNumber Mask:972813XXXX

Caller Id:45000

972813XXXX9728135000

Line45000 PSTN

Cisco CallManager



Calling Party Transformation Mask

• Cisco CallManager applies the specified mask to the caller ID

Match: 9.@Calling Party

Transformation Mask:

408525XXXX

Caller Id:45000

408525XXXX4085255000

Line45000 PSTNPSTN

Cisco CallManager


Calling Party Transformation Order

• Apply the Use External Phone Number Mask checkbox

• Apply the Calling Party Transformation Mask

45000

97281XXXXX

408525XXXX

9728145000

4085255000

Directory Number

External PhoneNumber Mask

Calling PartyTransformationMask

Caller ID



Called Party Transformations

• Three kinds of Transformations for Called Party Number:


Called Party Transformation Mask

Prefix Digits



• Covered earlier in this presentation

• Used primarily with the @ wildcard

• Allows you to throw away whole sections of the dialed number, like area code or carrier code



Called Party Transformation Mask

• Works just like Calling Party Transformation Mask

• Affects the called number, not the caller ID


Prefix Digits

• Cisco CallManager prepends the specified digits to the called number

Match:@Prefix Digits: 9

Called number:92145551212

Line45000

User dials: 2145551212

PSTN

Cisco CallManager



Called Party Transformation Order

• Apply Digit Discarding Instructions

• Apply the Called Party Transformation Mask

• Apply Prefix Digits

9 1010321 12145551212

10-10-Dialing

XXXXXXXXXX

9 12145551212

2145551212

Dialed Number

Digit DiscardingInstructions

Called PartyTransformationMask

Prefix Digits

Called Number 82145551212

8


Called Party Transformation Order

• Transformations performed on the Route Group Details page of a Route List override the settings configured on a Route pattern

• For example, if a Route Pattern has a DDI of “Pre-Dot” and the Route Group Details of a Route List says “NoDigits”, the “Pre-Dot” configuration on the route pattern is ignored

Overrides




• Route Patterns

• Route Filters

• Transformations





Translation Patterns

• Almost exactly like route pattern: uses wildcards, transformations, etc.

• Results of transformations are the input for another trip through digit analysis

• Use to handle extension mapping among other things

• All Translation Patterns are Urgent Priority route patternsA call is routed immediately to an urgent priority route pattern when a match is made, even if there are potential matches left



Routing Flowchart

Pattern Type?

Find Best MatchDigits

Apply Calling and CalledParty Transformations

Extend Call to Destination

Route Pattern

DigitsFind Best Match

Apply Calling and CalledParty Transformations

Pattern Type?Translation Pattern


Translation Patterns: Extension Mapping

Analyze: 9725559XXXTranslation Pattern

Called Party Transformation Mask: XXXX

Dialed Number: 9725559030

Line 9030(9725559030 to Outside Callers)

Resulting Number:9030

Analyze: 9030Route Pattern

Called Party: 9030

PSTN

Cisco CallManager




• Route Patterns

• Route Filters

• Transformations




Partitions and Calling Search Spaces

• Partitions and Calling Search Spaces cause the majority of Call Routing configuration errors

• Understanding Partitions and Calling Search Spaces is essential to understanding Call Routing in Cisco CallManager

• Allow toll bypass from one geographical region to another

• Allow different outside calling privileges by class of calling user

• Allow multiple tenants with overlapping dial plans to be served by the same Cisco CallManager



Partitions and Calling Search Spaces Analogy

RitaDave

305 555 5000

Miami Yellow Pages

Dave 305 555 5000

Rita wants to call Dave

Dave lists his numberIn a directory

To do so, she needs to know Dave’s number



RitaDave

305 555 5000

Miami Yellow Pages

Dave 305 555 5000

To Look up Numbers, RitaLooks through the

Directories She Owns

If She Doesn’t Havethe Right Directory…

Dallas White Pages

Outlook Address Book

Little Black Book

…She Can’t Place the Call

Rita’s List of Directories




RitaDave

305 555 5000

Miami Yellow Pages

Dave 305 555 5000But if She Has the

Directory Dave HasListed His Number in…

Dallas White Pages

Miami Yellow Pages

Little Black Book


…the Call Will Go Through

Miami Yellow Pages

Miami Yellow Pages



RitaDave

305 555 5000

Miami Yellow Pages

Dave 305 555 5000

Dallas White Pages

Miami Yellow Pages

Little Black Book


The Directory in which Dave’s Number Is Listed Is His Number’s Partition

The List of Directories in which Rita Looks up Numbers Is Her Calling Search Space

Miami Yellow Pages

Dallas White PagesMiami Yellow Pages

Little Black Book



Partitions and Calling Search Spaces Definition

• Partition: A logical grouping of patterns; All patterns in a partition are equally reachable

• Calling search space: An ordered list of partitions; Digit analysis looks through the caller’s list of partitions when searching for the closest match for the caller’s dialed number


Partitions and Calling Search Space Rules

• Calling entities (phones, lines, gateways, applications) have calling search spaces

• Called entities (route patterns, translation patterns, directory numbers, feature codes) have partitions




• Digit analysis looks through every partition in a calling search space and looks for the best match

• The order of the partitions listed in the calling search space is used only to break ties when there are equally good matches in two different partitions

• Contrary to popular belief, the partition the calling party’s line is in has NO effect on where you can call from that line; Only the Calling Search Space for that phone/device matters



• If no partition is specified for a pattern, the pattern is listed in the null partition

• All callers look in the null partition (as well as any partitions specified in their calling search space) to resolve dialed digits

• The null partition is always the last partition in any Calling Search Space

• Closest-match routing takes precedence over the partition ordering in a Calling Search Space, so a closer match in the null partition will be used to route a call over a less-explicit match in a partition




• Route Patterns

• Route Filters

• Transformations





I Don’t Get Outside Dial Tone at the Right Time

• A checkbox in route pattern allows the user to specify whether a pattern should receive outside dial tone

• Cisco CallManager applies outside dial tone only when all patterns that match or might match, including call park, Meet-Me conference, message waiting off/on, and other numbers, expect to have outside dial tone applied




Dallas PSTNDallas Line

45000

Pattern:

9.XXXXXXXXX

Apply Outside Dial Tone

Call Park Pattern:

91XX

(Don’t Apply Outside Dial Tone)

Dials: <off hook>

Might Match

Might Match

Cisco CallManager




45000

Pattern:

9.XXXXXXXXX


Call Park Pattern:

91XX


Dials: 9

Might Match

Might Match

Both patterns might match: no outside dial tone applied

Cisco CallManager





45000

Pattern:

9.XXXXXXXXX


Call Park Pattern:

91XX


Dials: 92

Doesn’t Match

Might Match

The Only Patterns that Might Match Ask for Outside Dial Tone, so Play It

Cisco CallManager


Cisco CallManager Is Choosing 9.@ over My Specific Pattern

• The @ pattern causes many individual patterns to be added on the user’s behalf

• If an individual pattern in the @ wildcard is a better match than the user’s pattern, then the @ pattern will be chosen

• Look in the NANP file to see the list of patterns or look in the CCM trace to see which pattern was matched



Trailing-# Is Not Discarded

• Most Digit Discarding Instructions work only with the @ pattern (with the exception of NoDigits and PreDot)

• If the configured pattern is 9.011!#, the Trailing-# Digit Discard Instruction will have no effect


Outside Local Calls Wait Ten Seconds Before Routing

• The @ pattern includes patterns for 10-digit local dialing ([2-9]XX XXX XXXX) and 7-digit local dialing ([2-9]XX XXXX); This causes delayed call routing in areas where 7-digit local dialing is in effect

• To eliminate the delay, create a route filter that says WHERE LOCAL-AREA-CODE DOES-NOT-EXIST and assign the route filter to the @ route pattern



I Can’t Block Calls to 900 Numbers

• Specifying a route filter of AREA-CODE == 900 does not in itself block 900 numbers

• Configure two route patterns: one @ pattern without a route filter and one with route filter AREA-CODE == 900; Tell CallManager to ‘block this pattern’ on the second pattern

• If a call with area code 900 is dialed, the second pattern will match (because it is a more explicit match) and the call will be blocked; otherwise, the first pattern will match and the call will route3


Why Is there a Calling Search Space on a Line and on a Phone?

• The Calling Search Space assigned to line applies to all phones that share the line

• The Calling Search Space assigned to a phone applies to all lines on that phone

• If a Calling Search Space is configured in both places, both search spaces are used

• The Calling Search Space on the Line comes before the Calling Search Space on the Phone (only when there is a tie)



Agenda





Troubleshooting Echo

• Echo Sources and Definition

• Eliminating Echo

• Tools and Methodology for Troubleshooting Echo



Echo—What Is Echo? What Is Echo?

• Objectionable reflected voice energy in speaker’s receive path

• Function of signal strength and delay

• Why is echo prevalent in packet telephony?


Sources of Echo: Hybrid Echo

HybridHybrid HybridHybrid

Two-wireSubscriber

Loop

Two-wireSubscriber

Loop

Four-wireTrunk

Echo



Sources of Echo: Acoustic Echo

• Poor acoustic isolation between the earpiece microphone and the microphone in handsets and hands-free devices introduce acoustic echo

Earpiece

Echo


Types of Echo

Talker Echo—The effect is the talker hears his/her own voice delayed by the total echo path delay time

Listener Echo—The effect is the person listening hears the talker and an echo of the talker



What Makes Echo a Problem?

• An analog leakage path between analog Tx and Rx paths

• Sufficient delay in echo return for echo to be perceived as annoying

(delays < 25ms are masked as sidetone)

• Sufficient echo amplitude to be perceived as annoying

For Echo to Be a Problem, All of the Following Conditions Must Exist:


PSTN

The Impact of Packet Voice on Echo Perception

• The packet segment of the voice connection introduces large delay (typically > 30 ms in each direction)

• The introduction of delay causes echoes (from analog tail circuits) that are normally indistinguishable from side tone to become perceptible

• Because the delay introduced by packet voice is unavoidable, the voice gateways must prevent the echo

Low Delay, Potential Echo Sources

Large Delay,No Echo Sources

WAN



Example Topology of a Tail Circuit

PBXGWFXO:FXS

PBXPBX T1T1

Tail Circuit

Analog Tail Circuit

Echoes Are Created in Analog Tail Circuits, They Do Not Form in Digital Call Legs


Echo in IP-PBX Environment

PSTN Phone IP PhoneVoice GW

PSTN

IP Phone Users HearsEcho Caused by Hybrids

in PSTN Network

HybridEcho

PSTN Phone Users Hears EchoCaused by Acoustic Couplingbetween the Earpiece and

Microphone in IP-Phone Handset

AcousticEcho

LAN



Echo Cancellation in an IP-PBX Environment

EchoCanceller in

IP Phone

Echo Canceller in

Voice GW

Echo Canceller in Voice GWCancels the Echo that IP Phone

Users May Hear

Echo Canceller in IP PhoneCancels the Acoustic Echo that PSTN Users May Hear

Independent Cancellers

PSTN LAN

Voice GW








Eliminating Echo—TerminologyTail Circuit

Rin Rout

SinSout

H(t)^

y(t)^

-

ACOMACOM

ERLEERLE

ERL = Echo Return Loss = Rout—Sin

ERLERL

ERLE = Echo Return Loss Enhanced= Rout—SoutACOM—Acombined = Rin—Sout

IP Network


Eliminating Echo—Terminology

• Echo Cancel Coverage is the amount of time the Echo Canceller will ‘Remember’ a signal that has been output; This parameter must be set to a value greater than the time it takes the echo to return back to the gateway



Characteristics of Conventional Echo Cancellers

• The convergence rate depends on the properties of the reference (Rin) signal

• Silence and telephony signaling tones (DTMF, ringback, etc…) are poor reference signals and will not train the echo canceller significantly

• The convergence rate is inversely proportional to the duration of coverage provisioned

• Violation of the minimum assumed ERL prevents convergence due to falsely detecting doubletalk (when both parties talk at the same time)

• Adaptation during doubletalk will cause divergence


Characteristics of the dspware Echo Canceller before 12.2(13)T

• Echo coverage is “provisionable” via CLI in 8 ms steps up to 32 ms; The greater the coverage provisioned, the slower the convergence rate

• Limitations of DSP MIPs and memory prohibit the expansion of coverage

• The minimum ERL is assumed to exceed 6 dB

• The EC does not perform well with echo environments that a) exceed 32ms in duration, b) are time varying (conferencing changes, acoustic echo), c) have an ERL < 6dB



Characteristics of the dspwareEcho Suppressor

• Can eliminate echo due to convergence times of echo canceller

• Echo Suppressors allow one way communicationvoice-port cli: echo suppressor < # seconds >

• Must be disabled for modem communication

• Automatically disables during double talk

• Available in 12.2(8)T5 for NM-HDV and 12.2(11)T2 for most other voice interfaces (i.e. NM-2V)


Echo Cancellation Enhancements

• Extends coverage to 64ms

• Allows required ERL drop from 6dB to 0 (via CLI)

• G.168 Complaint

• Much faster convergence time

• Echo suppressor not available (and is not needed) with ECAN Enhancements

cli: voice-card <slot>codec complexity {high | medium} ecan-extended



Echo Cancellation Enhancements -Platform Support

• 12.2(13)T adds support on NM-HDV, 7200/7500, ICS7750 MRP, High Complexity on 1700, High Complexity on MC3810

• 12.2(15)ZJ and second release of 12.3T add additional platform support for NM-HDA and AIM-VOICE

• 12.2(8)YH, 12.2(13)ZH, and the first release of 12.3T add medium complexity support for 1700

• 12.3(1) adds support for medium complexity on MC3810.

• Second release of 12.3T adds support for High Complexity Analog and Medium Complexity digital on the Cat4k AGM.








Narrowing Your Focus

• First, find out what the exact symptoms of the echo problem are

• Every echo case is different and must be treated on a case-by-case basis

• Isolate the problem and try to find a scenario where the echo is reproducible

• There may be several different echo problems present—isolate each one and troubleshoot one at a time


Questions to Ask

• When does the echo occur? • Throughout call?

• Only beginning of call?

• Does a single number (set of numbers) result in echo often?

• Which side hears the echo?

• Does the party hearing the echo hear themselves or the far end echoed?



What to Collect?

• Need to gather data while a call is experiencing echo

• Have users collect call-ING and call-ED numbers

• Need to produce 1004Hz tone and adjust dB levels (# or * dtmf buttons give a rough estimate if test gear is not available)

• PCM trace on PSTN tail-circuit producing the echo is very useful

• Sniffer trace

• ‘show voice call x/y:z.ts’ or ‘show call active voice’ à several iterations

• Check ERL—adjust input gain if necessary


Eliminating Echo

You need to make sure you give the echo canceller enough information to distinguish between echo and normal conversation; The only parameters you have control over are:

• Input Level (Input Gain)

• Output Level (Output Attenuation)

• Echo Canceller Coverage

• Echo Suppressor (12.2(8)T5 and later)

• Enhanced Echo Canceller (12.2(13)T and later)

• Impedance

So, How Do I Get Rid of Echo?



Measuring Echo Using a 7960 IP Phone

• To enable the tone generator, first unlock the phone by entering**# while the phone is idle; Wait at least 10 seconds before proceeding to the next step

• Type **3 on the 7960/40 keypad while the phone is not on a call;This will enable the ‘Tone’ softkey for as long as this phone is registered to CallManager

• Place a call to the source of echo

• Once the call is established, hit the ‘i’ button twice; This will bring up the statistics for the call

• If the **3 worked, you should have a ‘Tone’ softkey available; Press it and the phone will begin to generate a 1004 Hz tone at -15 dB

• The only way to stop the tone is to end the call

• Once the tone is being generated, keep the call up and then follow the procedures that follow to measure the dB levels


Measuring Echo in Cisco IOS

• 1004Hz tone coming from IP Call Leg:

• Show voice call x/y:z.tsvnt-3725-34a#sho voice call 1/0:23.23

1/0:23 23 vtsp level 0 state = S_CONNECT

callid 0x8003 B23 state S_TSP_CONNECT clld 99915506 cllg 41008

– snip –***DSP LEVELS***

TDM Bus Levels(dBm0): Rx -15.5 from PBX/Phone, Tx -15.5 to PBX/Phone

TDM ACOM Levels(dBm0): +0.0, TDM ERL Level(dBm0): +0.0TDM Bgd Levels(dBm0): -81.9, with activity being voice




• The test tone is being output as -15 and is being looped back to us with 0dB loss, so it is coming back at -15 dB

• The ERL value here doesn’t mean anything at this point since the ecan does not consider the input signal to be echo; The actual ERL is NOT really 25dB

• The OutSignalLevel shows the value of the level AFTER the outputattenuation has been applied to the signal and InSignalLevel shows the level AFTER the input gain has been applied

vdtl-3640-27a#sh call active voice - snip -OutSignalLevel=-15InSignalLevel=-15ERLLevel=25- snip -

Use the Cisco IOS command ‘show call active voice’ to look at the input and output levels for your call; The following is a call to a loopback number that just echos back whatever we send with no attenuation


Eliminating Echo

• Perform dB level adjustment procedure; Remember:Output Attenuation of a signal is performed AFTER the echo canceller has ‘seen’ the original output signalInput Gain of a signal is performed BEFORE the echo canceller has ‘seen’ the echo

Output AttenuationOutput Attenuation

Input GainInput Gain

Tail CircuitRin Rout

SinSout

H(t)^

y(t)^

-

ACOM

ERLE

ERLIP Network




• Notice the OutSignalLevel is -16 because we attenuated the -15 dB signal by 1 dB; The InSignalLevel is -17 dB due to the input gain of -1

• At this point our real ERL is 2dB, however the Echo Canceller still does not acknowledge the input signal as echo

vdtl-3640-27a#sh call active voice - snip -OutSignalLevel=-16InSignalLevel=-17ERLLevel=11- snip -

If we configure 1 dB of attenuation in each direction as follows:

The resulting levels are as follows:

voice-port 1/1:23input gain -1output attenuation 1

-15 dB minus 1 from output attenuation = -16-16 dB minus 1 from input gain = -17


vdtl-3640-27a#sh call active voice - snip -OutSignalLevel=-17InSignalLevel=-19ERLLevel=4-snip -


• Notice the OutSignalLevel is -17 because we attenuated the -15 dB signal by 2 dB; The InSignalLevel is -19 dB due to the input gain of -2

• Our expected ERL of 4dB is now correct• The G.113 specification recommends a minimum ERL of 15 dB

If we configure 2 dB of attenuation in each direction as follows:

The resulting levels are as follows:

voice-port 1/1:23input gain -2output attenuation 2

-15 dB minus 2 from output attenuation = -17-17 dB minus 2 from input gain = -19



Measuring Echo on the 6608

• Same principles apply when troubleshooting echo on a 6608, however the commands are different

• From the CatOS prompt, type ‘show port voice active <mod>/<port>’ to see the active calls on that port

• The 6608 does not show you input and output levels, however it does show the ERL and ACOM

• ERL and ACOM values are displayed as 10x the dB value, so a value of 61 is really 6.1 dB

• Echo cancel coverage is not configurable on the 6608; It is roughly equivalent to 32 ms in Cisco IOS

• The 6608 always has the echo suppressor enabled to reduce convergence echo


Adjusting Levels on Cisco CallManager

• On Skinny/MGCP gateways, the input and output dB levels are adjusted from the CallManager administration web page

• The Output level is adjusted using the ‘Audio Signal Adjustment from IP Network’ menu; (Same as output attenuation, but positive values increase volume and negative values decrease volume)

• The Input level is adjusted using the ‘Audio Signal Adjustment into IP Network’ menu; (Same as input gain)

• You must reset the gateway for the changes to take effect



Measuring Echo on the 6608Input Gain of -1 and Output Attenuation of 1

vdtl-Cat6k-PBX1> (enable) sh port voice active 4/8Port 4/8 :

Channel #23:Remote IP address : 172.18.104.74 Remote UDP Port : 24876ACOM Level Current : 45Call State : voiceCodec Type : G711 ULAW PCMCoder Type Rate : 20ERL Level : 61Voice Activity Detection : disabledEcho Cancellation : enabledFax Transmit Duration (ms) : 0Hi Water Playout Delay : 65Low Water Playout Delay : 64Receive Bytes : 373920Receive Delay : 64Receive Packets : 2337Transmit Bytes : 374240Transmit Packets : 2339Tx Duration (ms) : 42090Voice Tx Duration (ms) : 42090











Echo Canceller Coverage

• The echo canceller coverage time can be changed on IOS platforms using the echo-cancel coverage voice-port command

Router(config-voiceport)#echo-cancel coverage ?16 16 milliseconds echo canceller coverage24 24 milliseconds echo canceller coverage32 32 milliseconds echo canceller coverage64 64 milliseconds echo canceller coverage8 8 milliseconds echo canceller coverage

• Echo canceller coverage is hard-coded to 32 ms on the 6608 gateway



Impedance Adjustment

• Echo can also be caused by an impedance mismatch if both sides are not configured identically

• Default of 600r Ohm is consistent with most lines on the PSTN and PBX’s

vnt-1760-32(config-voiceport)#impedance ?600c 600 Ohms complex600r 600 Ohms real900c 900 Ohms complexcomplex1 complex 1complex2 complex 2

vnt-1760-32a#sho voice port 2/0 | inc ImpedanceImpedance is set to 600r Ohm


Rules of Thumb

• Echo on one end is typically generated at other end

• Introduced by 2 to 4 wire conversion in hybrid and impedance mismatch or via acoustic feedback

• Bits don’t leak—Echo is not introduced on digital links

• Must have sufficient ERL for ECANs to engage• Longer coverage yields longer convergence time —more so

on legacy echo cancellers. Configure the coverage so that it is long enough to cover the worst-case for your environment, but no higher

• Use **3 on 7960/40 to use the built-in 1004 Hz tone generator

• # or * DTMF tones approximate 1004Hz @ 0dB tones (on Analog phones if test gear isn’t available)



Agenda





Directory Services Overview

• Directory is a Hierarchical database to provide fast and efficient search and retrievals

• Enterprises have deployed Directories in the networks

• Applications need access to directories for accessing user data, storing application specific information



Cisco CallManager Directory Approach

• SQL DB used to store device and system configurations

• LDAP directory only used to store user profiles

• Two storage options for LDAP directory:1. Use embedded DC directory2. Use external corporate directory

• Support available for Active Directory, Netscape iPlanet


Use of Directory in Cisco CallManager

• User Authentication and Authorization

• User PreferencesExtension MobilityPersonal AssistantInternationalizationPersonal Address BookSpoken NameSpeed DialCall Forward Information

• Application Enablement, Deployment, Configuration



Corporate Directory Access

• Search users in Corp. Directory

• Display matching entries

• Select “Dial” SoftKey to make a call


Using the Embedded Directory

SQLSQL

Publisher CMPublisher CM

Subscriber CM 1Subscriber CM 1

Subscriber CM 2Subscriber CM 2

SQLMasterMaster

ReplicaReplicaReplicaReplica

CM ClusterLDAP accessLDAP access

ReplicationReplication



Corporate Directory Integration

• CCM stores user info in corporate directory instead of embedded DC directory

• Single storage point for all user info (HR, NT domain, phone)

• Information shared between CM clusters and other applications (VMail, IVR, …)

CCM Cluster 1

LDAP Access

ldap.cisco.com

CCM Cluster 2

Master

Replica


File Contents File Contents

DC Directory Log/Configuration Files

C:\dcdsrvr\log\DcdSetup.trcC:\dcdsrvr\log\DcdSetup.trc DC Directory Install LogsDC Directory Install Logs

C:\dcdsrvr\log\IntegratedSetup.trcC:\dcdsrvr\log\IntegratedSetup.trc

C:\dcdsrvr\run\dcx500\config.logC:\dcdsrvr\run\dcx500\config.log

*err.log*err.log

File/Directory NameFile/Directory Name

DC Directory Log Files Path: C:\dcdsrvr\logDC Directory Log Files Path: C:\dcdsrvr\log

CallManager Integration LogCallManager Integration Log

Potential Error Events with DC Directory OperationPotential Error Events with DC Directory Operation

C:\dcdsrvr\run\dcx500\config\ADC:\dcdsrvr\run\dcx500\config\AD

C:\dcdsrvr\run\dcx500\C:\dcdsrvr\run\dcx500\

C:\dcdsrvr\run\dcx500\config\Netscape C:\dcdsrvr\run\dcx500\config\Netscape

Active Directory Schema Update DefinitionsActive Directory Schema Update Definitions

Netscape Directory Schema Update DefinitionsNetscape Directory Schema Update Definitions

DC Directory Database LocationDC Directory Database LocationC:\dcdsrvr\run\dcx500\database C:\dcdsrvr\run\dcx500\database

DC Directory Diagnostic Files LocationDC Directory Diagnostic Files Location

C:\dcdsrvr\run\dcx500\DGyyyymmdd.tttt C:\dcdsrvr\run\dcx500\DGyyyymmdd.tttt Achieved DC Directory Diagnostic Files LocationAchieved DC Directory Diagnostic Files Location

Record of all config changes, server starts and stopsRecord of all config changes, server starts and stops



File Contents File Contents

Directory Integration Log Files

C:\dcdsrvr\log\ad_cfg.logC:\dcdsrvr\log\ad_cfg.log Successful AD Schema Update EventsSuccessful AD Schema Update Events

C:\dcdsrvr\log\at_schema_reject.txtC:\dcdsrvr\log\at_schema_reject.txt

C:\dcdsrvr\log\pluginsetup.trcC:\dcdsrvr\log\pluginsetup.trc

DC Directory Log Files Path: C:\dcdsrvr\logDC Directory Log Files Path: C:\dcdsrvr\log

AD Schema the Rejected Schema Update Entries for ADAD Schema the Rejected Schema Update Entries for AD

Schema Update Problems with ADSchema Update Problems with AD

C:\dcdsrvr\log\netscape_cfg_reject.txtC:\dcdsrvr\log\netscape_cfg_reject.txt

Netscape/Sun Directory Plugin Success Log EntriesNetscape/Sun Directory Plugin Success Log Entries

Rejected Schema Update Entry LogsRejected Schema Update Entry Logs

Netscape/Sun Directory Plugin Failure Log entriesNetscape/Sun Directory Plugin Failure Log entriesC:\dcdsrvr\log\netscape_cfg_err.logC:\dcdsrvr\log\netscape_cfg_err.log

Logs the entries for Plugin setup for AD/Netscape/SunLogs the entries for Plugin setup for AD/Netscape/Sun

C:\dcdsrvr\log\oc_schema_reject.txtC:\dcdsrvr\log\oc_schema_reject.txt

C:\dcdsrvr\log\netscape_cfg.logC:\dcdsrvr\log\netscape_cfg.log

File/Directory NameFile/Directory Name


Common Problems (Error Page)



Troubleshooting Tips (Installation/Configuration Issues)

• DC Directory is not installed or was not configured properly during the installation

• Ensure that the DC Directory Service is up and running; If it is not running check the System Event Viewer Log for logon or other startup failures for the DC Directory service

• Ensure that the DC Directory Service is not in a Paused state; This can occur if the system is short on resources such as Disk or Memory; Check the Application and System Event Viewer Log for more details; After easing the resource shortage restart DC Directory Service

• If the DC Directory Service is running launch the DC Directory Administrator from Start->Programs->DC Directory Administrator


Troubleshooting Tips (Logon to DC Directory Admin)



Troubleshooting Tips (Logon to DC Directory Admin)


Troubleshooting Tips (Improperly Configured DCD)



DCD Replication Issues (1)

• Cisco CallManager publisher server has correct user data and one or more Cisco CallManager subscriber servers either do not have user data or the user data is out of sync

• DCDirectory Service on the Cisco CallManager publisher server takes a long time to start-up (appears to stall/hang on startup)

• DCD Replication errors are logged to the Cisco CallManager publisher and/or subscriber server(s) in the “Application Event Viewer”

• Examination of “C:\dcdsrvr\run\dcx500\dcx500.out” show duplicate and/or invalid replication agreements

Symptoms



Event Log error below shows that replication failed with CallManager server “SRVCM5”

(DSA REPLICATION(17) Proc 1021, Sev 14)We have abandoned an outstanding primitive on the shadowingagreement defined below, as our association to the partner

DSA has been lost.agreement id 3

role (consumer/supplier) Supplier

partner DSA AE_Title /o=cisco.com/cn=DCDSERVER/cn=SRVCM5

old state Awaiting Coord Resp

event No association

new state Between Updates

action to take Ignore the event




• Reinstalling a Cisco Customer Response Application(CRA) server (or a Cisco CallManager subscriber) one or more times (each reinstall of CRA server/CallManager server will cause the publisher to have a new replication agreement to the subscriber)

• Decommissioning an existing CRA server (or a Cisco CallManager subscriber) without performing the DCD reconfig procedure in the CallManager clusterNote: When removing a directory node from a CallManager cluster the DCD replication agreements to the removed subscriber are NOT automatically cleaned up

• Manually running the avvid_scfg command on the subscriber more than once, i.e., a partial DCD reconfig procedure was attempted

Causes



• DCD saves state for each and every replication operation that it fails to perform

• Over a period of time this saved state information for the invalid replication agreements causes the DB to grow to several hundred MB

• C:\dcdsrvr\run\dcx500\database contains this partial replicated files

DCD Database Size Growth



Script FunctionScript Function

DCD Scripts

Reconfig_Cluster.cmdReconfig_Cluster.cmd • Reconfigures the replication agreements between the Servers in the Cluster

• Needs to be Run only on the Publisher• Does not Delete or Modify Existing Data

• Reconfigures the replication agreements between the Servers in the Cluster

• Needs to be Run only on the Publisher• Does not Delete or Modify Existing Data

Script NameScript Name

All the New DCD Scripts Are Written in PerlAll the New DCD Scripts Are Written in Perl

• Removes the replication agreements to all non existent subscribers in the cluster

• Needs to be Run only on the Publisher after removing any server from cluster

• Does not Delete or Modify Existing Data

• Removes the replication agreements to all non existent subscribers in the cluster

• Needs to be Run only on the Publisher after removing any server from cluster

• Does not Delete or Modify Existing Data

Clean_Publisher.cmdClean_Publisher.cmd

Avvid_srepl.cmdAvvid_srepl.cmd • Configures the replication agreements between the subscriber and the publisher

• Needs to be Run only on the subscribers

• Configures the replication agreements between the subscriber and the publisher

• Needs to be Run only on the subscribers

Avvid_migrate_save.cmdAvvid_migrate_restore.cmdAvvid_migrate_save.cmdAvvid_migrate_restore.cmd

• Saves and restores the DCD data in LDIF format• Data stored in C:\dcdsrvr \run\dcx500\config\Migration-

Backup directory

• Saves and restores the DCD data in LDIF format• Data stored in C:\dcdsrvr \run\dcx500\config\Migration-

Backup directory


Check DCD Version, Install Status

• CCMRegBrowser

Allows you to view the DCD Version Information

The various configuration/status parameters under HKEY_LOCAL_MACHINE\SOFTWARE\Cisco Systems, Inc.\Directory Configuration

On ALL of the configured CM servers



Change Password of Special CCM Users

• CCMPwdChangerUpdates the password of special CCM Users such as Directory Manager, CCMSysUser (replacement for ctifw), etc

Works with all supported directory servers (AD, Netscape, DCD)

Updates both the directoryand the registryon ALL CM servers

MUST reboot all of the CM servers, as the password change will be reflected in all the servers in the CallManager cluster


CallManager Registry—Before AD Integration

HKEY_LOCAL_MACHINE\SOFTWARE\Cisco Systems, Inc. \Directory ConfigurationHKEY_LOCAL_MACHINE\SOFTWARE\Cisco Systems, Inc. \Directory Configuration

CiscoBase: The OUWhere Cisco relatedInformation is stored

DIRTYPE: DefaultThe directory is DCD

LDAPURL: IP addressOf the CallManager Puband LDAP Port Number

MGRDN: The useridUsed for Directory Access



CallManager Registry—After AD Integration

CiscoBase: The OUWhere Cisco relatedInformation is stored

DIRTYPE: ADSthe directory is ADFor Netscape it is Netscape

LDAPURL: IP addressOf the Schema Masterand LDAP Port Number

MGRDN: The useridUsed for Directory Integration

HKEY_LOCAL_MACHINE\SOFTWARE\Cisco Systems, Inc. \Directory ConfigurationHKEY_LOCAL_MACHINE\SOFTWARE\Cisco Systems, Inc. \Directory Configuration


Log File for Failed Plug-in Setup

• Plugin Setup Log is written to the C:\dcdsrvr\log\PluginSetup.trc file• Common Problems, Incorrect entries for the IP Address for Schema Master Server or LDAP Port Number or Wrong User NameWrong Password• To determine the exact problem, setup the Network Monitor Trace



Log File Output—Query for Domain Name Failure

• Plugin Queries the Schema Master for the User Name, Domain Namebased on the IP Address and Port Number entered

• If Query Fails, errors are logged in the PluginSetup.trc file• Manually Populate the Information in the Plugin setup window


Log File for Insufficient Access

C:\dcdsrvr\log\ad_cfg.log C:\dcdsrvr\log\at_schema_reject.txt

User had insufficient rights to extend the Schema



Log File and Warning if Schema Update Is not Allowed


Setting the Schema Update Flag

• On the Schema Master on the command prompt runRegsvr32 schmmgmt.dll

• Open the MMC, by typing mmcOn the command line

• Add the Active Directory Schema Snap In



Setting up Network Monitor (1)

• Access the Network Monitor from the Administrative Tools Menu on the CallManager

• First time when you run the tool, select the NIC card

• Start the Network Capture Process



• Access the External Directory Server

• Stop the Network Capture




• Setup the Filter to display only LDAP Packets

• Disable all other Protocols from the display



• After setting up the Filter, Save the Capture for the Analysis/Troubleshooting

• By Default, the captures are stored in the C:\WINT\System32\NETMON\CAPTURES directory



Capture Trace (1)

User Name Used for Accessing Directory

Using LDAP

User Name Used for Accessing Directory

Using LDAP


Capture Trace (2)

LDAP ErrorLDAP Error



Summary

• Dial Plan is the key configuration in any PBX; Understanding CallManager Call routing principles eliminates most of the problems

• Echo is the most common voice quality problem faced in the packet telephony networks. Proper analysis and methodical approach helps to resolve echo problems

• For further troubleshooting and information read the technical tips on Cisco TAC web site at http://www.cisco.com/tac


More Information

• For more details on reading CCM traces, Troubleshooting Call Routing, and Echo, see here:

Troubleshooting Cisco IP TelephonyISBN 1-58705-075-7



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