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Outbound Dial Peer Matching

Hi Support Community

I have been reading various documentation and have been placing test calls and debugging the gateway but im still not 100% sure on the correct answers and would be grateful if someone could clarify for me :

Using outbound dial peers on a H323 gateway the Cisco docuemntation states it uses digit by digit analysis and as soon as a match is made this dial peer will route the call. So if we use the dialed number 9212XXXXXXX as an example it seems to match dial-peer 2 however if digit by digit anylysis is used would it not match dial peer 3 because as soon as 9212 is dialled this will match ?

dial-peer voice 1 pots

description **Local 7-Digit**

translation-profile outgoing national

destination-pattern 9[2-9]......

port 0/0/0:23

forward-digits 7

!

dial-peer voice 2 pots

description **Local 10-Digit**

translation-profile outgoing subscriber

destination-pattern 9212[2-9]......

port 0/0/0:23

forward-digits 10

!

dial-peer voice 3 pots

description **Service Numbers**

translation-profile outgoing subscriber

destination-pattern 9[2-8]..

port 0/0/0:23

forward-digits 3

Thanks, Carl Ratcliffe

3 ACCEPTED SOLUTIONS

Accepted Solutions

Outbound Dial Peer Matching

Hi Carl, when the gateway receives the call from CUCM, it would try to match the entire dial string not digit by digit analysis.

If it receives the call from POTS line and direct inward dialing is configured under the incoming dial peer, then again it tries to match the entire dial string.

In case DID is not configured,then only the GW will enter into digit collection mode.

Matching Outbound Dial Peers

In order to match outbound dial peers, the router or gateway uses the dial peer destination-pattern called_number command.

On POTS dial peers, the port command is then used to forward the call.

On Voice-Network dial peers, the session target command is then used to forward the call.

Also, when outbound peers are matched, there are two cases to consider: DID case and non-DID.

DID (Direct Inward Dial) Case

An incoming dial peer configured with DID direct-inward-dial looks like this:

dial-peer voice 1 pots

  incoming called-number 81690

  voice-port 0:D

  direct-inward-dial

On DID calls, also referred to as one-stage dialing, the setup message contains all the digits necessary to route the call, and the router or gateway should not do subsequent digit collection. When the router or gateway searches for an outbound dial peer, the device uses the entire incoming dial string. This matching is variable-length by default. This match is not done digit-by-digit because by DID definition, all digits have been received. This example helps clarify this concept:

Assume the DID dial-string is "81690". In this case, the router matches dial peer 4 and forwards the complete dial-string "81690".

dial-peer voice 3 voip

destination-pattern 816

session target ipv4:172.22.10.1

!

dial-peer voice 4 voip

destination-pattern 81690

session target ipv4:172.22.10.1

For more information on DID, refer to Voice - Understanding Direct-Inward-Dial (DID) on Cisco IOS Digital (T1/E1) Interfaces.

Non-DID Case

This case is also referred to as two-stage dialing. If DID is not configured on the matched incoming dial peer, the router or gateway enters the digit collection mode (digits are collected inband). Outbound dial peer matching is done on a digit-by-digit basis. The router or gateway checks for dial peer matches after the device has received each digit and then routes the call when a full match is made. These examples help clarify this concept:

Assume the dial-string is "81690". Immediately after the router receives the digit "6", the router matches dial peer 3 and routes the call (forwarding only the digits "816").

dial-peer voice 3 voip

destination-pattern 816

session target ipv4:172.22.10.1

!

dial-peer voice 4 voip

destination-pattern 81690

session target ipv4:172.22.10.1

Now, assume dial peer 3 is configured for wild-card matching:

dial-peer voice 3 voip

destination-pattern 816..

session target ipv4:172.22.10.1

!

dial-peer voice 4 voip

destination-pattern 81690

session target ipv4:172.22.10.1

In this case, the longest-prefix rule applies, and dial peer 4 is matched for the outbound call leg.

Hope this clarifies

//Suresh

Please rate all the useful posts.

//Suresh Please rate all the useful posts.

Outbound Dial Peer Matching

Hi Carl, Glad that I could give correct answer to your question.

>> No were could i find official documentation which detailed that when cucm sends the dialed number to the gateway

The dial-peer to/from CUCM is VoIP dial-peer and it has been mentioned in the URL Carlo posted above.

http://www.cisco.com/c/en/us/support/docs/voice/call-routing-dial-plans/14074-in-dial-peer-match.html#topic1

Matching Inbound Dial Peers

Inbound Dial Peers Elements and Attributes

Three information elements sent in the call setup message and four       configurable dial peer command attributes are used to match dial peers as       follows:

  • Inbound POTS dial peers are associated to           incoming POTS call legs on the originating router or gateway.

  • Inbound Voice-Network dial peers are associated           to incoming Voice-Network call legs of the terminating router or gateway.           Examples of Voice-Network calls legs are Voice over IP (VoIP), Voice over Frame           Relay (VoFR), Voice over ATM (VoATM), and Multimedia Mail over IP           (MMoIP).

Matching Outbound Dial Peers

In order to match outbound dial peers, the router       or gateway uses the dial peer destination-pattern       called_number command.

  • On POTS dial peers, the port command is           then used to forward the call.

  • On Voice-Network dial peers, the session           target command is then used to forward the           call.

Also, when outbound peers are matched, there are two cases to consider:       DID case and non-DID.

Please let me know if you have any further questions. I would be happy to assist you.

Kindly mark this thread as 'Answered' if you have got the correct answers to your questions.

//Suresh

Please rate all the useful posts.

                
       
                                     
               
                                                                   
                            
                                                             
                                           

Introduction

The purpose of this document is to explain how inbound and outbound       dial peers are matched to plain old telephone service (POTS) and Voice-Network       call legs.

Prerequisites

Requirements

Cisco recommends that you have knowledge of these topics:

 

Components Used

This document is not restricted to specific software and hardware       versions.

Conventions

Refer to       Cisco       Technical Tips Conventions for more information on document       conventions.

Matching Inbound Dial Peers

Inbound Dial Peers Elements and Attributes

Three information elements sent in the call setup message and four       configurable dial peer command attributes are used to match dial peers as       follows:

  • Inbound POTS dial peers are associated to           incoming POTS call legs on the originating router or gateway.

  • Inbound Voice-Network dial peers are associated           to incoming Voice-Network call legs of the terminating router or gateway.           Examples of Voice-Network calls legs are Voice over IP (VoIP), Voice over Frame           Relay (VoFR), Voice over ATM (VoATM), and Multimedia Mail over IP           (MMoIP).

The four configurable Cisco IOS® dial peer attributes and corresponding       call setup elements are shown here:

    
Dial Peer Attribute Description Call Setup Element                   (See Table 2)
gwy(config-dial-peer)# incoming called-number                     DNIS_string This dial peer command defines the called number destination or                     dialed number identification service (DNIS) string. When properly configured,                     this dial peer command uses the called number to match the incoming call leg to                     an inbound dial peer.Called number (DNIS)
gwy(config-dial-peer)# answer-address                     ANI_string This dial peer command defines the originating calling number                     or automatic number identification (ANI) string. When properly configured, this                     dial peer command uses the calling number to match the incoming call leg to an                     inbound dial peer. Calling Number (ANI)
gwy(config-dial-peer)# destination-pattern                     string When inbound call legs are matched, this command uses the                     calling number (originating or ANI string) to match the incoming call leg to an                     inbound dial peer.                 

Note: For outbound dial peers, this command is matched against the                       called number or DNIS strings.

Calling Number (ANI) for inbound or the                     Called number (DNIS) strings for outbound
gwy(config-dial-peer)# port                     port This dial peer command defines the POTS voice port through                     which calls to this dial peer are placed. Voice Port

The three call setup elements are:

    
Call Setup Element Description
Called number (DNIS) This is the call destination dial string and is derived from                     the ISDN setup message or channel associated signaling (CAS) DNIS.
Calling Number (ANI)This is a number string that represents the origin and is                     derived from the ISDN setup message or CAS ANI. The ANI is also referred to as                     Calling Line Identification (CLID).
Voice PortThis represents the POTS physical voice port.

Inbound Dial Peers Matching Process

When the Cisco IOS router or gateway receives a call setup request, a       dial peer match is made for the incoming call in order to facilitate routing       the call to different session applications. This is not a digit-by-digit match,       rather the full digit string received in the setup request is used to match       against configured dial peers.

Note: The maximum number of dial peers that can be configured on a Cisco           IOS gateway depends on the available memory (DRAM). Each dial peer consumes           approximately 6KB of memory. Make sure that you have at least 20% of the total           memory reserved for other CPU processes. If the dial peers are used for call           routing, a larger number of dial peers will add to the delay to route a call.           This will be significant as the Cisco IOS voice stack looks through dial peers           from the top down, similar to an Acess Control List.

    

The router or gateway matches the information elements in the setup       message with the dial peer attributes to select an inbound dial peer. The router or gateway matches these items in this order:

 
  1. Called number (DNIS) with the incoming           called-number command

    First, the router or gateway attempts to match the called number of           the call setup request with the configured incoming           called-number of each dial peer. Because call setups always           include DNIS information, it is recommended to use the incoming           called-number command for inbound dial peer matching. This           attribute has matching priority over the           answer-address and           destination-pattern commands.

  2. Calling Number (ANI) with the           answer-address command

    If no match is found in step 1, the router or gateway attempts to           match the calling number of the call setup request with the           answer-address of each dial peer. This attribute can           be useful in situations where you want to match calls based on the calling           number (originating).

  3. Calling Number (ANI) with the           destination-pattern command

    If no match is found in step 2, the router or gateway attempts to           match the calling number of the call setup request to the           destination-pattern of each dial peer. For more           information about this, see the first bullet in the Dial Peer Additional Information section of this           document.

  4. Voice-port (associated with the incoming call setup request) with           configured dial peer port (applicable for inbound           POTS call legs)

    If no match is found in the step 3, the router or gateway attempts to           match the configured dial peer port to the           voice-port associated with the incoming call. If multiple dial peers have the           same port configured, the dial peer first added in the configuration is           matched.

  5. If no match is found in the first four steps, then the           default dial peer 0 (pid:0) command is           used.

 

Note: Step 4 is not applicable to voice or dial           platforms such as AS5300, AS5350, AS5400, AS5800 and AS5850. If any one of the           first three steps is not used, then match dial peer 0, and the call is treated           as a dial modem call. This means that customers can get modem tones as opposed           to dial tones for inbound calls.

    

The previous selection process is displayed with this       diagram:

dial_peer_flow.gif

   

The Cisco IOS router or gateway matches only one of these conditions.       It is not necessary for all the attributes to be configured in the dial peer or       that every attribute match the call setup information. Only one condition must       be met for the router or gateway to select a dial peer. The router or gateway       stop to search as soon as one dial peer is matched.

The longest prefix matching criteria applies while each step is       performed. At each step, if multiple matches are found, the one with the       longest explicit match is chosen. This example helps clarify this concept:

Assume the incoming called number (DNIS) is "81690". Dial peer 2 is       matched.

dial-peer voice 1 pots
 incoming called-number 8....
 direct-inward-dial
!

dial-peer voice 2 pots
 incoming called-number 816..
 direct-inward-dial

Note: For inbound dial peers, the session           target command is ignored.

The Default Dial-Peer 0 peer_tag=0, pid:0

If no incoming dial peer is matched by the router or gateway, the       inbound call leg is automatically routed to a default dial peer (POTS or       Voice-Network). This default dial peer is referred to as dial-peer       0 or pid:0.

Note: There is an exception to this statement. Cisco voice and dial           platforms, such as the AS53xx and AS5800, require that a configured inbound           dial peer is matched for incoming POTS calls to be accepted as voice calls. If           there is no inbound dial peer match, the call is treated and processed as a           dial-up (modem) call.

    

Dial-peer 0 (pid:0) has a default configuration       that cannot be changed. The default dial-peer 0 fails to       negotiate non-default capabilities, services, and applications such as:

 
  • Non-default Voice-Network capabilities: dtmf-relay,           no vad, and so forth.

  • Direct Inward Dial (DID)

  • TCL Applications

Dial-peer 0 for inbound VoIP peers has this       configuration:

  • any codec

  • vad enabled

  • no rsvp support

  • fax-rate voice

    Note: The default DSCP for voice is EF codepoint 101110 (RFC 2598), and             the default DSCP for signaling is AF31 codepoint 011010 (RFC 2597). The default             dial peer does not mark packets to DSCP 0. All voice packets on the routers are             marked by default (this can be overridden by the dial peer), signaling with             AF31 and media with EF. Calls that match the default dial peer 0 should also             have this behavior.

Dial-peer 0 (pid:0) for inbound POTS peers has       this configuration:

  • no ivr application

For further explanation of this concept, see the       Case Study: Understanding Inbound Matching and Default       Dial-Peer 0 section of this document.

Special Note on isdn overlap-receiving

There are implications for inbound dial peer matching when the       isdn overlap-receving command is configured on ISDN       interfaces. After every digit is received at the ISDN layer, dial peers are       checked for matches. If a full match is made, the call is routed immediately       (to the session app in this case) without waiting for additional digits. The       'T' terminator can be used to suspend this digit-by-digit       matching and force the router or gateway to wait until all digits are received.       The 'T' refers to the T302 interdigit timer at the ISDN level, configurable       under the serial interface associated with the ISDN interface. ISDN also       provides other mechanisms to indicate the end of digits, such as setting the       Sending Complete Information Element (IE) in Q.931 information messages.

Special Note on POTS Calls with Empty Calling Number Field

Assume this configuration:

dial-peer voice 1 pots
   destination-pattern 9T
   port 1/0:1

Now, assume that an incoming call arrives with no calling number       information and is matched with the POTS dial peer based on the       destination-pattern 9T command. In this case, the       Cisco IOS router or gateway uses the "9" digit as the calling number and       forwards the call to the corresponding device, such as CallManager or the IOS       Gateway. In order to not replace the empty calling number field, create a dummy       POTS dial peer with just the incoming called-number command configured. Because the incoming       called-number statement has higher priority than       destination pattern for inbound POTS matching,       dial-peer voice 2 becomes the POTS dial peer used.

dial-peer voice 1 pots 
    destination-pattern 9T
    port 1/0:1
!
dial-peer voice 2 pots
    incoming called-number .

Special Note on Empty Called Number

The Warning message shown here, which displays when dial-peer is       configured with incoming called-number T, might raise questions in regards to       the dial-peer selection with an empty called number from an actual       router.

RTR(config)#dial-peer voice 1 pots
RTR(config-dial-peer)#incoming called-number T 

Warning: Pattern T defines a match with zero or more digits and hence could 
match with an empty number.  If this is not the desired behaviour please 
configure pattern .T instead to match on one or more digits
RTR(config-dial-peer)#

Incoming dial-peer match with an empty called number:

 
  • A "null" called-number is considered "less" qualified compared to a           port number and/or in some cases answer-address. Therefore, a match based on a           "null" called number will occur ONLY if there is no match based on either           answer-address or port-number.

  • In case of overlap dialing, a "null" called number will not match           "incoming called-number T" because timeout has not occurred.

  • A "null" called-number will match "incoming called-number T" only in           case of ENBLOCK and there is no match either because of answer-address and           port-number. The warning you see when you configure "incoming called-number T"           refers to this specific case.

Matching Outbound Dial Peers

In order to match outbound dial peers, the router       or gateway uses the dial peer destination-pattern       called_number command.

 
  • On POTS dial peers, the port command is           then used to forward the call.

  • On Voice-Network dial peers, the session           target command is then used to forward the           call.

Also, when outbound peers are matched, there are two cases to consider:       DID case and non-DID.

//Suresh Please rate all the useful posts.

Outbound Dial Peer Matching

Hello Carl, the direct-inward-dial (DID) command is effective for POTS dial peer that too Inbound direction.

PSTN--- -->E1-PRI------->Gateway(H323/SIP)------>CUCM----->IP Phone.

when the call comes in from PSTN to IP phone, the GW checks whether or not the DID is configured on the inbound dial-peer. If yes, it is called  one stage dialing and the entire called number (ex:12345) is matched against the outbound voip dial-peer (dial-peer to CUCM is a voip dial-peer).

if the called number is 12345, and 2 outbound voip dial peers to CUCM as below

dial-peer voice 1 voip
 destination-pattern 123
 session target ipv4:
!
dial-peer voice 2 voip
 destination-pattern 12345
 session target ipv4:

dial-peer voice 3 pots
description Inbund dial-peer from PSTN
incoming called-number 12345 voice-port 0/0/0:15 direct-inward-dial

In the config above, dial-peer 2 will be matched to send the call to CUCM.

if DID is not configured on the inbound dial-peer, then the outbound dial-peer matching is done digit by digit.

So when though the user dials 12345, As soon as digit 3 is receied, it will match dial-peer 2 because of
destination-pattern 123

as a conclusion: If DID is configured on the inbound pots dial-peer, then outbound dial-peer matching is against the entire (enbloc) called number and not digit by digit.

If DID is not configured, then outbound dial-peer matching is against the digit by digit called number

please let me know if you have any questions, I would be glad to answer that.

//Suresh

Please rate all the useful posts.

//Suresh Please rate all the useful posts.
10 REPLIES
New Member

Outbound Dial Peer Matching

What i should have also added is my assumption is becasue 9212 destination pattern is a better match than 9[2-9]XX and becasue its digit by digit matching and the gateway is not aware of the full length pattern. If this is the case then using and example of dialling 9212XXXX would this mean dial peer 3 is matched over dial peer 1 as their is no better match ?

dial-peer voice 1 pots

description **Local 7-Digit**

translation-profile outgoing national

destination-pattern 9[2-9]......

port 0/0/0:23

forward-digits 7

!

!

dial-peer voice 3 pots

description **Service Numbers**

translation-profile outgoing subscriber

destination-pattern 9[2-9]..

port 0/0/0:23

forward-digits 3

Outbound Dial Peer Matching

Hi Carl.

The default dialpeer hunting method is longest match (0), that's why  in case of dialed number 9212XXXXXXX dial-peer 2 would be mached

The following link, will give you a review on dialpeer matching behaviour.

http://www.cisco.com/en/US/tech/tk652/tk90/technologies_tech_note09186a008010fed1.shtml

HTH

Regards

Carlo


Please rate all helpful posts

"The more you help the more you learn"

Please rate all helpful posts "The more you help the more you learn"
New Member

Outbound Dial Peer Matching

Hi Carlo

Thanks for the response. Im taking it that  destination-pattern 9212[2-9]...... is only a better match than destination-pattern  9 [2-9]...... for an outbound dial peer matching becasue of the digit by digit matching as if the wholse string was used as it is with inbound dial peers then they would both be the same becasue they would have equal number of matches - both having 2-9 followed by 6 digits.

Another example which would probbaly clarify it for me and this is taken out of a live environment which is why it is causing me confusion, we have 2 dial peers below, 1 is used for local 7 digit so a dialling with  access code of 9 followed by 2-9 and then 6 digits, the other is used for service numbers dialling using a 9 prefix code followed by 2-9 and 2 digits. In this case does that mean if 92233445 was dialled it would always hit dial-peer 3 below and herfore only 3 digits would be forwarded  :

dial-peer voice 1 pots

description **Local 7-Digit**

translation-profile outgoing national

destination-pattern 9[2-9]......

port 0/0/0:23

forward-digits 7

!

dial-peer voice 3 pots

description **Service Numbers**

translation-profile outgoing subscriber

destination-pattern 9[2-9]..

port 0/0/0:23

forward-digits 3

Thanks, Carl Ratcliffe

New Member

Outbound Dial Peer Matching

Hi Support Community

Does anyone have any feedback on the above or below. I have another example which i cant make sense of, if Cisco says digit by digit analysis is used in outbound dial peers using best match logic and as soon as a mtach is made that dial peer is used can someone explain to me ( although it is working as i want it to just trying to understand ) why if i dial 9514XXXXXXX dial-peer 1007 is used and not 1003.

If it is correct what Cisco say then i would expect dial-peer 1003 to be hit as if digit by digit anaysis is used then a match is made after 9514 ?

dial-peer voice 1007 pots

description ## Local and Mobile ##

destination-pattern 9[2-9]..[2-9]......

port 0/0/1:23

forward-digits 10

!

dial-peer voice 1003 pots

description ## Service Numbers ##

destination-pattern 9[2-8]..

port 0/0/1:23

forward-digits 3

Thanks, Carl Ratcliffe

Outbound Dial Peer Matching

Hi Carl, when the gateway receives the call from CUCM, it would try to match the entire dial string not digit by digit analysis.

If it receives the call from POTS line and direct inward dialing is configured under the incoming dial peer, then again it tries to match the entire dial string.

In case DID is not configured,then only the GW will enter into digit collection mode.

Matching Outbound Dial Peers

In order to match outbound dial peers, the router or gateway uses the dial peer destination-pattern called_number command.

On POTS dial peers, the port command is then used to forward the call.

On Voice-Network dial peers, the session target command is then used to forward the call.

Also, when outbound peers are matched, there are two cases to consider: DID case and non-DID.

DID (Direct Inward Dial) Case

An incoming dial peer configured with DID direct-inward-dial looks like this:

dial-peer voice 1 pots

  incoming called-number 81690

  voice-port 0:D

  direct-inward-dial

On DID calls, also referred to as one-stage dialing, the setup message contains all the digits necessary to route the call, and the router or gateway should not do subsequent digit collection. When the router or gateway searches for an outbound dial peer, the device uses the entire incoming dial string. This matching is variable-length by default. This match is not done digit-by-digit because by DID definition, all digits have been received. This example helps clarify this concept:

Assume the DID dial-string is "81690". In this case, the router matches dial peer 4 and forwards the complete dial-string "81690".

dial-peer voice 3 voip

destination-pattern 816

session target ipv4:172.22.10.1

!

dial-peer voice 4 voip

destination-pattern 81690

session target ipv4:172.22.10.1

For more information on DID, refer to Voice - Understanding Direct-Inward-Dial (DID) on Cisco IOS Digital (T1/E1) Interfaces.

Non-DID Case

This case is also referred to as two-stage dialing. If DID is not configured on the matched incoming dial peer, the router or gateway enters the digit collection mode (digits are collected inband). Outbound dial peer matching is done on a digit-by-digit basis. The router or gateway checks for dial peer matches after the device has received each digit and then routes the call when a full match is made. These examples help clarify this concept:

Assume the dial-string is "81690". Immediately after the router receives the digit "6", the router matches dial peer 3 and routes the call (forwarding only the digits "816").

dial-peer voice 3 voip

destination-pattern 816

session target ipv4:172.22.10.1

!

dial-peer voice 4 voip

destination-pattern 81690

session target ipv4:172.22.10.1

Now, assume dial peer 3 is configured for wild-card matching:

dial-peer voice 3 voip

destination-pattern 816..

session target ipv4:172.22.10.1

!

dial-peer voice 4 voip

destination-pattern 81690

session target ipv4:172.22.10.1

In this case, the longest-prefix rule applies, and dial peer 4 is matched for the outbound call leg.

Hope this clarifies

//Suresh

Please rate all the useful posts.

//Suresh Please rate all the useful posts.
New Member

Outbound Dial Peer Matching

Hi Suresh

Thanks for taking the time to reply. I think you have answered by question in the first sentence 'when the gateway receives the call from CUCM, it would try to match the entire dial string not digit by digit analysis.'

I have used dial peers for years and not really had any issues using them it was more for clarification. I have been reviewing dial-peers on a number of gateways for SRST purposes ( which im assuming when in SRST will use digit by digit analysis ? ). No were could i find official documentation which detailed that when cucm sends the dialed number to the gateway the entire string is used to match a dial-peer. I knew it was doing as i could see from the debugs i just couldnt confirm in documentation.

Depending on if digit by digit analysis is used for phones when failing over to SRST will determine if i could still have an issue with my dial peers.

Thanks, Carl Ratcliffe

Outbound Dial Peer Matching

Hi Carl, Glad that I could give correct answer to your question.

>> No were could i find official documentation which detailed that when cucm sends the dialed number to the gateway

The dial-peer to/from CUCM is VoIP dial-peer and it has been mentioned in the URL Carlo posted above.

http://www.cisco.com/c/en/us/support/docs/voice/call-routing-dial-plans/14074-in-dial-peer-match.html#topic1

Matching Inbound Dial Peers

Inbound Dial Peers Elements and Attributes

Three information elements sent in the call setup message and four       configurable dial peer command attributes are used to match dial peers as       follows:

  • Inbound POTS dial peers are associated to           incoming POTS call legs on the originating router or gateway.

  • Inbound Voice-Network dial peers are associated           to incoming Voice-Network call legs of the terminating router or gateway.           Examples of Voice-Network calls legs are Voice over IP (VoIP), Voice over Frame           Relay (VoFR), Voice over ATM (VoATM), and Multimedia Mail over IP           (MMoIP).

Matching Outbound Dial Peers

In order to match outbound dial peers, the router       or gateway uses the dial peer destination-pattern       called_number command.

  • On POTS dial peers, the port command is           then used to forward the call.

  • On Voice-Network dial peers, the session           target command is then used to forward the           call.

Also, when outbound peers are matched, there are two cases to consider:       DID case and non-DID.

Please let me know if you have any further questions. I would be happy to assist you.

Kindly mark this thread as 'Answered' if you have got the correct answers to your questions.

//Suresh

Please rate all the useful posts.

                
       
                                     
               
                                                                   
                            
                                                             
                                           

Introduction

The purpose of this document is to explain how inbound and outbound       dial peers are matched to plain old telephone service (POTS) and Voice-Network       call legs.

Prerequisites

Requirements

Cisco recommends that you have knowledge of these topics:

 

Components Used

This document is not restricted to specific software and hardware       versions.

Conventions

Refer to       Cisco       Technical Tips Conventions for more information on document       conventions.

Matching Inbound Dial Peers

Inbound Dial Peers Elements and Attributes

Three information elements sent in the call setup message and four       configurable dial peer command attributes are used to match dial peers as       follows:

  • Inbound POTS dial peers are associated to           incoming POTS call legs on the originating router or gateway.

  • Inbound Voice-Network dial peers are associated           to incoming Voice-Network call legs of the terminating router or gateway.           Examples of Voice-Network calls legs are Voice over IP (VoIP), Voice over Frame           Relay (VoFR), Voice over ATM (VoATM), and Multimedia Mail over IP           (MMoIP).

The four configurable Cisco IOS® dial peer attributes and corresponding       call setup elements are shown here:

    
Dial Peer Attribute Description Call Setup Element                   (See Table 2)
gwy(config-dial-peer)# incoming called-number                     DNIS_string This dial peer command defines the called number destination or                     dialed number identification service (DNIS) string. When properly configured,                     this dial peer command uses the called number to match the incoming call leg to                     an inbound dial peer.Called number (DNIS)
gwy(config-dial-peer)# answer-address                     ANI_string This dial peer command defines the originating calling number                     or automatic number identification (ANI) string. When properly configured, this                     dial peer command uses the calling number to match the incoming call leg to an                     inbound dial peer. Calling Number (ANI)
gwy(config-dial-peer)# destination-pattern                     string When inbound call legs are matched, this command uses the                     calling number (originating or ANI string) to match the incoming call leg to an                     inbound dial peer.                 

Note: For outbound dial peers, this command is matched against the                       called number or DNIS strings.

Calling Number (ANI) for inbound or the                     Called number (DNIS) strings for outbound
gwy(config-dial-peer)# port                     port This dial peer command defines the POTS voice port through                     which calls to this dial peer are placed. Voice Port

The three call setup elements are:

    
Call Setup Element Description
Called number (DNIS) This is the call destination dial string and is derived from                     the ISDN setup message or channel associated signaling (CAS) DNIS.
Calling Number (ANI)This is a number string that represents the origin and is                     derived from the ISDN setup message or CAS ANI. The ANI is also referred to as                     Calling Line Identification (CLID).
Voice PortThis represents the POTS physical voice port.

Inbound Dial Peers Matching Process

When the Cisco IOS router or gateway receives a call setup request, a       dial peer match is made for the incoming call in order to facilitate routing       the call to different session applications. This is not a digit-by-digit match,       rather the full digit string received in the setup request is used to match       against configured dial peers.

Note: The maximum number of dial peers that can be configured on a Cisco           IOS gateway depends on the available memory (DRAM). Each dial peer consumes           approximately 6KB of memory. Make sure that you have at least 20% of the total           memory reserved for other CPU processes. If the dial peers are used for call           routing, a larger number of dial peers will add to the delay to route a call.           This will be significant as the Cisco IOS voice stack looks through dial peers           from the top down, similar to an Acess Control List.

    

The router or gateway matches the information elements in the setup       message with the dial peer attributes to select an inbound dial peer. The router or gateway matches these items in this order:

 
  1. Called number (DNIS) with the incoming           called-number command

    First, the router or gateway attempts to match the called number of           the call setup request with the configured incoming           called-number of each dial peer. Because call setups always           include DNIS information, it is recommended to use the incoming           called-number command for inbound dial peer matching. This           attribute has matching priority over the           answer-address and           destination-pattern commands.

  2. Calling Number (ANI) with the           answer-address command

    If no match is found in step 1, the router or gateway attempts to           match the calling number of the call setup request with the           answer-address of each dial peer. This attribute can           be useful in situations where you want to match calls based on the calling           number (originating).

  3. Calling Number (ANI) with the           destination-pattern command

    If no match is found in step 2, the router or gateway attempts to           match the calling number of the call setup request to the           destination-pattern of each dial peer. For more           information about this, see the first bullet in the Dial Peer Additional Information section of this           document.

  4. Voice-port (associated with the incoming call setup request) with           configured dial peer port (applicable for inbound           POTS call legs)

    If no match is found in the step 3, the router or gateway attempts to           match the configured dial peer port to the           voice-port associated with the incoming call. If multiple dial peers have the           same port configured, the dial peer first added in the configuration is           matched.

  5. If no match is found in the first four steps, then the           default dial peer 0 (pid:0) command is           used.

 

Note: Step 4 is not applicable to voice or dial           platforms such as AS5300, AS5350, AS5400, AS5800 and AS5850. If any one of the           first three steps is not used, then match dial peer 0, and the call is treated           as a dial modem call. This means that customers can get modem tones as opposed           to dial tones for inbound calls.

    

The previous selection process is displayed with this       diagram:

dial_peer_flow.gif

   

The Cisco IOS router or gateway matches only one of these conditions.       It is not necessary for all the attributes to be configured in the dial peer or       that every attribute match the call setup information. Only one condition must       be met for the router or gateway to select a dial peer. The router or gateway       stop to search as soon as one dial peer is matched.

The longest prefix matching criteria applies while each step is       performed. At each step, if multiple matches are found, the one with the       longest explicit match is chosen. This example helps clarify this concept:

Assume the incoming called number (DNIS) is "81690". Dial peer 2 is       matched.

dial-peer voice 1 pots
 incoming called-number 8....
 direct-inward-dial
!

dial-peer voice 2 pots
 incoming called-number 816..
 direct-inward-dial

Note: For inbound dial peers, the session           target command is ignored.

The Default Dial-Peer 0 peer_tag=0, pid:0

If no incoming dial peer is matched by the router or gateway, the       inbound call leg is automatically routed to a default dial peer (POTS or       Voice-Network). This default dial peer is referred to as dial-peer       0 or pid:0.

Note: There is an exception to this statement. Cisco voice and dial           platforms, such as the AS53xx and AS5800, require that a configured inbound           dial peer is matched for incoming POTS calls to be accepted as voice calls. If           there is no inbound dial peer match, the call is treated and processed as a           dial-up (modem) call.

    

Dial-peer 0 (pid:0) has a default configuration       that cannot be changed. The default dial-peer 0 fails to       negotiate non-default capabilities, services, and applications such as:

 
  • Non-default Voice-Network capabilities: dtmf-relay,           no vad, and so forth.

  • Direct Inward Dial (DID)

  • TCL Applications

Dial-peer 0 for inbound VoIP peers has this       configuration:

  • any codec

  • vad enabled

  • no rsvp support

  • fax-rate voice

    Note: The default DSCP for voice is EF codepoint 101110 (RFC 2598), and             the default DSCP for signaling is AF31 codepoint 011010 (RFC 2597). The default             dial peer does not mark packets to DSCP 0. All voice packets on the routers are             marked by default (this can be overridden by the dial peer), signaling with             AF31 and media with EF. Calls that match the default dial peer 0 should also             have this behavior.

Dial-peer 0 (pid:0) for inbound POTS peers has       this configuration:

  • no ivr application

For further explanation of this concept, see the       Case Study: Understanding Inbound Matching and Default       Dial-Peer 0 section of this document.

Special Note on isdn overlap-receiving

There are implications for inbound dial peer matching when the       isdn overlap-receving command is configured on ISDN       interfaces. After every digit is received at the ISDN layer, dial peers are       checked for matches. If a full match is made, the call is routed immediately       (to the session app in this case) without waiting for additional digits. The       'T' terminator can be used to suspend this digit-by-digit       matching and force the router or gateway to wait until all digits are received.       The 'T' refers to the T302 interdigit timer at the ISDN level, configurable       under the serial interface associated with the ISDN interface. ISDN also       provides other mechanisms to indicate the end of digits, such as setting the       Sending Complete Information Element (IE) in Q.931 information messages.

Special Note on POTS Calls with Empty Calling Number Field

Assume this configuration:

dial-peer voice 1 pots
   destination-pattern 9T
   port 1/0:1

Now, assume that an incoming call arrives with no calling number       information and is matched with the POTS dial peer based on the       destination-pattern 9T command. In this case, the       Cisco IOS router or gateway uses the "9" digit as the calling number and       forwards the call to the corresponding device, such as CallManager or the IOS       Gateway. In order to not replace the empty calling number field, create a dummy       POTS dial peer with just the incoming called-number command configured. Because the incoming       called-number statement has higher priority than       destination pattern for inbound POTS matching,       dial-peer voice 2 becomes the POTS dial peer used.

dial-peer voice 1 pots 
    destination-pattern 9T
    port 1/0:1
!
dial-peer voice 2 pots
    incoming called-number .

Special Note on Empty Called Number

The Warning message shown here, which displays when dial-peer is       configured with incoming called-number T, might raise questions in regards to       the dial-peer selection with an empty called number from an actual       router.

RTR(config)#dial-peer voice 1 pots
RTR(config-dial-peer)#incoming called-number T 

Warning: Pattern T defines a match with zero or more digits and hence could 
match with an empty number.  If this is not the desired behaviour please 
configure pattern .T instead to match on one or more digits
RTR(config-dial-peer)#

Incoming dial-peer match with an empty called number:

 
  • A "null" called-number is considered "less" qualified compared to a           port number and/or in some cases answer-address. Therefore, a match based on a           "null" called number will occur ONLY if there is no match based on either           answer-address or port-number.

  • In case of overlap dialing, a "null" called number will not match           "incoming called-number T" because timeout has not occurred.

  • A "null" called-number will match "incoming called-number T" only in           case of ENBLOCK and there is no match either because of answer-address and           port-number. The warning you see when you configure "incoming called-number T"           refers to this specific case.

Matching Outbound Dial Peers

In order to match outbound dial peers, the router       or gateway uses the dial peer destination-pattern       called_number command.

 
  • On POTS dial peers, the port command is           then used to forward the call.

  • On Voice-Network dial peers, the session           target command is then used to forward the           call.

Also, when outbound peers are matched, there are two cases to consider:       DID case and non-DID.

//Suresh Please rate all the useful posts.
New Member

Re:Outbound Dial Peer Matching

Hi and thanks for your reply again. I think were I'm getting confused is did. I have read the link several times and am happy with the process except did is used on an inbound pots dial peer which then matches an outbound voip or pots dial peer so 1stage dialling.

A call from cucm matches a voip inbound dial peer it then has to match an outbound dial peer. Voip inbound dial peers don't have did configured so I'm assuming this is done automatically and an outbound dial peer is matched from the called number in the setup message. It was this bit I was querying about how the outbound dial peer digit matching was done.

Thanks, Carl Ratcliffe


Sent from Cisco Technical Support Android App

Outbound Dial Peer Matching

Hello Carl, the direct-inward-dial (DID) command is effective for POTS dial peer that too Inbound direction.

PSTN--- -->E1-PRI------->Gateway(H323/SIP)------>CUCM----->IP Phone.

when the call comes in from PSTN to IP phone, the GW checks whether or not the DID is configured on the inbound dial-peer. If yes, it is called  one stage dialing and the entire called number (ex:12345) is matched against the outbound voip dial-peer (dial-peer to CUCM is a voip dial-peer).

if the called number is 12345, and 2 outbound voip dial peers to CUCM as below

dial-peer voice 1 voip
 destination-pattern 123
 session target ipv4:
!
dial-peer voice 2 voip
 destination-pattern 12345
 session target ipv4:

dial-peer voice 3 pots
description Inbund dial-peer from PSTN
incoming called-number 12345 voice-port 0/0/0:15 direct-inward-dial

In the config above, dial-peer 2 will be matched to send the call to CUCM.

if DID is not configured on the inbound dial-peer, then the outbound dial-peer matching is done digit by digit.

So when though the user dials 12345, As soon as digit 3 is receied, it will match dial-peer 2 because of
destination-pattern 123

as a conclusion: If DID is configured on the inbound pots dial-peer, then outbound dial-peer matching is against the entire (enbloc) called number and not digit by digit.

If DID is not configured, then outbound dial-peer matching is against the digit by digit called number

please let me know if you have any questions, I would be glad to answer that.

//Suresh

Please rate all the useful posts.

//Suresh Please rate all the useful posts.
New Member

Re:Outbound Dial Peer Matching

Thanks for your help, that's great information.


Sent from Cisco Technical Support Android App

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