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Why unsupport BRI on Mobile Connect?

Answered Question
Oct 25th, 2010
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I plan to use "mobile connect" feature for big UC customer.


But, "mobile connect" is able to use only T1-PRI, written by CUCM SRND.
I plan to use BRI at a lot of branches, and tested no problems.
Why unsupport of BRI? What's problems? What's going to happen?


And so, CUCM Express is support BRI.


Cisco Unified Communications Manager Express System Administrator Guide
http://www.cisco.com/en/US/docs/voice_ip_comm/cucme/admin/configuration/guide/cmesnr.html

Single Number Reach
   :
Remote destinations may include the following devices:
-Mobile (cellular) phones.
-Smart phones.
-IP phones not belonging to the same Cisco Unified CME router as the desktop phone.
-Home phone numbers in the PSTN. Supported PSTN interfaces include PRI, BRI, SIP, and FXO


Why support BRI on CUCM Express?

rgds,


Kazuki "amigo" Nakagawa

Correct Answer by paolo bevilacqua about 6 years 9 months ago

srsivara wrote:


This is the information I got from the developers :


...


The problem with BRI is there is no guarantee that answer/disconnect indication  can be provided in a timely manner.  Certainly there are configurations that can  be used get this working, but  the configuration varies widely from IOS version to IOS version as well as based  on provider network.  PRI is the only type of TDM connection that provides  consistent answer/disconnect indication across all versions of IOS and all  provider networks.



- Sriram


The developers you spoke to should research more before making such incorrect statements.

BRI support for all and any ISDN feature like disconnect supervision, and more. BRI is 100% equivalent to PRI, in every country of the world, since the day ISDN was introduce 20 years ago,


To be more clear, under layer 2 and 3 aspects, PRI and BRI are 100% identical, and only differ in the number of channel supported.


When I was working at Cisco, that was (of  course) perfectly understood. It is worring to learn that this kind of misunderstaing now resides in some engineering people.

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paolo bevilacqua Mon, 10/25/2010 - 02:40
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Possibly due to lack of testing.


BRI should work as well as PRI.

amigo Tue, 10/26/2010 - 11:49
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Thanks for res.


I experimented with "Mobile Connect" on BRI, and succeeded.

I think that MC on BRI is in demand more and more.

However, I expectation that TAC help us in a negativity when any troubles occur.

Because it is written that it doesn't support it to the SRND or some manuals.

If what we do, does Cisco and TAC admit?

Is there a person who has the case and the experience actually used with MC on BRI?

srsivara Tue, 10/26/2010 - 12:36
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This is the information I got from the developers :


In a nutshell, the limitation is related to connect/disconnect supervision.   Without a PRI, CUCM has no ability to determine whether the Remote Destination  has answered or terminated the call.  CUCM must have the ability to determine  this in order to stop ringing the desk phone and/or other configured Remote  Destinations as well as to take a call back from the PSTN if the Remote  Destination answers too soon.  The latter is necessary for Single Enterprise  Voicemail Box feature and is based on the Answer Too Soon Timer, such that  should a Remote Destination mobile phone be out of range or turned off, we don't  want the call rolling to mobile VM - instead we take the call back and continue  to only ring the desk phone until it rolls to enterprise VM.  Furthermore we  also need connect/disconnect supervision in order to support the Desk Phone  Pickup feature, such that the user can move an in-progress Mobile Connect at  their mobile phone to their desk phone.  In addition, PRIs provide callerID  support which is required for Mobile Voice Access and Enterprise Feature Access  2-Stage Dialing features because these features depend on inbound callerID  matching for Remote Destination phones to function.


The problem with BRI is there is no guarantee that answer/disconnect indication  can be provided in a timely manner.  Certainly there are configurations that can  be used get this working, but  the configuration varies widely from IOS version to IOS version as well as based  on provider network.  PRI is the only type of TDM connection that provides  consistent answer/disconnect indication across all versions of IOS and all  provider networks.


I don't know how CME handles SNR - so can't comment on why CME can support SNR over BRI. However, Unified CM and CME are different applications, so differences in support are not  unusual.


- Sriram

Correct Answer
paolo bevilacqua Tue, 10/26/2010 - 13:39
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srsivara wrote:


This is the information I got from the developers :


...


The problem with BRI is there is no guarantee that answer/disconnect indication  can be provided in a timely manner.  Certainly there are configurations that can  be used get this working, but  the configuration varies widely from IOS version to IOS version as well as based  on provider network.  PRI is the only type of TDM connection that provides  consistent answer/disconnect indication across all versions of IOS and all  provider networks.



- Sriram


The developers you spoke to should research more before making such incorrect statements.

BRI support for all and any ISDN feature like disconnect supervision, and more. BRI is 100% equivalent to PRI, in every country of the world, since the day ISDN was introduce 20 years ago,


To be more clear, under layer 2 and 3 aspects, PRI and BRI are 100% identical, and only differ in the number of channel supported.


When I was working at Cisco, that was (of  course) perfectly understood. It is worring to learn that this kind of misunderstaing now resides in some engineering people.

srsivara Tue, 10/26/2010 - 13:56
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Thanks for the information, Paolo. Will need to revisit the topic with the developers - will update the thread if I get any updates.


- Sriram

paolo bevilacqua Tue, 10/26/2010 - 14:50
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You are welcome, and thank you for moving the matter forward with your contacts.

James Hawkins Tue, 10/26/2010 - 14:51
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Just thought it was worth posting the relevent section of the CUCM SRND relating to this.



The following guidelines and restrictions apply with regard to  deployment and operation of Mobile Connect within the Unified CM  telephony environment:


  • Mobile  Connect is supported only with PRI TDM PSTN connections. T1 or E1-CAS,  FXO, FXS, and BRI PSTN connections are not supported. This PRI  requirement is based on the fact that Cisco Unified CM must receive  expeditious answer and disconnect indication from the PSTN in order to  ensure full feature support. Answer indication is needed in order for  Cisco Unified CM to stop ringing the desk phone and other remote  destinations when a Mobile Connect call is answered at a particular  remote destination. In addition, answer indication is required in order  to support the single enterprise voicemail box feature. Finally,  disconnect indication is required for desk phone pickup. A PRI PSTN  connection will always provide answer or disconnect indication.

  • Mobile  Connect is also supported over SIP trunk VoIP PSTN connections as long  as the Cisco IOS Unified Border Element provides the demarcation point  between the Unified CM SIP trunk and the service provider trunk and as  long as mid-call features (or other DTMF-dependent features) are not in  use. Mid-call features are not supported over VoIP PSTN connections. A  VoIP-based PSTN connection is still able to provide expeditious answer  and disconnect indication to Unified CM due to the end-to-end signaling  path provided by VoIP-based PSTN connections.


Possibly SIP trunks could be an option for the OP?


As an aside I have a customer successfully running Mobile Connect with outbound calls being routing via a Quescom GSM300 gateway.

amigo Tue, 10/26/2010 - 21:56
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I wish to express my gratitude for a great discussion and information.

In Japan, FMC service and the cellular phone fixed amount menu are spreading in businesses, the compatibility of these and Mobile Connect feature is very good. Any FMCs and fixed amount are regularity supported PRI,BRI, and FXO. SIP for some services. PSTN Connection (on Cisco UC) have to use PRI/BRI combination. I wish for authoritative support of MC on BRI.

srsivara Wed, 10/27/2010 - 06:29
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  • Mobile   Connect is supported only with PRI TDM PSTN connections. T1 or E1-CAS,   FXO, FXS, and BRI PSTN connections are not supported. This PRI   requirement is based on the fact that Cisco Unified CM must receive   expeditious answer and disconnect indication from the PSTN in order to   ensure full feature support. Answer indication is needed in order for   Cisco Unified CM to stop ringing the desk phone and other remote   destinations when a Mobile Connect call is answered at a particular   remote destination. In addition, answer indication is required in order   to support the single enterprise voicemail box feature. Finally,   disconnect indication is required for desk phone pickup. A PRI PSTN   connection will always provide answer or disconnect indication.


What do you think of this section, Paolo ? In my opinion, it seems to imply that non-PRI, including BRI, doesn't help in immediate supervision disconnects (which is not true for BRI).


- Sriram

paolo bevilacqua Wed, 10/27/2010 - 06:44
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What do you think of this section, Paolo ? In my opinion, it seems to imply that non-PRI, including BRI, doesn't help in immediate supervision disconnects (which is not true for BRI).


Correct, and that is common knowledge among voice engineers, so it's a surprising inaccuracy to find in an official SRND.

amigo Fri, 10/29/2010 - 11:50
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Similar descriptions also in the CUCM Features and Services Guide,

   :

Gateways and Ports

Only H.323 VoIP gateways get supported for Mobile Voice Access.

Mobile Connect features do not get supported for T1 CAS, FXO, FXS and BRI.


Mobile Connect Support Restrictions

The Mobile Connect feature gets supported only for Primary Rate Interface (PRI) public switched telephone network (PSTN) connections.

For SIP trunks, Mobile Connect gets supported via IOS gateways or intercluster trunks.

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