How to configure Eventlist BLF

  • Updated on March 3, 2022

Although SIP protocol (RFC3261) was not providing the semantics to support the Busy Lamp Field (BLF) there’s a way around to make the Busy Lamp Field function works on our phone by using the proper instantiation and the appropriate extension of the SIP Specific Event Notification framework (RFC3265). RFC4235 – Dialog Event Package is the instantiation RFC3265 which defined the mechanism of how the endpoint can subscribe for the status of any dialog including another endpoint. The Busy Lamp Field feature is useful but can create a lot of overhead when trying to subscribe for the status of a large number of the resources. Event List BLF or BLF resource list is the solution to solve the overhead problem by reducing the number of requests. Instead of generating an individual SUBSCRIBE request for each resource status, the concept of the Event List is combining all of those requests into a single request that queries the status of the resources from the Event List. RFC4662 – Resource List defines an aggregating mechanism that allows for subscribing and notifying for a list of resources. This mechanism is useful when the device needs to subscribe to a large number of resources. The overhead of generating individual SUBSCRIBE requests and the overhead of processing individual NOTIFY requests can be reduced by aggregating resources using a resource list concept.

This document serves as an end-user guide on how to configure Grandstream GXP21xx/17xx/16xx Enterprise IP phones for the UCM Eventlist BLF feature. And How to configure the BLF list on Grandstream UCM and apply them on the GXP phones.

OVERVIEW

Grandstream GXP21xx/17xx/16xx Enterprise IP Phones support both Grandstream UCM Busy Lamp Field and EventList BLF features and allow end-users, such as attendants, to monitor the call status of users in the list. GXP21xx/17xx/16xx supports this feature by sending out the subscription request to the UCM and changing the indicator status of the Line keys, MPKs, or virtual MPKs associated with the monitored users. Additionally, the phone is also able to pick up the calls to the monitored extensions by using a pre-defined feature code called BLF- Call-pickup Prefix.

Available Programmable Keys on each Model

Model/KeyLine KeysOnboard MPKsExtension Board MPKsVPKs

GXP2130

X

X

X

GXP2140

X

X

X

GXP2160

X

X

X

GXP2170

X

X

X

GXP1760

X

X

GXP1780

X

X

GXP1782

X

X

GXP1610

X

X

GXP1615

X

X

GXP1620

X

X

GXP1625

X

X

GXP1628

X

X

X

GXP1630

X

X

X

HOW EVENTLIST BLF WORKS

Subscribe

According to the RFC4662 – Resource List, UCM must allow no more than 20 endpoints to subscribe to the single resource list. However, in practice, only a single endpoint will subscribe to a particular EventList.

In the first step, the endpoint will send a SUBSCRIBE request to the configured EventList URI as per RFC3265. The main goal of this subscription is to obtain the state information of all endpoints that are associated with the Event List.

In order to subscribe for the Event List, it is necessary that the phone includes the “eventlist” tag in the supported header, and in most cases, the Authorization header is also required.

Via: SIP/2.0/UDP 192.168.40.119:5060;branch=z9hG4bK341324999;rport

From: <sip:5000@192.168.40.170>;tag=1620181217

To: <sip:170BLF@192.168.40.170>

Call-ID: 1469406960-5060-2@BJC.BGI.EA.BBJ

CSeq: 20001 SUBSCRIBE

Contact: <sip:5000@192.168.40.119:5060>

Authorization: Digest username="5000", realm="Grandstream", nonce="509e9f25", uri="sip:170BLF@192.168.40.170", response="47c40eb60804fff79e3478e327145432", algorithm=MD5

X-Grandstream-PBX: true

Max-Forwards: 70

User-Agent: Grandstream GXP2170 1.0.11.35

Expires: 3600

Supported: replaces, path, timer, eventlist

Event: dialog

Accept: application/dialog-info+xml,multipart/related,application/rlmi+xml

Allow: INVITE, ACK, OPTIONS, CANCEL, BYE, SUBSCRIBE, NOTIFY, INFO, REFER, UPDATE, MESSAGE

Content-Length: 0

Notify

Upon the successful subscription, the UCM will reply to the Event List initial status information in form of the NOTIFY message that contains the state and other information of each endpoint on the Event List in the XML format. In normal cases, each NOTIFY will contains the information of 3 endpoints. Therefore, it is normal to have a set of NOTIFYs from the UCM even if the user only subscribes for a single Event List.

Content-Transfer-Encoding: binary

Content-ID: <5000@192.168.40.170>

Content-Type: application/dialog-info+xml;charset="UTF-8"




<?xml version="1.0" encoding="UTF-8"?>

<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" version="2" state="full" entity="sip:5000@192.168.40.170">

<dialog id="5000">

    <state>terminated</state>

    <local>

      <identity display="John Smith">sip:5000@192.168.40.170</identity>

    </local>

  </dialog>

</dialog-info>




Content-Transfer-Encoding: binary

Content-ID: <5001@192.168.40.170>

Content-Type: application/dialog-info+xml;charset="UTF-8"




<?xml version="1.0" encoding="UTF-8"?>

<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" version="2" state="full" entity="sip:5001@192.168.40.170">

  <dialog id="5001">

    <state>offline</state>

    <local>

      <identity display="David Jackson">sip:5001@192.168.40.170</identity>

    </local>

  </dialog>

</dialog-info>




Content-Transfer-Encoding: binary

Content-ID: <5002@192.168.40.170>

Content-Type: application/dialog-info+xml;charset="UTF-8"




<?xml version="1.0" encoding="UTF-8"?>

<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" version="3" state="full" entity="sip:5002@192.168.40.170">

  <dialog id="5002">

    <state>terminated</state>

    <local>

      <identity display="William Thompson">sip:5002@192.168.40.170</identity>

    </local>

  </dialog>

</dialog-info>

Endpoint States

  • Terminated

When there is no active call for a specific endpoint or when a call to or from a subscribed endpoint is just being released, then the endpoint is considered idle/terminated.

  • If applicable, the LED for the associated endpoint should be solid green or background should be solid green for the related VMPKs.
  • Early

When an incoming call arrives for a subscribed endpoint, the endpoint is considered ringing/in the early state.

  • If applicable, the LED for the associated endpoint should be blinking red or background should be solid red for the related VMPK.
  • Confirmed

When a call is originated from a subscribed endpoint or a subscribed endpoint answered the call, then the resource is said to be in the “active” state.

  • If applicable, the LED for the associated endpoint should be solid red or background should be solid red for the related VMPK.
  • Offline

The subscription for that endpoint is failed or unreachable.

  • If applicable, the LED for the associated endpoint should be off or background should be solid grey for the related VPK.

CREATING A BLF EVENT LIST ON GRANDSTREAM UCM

Grandstream UCM supports and allows creating an Event List for Busy Lamp Field (BLF) monitoring purposes. To create a list, login into the UCM and follow the below steps:

  1. Go to Call Features 🡪 Event List.
  2. Click “Add Event List” to start creating a new list.
Create new Event List

Enter the unique URI of the Event List in the URI field followed by choosing either “dialog” or “presence” Event List (subscribers must carry the same value in the Event header).

Event List URI
  1. Select the accounts (endpoint) to be monitored from the both available local and remote extensions. then click on the right arrow head to move them to the “selected” column.
Event List Account selection
  1. You can add extensions which are not in the list under the “Special Extensions” field.
Special Extensions
  1. Click “Save” to complete the Event List BLF creation.

If the new Event List is successfully created, it should be showing on the Event List table:

Event List Table
  1. Apply Changes

Notes:

  • Click on to edit the Event List configuration.
  • Click on to delete the Event List.
  • Once properly configuring the Event List on a GXP a new section will appear, labeled “Member of Subscribers”. Where users can Select one Event List to show its subscribers.
Member of Subscribers

PROVISION THE EVENT LIST BLF ON THE PHONE

Configuring the GXP21xx/GXP17xx/GXP16xx Enterprise IP Phones to work with Grandstream UCM Event List BLF feature is straightforward.

  1. First configure your SIP account settings.
Configure the SIP Account Settings
  1. Choose the provisioning method under Settings 🡪 Call Features: “Auto Provision List Starting Point”.
Event List BLF provisioning method GXP21xx
  • Select “Extension Boards” or “VPK” to be used first when the phone is being automatically provisioned with Event List BLF. The default setting is “Extension Boards”.

Note:

  • GXP2130/GXP2160: Need to set “Auto Provision List Starting Point” to “MPK” (Default setting is VPK) to make the provision work.
Event List BLF provisioning method on GXP2160/2130
  1. Fill in the BLF URI under Account X 🡪 SIP Settings 🡪 Advanced Features.
  • Enter the URI (name) of the Event List BLF that you just created on the Grandstream UCM.
  • Enable Auto Provision Event List BLFs (Recommended) to automatically assign the BLF extensions into the available MPKs/VMPKs slots.
Event List BLF URI Settings
  1. In the case that Auto Provision Event List BLF was disabled:
  2. Users can manually configure the MPKs on the extension Boards (GXP2140/2170) to monitor the BLF extension. Under Settings 🡪 Extension Boards 🡪 EXTx: For each MPK, user needs to select “Event List BLF” as Mode, choose the specified Account, and enter the Value of each extension in the list. After saving and rebooting, the UCM extensions will be logged on the extension board, and the phone will start to monitor the extensions status.
Extension Board Settings
  1. If the phone doesn’t support the extension board. Event List BLF still can be configured on Line Keys: Go to Settings 🡪 Programmable Keys 🡪 Programmable Keys, then configure each line accordingly.
Configure Event List BLF on Line Keys

The Event List BLF can also be configured on MPKs and VPKs:

  1. To configure the Event List BLF on MPKs: Go to Settings 🡪 Programmable Keys 🡪 Multi-Purpose Keys.
Configure Event List BLF on MPKs
  1. To configure the Event List BLF on VPKs:
    Go to Settings 🡪 Programmable Keys 🡪 Virtual Multi-Purpose Keys: Click “Add VPK” to Select the “Mode”, the “Account” and enter the “Value”. Then “Save”.
Edit VPK
Configure Event List on VPKs

VISUAL INDICATORS

Grandstream GXP21xx/17xx/16xx Enterprise IP Phones are able to notify the end-user of the call status of the monitored extension by turning on the LEDs or changing the background colors.

For example, if the monitored extension is ringing, the BLF indicator status will be changed from solid green to blinking red; and if the monitored extension answers the call, the BLF indicator status will be changed from blinking red to solid red.

The following table shows the BLF indicator status in different scenarios:

Monitored Extension Behavior

VMPK (BLF Background Status for GXP21xx)

LINE Keys/MPKs (LED Indicator Status)

Extension Board Key Status (Only for MPK Extension Supported Models)

Idle

Solid green

Solid green

Solid green

Placing a call

Solid red

Blinking green

Blinking green

Ringing

Solid red

Blinking red

Blinking red

During a call

Solid red

Solid red

Solid red

Hold the call

Solid red

Solid red

Solid red

Call Park

Solid red

Blinking red

Blinking red

Monitored extension not registered/BLF subscription failed

Solid grey

Off

Off

DIRECTED CALL PICKUP

The directed call pickup feature allows the GXP/21xx/17xx/16xx phone system to answer the calls to the monitored users. This feature is very useful for the attendant to be able to answer calls if the callees are not available.

For the Grandstream UCM system, it requires to dial the specified prefix ahead of the monitored extension to direct pick up the call. Thus, the end-user must configure the BLF Call-pickup Prefix for GXP21xx/17xx/16xx in order to use this feature.

The following screenshot shows that (**) is configured as the prefix under the Account X 🡪 SIP Settings 🡪 Advanced Features 🡪 BLF Call-pickup Prefix.

Configure BLF Call Pickup Prefix for GXP21xx
Configure BLF Call Pickup Prefix for GXP17xx/GXP16xx

Then, when the monitored user’s indicator shows an incoming call signal, the GXP21xx/17xx/16xx phones user can press the BLF button to answer/pick up the call.

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