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Target release	1.0
Epic
Document status
Document owner	Alexander Feldt
Designer	Zsolt Erdei
Developers	Clemens Cramer
QA	Tita Petre

Goals

The current BLF and Extension mapping implementations for D8xx IP phone series are similar, but with a few differences and partly erroneous behaviour. Therefore, it is desired to align both implementations by using XML definitions instead. Furthermore, the requirements should be re-defined to communicate a clear result.
- Avoid confusion for customers
- Improve user experience
- Improve performance

Background and strategic fit

BLF is a valuable feature for Snom customers, like enterprises who are looking to assist in connecting their customers to a live, available person as well as save business phone use time. Overall, it enables businesses to streamline their communication and better serve customers. BLF aka Extension monitoring has been utilized in numerous ways by businesses using Snom phone systems with multiple extensions.

Use cases

Use case#1: A secretary's phone shall display the call status of the boss's line, allowing the secretary to know whether the boss is on a phone call or not. This will enable the secretary to make the decision to put the new caller on hold or let them through to the boss.
Use case#2: Call centers and customer support groups have also a need for BLF: it enables employees to see if their colleagues are free to take a support call or if their supervisor is on another line and unable to help another customer.
Use case#3: BLF is needed by teams working on a specific project: supervisors can monitor team members' extensions and vice versa so all team members are aware of each other's current status.

Preconditions

On Snom IP phones acting as UAS, any SIP extension having an active subscription of its state changes, shall sent a notification SIP message (NOTIFY) to the UAC, when one of the following state changes occur:

from any state => terminated
from any state => trying
from any state => early/proceeding
from any state => confirmed

The NOTIFY XML body must contain the necessary information for the UAC to perform state translation and visualization.

Requirements

#

Requirement title

Functionality

Importance

Implementation status

1

D8XX:PFK-mapping:BLF-XML:General-Functionality

On D8xx IP phones, any PFK (programmable function key - physical or virtual) can be assigned to a key type called "BLF-XML", and a key number, which corresponds to a SIP extension on another IP phone in the same VoIP environment. The following specific functionality is required:

Monitoring states of the configured SIP extension
Quick-dial to the configured SIP extension in idle state
Pick-up an incoming call to the configured SIP extension

2

D8XX:PFK-mapping:BLF-XML:Configuration

The assignment shall be configured either manually via web user interface (WUI) and/or phone user interface (PUI), and automatically via auto-provisioning (HTTP/TFTP setting server), SRAPS, or remote management (TR-069).

3

D8XX:PFK-mapping:BLF-XML:Subscription

The assignment shall initiate the SIP subscription process according to RFC 3265.

4

D8XX:PFK-mapping:BLF-XML:Monitoring:Translation

Dialog states of the configured SIP extension shall be monitored, processed, and translated according to its direction.

UAS state	Dialog state (NOTIFY)	Direction	Translated state
idle mode	terminated/none of the below mentioned	-	idle
offhook	trying	initiator	offhook
incoming call ringing	early/proceeding	recipient	ringing
incoming call accepted	confirmed	recipient	talking
outgoing call ringing	early/proceeding	initiator	calling
outgoing call accepted	confirmed	initiator	talking

5

D8XX:PFK-mapping:BLF-XML:Actions

When the PFK is pressed, the following actions are allowed according to the translated state

Translated state	idle	offhook	calling	ringing	talking
Allowed actions	Quick-dial	?	?	Pick-up	?

6

D8XX:PFK-mapping:BLF-XML:Monitoring:Visualization

On D8xx series, during an active subscription, state changes of the monitored SIP extension shall be visualized on both, PFK LED and PFK label.

7

D8XX:PFK-mapping:BLF-XML:Monitoring:Visualization:LED

The PFK LED behaviour and colour shall be according to the translated state:

Translated state	idle	offhook	calling	ringing	talking
LED behaviour	off	on	on	blinking	on
LED colour	-	red	red	red	red

8

D8XX:PFK-mapping:BLF-XML:Monitoring:Visualization:Label:Areas

The PFK label shall be composed of 3 areas:

(A) icon area	(B) name area
	(C) state area

9

D8XX:PFK-mapping:BLF-XML:Monitoring:Visualization:Label:icon-area

The label icon area (A) shall contain an icon and colour according to the translated state

Translated state	idle	offhook	calling	ringing	talking
Icon (suggestion from fkey_icons)
Name	kIconTypeFkeyBlfIdle	kIconTypeFkeyBlfOffhook	kIconTypeFkeyBlfCalling	kIconTypeFkeyBlfRinging	kIconTypeFkeyBlfTalking
Colour	grey/white	red	red	yellow	red

10

D8XX:PFK-mapping:BLF-XML:Monitoring:Visualization:Label:name-area

The label name area (B) shall contain a text derived from display name or number (configurable) according to translated state and direction. Depending on the available space, the text shall be scrolled.

Translated state	idle	offhook	calling	ringing	talking
Direction	-	initiator	initiator	recipient	initiator	recipient
Text (based on target)	local	local >	local > remote	remote > local	remote <> local	local <> remote
Text colour	white	white	white	white	white	white
Example (using number)	101	101 >	101 > 102	102 > 101	102 <> 101	101 <> 102
Example (using display name)	Alex	Alex >	Alex > Alice	Alice > Alex	Alice <> Alex	Alex <> Alice

11

D8XX:PFK-mapping:BLF-XML:Monitoring:Visualization:Label:state-area

The label state area (C) shall contain a text and colour representing the translated state

Translated state	idle	offhook	calling	ringing	talking
text	idle	offhook	calling	ringing	talking
colour	white	white	white	white	white

Software Requirement Specification (SRS)

Based on user interactions, the UAS sends SIP NOTIFY messages to the UAC. By means of XML definitions, the information in the SIP NOTIFY XML body are translated into variables, that are known to the UAC phone application and can be processed to show the desired results.

Interactions

SIP NOTIFY XML body

XML definition

Display

UAS

UAS => UAC

UAC translation rules

Complete rule set

PFK LED & label (number)

PFK LED & label (display name)

goes offhook

dialog state => trying

NOTIFY
...
<?xml version="1.0"?>
<dialog-info
	xmlns="urn:ietf:params:xml:ns:dialog-info"
	version="..."
	state="full"
	entity="sip:101@...">
	<dialog id="..." >
		<state>trying</state>
	</dialog>
</dialog-info>

translate state => offhook

quick dial not allowed
pick-up not allowed

...
<NotifyParsingRules type="state">
	...
  	<level3
		translates_to="offhook">/dialog-info/dialog/state[.="trying"]
	</level3>
  	...
</NotifyParsingRules>
...
<action>
	<invite target="$(subscr_uri)"
		when="on press"
		states="idle"/>
	<invite target="$(remote_uri)"
		when="on press"
		state="ringing"
		request_uri="$(remote_uri)"
		replaces="$(call_id);to-tag=$(remote_tag);from-tag=$(local_tag)"/>
</action>

<ReplacementPlan>
	<!-- This defines the name of the entry in the Function Keys page under Type -->
	<key id="BLF-new">
	<general type="BLFSampleDefinition" />
		<initialization>
 		<!-- only add the UAS IP here, extension number is replaced from WUI as variable $(ui_argument) -->
		<variable name="subscr_proxy" value="10.110.22.35"/>
		<!-- initial value for the state variable: off means, that after bootup this button has state off -->
		<state value="off"/>
		</initialization>
		<!-- a subscription of event-type dialog will be initiated to the URI defined -->
		<subscription type="dialog" to="<sip:$(ui_argument)@$(subscr_proxy)>" for="$(ui_argument)@$(subscr_proxy)"/>
		<!-- checks if a SIP NOTIFY message belongs to this particular button
		level is ok, if the condition inside the tags is matched -->
		<NotifyParsingRules type="applies">
			<level1 translates_to='OK'>/dialog-info[@entity="sip:$(ui_argument)@$(subscr_proxy)"]</level1>
		</NotifyParsingRules>
		<!-- translates the button state based on the body of the SIP NOTIFY -->
		<NotifyParsingRules type="state">
			<level1 translates_to="ringing">/dialog-info/dialog/state[.="early"]</level1>
			<level1-1 translates_to="calling">/dialog-info/dialog[@direction="initiator"]</level1-1>
			<level2 translates_to="ringing">/dialog-info/dialog/state[.="proceeding"]</level2>
			<level2-1 translates_to="calling">/dialog-info/dialog[@direction="initiator"]</level2-1>
			<level3 translates_to="offhook">/dialog-info/dialog/state[.="trying"]</level3>
			<level4 translates_to="talking">/dialog-info/dialog/state[.="confirmed"]</level4>
			<level5 translates_to="idle"/>
		</NotifyParsingRules>
		<!-- Call pickup: fetch variable call_id from call-id of NOTIFY body -->
		<NotifyParsingRules type="variable" id="call_id" state="ringing">
			<level1 fetch_attribute="call-id">/dialog-info/dialog[@call-id]</level1>
        </NotifyParsingRules>
		<!-- Call pickup: fetch variable remote_tag from remote-tag of NOTIFY body -->
		<NotifyParsingRules type="variable" id="remote_tag" state="ringing">
			<level1 fetch_attribute="remote-tag">/dialog-info/dialog[@remote-tag]</level1>
		</NotifyParsingRules>
		<!-- Call pickup: fetch variable local_tag from local-tag of NOTIFY body -->
		<NotifyParsingRules type="variable" id="local_tag" state="ringing">
			<level1 fetch_attribute="local-tag">/dialog-info/dialog[@local-tag]</level1>
		</NotifyParsingRules>
		<!-- Call pickup: fetch variable remote_uri from uri of NOTIFY body -->
		<NotifyParsingRules type="variable" id="remote_uri" state="ringing">
			<level1 fetch_attribute="uri">/dialog-info/dialog/remote/target[@uri]</level1>
		</NotifyParsingRules>
		<action>
		 	<!-- Quick dial: depending in which states we want to allow this action -->
            <invite target="$(ui_argument)" when="on press" states="calling, talking, offhook, idle"/>
 		 	<!-- Pick up --> 
            <invite target="$(remote_name)<$(remote_uri)>" when="on press" state="ringing" request_uri="$(remote_uri)" replaces="$(call_id);to-tag=$(remote_tag);from-tag=$(local_tag)"/>
			<!-- change icon on NOTIFY and translated state idle -->
			<assign when="on notify" state="idle">
   				<source value="kIconTypeFkeyBlfIdle"/>
   				<destination id="icon"/>
 			</assign>
    		 <!-- change icon on NOTIFY and translated state offhook -->
			<assign when="on notify" state="offhook">
   				<source value="kIconTypeFkeyBlfOffhook"/>
   				<destination id="icon"/>
 			</assign> 
			<!-- change icon on NOTIFY and translated state ringing -->
			<assign when="on notify" state="ringing">
   				<source value="kIconTypeFkeyBlfRinging"/>
   				<destination id="icon"/>
			</assign>
   		 	<!-- change icon on NOTIFY and translated state calling -->
			<assign when="on notify" state="calling">
   				<source value="kIconTypeFkeyBlfCalling"/>
   				<destination id="icon"/>
			</assign>
   		 	<!-- change icon on NOTIFY and translated state talking -->
			<assign when="on notify" state="talking">
   				<source value="kIconTypeFkeyBlfTalking"/>
   				<destination id="icon"/>
			</assign>
		</action>
    </key>
</ReplacementPlan>

🔴		101 >
		offhook

🔴		Alex >
		offhook

goes onhook

dialog state => terminated

NOTIFY
...
<?xml version="1.0"?>
<dialog-info
	xmlns="urn:ietf:params:xml:ns:dialog-info"
	version="..."
	state="full"
	entity="sip:101@...">
	<dialog id="..."
		direction='initiator'
		call-id='...'
		local-tag=""
		remote-tag="">
		<state>terminated</state>
		<local>
			<identity display="B">sip:101@...</identity>
			<target uri="sip:101@...;line=...">
				<param pname="x-line-id" pval="0" />
			</target>
		</local>
	</dialog>
</dialog-info>

translate state => idle

quick dial allowed
pick-up not allowed

...
<NotifyParsingRules type="state">
	...
  	<level5 translates_to="idle"/>
</NotifyParsingRules>
...
<action>
	<invite target="$(subscr_uri)"
		when="on press"
		states="idle"/>
	<invite target="$(remote_uri)"
		when="on press"
		state="ringing"
		request_uri="$(remote_uri)"
		replaces="$(call_id);to-tag=$(remote_tag);from-tag=$(local_tag)"/>
</action>

⚪️		101
		idle

⚪️		Alex
		idle

incoming call ringing

dialog state => early/proceeding

NOTIFY
...
<?xml version="1.0"?>
<dialog-info
	xmlns="urn:ietf:params:xml:ns:dialog-info"
	version="..."
	state="full" entity="...">
	<dialog
		id="..."
		direction='recipient'
		call-id='...'
		local-tag="..."
		remote-tag="...">
		<state>early</state>
		<local>
			<identity display="B">
				sip:101@...
			</identity>
			<target uri="sip:101@...;line=...">
				<param pname="x-line-id" pval="0" />
			</target>
		</local>
		<remote>
			<identity display="C">
				sip:102@...
			</identity>
			<target uri="sip:102@..."/>
		</remote>
	</dialog>
</dialog-info>

translate state => ringing

quick dial not allowed
pick-up allowed

...
<NotifyParsingRules type="state">
	<level1
		translates_to="ringing">/dialog-info/dialog/state[.="early"]
	</level1>
	...
	<level2
		translates_to="ringing">/dialog-info/dialog/state[.="proceeding"]
	</level2>
  ...
</NotifyParsingRules>
<NotifyParsingRules
	type="variable"
	id="call_id"
	state="ringing">
	<level1 fetch_attribute="call-id">/dialog-info/dialog[@call-id]</level1>
</NotifyParsingRules>
<NotifyParsingRules
	type="variable"
	id="remote_tag"
	state="ringing">
	<level1 fetch_attribute="remote-tag">/dialog-info/dialog[@remote-tag]</level1>
</NotifyParsingRules>
<NotifyParsingRules
	type="variable"
	id="local_tag"
	state="ringing">
	<level1 fetch_attribute="local-tag">/dialog-info/dialog[@local-tag]</level1>
</NotifyParsingRules>
<NotifyParsingRules
	type="variable"
	id="remote_uri"
	state="ringing">
	<level1 fetch_attribute="uri">/dialog-info/dialog/remote/target[@uri]</level1>
</NotifyParsingRules>
<action>
	<invite target="$(subscr_uri)"
		when="on press"
		states="idle"/>
	<invite target="$(remote_uri)"
		when="on press"
		state="ringing"
		request_uri="$(remote_uri)"
		replaces="$(call_id);to-tag=$(remote_tag);from-tag=$(local_tag)"/>
</action>

🟠		102 > 101
		ringing

🟠		Alice > Alex
		ringing

incoming call accepted

dialog state => confirmed

NOTIFY
...
<?xml version="1.0"?>
<dialog-info
	xmlns="urn:ietf:params:xml:ns:dialog-info"
	version="..."
	state="full"
	entity="sip:101@...">
	<dialog
		id="..."
		direction='recipient'
		call-id='...'
		local-tag="..."
		remote-tag="...">
		<state>confirmed</state>
		<local>
			<identity display="B">sip:101@...</identity>
			<target uri="sip:101@...;line=...">
				<param pname="x-line-id" pval="0" />
				<param pname="+sip.rendering" pval='yes' />
			</target>
		</local>
			<remote>
				<identity display="C">sip:102@...</identity>
				<target uri="sip:102@..."/>
			</remote>
	</dialog>
</dialog-info>

translate state => talking

quick dial not allowed
pick-up not allowed

...
<NotifyParsingRules type="state">
	...
	<level4
		translates_to="talking">/dialog-info/dialog/state[.="confirmed"]
	</level4>
</NotifyParsingRules>
...
<action>
	<invite target="$(subscr_uri)"
		when="on press"
		states="idle"/>
	<invite target="$(remote_uri)"
		when="on press"
		state="ringing"
		request_uri="$(remote_uri)"
		replaces="$(call_id);to-tag=$(remote_tag);from-tag=$(local_tag)"/>
</action>

🔴		102 <> 101
		talking

🔴		Alice <> Alex
		talking

Incoming call terminated

dialog state => terminated

NOTIFY
...
<?xml version="1.0"?>
<dialog-info
	xmlns="urn:ietf:params:xml:ns:dialog-info"
	version="8"
	state="full"
	entity="sip:101@...">
	<dialog id="..."
		direction='recipient'
		call-id='...'
		local-tag="..."
		remote-tag="...">
		<state>terminated</state>
		<local>
			<identity display="B">sip:101@...</identity>
			<target uri="sip:101@...;line=...">
				<param pname="x-line-id" pval="0" />
			</target>
		</local>
		<remote>
			<identity display="C">sip:102@...</identity>
			<target uri="sip:102@..."/>
		</remote>
	</dialog>
</dialog-info>

translate state => idle

quick dial allowed
pick-up not allowed

...
<NotifyParsingRules type="state">
  ...
  <level5 translates_to="idle"/>
</NotifyParsingRules>
... 
<action>
	<invite target="$(subscr_uri)"
		when="on press"
		states="idle"/>
	<invite target="$(remote_uri)"
		when="on press"
		state="ringing"
		request_uri="$(remote_uri)"
		replaces="$(call_id);to-tag=$(remote_tag);from-tag=$(local_tag)"/>
</action>

⚪️		101
		idle

⚪️		Alex
		idle

Outgoing call ringing

dialog state => early/proceeding

NOTIFY
...
<?xml version="1.0"?>
<dialog-info
	xmlns="urn:ietf:params:xml:ns:dialog-info"
	version="13"
	state="full"
	entity="sip:101@...">
	<dialog
		id="..."
		direction='initiator'
		call-id='...'
		local-tag="..."
		remote-tag="">
		<state>early</state>
		<local>
			<identity display="B">sip:101@...</identity>
			<target uri="sip:101@...;line=...">
				<param pname="x-line-id" pval="0" />
			</target>
		</local>
		<remote>
			<identity display="D">sip:103@...;user=phone</identity>
			<target uri="sip:103@...;user=phone"/>
		</remote>
	</dialog>
</dialog-info>

translate state => calling

quick dial not allowed
pick-up not allowed

...
<NotifyParsingRules type="state">
	<level1
		translates_to="ringing">/dialog-info/dialog/state[.="early"]
	</level1>
	<level1-1
		translates_to="calling">/dialog-info/dialog[@direction="initiator"]
	</level1-1>
	<level2
		translates_to="ringing">/dialog-info/dialog/state[.="proceeding"]
	</level2>
	<level2-1
		translates_to="calling">/dialog-info/dialog[@direction="initiator"]
	</level2-1>
</NotifyParsingRules>
...
<action>
	<invite target="$(subscr_uri)"
		when="on press"
		states="idle"/>
	<invite target="$(remote_uri)"
		when="on press"
		state="ringing"
		request_uri="$(remote_uri)"
		replaces="$(call_id);to-tag=$(remote_tag);from-tag=$(local_tag)"/>
</action>

🔴		101 > 103
		calling

🔴		Alex > Tita
		calling

Outgoing call accepted

dialog state => confirmed

NOTIFY
...
<?xml version="1.0"?>
<dialog-info
	xmlns="urn:ietf:params:xml:ns:dialog-info"
	version="..."
	state="full"
	entity="sip:101@...">
	<dialog
		id="..."
		direction='initiator'
		call-id='...'
		local-tag="..."
		remote-tag="...">
		<state>confirmed</state>
		<local>
			<identity display="B">sip:101@...</identity>
			<target uri="sip:101@...;line=...">
				<param pname="x-line-id" pval="0" />
				<param pname="+sip.rendering" pval='yes' />
			</target>
		</local>
		<remote>
			<identity display="D">sip:103@...</identity>
			<target uri="sip:103@..."/>
		</remote>
	</dialog>
</dialog-info>

translate state => talking

quick dial not allowed
pick-up not allowed

...
<NotifyParsingRules type="state">
	...
	<level4
		translates_to="talking">/dialog-info/dialog/state[.="confirmed"]
	</level4>
</NotifyParsingRules>
... 
<action>
	<invite target="$(subscr_uri)"
		when="on press"
		states="idle"/>
	<invite target="$(remote_uri)"
		when="on press"
		state="ringing"
		request_uri="$(remote_uri)"
		replaces="$(call_id);to-tag=$(remote_tag);from-tag=$(local_tag)"/>
</action>

🔴		101 <> 103
		talking

🔴		Alex <> Tita
		talking

Outgoing call terminated

dialog state => terminated

NOTIFY
...
<?xml version="1.0"?>
<dialog-info
	xmlns="urn:ietf:params:xml:ns:dialog-info"
	version="..."
	state="full"
	entity="sip:101@...">
	<dialog
		id="..."
		direction='initiator'
		call-id='...'
		local-tag="..."
		remote-tag="...">
		<state>terminated</state>
		<local>
			<identity display="B">sip:101@...</identity>
			<target uri="sip:101@...;line=...">
				<param pname="x-line-id" pval="0" />
			</target>
		</local>
		<remote>
			<identity display="D">sip:103@...</identity>
			<target uri="sip:103@..."/>
		</remote>
	</dialog>
</dialog-info>

translate state => idle

quick dial allowed
pick-up not allowed

...
<NotifyParsingRules type="state">
	...
  	<level5 translates_to="idle"/>
</NotifyParsingRules>
... 
<action>
	<invite target="$(subscr_uri)"
		when="on press"
		states="idle"/>
	<invite target="$(remote_uri)"
		when="on press"
		state="ringing"
		request_uri="$(remote_uri)"
		replaces="$(call_id);to-tag=$(remote_tag);from-tag=$(local_tag)"/>
</action>

⚪️		101
		idle

⚪️		Alex
		idle

Questions

Below is a list of questions to be addressed as a result of this requirements document:

Question	Outcome
Shall we visualize all possible translation states?	Alexander Feldt I'd agree, for these reasons: Snom phones (acting as UAS) already provide all information in NOTIFY body It's cleaner, e.g. when the UAS goes offhook or calls somebody, currently "talking" is visualized, which is not true. It could be an advanced sales feature?
Shall we allow quick dial only in idle state?	Alexander Feldt Technically, we could allow quick dial in any state, except ringing... Zsolt Erdei Quick dial → Dial the configured extension happens only in Idle state; in Calling state does the button nothing to do, in connected state, when the party is different, the blf might blind transfer the call
Shall we create new icons or reuse those already existing ones?	Alexander Feldt I really question icons, that are so small, that there is no visible difference to the user, like and , therefore - if we use them at all - I vote for better distinguishable icons. Zsolt Erdei If possible reuse
How can a specific LED behaviour be addressed using XML definitions?	Alexander Feldt Currently not within XML definitions, it has to be configured via settings. Zsolt Erdei Using a new statename; that new name is added in xml definition to "state" variable and the string is configured in the led settings.
How can a specific label be addressed using XML definitions?	Alexander Feldt see label, but I haven't figured out how to define it correctly Zsolt Erdei with the label variable Initialisation: `<variable` `name="label"` `value="Clock on"/>` During XML evaluation: `<assign` `when="on press">` `<source` `value="Hello"/>` `<destination` `id="label"/>` `</assign>`
How can a specific icon be addressed using XML definitions?	Alexander Feldt see icon, but I haven't figured out how to define it correctly Zsolt Erdei As I remember, same as label, value name is icon.
How shall the Label area be configured to use either number or display name?	Alexander Feldt The topic is even more complex: I assume the PFK label is generally too short to show longer extension number or names, i.e. some kind of scrolling must be used. But is this really helpful for the customer at all? Zsolt Erdei It is shorted by an ellipse in QT; I think it is enough if we display the label value and the state.
From the UX point of view: which visual aid is more important for the customer: LED or PFK label?	Alexander Feldt The colour of the LED and if it is blinking => very important The label icon => basically not important, the LED is already showing everything, also the PFK label is not even shown by default The label name => important when it comes to call pickup, less important for other scenarios, so is it worth adding scrolling or should we keep it simpler? The label state => It is definitely an additional information, which cannot be shown with LED only, e.g. the difference between offhook, calling and talking Zsolt Erdei I say led + status on pfkey label
Tita Petre Is the above list of requirements enough input to create a proper testplan?
Clemens Cramer As the decision to move the default blf & extension configuration to a xml definition is based on customer requests to modify the behavior, guides with working examples on how to change the labels, icons, led behavior, and handled dialog states should probably be a requirement (and as such covered by tests).

Not Doing

List the features discussed which are out of scope or might be revisited in a later release.