Microsoft Skype for Business Presence of Third-Party Endpoints

Microsoft presence capability allows Skype for Business users to know the status (e.g., "Available" or "Do Not Disturb") of their contacts. Presence status of contacts is displayed on the user's Skype for Business endpoint. Presence information of Skype for Business endpoints (such as Skype for Business desktop client) is handled solely by the Skype for Business Server, without any intervention of the device. However, when third-party (non-Skype for Business) endpoint devices (e.g., mobile phone or PBX phone) are used by the Skype for Business users, presence status information can only be reported to the Skype for Business Server by the device. For example, if John and Alice are Skype for Business users and John makes or receives a call on a mobile device, Alice is able to see that John is in a call, even though the call is not on a native Skype for Business endpoint. Once the device reports the presence status, the Skype for Business Server sends this status change to the Skype for Business users in the network.

The device notifies the Skype for Business Server of a user's presence status, by using SIP PUBLISH messages. The message transactions between the device and Skype for Business Server is as follows:

1.

The device routes a call between two Skype for Business users and when connected, sends a PUBLISH message with the Event header set to "presence", Expires header set to "600", Content-Type header set to "application/pidf+xml", and where the XML body's "activity" is set to "on-the-phone", as shown in the following example for user John Doe:

PUBLISH sip:john.doe@sfb.example SIP/2.0 
From: <sip:john.doe@sfb.example>;tag=1c537837102 
To: <sip:john.doe@sfb.example>
CSeq: 1 PUBLISH
Event: presence 
Expires: 600
Content-Type: application/pidf+xml 
Content-Length: 489

<?xml version="1.0" encoding="utf-8"?> 
<presence xmlns="urn:ietf:params:xml:ns:pidf" 
xmlns:ep="urn:ietf:params:xml:ns:pidf:status:rpid-status" 
xmlns:et="urn:ietf:params:xml:ns:pidf:rpid-tuple" 
xmlns:ci="urn:ietf:params:xml:ns:pidf:cipid" 
entity="sip:john.doe@sfb.example"> 
<tuple id="0"> 
<status> 
<basic>open</basic> 
<ep:activities> 
<ep:activity>on-the-phone</ep:activity> 
</ep:activities> 
</status> 
</tuple> 
<ci:display-name>John Doe</ci:display-name> 
</presence>

2.

The Skype for Business Server responds to the device with a SIP 200 OK. The message is sent with a SIP-ETag header which identifies the entity (and Expires header set to 600 seconds), as shown in the following example:

SIP/2.0 200 OK 
From: "John Doe"<sip:john.doe@sfb.example>;tag=1c537837102 
To: <sip:john.doe@sfb.example>;tag=0E4324A4B27040E4A167108D4FAD27E3 
Call-ID: 1284896643279201635736@10.33.221.57 
CSeq: 1 PUBLISH 
Via: SIP/2.0/TLS 10.33.221.57:5061;alias;…received=10.33.221.57;ms-received port=48093;ms-received-cid=4900 
SIP-ETag: 2545777538-1-1
Expires: 600 
Content-Length: 0 

3.

If the call lasts longer than 600 seconds, the device sends another PUBLISH message with the same SIP-ETag value and with an Expires header value of 600 seconds. The Skype for Business Server responds with another 200 OK, but with a new SIP-ETag value (and Expires header set to 600 seconds). This scenario occurs for each 600-second call interval.

4.

When the call ends, the device sends a PUBLISH message to cancel the user's online presence status (and the user's previous presence state is restored). The message is sent with a SIP-If-Match header set to the matching entity tag (SIP-ETag) value (i.e., SIP-ETag value of last 200 OK) and Expires header value set to "0", as shown in the following example:

PUBLISH sip:john.doe@sfb.example SIP/2.0 
From: <sip:john.doe@sfb.example>;tag=1c1654434948 
To: <sip:john.doe@sfb.example> 
CSeq: 1 PUBLISH 
Contact: <sip:john.doe@10.33.221.57:5061;transport=tls> 
Event: presence 
Expires: 0
User-Agent: sur1-vg1.ecarecenters.net/v.7.20A.001.080 
SIP-If-Match: 2545777538-1-1
Content-Length: 0

The following figure shows a basic illustration of the device's integration into Microsoft Skype for Business Presence feature for third-party endpoints.