/mcpCall Persistency Registration—LTE to Wi-Fi Support Unified Communications Manager provides the flexibility for Webex App users to switch between networks without getting disconnected from active calls using the Call Persistency Registration feature. When there is a call that is made from Webex App on iOS/Android devices and the user moves from LTE to Wi-Fi or vice versa, and Unified CM detects that the client has lost connection with the user, the call is not impacted. If Webex App connects back within 12 seconds, the active call and media are resumed with the client's updated connection address on a new network after switch re-registration. The following header tag is defined to support this capability: • X-cisco-sessionpersist: This tag informs Unified Communications Manager that the client supports call persistency after network switch. [1] Client A Registers -> CUCM - REGISTER, X-cisco-sessionpersist Registration successful message after identifying the new network post switch registration. [2] CUCM -> Client A - 200 OK Enhanced Interface Compliance Summary This section provides details with respect to overall flow and handling of enhanced SIP features on the Unified CM line-side interface. This includes, but is not limited to, the following features: Call-Info Header The Call-Info header is used mainly for the two following purposes: 1. Pass supplementary call information from Unified Communications Manager to the endpoint. 2. Pass supplementary feature activation information from the endpoint to Unified Communications Manager. The following sections describe each of these. Call-Info-Sent from Unified CM to Endpoint Unified Communications Manager line side SIP uses the Call-Info header with the Call-Info feature to pass supplementary call information to the endpoints. Inclusion of this information depends on whether the endpoint registers with the line including the x-cisco-callinfo tag. In case not, this information is not sent by Unified Communications Manager to the endpoint. This information is not required to make calls operational. It is additional supplementary information typically used to display call details to a phone user. For calls from a SIP endpoint to Unified Communications Manager, Unified CM sends Call-Info in response messages to the INVITE (for example, 18x and 200). For calls to a SIP endpoint from Unified Communications Manager, Unified CM sends Call-Info in the initial INVITE message to the phone. Throughout a dialog, re-INVITE messages and UPDATE messages may contain new Call-Info parameters. Here is an example with all the parameters: Call-Info: urn:x-cisco-remotecc:callinfo; security= NotAuthenticated; orientation= to; SIP Line Messaging Guide (Standard Edition) for Cisco Unified Communications Manager 51 SIP Standard Line Interface Call Persistency Registration—LTE to Wi-Fi Support