Abstract: A Present Application Server (PAS) is holding a presence list for each user is introduced. The presence list of a first user comprises other network registered users for which the first user, wants to track the registration status. The registration status of each user corresponds to the user's registration status in their associated Gatekeepers. Each time a change in registration status for a user occurs in its associated Gatekeeper, the Gatekeeper will send a message including an identification of both the user and the Gatekeeper, in addition to information concerning the change of status (register or unregister). The presence lists affected by the change of the registration status of said user is updated in the PAS. Then the associated users are informed by messages sent from the PAS via the Gatekeeper to the user's EndPoints. The messages are adapted to refresh URL's at the EndPoints pointing at the user's presence list.

Abstract: A method for exchange of vertical information in a layered redundant deployed network is disclosed. At an endpoint side, a first message, e.g. a user registration message, is vertically being sent upwards from layer to layer. For each passed node, an address list of peers in the current layer is added to the message. When reaching the uppermost layer, all the address lists added to the message are being stored in a node in that layer. A second message confirming the first message is being sent from the latter node in the opposite vertical direction from layer to layer, wherein said second message always contains the addresses of the previously passed node and its redundant peers. These addresses are stored in each node receiving said second message. Consequently, the uppermost layer at the endpoint side will know all the alternative routes for transmitting messages vertically towards the lowermost layer.