Abstract: There is provided a method of switching from multipoint communication to point-to-point communication while a device performs the multipoint communication with a plurality of participant devices. The method comprises: sharing, by the device, peer-to-peer (P2P) connection information of the device and P2P connection information of each of the plurality of participant devices, with the plurality of participant devices; and switching by the device, from the multipoint communication to the point-to-point communication using the P2P connection information of remaining participant devices of the plurality of participant devices in the multipoint communication when a total number of the remaining participant devices of the multipoint communication decreases to two.

Abstract: Provided are a system and method for a video call. The system for a video call includes one or more terminals configured to transmit images obtained by capturing video call users, and a video call control server configured to generate a combined image by combining the images transmitted by the one or more terminals, and transmit the combined image to the terminals. Here, the respective images are rotated according to information on orientations sensed by the terminals, and combined into the combined image.

Abstract: There is provided an apparatus for controlling transmission of data traffic to a destination node. The apparatus includes: an interface unit configured to obtain information regarding a congestion condition that has occurred on a first routing path during transmission of the data traffic; and a control unit configured to select, based on the information, a second routing path to route, to the destination node, a first portion and a second portion of the data traffic along the first routing path and the second routing path, respectively.

Abstract: Provided is a quality-of-service (QoS)-guaranteed video stream method. The QoS-guaranteed video stream method includes transmitting, by a transmitting server, a video stream including different video stream data for a plurality of respective layers, to a relay server, receiving, by the transmitting server, first section network state information which is information about a network state between the relay server and the transmitting server, from the relay server, receiving, by the transmitting server, second section network state information which is information about a network state between the plurality of respective user terminals and the transmitting server, and adjusting, by the transmitting server, qualities of video streams which are transmitted to the plurality of respective user terminals through the relay server by using network state information of the first section and network state information of the second section.

Abstract: Provided are a data transmission system and method of using a relay server. In the data transmission method using the relay server, the relay server transmits a registration result message to a client after registering the client through a registration packet when the client transmits the registration packet to the relay server. The relay server transmits registration information of the client to a location server. The location server stores client registration information according to each client.

Abstract: Provided are a system and method for a video call. The system for a video call includes one or more terminals configured to transmit images obtained by capturing video call users, and a video call control server configured to generate a combined image by combining the images transmitted by the one or more terminals, and transmit the combined image to the terminals. Here, the respective images are rotated according to information on postures sensed by the terminals and combined into the combined image.

Abstract: Provided are a peer-to-peer (P2P) connection system and method for use in a multi-network environment. The P2P connection system includes a user terminal configured to register connection information for connecting to the user terminal through each of a plurality of connectable networks in a location server; and the location server configured to store the connection information received from the user terminal.

Abstract: There is provided a method of switching from multipoint communication to point-to-point communication while a device performs the multipoint communication with a plurality of participant devices. The method comprises: sharing, by the device, peer-to-peer (P2P) connection information of the device and P2P connection information of each of the plurality of participant devices, with the plurality of participant devices; and switching by the device, from the multipoint communication to the point-to-point communication using the P2P connection information of remaining participant devices of the plurality of participant devices in the multipoint communication when a total number of the remaining participant devices of the multipoint communication decreases to two.

Abstract: A method for peer-to-peer (P2P) connection in a mobile environment, the method comprising: transmitting, from a first peer to a second peer, a connection request message through a push mechanism; transmitting, from the second peer to the first peer, a connection response message including connection information containing a private address of the second peer, a public address of the second peer and an address of a relay server; and attempting, at the first peer, to connect with the second peer by making a first connection attempt using the private address of the second peer, a second connection attempt using the public address of the second peer, and a third connection attempt using the address of the relay server, the first to the third connection attempts being made concurrently or sequentially at predetermined time intervals.

Abstract: A peer-to-peer (P2P) message transmission/reception system, a P2P message transmission/reception system and a media key distributing method using the system are disclosed. The P2P message transmission/reception system includes a transmitting client configured to add a first media key issued from a reception-side relay server to media data to be transmitted to the reception-side relay server, the reception-side relay server configured to issue the first media key to the transmitting client, receive the media data from the transmitting client, replace the first media key added to the received media data with a second media key issued from a receiving client, and transmit the media data having the second media key to the receiving client, and the receiving client configured to issue the second media to the reception-side relay server and receive the media data from the reception-side relay server.

Abstract: Provided are a system and method for transmitting and receiving Session Initiation Protocol (SIP) messages. The system includes user equipment (UE) including an SIP client configured to generate an SIP message, and an external transport configured to receive the SIP message from the SIP client, generate a packet by combining a tunneling header with the received SIP message, and transmit the generated packet to an SIP broker server, and the SIP broker server configured to receive the packet from the external transport in the UE, remove the tunneling header from the packet, and transmit the SIP message from which the tunneling header has been removed to a communication counterpart.

Abstract: Provided are a data transmission system and method of using a relay server. In the data transmission method using the relay server, the relay server transmits a registration result message to a client after registering the client through a registration packet when the client transmits the registration packet to the relay server. The relay server transmits registration information of the client to a location server. The location server stores client registration information according to each client.

Abstract: Provided are a peer-to-peer (P2P) connection system and method for use in a multi-network environment. The P2P connection system includes a user terminal configured to register connection information for connecting to the user terminal through each of a plurality of connectable networks in a location server; and the location server configured to store the connection information received from the user terminal.