Patent ID: 7936750
Filing Date: 2011-05-03
Classification: H04L

Abstract:
1. A packet transfer device which is a first packet transfer device in a communication system that includes the first packet transfer device and a second packet transfer device, wherein the first packet transfer device is a layer 2 switch and is set to an uplink VLAN setting, and the second packet transfer device is a layer 3 switch and performs routing of a packet between the first packet transfer device and a server or a network, wherein, the first packet transfer device has a first port for communicating with a first terminal, a second port for communicating with a second terminal, and a third port for communicating with the second packet transfer device, the packet inputted from the first port and the second port is fixedly transferred to the third port according to the uplink VLAN setting, the first packet transfer device transfers the packet received from the first terminal through the first port and the packet received from the second terminal through the second port to the third port in accordance with the uplink VLAN setting, the first packet transfer device transfers the packet received from the second packet transfer device through the third port to either one of the first port and the second port in accordance with destination information of the packet, and communication between the first terminal and the second terminal is realized through the first and the second packet transfer devices, the packet transfer device which is the first packet transfer device comprising: a device management table to correspondingly store sending terminal information including identification information of the first terminal and identification information of the first port, and receiving terminal information including identification information of the second terminal and identification information of the second port; a connection management table to store output port information corresponding to transmission source information and transmission destination information of a packet; and a processing unit which snoops SIP (Session Initiation Protocol) messages, wherein the processing unit registers, in a case where a session establishment request of a SIP message from the first terminal is received through the first port, the identification information of the first terminal in the session establishment request packet and the identification information of the first port into the sending terminal information of the device management table by snooping the session establishment request packet, registers, in a case where a response packet of the SIP message to the session establishment request packet is received from the second terminal through the second port, the identification information of the second terminal in the response packet and the identification information of the second port into the receiving terminal information of the device management table correspondingly to the sending terminal information by snooping the response packet, registers into the connection management table the identification information of the first terminal registered in the device management table as transmission source information, the identification information of the second terminal as transmission destination information, and the second port information as output destination port information, registers into the connection management table the identification information of the second terminal registered in the device management table as transmission source information, the identification information of the first terminal as transmission destination information, and the first port information as output destination port information, searches, when a packet is received from the first or the second port, the connection management table based on transmission source information and transmission destination information of the received packet, transfers, in a case where the transmission source information and the destination information of the received packet are registered in the connection management table, the received packet through the second or the first port in accordance with corresponding output port information, and transfers, in a case where the transmission source information and the destination information of the received packet are not registered in the connection management table or in a case where the output port information of the connection management table indicates the third port, the received packet to the second packet transfer device through the third port in accordance with the uplink VLAN setting, wherein a SIP protocol is used as a protocol for session control, an INVITE packet as the session establishment request packet, a 200 OK packet to the INVITE packet as the response packet, and a BYE message as the session disconnection request packet are respectively snooped, and snooped information is registered in the device management table in advance and then, the information registered in the device management table is registered into the connection management table.