WE CLAIM:
[Claim 1] A transfer device included in a plurality of transfer devices
constituting a ring network, the transfer device comprising:
an acquisition unit to acquire a transfer frame;
a server unit to execute a server function of providing a service;
an identification unit to identify whether the transfer frame acquired by the acquisition unit is a server traffic frame used for achieving synchronization between the server unit and a server unit of an adjacent transfer device;
a closure management unit to manage closure information indicating whether a link route is closed, the link route connecting the transfer device and the adjacent transfer device and allowing the server traffic frame to be communicated between the transfer device and the adjacent transfer device, the link route blocking a transfer frame other than the server traffic frame;
a status management unit to manage status information indicating whether there is a fault in the ring network; and
a port selection unit to select, when the transfer frame is the server traffic
frame, an output port corresponding to a transfer destination of the server traffic frame
based on the status information and the closure information.
[Claim 2] The transfer device according to claim 1, wherein
when there is no fault in the ring network, the port selection unit selects an
output port through which the server traffic frame corresponds to the link route.
[Claim 3] The transfer device according to claim 1 or 2,
wherein when there is a fault in the ring network and the link route is not closed, the port selection unit selects an output port through which the server traffic frame corresponds to the link route.

[Claim 4] The transfer device according to any one of claims 1 to 3,
wherein when there is a fault in the ring network and the link route is closed,
the port selection unit selects an output port corresponding to a transfer destination of
the server traffic frame, using a Media Access Control (MAC) address of the server unit
of the adjacent transfer device.
[Claim 5] The transfer device according to any one of claims 1 to 4,
wherein the ring network is constructed by an Ethernet (registered trademark) Ring Protection (ERP) method, and
wherein the link route is a Ring Protection Link (RPL) that can be blocked in
the ring network.
[Claim 6] The transfer device according to claim 5,
wherein the closure management unit determines whether or not the link route
is closed, using a Connectivity Check frame in Operations Administration Maintenance
(OAM) of Ethernet, or a protocol defined at an application level of layer 2 or more.
[Claim 7] A transfer method of a transfer device included in a plurality of
transfer devices constituting a ring network, the transfer device comprising a server unit to execute a server function of providing a service, the transfer method comprising:
by an acquisition unit, acquiring a transfer frame;
by an identification unit, identifying whether the transfer frame acquired by the acquisition unit is a server traffic frame used for achieving synchronization between the server unit and a server unit of an adjacent transfer device;
by a closure management unit, managing closure information indicating whether a link route is closed, the link route connecting the transfer device and the adjacent transfer device and allowing the server traffic frame to be communicated between the transfer device and the adjacent transfer device, the link route blocking a

transfer frame other than the server traffic frame;
by a status management unit, managing status information indicating whether there is a fault in the ring network; and
by a port selection unit, selecting, when the transfer frame is the server traffic
frame, an output port corresponding to a transfer destination of the server traffic frame
based on the status information and the closure information.
[Claim 8] A transfer program of a transfer device included in a plurality of
transfer devices constituting a ring network, the transfer device comprising a server unit to execute a server function of providing a service, the transfer program comprising:
an acquisition process of acquiring a transfer frame;
an identification process of identifying whether the transfer frame acquired by the acquisition process is a server traffic frame used for achieving synchronization between the server unit and a server unit of an adjacent transfer device;
a closure management process of managing closure information indicating whether a link route is closed, the link route connecting the transfer device and the adjacent transfer device and allowing the server traffic frame to be communicated between the transfer device and the adjacent transfer device, the link route blocking a transfer frame other than the server traffic frame;
a status management process of managing status information indicating whether there is a fault in the ring network; and
a port selection process of selecting, when the transfer frame is the server traffic frame, an output port corresponding to a transfer destination of the server traffic frame based on the status information and the closure information.