Abstract: A communication system capable of high-quality routing and improved in operability. An IPsec tunneling control section sets up an IPsec tunnel on the Internet between the device in which it is provided and a remote router, by using an ISAKMP default route. A routing registration section has a routing table in which local IP addresses as destination addresses are statically registered and also a second router is statically registered as an IP default route for addresses other than the registered local IP addresses. When the IPsec tunnel is set up, the routing registration section identifies a global IP address of the remote router and dynamically registers the global IP address in the routing table in association with the corresponding local IP address. A packet transfer section transfers packets in accordance with the routing table.

Abstract: The invention relates to a network emulating a local network, and particularly provides a communication cache management device that uses, e.g., an MPOA for efficiently transmitting LAN data within an ATM network, and a method therefor. A communication cache management method at an ingress communication client side includes the steps of: monitoring a data flow that is transmitted to an ingress communication server within a predetermined time period before a time-out of an aging timer after a shortcut has been set; re-starting an aging timer when there has been detected a data flow that exceeds a predetermined value; timing out the aging timer when there has been detected no data flow that exceeds the predetermined value; and timing out the aging timer when the contents of a response message to a communication address resolution request message do not permit a cache refresh.

Abstract: An ATM network system of the present invention contains a clock synchronization source and a plurality of nodes. In this ATM network system, a plurality of clock supply routes are set, which are used in receiving clocks from the clock synchronization source by each of the nodes. When each of the nodes detects a failure occurred in the presently used route, each of the nodes supplies a failure signal to other nodes which receive the clock supplied from the own node through this route, and further changes a route under use into another route. When each of the nodes receive the failure signals from other nodes, each of these nodes changes the route under use into another route.

Abstract: An exchange constituting an ATM network administers the number of UBR connections for every line port included in the exchange. Upon receiving a request for setting a UBR connection, the exchange determines the route of the UBR connection on the basis of the number of the UBR connections administered for every line port included in the exchange.