Patent ID: 6738344
Filing Date: 2004-05-18
Classification: H04L

Abstract:
In a system area network including end nodes and routing nodes connected by physical links and link extenders for coupling links from either end nodes or routing nodes to serial cables, where the link extenders are coupled in a connection comprising a first node having a port, a first link extender having local and remote ports, a first link coupling the port of said first node and the local port of said first link extender, a second link extender having local and remote ports, a second link coupling the remote ports of said first and second link extenders, a second node having a port, and a third link coupling the local port of said second link extender to the port of said second node, with the links being duplex links and each port having a receiver and transmitter, and with ports of nodes in the system area network transmitting link alive symbols to indicate to remote ports on a link that the link is alive, a method for propagating link alive symbols through a link extender comprising the steps of:detecting, at a first link extender, an absence of link alive command transmissions on a first link coupled to a first port of the first link extender; blocking the transmission of link alive symbols on a second link coupled to the second port of said first link extender; monitoring said first port to detect the resumption of link alive commands transmitted on said first link; if transmission on said first link is resumed, unblocking the transmission of link alive symbols on the second link coupled to the second port of said first link extender so that loss and resumption of link alive command transmissions is propagated through the link extender.