Synchronizing asynchronous protocol interactions between peer layers in different nodes of a layered communication network

摘要

A method and apparatus for allowing the higher layers of two nodes on a connection that uses an asynchronous link protocol to synchronize the exchange of messages so that, without knowledge of the lower data link protocols, the protocols at higher layers can complete when the data link protocols are also complete. The upper layer of a node sends messages for transmittal to another node to the lower layer of its node and receives messages from another node via the lower layer of its node. A first message, including an initiator flag is sent from the upper layer of the first node to the lower layer of the first node. In response, the lower layer transmits a second message including the initiator flag from the first message to the lower layer of the second node. The second message is transmitted as a command or a response in accordance with the send process state of the lower layer of the first node. If the upper layer of the first node subsequently detects a fourth message from the lower layer of the first node (which corresponds to a third message from the second node) and if the initiator flag is ON in the fourth message, the primary or secondary status of the first node is determined. If the first node is primary, the first message is resent to the lower layer of the first node until a message is received having the initiator flag set to OFF. The initiator flag is set to ON in all subsequent messages to the lower layer of the first node related to the first message. If the first node is secondary, the fourth message is discarded and the initiator flag in all subsequent messages to the lower layer of the first node related to the first message are set to OFF.