Patent ID: 8683084

Claim:
A method of performing an input/output (I/O) processing operation at a host computer system configured for communication with a control unit, the method comprising: obtaining information relating to an I/O operation at a channel subsystem in the host computer system, the channel subsystem including at least one channel having a channel processor and a local channel memory, the channel subsystem in communication with a network interface configured to transmit data between the channel subsystem and the control unit during the I/O operation; generating at least one address control word (ACW) specifying one or more host memory locations for transfer of data between the host computer system and the control unit, and storing the at least one ACW in the local channel memory, the at least one ACW including a field for storing header information for use in one or more messages transmitted between the channel subsystem and the control unit; generating an address control structure for each data transfer specified by the I/O operation and forwarding each address control structure from the at least one channel to the network interface, each address control structure specifying a location in the local channel memory of a corresponding ACW; forwarding an I/O command message to the at least one I/O device via the network interface; responsive to the I/O command message, receiving a data transfer request from the network interface that includes the address control structure; responsive to the data transfer request including a header and data to be stored in the host memory, routing the data to at least one host memory location specified by the corresponding ACW and storing the header information in the corresponding ACW; and responsive to the data transfer request including a header and requesting data to be retrieved from the host memory, routing the data from a host memory location specified by the ACW to the network interface and appending header information to the data.