4. The computer program product of claim 3 , Wherein the I/O operation is a transport mode operation, and obtaining information includes obtaining a transport command word (TCW) at the channel subsystem, the TCW including a transport command control block (TCCB) address field including an address of a TCCB, the TCCB including a plurality of device command words (DCW) that each includes an I/O command.
4. The computer program product of claim 3 , Wherein the I/O operation is a transport mode operation, and obtaining information includes obtaining a transport command word (TCW) at the channel subsystem, the TCW including a transport command control block (TCCB) address field including an address of a TCCB, the TCCB including a plurality of device command words (DCW) that each includes an I/O command. 6. The computer program product of claim 4 , wherein the data transfer request is a request for the output data from the host memory location, the at least one generated, data check word is generated using the initial value from the Data Check Word Seed field of a Transport Write Data ACW and a length of the output data that is received at the channel, and the at least one generated data check word is appended at an end of the output data that is routed to the network interface.