1. A method for receiving a single message, the method comprising: receiving, by a receiving communication adapter from a transmitting communication adapter via a consolidated processor and input/output (I/O) network, a first sub-unit of a plurality of sub-units in the single message, wherein the first sub-unit comprises a first payload, and wherein the single message is partitioned into the plurality of sub-units by the transmitting communication adapter; identifying a first maximum transmission unit (MTU) encoding on the first sub-unit; determining that the first sub-unit is received when a size of the first sub-unit matches the first MTU encoding; performing, by the receiving communication adapter, direct memory access to store the first payload in the memory of a receiving device, wherein the receiving device is directly connected, via a peripheral component interconnect (PCI) express connection, to the receiving communication adapter and comprises a receiving entity; appending, by the receiving communication adapter, a first completion code into the first sub-unit; sending, by the receiving communication adapter, a first notification to the receiving entity of the first completion code; making, by the receiving entity, in response to the first notification, a first determination that the first sub-unit is completely stored based on the first completion code; processing, by the receiving entity, the first payload based on the first determination; receiving, by the receiving communication adapter via the consolidated processor and I/O network, a second sub-unit of the plurality of sub-units after the first payload is processed by the receiving entity, wherein the second sub-unit comprises a second payload; identifying a second MTU encoding on the second sub-unit, wherein the second MTU encoding specifies a different size value than the first MTU encoding, wherein the second MTU encoding is defined based on selecting from a group consisting of ramping up and ramping down of a MTU size of the single message, and wherein ramping up is performed as a function of a first constant and ramping down is performed as a function of a second constant; determining that the second sub-unit is received when a size of the second sub-unit matches the second MTU encoding; performing, internally at a receiving side comprising the receiving communication adapter and the receiving device, and by the receiving communication adapter, direct memory access via the PCI express connection to store the second payload in the memory of the receiving device; and making, by the receiving entity, a second determination that the second sub-unit is completely stored based on a second completion code appended by the receiving communication adapter, wherein the first completion code is different than the second completion code.