A first in-line network interface card, NIC, to handle network flows, the first in-line NIC comprising: a first media access controller, MAC; a second MAC; processing hardware configured to provide passthrough transmission (154, 156) of packets of the network flows by transmitting from the first MAC packets received by the second MAC and by transmitting from the second MAC packets received by the first MAC; a first module configured to implement a lightweight transport protocol, LTP; and a second module configured to communicate with an arbitrary second in-line NIC via the first module by specifying a network address corresponding to the second in-line NIC to enable the first module to establish an LTP connection with endpoints at the first in-line NIC and at the second in-line NIC, wherein the first in-line NIC is connected to a first host and to the data network, and the second in-line NIC is connected to a second host and to the data network, wherein the processing hardware is configured to provide network connectivity between the first host and the second host by performing pass-through transmission of received packets that are determined to not be inter-NIC LTP packets, and provide inter-NIC LTP connectivity between the first in-line NIC and the second in-line NIC, and wherein packets received by the first in-line NIC that are determined to be inter-NIC LTP packets are consumed by the first in-line NIC and are not forwarded to the first or second host by the first in-line NIC, and wherein the inter-NIC LTP packets are originated by the first or second in-line NIC. a first media access controller, MAC; a second MAC; processing hardware configured to provide passthrough transmission (154, 156) of packets of the network flows by transmitting from the first MAC packets received by the second MAC and by transmitting from the second MAC packets received by the first MAC; a first module configured to implement a lightweight transport protocol, LTP; and a second module configured to communicate with an arbitrary second in-line NIC via the first module by specifying a network address corresponding to the second in-line NIC to enable the first module to establish an LTP connection with endpoints at the first in-line NIC and at the second in-line NIC, wherein the first in-line NIC is connected to a first host and to the data network, and the second in-line NIC is connected to a second host and to the data network, wherein the processing hardware is configured to provide network connectivity between the first host and the second host by performing pass-through transmission of received packets that are determined to not be inter-NIC LTP packets, and provide inter-NIC LTP connectivity between the first in-line NIC and the second in-line NIC, and wherein packets received by the first in-line NIC that are determined to be inter-NIC LTP packets are consumed by the first in-line NIC and are not forwarded to the first or second host by the first in-line NIC, and wherein the inter-NIC LTP packets are originated by the first or second in-line NIC. provide network connectivity between the first host and the second host by performing pass-through transmission of received packets that are determined to not be inter-NIC LTP packets, and provide inter-NIC LTP connectivity between the first in-line NIC and the second in-line NIC, and wherein packets received by the first in-line NIC that are determined to be inter-NIC LTP packets are consumed by the first in-line NIC and are not forwarded to the first or second host by the first in-line NIC, and wherein the inter-NIC LTP packets are originated by the first or second in-line NIC.