The reliability of datagram transmission over Copper Gigabit Ethernet using commodity hardware at sustained Gb/s rate is crucial for the functioning of the software trigger layers of the LHCb experiment. We aim to demonstrate that a nowadays available high-end commodity PC can be employed to achieve the required network performance, in particular to implement a sub-farm controller node. To evaluate all components ranging from the physical medium up to the operating system running on the sub-farm controllers, several issues are addressed, such as transmission error rate, packet drop in switching hardware, protocol handling on reception.