Exchange Team published a great article explaining how to disable the power saving mode in a NIC adapter, specially when running Exchange Server.
Read more at source: http://blogs.technet.com/b/exchange/archive/2013/10/22/do-you-have-a-sleepy-nic.aspx
Cheers,
Anderson Patricio
Exchange Server MVP
@APatricio
http://www.AndersonPatricio.ca