What is required to achieve gigabit network throughput on EC2? You already selected cluster-compute, 10GB instances
with enhanced networking, and your workload is already network-bound, but you are not seeing 10 gigabit speeds.

A.
Enable biplex networking on your servers, so packets are non-blocking in both directions and there’s no switching overhead.

B.
Ensure the instances are in different VPCs so you don’t saturate the Internet Gateway on any one VPC.

C.
Select PIOPS for your drives and mount several, so you can provision sufficient disk throughput.

D.
Use a placement group for your instances so the instances are physically near each other in the same Availability Zone.

Explanation:
You are not guaranteed 10gigabit performance, except within a placement group. A placement group is a logical grouping
of instances within a single Availability Zone. Using placement groups enables applications to participate in a low-latency,
10 Gbps network. Placement groups are recommended for applications that benefit from low network latency, high
network throughput, or both.
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html