Please take a look at our Amazon EC2:
Quick Start Guide which shows the options you have available.
From here you can see the supported instances and
pre-built AMIs which include the C3 and HS1.
More detail on the the instance types can be found on the
Amazon EC2 Instances page which includes details on Cluster Networking.
C3, I2, CR1, G2, and HS1 instances support cluster networking. Instances launched into a common cluster placement group are placed into a logical cluster that provides high-bandwidth, low-latency networking between all instances in the cluster. Cluster networking is ideal for high performance analytics systems and many science and engineering applications, especially those using the MPI library standard for parallel programming.
You may also want to check out CloudFront. Please see our article below.