SSIS cannot be installed as a cluster-aware service, but it can be made cluster-aware after the initial install.
If you want to use SSIS ‘out of the box’, then you will need to explicitly install SSIS on all nodes of your cluster. When you apply maintenance or add SSIS packages, you will need to do this on each SSSIS node separately. In this situation, SSIS is not cluster-aware and will not fail-over with the rest of the cluster.
If you want to make a SSIS cluster, this link from Microsoft discusses how to do this: http://msdn.microsoft.com/en-us/library/ms345193.aspx