In this paper, we present a PVM extension which through a middleware solution based on the H2O distributed metacomputing framework, permits us to build a parallel virtual machine composed of hosts located across multidomain clusters.

In the H2O framework, we have developed specialized proxy pluglets used to route PVM messages among computational resources placed in different network domains that firewalls can shield should the need arise.

The simulation tests that we have performed showed a smaller time overhead in communications across the proxies. However, this is acceptable if we consider the benefits gained in utilizing resources that we can now exploit owing to the fact that they are often located on non-routable private networks. PVM applications can be ported into this system without modifications.