Processes communicate through a message exchange service provided by the network.
Informally, the consequences of large scale on the system are the following. The network is not fully connected and is typically quite sparse. Both processes and communication links may fail by crashing. Furthermore, the network may allow delivery of duplicate messagesand it provides no message sequencing guarantees. Given that the computing and communication resources may be shared by large numbers of processes and messages, the load on the system will be highly variable and unpredictable.