What is group communication in distributed systems?

Communication between two processes is essential to transfer data between the processes, such as code or a file.

Group Communication occurs when a single source process simultaneously attempts to communicate with numerous functions.

A group is an abstract collection of interrelated operations. This abstraction hides the message passing such that the communication seems to be a standard procedure call. Group communication also enables processes from separate hosts to collaborate and conduct activities in a coordinated way, improving overall system performance.

Different areas of group communication

Types of group communication

As illustrated above, there are three types of group communication. They are defined below:

Broadcast communication

This occurs when the host simultaneously attempts to communicate with all the processes in a distributed system. It is helpful when a consistent information stream must be supplied to all methods effectively. Communication is highly rapid compared to other means of communication since it does not require processing. It doesn't, however, support many operations and cannot address each function independently.

P1 process communicating with every process in the system

Multicast communication

The host process attempts to simultaneously interact with a specific set of operations in a distributed system. This approach is mainly used to discover solutions to the high burden on the host system and duplicate information from system processes. Multitasking can considerably reduce the time required to handle messages.

P1 process communicating with only a group of the process in the system

Unicast communication

This occurs when the host process attempts to interact with a single operation in a distributed system simultaneously. It works well for two processes interacting since it treats one way. However, it incurs costs since it must first determine the specific procedure and then communicate information.

P1 process communicating with only P5 process

Group communication characteristics

Atomicity, often known as an all-or-nothing quality, is a crucial property in the group communication mechanism. If one or more group members have a problem receiving the message, the process that delivers it to them will get an error notice.

The ordering attribute of the messages is in charge of managing the order in which messages are delivered. Message ordering types include:

  • No order means message sending happens without regard for the order to the group.

  • FIFO first in, first outorder means messages are shown in the order they are sent.

  • Casual order means messages are shipped in a random order after receiving another message.

  • Total order means all communications are sent to all group members in the same order.

Group organization

Group communication systems can be classified as either closed or open. Only members of the closed group can send messages to the group. Users who are not group members can send messages to each member separately. Non-members in the open group can send messages to the group. The program's objective determines the use of a closed or open group.

The group's internal structure can be determined based on its organization. All decisions in egalitarian groupings are made collaboratively. In the event of a failure, the group proceeds without a procedure. The coordinator makes decisions in hierarchical clusters. The loss of the coordinator brings all processes to a standstill.

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