P2P Common Functions and Characteristics

Early P2P applications were single-function, formed groups of peers from ordinary PCs, and peer group membership changed frequently or erratically. Chapter 3, "P2P Application Types" introduced multifunction applications and the commercialization and adoption of P2P in the corporate environment.

Now we can compare and contrast P2P with existing and emerging systems. Comparing these systems to P2P requires examining network formation, functional partitioning, models of communication, and the supported standards.

Dynamic Networks

Dynamic networks are an essential characteristic of P2P. Dynamic networks are enabled by

• Discovery A dynamic approach to searching and locating an identity within a broadcast horizon

• Identity A unique identifier for a peer or resource within a domain

• Presence The online status of a peer or resource based on identity

• Domain space A virtual space (network) bound by discovery

Edge devices are the building blocks of dynamic networks. They collaborate to form a virtual space of connected devices. Recent models of P2P are extending participation to include server-to-server and server-to-edge devices.

Equality and Autonomy

In addition to the dynamics of the network, you must look at the partitioning of the functionality. You need to identify whether there are central control points, and if so, what they control. You should also identify access control to resources, such as databases, files, networks and other clients.

In addition, you need to determine whether centralized administration of the system is required. You must also determine how the system and network is monitored for faults, availability, intrusions, and so on.

What are the security implications with the model implemented? It might provide limited or no security, or be highly secure in relation to the functionality provided.

You should consider centralization versus decentralization depending on the technology. Mixed models are composed of centralized and decentralized nodes (peers) that are connected at pivotal control points. For instance, a central node might be used as a file index, or provide presence and identity services.

Finally, look at the standards supported by the technology. Is P2P trying to provide a service that has already been standardized? Is there an overlap or fit with existing systems?