The classic Client-Server model is not suited to every networking scenario - in peer-to-peer environments, or highly fault-tolerant networks, dedicated server machines can be costly and cumbersome to manage. Silver Forge's XPN ("eXtensible Packet Network") technology leverages clients to extend the network - turning them into routers/repeaters for other clients on the network. It provides a unified communications architecture: Messaging, File-sharing and Searching in a single fault-tolerant protocol.

Taking the best that the classical paradigm has to offer, and implementing intelligent self-managing peers improves overall network health and can boost performance. XPN networks benefit from enhanced scalability, with the most powerful computers providing the backbone over which the slower nodes interchange data, but in a distributed manner where each node on the network adds to its overall capacity and resilience.

The network's reliance on one single system in order to function is removed; a "central server" is no longer required, since each node in effect performs the roles of both server and client. The replacement of the server with a variety of interconnected links enables data to arrive at its destination through a variety of possible paths. If a system looses its connection to the network, information can still arrive at its destination via an alternative route. This level of resilience is a clear advantage over the classic model, since information would not be able to pass between clients if their connection to the server was lost.

To join the network, a client must simply connect to any computer already in the network, as opposed to relying on one main system that could potentially become congested or suffer from downtime. Thus if one connection attempt fails, another to any computer in the network is equally viable, as communication is possible irrespective of location. Data sent by the new client can travel anywhere on the network, therefore its point of connection is irrelevant. Simply, as long as a network exists to connect to, a client is able to join at any point.

A node is defined as any computer connected to the network. XPN nodes come in three dynamic types; Peer, Server and Router. A node can adopt any of the roles depending on the network topology required. For example, a traditional Client-Server model might be adopted for a hierarchical system, Peer-to-Peer in a 'flat' networking environment where all members of the network are 'equal', or some combination of the two.

Generally speaking, Peers connect to Servers or other Peers, with the traffic between servers being handled by Routers to streamline data flow. A Router is a node with multiple connections to Servers, a high speed hub specifically designed to route data effectively. They often serve as the 'nexus' or core of a network, providing a multitude of connections to other parts of the network, so that Servers do not have to establish these connections individually. Servers are usually responsible for a group of Peers, but this in no way limits Peers from establishing their own alternative connections into the network.

Scenario 1
If a client of Server A wishes to send data to a client of Server B, information is first transmitted by the sending client to Server A, then passed to Server B to relay to its destination.

If instead, a client on a third server, C, connected to B was the destination, the intermediary server B would be effectively acting as a router. If such a scenario were to persist, Server B might decide to alter its role, demonstrating how the network's structure can change depending on the nature of its traffic. By adapting to an alteration in their surroundings, nodes streamline the overall flow of data through the network by prioritising resources where they are needed most.

Scenario 2
Assume Server B in the diagram below is processing a high volume of traffic, only a small percentage of which is generated between its own clients, with the remainder passing straight through the node.

To adapt, Server B changes its role on-the-fly to a Router, in order to more effectively dedicate its resources to channeling traffic between servers A and C. In such a scenario, its clients would be seamlessly transferred to either A or C automatically, leaving the router with established connections only to servers.

Server-to-server transfer of clients is achieved without service interruption by establishing a second connection from a client to its destination server before its original connection is terminated, thereby allowing the flow of data to continue uninterrupted.

In another instance, if two particular clients on separate servers were creating large amounts of cross-network traffic between them, they might be relocated to the same server so that inter-server traffic is minimised. Such "intelligent load balancing" is featured in the free Nexus Network Manager, allowing clients which exceed a certain bandwidth allocation to be transferred to other nodes to aid network health.

Often undue emphasis is placed on various routing technologies' impact on the performance or reliability of network traffic. In addition to its low-level congestion-reduction measures, XPN uses a simple but effective routing method. When enabled, a packet's route through the network is embedded in its header so that each node along its path is able to build-up a list of valid routes up to that point. These are used in reverse later to decide the best connection through which to send future traffic.

Routing can be enabled on a per-application basis, but every node respects the routing preference of those it routes data for, regardless of its individual preference.

XPN technology is being implemented throughout our product line.
Some of these applications are listed below.

Neptune Web Server
WebGate
Nexus Network Manager
Swift Home File Sharing
Equinox Shell
xStore