Architecture - SkycoinProject/skywire GitHub Wiki

This entry elaborates on the high-level architecture of Skywire. Since we use certain networking terms idiosyncratically, please check out the Glossary as well.

Architecture

Skywire is a decentralized and private network. Skywire separates the data and control plane of the network and assigns the tasks of network coordination and administration to dedicated services, while the nodes follow the rules that were created by the control plane and execute them.

Currently Skywire functions as an overlay network. That means, it uses the existing internet infrastructure to create the Skywire network. In the future, Skywire can become its own independent network, when the adoption of the project has grown and there is a more dense distribution of hardware.

The core of Skywire is the Skywire node which hosts applications and is the gateway to use the network. It establishes connections, called transports, to other nodes, requests the setup of routes and forwards packets for other nodes on a route. The Skywire node exposes an API to applications for using the networking protocol of Skywire.

In order to detach control plane tasks from the network nodes, there are 3 other services that maintain a picture of the network topology, calculate routes (currently based on the number of hops, but will be extended to other metrics) and set the routing rules on the nodes.

The transport discovery maintains a picture of the network topology, by allowing Skywire nodes to advertise transports that they established with other nodes. It also allows to upload a status to indicate whether a given transport is currently working or not.

On the basis of this information the route finder calculates the most efficient route in the network. Nodes request a route to a given public key and the route finder will calculate the best route and return the transports that the packet will be sent over to reach the intended node.

This information is sent from a node to the Setup Node, which sets the routing rules in all nodes along a route. Skywire nodes determine, which nodes they accept routing rules from, so only a whitelisted node can send routing rules to a node in the network. The only information the Skywire node gets for routing is a Routing ID and an associated rule that defines which transport to send a packet to (or to consume the packet). Therefore nodes along a route only know the last and next hop along the route, but not where the packet originates from and where it is sent to. Skywire supports source routing, so nodes can specify a path that a packet is supposed to take in the network.

There are currently two types of transports that nodes can use. The messaging transport is a transport between two nodes that uses an intermediary messaging server to relay packets between them. The connection to a specific node and the connection to a messaging server is facilitated by a discovery service, that allows nodes to advertise the messaging servers over which they can be contacted. This transport is used by the setup node to send routing rules and can be used for other applications as well. It allows nodes behind NATs to communicate. The second transport type is TCP, which sets up a connection between two servers with a public IP. This transport type is experimental and an automated setup therefore not yet implemented. More transport types will be supported in the future and custom transport implementations can be written for specific use cases.