Rhizome
Technical documentation
Rhizome API contains links to the authoritative technical documentation of the Rhizome HTTP REST API, which resides in the source code of the Serval DNA software, and should be used in preference to the older documents on this wiki.
Other relevant information:
Purpose and features
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Rhizome guarantees that payloads will remain intact wherever they are transported
Rhizome makes no guarantees about delivery time or eventual arrival
Rhizome makes its best effort to transport payloads to wherever they are wanted, subject to the constraints of the network (topology, bandwidth) and its nodes (storage, battery), without favouring any payloads above others of equal kind
Rhizome is neutral with respect to originating and receiving nodes, applications, and payload content
Rhizome uses cryptography to preserve the integrity and privacy of payloads
Rhizome protects anonymous senders by not storing or transmitting information that may allow senders to be traced, even on the originating device
Rhizome functions without centralised infrastructure such as well-known servers or a persistent network connection
Rhizome can be configured to use central servers to improve efficiency and reach
Rhizome applications
Users do not use Rhizome directly, but
indirectly via applications which use Rhizome as their data transport
Current Rhizome applications:
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the
Serval Mesh app for Android uses Rhizome to distribute software upgrades
the file sharing service of the
Serval Mesh app for Android is a simple UI for sharing, browsing and saving/viewing non-MeshMS content in Rhizome
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Future applications may include:
voice mail
disaster response situational awareness
medical or environmental sensor data collection
collaborative text editing and whiteboarding
distributed document management
citizen journalism
classroom and remote teaching tools
group chat
Wikipedia caching
Applications inject data into Rhizome by supplying a payload and some meta data
Applications extract data from Rhizome, receiving the payload and all meta data
Rhizome's data model
Every file distributed by Rhizome (“payload”) is accompanied by some structured meta-data called a manifest.
A payload plus a manifest together form a Rhizome bundle.
Rhizome's data transport
A Rhizome node is any network node (device) that is running the Rhizome software
A Rhizome node exchanges manifests and payloads directly with adjacent nodes on the network
Rhizome bundles are transferred between nodes automatically and autonomously, ie, without user intervention, using any available network connection
A manifest may be stored on many nodes at a time
A payload may be stored on many nodes at a time
A manifest may persist for any length of time on any node
A payload may persist for any length of time on any node
Each Rhizome node advertises its recently acquired bundles to its neighbours
Rhizome store
A Rhizome node contains a Rhizome store
A Rhizome store is a database containing payloads indexed by PH (Payload Hash) and manifests indexed by BID (Bundle ID)
A Rhizome store may reside in volatile (RAM) or non-volatile (Flash, disk) local storage
The original implementation of the Rhizome store used
SQLite for the database
Rhizome Rank
Every Rhizome node maintains its own ordered list of all the manifests in its store, called the Rank
Every Rhizome node attempts to fetch missing payloads from neighbouring nodes, in order of rank
Every Rhizome node recovers local storage space by evicting its lowest ranked payloads
A bundle's position in the rank depends on meta data in the manifest and local node state, which may include:
Network connections
Rhizome nodes may transfer bundles using
network layer connections over established networks, eg,
TCP or
UDP or
HTTP over public Internet or cellular GSM
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Neutrality
Rhizome interprets meta data uniformly, regardless of the originating or receiving application
Rhizome ranks (prioritises) payloads using uniform rules that do not depend on the originating or receiving application
Rhizome software does not encapsulate any application-specific logic
Rhizome does not record the originating or transited nodes of any payload, so nodes cannot rank (prioritise) payloads based on point of origin, only on available meta data
Rhizome does not rank (prioritise) based on the content of payloads
User intervention
Architecture
Rhizome is currently implemented as part of the Serval DNA daemon.
The name "Rhizome"
Once a file is inserted into Rhizome, it can be notoriously difficult to eradicate. This is analogous to a biological process of vegetative reproduction: a rhizome is an underground plant stem with the ability to send out shoots which develop into new plants. If a rhizome is cut into smaller pieces, each piece can grow into a new organism. Anybody who has battled the incursion of couch grass into their garden knows how obstinate a rhizome can be.
Prototypes
The Rhizome Retriever was the first prototype of the manifest-payload distribution system.