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content:tech:rhizome [07/04/2013 22:29]
Andrew Bettison [Rhizome's data model] much improved
content:tech:rhizome [21/02/2016 22:52] (current)
Andrew Bettison Re-word [Technical documentation] section; remove link to GitHub (maintenance burden)
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 ====== Rhizome ====== ====== Rhizome ======
  
-**Rhizome** is the resilient file distribution system developed by [[:|The Serval Project]].  It forms the basis of all non-[[http://en.wikipedia.org/wiki/Connection_oriented|connection-oriented]] services provided by [[:content:technologies:servalmesh|Serval Mesh]], such as [[:content:technologies:meshms|text messaging]], file sharing, voice mail, and automatic software upgrades. +**Rhizome** is resilient content distribution system developed by [[:|The Serval Project]].  It forms the basis of all non-[[http://en.wikipedia.org/wiki/Connection_oriented|connection-oriented]] services provided by [[:content:servalmesh:|Serval Mesh]], such as [[meshms|text messaging]], file sharing, voice mail, and automatic software upgrades. 
  
 +==== Technical documentation====
 +
 +**[[Rhizome API]]** contains links to the authoritative [[:content:dev:techdoc|technical documentation]] of the Rhizome HTTP REST API, which resides in the source code of the [[:content:servaldna:development|Serval DNA]] software, and should be used in preference to the older documents on this wiki.
 +
 +Other relevant information:
 +
 +  * [[Security Framework]] describes the cryptographic features of Rhizome
 +  * [[:content:activity:naf4]] describes the original development of the Rhizome HTTP REST API (beware: some technical details are out of date; refer to [[Rhizome API]] for current documentation)
  
 ==== Purpose and features ==== ==== Purpose and features ====
  
   * Rhizome is a **[[http://en.wikipedia.org/wiki/Store_and_forward|store and forward]]** service for transporting units of data called **payloads** ("files") between **applications** running on nodes in a digital [[http://en.wikipedia.org/wiki/Telecommunications_network|telecommunications network]]   * Rhizome is a **[[http://en.wikipedia.org/wiki/Store_and_forward|store and forward]]** service for transporting units of data called **payloads** ("files") between **applications** running on nodes in a digital [[http://en.wikipedia.org/wiki/Telecommunications_network|telecommunications network]]
-  * Rhizome is designed for [[http://en.wikipedia.org/wiki/Wireless_mesh_network|wireless mesh networks]] such as [[:content:technologies:mdp|MDP]] in the [[:content:technologies:servalmesh|Serval Mesh]], but can also be used within a fixed network infrastructure+  * Rhizome is designed for [[http://en.wikipedia.org/wiki/Wireless_mesh_network|wireless mesh networks]] such as [[MDP]] in the [[:content:servalmesh:|Serval Mesh]], but can also be used within a fixed network infrastructure
   * Rhizome guarantees that payloads will remain intact wherever they are transported   * Rhizome guarantees that payloads will remain intact wherever they are transported
   * Rhizome makes no guarantees about delivery time or eventual arrival   * Rhizome makes no guarantees about delivery time or eventual arrival
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   * Users do not use Rhizome directly, but //indirectly via [[http://en.wikipedia.org/wiki/Application_software|applications]]// which use Rhizome as their data transport   * Users do not use Rhizome directly, but //indirectly via [[http://en.wikipedia.org/wiki/Application_software|applications]]// which use Rhizome as their data transport
   * Current Rhizome applications:   * Current Rhizome applications:
-    * [[:content:technologies:meshms|MeshMS]], the simple text messaging service of the [[:content:technologies:servalmesh|Serval Mesh]] app for Android+    * [[MeshMS]], the simple text messaging service of the [[:content:servalmesh:|Serval Mesh]] app for Android
     * [[:content:servalmaps:|Serval Maps]], an Android app produced by the [[:|Serval Project]], uses Rhizome to share geo-tagged data like photos and documents     * [[:content:servalmaps:|Serval Maps]], an Android app produced by the [[:|Serval Project]], uses Rhizome to share geo-tagged data like photos and documents
-    * the [[:content:technologies:servalmesh|Serval Mesh]] app for Android uses Rhizome to distribute software upgrades +    * the [[:content:servalmesh:|Serval Mesh]] app for Android uses Rhizome to distribute software upgrades 
-    * the file sharing service of the [[:content:technologies:servalmesh|Serval Mesh]] app for Android is a simple UI for sharing, browsing and saving/viewing non-MeshMS content in Rhizome +    * the file sharing service of the [[:content:servalmesh:|Serval Mesh]] app for Android is a simple UI for sharing, browsing and saving/viewing non-MeshMS content in Rhizome 
-    * [[:content:technologies:servalsam|Serval SAM]] is a crowd survey app for Android that allows the user to fill in an [[http://opendatakit.org/|Open Data Kit]] form and uses Rhizome to transport completed forms to a central collection server +    * [[Serval SAM]] is a crowd survey app for Android that allows the user to fill in an [[http://opendatakit.org/|Open Data Kit]] form and uses Rhizome to transport completed forms to a central collection server 
-    * [[:content:technologies:sensorlogger|Sensor Logger]], an Android app produced by the [[:|Serval Project]], uses Rhizome to send continuous accelerometer logs to the [[:content:seniordevs:servalhq|Serval HQ]] central collection server +    * [[Sensor Logger]], an Android app produced by [[:content:about]], uses Rhizome to send continuous accelerometer logs to the [[:content:seniordevs:servalhq|Serval HQ]] central collection server 
   * Future applications may include:   * Future applications may include:
     * voice mail     * voice mail
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 ==== Rhizome's data model ==== ==== Rhizome's data model ====
  
-Every Rhizome **payload** ("file") is accompanied by some structured meta data called a **manifest**: +Every file distributed by Rhizome ("payload") is accompanied by some structured meta-data called a **[[Rhizome manifest|manifest]]**.
-  * some meta data is supplied by the originating application to accompany the payload, but is not used by Rhizome, eg, File name, Content MIME type +
-  * some meta data is created and used by Rhizome to identify, prioritise, route and expire the payload, eg, Bundle ID, Bundle Version, Payload size, Payload hash (digest) +
-  * some meta data is supplied by the originating application and is used by Rhizome to prioritise, route and expire the payload, eg, sender and recipient [[:content:technologies:sid|Serval Identities]], [[:content:technologies:rhizome:journal|Journal head]], [[:content:technologies:rhizome:boundingcircle|Bounding circle]], [[:content:technologies:rhizome:lifetime|Lifetime]]+
  
-A Rhizome **bundle** = **manifest** + **payload**+payload plus a [[Rhizome manifest|manifest]] together form a **[[Rhizome bundle]]**.
  
-== Rhizome manifest ==+==== Rhizome's data transport ====
  
-The Rhizome manifest is a set of key-value pairs called **fields**,  A manifest is stored and transmitted in either text or binary representation:+  * 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 autonomouslyie, 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
  
-  * The **text manifest** is the original implementation +== Rhizome store ==
-  * The original text format used [[http://en.wikipedia.org/wiki/ASCII|US-ASCII]] character encoding and may be upgraded to [[http://en.wikipedia.org/wiki/UTF-8|Unicode UTF-8]] when needed +
-  * The **[[:content:technologies:rhizome:binarymanifest|binary manifest]]** is not yet implemented +
-  * Here are some sample (historical) implementations of the text manifest from [[:content:software:techroadmap:releases:version090|Serval Mesh release 0.90 "Shiny"]]: +
-    * [[https://github.com/servalproject/serval-dna/blob/batphone-release-0.90/rhizome_bundle.c#L87|rhizome_bundle.c]] in the [[:content:technologies:servaldna|Serval DNA]] source code +
-    * [[https://github.com/servalproject/batphone/blob/0.90/src/org/servalproject/rhizome/RhizomeManifest.java|RhizomeManifest.java]] from the [[:content:process:servalmesh|Batphone]] source code +
-  * An example of a text manifest:<code> +
-recipient=FFA9248AF3848D3FD3FCCCF339C3AF9D574A3D6C9BA2FB3F6C587FB25C479F64 +
-sender=49259519777EF680E20C6ED05FA4B51EB86DDDC7D175A3B15B7AF2F9E446B54E +
-service=MeshMS1 +
-date=1351559461139 +
-id=E6856342C6F2DAFE560C18FE85EC1CCDAB5457D50BFDAE7FCF271D5B9C0E4123 +
-BK=8CEA7C075CD15F1CC8AA1D0F5E263ACD4ECEE6A870A87D90BBD68A4968B8939C +
-crypt=0 +
-filesize=39 +
-filehash=254CDA75BF5E8CA6B5498FE20C33F120BA50464B7BC7B09FD6C41D10722F1B0844137E55F073FCDC7A4388EA48DD282B2C5A6D42931C84E9E076A2BFA8A21BC0 +
-version=1351559461142 +
-</code> +
-  * Every manifest contains one or more cryptographic signatures to prevent tampering +
-    * Rhizome nodes will reject manifests with no signature or a signature that does not verify +
-    * Only the original creator (author) of the manifest may possess the signing key, so is the only party able to modify the manifest (publish newer Bundle Versions with the same Bundle ID)+
  
-== Backward and forward compatibility ==+  * 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 [[http://www.sqlite.org/|SQLite]] for the database
  
-Both Rhizome manifest representations (text and binary) are designed to allow upgrades.+== Rhizome Rank ==
  
-[[http://en.wikipedia.org/wiki/Forward_compatibility|Forward compatibility]] arises from an extensible manifest data format that allows unrecognised fields to be skipped: +  Every Rhizome node maintains its own ordered list of all the manifests in its store, called the **Rank** 
-  The text manifest uses a special field delimiter (newline) that cannot appear in any field value +  * Every Rhizome node attempts to fetch missing payloads from neighbouring nodesin order of rank 
-  * The [[:content:technologies:rhizome:binarymanifest|binary manifest]] stores the length of every field +  * Every Rhizome node recovers local storage space by evicting its lowest ranked payloads 
-  * Every Rhizome node uses only the manifest fields it recognises and successfully parsesand ignores any it does not (possibly logging a warning) +  * A bundle's position in the rank depends on meta data in the manifest and local node statewhich may include: 
-  * Every Rhizome node always stores and transmits the manifest intactwithout modification, including any unrecognised fields+    * own Serval Identities 
 +    * Serval Identities of recently reachable nodes 
 +    * current time 
 +    * current or recent geographic location
  
-[[http://en.wikipedia.org/wiki/Backward_compatible|Backward compatibility]] is done using a standard replace/deprecate/delete process: +== Network connections ==
-  * The format and meaning of existing fields is never changed +
-  * Software upgrades may introduce a new field that can coexist with the older field(s) it supercedes +
-  * For a while, software upgrades create manifests containing the deprecated field and the newer field +
-  * Eventually a software release and all following releases cease to insert the deprecated field +
-  * This provides a time window during which the [[:content:technologies:autoupgrade|automatic field upgrade]] has a chance to upgrade all the Rhizome software in the field+
  
-== Sender and recipient == +  * Rhizome nodes may transfer bundles using **[[http://en.wikipedia.org/wiki/Network_layer|network layer]]** connections over established networks, eg, [[http://en.wikipedia.org/wiki/Transmission_Control_Protocol|TCP]] or [[http://en.wikipedia.org/wiki/User_Datagram_Protocol|UDP]] or [[http://en.wikipedia.org/wiki/Http|HTTP]] over public Internet or cellular GSM 
- +  * Adjacent Rhizome nodes may transfer bundles over **[[http://en.wikipedia.org/wiki/Data_link_layer|data link layer]]** connections, eg, [[MDP]] to [[:content:servalmesh:|Serval Mesh]] devices within Fi-Fi range
-  If a bundle does not indicate the [[:content:technologies:sid|Serval Identity]] of its intended recipientit is for general consumption (broadcast) +
-  * If a bundle does not indicate the [[:content:technologies:sid|Serval Identity]] of its sender, then it is of unknown origin (anonymous) +
- +
-=== Put these points somewhere else === +
- +
-  * A manifest may be present on many nodes at a time +
-  * A payload may be present 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 +
-  Rhizome does not modify any manifest once it is created +
-  Rhizome does not modify any payload +
- +
- +
-==== Rhizome nodes ==== +
- +
-  * A **Rhizome node** is any network node (device) that is running the Rhizome software +
-  * Payloads and manifests are copied directly from node to node using network transfers +
-  * Payloads and manifests are stored on nodes using volatile (RAM) or non-volatile (Flash, disk) local storage +
-  * Each Rhizome node actively transmits its recently acquired manifests to its neighbours +
-  * Each Rhizome node records all received manifests in a sorted list called the **rank** +
-  * Each Rhizome node attempts to acquire the payloads of its highest ranked manifests from neighbouring nodes +
-  * Each Rhizome node recovers local storage space by evicting its lowest ranked payloads and manifests+
  
 ==== Neutrality ==== ==== Neutrality ====
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   * Rhizome does not rank (prioritise) based on the content of payloads   * Rhizome does not rank (prioritise) based on the content of payloads
  
-==== Bundle integrity ==== 
  
-  * Rhizome creates a random 256-bit Elliptic Curve private key for every bundle, called the **Bundle Secret** or **BS** 
-  * The 256-bit public key derived from the Bundle Secret is called the **Bundle ID** or **BID** 
-  * Rhizome does not reveal the Bundle Secret to any other application or node 
-  * Rhizome computes the 512-bit SHA512 hash of the payload, called the **Payload Hash** or **PH** (also **File Hash** or **FH**) 
-  * At injection, Rhizome inserts the Payload Hash into the bundle's manifest 
-  * Rhizome signs every complete manifest using the Bundle Secret 
-  * Rhizome nodes will only store and transmit manifests with valid signatures 
-  * Only an application possessing the original Bundle Secret can alter the manifest or payload 
- 
-The net result of Rhizome's crytpo system is that: 
-  * any party may create a new bundle (with a new Bundle ID) 
-  * only the originating party may modify the manifest or payload of an existing bundle (keeping the same Bundle ID) 
-  * thus, once a bundle is created, all new payloads with the same Bundle ID are guaranteed to be from the same original sender 
- 
-==== Payload security ==== 
- 
-  * Rhizome can optionally **encrypt** a payload during injection with a one-way asymmetric cipher using the recipient's [[:content:technologies:sid|Serval ID]] public key 
-  * Rhizome can optionally **encrypt** a payload during injection with a two-way session cipher constructed using the sender's and recipient's [[:content:technologies:sid|Serval ID]] public keys 
-  * Rhizome will **decrypt** an encrypted payload during extraction if the node possesses the recipient's [[:content:technologies:sid|Serval ID]] secret key 
-  * The Payload Hash of an encrypted payload is the SHA512 hash of the encrypted form, not the clear text form 
-  
 ==== User intervention ==== ==== User intervention ====
  
   * Users may improve the local capacity of Rhizome by operating nodes with high storage capacity   * Users may improve the local capacity of Rhizome by operating nodes with high storage capacity
   * Users may improve the reach of Rhizome by periodically moving a node between distant locations   * Users may improve the reach of Rhizome by periodically moving a node between distant locations
- 
-==== Network connections ==== 
- 
-  * Rhizome nodes may communicate using **[[http://en.wikipedia.org/wiki/Network_layer|network layer]]** connections over established networks, eg, [[http://en.wikipedia.org/wiki/Transmission_Control_Protocol|TCP]] or [[http://en.wikipedia.org/wiki/User_Datagram_Protocol|UDP]] or [[http://en.wikipedia.org/wiki/Http|HTTP]] over public Internet or cellular GSM 
-  * Adjacent Rhizome nodes may communicate over **[[http://en.wikipedia.org/wiki/Data_link_layer|data link layer]]** connections, eg, [[:content:technologies:mdp|MDP]] to [[:content:technologies:servalmesh|Serval Mesh]] devices within Fi-Fi range 
  
 ==== Architecture ==== ==== Architecture ====
  
-Rhizome is currently implemented as part of the [[:content:technologies:servaldna|Serval DNA]] daemon.+Rhizome is currently implemented as part of the [[:content:servaldna:|Serval DNA]] daemon.
  
 ==== The name "Rhizome" ==== ==== The name "Rhizome" ====
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 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 [[http://en.wikipedia.org/wiki/Rhizome|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 [[http://en.wikipedia.org/wiki/Elymus_repens|couch grass]] into their garden knows how obstinate a rhizome can be. 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 [[http://en.wikipedia.org/wiki/Rhizome|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 [[http://en.wikipedia.org/wiki/Elymus_repens|couch grass]] into their garden knows how obstinate a rhizome can be.
  
-Curiously (but not coincidentally) some of the principles of the [[http://en.wikipedia.org/wiki/Rhizome_(philosophy)|rhizomatic]] philosophy of thought also describe the behaviour of the Rhizome file distribution system.+==== Prototypes ==== 
 + 
 +The [[Rhizome Retriever]] was the first prototype of the manifest-payload distribution system.
  
content/tech/rhizome.1365398974.txt.gz · Last modified: 07/04/2013 22:29 by Andrew Bettison