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diff --git a/content/en/docs/Concepts/elements.md b/content/en/docs/Concepts/elements.md deleted file mode 100644 index a803065..0000000 --- a/content/en/docs/Concepts/elements.md +++ /dev/null @@ -1,90 +0,0 @@ ---- -title: "Elements of a recursive network" -author: "Dimitri Staessens" -date: 2019-07-11 -weight: 2 -description: > - The building blocks for recursive networks. ---- - -This section describes the high-level concepts and building blocks are -used to construct a decentralized [recursive network](/docs/what): -layers and flows. (Ouroboros has two different kinds of layers, but -we will dig into all the fine details in later posts). - -A __layer__ in a recursive network embodies all of the functionalities -that are currently in layers 3 and 4 of the OSI model (along with some -other functions). The difference is subtle and takes a while to get -used to (not unlike the differences in the term *variable* in -imperative versus functional programming languages). A recursive -network layer handles requests for communication to some remote -process and, as a result, it either provides a handle to a -communication channel -- a __flow__ endpoint --, or it raises some -error that no such flow could be provided. - -A layer in Ouroboros is built up from a bunch of (identical) programs -that work together, called Inter-Process Communication (IPC) Processes -(__IPCPs__). The name "IPCP" was first coined for a component of the -[LINCS] -(https://www.osti.gov/biblio/5542785-delta-protocol-specification-working-draft) -hierarchical network architecture built at Lawrence Livermore National -Laboratories and was taken over in the RINA architecture. These IPCPs -implement the core functionalities (such as routing, a dictionary) and -can be seen as small virtual routers for the recursive network. - -{{<figure width="60%" src="/docs/concepts/rec_netw.jpg">}} - -In the illustration, a small 5-node recursive network is shown. It -consists of two hosts that connect via edge routers to a small core. -There are 6 layers in this network, labelled __A__ to __F__. - -On the right-hand end-host, a server program __Y__ is running (think a -mail server program), and the (mail) client __X__ establishes a flow -to __Y__ over layer __F__ (only the endpoints are drawn to avoid -cluttering the image). - -Now, how does the layer __F__ get the messages from __X__ to __Y__? -There are 4 IPCPs (__F1__ to __F4__) in layer __F__, that work -together to provide the flow between the applications __X__ and -__Y__. And how does __F3__ get the info to __F4__? That is where the -recursion comes in. A layer at some level (its __rank__), will use -flows from another layer at a lower level. The rank of a layer is a -local value. In the hosts, layer __F__ is at rank 1, just above layer -__C__ or layer __E_. In the edge router, layer __F__ is at rank 2, -because there is also layer __D__ in that router. So the flow between -__X__ and __Y__ is supported by flows in layer __C__, __D__ and __E__, -and the flows in layer __D__ are supported by flows in layers __A__ -and __B__. - -Of course these dependencies can't go on forever. At the lowest level, -layers __A__, __B__, __C__ and __E__ don't depend on a lower layer -anymore, and are sometimes called 0-layers. They only implement the -functions to provide flows, but internally, they are specifically -tailored to a transmission technology or a legacy network -technology. Ouroboros supports such layers over (local) shared memory, -over the User Datagram Protocol, over Ethernet and a prototype that -supports flows over an Ethernet FPGA device. This allows Ouroboros to -integrate with existing networks at OSI layers 4, 2 and 1. - -If we then complete the picture above, when __X__ sends a packet to -__Y__, it passes it to __F3__, which uses a flow to __F1__ that is -implemented as a direct flow between __C2__ and __C1__. __F1__ then -forwards the packet to __F2__ over a flow that is supported by layer -__D__. This flow is implemented by two flows, one from __D2__ to -__D1__, which is supported by layer A, and one from __D1__ to __D3__, -which is supported by layer __B__. __F2__ will forward the packet to -__F4__, using a flow provided by layer __E__, and __F4__ then delivers -the packet to __Y__. So the packet moves along the following chain of -IPCPs: __F3__ --> __C2__ --> __C1__ --> __F1__ --> __D2__ --> __A1__ ---> __A2__ --> __D1__ --> __B1__ --> __B2__ --> __D3__ --> __F2__ --> -__E1__ --> __E2__ --> __F4__. - -{{<figure width="40%" src="/docs/concepts/dependencies.jpg">}} - -A recursive network has __dependencies__ between layers in the -network, and between IPCPs in a __system__. These dependencies can be -represented as a directed acyclic graph (DAG). To avoid problems, -these dependencies should never contain cycles (so a layer I should -not directly or indirectly depend on itself). The rank of a layer is -defined (either locally or globally) as the maximum depth of this -layer in the DAG. |