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86 lines
3.4 KiB
Markdown
86 lines
3.4 KiB
Markdown
---
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title: RPC Protocol
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description: An overview of the RPC protocol used in Veilid
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weight: 24
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layout: subpage
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---
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### RPC Summary
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<ul>
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<li>
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<h4>Schema Language is Cap'n Proto</h4>
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<a href="https://capnproto.org/">Cap’n Proto</a> is designed for deserialization speed and schema evolution. Flexible and well supported in Rust.
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</li>
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<li>
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<h4>RPC is fully in-schema and documented</h4>
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Both ‘Question/Answer’ and ‘Statement’ RPC modes are supported. All schema fields are documented.
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</li>
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<li>
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<h4>RPC fully supports Private Routing</h4>
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All private routing structures are expressed in the RPC schema itself, no magic encrypted blobs.
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</li>
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<li>
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<h4>Schema Evolution is built-in</h4>
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Fields can be added and removed with full backward and forward compatibility. New features won’t break older Veilid nodes.
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</li>
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<li>
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<h4>RPC Schema is cryptography-independent</h4>
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As cryptosystems change, the language spoken by Veilid nodes remains the same.
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</li>
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</ul>
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### Distributed Hash Table
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Distributed Hash Tables are a way of storing data in records that have keys that are close to nodes in the network.
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#### DHT Is Just ‘Search’
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It may look complicated, but all the DHT algorithms out there are just ‘search’ algorithms. Finding data that is stored on some node somewhere out there.
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#### Improving Search
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We built a better DHT by making both search and data locality more relevant. Veilid synchronizes popular data when nodes come and go from the network.
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<img src="/img/dht-diagram.png" alt="a tree diagram for the search ability" class="img-fluid lightbox">
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Locating a node by its ID. Here the node with the prefix 0011 finds the node with the prefix 1110 by
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successively learning of and querying closer and closer nodes. The line segment on top represents the
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space of 160-bit IDs, and shows how the lookups coverge to the target node. Below we illustrate RPC messages
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made by 1110. The first RPC is to node 101, already known to 1110. Subsequent RPCs are to nodes returned by the
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previous RPC.
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#### DHT Schema
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Veilid DHT is built using GetValue and SetValue RPC operations. Nodes can opt out of DHT storage if they do not want to participate.
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Veilid DHT records have schemas that define subkeys that are individually addressable and can have multiple writers.
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DHT record subkeys have sequence numbers and are eventually consistent across multiple writes and background synchronizations.
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<div class="row gx-5 gy-3 mb-3">
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<div class="col-12 col-lg-6">
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<figure class="h-100">
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<img src="/img/dht-dflt-framed.png" alt="a diagram showing key-value pairs" class="img-fluid lightbox">
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<figcaption>
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<p>Veilid Default DHT Schema - DFLT</p>
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<p>To zoom in on the details, <a href="/img/dht-dflt-framed.png">view the image directly</a>.</p>
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</figcaption>
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</figure>
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</div>
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<div class="col-12 col-lg-6">
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<figure class="h-100">
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<img src="/img/dht-smpl.png" alt="a diagram showing key-value pairs, but with more fields" class="img-fluid lightbox">
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<figcaption>
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<p>Veild Simple DHT Schema - SMPL</p>
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<p>To zoom in on the details, <a href="/img/dht-smpl.png">view the image directly</a>.</p>
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</figcaption>
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</figure>
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</div>
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</div>
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<div class="focus-text">
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<p>The DHT gives you full control over your data</p>
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<p>Our DHT is not based on a blockchain or a coin </p>
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<p>Popular data becomes more available automatically </p>
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</div>
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