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94 lines
4.1 KiB
Plaintext
94 lines
4.1 KiB
Plaintext
Copper Protocol
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20kdc, 2017
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Copper is a simple to implement networking protocol based on names.
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This is it's sole purpose.
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It can be used in various contexts, though it is not suitable as a
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secure peer-to-peer networking protocol where all actors are untrusted.
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Rather, Copper is better for the situation of the current internet -
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hierarchial structures (operated by semi-trusted parties, with
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encryption used to hide information from them as appropriate),
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with arbitary network structure at the fully-trusted-network level.
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Copper addresses are names.
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In the context of a system not implementing a hierarchial gateway,
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this is as much about Copper addressing as matters.
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Copper base packets contain 4 fields.
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One byte indicating how many nodes have retransmitted the message
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(the original sender should use 0),
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A name (as a length-minus-1-byte-prefixed-string),
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another name (in the same format),
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and the rest is data.
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Copper packet data may be up to 1507 bytes long.
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1500 in-relib data bytes + 7 relib bytes.
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This makes the user's life easier by having an easy to remember MTU from within relib of 1500 bytes.
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This does not include header data, which may be up to (256*2) + 3 bytes long.
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Loop detection should performed by checking if a packet exactly the same has
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been seen recently - other rejection, alteration and routing measures
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are up to the implementer.
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Signalling is inadvisable - Copper is primarily meant to allow creating
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internally "partyline" OpenComputers in-game networks with named nodes
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and some semblance of routing or structure.
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Should a situation be dire enough,
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hierarchial networks (described in file 2, 'protocol.1'),
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and custom routing software in general,
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can be used to split networks however the system requires.
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--- The Broadcast Address
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The Broadcast Address is a possible feature which may or may not be actually used.
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It has been implemented with forward compatibility by simply ensuring that "*" is never put into the
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routing cache (so it's always broadcast).
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The idea is that if a name is directly equal to "*", it should be broadcast around the local network.
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Notably, it is completely incompatible with reliability mechanisms for probably obvious reasons,
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but can still be used in networks running the Reliability Layer via the 'unreliable' escape-hatch.
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Hierarchial gateways do not need modification on the from-child rules
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("*" is local to them there,
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"<*" or such is dealt with correctly by the normal rules),
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but in the from-parent rules it may be desirable to forward "*" to child networks.
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Or not.
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--- OpenComputers Usage
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Copper should be used on port 4957.
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Messages should be two part.
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The first part should always be "copper",
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the second part should always be the actual data.
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All available methods of communication should be open to Copper unless explicitly noted otherwise -
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for example, Linked Cards are one of the methods that could be used for purpose-built wireless links.
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--- Overlay Network Usage
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In this case, Copper messages may be relayed however the users see fit - but port 4957 UDP messages
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are a good fit on the basis that they are a parallel.
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To prevent annoyed ISPs, the best networking method is a looped daisy-chain.
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This provides a bit of redundancy while avoiding ISP-ire-causing mass fanout.
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Network messages should be accepted from any IP address, as spoofing is perfectly doable anyway.
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--- Serial Port/TCP Usage
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Copper packets should just be written out on the connection, prefixed with a big-endian two-byte
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unsigned integer specifying the size.
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--- Hybrid Usage
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The connection between OpenComputers and Copper can be performed with a TCP gateway between the
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Minecraft server and Copper server on the same computer, or via designated Copper HTTP event feeds
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of some form, or whatever.
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It doesn't really matter how the data is transmitted here, since it's just a gateway.
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Possibly consider integrating a hierarchial gateway into the OpenComputers/world bridge.
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ERRATA:
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The data MTU was described as 1506 bytes due to an error in the protocol.2 document.
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It should be 1507 to fit 1500 relib byets and the 7-byte header.
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