mfahampshire
d07f9c8fad
* rework of sdk docs * update integration docs + bit of overall restructure * remove debug logger from tool
83 lines
3.6 KiB
Plaintext
83 lines
3.6 KiB
Plaintext
import { Callout } from 'nextra/components'
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# Message Queue
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<Callout type="info">
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Although good to understand how the Nym Client works under the hood, this information is only of practical use if you're using the `Mixnet` module of the RustSDK and interacting with the SDK Mixnet Client at a low level. This is all mostly abstracted away with the `MixSocket`, `MixStream`, and `IpMixStream` abstractions.
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</Callout>
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## Sphinx Packet Streams
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Clients, once connected to the Mixnet, **are always sending traffic into the Mixnet**; as well as the packets that you as a developer are sending from your application logic, they send [cover traffic](../../network/concepts/cover-traffic) at a constant rate defined by a Poisson process. This is part of the network's mitigation of timing attacks.
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There are two constant streams of sphinx packets leaving the client at the rate defined by the Poisson process.
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- one that is solely cover traffic
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- one that sends a mixture of cover and 'real' traffic
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```mermaid
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---
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config:
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theme: neo-dark
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layout: elk
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title: Cover Traffic Stream
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---
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sequenceDiagram
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box Local Machine
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participant App Logic
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participant Nym Client
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end
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participant Entry Gateway
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loop Cover Traffic Stream
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Nym Client->>Nym Client: Delay
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Nym Client->>Entry Gateway: Cover traffic
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end
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```
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```mermaid
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---
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config:
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theme: neo-dark
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layout: elk
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title: Mixed Stream
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---
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sequenceDiagram
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box Local Machine
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participant App Logic
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participant Nym Client
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end
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participant Entry Gateway
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loop Cover + Real Traffic Stream
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Nym Client->>Nym Client: Check internal queue + delay
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Nym Client->>Entry Gateway: Cover traffic
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alt Packets with App Payload
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App Logic-->>Nym Client: Send(bytes): add to internal queue
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Nym Client->>Nym Client: Check internal queue: bytes to send
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Nym Client->>Nym Client: Encrypt & packetise bytes
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Nym Client->>Entry Gateway: Real Packets
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Nym Client->>Nym Client: Check internal queue: bytes to send
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Nym Client->>Nym Client: Encrypt & packetise bytes
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Nym Client->>Entry Gateway: Real Packets
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Nym Client->>Nym Client: Check internal queue: queue empty
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end
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Nym Client->>Nym Client: Delay
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Nym Client->>Entry Gateway: Cover traffic
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end
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```
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> Since Sphinx packets are indistinguishable to an external observer, the only difference between 'real' and cover traffic is whether the payload is empty or not. This can be only known to the eventual receiver of the packet.
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## What does `send()` do then?
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When passing a message to a client (however you do it, either piping messages from an app to a standalone client or via one of the `send` functions exposed by the SDKs), you are **putting that message into the queue** to be source encrypted and sent in the future, in order to ensure that traffic leaving the client does so in a manner that to an external observer is uniform / does not create any 'burst' or change in traffic timings that could aid traffic analysis.
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## Note on Client Shutdown
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Accidentally dropping a client before your message has been sent is something that is possible and should be avoided (see the [troubleshooting guide](../rust/mixnet/troubleshooting) for more on this) but is easy to avoid simply by remembering to:
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- keep your client process alive, even if you are not expecting a reply to your message
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- (in the case of the SDKs) properly disconnecting your client in order to make sure that the message queue is flushed of Sphinx packets with actual payloads.
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