Transport Selection

Rewire supports both DDS and Zenoh simultaneously. This guide helps you understand the trade-offs and choose the right transport for your setup.

You don't have to choose one. If your network has nodes on both DDS and Zenoh, Rewire bridges both at the same time without configuration — that is the default.

DDS vs Zenoh

DDS (Data Distribution Service) is the default middleware for ROS 2. Most ROS 2 installations use either CycloneDDS or FastDDS.

When to use DDS:

You're running a standard ROS 2 setup with the default middleware
All nodes are on the same local network or subnet
You need zero configuration — DDS discovery works out of the box on a LAN
You're using CycloneDDS or FastDDS

Considerations:

DDS discovery uses multicast, which may not work across subnets or VPNs without extra configuration
Large-scale deployments (many nodes/topics) can generate significant discovery traffic
Some cloud and container environments block multicast by default

Zenoh is a newer protocol adopted by ROS 2 via rmw_zenoh. It's designed for wide-area networks and resource-constrained environments.

When to use Zenoh:

Your ROS 2 nodes use rmw_zenoh as the middleware
You need to bridge across subnets, VPNs, or cloud environments
You want lower discovery overhead in large-scale deployments
You're running a fleet of robots that need to communicate across networks

Considerations:

Requires rmw_zenoh or zenoh-plugin-ros2dds on the ROS 2 side
Less mature than DDS in the ROS 2 ecosystem

Mixed networks

Rewire discovers topics on both DDS and Zenoh at the same time. If a topic is available on both transports, Rewire subscribes via whichever transport discovered it first.

By default Rewire starts both, which is the right answer for almost every setup: it costs a Zenoh session that finds nothing when there is no router, and it means a node that moves between middlewares needs no change here.

Narrow it with --transport when you know only one is in play:

rewire record --transport dds      # DDS only
rewire record --transport zenoh    # Zenoh only
rewire record --transport all      # both (the default)

{
    transport: "dds",
}

The flag is shared by rewire record, rewire doctor and rewire mappings generate, and a flag always beats the config key.

The case for narrowing is a DDS-only deployment: starting Zenoh there carries a session and a background dial loop against a router that was never meant to exist. Picking zenoh likewise skips DDS discovery traffic on a fleet that has moved to rmw_zenoh. The zenoh section of the config is ignored unless the choice actually runs Zenoh.

Configuration

DDS domain ID

rewire record --domain-id 42

Or set the ROS_DOMAIN_ID environment variable. Default is 0.

Zenoh router

Unset, Rewire dials tcp/localhost:7447, where the rmw_zenoh router listens. If your Zenoh nodes are behind a router elsewhere, pass the endpoint via CLI or config:

rewire record --zenoh-connect tcp/192.168.1.100:7447

{
    zenoh: {
        connect: ["tcp/192.168.1.100:7447"],
    },
}

Set zenoh.multicast_scouting: true to also scout for peers over multicast, on top of dialing the endpoints above. It is off by default because the rmw_zenoh router runs with scouting off too, so turning it on will not find one.

DDS vs Zenoh

Mixed networks

Choosing transports

Configuration

DDS domain ID

Zenoh router

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