Network Transform

The Network Transform component synchronizes the position, rotation, and scale of networked game objects across the network.
A game object with a Network Transform component must also have a Network Identity component. When you add a Network Transform component to a game object, Mirror also adds a Network Identity component on that game object if it does not already have one.
The (new) NetworkTransform component
By default, Network Transform is server-authoritative unless you check the box for Client Authority. Client Authority applies to player objects as well as non-player objects that have been specifically assigned to a client, but only for this component. With this enabled, position changes are send from the client to the server.
You can use the Send Interval to specify how often it syncs (in seconds).

Smooth Movement during Latency, Packet Loss & Jitter

NetworkTransform sends movement updates every sendInterval over the Unreliable channel.
Network conditions are never ideal, so those updates may come in out of order, delayed or get dropped somewhere on the way.
Smooth movement over non ideal network conditions is one of the more difficult problems in game networking. Our NetworkTransform component solves it by using Snapshot Interpolation. We recommend reading through the linked chapter to understand it in detail.
In short, smooth movement over non ideal conditions is achieved through buffering. The worse the conditions, the higher the Buffer Time Multiplier needs to be. However, the higher it is the longer it buffers too.
The total buffer time is calculated by sendInterval * Buffer Time Multiplier. It's usually recommended to use a factor of '3'.
This means that while you can increase the Buffer Time Multiplier to make up for worse conditions, you could also decrease the sendInterval to still keep a reasonably low buffering delay.
Our new Network Transform is already used in production by several real world game projects. Check out this video for a comparison between our old & new NetworkTransform components.
In order to get the new NetworkTransform component, simply update your Mirror version until it looks like the one from the above picture.
Please keep in mind that NetworkTransform broadcasts every sendInterval. To reduce bandwidth, we are currently working on SyncDirection, Notify & Delta Compression. Those will automatically reduce NetworkTransform bandwidth to a minimum once implemented. In fact, all of Mirror's bandwidth.