This document provides an overview of the architecture and design decisions around Ztunnel, the node-proxy component in ambient mode.

## Background and motivation

Motivations to implement ztunnel generally came from two areas.

First, and most importantly, it serves as a means to implement the real goal: waypoints.
For various reasons outside the scope of this document, there is a desire to move from a sidecar based architecture to a "remote proxy" architecture.

  // SideEffects states whether this webhook has side effects.
  // Acceptable values are: None, NoneOnDryRun (webhooks created via v1beta1 may also specify Some or Unknown).
  // Webhooks with side effects MUST implement a reconciliation system, since a request may be
  // rejected by a future step in the admission chain and the side effects therefore need to be undone.

  // SideEffects states whether this webhook has side effects.
  // Acceptable values are: Unknown, None, Some, NoneOnDryRun
  // Webhooks with side effects MUST implement a reconciliation system, since a request may be
  // rejected by a future step in the admission chain and the side effects therefore need to be undone.

// IngressSpec describes the Ingress the user wishes to exist.
message IngressSpec {
  // ingressClassName is the name of the IngressClass cluster resource. The
  // associated IngressClass defines which controller will implement the
  // resource. This replaces the deprecated `kubernetes.io/ingress.class`
  // annotation. For backwards compatibility, when that annotation is set, it
  // must be given precedence over this field. The controller may emit a

#### Caching

// IngressSpec describes the Ingress the user wishes to exist.
message IngressSpec {
  // IngressClassName is the name of the IngressClass cluster resource. The
  // associated IngressClass defines which controller will implement the
  // resource. This replaces the deprecated `kubernetes.io/ingress.class`
  // annotation. For backwards compatibility, when that annotation is set, it
  // must be given precedence over this field. The controller may emit a