What is the difference between Ingress and Egress? - Azure

There are two terms that I see often when looking at network traffic in Azure: Ingress and Egress.

But what are they? A quick define: search with google gives the following (not tech related) definitions:

ingress vs egress

In broad terms, ingress implies the action of entering, and egress implies exiting.

Definitions for Networking

In the context of network traffic, the terms have a very similar definition:

  • Egress refers to any traffic that exits an entity, or a network boundary. This may also be referred to as outbound traffic.
  • Ingress refers to traffic that enters the boundary of a network. This may also be referred to as inbound traffic.

Ingress is free, Egress is not.

Fortunately, in Azure, only egress is charged. Ingress is completely free.

There are a number of reasons why Azure might do this, including (but definitely not limited to):

  • It's much easier to migrate customers to Azure when there is no initial ingress charge.
  • Most customer data is egress. Typically, a user will make a small request to a cloud application (e.g., a user ID), and get a large amount of data in response (e.g., all that users information).
  • All major cloud providers have decided not to charge for ingress. Azure would have to follow to remain competitive.