OCI provide various gateways(GWs). Here is a brief summary.
List of various OCI GWs

이름
Purpose
Comment


인터넷 게이트웨이
Access internet from inside the Public Subnet;Access Public Subnet from internet.

NAT 게이트웨이
Access internet from inside the Private Subnet;(One-way traffic, unable to access Private Subnet from outside)

서비스 게이트웨이
Use OCI services such as Object Storage and ADB without going through the Internet.

Local Peering Gateway (LPG)
Connection between VCNs in the same region. (Even if the tenancy is different, VCNs can be connected to each other as long as they are in the same region.)
It is assumed that the CIDR Blocks of the two VCNs do not overlap.

Dynamic Routing Gateway (DRG)
1. Connection between On-P and OCI. (IPSec VPN, FastConnect)2. Connection between VCNs across regions.
It is assumed that the CIDR Block of the connection source and the destination do not overlap.

스토리지 게이트웨이
Data transfer from On-P to OCI Object Storage. (NFSv4 protocol)
Need to install on On-P client, only supports Linux OS.

API 게이트웨이
Provide REST API endpoints of OCI services to the outside.(OCI Services:Functions,OKE,Compute,etc)

인터넷 GW 대 NAT GW 대 서비스 GW

Local Peering Gateway

LPG Scenario-1 (Same Region)

If VCN1 and VCN2 are connected by LPG and VCN2 and VCN3 are connected by LPG too, another pairing is required if you want to communicate between VCN1 and VCN3.
LPG Scenario-2 (Transit Routing)
When connecting from On-P to OCI via IPSec VPN/FastConnect, you can connect to the Spoke VCN via the Hub VCN.

Dynamic Routing Gateway

DRG Scenario-1 (IPSec VPN)

DRG Scenario-2 (FastConnect)
In the case of public virtual circuit, it does NOT go through DRG.

DRG Scenario-3 (Crossing Regions)
You need DRG when you want to configure DR (Failure Recovery) across regions.

DRG Enhancement
There was a big enhancement on DRG released on 2021/05/26,. I listed some of them as following.
The relationship between DRG and VCN was 1:1. Now you can connect a single DRG to multiple VCNs

And, you can connect many VCNs if you attach them to a common DRG. (Up to 300)
If you want create connections between VCN, you may use LPG. But there is a service limit that allows you to create up to 10 LPGs for a single VCN. Now, you can connect more than 10 VCNs by attaching them to a common DRG.

By using Remote Peering Connection, known as RPC, it is possible to connect from On-P to a remote region via OCI backbone.

You can also connect DRGs in different tenancies using Remote Peering Connection.

스토리지 게이트웨이

API 게이트웨이

This blog is about how to call OCI Functions using API Gateway.

Price
--Except API GW, all above GWs are free to use. (Related OCI services and outbound charges are not included.)
--API GW price are calculated based on usage (the amount of API CALL). There is no charge if API GW is unused.

Related Blog
Personal Blogs on Oracle Cloud Infrastructure
OCI 다양한 GW 요약 (Japanese version)
Documentation
Access to Oracle Services: Service Gateway
Storage Gateway FAQ
Oracle API Management
Introducing global connectivity and enhanced cloud networking with the dynamic routing gateway