Forward proxy (client protection).
In this case, a proxy server is implemented between a local area network (LAN) and the Internet. Local terminals can thus be protected from the public network. All outgoing requests are first sent to the proxy server, which receives these requests and forwards them accordingly to the target computer on the Internet with its IP address (proxy IP address) as the sender.
The proxy server thus acts as a proxy and also assumes a control function.
Reverse proxy (server protection)
Web servers can also be protected, for example against denial of service attacks, by implementing a proxy server for accesses from the public network. Clients from the Internet thus have no direct access to the target server. Requests are first received by the proxy, checked and forwarded to the server in the background if they are unobjectionable.
Application Level & Circuit Level
Application Level Proxy:
This type of proxy has certain features that can analyze data packets. Thus, this method is on the seventh layer (application layer) of the OSI model (Open System Interconnection). Therefore, this type of proxy server has the function to block, modify and forward certain data packets according to preconfigured rules. An application-level proxy is also called an application or application filter.
Circuit Level Proxy:
The circuit level proxy operates at the 3-4 layer (switching and transport layer) of the OSI model and is therefore not authorized to analyze packet data. This type of proxy is often used as a firewall filtering module, which allows data packets to be filtered via ports and IP addresses. It cannot influence the communication itself. The filtering is based on the ALL OR NOTHING principle. Data packets are either allowed through or blocked.
Proxy vs VPN
VPNs typically operate at layers 2-3 of the OSI model and redirect all your traffic, while proxy servers operate at layers 3, 4, and 7, depending on their configuration, and only redirect traffic from a specific application or browser. VPNs can be slower than proxy servers because they additionally encrypt the data.