If you’re reading this, we may share a common goal of keeping our privacy secure on the Internet. To achieve this there are a variety of methods but they almost all involve proxy servers to some extent.
The proxy server can be found in many guises on the internet and indeed there are many different types but they all face the same challenges in how to handle the different protocols that are used on the internet.
What is the OSI Model?
The OSI (Open Systems Interconnection) model is a conceptual framework used to understand and describe the functions of a network protocol suite. It was developed by the International Organization for Standardization (ISO) in the late 1970s and early 1980s.
The OSI model consists of seven layers, each representing a different aspect of network communication. These layers are:
- Physical Layer: This layer deals with the physical transmission of data over the network medium, such as cables, wires, or wireless signals.
- Data Link Layer: The data link layer is responsible for the reliable transmission of data frames between nodes on a network. It handles error detection and correction and ensures data integrity.
- Network Layer: The network layer handles the addressing, routing, and forwarding of data packets across multiple networks. It determines the best path for data transmission.
- Transport Layer: This layer ensures the reliable delivery of data between end systems. It breaks down larger data segments into smaller packets and manages flow control and error recovery.
- Session Layer: The session layer establishes, manages, and terminates connections between applications on different devices. It provides synchronization and dialog control.
- Presentation Layer: This layer is responsible for data representation and transformation. It translates data into a format that the application layer can understand.
- Application Layer: The application layer is the closest to the end-user and provides network services and interfaces to applications. It enables user interactions and supports protocols like HTTP, FTP, SMTP, etc.
The OSI model serves as a guideline for the development of network protocols and helps in troubleshooting network issues by dividing the complex network communication process into manageable layers.
What layer of the OSI model do Proxy servers Operate?
A proxy server operates at the Application layer of the OSI model and in general they have two ways of handling protocols – they can either be proxied or tunneled.
When we talk about a proxy operating at the Application layer we basically means that the proxy server actually understands what is happening. At this point we can do neat things like filter the protocol, perform logging and operate access control.
If a proxy doesn’t understand a protocol however it will generally just tunnel this information between the client and the server. This relaying happens generally with any protocol that the proxy doesn’t have specific support for it, examples are things like SSL protocols which are normally just tunneled by most proxies (but many don’t support SSL at all) including many of the web based proxies you’ll find on the internet.
Examples of protocols that do operate at the application level and which are truly proxied are things like HTTP, FTP and Gophur!
If you’ve been using the internet for a while you may remember gophur it was a protocol designed for searching for documents, it was pretty popular at one time but I don’t think anyone uses it much now outside maybe a few universities.
Anyway the important thing to remember from a privacy point of view is that ever piece of data you send through your web browser when using a proxy, goes through that proxy server – make sure you know it’s secure and well run !
