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Table of Contents
OSI Model -- Quick Overview
The Open Systems Interconnect (OSI) model is a framework that describes how two or more computer systems communicate over a network. Each layer of the framework provides a specific purpose in communications. The OSI framework is as follows:
- Layer 7 - Application
- Layer 6 - Presentation
- Layer 5 - Session
- Layer 4 - Transport
- Layer 3 - Network
- Layer 2 - Data Link
- Layer 1 - Physical
Depending on the type of transport being used, MOSH transmits at different layers of the OSI model. It is important to know that in all cases, MOSH implements its own framework of security.
Encapsulation
Another key concept in network communications is that of encapsulation. Simply put, encapsulation is the process of wrapping existing data in new data. In OSI (and TCP/IP), data at higher layers is encapsulated by data at lower layers. Consequently, MOSH messages are encapsulated, or wrapped, by other lower-level protocols used by transports.
Depending on the transport being used, MOSH may rely on the functionality of these existing protocols for things like reliable message delivery. For example, TCP (used in IP networks) ensures messages sent by one node are received by the destination node. In this scenario, MOSH doesn't need to perform that function since it's included it the transport.
MOSH Transports
A MOSH transport is the radio (or serial connection) where MOSH transmits and receives MOSH messages. The MOSH transport library currently provides support for the following protocols:
- Espressif ESP-NOW(V1)
- Espressif ESP-NOW(V2)
- WiFi
- Serial