Summary
Highlights
Communication involves a source, a destination, and a channel. Data is converted into a signal, transmitted, received, and converted back into a message. Rules are essential for effective communication, including identifying sender/receiver, common language, correct grammar, speed, timing, and confirmation. Computer protocols must agree on message encoding, formatting, encapsulation, size, timing, and delivery.
Message encoding involves converting data into binary (ones and zeros) and then into a signal suitable for the medium (e.g., electrical voltages for copper wire, light waves for fiber optics). The receiver decodes the signal back into the original message. Message formatting and encapsulation involve placing data into packets, adding source and destination addresses (like zip codes), which routers use to direct data, similar to how post offices use zip codes.
Message size is crucial; large messages must be broken down into smaller, manageable pieces. Timing controls data flow, response time, and access methods to avoid collisions when multiple devices try to transmit simultaneously. Message delivery can be unicast (one-to-one), multicast (one-to-many in a specific group), or broadcast (one-to-all).
Protocols are standards devices adhere to for communication, covering networking, security (encryption and authentication), routing (finding optimal paths), and service discovery. Specific network protocols handle addressing (e.g., IPv4, IPv6), reliability (guaranteeing delivery), flow control (managing data transmission speed), sequencing (reordering fragmented data), error detection, and application interfaces.
Protocols interact in layers. For example, HTTP data is given to TCP for guaranteed delivery, then to IP for routing, and finally to the Ethernet NIC for transmission. The TCP/IP model, developed by ARPA in the 1970s, uses a four-layer structure (application, transport, internet, network access) to simulate postal service operations, using IP addresses as zip codes, routers as post offices, and switches as mail persons. Every piece of data goes through these layers within the computer before being sent over the network.