Computer Science – 14.1 Protocols | e-Consult

A protocol stack structures network communication into a series of layers, each responsible for a specific set of functions. This layered approach offers significant benefits in terms of modularity, flexibility, and ease of development. Modularity means that each layer can be developed and modified independently without affecting other layers, as long as the interfaces between layers remain consistent. Flexibility arises because different implementations of a protocol can be used at a given layer, as long as they adhere to the defined interface. Ease of development is enhanced as complex communication tasks are broken down into smaller, manageable components.

A typical protocol stack, such as the TCP/IP model, consists of layers like the Application, Transport, Network, Data Link, and Physical layers. The Application layer (e.g., HTTP, SMTP) provides the interface for user applications. The Transport layer (e.g., TCP, UDP) handles reliable or unreliable data transmission. The Network layer (e.g., IP) is responsible for logical addressing and routing. The Data Link layer (e.g., Ethernet) handles physical addressing and error detection. Finally, the Physical layer deals with the actual transmission of bits over the physical medium.

For example, when sending a web request, the Application layer (HTTP) formats the request. This is passed down to the Transport layer (TCP), which segments the data, adds port numbers, and establishes a connection. The Network layer (IP) adds source and destination IP addresses and routes the packet. The Data Link layer encapsulates the IP packet into a frame for transmission over the physical network. The Physical layer then transmits the bits.