Networking protocol stacks Computers on a network communicate in agreed ways called protocols. Protocols dictate which signals computers use across cables, how they tell one another that they have received information, and how they exchange information. These terms reflect the fact that the communications functions are complex and are usually divided into independent layers or levels. A stack is a collection of protocol layers that implement network communication. The protocol associated with each layer communicates only with the layers immediately above and below it, and assumes the support of underlying layers.
Lower layers are closer to the hardware and higher layers are closer to the user.
Although these packages are not protocol stacks, they are discussed here because they provide low-cost alternatives to LANs based on specialized hardware and software.