Part $1$: Layering and the Internet Model

Imagine that Creamy Ice is a large manufacturer of tasty ice cream and other frozen dessert products and has been in business for decades. Further imagine that the organization$$s manufacturing equipment, and related computers and devices, use a legacy networking model with legacy protocols, rather than the suite of protocols popular today.

The legacy model consists of four layers, and each layer on the sender communicates with that same layer on the receiver. On the sending device, the top layer is named the Codes Layer, and sends control codes, status codes, and associated small data items from the device$$s software. The control codes represent the issuance of a command or instruction for the intended device, while the status codes represent a notification about what is going on with a particular function on the device. Going downwards, the next layer is named the Formatting Layer, and arranges the codes and data into protocol data units $($PDUs$).$ The next layer downwards is named the Distribution Layer, and one function it performs is compressing the PDUs so that they use less bandwidth. Another function is that it distributes the PDUs to nearby equipment, devices, or computers, within the same building or campus. The bottommost layer is named the Encoding Layer and encodes the PDU into electrical signals and transmits the signals over shielded twisted pair $($STP$)$ Type $1$ cable that connects all of the equipment, computers, and devices together.

The receiving device more or less performs the same functions in reverse. The Encoding Layer decodes the electrical signal into bits, then propagates the PDUs to the Distribution Layer. The Distribution Layer decompresses the PDUs and determines whether each PDU is meant for the local device, or for another one. If the PDU is intended for the local device, the layer will then propagate it upwards to the Formatting Layer. The Formatting Layer extracts the codes and data from the PDUs, putting them back into their raw form, and these are propagated to the Codes Layer. The Codes Layer simply gives the codes and data to the device software so it can take appropriate action. If the Distribution Layer initially determines that the PDU is intended for a device other than the local device, the layer will forward the PDU to the other device rather than propagating it to the Formatting Layer.

This legacy model is summarized below.

Sender Receiver

Codes Layer Sends control codes, status codes, and small chunks of associated data Codes Layer Gives the codes and data to the device software

Formatting Layer Formats the codes and data as standardized protocol data units $($PDUs$)$ Formatting Layer Extracts the codes and data from the PDUs and propagates them to the Codes Layer

Distribution Layer Compresses the PDUs, then distributes them to nearby equipment, computers, or devices Distribution Layer

Decompresses the PDUs, then checks whether the PDUs are intended for this device. If so$,$ it propagates the PDUs to the Formatting Layer. If not, it forwards the PDUs to the next nearby device.

Encoding Layer Encodes the PDUs in electrical signals and transmits them over STP Type $1$ cable $$ Encoding Layer Receives the electrical signals, decodes them extracting the PDUs, and propagates the PDUs to the Distribution Layer

With this scenario in mind, address each topic below.

Topic $1$: Layer Comparison

Compare and contrast the four layers of Creamy Ice$$s legacy network model with the five layers of the Internet model in use today. Focus on the significant aspects of the layers in both models, and make sure to cover all five layers of the Internet model in your answer.

Topic $2$: The Benefits of Changing Models

Identify and describe several significant benefits for Creamy Ice if the organization were to change to using the Internet model.

Topic $3$: The Disadvantages of Changing Models

Identify and describe significant disadvantages for Creamy Ice if the organization were to change to using the Internet model.