Follow Data Through an Internetwork

Follow Data Through an Internetwork
The figure on the next page presents a simple data transfer between two hosts across an internetwork. We highlight the function of each layer during the communication. For this example we will depict an HTTP request between a client and a server.

To focus on the data transfer process, we are omitting many elements that may occur in a real transaction. In each step we are only bringing attention to the major elements. Many parts of the headers are ignored, for example.

We are assuming that all routing tables are converged and ARP tables are complete. Additionally, we are assuming that a TCP session is already established between the client and server. We will also assume that the DNS lookup for the WWW server is already cached at the client.

In the WAN connection between the two routers, we are assuming that PPP has already established a physical circuit and has established a PPP session.

On the next page, you can step through this communication. We encourage you to read each explanation carefully and study the operation of the layers for each device.

Follow Data Through an Internetwork
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