
AWS Certified Advanced Networking – Specialty (ANS-C01) Certification Guide
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When looking at the example of encapsulation and decapsulation in the previous chapter, the fundamental principles of communication using direct connectivity seem evident. The system initiating the communication encapsulates the data and puts the bits on the wire, and then the receiving system decapsulates what has been sent. But how does this function when the two end systems are not directly connected? How does this information get sent across a network that exists between the two? The process of sending data between networks is called routing, and it is used to perform packet forwarding.
As covered earlier, the data unit that represents the encapsulated data at layer 3 is called a packet. Network devices that receive packets from end hosts and forward them along to their destination are referred to as routers. Routers forward data in the following way: