A point-to-point protocol over ethernet (PPPoE) is a network protocol that encapsulates PPP frames inside ethernet frames. It is commonly used in residential and small business broadband connections where the internet service provider (ISP) uses ethernet as the underlying technology.

Explanation:

1. PPPoE Protocol:
- PPPoE is a network protocol that enables the transmission of PPP frames over ethernet networks.
- PPP (Point-to-Point Protocol) is a data link layer protocol used for establishing a direct connection between two network nodes.

2. Ethernet Protocol:
- Ethernet is a widely used local area network (LAN) technology that operates at the data link layer of the OSI model.
- It provides a method for devices to communicate with each other using unique MAC (Media Access Control) addresses.

3. Encapsulation:
- Encapsulation is the process of adding protocol-specific headers and trailers to data packets as they traverse different network layers.
- In the case of PPPoE, PPP frames are encapsulated inside ethernet frames to allow them to be transmitted over ethernet networks.

4. Purpose of PPPoE:
- PPPoE is commonly used by ISPs to provide broadband internet access to residential and small business customers.
- It allows the ISP to establish a virtual point-to-point connection with each customer using PPP, while utilizing the existing ethernet infrastructure.
- By encapsulating PPP frames inside ethernet frames, the ISP can leverage the benefits of PPP, such as authentication and dynamic IP assignment, over an ethernet network.

5. PPPoE Process:
- The PPPoE process involves the following steps:
- The client device initiates a PPPoE session by sending a PPPoE discovery packet.
- The ISP's access concentrator (AC) responds with a PPPoE session ID and other configuration parameters.
- The client and AC exchange PPP control packets to establish the PPP session.
- The client's PPP frames are encapsulated inside ethernet frames and sent over the ethernet network to the AC.
- The AC decapsulates the PPP frames and forwards them to the appropriate destination.

Conclusion:
A point-to-point protocol over ethernet (PPPoE) is a network protocol that encapsulates PPP frames inside ethernet frames. It allows ISPs to provide broadband internet access using PPP over an ethernet infrastructure. By encapsulating PPP frames, the ISP can leverage the benefits of PPP, such as authentication and dynamic IP assignment, while utilizing existing ethernet networks.