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Correct me if I'm wrong.

So,

Ethernet technology is being primarily used in LANs. And we use PPP in serial links. To carry IP datagram, we can use either layer 2 technology, such as Ethernet, or we need some layer 2 protocol supporting IP like PPP, if there is no layer 2 technology being used. PPP is a data link layer protocol for two devices connected directly without any device between them according to Wikipedia.

1) Can I use PPP to connect to my router from PC? If no, then why?

2) Why I need PPPoE? Where it is used (in which situations)?

3) So PPP was created only for the situation if there is no layer 2 technology? So we could use PPP.

It will be wonderful if you give me detailed answers and additional informations if I misunderstand something.

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2 Answers 2

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1) Can I use PPP to connect to my router from PC? If no, then why?

That depends. If you have network interfaces in your PC and router that support PPP, then yes.

2) Why I need PPPoE? Where it is used (in which situations)?

PPPoE is needed for a link where the other end is running PPPoE. For example, many ISPs offering xDSL will use PPPoE, so you must use PPPoE to connect.

3) So PPP was created only for the situation if there is no layer 2 technology? So we could use PPP.

That is incorrect. PPP is one data-link protocol. There are many others, such as HDLC, frame relay, ethernet, token ring, ARCNET, FDDI, Wi-Fi, ATM, etc.

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  • So, we can use either PPP or Ethernet depending on our desire or implementation?
    – pedal
    Commented Feb 23, 2020 at 13:09
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    Not really. Ethernet interfaces only run ethernet. PPP is typically run on serial interfaces, although it can be encapsulated inside other data-link protocols if the OS allows it (must be able to set up virtual interfaces and encapsulation), but both ends need to support it (most business-grade routers can, but probably not on the LAN side for consumer-grade routers). For example, the original, and still often used, xDSL standard used PPPoA (PPP over ATM) on the WAN interface. Some ISPs have begun to use PPPoE (PPP over Ethernet).
    – Ron Maupin ♦
    Commented Feb 23, 2020 at 15:03
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The main point of using PPPoE is to have an authenticated session, a concept Ethernet by itself doesn't have. That allows an ISP to concentrate packets from many users in their backhaul network and sort out the sessions later on.

PPPoE is a variant of (serial) PPP, so you can use the exact same authentication scheme for xDSL and serial modem dial-in.

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  • So we use PPPoE when we have Ethernet implementation and we want some features which are provided by PPP (such as authentication)?
    – pedal
    Commented Feb 23, 2020 at 13:12

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