PPPoE, the abbreviated form of Point-to-Point Protocol over Ethernet is a proposal which defines the specific manner in which a host personal computer interacts with a broadband-connection modem (wireless, cable, DSL etc.) for achieving continued access to the increasing number of HSDN or High-Speed Data Networks. PPPoE depends on two commonly accepted standards which are PPP (Point-to-Point protocol) and the Ethernet. Its implementation doesn’t require end-users to have a lot of technical knowledge, apart from the basic skills related to connecting to the Internet via a dial-up service.

Furthermore, PPPoE doesn’t require any major changes in the way in which carriers and ISPs (Internet Service Providers) implement or abide by their operational models. Point-to-Point Protocol over Ethernet is highly popular is because of its extremely easy usage, compared to the other approaches. When high-speed Internet access is made easier for the end-consumers, and ISPs and carriers are provided with means of more seamless integrations into their existing infrastructures, the penetrative-ability of PPPoE can significantly improve the adoption levels of the high-speed access services among the common population.

In addition, PPPoE provides extensive advantage to the service providers, by maximizing its integration with and minimizing the disruptions of their already existing dial-up network infrastructures. Getting properly integrated with the pre-existing back-office automation tools developed by the ISPs for their dial-up lines, PPPoE provides for continued cost savings and swift deployment of services. Right from the accounting aspect, secure access and authentication to the configuration management, PPPoE provides support to a wide range of ISPs’ existing services and applications. The base protocol of PPPoE has its definition in the RFC 2516.



Why are Internet service providers and carriers interested in using PPPoE?

As the usage of PPPoE allows carriers and ISPs to use their already existing radius authentication systems of their dial-up services on Internet and broadband-based services, it makes a lot of common sense for them to use it actively in their service delivery. Dial-up is based on point-to-point protocol and majority of broadband connections are based on Ethernet. Therefore, using the Point-to-Point Protocol over Ethernet is the most feasible way of going about things. The protocol also enables the ISPs to resell their existing lines multiple number of times. For instance, their metered services, broadband-based content like movies etc., their rated services and more.

Does PPPoE change the way in which end-user uses high-speed data services?

Rather than the connection getting automatically established when a user boots his/her computer (for instance using DHCP for obtaining IP address), he/she would need to connect using a PPPoE software such as WinPoET, or perhaps a router that handles this process. Once the user is connected to the network using the client, his/her connection will work the same way as his/her already existing connection. However, it must be noted that when the user is finished working, or stays idle for a certain period of time, his/her client software may be reset and disconnect him/her from the Internet, requiring him to reconnect again for gaining re-access to the Internet.

Do the users experience any speed difference if their ISPs switch over to the PPPoE?

Going by the observations made by experts, the implementation of PPPoE may possibly lead to a 5% to 10% decrease in the bandwidth. This is because the extra data is sent to the line for handling of the PPPoE signaling. There could be other penalties too, deriving from the implementation on the server side. However, if you view it from the mathematical perspective, PPPoE causes addition of an extra 8 bytes of header information to the standard 1500 bytes MTU packets. Keeping this in mind, the speed may only get reduced by 0.3%. Hence, you may witness a speed drop, but it may hardly be evident.

Does PPPoE impact the Internet applications like ICQ?

PPPoE protocol has been running fine for over a decade now and all major Internet applications work perfectly well with it.

Is there a chance that PPPoE exposes the broadband users to higher security risks?

On the contrary it’s the other way round! The usage of PPPoE significantly decreases the security risks of broadband connection users. One can have his/her PC setup and running but disconnected from the ISP if he/she chooses to do so via the PPPoE software. The vulnerability levels to Internet attacks are thus reduced significantly owing to such disconnections.

How 3Com changed the PPPoE protocol?

All that 3Com did was that they created their own unique proprietary version of the PPPoE protocol. This protocol is used only when a person uses a 3Com DSL modem that is set to use the PPPoA mode. In this scenario, the DSL modem speaks the PPPoA language with the ISP, but PPPoE with the computer. This is the reason why 3Com bundles a PPPoE client into their DSL modems. The following two values were changed:
The ETHER_TYPE value was changed from the previous 0x8863 to 0x3c12 for the PPPoE Discovery phase
The ETHER_TYPE value was changed from the previous 0x8864 to 0x3c13 for the PPPoE Session phase

How this affected the router usage is that a few routers supported the new version only with the 3Com DSL modems in the PPPoA mode.

The network interface needed by PPPoE

The running of PPPoE applications needs an Ethernet adapter bound to TCP/IP. It could be in any of the following forms: USB DSL modem, USB connected to an Internet adapter or an Ethernet card.

Can PPPoE be configured to connect upon booting-up of a PC?

Majority of the PPPoE applications like WinPoET have a feature that allows for network connection during the Windows start-up phase.

How does PPPoE generate an IP address?

Whenever a user clicks on a PPPoE application for connecting to the Internet, or when his/her router does it on his/her behalf, a discovery process gets initiated for establishment of a connection. Thereafter, a session is created and the user’s user ID and password is authenticated via Radius. This is followed by assignment of DNS, IP address etc. through a process quite similar to IPCP or DHCP.

PPPoE discovery stage in detail

The discovery stage of PPPoE comprises of four different steps: the initiation, the offer, the request and then the session confirmation.

1. PADI Packet: In this step, a PADI (PPPoE Active Discovery Initiation) packet is sent by the PPPoE client to the broadcast address. The population of ‘service-name’ field can also be done by this packet provided it was entered in the dial-up networking properties.

2. PADO Packet: The sent PADI is responded by a PADO (PPPoE Active Discovery Offer) by the Access Concentrator or the PPPoE server if there was a ‘service-name’ provided. If not, the Access Concentrator populates the ‘service-name’ field (in PADO packet) with services it can service. Thereafter, the PPPoE client is sent the PADO packet by the Access Concentrator or PPPoE server.

3. PADR Packet: Upon receiving the PADO packet from the Access Concentrator or PPPoE server, the PPPoE client reverts back with a PADR (PPPoE Active Discovery Request) packet to the former’s unicast address. Even if the client receives multiple PADO packets, it responds only to the first valid PADO packet received. If the earlier PADI packet didn’t have any ‘service-name’ in it, the client now populates the ‘service-name’ field of the PADR packet with the first service-name received (in the PADO packet).

4. PADS Packet: After receiving the PADR, the Access Concentrator or PPPoE server generates a unique session id for that PPP (Point-to-Point Protocol) session, and returns that id via a PADS packet to the PPPoE client at its unicast address.