PPP over Ethernet (PPPoE)
PPP over Ethernet is a protocol for connecting remote hosts to the Internet over an ADSL connection by simulating a dial-up connection.
- Dynamic IP.
Dynamic IP : Select this option if your ISP (Internet Service Provider) provides you an IP address automatically. Cable modem providers typically use dynamic assignment of IP Address.
PPP over ATM (PPPoA)
PPP over ATM is a protocol for connecting remote hosts to the Internet over an ADSL connection by simulating an ATM connection.”
- Fixed IP
PPPoA is slightly faster than PPPoE, and I havn’t had any problems using PPPoA… So if your router/modem supports it, use it. Also note that some ISPs only support PPPoE, and if you have troubles using PPPoA you can always switch back to PPPoE it’s as simple as that
All ADSL lines use ‘ATM’ as the encapsulation between your modem and the exchange. The ATM protocol chops all data into 48 byte chunks called ‘cells’. To send an Ethernet packet over ATM, you need to chop the Ethernet frame into a string of up to 32 cells. If you send a PPP frame over ATM, the Ethernet framing is removed and only the PPP is sent but it still ends up being 32 cells max per frame.
PPPoE overheads are a little more than PPPoA. I think that the PPPoE requires about 20 - 30 bytes or so more. Because ATM cells are fixed lengths, the difference between PPPoE and PPPoA only matters if the frame that is being sent plus the overhead requires one more cell. For example, if the PPPoA frame is 720 bytes long, it can be sent in 15 cells. But the PPPoE frame would require 16 cells because the extra overhead wouldn’t fit into 15.
The PPPoE method ends up requiring perhaps 1-2% extra overhead. If you think you might notice this, change to PPPoA. But unless you peg your line to 100% utilisation for long periods, you really won’t notice any difference. The extra PPPoE overhead will just fill up the cells that were empty anyway.
