On 14/09/17 09:33, Peter Lambrechtsen wrote:
For me the restore time in the event of loss of service to customers is the main reason why PPPoE is superior to DHCP/IPoE.
Thanks for all the details. I do remain puzzled by the use of a stateful protocol (PPPoE) with a timeout (LCP keepalive) leading to better restore time than a mostly stateless approach (eg, VRRP for the gateway address, let CPEs keep using their DHCP lease IP, separate DHCP servers with state, minimal state in customer-facing gateway other than VRRP-master-of-the-second -- which is a common approach in, eg, datacentre networking).
Voice ATA services on the same handover can take up to 30 mins to restore even though the DHCP lease is set down to 5 mins.
Presumably this is until they give up on trying to renew their old lease and get around to asking for a different one. But it's not clear why they need a new IP anyway, at least over a short break like a head end device reboot. If the IP/subnet/gateway stays the same, IIRC most DHCP clients will successfully re-request it from another DHCP server on the same subnet if their original DHCP server goes away.
Another advantage is to find out the customers current sync rate on copper as the vast majority of Chorus EUBA/WVS DLSAMs send you the connect rate information in the PADI
That's definitely an argument for PPPoE on xDSL for legacy reasons; but UFB isn't over copper...
Even in the UFB world I would always expect some sort of router / Customer RGW between the ONT and the customers devices. I wouldn’t expect a customer to plug in a switch into an ONT then have multiple devices sending DHCP requests to the BNG
Nor would I, FWIW, I'd expect there to be some sort of router/CPE/RGW device at the edge. The usual way to handle that in a just-switched-Ethernet world is to put a MAC limit on the port; it seems like an obvious thing that an ONT could enforce (eg, 1 MAC, dynamically learnt, forgotten as soon as ethernet carrier on link to CPE goes away so end user can change CPE at will).
Since unconvinced to see the compelling reason case why IPoE/DHCP is any better than a PPPoE link, as I can only see downsides to IPoE.
Definitely seems to be a religious war :-) Thank you all, I'm much better informed as to why we ISPs are still doing PPPoE in a UFB/metro-ethernet environment. It still doesn't seem like a good tradeoff to me, but at least y'all are getting more than username/password authentication out of it! Ewen