Re: Dialup over Ethernet
Ewen McNeill <nznog-g+LI5CTLdeyVez4R2NBCHqU/[email protected]>
| Newsgroups | gmane.org.operators.nznog |
|---|---|
| Message-ID | <[email protected]> |
On 13/09/17 18:21, Nathan Ward wrote:
> In both EUBA and UFB, Chorus or the LFC inserts a headers in to the
> DHCP or PPPoE messages that convey the Circuit ID and Remote ID.
> Remote ID is the most commonly used for authentication and corresponds
> to a provider reference number (ASID in Chorus world, for example).
DHCP relay with additional parameters defining the origin ONT also seems
like a sensible way to identify back to the premises in question, if
you're doing IP straight over VLAN 10 (etc). That was the sort of "DHCP
extension" I had in mind as an alternative to username/password
authentication in PPPoE.
If PPPoE also has a similar extension at the discovery phase (where the
ONT/fibre provider can inject more identification details) then that too
seems less problematic than requiring the end user to configure
dialup-style PPPoE username/password details (as appears to be required
by my client's customer's ISP). But you do still have the PPPoE
overhead, and state.
> PPPoE’s benefit is LCP keepalives for fast failover. Without them, you
> need a BNG system that either: > a) has low DHCP timers, or;
> b) has BFD /similar and you have CPE that support it, or;
> c) has state syncing with another box
BFD (https://en.wikipedia.org/wiki/Bidirectional_Forwarding_Detection)
seems like another obvious "we should arrange to have CPEs that can do
this" feature if one were building out a network like UFB from scratch.
BFD's overhead is rather less than 8-bytes-per-frame-forever, even at,
eg, one BFD exchange per second. Running PPPoE to get LCP keepalive
seems a fairly heavyweight solution to the "we'd like faster than 5
minutes failover if a ISP core device dies".
Clustering devices for HA ("state syncing with another box") is a fairly
common approach (although not without its own set of edge cases to get
right in the clustering protocol).
Ewen
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