----- Original Message -----
From: "Leo Bicknell" <bicknell@ufp.org>
The Cable Modem is in many ways very similar to a FTTH ONT. It takes one media (cable, fiber), does some processing, provides some security and a test point to the provider, and then hands off ethernet to the customer. A majority of customers then plug in a Home Gateway (router, one of those linksys/netgear/belkin things), although some plug in a single device.
It's actually not. A cablemodem is similar to a DSU, while an ONT is similar to a CSU. Layer 2 vs layer 1. I think.
What goes wrong? Well, the Home Gateway sees a 1000Mbps GigE to the cable modem, and tries to send at that rate. The cable modem is only allowed to transmit to the plant at maybe 10Mbps though, and so it must buffer and drop packets, at what appears to be L2. At which point virtually any ability the customer had to do QoS is gone! I believe some Verizon FIOS customers had similar issues with GigE to the ONT, and then 100Mbps upstream service.
Sure. So you hard-throttle the ETH PHY to whatever speed they're paying for; if it's 50Mbps, then you set it as 100BaseT, not Gig.
Havng the two separate devices significantly degrades the customer experience in many cases, particularly where there is a speed mismatch.
I'm all about not buffering, but this seems baby/bathwater, to me.
I want to chuck the cable modem and/or ONT out the window never to be seen again, and let the customer plug their home gateway in directly. No middle box to buffer or drop packets, or otherwise mangle the data stream in bad ways.
Nothing at their end that you have any hope of being able to manage when they call in with trouble...
I have no issues with the Home Gateway responding to OAM testing from the provider. I have no issues with it learning part of its config (like a maximum transmit speed) from the provider.
A Cable Modem or ONT is a glorified media converter which should not exist.
If by "Home Gateway", you mean CPE, then no; the field is *way* too big to be able to get reliable remote management to work properly, not to mention the combinatorial explosion of multiple ISPs on the back end. Whether you can get by without carrier gear at the customer site is pretty much directly proportional to the complexity of the service. If a T-1 needs it, fiber sure does. Cheers, -- jra -- Jay R. Ashworth Baylink jra@baylink.com Designer The Things I Think RFC 2100 Ashworth & Associates http://baylink.pitas.com 2000 Land Rover DII St Petersburg FL USA #natog +1 727 647 1274