Juliusz Chroboczek <j...@pps.univ-paris-diderot.fr> wrote:
>> slowly I've gotten to understand the numerous layer-2 and layer-3
>> savings by not having to have the whole DHCPv4 relay and broadcast
>> processing occuring.
> Could you please explain that? Perhaps with some examples, or even
> actual empirical data?
I'm not a large scale residential ISP, and I've never played one on TV, but
I've operated niche ISPs since 1991, and recently installed a few medium
sized business oriented DSL, Fiber and GPONs. GPONs are odd.
I refer you to the sunset4 mailing list archives, but let me see what I recall.
1) Let's start with PPPoE/DSL
No DHCPv4 server for IPv4, it's all done in PPP.
So you'd have to have a DHCP server somehow, or a new PPP option.
2) Cable/FTTH using ethernet-type things.
You need code (silicon actually, at FTTH speeds) to police DHCP traffic
coming from each customer to make sure that they aren't running a rogue
DHCPv4 server.
That's something you can get rid of if you aren't running v4.
You need to have DHCPv4 relay agents in each of your cable head ends,
and they need to add option-82 to indicate where things are coming from.
You'd like to turn off layer-2 broadcasts (ff:ff:ff:ff:ff:ff) because
there is just a huge amount of noise coming from the customer machines,
but you can't just do that because the DHCPv4 uses that, and you've
got multiple layers of fiber backhauled cable modem.
There is a significant ARP load on the network from every single box
where 0.0.0.0/0->"eth0" because the network isn't configured yet.
(Every single directly connected windows box does this, and some distros
of Linux do this. I was surprised to learn it's allowed...)
The broadcasts have actually forced you to subnet your IPv4 down into
rather small pieces to contain it, and this has lead to uneven
provisioning of IPv4 address space, and you've effectively run out.
(Also see the history behind ARIN
https://www.arin.net/policy/proposals/2012_7.html and
http://www.crtc.gc.ca/eng/archive/2012/2012-96.htm might also be relevant)
If you could turn off broadcasts, you could forward just the multicast you
need (DHCPv6, RA..) which would significantly help reduce the MAC address
load on much layer-2 equipment. Moreso, it's pretty much all P2MP
traffic, so perhaps a much simpler layer-2 forwarding system could be
used. (I don't have such a thing; legacy layer-3 assumptions wouldn't let
anyone create such a thing yet)
And again: if it's too hard, don't implement it (certainly not in open
source, for free), thousands of devices will never get updated to have it
anyway.
--
Michael Richardson <mcr+i...@sandelman.ca>, Sandelman Software Works
-= IPv6 IoT consulting =-
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