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Re: I-D Action:draft-ietf-v6ops-ipv6-cpe-router-03.txt
On Sun, 10 Jan 2010, Mark Smith wrote:
routers may be link layer peers. The cost difference between layer 2
forwarding and layer 3 forwarding also encourages minimising the layer
3 resources.
I don't agree AT ALL, rather the opposite. I'd like to see rudimentary L3
switch quite close to the customer instead of these huge L2 clouds people
seem to like. Customers should not be in the same broadcast domain unless
quite a lot of security measures are taken (MAC rewrite etc). Basically
everything the customer can set themselves needs to be controlled in case
of shared L2.
The "security" I am talking about is the BCP38/SAVI kind, not anything
else. Doing that kind of security (defying spoofing, man in the middle,
etc) requires a lot of L2/L3 magic in a big L2 network, I'd rather avoid
that.
"security reasons" is a nice generic term, but it doesn't really
explain anything. What specific "security reasons"? What if an ISP
doesn't want to provide "security", and would rather just be a dumb bit
pipe for their customers?
They still need to do basic BCP38.
I also think it may not be that ISPs haven't wanted their customers to
talk L2 directly with each other, it think it's probably because they
haven't been able to. They've had legacy PPPoE infrastructures which
force hair pinning of traffic between layer 2 adjacent customer, or the
nature of the link layer technology, e.g. cable or ATM, hair pins the
traffic anyway and may not support simple link layer peer-to-peer
traffic exchange, without something like NHRP or setting up switched
virtual circuits.
Read my previous posts, I come from an ETTH background as of 10 years and
there we had shared L2 by means of L2 switches in every basement. When I
designed ADSL I did it with single vlan per customer and L3 switch in each
PoP.
If a generic "complexity" argument is going to be used, then I'd argue
that a prefix-redirect mechanism is much much simpler than PPPoE, PPP or
DHCP. Single packet format, simple processing. It's not really any more
complex that host-redirects and they're not complicated.
I don't see how this easily can be done and still adhere to BCP38. Guess
it would involve a lot more SAVI requirements on the L2 device aggregating
the customers.
--
Mikael Abrahamsson email: swmike@swm.pp.se