Le 04/10/2019 à 02:39, Ted Lemon a écrit :
(If you got this as a Bcc, it’s because I am hoping you can contribute to the
discussion, but might not be on the mailing list to which I sent the question,
so please answer on-list if you are willing.)
I’ve been involved in some discussions recently where the question has come up:
how good is support for RFC7084 in shipping routers? And what gaps exist in
RFC7084 that could cause problems? And in cases where RFC7084 support either
isn’t present, or isn’t useful because no IPv6 or because ISP is delegating a
/64, what things might work and what things might not, if we want bidirectional
reachability between two separate network links in the home.
So for example, suppose we have "CE Router," which supports RFC7084, including prefix
delegation. And we have "Internal Router" on that network requests a delegation, and
gets a prefix from the CE router. Presumably that prefix is out of a larger prefix that CE Router
got from the ISP. Great so far. Let’s call the network on the southbound interface of Internal
Router “South Network”. Let’s call the network on its northbound interface, which is also the
network on CE router’s southbound interface, “North Network.”
viz:
ISP
|
CE Router
|
North Network
|-------------------------------+--------------+-----------------|
| |
Internal Router +---- Node A
|
South Network
|-----------+-------------------+--------------------------------|
|
Node B ---+
If somebody makes a good solution and easily deployed for the topology
in the above figure, then I am willing to consider it for vehicular
networks as well. In them, the CE Router is a Mobile Router in the car
and the Internal Router is one of many other routers in the car. The
ISP is a cellular network and, potentially, an 802.11-OCB network.
At this time, the furthest we can do is a CE Router that runs DHCPv6-PD
and then forms /64s for the Internal Router, and then some 64share (
draft-shytyi-v6ops-danir-04 with URL to implementation). But it has
inconvenients: it introduces a new class (/56), because it is hardcoded
as much as the exiting class /64 is.
(we tried as much as we could to remove the IPv6 class only to come up
with a new one :-)
Alex
If I want hosts on South Network to communicate with hosts on North Network,
what do I have to do? Should Internal Router publish an RA on its northbound
interface? What is the likelihood of that being filtered by the network? If
packets for South Network are forwarded through CE Router, will it forward them
on to Internal Router, forward them north, or drop them?
Similarly, suppose we have a network where unfortunately PD Isn’t available
internally, but IPv6 is present on the northbound interface of the internal
node and southbound interface of the CE router. Suppose further that Internal
Router allocates itself a ULA prefix and advertises that as reachable and
on-link on its southbound interface, and as reachable but not on-link on its
northbound interface. Will that be blocked at layer 2 by CE Router? I’m
sort of assuming here that the CE router is managing the North Network link,
which is probably WiFi.
Okay, now what if there’s no IPv6 support on CE Router or being provided by CE
router on North Network. Suppose Internal Router allocates a ULA and
allocates two /64s out of the ULA, one of which is advertised as reachable on
its northbound interface and on-link on its southbound interface, and a second
of which is advertised as on-link on its northbound interface and reachable on
its southbound interface.
Fourth possibility: Node A is manually configured with an IPv6 address on a
prefix that Internal router is advertising as reachable on its southbound
interface, but which is not advertised on South Network because of filtering.
Node B has an address on a prefix that Internal Router is advertising as
on-link on its southbound interface. Node A has a static route configured
through Internal Router to the second prefix. Is there any reason to think
that traffic between Node A and Node B will be filtered at layer 2 by CE
Router, assuming that traffic on North Network is all going through CE Router?
The goal here is to have bidirectional reachability between the two nodes on
IPv6 using either a global prefix or a ULA. The concern is that something
could prevent each of these cases from working. What I’m really curious about
is whether people have experience with doing communications of this type using
actual routers that ISPs are shipping. Is this “internal network” scenario
part of acceptance testing for these routers? Is this all a big question mark?
In principle this should all work, unless RA guard is hyperactive in CE
Router. But what about in practice?
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