[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Permanent ULA support in home networking (Re: New (-02) version of IPv6 CPE Router draft is available for review)
On Tue, 22 Jul 2008 18:15:04 -0400, Alain Durand
<alain_durand@cable.comcast.com> wrote:
> [Changing the title of this long thread to focus the discussion and
> trimming the distribution list]
>
> We have a trade-off here to make between network stability and
application
> complexity: either modify apps to deal with renumbering (ie try
> reconnecting, avoid well know literal addresses, use some kind of service
> location,...) or to teach application when it is ok to use ULA vs GUA,
> especially in referrals.
Avoiding literal addresses is orthogonal to using ULA. Human beings will
not remember ULA addresses, neither GUA addresses. In both cases, a local
DNS server, or a multicast discovery system will be required. In the mean
time, CPE vendors will continue to document http://192.168.0.1 alike as the
way to configure the (dual-stack) CPE.
Same thing with service location. People will use UPnP, Bonjour, SAP or
whatever. There is actually some value in using ULAs here, as the
applications can easily check that this is "Intranet". With GUAs, it is
do-able but more difficult to tell semi-trusted local peers from untrusted
remote ones.
> My take is that the former is simpler and lead to less service calls.
> The later introduce the notion that apps have to be aware of the
> topology, which I found disturbing.
Most applications do not do referrals. And those that do... they will need
to have some IPv6 logic _anyway_ (e.g. to discard link-local), know
multicast groups, do AAAA lookups, etc.
Most applications will screw up, especially LANish applications (file
shares, printers, ...) if they need to reconnect. In fact, reconnecting is
typically not a complete solution due to protocol limitations. To the
contrary, enumerating addresses properly is an implementation issue that
does not affect protocol design.
Also, it is fairly typical for LAN applications to start doing discovery
right at boot. Precisely when renumbering from ULA to GUA is likely to
occur and break things up.
--
Rémi Denis-Courmont