[Wiltshire] Any ISP recommendations please? -> IPv4--IPv6

[Simon Iremonger]

> Everybody here probably has more technical knowledge than most so I
> appreciate that Zen has already allocated me a static IP address and
> will also be able to switch on IPv6 for me, perhaps after I've done a
> little reading! They have also sent the ID and passcode that I need to


Given what else you've said, I would basically turn on IPv6 straight
away and have it in practice.  Here are the main basics you can
know about IPv4->IPv6 differences.


IPv6 works in addition to IPv4, generally seamlessly in parallel
and generally automatically preferred when available.


The closest thing to DHCPv4 is Router-Advertisements and stateless
address assignments either with mac-address or 'random' privacy
addresses added-on.

There *is* such a thing as DHCPv6 (used for subnet allocation) and
also DHCPv6 stateful-assignment (which can then act a bit like
DHCPv4) but on a lan, this still requires the router-advertisements.
Alas Android does not support DHCPv6 stateful assignment.

NB: The automatic address assignments only work on 'normal'
/64 subnets, although you can 'manually configure' smaller blocks
in special cases.

Also, you need to know that ARP is replaced with NDP and that there
are these special 'link local' IPv6 addresses fe80:: range which
you generally don't have to play with and are annoying to use because
they have to have special syntax to specify address *and* interface.
The NDP (Neighbour discovery protocol) works with actual ICMPv6
packets sent using the fe80:: addresses, or so.


When IPv6 is auto-configured, the ''gateway'' address is usually
using the link-local (fe80::) address instead of a global address.

Whereas, when you are statically (manually) configuring IPv6
global addresses, you usually set the gateway using a global
address (usually subnet with ::1 on the end), which is the
convention OpenWRT uses, alas some consumer-routers do not
all do this,  which can then be annoying if you are swapping
between main and backup router, etc...


Furthermore, there is not normally a need for 'private' addresses
and not normally a need for NAT.  Instead, if/when your global
address-range changes your hosts just pick up new global addresses
to match the connection.
Your wan-gateway can still be 'firewalling' and provide the stateful
firewall aspect without requiring NAT. (controversy: NAT=security).


You *can* have Unique Local addresses in the fc00::/7 range if you
want something akin to private addresses, in addition to the global
addresses, but if you have static IPv6 global addresses there is
no need, you can use those for your ''internal addressing'' if not
otherwise using IPv4 for that.

Also, there is no such thing as 'fragmented packets'.

The addresses are written in hexadecimal and :: can replace any
group of 0's *once* in the address to shortern it.  You need
extra [] round IPv6 address to use it as a literal in a web
browser address-bar. e.g. http://[2001:db8::51bb:8181]/page etc


Other than those differences mostly about address config and
normally lac of nat, lac of private addresses as-normal, IPv6
works very much like IPv4, TCP/UDP/ICMPv6 works on top very
similarly to TCP/UDP/ICMPv4 do on IPv4, etc.

The "ip" tool (from iproute2 package etc) is best used over
old "ifconfig" "route" etc linux commands --
"ip -6 addr" "ip -6 ro" etc show ipv6 address and route etc...


In DNS, AAAA pointers are used in addition to A pointers to point
at the IPv6 address of a target computer name.  I.e. a host can
have 1 or the other or both.  If your computer has a route to
the target host, the AAAA (ipv6) connection is usually used in
preference to ipv4, except if you are using one of the 2nd-class
ipv6 transition technologies (6to4, teredo, ...) which you won't
need to get into here anyhow.

Reverse-DNS names do exist much the same, but reverse-DNS is rather
less common and very often not present for 'client' computers,
much more so for 'static' server addresses and critical for
directly sending your own outgoing email etc.


> For my needs I think Zen should be perfectly adequate for now as I am
> happy to, for example, continue to use the 1&1 secure SMTP servers to
> relay my outgoing email. I basically want something that all "Just

If you are relaying outgoing mail like that, then exact IPv6 address
allocation and reverse DNS need not matter, and as such, I really
would just 'get' IPv6 from the get-go.  Your IPv4-only incoming port
forwarding should still work once configured on router, etc... and
you can experience the IPv6 straight away by normal autoconfig.


>> They use the term ‘copper pair’ a lot.  I've come to understand they
>> mean the pair of copper wires, ‘tip and ring’, which run from BT's
>> cabinet to the master socket to implement a phone line.  They don't
>> call it a phone line because there may not be a phone on it.

Yes, exactly.


> My girlfriend who has an ADSL router from BT tells me that they appear
> to have stopped using her copper phone line for voice and sent out a
> couple of adapters to somehow connect her previously landline phone via
> the router. This might be what you refer to above. I will be interested

Yes, a farce of "digital voice", eurgh!.  Lots of BT horror-stories
there.  The point is they want to stop paying for legacy-maintenance
of 1980s system-X/Y exchange kit, basically.


I would encourage in any case setting up Signal-app and linking to
Signal-Desktop for linux, and looking into "Matrix", non-facebook
free-open-source things that can do useful voip/messaging
irrespective of "phone calls" although the former does need *a*
phone number (even geographic) that can recieve SMS, purely as an
"identity" to set it up with.  Signal is easy for those with
smartphones and is where the whatsapp developers basically moved
to when taken over by facebook .....   Matrix is less mature but
popular in FOSS circles and growing.


> Openreach are supposed to be coming on Thursday to pull fibre through
> the conduit under the road so this time next week I might be using Zen.

Oh good!.


> Dave

--Simon