[AusNOG] My Predictions for the ISP Industry

[Smith, Mark]

"CPE provides to the LAN hosts either link local (provides is probably the wrong term here), or a ULA or a 2002 based address."

It's not an "or", it's an "and" i.e.

"CPE provides to the LAN hosts link local (provides is probably the wrong term here), and a ULA and a 2002 based address." (although CPE doesn't supply link locals, hosts have them anyway)

One of the key differences between IPv4 and IPv6 is the intentional and designed in support for hosts (or rather interfaces) have multiple active addresses (e.g., one or more link locals, and any mix of ULAs and/or globals). IPv6 source and destination address selection will pick the right one to use e.g. if the destination is a ULA, then the host should use it's (or one of it's) ULA addresses as the source.

RFC3484, "Default Address Selection for Internet Protocol version 6 (IPv6)", is being revised at the moment. Probably the most signficant change is the preference of ULAs over globals - previously, if, for example, multiple AAAAs were returned for a DNS lookup, one a ULA and one 2000::/3, then it wasn't completely clear as to which was to be used in preference. The advantage of this preference is that, for example, in your home, you'll have both ULAs and global addresses on hosts that may need to access the Internet. If you're streaming video from your media NAS to your tablet, the ULA addressing should be used, such that if your ISP has an outage, and your global addresses expire, your video won't be interrupted, because your local ULA addressing is still valid.



-----Original Message-----
From: ausnog-bounces at lists.ausnog.net [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Mattia Rossi
Sent: Friday, 16 March 2012 4:46 PM
To: Mark Andrews
Cc: ausnog at lists.ausnog.net
Subject: Re: [AusNOG] My Predictions for the ISP Industry

On 16/03/2012 16:29, Mark Andrews wrote:
> In message<4F62C921.9090600 at swin.edu.au>, Mattia Rossi writes:
>>>
>>>    >   This means that the
>>>    >   CPE is creating a 6to4 prefix out of it's public facing IPv4 address,
>>>    >   which is then used to distribute v6 addresses to all his IPv6 devices in
>>>    >   the house.
>>>
>>> More or less.  Or some other prefix.  But yes.
>>>
>>
>> Some other prefix? E.g. fc00::/7 ?
>
> You get to play with lots of addrsses and prefixes with IPv6.
>
> en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST>  mtu 1500
>       ether 60:33:4b:01:75:85
>       inet6 fe80::6233:4bff:fe01:7585%en1 prefixlen 64 scopeid 0x5
>       inet 192.168.191.223 netmask 0xffffff00 broadcast 192.168.191.255
>       inet6 fd92:7065:b8e::6233:4bff:fe01:7585 prefixlen 64 autoconf
>       inet6 fd92:7065:b8e::5dfc:57b0:350:c254 prefixlen 64 autoconf temporary
>       inet6 2001:470:1f00:820:6233:4bff:fe01:7585 prefixlen 64 autoconf
>       inet6 2001:470:1f00:820:b12a:d75d:86e6:f3b3 prefixlen 64 autoconf
> temporary
>
> 3 prefixes and 5 addresses.
> fe80::/64 link local
>       fe80::6233:4bff:fe01:7585%en1
>
> fd92:7065:b8e::/64 ULA internal communiction.
>       fd92:7065:b8e::6233:4bff:fe01:7585  mostly servers, long lived
>       fd92:7065:b8e::5dfc:57b0:350:c254   clients, short lived
>
> 2001:470:1f00:820:/64 HE tunneled prefix, external communiction.
>       2001:470:1f00:820:6233:4bff:fe01:7585 mostly servers, long lived
>       2001:470:1f00:820:b12a:d75d:86e6:f3b3 clients, short lived
>

Exactly, that's what I meant: you have either a link local, or a ULA, or in your case a 2001 prefix via the tunnel.

So a 6to4 enabled CPE provides to the LAN hosts either link local (provides is probably the wrong term here), or a ULA or a 2002 based address. It can't get any 2001 or other global unicast prefix one, unless you manually set that up.

Given that ULAs and link locals can't leave the LAN, the hosts need to use the 2002 addresses as source to get out (actually for packets to get back), or the CPE will have to do some weirdness with the other types of addresses (e.g. NAT).

Mat
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