3gpp-analysis: DNS over v4 if availablen

[Pekka Savola <pekkas@netcore.fi>]

Hi,

Relating to the previous "Need for UE <-> 3GPP configuration" 
configuration issue (closed now), I'd maybe augment the text:

    DNS server addresses typically also need to be configured in the
    UE. In the case of IPv4 type PDP context, the (IPv4) DNS server
    addresses can be received in the PDP context activation (a control
    plane mechanism). Same kind of mechanism is also available for
    IPv6: so-called Protocol Configuration Options Information Element
    (PCO-IE) specified by the 3GPP [3GPP-24.008]. It is also possible
    to use [DHCPv6-SL] or [RFC3315] and [DHCP-DNS] for receiving DNS
    server addresses. The authors note that the general IPv6 DNS
    discovery problem is being solved by the IETF dnsop Working Group.
    The DNS server addresses can also be received over the air (using
    SMS), or typed in manually in the UE.

.. by adding a sentence at the end:

                                           Note that as long as IPv4
    PDP context is active, DNS lookups can also be done over IPv4
    transport.

.. just to highlight the fact that w/ dual-stack UE deployment, not having
v6 DNS is not necessary a big deal (yet!)

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings