 |
 |
 |
 |
|
 |
|
 |
|
 |
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
Hello, In my Humble
opinion this document is very interesting, for at least 6 reasons: 1/The mechanism "CPE
mode " described in chapter 3 allows an IPv4 only host running IPv4 only
applications behind an "upgraded IPv4 CPE" to initiate a communication
with an IPv6 only server using a well-known port and moreover, the server can also
add a second session with this host (for example to add a media flow). I have not seen any
other solution able to do that, but, may be, I have missed them (For example in
A+P solution an IPv4 only host can initiate a communication with the IPv6 only
host, with a shared IPv4, but only using a port in the port range). This is possible
because a virtual IPv6 address is allocated to the local IPv4 host behind the
IPv4 CPE. This IPv6 address is made of 3 parts : the IPv6 prefix of the IPv6/IPv4 gateway, the Public IPv4 of the CPE , and the private address of
the CPE. So, as in normal IPv6
network, this virtual IPv6 address is identifying the host behind the CPE ( not as in
an IPv4 network where the host
behind the CPE is just identified by a port and the IPv4 address of the CPE). 2/ To achieve that it is needed to includes 2 IPv4 addresses in
the virtual IPv6 address. This could also be
achieved with "6 to 4"+ISATAP technology. But the problem comes from
"6 to 4". This format uses a well-known prefix. But with a well-known
prefix, IPv4 routes are incorporated in IPv6 routers. As, with IPv4 address
depletion, IPv4 addresses allocation policy will more and more driven by IPv4
addresses saving considerations than routing optimization considerations, the
number of IPv4 routes (the IPv4 entropy) will grow and it is important to avoid
to introduce this entropy into IPv6 networks. So this solution
needs an "ISATAP like" format with 2 IPv4 addresses. Such format does
not exist and this is the reason why this document proposes a new format like a
"6 to 4"+ISATAP but with a local prefix instead of the well-known
"6 to 4" prefix. 3/ In this document it is mentioned that the CPE must be upgraded
toward dual-stack. This condition is sufficient but not necessary. In fact if you look
carefully, it just needs IPv4 in IPv6 translation, IPv6 in IPv4 encapsulation
and address modification in DNS answer. All theses processes can be done by simple
header manipulations. This can be done by a simple IPv4 network driver (No IPv6
routing or router advertisement or DHCPv6 …). 4/ Concerning the Dual-stack Mode, the condition that the host
is upgraded toward dual stack is also sufficient, but not necessary. In fact it
can also be done by a simple network driver as for the CPE. So not only IPv6
applications can uses this technology but also IPv4 only applications. 5/ The proposed format is consistent with the IVI format, so it
is easy to uses the same gateways for both cases. 6/ More, this
format can be extended so that a common architecture with only 2 kinds of function: the IPv4/IPv6 gateway the NAT function (this
function receives IPv6 packet and return IPv6 packets) This common architecture
can then be used for : IVI-T IVI IPv4/IPv6 translator DS-LITE A+P So it is possible
to build a common proposal to solve all different cases. But this is another
story and I am ready to discuss with the authors of the IVI-T proposal to prepare
a common draft. Eric BURGEY France-Telecom/Orange
Lab From:
Dave Thaler [mailto:dthaler at microsoft.com] I read this document and must admit I
didn’t understand it. L What I understood is that it seems to basically
say you can combine translation + encapsulation in the same
box, which is what I believe the Dual-Stack Lite etc folks
already say. Attached is a marked up copy with my comments
(mostly illustrating my confusion). -Dave |