Dear all,
Please find below some comments about this I-D.
(1)
* Precise in the introduction section the type of networks which are concerned
with the IPv6 deployment models listed in the I-D; in particular mention that
both corporate networks and providers networks are concerned.
* Fixed and mobile networks may adopt distinct IPv6 deployment strategies
because of the differences between the two networks (e.g., controlled CPE vs.
non controlled handsets).
* It seems services infrastructures (e.g., VoIP, IP TV) are out of scope. This
should be mentioned. Note that some service-related discussed is covered in
Section 4.4.
(2)
Page 5/6, the I-D says:
" o The ability to offer a valuable service. In the case of the
Internet, connectivity has been this service.
o The ability to deploy the solution in an incremental fashion.
o Simplicity. This has been a key factor in making it possible for
all types of devices to support the Internet protocols.
o Openly available implementations. These make it easier for
researchers, start-ups and others to build on or improve existing
components.
o The ability to scale. The IPv4 Internet grew far larger than its
original designers had anticipated, and scaling limits only became
apparent 20-30 years later.
o The design supports robust interoperability rather than mere
correctness. This is important in order to ensure that the
solution works in different circumstances and in an imperfectly
controlled world."
and in Page 6: "These factors are also important when choosing IPv6 migration
tools.", but:
* The I-D does not show how these factors are applied for the tools listed in
the I-D; a table with a set of criteria would be useful;
* The first criterion is IMHO meaningless for IPv6 deployment because IPv6 does
not offer a new service compared to IPv4.
* I'm not sure that having an open source for a given tool can be an argument
to RECOMMEND or NOT a given tool;
* How "scalability" is defined (5th bullet)?? All the solutions listed in the
I-D need a NAT (l2-nat, ds-lite nat44, nat44, nat64), to what extent a CGN is
considered as a scalable solution?
* The last bullet is not clear: Do you consider that DS-Lite satisfies this
factor? FWIW, DS-Lite has been rejected by the 3GPP because it requires
specific functions on the UE.
(3)
From the perspective of transitioning networks to IPv6, I don't see the
rationale behind including techniques such as those listed in "4.2. Crossing
IPv4 Islands" as a candidate solutions for IPv6 deployment. This section can
be removed to an appendix.
(4)
(a) I have an issue with the following statements in the I-D:
On page 6, the ID states: "The third scenario is more advanced and looks at a
service provider network that runs only on IPv6 but which is still capable of
providing both IPv6 and IPv4 services."
and in page 11, the ID mentions:
" The recommended tool for this model is Dual Stack Lite
[I-D.ietf-softwire-dual-stack-lite<http://tools.ietf.org/html/draft-arkko-ipv6-transition-guidelines-13#ref-I-D.ietf-softwire-dual-stack-lite>].
Dual Stack Lite provides both
relief for IPv4 address shortage and makes forward progress on IPv6
deployment, by moving service provider networks and IPv4 traffic over
IPv6. Given this IPv6 connectivity, as a side-effect it becomes easy
to provide IPv6 connectivity all the way to the end users."
Taking into account the current DS-Lite specification, this recommendation is
not justified for the following reasons:
* For Ds-Lite technique to be deployed in a IPv6-only realm, and as currently
specified in DS-Lite specification, this would mean that DS-Lite AFTR(s) are to
be located at the boundaries of the IPv6-only domain.
* This design choice would lead to non optimal intra-domain paths to place
communications between two DS-Lite serviced customers.
* This centralised model is not suitable for service providers who want to
deploy DS-Lite AFTRs closer to the customers.
(b) The I-D states in page 11: "Given this IPv6 connectivity, as a side-effect
it becomes easy to provide IPv6 connectivity all the way to the end users."
This wording is not accurate; IPv6 connectivity is not a side-effect of DS-lite
but rather a pre-requisite for DS-Lite (e.g., DHCPv6 is required to configure
for instance the AFTR NAME option, dual-stack CPE, etc.).
(5)
* In Section "4.4. IPv6-only Deployment", add a sentence to precise that the
issues listed in
[I-D.ietf-intarea-shared-addressing-issues<http://tools.ietf.org/html/draft-arkko-ipv6-transition-guidelines-13#ref-I-D.ietf-intarea-shared-addressing-issues>]
are still valid when NAT64 is deployed.
* Page 13, change "SIP (Session Identity Protocol)" to "SIP (Session Initiation
Protocol)";
* Page 13: "One might position a web proxy, a
mail server, or a SIP (Session Identity Protocol) back-to-back user
agent across the boundary between IPv4 and IPv6 domains, so that the
application terminates IPv4 sessions on one side and IPv6 sessions on
the other. Doing this preserves the end-to-end nature of
communications between gateways. For obvious reasons, this solution
is preferable to the implementation of Application Layer Gateways in
network layer translators.
"
(a) Why only listing the back-to-back user agent option (this option is valid)?
Why not deploying means for NAT traversal is not listed as an alternative?
(b) "Doing this preserves the end-to-end nature of communications between
gateways": Which gateways?
(c) For the SIP case, still there is a need for a translator for media flows;
(d) Service-related discussions are not elaborated in other sections: I would
prefer to have a similar discussion for the DS model, in particular issues in
SIP environments to signal both IPv4 and IPv6 addresses in the SDP offers;
means to prioritise the use of IPv6; how the SIP Proxy Server can determine
whether there is a need to invoke a SIP ALG/NAT64/NAT46 (e.g.., translator
should be avoided when a DS UA calls a IPvx-only/DS UA. ALG/NAT46/NAT64 should
be invoked only for IPvx-IPvy sessions), etc.
* Add a reference to
http://tools.ietf.org/html/draft-ietf-v6ops-v6-in-mobile-networks-02
(6)
It would be valuable if the I-D describes some migration paths and examples
about the use of the tools listed in the I-D; e.g.,:
* How DS-Lite CGN devices can be removed from the network since it is supposed
to be a transition solution. This would be a good example to apply what is
stated in the I-D in page 5: "The end goal is network-wide native IPv6
deployment, resulting in the
obsolescence of transitional mechanisms based on encapsulation,
tunnels, or translation, and also resulting in the obsolescence of
IPv4."
* How to encourage the use of native IPv6 transfer capabilities: address
selection issues, application considerations, etc.
Cheers,
Med
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