===== Top Down Use Case and Gap Analysis =====

Here are some top down use cases of VIM-agnostic IPv6 functionality, including
infrastructure layer and VNF (VM) layer, and its gap analysis with Neutron
in Juno release:

(1) Use Case / Requirement 1: All topologies work in a multi-tenant environment
Supported in Neutron, Kilo Release: Yes
Notes: The IPv6 design is following the Neutron tenant networks model; dnsmasq
is being used inside DHCP network namespaces, while radvd is being used inside
Neutron routers namespaces to provide full isolation between tenants.
Tenant isolation can be based on VLANs, GRE, or VXLAN encapsulation. In case of
overlays, the transport network (and VTEPs) must be IPv4 based as of today.

(2) Use Case / Requirement 2: IPv6 VM to VM only
Supported in Neutron, Kilo Release: Yes
Notes: It is possible to assign IPv6-only addresses to VMs. Both switching
(within VMs on the same tenant network) as well as east/west routing (between
different networks of the same tenant) are supported. 

(3) Use Case / Requirement 3: IPv6 external L2 VLAN directly attached to a VM
Supported in Neutron, Kilo Release: Yes
Notes: IPv6 provider network model; RA messages from upstream (external) router
are forwarded into the VMs.

(4) Use Case / Requirement 4: IPv6 subnet routed via L3 agent to an external
IPv6 network
(a) Both VLAN and overlay (e.g. GRE, VXLAN) subnet attached to VMs;
(b) Must be able to support multiple L3 agents for a given external network to
support scaling (neutron scheduler to assign vRouters to the L3 agents)
Supported in Neutron, Kilo Release: (a) Yes (b) Yes
Notes: Configuration is enhanced in Kilo to allow easier setup of the upstream
gateway, without the user forced to create an IPv6 subnet for the external network.

(5) Use Case / Requirement 5: Ability for a NIC to support both IPv4 and IPv6
(dual stack) address;
(a) VM with a single interface associated with a network, which is then
associated with two subnets.
(b) VM with two different interfaces associated with two different networks
and two different subnets.
Supported in Neutron, Kilo Release: (a) Yes (b) Yes
Notes: Dual-stack is supported in Neutron with the addition of "Multiple IPv6
Prefixes" Blueprint
(https://blueprints.launchpad.net/neutron/+spec/multiple-ipv6-prefixes)

(6) Use Case / Requirement 6: Support IPv6 Address assignment modes.
(a) SLAAC
(b) DHCPv6 Stateless
(c) DHCPv6 Stateful 
Supported in Neutron, Kilo Release: (a) Yes (b) Yes (c) Yes

(7) Use Case / Requirement 7: Ability to create a port on an IPv6 DHCPv6
Stateful subnet and assign a specific IPv6 address to the port and have it
taken out of the DHCP address pool. 
Supported in Neutron, Kilo Release: Yes

(8) Use Case / Requirement 8: Ability to create a port with fixed_ip for a
SLAAC/DHCPv6-Stateless Subnet. 
Supported in Neutron, Kilo Release: No
Notes: The following patch disables this operation:
https://review.openstack.org/#/c/129144/

(9) Use Case / Requirement 9: Support for private IPv6 to external IPv6
floating IP; Ability to specify floating IPs via Neutron API (REST and CLI)
as well as via Horizon, including combination of IPv6/IPv4 and IPv4/IPv6
floating IPs if implemented. 
Supported in Neutron, Kilo Release: Rejected
Notes: Blueprint proposed in upstream and got rejected. General expectation is
to avoid NAT with IPv6 by assigning GUA to tenant VMs. See
https://review.openstack.org/#/c/139731/ for discussion

(10) Use Case / Requirement 10: Provide IPv6/IPv4 feature parity in support for
pass-through capabilities (e.g., SR-IOV). 
Supported in Neutron, Kilo Release: Roadmap
Notes: The L3 configuration should be transparent for the SR-IOV implementation.
SR-IOV networking support introduced in Juno based on the sriovnicswitch ML2
driver is expected to work with IPv4 and IPv6 enabled VMs.

(11) Use Case / Requirement 11: Additional IPv6 extensions, for example: IPSEC,
IPv6 Anycast, Multicast
Supported in Neutron, Kilo Release: No
Notes: It doesn't appear to be considered yet (lack of clear requirements)

(12) Use Case / Requirement 12: VM access to the meta-data server to obtain
user data, SSH keys, etc. using cloud-init with IPv6 only interfaces. 
Supported in Neutron, Kilo Release: No
Notes: This is currently not supported. Config-drive or dual-stack IPv4/IPv6
can be used as a workaround (so that the IPv4 network is used to obtain
connectivity with the metadata service). See email discussion thread
(http://openstack.10931.n7.nabble.com/Neutron-cloud-init-IPv6-support-td45386.html)

(13) Use Case / Requirement 13: Full support for IPv6 matching (i.e. IPv6,
ICMPv6, TCP, UDP) in security groups. Ability to control and manage all IPv6
security group capabilities via Neutron/Nova API (REST and CLI) as well as via
Horizon.
Supported in Neutron, Kilo Release: Yes

(14) Use Case / Requirement 14: During network/subnet/router create, there
should be an option to allow user to specify the type of address management
they would like. This includes all options including those low priority if
implemented (e.g., toggle on/off router and address prefix advertisements);
It must be supported via Neutron API (REST and CLI) as well as via Horizon.
Supported in Neutron, Kilo Release: Yes
Notes: Two new Subnet attributes were introduced to control IPv6 address
assignment options:
(a) "ipv6-ra-mode" - to determine who sends Router Advertisements, and
(b) "ipv6-address-mode" - to determine how VM obtains IPv6 address, default
gateway, and/or optional information.

(15) Use Case / Requirement 15: Security groups anti-spoofing: Prevent VM from
using a source IPv6/MAC address which is not assigned to the VM.
Supported in Neutron, Kilo Release: Yes

(16) Use Case / Requirement 16: Protect tenant and provider network from rough RAs
Supported in Neutron, Kilo Release: Yes
Notes: When using a tenant network, Neutron is going to automatically handle the
filter rules to allow connectivity of RAs to the VMs only from the Neutron
router port; with provider networks, users are required to specify the LLA of
the upstream router during the subnet creation, or otherwise manually edit the
security-groups rules to allow incoming traffic from this specific address.

(17) Use Case / Requirement 17: Support the ability to assign multiple IPv6
addresses to an interface; both for Neutron router interfaces and VM interfaces.
Supported in Neutron, Kilo Release: Yes

(18) Use Case / Requirement 18: Ability for a VM to support a mix of multiple
IPv4 and IPv6 networks, including multiples of the same type.
Supported in Neutron, Kilo Release: Yes

(19) Use Case / Requirement 19: Support for IPv6 Prefix Delegation.
Supported in Neutron, Kilo Release: Roadmap
Notes: Planned for Liberty

(20) Use Case / Requirement 20: Distributed Virtual Routing (DVR) support for IPv6
Supported in Neutron, Kilo Release: No
Notes: Blueprint proposed upstream, pending discussion. 

(21) Use Case / Requirement 21: IPv6 First-Hop Security, IPv6 ND spoofing.
Supported in Neutron, Kilo Release: Roadmap
Notes: Blueprint proposed upstream. Some patches are under review.