Enable IPv6 by default

[mdavidsaver]

Something I have been testing locally for the past few months. When/if we have an IPv6 link-local address assigned (or just arbitrarily selected), it is straightforward to begin using in much the same way as an IPv4 broadcast address.

In this case I use [ff02::70:7661] as a placeholder. The last 3 bytes will also appear in the ethernet destination address, and picking something otherwise unused facilitates hardware filtering.

I don't have a definite timeline for moving forward with this idea.

@kasemir fyi.

[mdavidsaver]

an IPv6 link-local address assigned

Inputs to the request form https://www.iana.org/form/multicast-ipv6

• Can you use a locally scoped address or a MADCAP (RFC 2730) generated address?
  • Would prefer if our server-less name discover mechanism did not depend on the presence of a MADCAP server. (can't find an implementation...)
• Do you need a permanently allocated address? (Please see RFC 3307 for further information)
  • I am fairly confident that we do.
• Are you able to use Unicast-Prefix-Based IPv6 Multicast Addresses in FF3x::/16 or Embedded-RP Multicast Addresses in FF7x::/16?
• Are you able to use Source-specific Multicast (SSM)?
• In which block are you requesting an assignment?
  • Link-Local Scope (RFC 2375, section 2.2)
• Are you using a link local protocol?
  • In this context, yes. We are looking for a migration path from IPv4 broadcast addressing
• Are you using a global protocol?
  • No. Theoretical global use would rely on other mechanisms for name discovery.
• What is the protocol on the network?
  • PV Access
• If the proposed multicast use is for a new application or protocol for wide distribution, please describe the following:
  • The EPICS toolkit has been around for decades. PVA protocol for ~12 years. A migration from IPv4 -> IPV6 is new.
• What functions are performed by this protocol?
  • SCADA
• How is multicast used by this application?
  • Name/resource discovery
• Have you or your organisation requested globally unique IPv4 or IPv6 multicast addresses before?
  • No
• Will you need the proposed assignment for a defined period or for the foreseeable future?
  • indefinite future
• If your proposed use of the multicast address is described in an Internet-Draft or other specification,
  • No
• What name do you want associated with this multicast address?
  • "pva"
• Provide any additional information not described above that would assist the expert in reviewing your application.