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ietf-wg-snac / draft-ietf-snac-simple

Automatically Connecting Stub Networks to Unmanaged Infrastructure
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Clarify how stub router and home gateway can be combined in one device #61

Open EskoDijk opened 1 month ago

EskoDijk commented 1 month ago

Section 2 glossary defines:

the term "stub router" refers specifically to its role in providing connectivity to a stub network. For example, a Home Gateway may provide connectivity between a provider network (WAN) and a home network (LAN), while at the same time providing connectivity between the LAN and a stub network.

But the requirements for the stub router in the rest of the document become unclear for this "integrated Home Gateway" case.

For example the definition currently would allow these implementation methods for the router device that combines the 2 separate functions/roles:

  1. A sent RA (unicast or multicast) always includes both PIO + RIO (aka the complete information) – with “stub router flag” set.
  2. The stub router function sends RA with RIO with stub router flag set, and the home gateway function sends separate RA with PIO, using 2 separate link-local source addresses (acting as if 2 routers).
  3. The stub router function sends RA with RIO with stub router flag set, and the home gateway function sends separate RA with PIO, using a single link-local source address. This uses the feature of ND RA that it can be communicated “in parts”. See RFC 4861 6.3.4.

It looks like the draft intends option 1, however, that's currently hard to enforce because the requirements of the draft are only for the "stub router function" not requirements on the entire integrated router device.

Option 3 looks problematic for various reasons - e.g. if a host sends RS, the device has to answer with 2 unicast RAs from the same IPv6 link-local source address. And RFC 4861 does not provide an option for this kind of communication pattern.

EskoDijk commented 1 month ago

See also #62 , related.

EskoDijk commented 2 weeks ago

Discussed in #62 that an RFC 7084 compliant CE router does not qualify as a "SNAC router". So most of this discussion can move to issue 62. Leaving this issue open for a concrete fix of the introduction text that mentions Home Gateway, which is now not correct anymore.