Re: [Cbor] Supporting IPv6 Link-Local with scope (was Re: Éric Vyncke's Discuss on draft-ietf-cbor-network-addresses-09: (with DISCUSS and COMMENT))

Thiago Macieira <thiago.macieira@intel.com> Thu, 07 October 2021 18:42 UTC

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From: Thiago Macieira <thiago.macieira@intel.com>
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Date: Thu, 07 Oct 2021 11:42:09 -0700
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Subject: Re: [Cbor] =?utf-8?q?Supporting_IPv6_Link-Local_with_scope_=28was_Re?= =?utf-8?q?=3A_=C3=89ric_Vyncke=27s_Discuss_on_draft-ietf-cbor-network-add?= =?utf-8?q?resses-09=3A_=28with_DISCUSS_and_COMMENT=29=29?=
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On Thursday, 7 October 2021 11:31:54 PDT Michael Richardson wrote:
>     > - Is "false" for a prefix length a better choice than using either -1
>     > or null?
> We've gone for null.

false, null, 0, -1 and an empty string all have the same length and meaning 
for interfaces indices and names. Null makes the purpose clear (information 
absent) and the distinction between that and 0 might be important somewhere.

Like C++ std::optional<PointerType>: a disengaged optional is different from a 
an engaged optional containing a null pointer. One of those may convey "an 
error occurred" whereas the other says "success, information not applicable". 
Though I'd suggest using undefined for errors in CBOR, instead of null. So 
maybe a null interface is "valid, but missing", an undefined interface is 
"invalid, error" and a zero/empty interface is "not applicable in this 
context" (such as all non-link-local cases).

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel DPG Cloud Engineering