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))

Brian E Carpenter <> Thu, 07 October 2021 03:31 UTC

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To: Carsten Bormann <>, Erik Kline <>
Cc: Michael Richardson <>,, The IESG <>, Donald Eastlake <>, =?UTF-8?Q?=c3=89ric_Vyncke?= <>,
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From: Brian E Carpenter <>
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Date: Thu, 7 Oct 2021 16:31:14 +1300
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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 07-Oct-21 15:13, Carsten Bormann wrote:
> On 7. Oct 2021, at 03:58, Erik Kline <> wrote:
>> To my knowledge the closest such thing would be RFC 3927.
>> I've never seen anything like an extension of sockaddr_in to add the equivalent of sin6_scope_id, though it's not hard to imagine what would be 
required to make some "sin_scope_id" thing work.
> Interesting.  While IPV6_MULTICAST_IF is defined in RFC 3493, the RFCs seem to be silent about IP_MULTICAST_IF.
> (This would be another case where an IP address would be combined with an ifindex, even if that is not called a “zone ID” there.)

Formally, IPv4 addresses are assigned to a host, but IPv6 addresses are assigned to an interface. And consequently, IPv6 has a scoped address architecture and a scoped multicast address architecture. I think it's normal 
that these are reflected in APIs and absent in IPv4 APIs.

I think the whole question of multicast addresses needs careful analysis, 
so personally I'd defer it for now.