Re: [nvo3] Number assignments

Dale,

Ethertypes are allocated not by IANA, but IEEE. See
https://standards.ieee.org/develop/regauth/ethertype/ for further
information.

Cheers,
Andy

On Sat, Jul 22, 2017 at 4:15 AM, Dale R. Worley <worley@ariadne.com> wrote:

> The concept of Geneve as a generalized encapsulation technique -- or
> even the concept of some alternative to Geneve as a generalized
> encapsulation technique -- brings very little overhead other than
> demands on number assignments.  This message is an exercise to work
> through the implications of that idea.
>
> When Geneve is used over layer 4, UDP, then there needs to be an
> assigned UDP destination port.  IANA has assigned 6081 as the port
> number.
>
> When Geneve is used over layer 3, IP, it needs a protocol/next header
> value.  Protocol values are only 8 bits, but only a bit over half of the
> space has been allocated in 30 years, so it seems that there's not a lot
> of pressure on the number-space.
>
> When Geneve is used over layer 2, Ethernet, it needs an Ethertype
> value.  But only 3,500 Ethertypes have been assigned out of a space of
> 64k.
>
> In theory, Geneve could be used over layer 1, in which case the
> underlying protocol doesn't have a next-protocol field, but rather the
> layer 2 protocol is configured by the operational environment
>
> The Geneve header contains a next-protocol field, which is an Ethertype,
> which signals the overlying protocol.
>
> When layer 2 is used over Geneve, the next-protocol is 6558
> (encapsulated Ethernet).
>
> When layer 3 is used over Geneve, the next-protocol is 0800 (IPv4) or
> 86DD (IPv6).
>
> When layer 4 is used over Geneve, things are more complicated, because
> there's no defined way of representing an IP protocol/next header value
> directly as an Ethertype, and few or no protocols that can be
> represented as such a value have assigned Ethertypes.
>
> It seems to me that it would be useful to embed the IP protocol/next
> header value space into the Ethertype space by allocating a block of 256
> Ethertypes, xx00 to xxFF, to IANA, to represent the protocol/next header
> values.  This is a large allocation, but the Ethertype space is thinly
> allocated and ony 60 or so of the possible first-byte values are used,
> leaving over 150 choices to allocate.
>
> Thus, if we are to generalize Geneve (or any similar protocol) to be
> used over and under various protocol layers, we need these additional
> IANA assignments:
>
> - a protocol/next header value to indicate Geneve
>
> - an Ethertype to indicate Geneve
>
> - a 256-value block of Ethertypes that are assigned to IANA to embed the
>   protocol/next header value space
>
> Comments?
>
> Dale
>
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