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From: Jonas Schnelli <dev@jonasschnelli.ch>
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Date: Thu, 3 Nov 2022 12:26:54 -1000
References: <56677685-619a-691f-d5bc-54b69fdb6ed2@bip324.com>
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 <d4272a20-b2a7-4ad8-9b41-8ce2b7ce827d@murch.one>
To: Murch <murch@murch.one>,
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
In-Reply-To: <d4272a20-b2a7-4ad8-9b41-8ce2b7ce827d@murch.one>
Message-Id: <87FFCF31-946A-44AE-8AAE-6FA3E6465C89@jonasschnelli.ch>
Subject: Re: [bitcoin-dev] Refreshed BIP324
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> =46rom what I understand we'll have about 35 message types on the =
network with the addition of BIP324. 256 possible IDs sounds like plenty =
room to grow, but perhaps we can be a bit more conservative:
>=20
> We could use the first bit to signal a 2-byte message ID. That allows =
us to express 128 IDs with 1 byte, but if we need more, we get a total =
of 2^15 IDs across 2 bytes.

Could make sense.

There would be an alternative to preserve more 1 byte IDs on the cost of =
a (much) smaller 2 byte ID space:
Reserve the short ID 0xFF as an indication for a 2 bytes short ID =
(additional 256 short IDs with 2 bytes).
That could be done later outside BIP324.
The 0xFF approach would lead to approx. 207 unused 1 byte short IDs =
(while Murchs approach would give us approx. 79 unused 1 byte short =
IDs).
The signal bit two byte approach would however lead to ~32k more two =
byte message IDs.

The main (and only?) benefit of short IDs is bandwidth.
Short ID 1-12 are reserved for string based IDs and thus, new and rarely =
sent message types must not always use a short ID.

Maybe the BIP should state that only frequent sent messages should =
reserve a short ID, though, the BIP itself assigns short IDs to all(?) =
message types (including low frequent messages like SENDHEADERS).

Maybe exclude message types that expected to be only sent once from =
assigning a short ID?

/j=