Return-Path: Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id C6F85C0051 for ; Fri, 21 Aug 2020 21:17:47 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id C2A80887C3 for ; Fri, 21 Aug 2020 21:17:47 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id kRPBMfmeyIPi for ; Fri, 21 Aug 2020 21:17:47 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) by whitealder.osuosl.org (Postfix) with ESMTPS id DA1FA887C0 for ; Fri, 21 Aug 2020 21:17:46 +0000 (UTC) Received: from mail-ed1-f49.google.com (mail-ed1-f49.google.com [209.85.208.49]) (authenticated bits=0) (User authenticated as jlrubin@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 07LLHiKi027500 (version=TLSv1/SSLv3 cipher=AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 21 Aug 2020 17:17:45 -0400 Received: by mail-ed1-f49.google.com with SMTP id l23so2679064edv.11 for ; Fri, 21 Aug 2020 14:17:45 -0700 (PDT) X-Gm-Message-State: AOAM531HyfOhCywHCXtBVUp3xyIaXY1c18uHndABNuzx4YRrp+biuq4I ToNjHozzLZPsx4qsEpy/IIZTyLXpjcKsQSKN6EY= X-Google-Smtp-Source: ABdhPJwslBBWVfllmXoeoH8rX71DsS9P6CMlNrpg/Y/xNOKfRHIcXfRIftTud66PZZyk8ii+AyDzDf8TOSE+UqIHLvQ= X-Received: by 2002:aa7:d45a:: with SMTP id q26mr4646702edr.95.1598044664317; Fri, 21 Aug 2020 14:17:44 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Jeremy Date: Fri, 21 Aug 2020 14:17:32 -0700 X-Gmail-Original-Message-ID: Message-ID: To: Jeremy Content-Type: multipart/alternative; boundary="0000000000008d4be305ad69c454" Cc: Bitcoin Protocol Discussion Subject: Re: [bitcoin-dev] Generalizing feature negotiation when new p2p connections are setup X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 21 Aug 2020 21:17:47 -0000 --0000000000008d4be305ad69c454 Content-Type: text/plain; charset="UTF-8" As for an example of where you'd want multi-round, you could imagine a scenario where you have a feature A which gets bugfixed by the introduction of feature B, and you don't want to expose that you support A unless you first negotiate B. Or if you can negotiate B you should never expose A, but for old nodes you'll still do it if B is unknown to them. An example of this would be (were it not already out without a feature negotiation existing) WTXID/TXID relay. The SYNC primitve simply codifies what order messages should be in and when you're done for a phase of negotiation offering something. It can be done without, but then you have to be more careful to broadcast in the correct order and it's not clear when/if you should wait for more time before responding. On Fri, Aug 21, 2020 at 2:08 PM Jeremy wrote: > Actually we already have service bits (which are sadly limited) which > allow negotiation of non bilateral feature support, so this would supercede > that. > -- > @JeremyRubin > > --0000000000008d4be305ad69c454 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
As for an exampl= e of where you'd want multi-round, you could imagine a scenario where y= ou have a feature A which gets bugfixed by the introduction of feature B, a= nd you don't want to expose that you support A unless you first negotia= te B. Or if you can negotiate B you should never expose A, but for old node= s you'll still do it if B is unknown to them. An example of this would = be (were it not already out without a feature negotiation existing) WTXID/T= XID relay.

The SYNC primitve simp= ly codifies what order messages should be in and when you're done for a= phase of negotiation offering something. It can be done without, but then = you have to be more careful to broadcast in the correct order and it's = not clear when/if you should wait for more time before responding.


On Fri, Aug 21, 2020 at 2:08 PM Jeremy <jlrubin@mit.edu> wrote:
Actually we already have service bits (which are sadly limited) which all= ow negotiation of non bilateral feature support, so this would supercede th= at.
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