IETF Logo Mail Archive

Re: Is 1111 1110 10 equal to 0xfe80 or 0x3fa?

Alexandre Petrescu <alexandre.petrescu@gmail.com> Fri, 07 June 2019 05:55 UTC

Return-Path: <alexandre.petrescu@gmail.com>
X-Original-To: ipv6@ietfa.amsl.com
Delivered-To: ipv6@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 9B92D12016A for <ipv6@ietfa.amsl.com>; Thu, 6 Jun 2019 22:55:25 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.632
X-Spam-Level:
X-Spam-Status: No, score=-2.632 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_ADSP_CUSTOM_MED=0.001, FREEMAIL_FROM=0.001, NML_ADSP_CUSTOM_MED=0.9, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_SOFTFAIL=0.665] autolearn=ham autolearn_force=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id zAmZas7lF-6U for <ipv6@ietfa.amsl.com>; Thu, 6 Jun 2019 22:55:22 -0700 (PDT)
Received: from oxalide-smtp-out.extra.cea.fr (oxalide-smtp-out.extra.cea.fr [132.168.224.13]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 4FAC8120164 for <ipv6@ietf.org>; Thu, 6 Jun 2019 22:55:22 -0700 (PDT)
Received: from pisaure.intra.cea.fr (pisaure.intra.cea.fr [132.166.88.21]) by oxalide-sys.extra.cea.fr (8.14.7/8.14.7/CEAnet-Internet-out-4.0) with ESMTP id x575tJjF050395; Fri, 7 Jun 2019 07:55:19 +0200
Received: from pisaure.intra.cea.fr (localhost [127.0.0.1]) by localhost (Postfix) with SMTP id BFFB8200DE5; Fri, 7 Jun 2019 07:55:19 +0200 (CEST)
Received: from muguet2-smtp-out.intra.cea.fr (muguet2-smtp-out.intra.cea.fr [132.166.192.13]) by pisaure.intra.cea.fr (Postfix) with ESMTP id B22A2200BBB; Fri, 7 Jun 2019 07:55:19 +0200 (CEST)
Received: from [10.8.68.40] ([10.8.68.40]) by muguet2-sys.intra.cea.fr (8.14.7/8.14.7/CEAnet-Internet-out-4.0) with ESMTP id x575tJTf030010; Fri, 7 Jun 2019 07:55:19 +0200
Subject: Re: Is 1111 1110 10 equal to 0xfe80 or 0x3fa?
To: Sander Steffann <sander@steffann.nl>
Cc: IPv6 <ipv6@ietf.org>
References: <a71b00b7-0e0c-242a-b3f7-147f4c6b2eb0@gmail.com> <D05C857F-42F6-4F17-8520-A0BF4C8FB775@steffann.nl>
From: Alexandre Petrescu <alexandre.petrescu@gmail.com>
Message-ID: <c57bc938-d151-a96d-7ea6-efca7a48648b@gmail.com>
Date: Fri, 07 Jun 2019 07:55:19 +0200
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0
MIME-Version: 1.0
In-Reply-To: <D05C857F-42F6-4F17-8520-A0BF4C8FB775@steffann.nl>
Content-Type: text/plain; charset="utf-8"; format="flowed"
Content-Language: fr
Content-Transfer-Encoding: 8bit
Archived-At: <https://mailarchive.ietf.org/arch/msg/ipv6/gI4srJ5-cGWB4mj4EQBX2BaeYho>
X-BeenThere: ipv6@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "IPv6 Maintenance Working Group \(6man\)" <ipv6.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/ipv6>, <mailto:ipv6-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/ipv6/>
List-Post: <mailto:ipv6@ietf.org>
List-Help: <mailto:ipv6-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/ipv6>, <mailto:ipv6-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 07 Jun 2019 05:55:26 -0000


Le 06/06/2019 à 20:46, Sander Steffann a écrit :
> Hi Alexandre,
> 
>> I maintain that 1111 1110 10 equals 0x3fa, because that's what my Windows Calculator says: I type 1111 1110 10 and it converts to 0x3fa.
>>
>> On another hand, I am rhetorically asked how can 1111 1110 10 be 0x3fa?
>>
>> (the 1111 1110 10 are the 10 leading bits of the IPv6 link local addresses, which is familiarly known to start with an fe80).
>>
>> On my side, this is a difficulty to understand this 0xfe80, especially since 1111 1110 10 is so printed in Figure in RFC4291.
> 
> It's a prefix of an IPv6 address. IPv6 addresses are 128 bits long. Expand to 128 bits and try again :)

(I will try that twice on some other calculator that has 64bit operators.)

Is it wrong to write that 3fa::/10 is the link-local prefix?

Alex

> 
> 1111 1110 1000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 equals 0xfe800000000000000000000000000000. Not sure if Windows Calculator can handle that though…
> 
> Cheers,
> Sander
>

v2.23.0 | Report a Bug | By Email