Re: [hybi] Alternative for SRV proposal

Iñaki Baz Castillo <ibc@aliax.net> Mon, 25 July 2011 09:51 UTC

Return-Path: <ibc@aliax.net>
X-Original-To: hybi@ietfa.amsl.com
Delivered-To: hybi@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id A129221F8879 for <hybi@ietfa.amsl.com>; Mon, 25 Jul 2011 02:51:27 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.648
X-Spam-Level:
X-Spam-Status: No, score=-2.648 tagged_above=-999 required=5 tests=[AWL=0.029, BAYES_00=-2.599, FM_FORGED_GMAIL=0.622, MIME_8BIT_HEADER=0.3, RCVD_IN_DNSWL_LOW=-1]
Received: from mail.ietf.org ([64.170.98.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id HV+pPnW7etKp for <hybi@ietfa.amsl.com>; Mon, 25 Jul 2011 02:51:26 -0700 (PDT)
Received: from mail-qy0-f179.google.com (mail-qy0-f179.google.com [209.85.216.179]) by ietfa.amsl.com (Postfix) with ESMTP id 6D7B421F8877 for <hybi@ietf.org>; Mon, 25 Jul 2011 02:51:26 -0700 (PDT)
Received: by qyk29 with SMTP id 29so2829869qyk.10 for <hybi@ietf.org>; Mon, 25 Jul 2011 02:51:25 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.229.66.222 with SMTP id o30mr3215237qci.189.1311587485429; Mon, 25 Jul 2011 02:51:25 -0700 (PDT)
Received: by 10.229.185.195 with HTTP; Mon, 25 Jul 2011 02:51:25 -0700 (PDT)
In-Reply-To: <20110725043751.GL22405@1wt.eu>
References: <CALiegfni83KAFTeo1vo_XLmLhVSAR_BxYwLoSkOizJ1ToHfqhw@mail.gmail.com> <20110724195600.GF22405@1wt.eu> <CALiegfn8B4YzbAz9zp8s6t=47nSqCaqc3SjH3LE5m6ffC3Ht+w@mail.gmail.com> <20110724205120.GH22405@1wt.eu> <CALiegfmw=emUhnyCvr8Lya00N9q7S06zOxvB9itg4ixjAH1kfg@mail.gmail.com> <20110725043751.GL22405@1wt.eu>
Date: Mon, 25 Jul 2011 11:51:25 +0200
Message-ID: <CALiegfmR4e894MFP_v3NWye7_Ck7vzxSZo5f2AbBZmMzSR-YPw@mail.gmail.com>
From: =?UTF-8?Q?I=C3=B1aki_Baz_Castillo?= <ibc@aliax.net>
To: Willy Tarreau <w@1wt.eu>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Cc: hybi@ietf.org
Subject: Re: [hybi] Alternative for SRV proposal
X-BeenThere: hybi@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Server-Initiated HTTP <hybi.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/hybi>, <mailto:hybi-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/hybi>
List-Post: <mailto:hybi@ietf.org>
List-Help: <mailto:hybi-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/hybi>, <mailto:hybi-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 25 Jul 2011 09:51:27 -0000

2011/7/25 Willy Tarreau <w@1wt.eu>eu>:
>> Hummm, AFAIK some local DNS resolvers automatically resolve the CNAME
>> domain to an IP before passing the DNS result to the application, so
>> the application would not be aware of the existence of a CNAME record.
>
> I'm not aware of that and it sounds strange to me.

I was not exactly right. I use a local DNS cache/resolver (called
Unbound for Linux).

- I query it a DNS A for ghs.google.com.
- Unbound queries it to the DNS server.
- It receives a reply telling that ghs.google.com has just a CNAME
record (ghs.l.google.com).
- Unbound then queries DNS A for ghs.l.google.com.
- It receives "209.85.147.121".
- Then Unbound replies to my client with two answers:
    1) ghs.google.com: CNAME, cname ghs.l.google.com
    2) ghs.l.google.com: A, addr 209.85.147.121

So yes, by inspecting the DNS response the client can realize of the
presence of a CNAME for the queried domain.




>> But this would be an extra DNS query so there would be:
>>
>> a) NAPTR + SRV +`A/AAAA
>>
>> or
>>
>> b) NAPTR + A/AAAA
>>
>> It does not fit well with constrains exposed in the other mail thread.
>
> It does fit well as something at the option of the end user, because as
> Mark says, one can send the NAPTR + A + AAAA "at zero cost" (assuming
> the uplink is infinite). It does not require extra round trips, just
> extra bandwidth and some extra synchronization from the client.

It sounds good but, wouldn't it be too much not required information?
this is, a DNS ANY query retrievesa all the resource records for the
given domain.

-- 
Iñaki Baz Castillo
<ibc@aliax.net>