Re: [Tls-reg-review] Request to Register Value in TLS ALPN Registry

Yoav Nir <> Sat, 10 August 2019 09:07 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 488D3120099 for <>; Sat, 10 Aug 2019 02:07:38 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -1.997
X-Spam-Status: No, score=-1.997 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_FROM=0.001, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (2048-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id wo0uKW8Pa63X for <>; Sat, 10 Aug 2019 02:07:36 -0700 (PDT)
Received: from ( [IPv6:2a00:1450:4864:20::341]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id DAF65120098 for <>; Sat, 10 Aug 2019 02:07:35 -0700 (PDT)
Received: by with SMTP id m125so3538351wmm.3 for <>; Sat, 10 Aug 2019 02:07:35 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=from:message-id:mime-version:subject:date:in-reply-to:cc:to :references; bh=0rzajsNuwhv9eKeSTFQ0m92pfkkdiNXJBNmM7CPVOUQ=; b=Xu0235+z6lGZ3oMm8PRhLhLllIzuaoNumpQD+Rl748YvO77UTLyjokNUCTYD9XSuMS okqTgUHXiRApewYhXcTg5IgIxyFLVTrYIaJzLzU0YcYFyCFD0AG7qc5DZYturBf9iDtc qpkQgJr/jLnVVHEMD69E41MVxfBbuTzK9spszr6P7+n+yGf0cPccjf2da86JuGhqDTiG S1Um9E3sH8JELJQlCW82jK4noAH9leC9PmwVpZs5DZzJVuva9Zx1hT35f6VuihhP/yOB 7T/r9binOsvRfNDgXOvXkGuTXVYlDWURlczMaz67mMWly6k4Mso8yQi6WV9Mv78DqTt0 lV6A==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=x-gm-message-state:from:message-id:mime-version:subject:date :in-reply-to:cc:to:references; bh=0rzajsNuwhv9eKeSTFQ0m92pfkkdiNXJBNmM7CPVOUQ=; b=LxqMNWShJI7/i2oIKVeIzLy9ay7aOH0LUH5puv3Hdp6xyf5/lEzO02h25TEWwKJmIu FUSCyOoIzX2xY4ysJFZYtjyzb4ut9qEW+7K0KSLRQhIHEX69X6v4T9E9GicjAMwHB63y fdPYTMq7DGsAZNKHxba8DxKZB1IJJ6r7KYSuxMphjNLxV4oMkwm/mKaIfRdLMFXwoHRX VWMdFhMRlHA5SCFtRjp/Uy6YGYTQB5TeXzpWf5Vb3DY/8MwMYRaOeWZ3tIN8Xxh/1M8W p3J3SB1iQrXw+rIr1Kvh/F5ohzE30j3OQI5qa9F92fsXQn46MTD2el4fk0nQXJfe7XY8 zi3g==
X-Gm-Message-State: APjAAAXvcoY06MMQDlp7DzF9UxwDPIbodaFFqyZhZcgwBZa4pe8mYhB4 AanAc96i+Su7xgbTtMIGqBI=
X-Google-Smtp-Source: APXvYqzJgoIYwXD+RTMT0VGREUGtuu8VauWCt14nRtNcdENR/CVkZ9qB0SX33zP9suE6JyXCljOatQ==
X-Received: by 2002:a1c:ed06:: with SMTP id l6mr8055794wmh.128.1565428052983; Sat, 10 Aug 2019 02:07:32 -0700 (PDT)
Received: from [] ([]) by with ESMTPSA id x20sm220354758wrg.10.2019. (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 10 Aug 2019 02:07:27 -0700 (PDT)
From: Yoav Nir <>
Message-Id: <>
Content-Type: multipart/alternative; boundary="Apple-Mail=_93A5DE6F-D1B2-4F43-87B7-5995B5C3FD66"
Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\))
Date: Sat, 10 Aug 2019 12:07:24 +0300
In-Reply-To: <>
Cc: "" <>, "Lee, Alexandra" <>, "Sharfin, Jared" <>, "Gochenaur, Drew" <>
To: "Thakar, Eeshan" <>
References: <>
X-Mailer: Apple Mail (2.3445.104.11)
Archived-At: <>
Subject: Re: [Tls-reg-review] Request to Register Value in TLS ALPN Registry
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: TLS REVIEW <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Sat, 10 Aug 2019 09:07:39 -0000

On 9 Aug 2019, at 23:45, Thakar, Eeshan <> wrote:

> Type of Assignment:
> Registration of “mqtt” token
> Registry:
> Application Layer Protocol Negotiation (ALPN) Protocol ID
> Description:
> The mqtt protocol has the protocol version written into the first message on a connection. The mqtt server implementations typically understand the protocol version based on the fixed header on the first message (connect).
> Adding this protocol id to the registry will help the community since clients wanting to request mqtt as the protocol would have an appropriate specification reference to use.
> Additional Info:
> [1] MQTT 3.1 Specification: <>
> [2] MQTT 3.1.1 Specification: <>
> [3] MQTT 5.0 Specification: <>

Hi, Eeshan.

I’ve looked through the linked specifications, especially the third one because it says it replaces the others.

It says that TCP port 8883 is registered with IANA for MQTT over TLS, and the IANA registry confirms it.  If you have your own port, why do you need ALPN?

ALPN is used to negotiate a particular service (such as HTTP) over a single port, typically 443.  

So if you were using a server listening on port 443 and serving both MQTT and HTTP/2 you would need that to distinguish clients that need MQTT from web browsers that need HTTP/2.

The linked document does not make any mention of such a server.  Is this described elsewhere?