Re: [Roll] processing of multiple SRH-6LoRH

"Pascal Thubert (pthubert)" <> Tue, 26 April 2016 11:22 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id D49BA12D0F8 for <>; Tue, 26 Apr 2016 04:22:02 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -15.514
X-Spam-Status: No, score=-15.514 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DC_PNG_UNO_LARGO=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HTML_IMAGE_RATIO_06=0.001, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_HI=-5, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, RP_MATCHES_RCVD=-0.996, SPF_PASS=-0.001, USER_IN_DEF_DKIM_WL=-7.5] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (1024-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id XaS9dYoUaVGE for <>; Tue, 26 Apr 2016 04:22:01 -0700 (PDT)
Received: from ( []) (using TLSv1.2 with cipher DHE-RSA-SEED-SHA (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id EAA2512D0DF for <>; Tue, 26 Apr 2016 04:22:00 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;;; l=103617; q=dns/txt; s=iport; t=1461669721; x=1462879321; h=from:to:subject:date:message-id:references:in-reply-to: mime-version; bh=N15oaBIw45WaM1tAKJgXSWCo3KPiPQOkA0+iXIf+BJg=; b=NQUgiO9XMNmv//ekoiIRtQyVXhGcvRTGbZin7sV8N4GWV1iTii1cakMV PuJjBL/tNHDxcow9O/UEps2Ud/GC8VE+1W0hyIp7G0KKc3zuUWVI5DMN3 SUmSQIYiF6N74TxvdfwB0bFz/shOHd8PThaDZ+zeRU4gDFzg4/rgC1gVn g=;
X-Files: image002.png : 69836
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-AV: E=Sophos;i="5.24,536,1454976000"; d="png'150?scan'150,208,217,150";a="95700078"
Received: from ([]) by with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Apr 2016 11:21:59 +0000
Received: from ( []) by (8.14.5/8.14.5) with ESMTP id u3QBLxjq021975 (version=TLSv1/SSLv3 cipher=AES256-SHA bits=256 verify=FAIL); Tue, 26 Apr 2016 11:21:59 GMT
Received: from ( by ( with Microsoft SMTP Server (TLS) id 15.0.1104.5; Tue, 26 Apr 2016 06:21:58 -0500
Received: from ([]) by ([]) with mapi id 15.00.1104.009; Tue, 26 Apr 2016 06:21:58 -0500
From: "Pascal Thubert (pthubert)" <>
To: Michael Richardson <>, "" <>
Thread-Topic: processing of multiple SRH-6LoRH
Thread-Index: AQHRnJ2wylNlxUmyfEazm/DB5NwW4p+cFgjQ
Date: Tue, 26 Apr 2016 11:21:34 +0000
Deferred-Delivery: Tue, 26 Apr 2016 11:21:04 +0000
Message-ID: <>
References: <>
In-Reply-To: <>
Accept-Language: fr-FR, en-US
Content-Language: en-US
X-MS-Has-Attach: yes
x-ms-exchange-transport-fromentityheader: Hosted
x-originating-ip: []
Content-Type: multipart/related; boundary="_004_5e93d811225e4a9bab5840a750012eb1XCHRCD001ciscocom_"; type="multipart/alternative"
MIME-Version: 1.0
Archived-At: <>
Subject: Re: [Roll] processing of multiple SRH-6LoRH
X-Mailman-Version: 2.1.17
Precedence: list
Reply-To: Routing Over Low power and Lossy networks <>
List-Id: Routing Over Low power and Lossy networks <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Tue, 26 Apr 2016 11:22:03 -0000

Hello Michael:

Sorry I failed to respond to this.

> Pascal,


> section 5.5 of routing-dispatch says:


>    Else, if there is a next SRH-6LoRH of a Type with a larger or equal

>       value, meaning a same or lesser compression yielding same or larger

>       compressed forms, then the SRH-6LoRH is removed.


> okay, so when the new SRH provides more bytes, we remove the consumed

> one.


>    Else, the first entry of the next SRH-6LoRH is popped from the next

>       SRH-6LoRH and coalesced with the first entry of this SRH-6LoRH.


> To get here, the next SRH-6LoRH must be of a higher level of compression, so

> it encodes addresses with fewer bytes.  What is the logic to making the next

> next 6LoRH smaller (popping), and keeping the larger current 6LoRH?

This is illustrated below:


The root sends a type 4 with the fill address of A (say that they do not share a same prefix)

When A receives the packet it must remove the first address in the SRH which is self.

As illustrated A pops B's compressed address from the next header (the type 3) and coalesces that in the first (type 4) to get the full address of B.

> Why not just drop the current 6loRH here and have fewer bytes, period?

If we had removed the type 4 then the first SRH would have been the type 3 and the prefix would be lost.

Makes sense?