Re: [6lo-fragmentation-dt] Performance report for fragment forwarding

Rahul Jadhav <rahul.ietf@gmail.com> Wed, 19 September 2018 06:01 UTC

Return-Path: <rahul.ietf@gmail.com>
X-Original-To: 6lo-fragmentation-dt@ietfa.amsl.com
Delivered-To: 6lo-fragmentation-dt@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 3DE02130E9B for <6lo-fragmentation-dt@ietfa.amsl.com>; Tue, 18 Sep 2018 23:01:25 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.998
X-Spam-Level:
X-Spam-Status: No, score=-1.998 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_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=gmail.com
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 KoMJD5ZK9BTF for <6lo-fragmentation-dt@ietfa.amsl.com>; Tue, 18 Sep 2018 23:01:22 -0700 (PDT)
Received: from mail-ua1-x92a.google.com (mail-ua1-x92a.google.com [IPv6:2607:f8b0:4864:20::92a]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id F2669130F66 for <6lo-fragmentation-dt@ietf.org>; Tue, 18 Sep 2018 23:01:21 -0700 (PDT)
Received: by mail-ua1-x92a.google.com with SMTP id g18-v6so2115850uam.6 for <6lo-fragmentation-dt@ietf.org>; Tue, 18 Sep 2018 23:01:21 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=XB/R10VNtnSue2nyef4CxPvQOZx8+5jMwqkqEF5v49Q=; b=rX3DY33k0o19bV8nG47/ej4QEiQlSqWjWK9s+iQHh41fA8lO6GDxQmcv5FzR4ngnTL ap7PzZfS2fZ8gQLXWJUGOQl+TA+Mv5cjlqm81MVsoQGw+YQVLCPMWJv48KNpfdUGJzWJ h5KeXkr00D3e+31MelwTfpGqWw/ZR+Ija9rSfaJJ5yp1Oj8IuukzjWrnv6DaAEMs9pRf 9y4VMZzIYP/PilU2GeBLVTdTXQiuA5BVyReaHF/inWmvqgqGipSaueL2+6DEwfsZb8Q1 RexCWzmu+WhRcQr0T44udw/xihcgh7LT5FL9s2wDuG6wdbcyVrgjJZ+JxF6ynWvC8Ett /v2g==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=XB/R10VNtnSue2nyef4CxPvQOZx8+5jMwqkqEF5v49Q=; b=izqw3DaPAfqJ/WxHMtZIRAaXdTd2cVxxCbD/2GlV29UzvXx0vRMTCmTMG8KailTnl/ 4R5fpEquejGQe+5080/HikyliG9rZykYAGD3YVbEbygn1R2GOGqWGm+o4jC0Ie0uwCJe qv6l9x8/HRqECYTD9LfISWheRT4Ts3XdKdOc0nKGhBTQ7a7LObdsIh0KLSyG29nw2xka SKoD9Idkk8sn6ryqG4El/U7iUVpcH/wT7kL9W0+Qtt88wvvI/bjS0lnUU5JijiOJvNBa Jw7oJG/cUMESAMS/afMWK2SMMOvRMYKDkMWrzwVhVxolJaBqfAtxMbxjhWElaoiJjYmL KQYA==
X-Gm-Message-State: APzg51CwBM6A/1XN2uTyJtX5zhK1PQSPP2aLv8f13ctknYMtPJZDE0/m hsD8WpQzjXaj47AOxHNnnORa+pEAGGWESLfzYWE=
X-Google-Smtp-Source: ANB0VdbomAuwG2YBC4YsuhYJR0kbqWOCwFDbgN+iFN2xJ+85PK316y4/RWWuyvwGn/tqJhfXvNa41vwTCsges0SjrmE=
X-Received: by 2002:a9f:2b87:: with SMTP id y7-v6mr9745766uai.109.1537336880966; Tue, 18 Sep 2018 23:01:20 -0700 (PDT)
MIME-Version: 1.0
References: <CAO0Djp2EKyiZK5-b+_R4c557mXSktPCEtYxOQjQb4vreTVOX9g@mail.gmail.com> <C3A37ED0-C93B-4D1B-9E6D-857B14253874@tzi.org> <CAO0Djp37FHUaoLPEhfLMX2dmEb+=DY0XdYLUDvq1AOuT9to8ZQ@mail.gmail.com> <B340B396-A1C0-49D6-BCBF-A8C04D98F8C9@cisco.com>
In-Reply-To: <B340B396-A1C0-49D6-BCBF-A8C04D98F8C9@cisco.com>
From: Rahul Jadhav <rahul.ietf@gmail.com>
Date: Wed, 19 Sep 2018 11:31:09 +0530
Message-ID: <CAO0Djp2X0kaN2L=k3h8uR2Ab+f9BUBX9Jp5Nq6K-RsgkVJzrOA@mail.gmail.com>
To: "Pascal Thubert (pthubert)" <pthubert@cisco.com>
Cc: Carsten Bormann <cabo@tzi.org>, rabinarayans@huawei.com, 6lo-fragmentation-dt@ietf.org, yasuyuki.tanaka@inria.fr
Content-Type: multipart/alternative; boundary="000000000000b0b248057633226a"
Archived-At: <https://mailarchive.ietf.org/arch/msg/6lo-fragmentation-dt/P61tPhoQAk66BGtlRDLEcrwlt_w>
Subject: Re: [6lo-fragmentation-dt] Performance report for fragment forwarding
X-BeenThere: 6lo-fragmentation-dt@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: 6lo Fragmentation Design Team <6lo-fragmentation-dt.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/6lo-fragmentation-dt>, <mailto:6lo-fragmentation-dt-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/6lo-fragmentation-dt/>
List-Post: <mailto:6lo-fragmentation-dt@ietf.org>
List-Help: <mailto:6lo-fragmentation-dt-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/6lo-fragmentation-dt>, <mailto:6lo-fragmentation-dt-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 19 Sep 2018 06:01:25 -0000

Agreed. 6TiSCH with nodes using non-shared cells for transmission will be
the best deployment scenario for fragment-forwarding.
Unfortunately our testbest currently does not support TSCH and thus we wont
be able to report the numbers.

On Wed, 19 Sep 2018 at 11:08, Pascal Thubert (pthubert) <pthubert@cisco.com>;
wrote:

> Hello Rahul
>
> Pacing is another word for introducing delay between fragments and yes
> thus locks the buffers for a longer time. Having to do retries because a
> fragment interferes with the next also introduces delay, and possibly
> longer if you keep at it.
>
> The key message in my talk was that this problem simply goes away with
> 6TiSCH. I think that should be the key message of your writing...
>
> Take care,
>
> Pascal
>
> Le 19 sept. 2018 à 06:25, Rahul Jadhav <rahul.ietf@gmail.com>; a écrit :
>
> Thanks Pascal, Carsten for the comments.
>
> Pascal, Introducing delay is easy but it has further complications with
> regards to buffering requirement. Holding the fragment with a delay while
> receiving more fragments from the downstream would mean keeping additional
> buffers.
> Carsten also mentioned a pacing mechanism .. while it might improve fwding
> efficiency it will add to buffer requirement. Also such a scheme might be
> non-trivial to be implemented.
>
> Also Carsten, the PDR we reported takes into consideration all factors,,
> buffering as well (we use contiki and have single 1280B buffer on each
> node). While the transmission scheme we chose results in much less impact
> on buffering, it is much closer to our traffic pattern expectation.
>
> Regarding keeping higher mac-retry, ... We have chosen mac-retry of 3
> after some experimentation (considering expected node densities and tx
> frequency). increasing mac-retry might not necessarily help, in fact it may
> backfire in terms of both PDR as well as mean latency. Would you still
> suggest to give it a try and what mac-retry do you think makes sense ?
>
> Based on your comment, we will document the fragments dropped on nodes in
> both scenarios, just to be clear.
>
> Thanks,
> Rahul
>
> On Wed, 19 Sep 2018 at 01:29, Carsten Bormann <cabo@tzi.org>; wrote:
>
>> Hi Rahul,
>>
>> the memory issues in forwarders discussed during IETF101 are real, and
>> they would need to enter the calculations about PDR differences.
>>
>> Is a max-retry of 3 something that people are actually choosing? Sounds
>> low to me.
>>
>> More importantly, it seems we neglected to discuss pacing in both
>> draft-watteyne-6lo-minimal-fragment-02.txt and
>> draft-ietf-lwig-6lowpan-virtual-reassembly-00.txt.  Pacing is essential for
>> fragment forwarding (as it is for any application that sends more than one
>> datagram in a row).  If the original sender does not pace, there will
>> always be a collision between the forwarding of fragment N and the
>> origination of fragment N+1.
>>
>> Unfortunately, pacing is another knob that needs to be tuned, and I’m not
>> aware of good research that tells us what  the right setting for that knob
>> is.  Ideally, we’d want it to be self-tuning.
>>
>> Grüße, Carsten
>>
>>
>> > On 18. Sep 2018, at 18:05, Rahul Jadhav <rahul.ietf@gmail.com>; wrote:
>> >
>> > << turns out my earlier mail didn't reach the ML; trying again >>
>> >
>> > Hello all,
>> >
>> > We experimented with Fragment Forwarding and tried to understand the
>> performance implications vis-a-vis per-hop reassembly.
>> >
>> > Following is the detailed report:
>> >
>> https://github.com/nyrahul/ietf-data/blob/master/6lo-fragfwd-perf-report.md
>> >
>> > To summarize, we found that fragment forwarding has some practical
>> issues when it comes to forwarding efficiency or PDR "on single channel
>> 802.15.4". While similar concerns were been raised previously during IETF
>> meetings, we tried to validate it with data.
>> >
>> > Please let us know if any comments.
>> >
>> > Regards,
>> > Rahul
>> >
>> > _______________________________________________
>> > 6lo-fragmentation-dt mailing list
>> > 6lo-fragmentation-dt@ietf.org
>> > https://www.ietf.org/mailman/listinfo/6lo-fragmentation-dt
>>
>> _______________________________________________
> 6lo-fragmentation-dt mailing list
> 6lo-fragmentation-dt@ietf.org
> https://www.ietf.org/mailman/listinfo/6lo-fragmentation-dt
>
>