Subject: [6tisch] FW: Re: Time to Live - ASN in a packet

From: "Lijo Thomas" <[email-masked]>
Date: Wed, 31 Aug 2016 18:00:18 +0530

Hi all,

This is for your information.

Following are the mail interactions with Shwetha regarding the subject

Further inputs on the topic are most welcome..

Thanks & Regards

Lijo Thomas

-------- Forwarded Message -------- 

Subject: 

Re: [6tisch] Time to Live - ASN in a packet

Date: 

Fri, 26 Aug 2016 18:29:34 +0530 (IST)

From: 

Lijo Thomas  <mailto:[email-masked]> <[email-masked]>

Reply-To: 

Lijo Thomas  <mailto:[email-masked]> <[email-masked]>

To: 

Shwetha Bhandari (shwethab)  <mailto:[email-masked]%3e> <[email-masked]>

Hi Shwetha, 

Your proposal sounds good ! 

Since the intermediate nodes does not have to modify the packet, your suggestion suits the constrained environments as well. 

Thanks & Regards 

Lijo Thomas 

On August 26, 2016 at 2:14 PM "Shwetha Bhandari (shwethab)"  <mailto:[email-masked]> <[email-masked]> wrote: 

Hi Lijo, 

Very interesting use case, thanks for sharing the details. 

So at a minimum you will need to: 

*	timestamp when the packet starts its journey in the deterministic domain
*	A threshold delay that is acceptable

The above can be expressed as a future timestamp that specifies the cutoff time to deliver the packet to its destination. 

Given this, the intermediate hops need not update the value, but only read it to check the time remaining as the clocks are synchronized. 

Is that a fair assumption? 

If yes perhaps we can define a new type of Edge to Edge option that we have defined here -  https://tools.ietf.org/html/draft-brockners-inband-oam-data-01#section-3.3 

That will include the [timestamp + max delay] at the originator and be examined at every hop and used for scheduling.  

Something like: 

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Option Type  |  Opt Data Len | OAM-E2E-Type  |    reserved   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      E2E Option data format determined by iOAM-E2E-Type       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 
 iOAM-E2E-Type:  8-bit identifier of a particular in-band OAM E2E
      variant.
         0: E2E option data is a 64-bit sequence number added to a
         specific tube which is used to identify packet loss and
         reordering for that tube.
         1: E2E option data is a 64-bit timestamp …..

Thoughts?
 
Thanks,
Shwetha

From: Lijo Thomas <  <mailto:[email-masked]> [email-masked]> 
Reply-To: Lijo Thomas <  <mailto:[email-masked]> [email-masked]> 
Date: Friday, August 26, 2016 at 11:59 AM 
To: Shwetha bhandari <  <mailto:[email-masked]> [email-masked]> 
Cc: "Frank Brockners (fbrockne)" <  <mailto:[email-masked]> [email-masked]>, "  <mailto:[email-masked]> [email-masked]" <  <mailto:[email-masked]> [email-masked]>, "  <mailto:[email-masked]> [email-masked]" <  <mailto:[email-masked]> [email-masked]> 
Subject: Re: [6tisch] Time to Live - ASN in a packet 

Hi Shwetha, 

Thanks for the very useful inputs! 

I thought I will briefly describe the context. 

We are implementing a distributed scheduling scheme on a 6tisch network to 
support flows with strict delay contstaints. In some sense, we are working on 
deterministic networking. As you might be aware, there are several distributed 
algorithms in the literature such as EDF, LLF and so forth where intermediate 
nodes schedules packets based on the per-flow delay requirements, remaining 
time left to reach the destination, delay already experienced. These 
distributed debt based schemes attempt to meet the deadlines of the flows, 
thereby enabling us to realise deterministic networks. 

Therefore, the scheduler running on the nodes need to know the remaining time 
left before which the packet should reach the receiver. Since the 6tisch 
network is time synchronized, we are thinking of using ASN as a means to 
update the remaining time left. The originator specifies the maximum time 
limit. 

I went through your draft. Thanks for the same! From my understanding, it 
appears that we may have to use OAM-trace-type : 0x00001001 for our 
requirement. 

I am not sure if the above type can be used in our problem setting. 

Hence I would like to know if there is any specfic format explicitly defined 
considering the case of LLNs for including the Time field in hop by hop header, 
something similar to inclusion of RPL packet information in HbH. 

I would like to discuss more on this topic if you feel it is interesting. 

Thanks & Regards 

Lijo Thomas 

On August 26, 2016 at 5:44 AM "Shwetha Bhandari (shwethab)" < [email-masked] <mailto:[email-masked]> > wrote: 

Hi Lijo, 

We have the implementation in VPP, you can refer to the code  here <https://gerrit.fd.io/r/gitweb?p=vpp.git;a=blob;f=vnet/vnet/ip/ip6_hop_by_hop.c;h=7038556848c3d325b6612678a903f26cbf671de5;hb=HEAD> . 

If you want to try it out in your experiment do let us know we can help with more documentation to bring it up. 

We have some of our demos available here <https://www.youtube.com/channel/UC0WJOAKBTrftyosP590RrXw> . 

Do keep us posted on the hardware study and any modification that you try for constrained environment. 

Thanks, 

Shwetha 

From: Lijo Thomas <  <mailto:[email-masked]> [email-masked]> 
Reply-To: Lijo Thomas <  <mailto:[email-masked]> [email-masked]> 
Date: Thursday, August 25, 2016 at 5:48 PM 
To: Shwetha bhandari <  <mailto:[email-masked]> [email-masked]> 
Cc: "Frank Brockners (fbrockne)" <  <mailto:[email-masked]> [email-masked]> 
Subject: Re: [6tisch] Time to Live - ASN in a packet 

Hi Shwetha, 

Excellent.. 

Thanks for the inputs,  we are looking for a solution exactly suggested by you. 

we are implementing our algorithm on hardware and will get back to you . 

Thanks & Regards 

Lijo Thomas 

On August 25, 2016 at 3:54 PM "Shwetha Bhandari (shwethab)" < [email-masked] <mailto:[email-masked]> > wrote: 

Hi Lijo, 

We are trying something similar with In-band OAM – defining HbH options to collect timestamps, node, interface information as the packet traverses the nodes. Please take a look at the following: 

https://tools.ietf.org/html/draft-brockners-inband-oam-data-01#section-3.1 <https://tools.ietf.org/html/draft-brockners-inband-oam-data-01>  

https://tools.ietf.org/html/draft-brockners-inband-oam-transport-01#section-3.1 

Thanks, 

Shwetha 

From: 6tisch <  <mailto:[email-masked]> [email-masked]> on behalf of Lijo Thomas <  <mailto:[email-masked]> [email-masked]> 
Reply-To: Lijo Thomas <  <mailto:[email-masked]> [email-masked]> 
Date: Thursday, August 25, 2016 at 3:37 PM 
To: Thomas Watteyne <  <mailto:[email-masked]> [email-masked]>, "Pascal Thubert (pthubert)" <  <mailto:[email-masked]> [email-masked]> 
Cc: "  <mailto:[email-masked]> [email-masked]" <  <mailto:[email-masked]> [email-masked]> 
Subject: Re: [6tisch] Time to Live - ASN in a packet 

Hi Pascal & Thomas, 

The problem is inline with Pascal's comment on "looking for per packet information to as to monitor and maybe influence the forwarding and delivery" 

We are proposing a debt based distributed scheduling scheme where nodes make forwarding decisions based on the PDR and end-to-end delay requirement 
of flows. 

We simulated our algorithm using 6tisch simulator and got encouraging results. For this, we plugged in ASN value in the application payload and the intermediate node updates the ASN value before forwarding. 

Now we are implementing the algorithm on the hardware using OpenWSN environment and intend to do inline with the standard.    

We are actually contemplating on HbH at L3, similar to RPL RPI as described in RFC 6553 

But we would like to understand that if any options is available in the 6tisch framework. 

Expecting your valuable comments..!!!!!!!!!! 

Thanks & Regards 

Lijo Thomas 

On August 25, 2016 at 1:39 PM "Pascal Thubert (pthubert)" < [email-masked] <mailto:[email-masked]> > wrote: 

Hello Lijo:

Like Thomas, I’d love to understand what your case and solution approach is. Is asynchronous OAM like the openWSN application enough for you? Or else are you looking for per packet information to as to monitor and maybe influence the forwarding and delivery?

In the latter case, your work may be related to other efforts, and if your experimentation is successful then why not consider a more general applicability?

All in all I have this feeling that time-aware forwarding is on the way, in which exact shape and form is left TBD:

-        DetNet is discussing validating the end-to-end latency of individual packets to make sure that the delivery was within bounds. Is that similar to your need?

-        I’ve participated to work where the QoS of the packet was estimated at each hop depending on whether the packet was early or late vs. a predefined schedule. This makes things much simpler but slightly less deterministic than a tight scheduling. 

-        There’s also OAM work that uses HbH headers to monitor the packets as they flow along the network (IOW, in band as opposed to asynchronous OAM packets)

My understanding is that you want HbH behavior. 

-        If you are doing a mesh, you can probable hack a mesh header. 

-        But if you are considering a larger applicability (I hope so!) then you probably want to hack at L3. 

You can find tons of ideas of what can be done at L3 in various environments in  <https://tools.ietf.org/html/draft-dt-detnet-dp-alt-03> https://tools.ietf.org/html/draft-dt-detnet-dp-alt-03, which is pending adoption call. 

But if you narrow down to 6TiSCH, then you probably want to design you own option in the HbH header and incode it in a 6LoRH similar to the RPL RPI. You may use ASN to start with, but when going standard you’ll have to abstract that a little bit, even if the data in the packet is unchanged.

Very keen to hear more!

Pascal

From: 6tisch [ <mailto:[email-masked]> mailto:[email-masked]] On Behalf Of Thomas Watteyne
Sent: jeudi 25 août 2016 08:28
To: Lijo Thomas < <mailto:[email-masked]> [email-masked]>
Cc:  <mailto:[email-masked]> [email-masked]
Subject: Re: [6tisch] Time to Live - ASN in a packet

Lijo,

It looks like you are describing two things: the TTL (or hop limit in IPv6 parlance) which decrements by one by each router, and some timestamp which can be used to measure end -to-end latency. I'm assuming the latter.

I'm also assuming you are doing this as part of an experiment, to look at the end-to-end/hop-by-hop latency. In that context, you probably aren't looking for standardizing that (or even standards-compliance during your experiment), but more at an implementation technique to keep that information.

Of course, the answer depends entirely on the information we are missing. But assuming you are playing with the OpenWSN implementation, there is already an application called rrt which sends the ASN as application payload at the source, and records the ASN when the DAGroot has received that. You can then substract one by the other and do some stats. Please ask further questions to the OpenWSN community [1] as such technical discussion on a particular implementation doesn't belong on the 6TiSCH WG ML.

If you are using the commercial SmartMesh IP solution by Linear Tech [2], good news, all of that is already built in. The manager (~DAGroot) keeps track of timing and can send you average latencies for each of your nodes. If you're interested, you can look at these numbers "live" on deployments in Argentina [3,4] or California [5]. As you might imagine, latency/throughput/lifetime trade-off for one another, so there is a handy "performance estimator" tool you can use [6,7]. For further question on this topic, please use www.dustcloud.org <http://www.dustcloud.org> .

Finally, looking at lowering latency in 6TiSCH has been an important research topic in the last year or so. Look for example at the "Low-Latency Scheduling Function" [8] work which lowers the per-hop latency to 10's of ms withing the 6TiSCH framework.

Thomas

[1] www.openwsn.org <http://www.openwsn.org> 

[2] www.linear.com/dust <http://www.linear.com/dust> 

[3] http://www.savethepeaches.com/

[4] PEACH: Predicting Frost Events in Peach Orchards Using IoT Technology. Thomas Watteyne, Ana Laura Diedrichs, Keoma Brun-Laguna, Javier Emilio Chaar, Diego Dujovne, Juan Carlos Taffernaberry, Gustavo Mercado. EAI Endorsed Transactions on the Internet of Things, to appear in 2016.

[5] http://www.snowhow.io/

[6] http://www.linear.com/docs/42452

[7] Industrial IEEE802.15.4e Networks: Performance and Trade-offs. Thomas Watteyne, Joy Weiss, Lance Doherty, Jonathan Simon. IEEE International Conference on Communications (IEEE ICC), Internet of Things Symposium, London, UK, 8-12 June 2015.

[8] LLSF: Low Latency Scheduling Function for 6TiSCH Networks. Tengfei Chang, Thomas Watteyne, Qin Wang, Xavier Vilajosana.... IEEE International Conference on Distributed Computing in Sensor Systems (DCOSS), Washington, DC, USA, 26-28 May 2016.

On Thu, Aug 25, 2016 at 7:57 AM, Lijo Thomas <[email-masked] <mailto:[email-masked]> > wrote:

Hi all,

We are working on problem which needs the Time to Live (TTL) information in terms of ASN  to be included as part of the Packet.

We require the intermediate nodes to update TTL at each hop.

How this information can be passed in a 6tisch framework.

Suggestions are welcome..

Thanks & Regards

Lijo Thomas

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_______________________________________

Thomas Watteyne, PhD

Research Scientist & Innovator, Inria

Sr Networking Design Eng, Linear Tech

Founder & co-lead, UC Berkeley OpenWSN

Co-chair, IETF 6TiSCH

www.thomaswatteyne.com <http://www.thomaswatteyne.com> 

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