Re: [tsvwg] [tcmtf] M2M, WSNs and draft-saldana-tsvwg-tcmtf

["Jose Saldana" <[e-mail]>]

Another question: Brian talks about streaming over TCP (e.g. Youtube). This
is non-interactive traffic, since the client can do buffering an wait some
(short) time. But in addition, there are real-time interactive services
using TCP.

For example, World of Warcraft and almost every MMORPG game uses TCP. And
they are real-time interactive services: a player has to fight against other
players or against the "machine", and delay matters (every single player can
confirm this). Our research group has studied this issue, and also the
coexistence of real-time and best-effort TCP flows in a paper that is being
presented today in ICCCN Munchen: "The Effect of TCP Variants on the
Coexistence of MMORPG and Best-Effort Traffic"
(http://diec.unizar.es/~jsaldana/personal/hurry_NIME_2012_in_proc.pdf)

These games are becoming more and more popular. World of Warcraft has 10
million players. And gamers are really difficult clients to delay with. You
can have a look to this presentation (especially slide 5):
http://diec.unizar.es/~jsaldana/personal/sergei_SPECTS_2012_presentation.pdf

The only thing I want to remark with this e-mail is that TCP and best-effort
are not the same. It may sound weird, but real-time interactive TCP services
do exist, and they work every day with a lot of clients. We cannot forget
this when thinking about traffic classification.

Best regards and thank you for your feedback,

Jose

-----Mensaje original-----
De: [e-mail] [mailto:[e-mail]] En nombre de
Brian E Carpenter
Enviado el: lunes, 30 de julio de 2012 9:19
Para: [e-mail]
CC: [e-mail]; [e-mail]; [e-mail]; [e-mail]
Asunto: Re: [tcmtf] [tsvwg] M2M, WSNs and draft-saldana-tsvwg-tcmtf

On 30/07/2012 07:53, [e-mail] wrote:
> Folks,
> 
> avoiding a DSCP rewrite at domain boundarys is probably impossible - 
> there are many independent DiffServ deployments by now.
> 
> Al Morton will present some ITU work on the issue. We propose to apply 
> a small standardised set of domain behaviours (also called QoS 
> classes) at interconnection interfaces. The benefit is a domain 
> remarks tranmitted/received traffic to/from the interdomain DSCPs.

That assumes that you trust the diffserv markings applied by your peer. In
the general case, that seems unlikely, which is why there is always likely
to be a classifier as well as a re-marker at the boundary, and quite
possibly a traffic conditioner too.

Agreed, there might be a subset of peering relationships at which you would
be prepared to trust your neighbour's DSCPs. I thought that was one intent
behind RFC 4594 and its possible update.
We surely don't need *another* set of recommended traffic classes.

However, at a peering connection where you don't have that level of trust,
you have to either reclassify all packets or mark everything as best effort.

Every ISP needs to solve the interworking
> issue once only and should expect a reasonable end to end QoS.
> 
> The proposal more tries to look at DiffServ router forwarding knobs:
> a queuing mechanism and active queue management. My view is, these can 
> be optimised for an expected transport behaviour:
> 
> UDP traffic (streaming or telephony, real time gaming) will most 
> likely not be retransmitted. A short queue will do, active queue 
> management by random drops isn't required (unless you'd like to apply 
> PCN marking or the like).
> 
> TCP traffic interacts with router congestion indications, queues may 
> be a little bit deeper and active queue management may be deployed. 
> Today it is RED, ECN or the like in future.

How do you help the alarming amount of traffic that is streaming over TCP?

    Brian

> 
> If one looks at it from that angle, the number of useful QoS classes 
> is small.
> 
> Take the transport indication (TCP/UDP) as "dominating" in a class, 
> not a pureness requirement.
> 
> Regards
> 
> Ruediger
> 
> 
> 
> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On Behalf 
> Of Dan Wing
> Sent: Friday, July 27, 2012 6:27 PM
> To: 'Jose Saldana'
> Cc: [e-mail]; [e-mail]
> Subject: Re: [tsvwg] [tcmtf] M2M, WSNs and draft-saldana-tsvwg-tcmtf
> 
>> -----Original Message-----
>> From: Jose Saldana [mailto:[e-mail]]
>> Sent: Friday, July 27, 2012 4:14 AM
>> To: 'Dan Wing'
>> Cc: [e-mail]; [e-mail]
>> Subject: RE: [tcmtf] [tsvwg] M2M, WSNs and draft-saldana-tsvwg-tcmtf
>>
>> Well, perhaps a solution is the use of Diffserv bits: in the draft 
>> for updating rfc4594
>> (https://datatracker.ietf.org/doc/draft-polk-tsvwg-rfc4594-update)
>> there are
>> classes for real-time services and for best-effort ones. I have 
>> always believed that the update of rfc4594 can be beneficial for 
>> TCMTF: you can build a tunnel with flows belonging to the same 
>> traffic category.
>>
>> But I don't know if the best-effort class means exactly the same as 
>> delay-tolerant.
>>
>> Dan, what do you think?
> 
> I agree that DSCP is the best tool we have to combine packets with 
> similar characteristics.
> 
> A recurring problem with DSCP is they are re-written to different 
> values because a router was configured to rewrite them all the time or 
> because a queue of that traffic class had built.  That rewriting needs 
> to be considered (or ignored) when grouping packets that are 
> 'similar'.  IMO, the fact that a packet was in a queue a few router 
> hops away (and now has a different DSCP than its friends) doesn't 
> change that it should be grouped with all of its friends into a 
> multiplexing tunnel.
> 
> -d
> 
> 
>> Thanks,
>>
>> Jose
>>
>> -----Mensaje original-----
>> De: [e-mail] [mailto:[e-mail]] En nombre 
>> de Dan Wing Enviado el: viernes, 27 de julio de 2012 0:53
>> Para: 'Jose Saldana'
>> CC: [e-mail]
>> Asunto: Re: [tcmtf] [tsvwg] M2M, WSNs and draft-saldana-tsvwg-tcmtf
>>
>>> -----Original Message-----
>>> From: Jose Saldana [mailto:[e-mail]]
>>> Sent: Thursday, July 26, 2012 3:56 AM
>>> To: 'Dan Wing'
>>> Cc: [e-mail]
>>> Subject: RE: [tcmtf] [tsvwg] M2M, WSNs and draft-saldana-tsvwg-tcmtf
>>>
>>> Dan,
>>>
>>> I don't know if I have really understood your question. Of course, I 
>>> assume that a delay of some seconds is not important for certain 
>>> sensor networks.
>>> But they don't need to signal that they are delay tolerant. I mean, 
>>> they are assumed to be from the moment they are installed.
>> The device, doing the multiplexing, needs to know if the packets 
>> belong to a delay-tolerant (sensor) endpoint or to a non-delay 
>> tolerant endpoint.
>>
>> If the device doing the multiplexing is also the gateway 
>> communicating with the delay-tolerant (sensor) network, it certainly 
>> knows those
>> devices are delay-tolerant.   I believe that is your point.
>>
>> My point is that if the device doing the multiplexing is not directly 
>> connected to that network of delay-tolerant devices, it needs to 
>> somehow differentiate between the delay-tolerant devices and the non- 
>> delay- tolerant
>> -- by being signaled or by being configured.
>>
>> In the future, I expect a mix of sensors on various networks that are 
>> not traditional dedicated sensor networks (e.g., WiFi, 3G), so 
>> relying on a gateway to that dedicated network may not always be the 
>> way to know a device is delay tolerant.
>>
>> -d
>>
>>> Well, I think I should gather some information about typical 
>>> examples of sensor networks (number of sensors, frequency of 
>>> samples, packet size of the samples, etc), in order to calculate in 
>>> which cases the bandwidth saving obtained with TCMTF can be 
>>> interesting, and which "multiplexing period"
>>> should be used. I think that this could be a typical case in which 
>>> multiplexing can be done by packet size instead of using a period. I 
>>> mean, when you have almost 1500 bytes (or the MTU), you send a
>> packet.
>>> I don't know if I have answered your question,
>>>
>>> Jose
>>>
>>> -----Mensaje original-----
>>> De: Dan Wing [mailto:[e-mail]] Enviado el: martes, 24 de 
>>> julio de 2012 23:58
>>> Para: [e-mail]
>>> CC: [e-mail]; [e-mail]; [e-mail]
>>> Asunto: Re: [tcmtf] [tsvwg] M2M, WSNs and draft-saldana-tsvwg-tcmtf
>>>
>>> ...
>>>> Nevertheless, in order to get an idea of the savings, we should
>>> deploy
>>>> some calculations. Our research group has only done simulations for 
>>>> VoIP and games. In this case, we should know:
>>>>
>>>>
>>>>
>>>> -          Number of sensors in a typical scenario.
>>>>
>>>> -          Packet size and used headers. If IPv6 is used, savings
>>>>            can be really big, since header compression is really
>>>>            good for it.
>>>>
>>>> -          Packets per second that a single sensor can generate.
>>>>
>>>>
>>>>
>>>> And of course, the gateway should be the place for multiplexing.
>>>> In this case, the flows only travel from sensors to data center.
>>>> Am I right?
>>> I wonder if there is an easy way for the endpoints to signal that
>> they
>>> are delay tolerant (to allow collecting ~5 seconds of little
>> packets).
>>> -d
>>
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> 
> 
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