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

[<[e-mail]>]

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. 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.

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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