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Date:   Fri, 28 Aug 2020 14:20:53 +0530
From:   "S.V.R.Anand" <anandsvr@...c.ac.in>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: packet deadline and process scheduling

There is an active Internet draft "Packet Delivery Deadline time in
6LoWPAN Routing Header"
(https://datatracker.ietf.org/doc/draft-ietf-6lo-deadline-time/) which
is presently in the RFC Editor queue and is expected to become an RFC in
the near future. I happened to be one of the co-authors of this draft.
The main objective of the draft is to support time sensitive industrial
applications such as Industrial process control and automation over IP
networks.  While the current draft caters to 6LoWPAN networks, I would
assume that it can be extended to carry deadline information in other
encapsulations including IPv6. 

Once the packet reaches the destination at the network stack in the
kernel, it has to be passed on to the receiver application within the
deadline carried in the packet because it is the receiver application
running in user space is the eventual consumer of the data. My mail below is for
ensuring passing on the packet sitting in the socket interface to the
user receiver application process in a timely fashion with the help of
OS scheduler. Since the incoming packet experieces variable delay, the
remaining time left before deadline approaches too varies. There should
be a mechanism within the kernel, where network stack needs to
communicate with the OS scheduler by letting the scheduler know the
deadline before user application socket recv call is expected to return.

Anand


On 20-08-28 10:14:13, Eric Dumazet wrote:
> 
> 
> On 8/27/20 11:45 PM, S.V.R.Anand wrote:
> > Hi,
> >
> > In the control loop application I am trying to build, an incoming message from
> > the network will have a deadline before which it should be delivered to the
> > receiver process. This essentially calls for a way of scheduling this process
> > based on the deadline information contained in the message.
> >
> > If not already available, I wish to  write code for such run-time ordering of
> > processes in the earlist deadline first fashion. The assumption, however
> > futuristic it may be, is that deadline information is contained as part of the
> > packet header something like an inband-OAM.
> >
> > Your feedback on the above will be very helpful.
> >
> > Hope the above objective will be of general interest to netdev as well.
> >
> > My apologies if this is not the appropriate mailing list for posting this kind
> > of mails.
> >
> > Anand
> >
> 
> Is this described in some RFC ?
> 
> If not, I guess you might have to code this in user space.
> 
> 

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