Re: [Detnet] IPv6 encapsulation in dataplane doc

[Jouni <[e-mail]>]

>>>> * End systems cannot participate to DetNet service layer packet
>>>> elimination & duplication business. If they still do e.g. using DetNet
>>>> DstOpt that is separate from subnet/transport layer provided service.
>>> 
>>> True, end station participation in PREF wouldn't be possible in this
>>> simplified approach for IP, but the end stations *could* still
>>> participate in the equivalent function provided by a sub-net layer such
>>> as TSN. So end to end detnet traffic protection is not possible, but it
>>> doesn't mean it can't be provided by lower network layers.  The gain
>>> here is a simplified and unified IP solution and simplified host
>>> processing/support, albeit with a loss of one of the three end to end
>>> detnet service attributes.
>> 
>> Yes, that’s true (as I already clarified in my latest mail to Pascal).
>> 
> 
> yes.  It's good for all to remember that DetNet is just as much (if not
> more) about supporting explicit routes with congestion protection and
> latency control....

Indeed..

>>>> * Different subnet/transport layer segments in the DetNet domain are
>>>> likely to use their own sequencing and duplication & elimination
>>>> solutions. I am not sure how independent those will be e.g., is the
>>>> sequence numbering unified across or only per segment. The former is not
>>>> IMO easy and the latter easily reduces to single points between segments
>>>> to handle number book keeping properly.  
>>> 
>>> Agreed.  The question for the WG is this a reasonable compromise in
>>> order to in our *initial* solution defined by the WG.  -- Nothing says
>>> we can't come back and improve on this in the future, but it will allow
>>> us to get *something* useful defined with less complexity.
>> 
>> I would first specify the required steps that make IP as-is work within one subnet/transport layer segment. That should be an achievable goal with a limitation of e.g. a single interconnection point between subnet/transport layer segments of different types/solutions. 
>> 
> 
> sure. as long as one of the 'attached stations' can be a router.

Yes. That’s the plan at least from my side.

- Juoni


> 
>> After that look into solving multiple interconnection points.. and there the L4 path that Pascal mentioned or that IPv6 DetNet DstOpt of mine could be way forward.
>> 
> 
> yes, this would be good follow on work...
> 
> Cheers,
> Lou
>> - Jouni
>> 
>> 
>>> 
>>> 
>>>> 
>>>> Regardless the above I am keen to explore this alternative approach..
>>>> 
>>> 
>>> Great - look forward to hear the results!
>>> Lou
>>> 
>>>> 
>>>> -          Jouni
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> *From:* detnet [mailto:[e-mail]] *On Behalf Of *Lou Berger
>>>> *Sent:* Wednesday, February 7, 2018 17:00 PM
>>>> *To:* Pascal Thubert (pthubert) <[e-mail]>; [e-mail]
>>>> *Subject:* Re: [Detnet] IPv6 encapsulation in dataplane doc
>>>> 
>>>> 
>>>> 
>>>> Pascal/all,
>>>> 
>>>> At the last interim a proposal was made to simplify IP processing, at
>>>> least for the initial detnet solution, by leaving PREF to the
>>>> subnet/transport layers (i.e., TSN and MPLS) and providing DetNet flow
>>>> identification based on typical IP 5-tuple perhaps + dscp. This approach
>>>> has several benefits beyond simplification, notably it will work for
>>>> both ipv4 and IPv6, and doesn't require any modification to
>>>> encapsulation / formats.
>>>> 
>>>> It would be really valuable to get feedback from the whole working group
>>>> if this simplification is acceptable or has unacceptable limitations.
>>>> 
>>>> Lou
>>>> 
>>>> On February 7, 2018 8:28:02 AM "Pascal Thubert (pthubert)"
>>>> <[e-mail] <mailto:[e-mail]>> wrote:
>>>> 
>>>>   Dear all
>>>> 
>>>> 
>>>> 
>>>>   This is about the IPv6 encapsulation and more precisely
>>>> 
>>>> 
>>>> 
>>>>                           Therefore, if a DetNet-aware end system only
>>>> 
>>>>      inserted the DetNet Destination Option into the IPv6 but e.g., a
>>>> 
>>>>      DetNet Edge node is configured to enforce an explicit route for the
>>>> 
>>>>      IPv6 packet using a source routing header, then it has no other
>>>> 
>>>>      possibility than add an outer tunneling IPv6 header with required
>>>> 
>>>>      extension headers in it.  The processing of IPv6 packets in a DetNet
>>>> 
>>>>      Edge node is discussed further in Section 6.4.1
>>>>   <https://tools.ietf.org/html/draft-ietf-detnet-dp-sol-01#section-6.4.1>.
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>>   With the current spec, a source sends a DetNet packet as
>>>> 
>>>> 
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>>                       |                                 |
>>>> 
>>>>                       |           DetNet Flow           |
>>>> 
>>>>                       |             Payload             |
>>>> 
>>>>                       |                                 |
>>>> 
>>>>                       /---------------------------------\
>>>> 
>>>>                       H   Optional DetNet DstOpt Hdr    H
>>>> 
>>>>                       \---------------------------------/
>>>> 
>>>>                       |          IPv6 header            |
>>>> 
>>>>                       |     (with set Flow label)       |
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>> 
>>>> 
>>>>   And then the ingress node needs to re-encapsulate as
>>>> 
>>>> 
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>>                       |                                 |
>>>> 
>>>>                       |           DetNet Flow           |
>>>> 
>>>>                       |             Payload             |
>>>> 
>>>>                      |                                 |
>>>> 
>>>>                       /---------------------------------\
>>>> 
>>>>                       H        DetNet DstOpt Hdr        H
>>>> 
>>>>                       \---------------------------------/
>>>> 
>>>>                       |          IPv6 header            |
>>>> 
>>>>                       |     (with set Flow label)       |
>>>> 
>>>>                       +=================================+
>>>> 
>>>>                       |          Routing header         |
>>>> 
>>>>                       /---------------------------------\
>>>> 
>>>>                       H        DetNet DstOpt Hdr        H
>>>> 
>>>>                       \---------------------------------/
>>>> 
>>>>                       |          IPv6 header            |
>>>> 
>>>>                       |     (with set Flow label)       |
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>> 
>>>> 
>>>>   This creates a duplication of the DetNet Destination Option.
>>>> 
>>>> 
>>>> 
>>>>   There are alternatives
>>>> 
>>>> 
>>>> 
>>>>   a)  whereby the packet is tunneled from the source to the detnet
>>>>   ingress, and based on its state the DetNet ingress accepts the
>>>>   packet, processes it and then resends it. The tunneled version of
>>>>   this could be:
>>>> 
>>>> 
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>>                       |                                 |
>>>> 
>>>>                       |           DetNet Flow           |
>>>> 
>>>>                       |             Payload             |
>>>> 
>>>>                       |                                 |
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>>                       |          IPv6 header            |
>>>> 
>>>>                       |   (dest = final destination)    |
>>>> 
>>>>                       /=================================\
>>>> 
>>>>                       H   Optional DetNet DstOpt Hdr    H
>>>> 
>>>>                       \---------------------------------/
>>>> 
>>>>                       |          IPv6 header            |
>>>> 
>>>>                       |   (dest = DetNet ingress edge)  |
>>>> 
>>>>                       |     (with set Flow label)       |
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>> 
>>>> 
>>>>   Which allows the ingress to tunnel to the egress as follows:
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>>                       |                                 |
>>>> 
>>>>                       |           DetNet Flow           |
>>>> 
>>>>                       |             Payload             |
>>>> 
>>>>                       |                                 |
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>>                       |          IPv6 header            |
>>>> 
>>>>                       |      (to final destination)     |
>>>> 
>>>>                       +=================================+
>>>> 
>>>>                       |          Routing header         |
>>>> 
>>>>                       /---------------------------------\
>>>> 
>>>>                       H   Optional DetNet DstOpt Hdr    H
>>>> 
>>>>                       \---------------------------------/
>>>> 
>>>>                       |          IPv6 header            |
>>>> 
>>>>                       |   (dest = DetNet egress edge)   |
>>>> 
>>>>                       |     (with set Flow label)       |
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>>   b)  whereby the PREF is done by the end nodes and the tunnel is
>>>>   transport only, meaning that there are 2 tunnels A and B and that
>>>>   the source sends twice a packet like this:
>>>> 
>>>> 
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>>                       |                                 |
>>>> 
>>>>                       |           DetNet Flow           |
>>>> 
>>>>                       |             Payload             |
>>>> 
>>>>                       |                                 |
>>>> 
>>>>                       /---------------------------------\
>>>> 
>>>>                       H   Optional DetNet DstOpt Hdr    H
>>>> 
>>>>                       \---------------------------------/
>>>> 
>>>>                       |          IPv6 header            |
>>>> 
>>>>                       |   (dest = DetNet ingress edge X)|
>>>> 
>>>>                       |     (with set Flow label)       |
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>> 
>>>> 
>>>>   And then the ingress node needs to re-encapsulate as
>>>> 
>>>> 
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>>                       |                                 |
>>>> 
>>>>                       |           DetNet Flow           |
>>>> 
>>>>                       |             Payload             |
>>>> 
>>>>                      |                                 |
>>>> 
>>>>                       /---------------------------------\
>>>> 
>>>>                       H        DetNet DstOpt Hdr        H
>>>> 
>>>>                       \---------------------------------/
>>>> 
>>>>                       |          IPv6 header            |
>>>> 
>>>>                       |   (dest = final destination)    |
>>>> 
>>>>                       |     (with set Flow label)       |
>>>> 
>>>>                       +=================================+
>>>> 
>>>>                       |          Routing header         |
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>>                       |          IPv6 header            |
>>>> 
>>>>                       |   (dest = DetNet egress edge X) |
>>>> 
>>>>                       |     (with set Flow label)       |
>>>> 
>>>>                       +---------------------------------+
>>>> 
>>>> 
>>>> 
>>>>   Cheers,
>>>> 
>>>> 
>>>> 
>>>>   Pascal
>>>> 
>>>>   _______________________________________________
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>>>>   [e-mail] <mailto:detnet%40ietf.org>
>>>>   https://www.ietf.org/mailman/listinfo/detnet
>>>> 
>>> 
>> 
>> 
>