Re: [Detnet] IPv6 encapsulation in dataplane doc

[Lou Berger <[e-mail]>]

hi,

On 02/11/2018 03:06 PM, Jouni wrote:
> 
> Hi,
> 
> Inline..
> 
>> On 09 Feb 2018, at 18:23, Lou Berger <[e-mail]> wrote:
>>
>> Hi Jouni,
>>
>>
>> On 02/08/2018 04:08 AM, Jouni wrote:
>>> Hi,
>>>
>>>  
>>>
>>> Yes, we discussed this to an extent in the last call. I’ve been thinking
>>> this a bit more lately (cross country skiing conditions have been great
>>> thus you got a lot of time while on the skiing tracks ;) Few
>>> concerns/points to think I see here are:
>>
>> I'm jealous!
>>
>>>
>>> * 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....

> 
>>> * 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.

> 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
>>>
>>>    _______________________________________________
>>>    detnet mailing list
>>>    [e-mail] <mailto:detnet%40ietf.org>
>>>    https://www.ietf.org/mailman/listinfo/detnet
>>>
>>
> 
>