Re: [Detnet] IPv6 encapsulation in dataplane doc

[Lou Berger <[e-mail]>]

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]> 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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