Re: I-D Action: draft-voyer-6man-extension-header-insertion-02.txt

[Tom Herbert <[e-mail]>]

On Sat, Dec 2, 2017 at 11:31 AM, Robert Raszuk <[e-mail]> wrote:
> Hi Tom,
>
>>
> Thanks for the detail Robert. Has there been any thought into using
>> the flow label to switch the packet over alternate paths? That might
>> be a zero overhead solution :-)
>
> The issue is not at the node doing the actual repair switching ... the issue
> is at the other nodes which must forward the packet to achieve loop free
> native forwarding.
>
Right, the idea is that at each node the input flow label and dst map
to an output flow label. All the flow label tables are constructed to
provide give loop free forwarding and multipath selection. Routers in
a domain need to participate (so a controlled domain is required), but
this does not change the on-the-wire format of packets. IIRC a single
depth label like this was proposed in some of the encapsulation
protocols for this same purpose.

> So if we use flow label for forwarding now each IPv6 router needs to do
> three lookups ... flow label + SRH + dst address or even 4 if you include
> src-dst forwarding.
>
SRH would be unneeded in this solution. Lookups would just be dst+flow
label. Encapsulation at ingress is probably still needed if nothing
else to be able to restore the flow label at domain egress.

Tom