Re: [Detnet-dp-dt] detnet LSPs and PWs

["Andrew G. Malis" <[e-mail]>]

On Mon, Feb 13, 2017 at 5:55 AM, Stewart Bryant <[e-mail]>
wrote:

> Now for the elephant in the corner of all of the schemes I have seen. If
> you have multiple paths to an X-PE, packets will likely arrive on different
> line cards. Sequence number co-ordination amongst different line cards, and
> at high speed even amongst different ports on the same line card is a hard
> problem. Indeed depending on the pipeline design on the line card, ANY
> sequence number processing can be hard. You could mitigate this (at the
> cost of availability) by requiring a common ingress port at any detnet
> X-PE. This would normally require an RSVP-TE or SR underlay.
>
I would like to second Stewart’s comment above. Back in the early days of
PWs, some vendors implemented PWs without a sequence number because they
couldn’t do sequence number processing across multiple parallel forwarding
engines even on the same physical port, as the forwarding engines didn’t
have common shared memory. Of course, their customers had to not use ECMP,
at least for those PWs. I think most vendors have gotten past that these
days, but you can never tell. But keep these possible limitations in mind
as you design Detnet.

Cheers,
Andy