Re: Limited Domains:

[Tom Herbert <[e-mail]>]

On Tue, Apr 13, 2021 at 9:18 AM Ahmed Abdelsalam (ahabdels)
<[e-mail]> wrote:
>
> Hi Nick,
> Please find my answers inline [AA]
>
> -----Original Message-----
> From: Nick Hilliard <[e-mail]>
> Date: Tuesday, 13 April 2021 at 11:58
> To: ahabdels <[e-mail]>
> Cc: Tom Herbert <[e-mail]>, Brian E Carpenter <[e-mail]>, "[e-mail]" <[e-mail]>, "[e-mail]" <[e-mail]>
> Subject: Re: Limited Domains:
>
>     Ahmed Abdelsalam (ahabdels) wrote on 13/04/2021 09:59:
>     > [AA] I don't think we need a new codepoint.
>     > The operator explicitly configures the routers under his
>     > administrative domain to support Structured Flow Label.
>
>     a codepoint is a marker to cause something to be interpreted in a
>     specific and different way.  Moving this flag to the configuration
>     domain is essentially admitting that the semantics of a codepoint are
>     necessary, except that it removes the possibility of having these
>     semantics interpreted automatically on a per-packet basis, and turns it
>     into a per-router or possibly per-interface flag.  This is an unusual
>     type of regression in terms of a protocol where so much work has been
>     put into auto-configuration, and where the syntactic mechanism has been
>     created for protocol extensions.
> [AA] This is a domain wide config applied to all nodes of the domain. So either you decide to do on all routers or not. It doesn’t on per packet treatment.
>
Ahmed,

So this is all or nothing then, replete with a so-called "flag day".
What is the protocol that guarantees that every router in the domain
is properly configured, that no one ever inadvertently brings up a
router without proper configuration? And if configuration fails, which
even in a moderately sized domain will inevitably happen at some
point, how will the user detect the issue and debug it?

Tom

>
>     As a separate issue, if a regular ip packet from the outside
>     accidentally enters into this administrative domain, how does a router
>     on the inside of the domain know not to attempt to interpret the flow
>     label as a SFL, as it could end up effectively parsing random junk?
>
> [AA] All packet coming from external interfaces will be encapsulated in outer IPv6 header as explained the in section 3. The outer IPv6 is what matters for forwarding inside the domain. If a packet from outside accidentally enters into this administrative domain, then that is a bigger problem than SFL.
>
>     Nick
>