Re: [Sidrops] Format of ASPA RTR PDU

[Maria Matejka <[e-mail]>]

Dear WG,

>>> On Tue, Nov 07, 2023 at 04:00:49PM +0100, Maria Matejka wrote:
>>>> While trying to implement ASPA in RTR, we got confused by § 5.12,
>>>> ASPA PDU, as of draft-ietf-sidrops-8210bis-11. Bytes 2 and 3 are
>>>> set to zero and bytes 10 and 11 are encoding Provider AS Count
>>>> which can be inferred from the overall PDU length easily. Is there
>>>> any good reason to have this redundant information inside the PDU?
>>>> We are suggesting to move the Flags and AFI Flags to bytes 2 and 3
>>>> and to drop Provider AS Count completely. The Customer ASN would
>>>> then start at byte 8 and Provider ASNs would start at byte 12.

returning to the ASPA RTR PDU format, I'm wishing to update the 5.12 
section as follows → we shall drop the AFI Flags (making them zero) and 
Provider AS Count (can be inferred from Length easily) and move the 
Flags to the byte 2.

Regarding all other parts of ASPA implementation in BIRD, it is 
basically prepared for merge and release, so we'd like to resolve this 
issue rather sooner than later, to avoid releasing breaking code changes.

Please see the updated parts below.

>
>       5.12.
>       <https://datatracker.ietf.org/doc/html/draft-ietf-sidrops-8210bis-11#section-5.12>ASPA
>       PDU
>       <https://datatracker.ietf.org/doc/html/draft-ietf-sidrops-8210bis-11#name-aspa-pdu>
>
>
> 0          8          16         24        31
> .-------------------------------------------.
> | Protocol |   PDU    |          |          |
> | Version  |   Type   |   Flags  |   zero   |
> |    2     |    11    |          |          |
> +-------------------------------------------+
> |                                           |
> |                 Length                    |
> |                                           |
> +-------------------------------------------+
> |                                           |
> |    Customer Autonomous System Number      |
> |                                           |
> +-------------------------------------------+
> |                                           |
> ~    Provider Autonomous System Numbers     ~
> |                                           |
> ~-------------------------------------------~
>
> (… 4 paragraphs skipped …)
>
> If the announce/withdraw flag is set to 0, it indicates removal of the 
> entire ASPA record for that Customer AS. Here, the customer AS of the 
> ASPA record MUST be provided. The Provider AS Numbers list MUST be 
> null and ignored by the router.
>
> The Customer Autonomous System Number is the 32-bit Autonomous System 
> Number of the customer which authenticated the ASPA RPKI data. There 
> MUST be one and only one ASPA for a Customer Autonomous System Number 
> active in the router at any time. There are zero or more 32-bit 
> Provider Autonomous System Number fields as indicated by the PDU 
> Length; see [I-D.ietf-sidrops-aspa-profile 
> <https://datatracker.ietf.org/doc/html/draft-ietf-sidrops-aspa-profile-16>].
>
Thank you for processing this.

-- 
Maria Matejka (she/her) | BIRD Team Leader | CZ.NIC, z.s.p.o.