Re: [mpls] Notes on draft-jags-mpls-mna-hdr-04

[Tony Li <[e-mail]>]

Hi Greg,

>     0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>    |                 Label                 | TC  |S|      TTL      |
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>    |   Opcode    |        Data             |P|IHS|S|Res|U|O|  NASL |
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>    | Opcode = 3  |              NAI              |S|  Data |  NAL  |
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>    ~1|            Ancillary   Data               |S|Ancillary Data ~
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>    |1|            Ancillary   Data               |S|Ancillary Data |
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> 
> None, one or more Format C LSEs with Opcode 3 MAY be present in the same NAS.
> Each Format C LSE with the Opcode 3 MUST be followed by one or more Format D LSEs carrying associated Ancillary Data.


That’s correct.


> If my understaning is correct, I have some questions about the Ancillary Data encoding:
> Can an AD associated with the particular NAI span more than a single Format D LSE?


Yes, certainly.  AD length is only bounded by the NAL plus other actions within the same LSE.


> Can a single Format D LSE carry ADs of more than one NAI?


Good question.  We have required an action to specify the amount of AD that it needs, but we have not specified any kind of granularity. This could reasonably be in bits, octets, or LSEs. If it’s in bits or octets, we might need to talk about data alignment.  If it’s in LSEs, we will need to talk about efficiency.


> And I still need a help to answer How a node skips an AD associated with the unsupported NAI?


I think I addressed this in my previous reply.  Please let me know if that was unclear.

Regards,
Tony