Re: [mpls] draft-kbbma-mpls-1stnibble

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

Robert,

Tell that to the folks that implemented heuristics-based ECMP back in the
day. Now we have to pick up the pieces.

Cheers,
Andy


On Tue, Apr 19, 2022 at 3:24 PM Robert Raszuk <[e-mail]> wrote:

> Andy,
>
> That nibble already breaks MPLS architecture regardless that it has been
> in use for a long time.
>
> There should be nothing MPLS related above S=1 in the packet.
>
> Cheers,
> R.
>
> On Tue, 19 Apr 2022 at 19:29, Andrew G. Malis <[e-mail]> wrote:
>
>> Robert,
>>
>> That's completely out of the scope of this draft. The point of this draft
>> is to document existing practice, create a new registry, and clarify the
>> best way to do load balancing based on the type of payload.
>>
>> The future stuff being discussed by the design team will be in a
>> different draft. THEN you can complain about breaking the MPLS
>> architecture! :-)
>>
>> Cheers,
>> Andy
>>
>>
>> On Tue, Apr 19, 2022 at 10:44 AM Robert Raszuk <[e-mail]> wrote:
>>
>>> Hi Andy,
>>>
>>> Yes I got this.
>>>
>>> But I am thinking about MNA. Where does PSD would sit in respect to the
>>> Figure 1 and Figure 2 ? Do you know ?
>>>
>>> Thx,
>>> R.
>>>
>>>
>>>
>>> On Tue, 19 Apr 2022 at 16:42, Andrew G. Malis <[e-mail]> wrote:
>>>
>>>> Robert,
>>>>
>>>> As shown in Figures 1 and 2, there is exactly one payload with a
>>>> post-stack header, but three types of post stack-payloads (and headers),
>>>> thus the use of the plural in the draft. To quote the text:
>>>>
>>>>    Figure 1 shows an MPLS packet with Layer 2 header X and a label stack
>>>>    Y ending with Label-n.  Figure 2 shows three examples of an MPLS
>>>>    payload, A, B and C.  The full MPLS packets thus are: [X, Y, A], [X,
>>>>    Y, B], and [X, Y, C].
>>>>
>>>> I hope this clears things up.
>>>>
>>>> Cheers,
>>>> Andy
>>>>
>>>>
>>>> On Tue, Apr 19, 2022 at 10:33 AM Robert Raszuk <[e-mail]>
>>>> wrote:
>>>>
>>>>> Hi Andy,
>>>>>
>>>>> I just understood from the text in the draft that the main objective
>>>>> to define those values in IANA is to allow more post stack headers ...
>>>>>
>>>>> ...
>>>>> First Nibble registry is to document the types of post-stack headers
>>>>>    that may follow a label stack, and to simplify their parsing.
>>>>>
>>>>> 2.2.  Why Create a Registry
>>>>>
>>>>>    The MPLS WG is currently engaged in updating the MPLS architecture;
>>>>>    part of this work involves the use of post-stack headers.
>>>>> ...
>>>>>
>>>>> Such post stack headers will likely sit between the nibble and payload
>>>>> - no ? And so far discussions about PSD insertion seems to be why this
>>>>> draft may have surfaced :)
>>>>>
>>>>> Best,
>>>>> R.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Tue, 19 Apr 2022 at 16:14, Andrew G. Malis <[e-mail]>
>>>>> wrote:
>>>>>
>>>>>> Robert,
>>>>>>
>>>>>> I think you're misreading the draft. The nibble under discussion is
>>>>>> the first nibble of the payload, such as zero for the control word, 4 or 6
>>>>>> for IP, etc. It IS the "PWE3 nibble" that you refer to in your email.
>>>>>>
>>>>>> Cheers,
>>>>>> Andy
>>>>>>
>>>>>>
>>>>>> On Tue, Apr 19, 2022 at 9:57 AM Robert Raszuk <[e-mail]>
>>>>>> wrote:
>>>>>>
>>>>>>> Hi Andy,
>>>>>>>
>>>>>>> Pseudowire emulation is a network layer in itself. Sure it is free
>>>>>>> to define its own nibble.
>>>>>>>
>>>>>>> Now we are talking about a new nibble between the last mpls label on
>>>>>>> the stack (S=1) and PWE3 nibble. Moreover that middle nibble will by
>>>>>>> definition be 1st one and will likely indicate the presence of a special
>>>>>>> container with additional instructions way before the PWE3 nibble sits.
>>>>>>>
>>>>>>> Are you game with this ? Actually the entire reason for RFC4385 just
>>>>>>> got smashed :) Not to mention any of the existing implementations which
>>>>>>> will not be new nibble aware and will be based on ethertype 8847 just parse
>>>>>>> it as today say for ECMP ...
>>>>>>>
>>>>>>> Best,
>>>>>>> R.
>>>>>>>
>>>>>>> On Tue, 19 Apr 2022 at 15:45, Andrew G. Malis <[e-mail]>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Robert,
>>>>>>>>
>>>>>>>> If this is the case, then how have we been using the Pseudowire
>>>>>>>> Control Word for the past 20 years or so? Nothing in this draft contradicts
>>>>>>>> what's been running in the field since the early days of the PWE3 working
>>>>>>>> group, and codified in RFC 4385.
>>>>>>>>
>>>>>>>> Cheers,
>>>>>>>> Andy
>>>>>>>>
>>>>>>>>
>>>>>>>> On Tue, Apr 19, 2022 at 8:03 AM Robert Raszuk <[e-mail]>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Dear WG,
>>>>>>>>>
>>>>>>>>> I would like to make the observation that
>>>>>>>>> the draft-kbbma-mpls-1stnibble departs from MPLS Label Stack encoding as
>>>>>>>>> defined in RFC3032 (ref section 2.2 of RFC3032).
>>>>>>>>>
>>>>>>>>> Post last label on the stack we are expecting Network Layer
>>>>>>>>> Protocol not some nibbles. This is no longer MPLSv1.
>>>>>>>>>
>>>>>>>>> If folks want to start defining nibbles and post stack data which
>>>>>>>>> is not a network layer they are welcome but let's call it what it is - new
>>>>>>>>> MPLS architecture and let's call it MPLSv2.
>>>>>>>>>
>>>>>>>>> Likely with new ethertype.
>>>>>>>>>
>>>>>>>>> Kind regards,
>>>>>>>>> Robert
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> mpls mailing list
>>>>>>>>> [e-mail]
>>>>>>>>> https://www.ietf.org/mailman/listinfo/mpls
>>>>>>>>>
>>>>>>>>