Re: [Detnet] Regarding the model for Active OAM packet

[Loa Andersson <[e-mail]>]

Mach,

inline please

On 2018-09-21 18:31, Mach Chen wrote:
> Hi Loa,
> 
> New ACH type is fine, this is also needed for DetNet OAM, IMHO.  The crucial here is how to "cheat" the replication/elimination nodes that an OAM packet is a "normal" DetNet packet, then they can replicate/eliminate the OAM packets as normal DetNet packets. Otherwise, it needs to introduce additional replication/elimination processing for the DetNet OAM packets.
> 
> To support this, I suggest to use ACH without GAL (of cause, a new ACH-type) for DetNet OAM (as bellow) and the "reserved" field  carries sequence number information, the "ACH" can be considered as the d-CW by the replication/elimination nodes.
> +----------+
> |S-Label  |
> +----------+
> |ACH        |
> +----------+
> | Payload|
> +----------+
>
what info do a node use to understand that the ACH is an ACH??

/Loa
> If GAL is used ( the stack as below), additional processing has to be introduced at the replication/elimination nodes, because they have to parse GAL+ACH to decide how to process. That means, the OAM packets will have different replication/elimination process from the normal DetNet packets.
> 
> +----------+
> |S-Label  |
> +----------+
> |GAL        |
> +----------+
> |ACH        |
> +----------+
> | Payload|
> +----------+
> 
> Best regards,
> Mach
> 
>> -----Original Message-----
>> From: Loa Andersson [mailto:[e-mail]]
>> Sent: Friday, September 21, 2018 4:49 PM
>> To: Mach Chen <[e-mail]>; Greg Mirsky
>> <[e-mail]>
>> Cc: DetNet WG <[e-mail]>; János Farkas
>> <[e-mail]>; [e-mail]
>> Subject: Re: [Detnet] Regarding the model for Active OAM packet
>>
>> Mach,
>>
>> Admittedly I'm not up to speed on DetNet OAM, but .....
>>
>> The ACH is specified like this:
>>
>>       0                   1                   2                   3
>>       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
>>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>      |0 0 0 1|Version|   Reserved    |         Channel Type          |
>>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>
>> you can define 65k ACH-types, what stops you from defining a ACH channel
>> type for DetNet OAM, then define that the structure of the following octets
>> in a way that you see fit (like (yes I'm inventing as I type, more thoughts
>> should go into to this):
>>
>>          0          1          2          3
>>          0123 45678901 234567890123 45678901
>>         +----+--------+------------+--------+
>>         | R  |   LEN  |     relevant info   |
>>         +----+--------+------------+--------+
>>         |0000|             d-CW             |
>>         +----+--------+------------+--------+
>>         |        more relevant info         |
>>         +----+--------+------------+--------+
>>
>>
>> What is that I'm missing?
>>
>> /Loa
>>
>> On 2018-09-21 14:22, Mach Chen wrote:
>>> Hi Loa,
>>>
>>> Can you clarify how a new ACH-type can address the problem?
>>>
>>> Best regards,
>>> Mach
>>>
>>>> -----Original Message-----
>>>> From: Loa Andersson [mailto:[e-mail]]
>>>> Sent: Thursday, September 20, 2018 6:14 PM
>>>> To: Mach Chen <[e-mail]>; Greg Mirsky
>>>> <[e-mail]>
>>>> Cc: DetNet WG <[e-mail]>; János Farkas
>>>> <[e-mail]>; [e-mail]
>>>> Subject: Re: [Detnet] Regarding the model for Active OAM packet
>>>>
>>>> Mach,
>>>>
>>>> I'd like Stewart or Matthew to look at this, but as I understand it
>>>> it is possible to define a new ACH-type that can do exactly what you want.
>>>>
>>>> /Loa
>>>>
>>>> On 2018-09-20 17:58, Mach Chen wrote:
>>>>> Loa,
>>>>>
>>>>> GAL is just an OAM indicator, the problem here is that when do
>>>>> DetNet
>>>> OAM, the d-CW will replaced by ACH or by GAL+ACH. No matter which
>> way
>>>> is used, to support the replication or elimination, there has to be a
>>>> sequence number filed. But ACH (as its current defined) does not have
>> such a field.
>>>>>
>>>>> My suggestion is to use the reserved field of ACH to carry sequence
>>>> number of OAM packet,  and for those replication or elimination
>>>> nodes, they do not have to differentiate whether a packet is OAM
>>>> packet or a normal packet, they could just treat the right 28 bits of
>>>> the ACH as the sequence number ( or treat the ACH as the d-CW), then
>>>> both OAM and replication/elimination can be supported.
>>>>>
>>>>> Best regards,
>>>>> Mach
>>>>>
>>>>>> -----Original Message-----
>>>>>> From: detnet [mailto:[e-mail]] On Behalf Of Loa
>>>>>> Andersson
>>>>>> Sent: Thursday, September 20, 2018 3:21 PM
>>>>>> To: Mach Chen <[e-mail]>; Greg Mirsky
>>>>>> <[e-mail]>
>>>>>> Cc: DetNet WG <[e-mail]>; János Farkas
>>>>>> <[e-mail]>; [e-mail]
>>>>>> Subject: Re: [Detnet] Regarding the model for Active OAM packet
>>>>>>
>>>>>> Mach,
>>>>>>
>>>>>> If I understand you correctly this is for an LSP in an MPLS
>>>>>> network, can you help me understand why GAL does not enough.
>> Given
>>>>>> that there might be some minor extensions to GAL because of
>>>>>> replication and
>>>> elimination.
>>>>>>
>>>>>> /Loa
>>>>>>
>>>>>> On 2018-09-19 14:31, Mach Chen wrote:
>>>>>>> Hi Greg,
>>>>>>>
>>>>>>> Indeed, there is no DetNet Associated Channel defined in
>>>>>>> draft-ietf-detnet-dp-sol-mpls for now, I think there should be.  I
>>>>>>> also assume that PW ACH will be used for DetNet OAM.
>>>>>>>
>>>>>>> Assume that PW ACH will be used for DetNet OAM and the reserved
>>>>>>> filed of the PW ACH will be used to carry sequence number for OAM
>>>> packet.
>>>>>>> But
>>>>>>>      for PREF, a tricky way is to treat the “Version”+ “Reserved” +
>>>>>>> ”Channel type” as the Sequence number, the replication or
>>>>>>> elimination nodes do not need to differentiate whether it is a
>>>>>>> d-CW or  a
>>>> PW ACH .
>>>>>>> This way, OAM can be supported without additional processing and
>>>> states.
>>>>>>>
>>>>>>>            0                   1                   2
>>>>>>> 3
>>>>>>>
>>>>>>>            0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7
>>>>>>> 8 9
>>>>>>> 0
>>>>>>> 1
>>>>>>>
>>>>>>>
>>>>>>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>>>
>>>>>>>           |0 0 0 1|Verion |    Reserved   |         Channel Type
>>>>>>> |
>>>>>>>
>>>>>>>
>>>>>>> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>>>
>>>>>>> Regarding sequence number, there are two ways to generate the
>>>>>> sequence
>>>>>>> number IMHO:  1) generated by the edge node, but it may need to
>>>>>>> configure the start number, or 2) copied from the application-flow
>>>>>>> (if there is). If the WG agree with this, the model can be updated
>>>>>>> reflect this.
>>>>>>>
>>>>>>> Best regards,
>>>>>>>
>>>>>>> Mach
>>>>>>>
>>>>>>> *From:*Greg Mirsky [mailto:[e-mail]]
>>>>>>> *Sent:* Wednesday, September 19, 2018 11:29 AM
>>>>>>> *To:* Mach Chen <[e-mail]>
>>>>>>> *Cc:* János Farkas <[e-mail]>; DetNet WG
>>>>>>> <[e-mail]>; [e-mail]
>>>>>>> *Subject:* Re: Regarding the model for Active OAM packet
>>>>>>>
>>>>>>> Hi Mach,
>>>>>>>
>>>>>>> thank you for your attention to my comment and the most expedient
>>>>>> response.
>>>>>>>
>>>>>>> I don't find the DetNet Associated Channel defined in
>>>>>>> draft-ietf-detnet-dp-sol-mpls and thus I assumed that OAM packets
>>>>>>> that follow the data packet encapsulation defined in that draft
>>>>>>> use PW ACH as defined in section 5 RFC 4385: True, it includes 8
>>>>>>> bits-long Reserved field that may be defined as OAM Sequence
>>>>>>> Number but that
>>>>>> had
>>>>>>> not been discussed. One is certain, existing nodes do not check
>>>>>>> the Reserved field. And without a field to hold the sequence
>>>>>>> number, PREF will not handle the OAM packets. Another question,
>>>>>>> additional processing and amount of state introduced in the fast
>>>>>>> path by the fact that OAM's Sequence Number will have different
>>>>>>> length and location in d-CW (differentiating cases by the first nibble).
>>>>>>>
>>>>>>> Now, if we step back from DetnNet in MPLS data plane
>>>>>>> encapsulation, why the control-word, as I understand, is
>>>>>>> configurable? I think that the Sequence Number is not
>>>>>>> configurable, nor the first nibble. What do you think?
>>>>>>>
>>>>>>> Regards,
>>>>>>>
>>>>>>> Greg
>>>>>>>
>>>>>>> On Tue, Sep 18, 2018 at 7:48 PM Mach Chen
>> <[e-mail]
>>>>>>> <mailto:[e-mail]>> wrote:
>>>>>>>
>>>>>>>        Hi Greg,
>>>>>>>
>>>>>>>        The MPLS DetNet header is defined as below:
>>>>>>>
>>>>>>>        grouping mpls-detnet-header {
>>>>>>>             description
>>>>>>>                 "The MPLS DetNet encapsulation header information.";
>>>>>>>             leaf service-label {
>>>>>>>               type uint32;
>>>>>>>               mandatory true;
>>>>>>>               description
>>>>>>>                 "The service label of the DetNet header.";
>>>>>>>             }
>>>>>>>             leaf control-word {
>>>>>>>               type uint32;
>>>>>>>               mandatory true;
>>>>>>>               description
>>>>>>>                 "The control word of the DetNet header.";
>>>>>>>             }
>>>>>>>           }
>>>>>>>
>>>>>>>        Although do not consider Active OAM when design the above
>>>>>>>        mpls-denet-header,  seems that it can cover Active OAM case as
>> well.
>>>>>>>        No matter a normal DetNet packet or an Active OAM packet, there
>>>>>>>        should be a CW field, just as defined above.
>>>>>>>
>>>>>>>        For normal DetNet packets, the CW is the d-CW as defined in the
>>>>>>>        draft-ietf-detnet-dp-sol-mpls.
>>>>>>>
>>>>>>>        For OAM packets, the CW is the "DetNet Associated Channel".
>>>>>>>
>>>>>>>        Best regards,
>>>>>>>        Mach
>>>>>>>
>>>>>>>
>>>>>>>        > -----Original Message-----
>>>>>>>        > From: detnet [mailto:[e-mail]
>>>>>>> <mailto:detnet-
>>>>>> [e-mail]>] On Behalf
>>>>>>>        Of Greg Mirsky
>>>>>>>        > Sent: Wednesday, September 19, 2018 3:17 AM
>>>>>>>        > To: János Farkas <[e-mail]
>>>>>> <mailto:[e-mail]>>
>>>>>>>        > Cc: DetNet WG <[e-mail] <mailto:[e-mail]>>;
>>>>>>> detnet-
>>>>>> [e-mail]
>>>>>>>        <mailto:[e-mail]>
>>>>>>>        > Subject: Re: [Detnet] WG adoption poll
>>>>>>> draft-geng-detnet-conf-
>>>> yang
>>>>>>>        >
>>>>>>>        > Hi Janos, et. al,
>>>>>>>        > the mpls-detnet-header container is based on the solution
>>>> described in
>>>>>>>        > draft-ietf-detnet-dp-sol-mpls. Analysis of active SFC OAM
>>>>>>> in the
>>>>>> proposed
>>>>>>>        > MPLS data plane solution in draft-mirsky-detnet-oam points
>>>>>>> to the
>>>>>> potential
>>>>>>>        > problem as result the fact that OAM packet doesn't include
>>>>>>> d-CW. I
>>>>>> believe
>>>>>>>        > that this question should be discussed and, if we agree on
>>>>>>> the
>>>> problem
>>>>>>>        > statement, properly resolved. Until then, I do not support
>>>>>>> the adoption
>>>>>> of
>>>>>>>        > the model that may not be capable to support active OAM.
>>>>>>>        >
>>>>>>>        > Regards,
>>>>>>>        > Greg
>>>>>>>        > On Tue, Sep 18, 2018 at 12:03 PM Janos Farkas
>>>>>> <[e-mail] <mailto:[e-mail]>>
>>>>>>>        > wrote:
>>>>>>>        > >
>>>>>>>        > > Dear all,
>>>>>>>        > >
>>>>>>>        > > This is start of a two week poll on making
>>>>>>>        > > draft-geng-detnet-conf-yang-04 a working group document.
>>>>>>> Please
>>>>>> send
>>>>>>>        > > email to the list indicating "yes/support" or "no/do not
>>>> support".  If
>>>>>>>        > > indicating no, please state your reservations with the
>>>> document.  If
>>>>>>>        > > yes, please also feel free to provide comments you'd like to see
>>>>>>>        > > addressed once the document is a WG document.
>>>>>>>        > >
>>>>>>>        > > The poll ends Oct 3.
>>>>>>>        > >
>>>>>>>        > > Thanks,
>>>>>>>        > > János and Lou
>>>>>>>        > >
>>>>>>>        > > _______________________________________________
>>>>>>>        > > detnet mailing list
>>>>>>>        > > [e-mail] <mailto:[e-mail]>
>>>>>>>        > > https://www.ietf.org/mailman/listinfo/detnet
>>>>>>>        >
>>>>>>>        > _______________________________________________
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>>>>>>>
>>>>>>>
>>>>>>>
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>>>>>>>
>>>>>>
>>>>>> --
>>>>>>
>>>>>>
>>>>>> Loa Andersson                        email: [e-mail]
>>>>>> Senior MPLS Expert
>>>>>> Bronze Dragon Consulting             phone: [phone]
>>>>>>
>>>>>> _______________________________________________
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>>>>> _______________________________________________
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>>>>>
>>>>
>>>> --
>>>>
>>>>
>>>> Loa Andersson                        email: [e-mail]
>>>> Senior MPLS Expert
>>>> Bronze Dragon Consulting             phone: [phone]
>>
>> --
>>
>>
>> Loa Andersson                        email: [e-mail]
>> Senior MPLS Expert
>> Bronze Dragon Consulting             phone: [phone]
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-- 


Loa Andersson                        email: [e-mail]
Senior MPLS Expert
Bronze Dragon Consulting             phone: [phone]