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

[Loa Andersson <[e-mail]>]

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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>>>> https://www.ietf.org/mailman/listinfo/detnet
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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]