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

[Loa Andersson <[e-mail]>]

Greg,

If ACH is self-identifying, why do we ever need the GAL?

/Loa

On 2018-09-21 23:23, Greg Mirsky wrote:
> Hi Loa,
> you've asked how a node identifies that the payload is ACH, not CW. As I 
> understand RFC 4385, it is by the value of the first nibble that follows 
> BoS label. ACH assigned value 0b0001, PW CW - 0b0000. 0b0100 defines 
> IPv4, and 0b0110 - IPv6.
> 
> Regards,
> Greg
> 
> On Fri, Sep 21, 2018 at 3:55 AM Loa Andersson <[e-mail] 
> <mailto:[e-mail]>> wrote:
> 
>     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] <mailto:[e-mail]>]
>      >> Sent: Friday, September 21, 2018 4:49 PM
>      >> To: Mach Chen <[e-mail]
>     <mailto:[e-mail]>>; Greg Mirsky
>      >> <[e-mail] <mailto:[e-mail]>>
>      >> Cc: DetNet WG <[e-mail] <mailto:[e-mail]>>; János
>     Farkas
>      >> <[e-mail] <mailto:[e-mail]>>;
>     [e-mail] <mailto:[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] <mailto:[e-mail]>]
>      >>>> Sent: Thursday, September 20, 2018 6:14 PM
>      >>>> To: Mach Chen <[e-mail]
>     <mailto:[e-mail]>>; Greg Mirsky
>      >>>> <[e-mail] <mailto:[e-mail]>>
>      >>>> Cc: DetNet WG <[e-mail] <mailto:[e-mail]>>;
>     János Farkas
>      >>>> <[e-mail]
>     <mailto:[e-mail]>>; [e-mail]
>     <mailto:[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]
>     <mailto:[e-mail]>] On Behalf Of Loa
>      >>>>>> Andersson
>      >>>>>> Sent: Thursday, September 20, 2018 3:21 PM
>      >>>>>> To: Mach Chen <[e-mail]
>     <mailto:[e-mail]>>; Greg Mirsky
>      >>>>>> <[e-mail] <mailto:[e-mail]>>
>      >>>>>> Cc: DetNet WG <[e-mail] <mailto:[e-mail]>>;
>     János Farkas
>      >>>>>> <[e-mail]
>     <mailto:[e-mail]>>; [e-mail]
>     <mailto:[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]
>     <mailto:[e-mail]>]
>      >>>>>>> *Sent:* Wednesday, September 19, 2018 11:29 AM
>      >>>>>>> *To:* Mach Chen <[e-mail]
>     <mailto:[e-mail]>>
>      >>>>>>> *Cc:* János Farkas <[e-mail]
>     <mailto:[e-mail]>>; DetNet WG
>      >>>>>>> <[e-mail] <mailto:[e-mail]>>;
>     [e-mail] <mailto:[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]>
>      >>>>>>> <mailto:[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:[e-mail]>
>      >>>>>>> <mailto:detnet- <mailto:detnet->
>      >>>>>> [e-mail] <mailto:[e-mail]>>] On Behalf
>      >>>>>>>        Of Greg Mirsky
>      >>>>>>>        > Sent: Wednesday, September 19, 2018 3:17 AM
>      >>>>>>>        > To: János Farkas <[e-mail]
>     <mailto:[e-mail]>
>      >>>>>> <mailto:[e-mail]
>     <mailto:Janos.Farkas@ericsson..com>>>
>      >>>>>>>        > Cc: DetNet WG <[e-mail]
>     <mailto:[e-mail]> <mailto:[e-mail]
>     <mailto:[e-mail]>>>;
>      >>>>>>> detnet-
>      >>>>>> [e-mail] <mailto:[e-mail]>
>      >>>>>>>        <mailto:[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]> <mailto:[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]>
>     <mailto:[e-mail] <mailto:[e-mail]>>
>      >>>>>>>        > > https://www.ietf.org/mailman/listinfo/detnet
>      >>>>>>>        >
>      >>>>>>>        > _______________________________________________
>      >>>>>>>        > detnet mailing list
>      >>>>>>>        > [e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>
>      >>>>>>>        > https://www.ietf.org/mailman/listinfo/detnet
>      >>>>>>>
>      >>>>>>>
>      >>>>>>>
>      >>>>>>> _______________________________________________
>      >>>>>>> detnet mailing list
>      >>>>>>> [e-mail] <mailto:[e-mail]>
>      >>>>>>> https://www.ietf.org/mailman/listinfo/detnet
>      >>>>>>>
>      >>>>>>
>      >>>>>> --
>      >>>>>>
>      >>>>>>
>      >>>>>> Loa Andersson                        email: [e-mail]
>     <mailto:[e-mail]>
>      >>>>>> Senior MPLS Expert
>      >>>>>> Bronze Dragon Consulting             phone: [phone]
>      >>>>>>
>      >>>>>> _______________________________________________
>      >>>>>> detnet mailing list
>      >>>>>> [e-mail] <mailto:[e-mail]>
>      >>>>>> https://www.ietf.org/mailman/listinfo/detnet
>      >>>>> _______________________________________________
>      >>>>> detnet mailing list
>      >>>>> [e-mail] <mailto:[e-mail]>
>      >>>>> https://www.ietf.org/mailman/listinfo/detnet
>      >>>>>
>      >>>>
>      >>>> --
>      >>>>
>      >>>>
>      >>>> Loa Andersson                        email: [e-mail]
>     <mailto:[e-mail]>
>      >>>> Senior MPLS Expert
>      >>>> Bronze Dragon Consulting             phone: [phone]
>      >>
>      >> --
>      >>
>      >>
>      >> Loa Andersson                        email: [e-mail]
>     <mailto:[e-mail]>
>      >> Senior MPLS Expert
>      >> Bronze Dragon Consulting             phone: [phone]
>      > _______________________________________________
>      > detnet mailing list
>      > [e-mail] <mailto:[e-mail]>
>      > https://www.ietf.org/mailman/listinfo/detnet
>      >
> 
>     -- 
> 
> 
>     Loa Andersson                        email: [e-mail] <mailto:[e-mail]>
>     Senior MPLS Expert
>     Bronze Dragon Consulting             phone: [phone]
> 
> 
> 
> _______________________________________________
> detnet mailing list
> [e-mail]
> https://www.ietf.org/mailman/listinfo/detnet
> 

-- 


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