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

[Mach Chen <[e-mail]>]

Hi Loa,

Please see my reply inline...

> -----Original Message-----
> From: Loa Andersson [mailto:[e-mail]]
> Sent: Friday, September 21, 2018 6:55 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,
> 
> 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??

The first nibble of the ACH field would be for that purpose. 

Best regards,
Mach
> 
> /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
> >>>>>>>        >
> >>>>>>>        > _______________________________________________
> >>>>>>>        > detnet mailing list
> >>>>>>>        > [e-mail] <mailto:[e-mail]>
> >>>>>>>        > https://www.ietf.org/mailman/listinfo/detnet
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> _______________________________________________
> >>>>>>> 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]
> >>>>>>
> >>>>>> _______________________________________________
> >>>>>> detnet mailing list
> >>>>>> [e-mail]
> >>>>>> https://www.ietf.org/mailman/listinfo/detnet
> >>>>> _______________________________________________
> >>>>> 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]
> >>
> >> --
> >>
> >>
> >> Loa Andersson                        email: [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]