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

Loa Andersson <loa@pi.nu> Fri, 21 September 2018 10:44 UTC

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To: Greg Mirsky <gregimirsky@gmail.com>
Cc: Mach Chen <mach.chen@huawei.com>, DetNet WG <detnet@ietf.org>, János Farkas <Janos.Farkas@ericsson.com>, detnet-chairs@ietf.org, Stewart Bryant <stewart.bryant@gmail.com>, "Bocci, Matthew (Nokia - GB)" <matthew.bocci@nokia.com>
References: <F73A3CB31E8BE34FA1BBE3C8F0CB2AE29267092D@dggeml530-mbs.china.huawei.com> <CA+RyBmX29+Q9y3dXM-PqYm-Nu8KtjYZDs6a-fh_rW5hacSpyRg@mail.gmail.com> <F73A3CB31E8BE34FA1BBE3C8F0CB2AE292672CBB@dggeml530-mbs.china.huawei.com> <d4e45e7d-1001-be64-9ff0-f9ea9a882b77@pi.nu> <F73A3CB31E8BE34FA1BBE3C8F0CB2AE292673B40@dggeml530-mbs.china.huawei.com> <1e141c08-421a-3698-ac5f-02b597d978ea@pi.nu> <CA+RyBmWXMTN0N81QAAQ9jg9=5hKKe7kdrxGyCO8boBMBZfCUqQ@mail.gmail.com>
From: Loa Andersson <loa@pi.nu>
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Date: Fri, 21 Sep 2018 18:44:12 +0800
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Subject: Re: [Detnet] Regarding the model for Active OAM packet
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Greg,

On 2018-09-20 20:55, Greg Mirsky wrote:
> Hi Loa,
> I agree that we can define new ACH Type that will have Sequence Number 
> immediately following the ACH. 

OK!

    > But then we'll need to re-define number
> of Types, e.g., BFD, RFC 6374, etc. Or I misunderstood your suggestion.this probably 
> 
This probably the key, why do you need to redefine?

/Loa
> Regards,
> Greg
> 
> On Thu, Sep 20, 2018 at 3:13 AM Loa Andersson <loa@pi.nu 
> <mailto:loa@pi.nu>> wrote:
> 
>     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:detnet-bounces@ietf.org
>     <mailto:detnet-bounces@ietf.org>] On Behalf Of Loa Andersson
>      >> Sent: Thursday, September 20, 2018 3:21 PM
>      >> To: Mach Chen <mach.chen@huawei.com
>     <mailto:mach.chen@huawei.com>>; Greg Mirsky
>      >> <gregimirsky@gmail.com <mailto:gregimirsky@gmail.com>>
>      >> Cc: DetNet WG <detnet@ietf.org <mailto:detnet@ietf.org>>; János
>     Farkas
>      >> <Janos.Farkas@ericsson.com <mailto:Janos.Farkas@ericsson.com>>;
>     detnet-chairs@ietf.org <mailto:detnet-chairs@ietf.org>
>      >> 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:gregimirsky@gmail.com
>     <mailto:gregimirsky@gmail.com>]
>      >>> *Sent:* Wednesday, September 19, 2018 11:29 AM
>      >>> *To:* Mach Chen <mach.chen@huawei.com
>     <mailto:mach.chen@huawei.com>>
>      >>> *Cc:* János Farkas <Janos.Farkas@ericsson.com
>     <mailto:Janos.Farkas@ericsson.com>>; DetNet WG
>      >>> <detnet@ietf.org <mailto:detnet@ietf.org>>;
>     detnet-chairs@ietf.org <mailto:detnet-chairs@ietf.org>
>      >>> *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 <mach.chen@huawei.com
>     <mailto:mach.chen@huawei.com>
>      >>> <mailto:mach.chen@huawei.com <mailto:mach.chen@huawei.com>>> 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:detnet-bounces@ietf.org
>     <mailto:detnet-bounces@ietf.org> <mailto:detnet- <mailto:detnet->
>      >> bounces@ietf.org <mailto:bounces@ietf.org>>] On Behalf
>      >>>      Of Greg Mirsky
>      >>>      > Sent: Wednesday, September 19, 2018 3:17 AM
>      >>>      > To: János Farkas <Janos.Farkas@ericsson.com
>     <mailto:Janos.Farkas@ericsson.com>
>      >> <mailto:Janos.Farkas@ericsson.com
>     <mailto:Janos.Farkas@ericsson.com>>>
>      >>>      > Cc: DetNet WG <detnet@ietf.org <mailto:detnet@ietf.org>
>     <mailto:detnet@ietf.org <mailto:detnet@ietf.org>>>; detnet-
>      >> chairs@ietf.org <mailto:chairs@ietf.org>
>      >>>      <mailto:detnet-chairs@ietf.org
>     <mailto:detnet-chairs@ietf.org>>
>      >>>      > 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
>      >> <Janos.Farkas@ericsson.com <mailto:Janos.Farkas@ericsson.com>
>     <mailto:Janos.Farkas@ericsson.com <mailto:Janos.Farkas@ericsson.com>>>
>      >>>      > 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
>      >>>      > > detnet@ietf.org <mailto:detnet@ietf.org>
>     <mailto:detnet@ietf.org <mailto:detnet@ietf.org>>
>      >>>      > > https://www.ietf.org/mailman/listinfo/detnet
>      >>>      >
>      >>>      > _______________________________________________
>      >>>      > detnet mailing list
>      >>>      > detnet@ietf.org <mailto:detnet@ietf.org>
>     <mailto:detnet@ietf.org <mailto:detnet@ietf.org>>
>      >>>      > https://www.ietf.org/mailman/listinfo/detnet
>      >>>
>      >>>
>      >>>
>      >>> _______________________________________________
>      >>> detnet mailing list
>      >>> detnet@ietf.org <mailto:detnet@ietf.org>
>      >>> https://www.ietf.org/mailman/listinfo/detnet
>      >>>
>      >>
>      >> --
>      >>
>      >>
>      >> Loa Andersson                        email: loa@pi.nu
>     <mailto:loa@pi.nu>
>      >> Senior MPLS Expert
>      >> Bronze Dragon Consulting             phone: +46 739 81 21 64
>      >>
>      >> _______________________________________________
>      >> detnet mailing list
>      >> detnet@ietf.org <mailto:detnet@ietf.org>
>      >> https://www.ietf.org/mailman/listinfo/detnet
>      > _______________________________________________
>      > detnet mailing list
>      > detnet@ietf.org <mailto:detnet@ietf.org>
>      > https://www.ietf.org/mailman/listinfo/detnet
>      >
> 
>     -- 
> 
> 
>     Loa Andersson                        email: loa@pi.nu <mailto:loa@pi.nu>
>     Senior MPLS Expert
>     Bronze Dragon Consulting             phone: +46 739 81 21 64
> 

-- 


Loa Andersson                        email: loa@pi.nu
Senior MPLS Expert
Bronze Dragon Consulting             phone: +46 739 81 21 64