Re: [Pals] [mpls] draft-zzhang-intarea-generic-delivery-functions

Greg Mirsky <gregimirsky@gmail.com> Tue, 23 February 2021 01:00 UTC

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From: Greg Mirsky <gregimirsky@gmail.com>
Date: Mon, 22 Feb 2021 17:00:27 -0800
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To: "Jeffrey (Zhaohui) Zhang" <zzhang@juniper.net>
Cc: Stewart Bryant <stewart.bryant@gmail.com>, Rakesh Gandhi <rgandhi.ietf@gmail.com>, "Yangfan (IP Standard" <shirley.yangfan@huawei.com>, mpls <mpls@ietf.org>, "int-area@ietf.org" <int-area@ietf.org>, Kireeti Kompella <kireeti@juniper.net>, Ron Bonica <rbonica@juniper.net>, "<rtg-ads@ietf.org>" <rtg-ads@ietf.org>, "pals@ietf.org" <pals@ietf.org>
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Subject: Re: [Pals] [mpls] draft-zzhang-intarea-generic-delivery-functions
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Hi Jeffrey,
I have read the draft and find it very interesting. I've got a question,
perhaps we can discuss:

   - if I understand it correctly, GDFH shim creates a new network layer.
   How you envision OAM at that layer can be identified? BIER uses protocol
   type. MPLS - GAL. IP - ICMP and, in UDP transport, well-known port numbers
   as the destination. Could it be assigned value from This Header registry?
   (Note, that This Header and Header Length appear swapped in Fig.2 compared
   to Fig.3 and Fig.4)

Regards,
Greg

On Mon, Feb 22, 2021 at 2:44 PM Jeffrey (Zhaohui) Zhang <zzhang@juniper.net>
wrote:

> Hi Stewart,
>
>
>
> GDF is for any transportations, MPLS being of the transportations.
>
> Here the question is, in case of MPLS, how do we do it.
>
>
>
> I did design it to advertise a GDF label so that we know that a GDFH is at
> BoS; and I make the GDFH start with 0000b so that it won’t be mistaken as
> an IP header.
>
>
>
> I don’t see why using 0000b in GDFH is contending with IOAM (even if it
> uses 0000b) and PW CW?
>
>
>
> I was incorrectly thinking that IOAM was using GAL, so I was thinking, if
> IOAM (which I think it is user traffic with OAM info embedded) could use
> GAL, then perhaps GAL’s restriction for user-traffic could be lifted, and
> in that case GDF go with G-ACH using GAL.
>
>
>
> Now I realize that I can’t really use GAL. In that case, I think it’s
> better to be independent of PW and G-ACH – this is not only the
> fragmentation function.
>
>
>
> Thanks.
> Jeffrey
>
>
>
> *From:* Stewart Bryant <stewart.bryant@gmail.com>
> *Sent:* Monday, February 22, 2021 5:39 AM
> *To:* Jeffrey (Zhaohui) Zhang <zzhang@juniper.net>
> *Cc:* Stewart Bryant <stewart.bryant@gmail.com>om>; Rakesh Gandhi <
> rgandhi.ietf@gmail.com>gt;; Yangfan (IP Standard <shirley.yangfan@huawei.com>om>;
> Greg Mirsky <gregimirsky@gmail.com>om>; mpls <mpls@ietf.org>rg>;
> int-area@ietf.org; Kireeti Kompella <kireeti@juniper.net>et>; Ron Bonica <
> rbonica@juniper.net>gt;; <rtg-ads@ietf.org> <rtg-ads@ietf.org>rg>; pals@ietf.org
> *Subject:* Re: [mpls] draft-zzhang-intarea-generic-delivery-functions
>
>
>
> *[External Email. Be cautious of content]*
>
>
>
> The way that a forwarder processing a PW  knows that a CW follows is
> because it is a parameter of the FEC of the PW label that is BoS.
>
>
>
> The CW then described whether the payload is a PW user payload of an ACH
> using the 0001
>
>
>
> IF you want to run OAM on an MPLS LSP as we do in MPLS-TP you have no CW
> so you need another method of indicating the presence of the ACH and the
> way that is done is with a GAL.
>
>
>
> The cleanest way to put fragmentation information at the BoS is to create
> a new type MPLS payload construct the “fragwire” if you like push the
> metadata, push a label advertised by the recipient that says that this is
> what is being done, then just the delivery label.
>
>
>
> You have to know that the target can do this, so the target can advertise
> or otherwise provide a label saying what it needs as an indicator.
>
>
>
> Job done and it is a private matter between sender and receiver.
>
>
>
> This is just reusing what is already in place today.
>
>
>
> Indeed if you make this a PW type, you only need a very short draft and it
> is all done.
>
>
>
> - Stewart
>
>
>
>
>
> On 19 Feb 2021, at 16:15, Jeffrey (Zhaohui) Zhang <zzhang@juniper.net>
> wrote:
>
>
>
> Hi Rakesh, Yangfan,
>
>
>
> I agree that a GDFH can follow the IOAM header and the two do not contend.
>
>
>
> It came to me though, the IOAM header could become a GDFH 😊 It can then
> be used for all transportations (MPLS, BIER, or even ethernet).
>
>
>
> I see that in your -06 version you treat IOAM as  a G-ACH channel. That
> does not seem to go well with the following in RFC 5586:
>
>
>
>    The G-ACh MUST NOT be used to transport user traffic.
>
>
>
> However I am not against relaxing the above restriction a bit.
>
> But I don’t understand why you need an “IOAM Indicator Label” – there is
> already a special label G-ACh Label (GAL).
>
> For GDFH, I had designed to advertise regular labels to indicate that a
> GDFH follows (I am always a good citizen when it comes to requesting
> special labels). Seeing that G-Ach uses the GAL, and the following:
>
>
>
>    The ACH used by CC Type 1 is depicted in figure below:
>
>
>
>     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          |
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>
>
>                     Figure 1: Associated Channel Header
>
>
>
> If the user traffic restriction could be lifted, it’s tempting to treat
> GDFH as a G-Ach channel type. That way we don’t need to advertise GDFH
> labels.
>
>
>
> To answer Yangfan’s question “what is the difference compared to G-AC” in
> another email: GDFH is for generic delivery function over different
> transports, and even when it is used over MPLS it is different from the
> (original intention of) G-ACH. However, as mentioned above, it’s tempting
> to treat GDFH as a channel type just to be able use the already assigned
> GAL.
>
>
>
> Thanks.
> Jeffrey
>
>
>
> *From:* Rakesh Gandhi <rgandhi.ietf@gmail.com>
> *Sent:* Thursday, February 18, 2021 6:49 PM
> *To:* Stewart Bryant <stewart.bryant@gmail.com>
> *Cc:* Jeffrey (Zhaohui) Zhang <zzhang@juniper.net>et>; mpls <mpls@ietf.org>rg>;
> int-area@ietf.org; Kireeti Kompella <kireeti@juniper.net>et>; Ron Bonica <
> rbonica@juniper.net>gt;; <rtg-ads@ietf.org> <rtg-ads@ietf.org>rg>; pals@ietf.org
> *Subject:* Re: [mpls] draft-zzhang-intarea-generic-delivery-functions
>
>
>
> *[External Email. Be cautious of content]*
>
>
>
> Hi Stewart,
>
> Hi Xiao, Loa,
>
> FYI:
>
> I believe the latest revision (06) addresses this comment. Welcome your
> feedback on that.
>
> https://datatracker.ietf.org/doc/html/draft-gandhi-mpls-ioam-sr-06
> <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/draft-gandhi-mpls-ioam-sr-06__;!!NEt6yMaO-gk!VXglGy7lcO2Pe-wXQDgZaYzzz0Ckq57ZSdkkJ0Sz5yTrNvCrxSb9ClooNfsG5fW-$>
>
>
>
> Thanks for your review.
>
> Regards,
>
> Rakesh
>
>
>
> On Tue, Jan 19, 2021 at 3:57 PM Rakesh Gandhi <rgandhi.ietf@gmail.com>
> wrote:
>
> Hi Stewart,
>
> Thanks for your comments. If we have a mechanism like following, does that
> address the issue?
>
>    1. IOAM header is part of the MPLS encapsulation, any other control
>    word is added after the IOAM header in the data packet.
>    2. The transit nodes can process the IOAM data field(s) after the EOS
>    in data packets as it is proposed.
>    3. The decapsulating node removes the MPLS encapsulation including the
>    IOAM header and then processes the other control word following it.
>
>    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
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    | IOAM Indicator Label                  | TC  |1|  TTL          |
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
>
>    |0 0 0 1|Version| Reserved      | IOAM G-ACh                    |  |
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  |
>
>    | Reserved      | Block Number  | IOAM-OPT-Type |IOAM HDR Length|  |
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  I
>
>    |                                                               |  O
>
>    |                                                               |  A
>
>    ~                 IOAM Option and Data Space                    ~  M
>
>    |                                                               |  |
>
>    |                                                               |  |
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
>
>    |0 0 0 0| Rsved | This Header   | Header Length | Next Header   |
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    ~              Variable field per “This header”                 ~
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    |                                                               |
>
>    |                                                               |
>
>    ~                 Payload Packet                                ~
>
>    |                                                               |
>
>    |                                                               |
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>
>
> Thanks,
>
> Rakesh
>
>
>
>
>
>
>
> On Tue, Jan 12, 2021 at 10:00 AM Stewart Bryant <stewart.bryant@gmail.com>
> wrote:
>
> Thank you Jeffery
>
> Please see the note that I sent about iOAM who also want to sit after BoS
> … and both of you want the same space that PALS and DetNet is already using.
>
> We plan to have a joint session on this hosted by PALS at the next IETF,
> but I think we also need to include the iOAM people.
>
> This has scope to get very messy as we find new candidates for BoS
> metadata so we really need to take a holistic position to ensure the future
> health the MPLS protocol.
>
> - Stewart
>
>
> > On 12 Jan 2021, at 14:27, Jeffrey (Zhaohui) Zhang <zzhang@juniper.net>
> wrote:
> >
> > Hi,
> >
> > I just posted
> https://datatracker.ietf.org/doc/draft-zzhang-intarea-generic-delivery-functions/
> <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/draft-zzhang-intarea-generic-delivery-functions/__;!!NEt6yMaO-gk!VXglGy7lcO2Pe-wXQDgZaYzzz0Ckq57ZSdkkJ0Sz5yTrNvCrxSb9ClooNQ3VcEYN$>
> .
> >
> > The initial version was posted to the tsvwg (
> https://tools.ietf.org/html/draft-zzhang-tsvwg-generic-transport-functions-00
> <https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-zzhang-tsvwg-generic-transport-functions-00__;!!NEt6yMaO-gk!VXglGy7lcO2Pe-wXQDgZaYzzz0Ckq57ZSdkkJ0Sz5yTrNvCrxSb9ClooNdw0REUd$>).
> After discussions/feedback we are re-homing it to intarea wg. This new
> version also contains quite some changes based on the comments and feedback
> that we received (special thanks to Stewart).
> >
> > Comments and suggestions are appreciated.
> >
> > Thanks.
> > Jeffrey
> >
> > Juniper Business Use Only
>
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