Re: [ippm] Review on draft-ietf-ippm-ioam-data-06

Anoop Ghanwani <anoop@alumni.duke.edu> Tue, 03 September 2019 22:05 UTC

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From: Anoop Ghanwani <anoop@alumni.duke.edu>
Date: Tue, 3 Sep 2019 15:05:33 -0700
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To: "Frank Brockners (fbrockne)" <fbrockne@cisco.com>
Cc: "vijayr@arista.com" <vijayr@arista.com>, "draft-ietf-ippm-ioam-data@ietf.org" <draft-ietf-ippm-ioam-data@ietf.org>, IETF IPPM WG <ippm@ietf.org>, Hugh Holbrook <holbrook@arista.com>, "OU, Heidi" <heidi.ou@alibaba-inc.com>, Surendra Anubolu <surendra.anubolu@broadcom.com>, "bew.stds@gmail.com" <bew.stds@gmail.com>
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Subject: Re: [ippm] Review on draft-ietf-ippm-ioam-data-06
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Thanks Frank, this is helpful.  It appears the issue is still unresolved.

Anoop

On Mon, Sep 2, 2019 at 1:20 AM Frank Brockners (fbrockne) <
fbrockne@cisco.com> wrote:

> Hi Anoop,
>
>
>
> WRT/ the use of GRE encap: There was an earlier discussion among authors
> and interested parties which I’m attaching here.
>
> This discussion is also captured in the open issue #128:
> https://github.com/inband-oam/ietf/issues/128
>
>
>
> Frank
>
>
>
> *From:* Anoop Ghanwani <anoop@alumni.duke.edu>
> *Sent:* Samstag, 24. August 2019 00:02
> *To:* vijayr@arista.com
> *Cc:* Frank Brockners (fbrockne) <fbrockne@cisco.com>om>;
> draft-ietf-ippm-ioam-data@ietf.org; IETF IPPM WG <ippm@ietf.org>rg>; Hugh
> Holbrook <holbrook@arista.com>om>; OU, Heidi <heidi.ou@alibaba-inc.com>om>;
> Surendra Anubolu <surendra.anubolu@broadcom.com>
> *Subject:* Re: [ippm] Review on draft-ietf-ippm-ioam-data-06
>
>
>
> Hi Frank,
>
>
>
> As with Vijay, I am also interested in understanding the use of GRE for
> in-sequencing OAM.  Do we end up needing an Ethertype for TCP/UDP?
>
>
>
> Thanks,
>
> Anoop
>
>
>
> On Thu, Aug 22, 2019 at 10:06 AM Vijay Rangarajan <vijayr=
> 40arista.com@dmarc.ietf.org> wrote:
>
> Hi Frank:
>
> Thanks, I knew I was missing something.
>
> So basically what you are saying is - let's say we have a UDP packet, we
> are just going to stick in the GRE header and IOAM Header and Metadata
> in-between the original IP and UDP headers?
>
>
>
> So, the next protocol in the IOAM Header should indicate the L4 protocol -
> i.e UDP/TCP?
>
> Looking at https://datatracker.ietf.org/doc/draft-weis-ippm-ioam-eth/, it
> actually defines the "Next protocol" in the IOAM header to be an ethertype
> value?
>
>
>
> Thanks,
>
> Vijay
>
>
>
>
>
> On Thu, Aug 22, 2019 at 6:22 PM Frank Brockners (fbrockne) <
> fbrockne@cisco.com> wrote:
>
> Hi Vijay,
>
>
>
> note that you don’t necessarily need to “tunnel” – you can just use the
> GRE header to sequence-in IOAM.
>
>
>
> Cheers, Frank
>
>
>
> *From:* Vijay Rangarajan <vijayr@arista.com>
> *Sent:* Donnerstag, 22. August 2019 05:31
> *To:* Carlos Pignataro (cpignata) <cpignata@cisco.com
> <cpignata@cisco..com>>
> *Cc:* Jai Kumar <jai.kumar@broadcom.com>om>;
> draft-ietf-ippm-ioam-data@ietf.org; IETF IPPM WG <ippm@ietf.org>rg>; Frank
> Brockners (fbrockne) <fbrockne@cisco.com>om>; Hugh Holbrook <
> holbrook@arista.com>gt;; Anoop Ghanwani <Anoop.Ghanwani@dell.com>om>; OU, Heidi
> <heidi.ou@alibaba-inc..com <heidi.ou@alibaba-inc.com>>m>>; Surendra Anubolu <
> surendra.anubolu@broadcom.com>gt;; John Lemon <john.lemon@broadcom.com>
> *Subject:* Re: [ippm] Review on draft-ietf-ippm-ioam-data-06
>
>
>
> Thanks Carlos, for pointing me to the draft.
>
>
>
> Based on my understanding of the two drafts I have the following questions
> and concerns:
>
>    1. If I understand correctly, to deploy inband telemetry, we would
>    need to construct GRE tunnels coinciding with the IOAM domain?
>    2. GRE typically requires configuration to provision the tunnels.
>    Provisioning and managing these tunnels and keeping these updated as the
>    network grows/shrinks could be a significant overhead.
>    3. In order to get the benefit of telemetry, we are imposing a change
>    in forwarding protocol/topology and configuration - which, I feel is not
>    desirable. For example, a customer might have basic L3 routing enabled and
>    the expectation would be for inband telemetry to work seamlessly, without
>    having to revamp the network with GRE tunnels and such. This could be a
>    significant barrier to deployment.
>    4. If sampling is used to select packets for performing IOAM encap, is
>    the expectation that only sampled IOAM packets go through GRE encap? Or all
>    data packets?
>    5. Due to network nodes inserting the IOAM data, the inner L3/L4
>    headers keep getting pushed deeper. I would imagine this gets challenging
>    for ASICs to access these fields for hashing/load balancing.
>    6. Assuming only a subset of packets in a flow are subject to IOAM
>    (based on sampling), how do we ensure these packets take the same network
>    path as the rest of the packets in the flow?
>
> Thanks,
>
> Vijay
>
>
>
>
>
> On Wed, Aug 21, 2019 at 5:04 PM Carlos Pignataro (cpignata) <
> cpignata@cisco.com> wrote:
>
> Hello, Vijay,
>
>
>
> Please see https://datatracker.ietf.org/doc/draft-weis-ippm-ioam-eth/,
> and the document this replaces.
>
>
>
> Thanks!
>
> Thumb typed by Carlos Pignataro.
>
> Excuze typofraphicak errows
>
>
> 2019/08/21 6:35、Vijay Rangarajan <vijayr@arista.com>のメールt;のメール:
>
> Hello all:
>
> Apologise if this has been previously discussed.
>
> In reading "draft-ietf-ippm-ioam-data-06", I don't see mention of GRE
> encap. The draft, in fact in Sec 3, says the following - "The in-situ OAM
> data field can be transported by a variety of transport protocols,
> including NSH, Segment Routing, Geneve, IPv6, or IPv4.  Specification
> details for these different transport protocols are outside the scope of
> this document."
>
>
>
> Is there another document, or a description somewhere, that talks about
> how IOAM is proposed to be carried in GRE? what would be the GRE payload,
> the GRE protocol type etc?
>
>
>
> Thanks,
>
> Vijay
>
>
>
>
>
> On Wed, Aug 21, 2019 at 7:52 AM Jai Kumar <jai.kumar@broadcom.com> wrote:
>
> Hello Frank,
>
>
>
> This is in context of our conversation at IETF105. My goal is to provide
> input and improve current IOAM data draft with the learnings we had with
> IFA deployment.
>
> This feedback is based on various customer interactions and concerns
> raised by them wrt IOAM. Each feedback is a longer topic and I am starting
> this thread as a summary email. This is just highlighting the issues and
> not yet proposing any solution.
>
>
>
>
>
> Feedback 1:
>
> Section 4.2.1 Pre-allocated and Incremental Trace Options
>
> Pre-allocated and incremental trace option is 8Bytes long. This can be
> easily reduced to 4Bytes.
>
> There is a feedback that pre-allocated option is really not needed and
> either be removed or made optional.
>
> Given that deployments are sensitive to the IOAM overhead (specially in 5G
> deployments), it’s a 50% fixed overhead savings on a per packet basis.
>
>
>
>
>
> Feedback 2:
> Section 4.1 IOAM Namespaces
>
> Namespaces should be treated as templates (similar to IPFIX template
> record formats). This is more flexible way of enumerating data. 64K
> namespace id is a very large namespace and can be reduced to 64 IANA
> specified name spaces. Separate private name space can be allowed instead
> of interleaving of opaque data in the IANA allocated name space as
> suggested in the current draft “opaque state snapshot”.
>
> https://tools.ietf.org/html/rfc7011#section-3.4
>
>
>
> Feedback 3:
>
> Section 4.2.1 Pre-allocated and Incremental Trace Options
>
> IOAM-Trace-Type:  A 24-bit identifier which specifies which data
>
>       types are used in this node data list.
>
> This is the most contentious of all. In the current proposal, as new data
> fields are added, there is a corresponding trace type bit need in the
> header. This essentially means that all possible data fields need to be
> enumerated. Given that we there are 64K names spaces allowed, I don’t see
> how we can fit all possible data fields in this 24bit vector. I know there
> was a suggestion of keeping last bit as an extension bit but it is still
> scalable and/or easy to implement in hardware. Besides this the data fields
> are not annotated/encoded with the data type, something like in IPFIX
> https://tools.ietf.org/html/rfc7011#section-6.1
>
>
>
> Feedback 4:
>
> There is no version field in the data header and this will make
> interoperability challenging. Standard will evolve and headers bit
> definition and/or trace type will change and without version field HW will
> not be able to correctly handle the IOAM data headers.
>
>
>
> Feedback 5:
>
> Handling of TCP/UDP traffic using GRE encap is not acceptable. Here are
> some of the issues I can think of
>
>    - GRE encaped IOAM packets will traverse a different network path then
>    the original packet
>    - Not all packets can be GRE encaped to avoid the previous problem,
>    due to wastage of network bandwidth (typically sampled traffic is used for
>    IOAM). What about native GRE traffic, will it get further encaped in
>    another GRE tunnel and so forth.
>    - IP header protocol will point to GRE IP proto and IOAM ethertype
>    (pending allocation by IEEE) need to be read from the GRE header to detect
>    an IOAM packet. This means parsing performance penalty for all regular GRE
>    (non IOAM) traffic.
>
>
>
> Thanks,
>
> -Jai
>
>
>
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