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

Anoop Ghanwani <anoop@alumni.duke.edu> Fri, 23 August 2019 22:02 UTC

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From: Anoop Ghanwani <anoop@alumni.duke.edu>
Date: Fri, 23 Aug 2019 15:02:23 -0700
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To: vijayr@arista.com
Cc: "Frank Brockners (fbrockne)" <fbrockne@cisco.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>
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Subject: Re: [ippm] Review on draft-ietf-ippm-ioam-data-06
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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>om>; 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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