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

[Vijay Rangarajan <[e-mail]>]

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) <
[e-mail]> 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 <[e-mail]>
> *Sent:* Donnerstag, 22. August 2019 05:31
> *To:* Carlos Pignataro (cpignata) <[e-mail]>
> *Cc:* Jai Kumar <[e-mail]>;
> [e-mail]; IETF IPPM WG <[e-mail]>; Frank
> Brockners (fbrockne) <[e-mail]>; Hugh Holbrook <
> [e-mail]>; Anoop Ghanwani <[e-mail]>; OU, Heidi
> <[e-mail]>; Surendra Anubolu <
> [e-mail]>; John Lemon <[e-mail]>
> *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) <
> [e-mail]> 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 <[e-mail]>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 <[e-mail]> 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
>
>
>
>