Re: [ippm] review comments on draft-mirsky-ippm-hybrid-two-step-05

[Greg Mirsky <[e-mail]>]

Hi Haoyu,
many thanks for your thorough review and detailed comments, much
appreciated. I'll respond with the proposed updates later this week.

Best regards,
Greg

On Thu, Oct 15, 2020 at 1:03 PM Haoyu Song <[e-mail]> wrote:

> Hi authors and IPPM,
>
>
>
> I reviewed the draft and see a close link of the proposed method with the
> other methods in discussion in the IPPMWG. Below are some questions and
> comments for your consideration.
>
>    1. I believe HTS has its place in the on-path telemetry branch of
>    technology. In essence, it sits just between IOAM and PBT: collect the
>    telemetry data using one dedicated and separate packet. The benefit of
>    doing so is clear and sound.
>    2. To best progress this work, I think a good strategy is to try to
>    align it with the existing specifications of IOAM Trace and IOAM DEX (e.g.,
>    data and header specification). It’s even possible to think about it as yet
>    another option for IOAM.
>    3. The nodes on the path need to maintain the states for each trigger
>    (the transport header and timer). This is not a  trivial process and the
>    scalability also needs to be considered.
>    4. How is the trigger implemented and how is the follow-up packet
>    header encapsulated? The current draft doesn’t provide enough details on
>    these issues.
>    5. The definition and usage of the sequence number is not very clear
>    to me. It seems to be used to differentiate the internal generated
>    follow-up packets. Based on the description, if a follow-up packet is
>    dropped, then each hop on the remaining path will experience the timer
>    expiration and generate a new follow-up packet. Will these packets all have
>    the same sequence number? If the original follow-up packet is just delayed
>    but not dropped, how will this and the other newly generated follow-up
>    packets are differentiated and processed?
>    6. The specification of the data profile is also missing. Isn't the
>    data profile should be carried by the trigger packet instead of the
>    follow-up packet?
>    7. The telemetry is encoded as TLV. How can the collector tell which
>    data is generated by which node?
>
> Please let me known if I missed or misunderstood anything. Thanks!
>
> Best regards,
>
> Haoyu
>