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

"Carlos Pignataro (cpignata)" <cpignata@cisco.com> Sun, 25 August 2019 20:50 UTC

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From: "Carlos Pignataro (cpignata)" <cpignata@cisco.com>
To: Greg Mirsky <gregimirsky@gmail.com>
CC: Tom Herbert <tom@quantonium.net>, "OU, Heidi" <heidi.ou@alibaba-inc.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>, "Anoop Ghanwani" <Anoop.Ghanwani@dell.com>, Surendra Anubolu <surendra.anubolu@broadcom.com>
Thread-Topic: [ippm] Review on draft-ietf-ippm-ioam-data-06
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Subject: Re: [ippm] Review on draft-ietf-ippm-ioam-data-06
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> On Aug 22, 2019, at 7:41 PM, Greg Mirsky <gregimirsky@gmail.com> wrote:
> 
> Hi Tom,
> I think that the right solution to the problem of collecting telemetry
> information as experienced by a data packet is to disconnect origination of
> such information and transporting it. An iOAM packet may be used as a
> trigger to collect the required data on a node. But the same packet doesn't
> have to transport that information. That could be done either using
> Postcard-based
> Telemetry
> <https://datatracker.ietf.org/doc/draft-song-ippm-postcard-based-telemetry/>
> or Hybrid Two-Step
> <https://datatracker.ietf.org/doc/draft-mirsky-ippm-hybrid-two-step/>methods.
> In that case, IP options provide sufficient space to encode the profile of
> telemetry data to collect on a node.

It is not about the size of the option.

Please read, even using NOOP:
http://conferences.sigcomm.org/imc/2004/papers/p336-medina.pdf
https://www2.eecs.berkeley.edu/Pubs/TechRpts/2005/EECS-2005-24.html
http://www.employees.org/~dwing/ipoptions/

-- Carlos.

> 
> Regards,
> Greg
> 
> On Thu, Aug 22, 2019 at 12:34 PM Tom Herbert <tom@quantonium.net> wrote:
> 
>> On Thu, Aug 22, 2019 at 12:21 PM OU, Heidi <heidi.ou@alibaba-inc.com>
>> wrote:
>>> 
>>> Hi Frank,
>>> 
>>> 
>>> 
>>> I also have a question on the encapsulation: If you can get a new
>> ethertype for IOAM, why not insert IOAM data directly after layer2 MAC?
>> instead of adding a GRE header for IOAM.
>>> 
>> Because, we need a packet format that is compatible with existing
>> network devices. In light of that, GRE is more preferable than using
>> the new Ethertype directly in an Ethernet frame. There will also be
>> similar arguments made for using GRE/IP, and UDP encapsulation over
>> IP, and there was even a proposal to somehow insert the IOAM data
>> immediately after the TCP header and before the TCP data. All of these
>> are attempts to use protocol headers that are thought to be most
>> palatable to intermediate devices and maximize the chances of
>> efficient delivery.
>> 
>> IMO, all of the aforementioned techniques have some problem or aren't
>> clean (including the GRE solution). The best solution, and most
>> architecturally correct and generic one, is an IOAM option in
>> Hop-by-Hop extension headers.
>> 
>> Tom
>> 
>>> 
>>> 
>>> Thanks
>>> 
>>> Heidi
>>> 
>>> 
>>> 
>>> From: Vijay Rangarajan <vijayr@arista.com>
>>> Date: Thursday, August 22, 2019 at 7:22 AM
>>> To: "Frank Brockners (fbrockne)" <fbrockne@cisco.com>
>>> Cc: "Carlos Pignataro (cpignata)" <cpignata@cisco.com>om>, Jai Kumar <
>> jai.kumar@broadcom.com>gt;, "draft-ietf-ippm-ioam-data@ietf.org" <
>> draft-ietf-ippm-ioam-data@ietf.org>gt;, IETF IPPM WG <ippm@ietf.org>rg>, Hugh
>> Holbrook <holbrook@arista.com>om>, Anoop Ghanwani <Anoop.Ghanwani@dell.com>om>,
>> "OU, Heidi" <heidi.ou@alibaba-inc.com>om>, Surendra Anubolu <
>> surendra.anubolu@broadcom.com>gt;, John Lemon <john.lemon@broadcom.com>
>>> Subject: Re: [ippm] Review on draft-ietf-ippm-ioam-data-06
>>> 
>>> 
>>> 
>>> 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>
>>> 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>om>; 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:
>>> 
>>> If I understand correctly, to deploy inband telemetry, we would need to
>> construct GRE tunnels coinciding with the IOAM domain?
>>> 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.
>>> 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.
>>> 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?
>>> 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.
>>> 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)