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

Greg Mirsky <gregimirsky@gmail.com> Thu, 22 August 2019 23:41 UTC

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From: Greg Mirsky <gregimirsky@gmail.com>
Date: Thu, 22 Aug 2019 16:41:10 -0700
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To: Tom Herbert <tom@quantonium.net>
Cc: "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>
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Subject: Re: [ippm] Review on draft-ietf-ippm-ioam-data-06
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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.

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).
> 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
> >
> >
> >
> > _______________________________________________
> > ippm mailing list
> > ippm@ietf.org
> > https://www.ietf.org/mailman/listinfo/ippm
>
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