Re: [nvo3] [ippm] [Int-area] encapsulation of IOAM data in various protocols - follow up from WG discussion in London

[Tom Herbert <[e-mail]>]

On Mon, Apr 16, 2018 at 6:31 AM, Tianran Zhou <[e-mail]> wrote:
> Hi Shwetha,
>
> You are talking about the outer encapsution. It is straight forward for the
> underlay to record by the header. But what about the overlay, i.e., inner
> encapsulation(e.g. geneve)? Without special configuration, intermediate node
> will not read the inner header, hence not be able to process IOAM.e

Hi Tianran,

I believe that is also not protocol conformant. Intermediate nodes
should not be processing transport layer data as this can lead to
misinterpretation and possibly silent data corruption.

For instance, Geneve is a UDP encapsulation protocol with assigned
port 6081. In order for an intermediate device to process the Geneve
encapsulation header it would need to look for packets with
destination port of 6081 since that is the only possible
discriminator. However, transport port numbers do not have global
meaning and hosts may use port numbers for other purposes (RFC7605
describes this). So a packet to port 6081 might be something other
than Geneve and may be misinterpreted. If a misinterpreted packet is
changed (like ippm data is written) then that would be systematic
silent data corruption.

As far as I know, hop-by-hop options is the only protocol confirming
mechanism that allows an intermediate note to change data of packet in
flight. Encpasulation is the only conforming mechanism that allows an
intermediate node to add data (like extension headers) to a packet in
flight.

Tom

> Maybe we are not synced by this overlay/underlay use case. :-)
>
> Tianran
>
>
>
> ________________________________
> Sent from WeLink
>
> 发件人： Shwetha Bhandari (shwethab)
> 收件人： Tianran Zhou<[e-mail]>;Frank Brockners
> (fbrockne)<[e-mail]>;Mickey
> Spiegel<[e-mail]>;Tom Herbert<[e-mail]>
> 抄送： NVO3<[e-mail]>;int-area<[e-mail]>;Service Function
> Chaining IETF list<[e-mail]>;IETF IPPM WG<[e-mail]>
> 主题： Re: [ippm] [Int-area] encapsulation of IOAM data in various protocols -
> follow up from WG discussion in London
> 时间： 2018-04-16 18:17:01
>
> Hi Tianran,
>
>> If I recall right, it is not written in the ioam data draft.
>
> Data draft is defining the data to be carried in IOAM in an encapsulation
> agnostic way, it does not specify how the encapsulation protocol is
> configured.
>
>
>
>> Yes, node by node configuration is an easy way.
>
> While it is, it does not have to be a node by node configuration. It can be
> part of the encapsulation definition.
>
> For e.g. If the encapsulation is IPv6 and if we define the data to be
> carried as HbH options, then based on the Option Type with highest order 2
> bits set to 00 then the v6 nodes that implement IOAM will process the option
> and others will skip over.
>
>
>
>
>
> Thanks,
>
> Shwetha
>
>
>
> From: ippm <[e-mail]> on behalf of Tianran Zhou
> <[e-mail]>
> Date: Monday, April 16, 2018 at 2:36 PM
> To: "Frank Brockners (fbrockne)" <[e-mail]>, Mickey Spiegel
> <[e-mail]>, Tom Herbert <[e-mail]>
> Cc: NVO3 <[e-mail]>, "[e-mail]" <[e-mail]>, Service
> Function Chaining IETF list <[e-mail]>, IETF IPPM WG <[e-mail]>
> Subject: Re: [ippm] [Int-area] encapsulation of IOAM data in various
> protocols - follow up from WG discussion in London
>
>
>
> Hi Frank,
>
>
>
> If I recall right, it is not written in the ioam data draft.
>
> Yes, node by node configuration is an easy way. In the
> draft-zhou-ippm-ioam-yang, we have the “protocol-type” to indicate the
> layering.
>
>    +--rw ioam
>
>       +--rw ioam-profiles
>
>          +--rw enabled?        boolean
>
>          +--rw ioam-profile* [profile-name]
>
>             +--rw profile-name                    string
>
>             +--rw filter
>
>             |  +--rw filter-type?   ioam-filter-type
>
>             |  +--rw acl-name?      -> /acl:acls/acl/name
>
>             +--rw protocol-type?                  ioam-protocol-type
>
>             +--rw incremental-tracing-profile {incremental-trace}?
>
>             |  ...
>
>             +--rw preallocated-tracing-profile {preallocated-trace}?
>
>             |  ...
>
>             +--rw pot-profile {proof-of-transit}?
>
>             |  ...
>
>             +--rw e2e-profile {edge-to-edge}?
>
>                ...
>
>
>
>
>
> Tianran
>
> From: Frank Brockners (fbrockne) [mailto:[e-mail]]
> Sent: Monday, April 16, 2018 4:51 PM
> To: Tianran Zhou <[e-mail]>; Mickey Spiegel
> <[e-mail]>; Tom Herbert <[e-mail]>
> Cc: NVO3 <[e-mail]>; [e-mail]; Service Function Chaining IETF
> list <[e-mail]>; IETF IPPM WG <[e-mail]>
> Subject: RE: [ippm] [Int-area] encapsulation of IOAM data in various
> protocols - follow up from WG discussion in London
>
>
>
> Hi Tianran,
>
>
>
> IOAM is a domain specific feature (see also draft-ietf-ippm-ioam-data-02
> sections 3 and 4), which allows an operator to control by means of
> configuration where and for which traffic IOAM data fields are
> added/updated/removed from the customer traffic. Using your example of
> Geneve over IPv6 – with IOAM data in both the Geneve and the IPv6 protocol,
> one would expect that the operator configures the endpoints of the Geneve
> tunnel to operate on the IOAM data in Geneve, and the IPv6 routers that the
> Geneve tunnel traverses to operate on the IOAM data in IPv6.
>
>
>
> Frank
>
>
>
> From: Tianran Zhou <[e-mail]>
> Sent: Montag, 16. April 2018 10:37
> To: Frank Brockners (fbrockne) <[e-mail]>; Mickey Spiegel
> <[e-mail]>; Tom Herbert <[e-mail]>
> Cc: NVO3 <[e-mail]>; [e-mail]; Service Function Chaining IETF
> list <[e-mail]>; IETF IPPM WG <[e-mail]>
> Subject: RE: [ippm] [Int-area] encapsulation of IOAM data in various
> protocols - follow up from WG discussion in London
>
>
>
> Hi Frank,
>
>
>
> How does a forwarder know when and where to insert the data?
>
> In the case of Geneve over IPv6, do you mean the device need to scan all the
> protocol stack? Or just the outer encapsulation?
>
>
>
> Tianran
>
>
>
> From: ippm [mailto:[e-mail]] On Behalf Of Frank Brockners
> (fbrockne)
> Sent: Monday, April 16, 2018 3:08 PM
> To: Mickey Spiegel <[e-mail]>; Tom Herbert
> <[e-mail]>
> Cc: NVO3 <[e-mail]>; [e-mail]; Service Function Chaining IETF
> list <[e-mail]>; IETF IPPM WG <[e-mail]>
> Subject: Re: [ippm] [Int-area] encapsulation of IOAM data in various
> protocols - follow up from WG discussion in London
>
>
>
>
>
> Tom,
>
>
>
> a quick addition to what Mickey mentioned below: What you seem to have in
> mind is what draft-ietf-ippm-ioam-data-02 refers to as “layering” (see
> section 3.), i.e. if you’re running for example Geneve over IPv6, then IOAM
> data could be encapsulated in both protocols, Geneve and IPv6 – giving you
> visibility into the “underlay” (IPv6) and the “overlay” (Geneve).
>
>
>
> Frank
>
>
>
> From: ippm <[e-mail]> On Behalf Of Mickey Spiegel
> Sent: Freitag, 13. April 2018 20:22
> To: Tom Herbert <[e-mail]>
> Cc: NVO3 <[e-mail]>; [e-mail]; Service Function Chaining IETF
> list <[e-mail]>; IETF IPPM WG <[e-mail]>
> Subject: Re: [ippm] [Int-area] encapsulation of IOAM data in various
> protocols - follow up from WG discussion in London
>
>
>
> Tom,
>
>
>
> On Thu, Apr 12, 2018 at 10:17 PM, Tom Herbert <[e-mail]> wrote:
>
> Mickey,
>
> Looking at these ippm drafts more closely, I have a much more
> fundamental concern.
>
> In draft-brockners-ippm-ioam-geneve-00 for instance, there is the text
> in the introduction:
>
> "In-situ OAM (IOAM) records OAM information within the packet while
> the packet traverses a particular network domain.  The term "in-situ"
> refers to the fact that the IOAM data fields are added to the data
> packets rather than is being sent within packets specifically
> dedicated to OAM.  This document defines how IOAM data fields are
> transported as part of the Geneve [I-D.ietf-nvo3-geneve]
> encapsulation."
>
> I assume this means that as packets with Geneve encapsulation traverse
> the network they are interpreted by intermediate nodes as being
> Geneve. Since Geneve is a UDP encapsulation, then the destination UDP
> port number would be used to identify packets as being Geneve. So an
> intermediate device might be looking for UDP packets destined to port
> 6081 (the assigned UDP port for Geneve). If my understanding is
> correct, then this is a problem.
>
> UDP port numbers do not have global meaning. An intermediate device
> may very well see UDP packets destined to port 6081 that are not
> actually Geneve. This scenario is discussed in RFC7605:
>
> "...intermediate device interprets traffic based on the port number.
> It is important to recognize that any interpretation of port numbers
> -- except at the endpoints -- may be incorrect, because port numbers
> are meaningful only at the endpoints."
>
> If the UDP data is modified, as the draft would imply, then
> misinterpretation may also mean silent data corruption of packets. A
> protocol that would allow this seems pretty incorrect! Note that this
> would be true also for any UDP encapsulation that the network tries to
> interpret.
>
>
>
> The intention is to allow for multiple nodes that a packet traverses
>
> to be able to insert IOAM node information in the same trace option,
>
> but leave some flexibility regarding which nodes actually do the
>
> IOAM processing and the node information. This may vary
>
> depending on the transport.
>
>
>
> In case of a tunneled encapsulation such as Geneve or VXLAN,
>
> there may still be multiple hops. For example a network may use
>
> Geneve or VXLAN, but only do L2 processing at ToRs, with L3
>
> processing done at aggregation or core switches. In this case
>
> many packets would do 2 Geneve or VXLAN hops, so the packet
>
> would contain IOAM node information from two nodes.
>
>
>
> Another example is service function chaining using Geneve or
>
> VXLAN rather than NSH.
>
>
>
>
> I am also wondering if hop-by-hop options been considered for this
> application? Their interpretation in the network is unabiguous and
> they also have the advantage that the work with any IP protocol or
> encapsulation.
>
>
>
> IPv6 hop-by-hop options has been considered. See
>
> draft-brockners-inband-oam-transport-05. This has not yet been
>
> broken out into a separate draft.
>
>
>
> Mickey
>
>
>
>
> Thanks,
> Tom
>
>
> On Thu, Apr 12, 2018 at 3:31 PM, Mickey Spiegel
> <[e-mail]> wrote:
>
>> Tom,
>>
>> On Thu, Apr 12, 2018 at 2:46 PM, Tom Herbert <[e-mail]> wrote:
>>>
>>> On Thu, Apr 12, 2018 at 9:54 AM, Greg Mirsky <[e-mail]>
>>> wrote:
>>> > Hi Frank,
>>> > thank you for sharing your points. Please find my notes in-line and
>>> > tagged
>>> > GIM>>. I believe that this is very much relevant to work of other
>>> > working
>>> > groups that directly work on the overlay encapsulations in the center
>>> > of
>>> > the
>>> > discussion and hence I've added them to the list. Hope we'll have more
>>> > opinions to reach the conclusion that is acceptable to all.
>>> >
>>> > Regards,
>>> > Greg
>>> >
>>> > On Wed, Apr 11, 2018 at 12:02 PM, Frank Brockners (fbrockne)
>>> > <[e-mail]> wrote:
>>> >>
>>> >> Back at the IPPM meeting in London, we discussed several drafts
>>> >> dealing
>>> >> with the encapsulation of IOAM data in various protocols
>>> >> (draft-brockners-ippm-ioam-vxlan-gpe-00,
>>> >> draft-brockners-ippm-ioam-geneve-00, draft-weis-ippm-ioam-gre-00). One
>>> >> discussion topic that we decided to take to the list was the question
>>> >> on
>>> >> whether draft-ooamdt-rtgwg-ooam-header could be leveraged..  After
>>> >> carefully
>>> >> considering draft-ooamdt-rtgwg-ooam-header, I came to the conclusion
>>> >> that
>>> >> the “OOAM header” does not meet the needs of IOAM:
>>> >>
>>> >> * Efficiency: IOAM adds data to live user traffic. As such, an
>>> >> encapsulation needs to be as efficient as possible. The “OOAM header”
>>> >> is 8
>>> >> bytes long. The approach for IOAM data encapsulation in the above
>>> >> mentioned
>>> >> drafts only requires 4 bytes. Using the OOAM header approach would add
>>> >> an
>>> >> unnecessary overhead of 4 bytes – which is significant.
>>> Greg,
>>>
>>> I'm missing something here. I looked at the drafts you referenced and
>>> each of them looks like the overhead for OAM is greater that four
>>> bytes. In each there is some overhead equivalent to type/length, for
>>> instance in Geneve four bytes are needed for option class, type, and
>>> length. Unless the the OAM data is zero length, I don't see how this
>>> adds up to only four bytes of overhead.
>>
>>
>> The four versus eight bytes just refers to the fields in the four bytes of
>> IOAM
>> info, that is common to all IOAM options. Beyond that, there are IOAM
>> option
>> specific fields. For example if doing one of the IOAM trace options, there
>> are
>> four bytes of trace option header, including the IOAM-trace-type, NodeLen,
>> Flags, and RemainingLen fields. These are followed by the node data list
>> containing the per hop IOAM information.
>>
>> In looking at the OOAM header content, it has nothing to do with any of
>> the
>> IOAM information after the first four bytes. It contains another variant
>> of
>> the
>> information in the first four bytes of IOAM info, spread out over eight
>> bytes.
>>
>>>
>>> Tom
>>>
>>> >
>>> > GIM>> The difference in four octets is because OOAM Header:
>>> >
>>> > provides more flexibility, e.g. Flags field and Reserved fields;
>>
>>
>> The flags field only has one defined flag at the moment, for a timestamp
>> block. For IOAM trace we need per hop timestamps, which the timestamp
>> block cannot address, i.e. the timestamp block is redundant for IOAM.
>>
>>>
>>> > supports larger OAM packets than iOAM header;
>>
>>
>> For IOAM purposes, 1020 octets is more than enough.
>>
>>>
>>> > is future proof by supporting versioning (Version field).
>>
>>
>> IMO, taking the first two bits of the IOAM-Type to define a Version field
>> would be a good thing. This does not require adding four more bytes of
>> overhead. 64 IOAM-Types is more than enough.
>>
>>>
>>> >>
>>> >> * Maturity: IOAM has several implementations, which were also shown at
>>> >> recent IETF hackathons – and we’re expecting additional
>>> >> implementations
>>> >> to
>>> >> be publicized soon. Interoperable implementations need timely
>>> >> specifications. Despite the question being asked, the recent thread on
>>> >> OOAM
>>> >> in the NVO3 list hasn’t revealed any implementation of the OOAM
>>> >> header.
>>> >> In
>>> >> addition, the thread revealed that several fundamental questions about
>>> >> the
>>> >> OOAM header are still open, such as whether or how active OAM
>>> >> mechanisms
>>> >> within protocols such as Geneve would apply to the OOAM header. This
>>> >> ultimately means that we won’t get to a timely specification.
>>> >
>>> > GIM>> May I ask which encapsulations supported by the implementations
>>> > you
>>> > refer to. Until very recently all iOAM proposals were to use meta-data
>>> > TLV
>>> > in, e.g. Geneve and NSH. And if these or some of these implementations
>>> > already updated to the newly proposed iOAM shim, I don't see problem in
>>> > making them use OOAM Header. Would you agree?
>>> >
>>> >>
>>> >> * Scope: It isn’t entirely clear to which protocols the OOAM header
>>> >> would
>>> >> ultimately apply to. The way the OOAM header is defined, OOAM uses a
>>> >> 8-bit
>>> >> field for “Next Prot”, the next protocol. Some protocols that IOAM
>>> >> data
>>> >> needs to be encapsulated into use 16-bits for their next protocol code
>>> >> points. See e.g. the GRE encapsulation – as specified in
>>> >> draft-weis-ippm-ioam-gre-00.
>>> >
>>> > GIM>> The first paragraph of the Introduction section states:
>>> >    New protocols that support overlay networks like VxLAN-GPE
>>> >    [I-D.ietf-nvo3-vxlan-gpe], GUE [I-D.ietf-nvo3-gue], Geneve
>>> >    [I-D.ietf-nvo3-geneve], BIER [I-D.ietf-bier-mpls-encapsulation], and
>>> >    NSH [I-D.ietf-sfc-nsh] support multi-protocol payload, e.g.
>>> >    Ethernet, IPv4/IPv6, and recognize Operations, Administration, and
>>> >    Maintenance (OAM) as one of distinct types.  That ensures that
>>> >    Overlay OAM (OOAM)packets are sharing fate with Overlay data packet
>>> >    traversing the underlay.
>>> > I'm updating the OOAM Header draft and along with cleaning nits will
>>> > update
>>> > reference to GUE. I think that the list and the statemnt are quite
>>> > clear
>>> > in
>>> > identifying the scope of networks that may benefit from using not only
>>> > common OOAM Header but common OOAM mechanisms, e.g. Echo Request/Reply.
>>> >
>>> >> With the above in mind, I’d suggest that the WG moves forward with
>>> >> specific definitions for encapsulating IOAM data into protocols – per
>>> >> the
>>> >> above mentioned drafts.
>>> >>
>>> >>
>>> >>
>>> >> Regards, Frank
>>> >>
>>> >>
>>> >> _______________________________________________
>>> >> ippm mailing list
>>> >> [e-mail]
>>> >> https://www.ietf.org/mailman/listinfo/ippm
>>> >>
>>> >
>>> >
>>> > _______________________________________________
>>> > Int-area mailing list
>>> > [e-mail]
>>> > https://www.ietf.org/mailman/listinfo/int-area
>>> >
>>>
>>> _______________________________________________
>>> ippm mailing list
>>> [e-mail]
>>> https://www.ietf.org/mailman/listinfo/ippm
>>
>>
>
>