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Requirements for In-band OAM
draft-brockners-inband-oam-requirements-01

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Authors Frank Brockners , Shwetha Bhandari , Sashank Dara , Carlos Pignataro , Hannes Gredler , John Leddy , Stephen Youell
Last updated 2016-07-18
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draft-brockners-inband-oam-requirements-01
Network Working Group                                       F. Brockners
Internet-Draft                                               S. Bhandari
Intended status: Informational                                   S. Dara
Expires: January 19, 2017                                   C. Pignataro
                                                                   Cisco
                                                              H. Gredler
                                                            RtBrick Inc.
                                                                J. Leddy
                                                                 Comcast
                                                               S. Youell
                                                                    JMPC
                                                           July 18, 2016

                      Requirements for In-band OAM
               draft-brockners-inband-oam-requirements-01

Abstract

   This document discusses the motivation and requirements for including
   specific operational and telemetry information into data packets
   while the data packet traverses a path between two points in the
   network.  This method is referred to as "in-band" Operations,
   Administration, and Maintenance (OAM), given that the OAM information
   is carried with the data packets as opposed to in "out-of-band"
   packets dedicated to OAM.  In-band OAM complements other OAM
   mechanisms which use dedicated probe packets to convey OAM
   information.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 19, 2017.

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Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Motivation for In-band OAM  . . . . . . . . . . . . . . . . .   4
     3.1.  Path Congruency Issues with Dedicated OAM Packets . . . .   5
     3.2.  Results Sent to a System Other Than the Sender  . . . . .   5
     3.3.  Overlay and Underlay Correlation  . . . . . . . . . . . .   5
     3.4.  SLA Verification  . . . . . . . . . . . . . . . . . . . .   6
     3.5.  Analytics and Diagnostics . . . . . . . . . . . . . . . .   6
     3.6.  Frame Replication/Elimination Decision for Bi-casting
           /Active-active Networks . . . . . . . . . . . . . . . . .   7
     3.7.  Proof of Transit  . . . . . . . . . . . . . . . . . . . .   7
     3.8.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . .   8
   4.  Considerations for In-band OAM  . . . . . . . . . . . . . . .   9
     4.1.  Type of information to be recorded  . . . . . . . . . . .  10
     4.2.  MTU and packet size . . . . . . . . . . . . . . . . . . .  10
     4.3.  Administrative boundaries . . . . . . . . . . . . . . . .  11
     4.4.  Selective enablement  . . . . . . . . . . . . . . . . . .  11
     4.5.  Optimization of node and interface identifiers  . . . . .  12
     4.6.  Loop communication path (IPv6-specifics)  . . . . . . . .  12
   5.  Requirements for In-band OAM Data Types . . . . . . . . . . .  12
     5.1.  Generic Requirements  . . . . . . . . . . . . . . . . . .  12
     5.2.  In-band OAM Data with Per-hop Scope . . . . . . . . . . .  13
     5.3.  In-band OAM with Selected Hop Scope . . . . . . . . . . .  14
     5.4.  In-band OAM with End-to-end Scope . . . . . . . . . . . .  14
   6.  Security Considerations and Requirements  . . . . . . . . . .  15
     6.1.  Proof of Transit  . . . . . . . . . . . . . . . . . . . .  15
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  16
   9.  Informative References  . . . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

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1.  Introduction

   This document discusses requirements for "in-band" Operations,
   Administration, and Maintenance (OAM) mechanisms.  "In-band" OAM
   means to record OAM and telemetry information within the data packet
   while the data packet traverses a network or a particular network
   domain.  The term "in-band" refers to the fact that the OAM and
   telemetry data is carried within data packets rather than being sent
   within packets specifically dedicated to OAM.  In-band OAM
   mechanisms, which are sometimes also referred to as embedded network
   telemetry are a current topic of discussion.  In-band network
   telemetry has been defined for P4 [P4].  The SPUD prototype
   [I-D.hildebrand-spud-prototype] uses a similar logic that allows
   network devices on the path between endpoints to participate
   explicitly in the tube outside the end-to-end context.  Even the IPv4
   route-record option defined in [RFC0791] can be considered an in-band
   OAM mechanism.  In-band OAM complements "out-of-band" mechanisms such
   as ping or traceroute, or more recent active probing mechanisms, as
   described in [I-D.lapukhov-dataplane-probe].  In-band OAM mechanisms
   can be leveraged where current out-of-band mechanisms do not apply or
   do not offer the desired characteristics or requirements, such as
   proving that a certain set of traffic takes a pre-defined path,
   strict congruency is desired, checking service level agreements for
   the live data traffic, detailed statistics on traffic distribution
   paths in networks that distribute traffic across multiple paths, or
   scenarios where probe traffic is potentially handled differently from
   regular data traffic by the network devices.  [RFC7276] presents an
   overview of OAM tools.

   Compared to probably the most basic example of "in-band OAM" which is
   IPv4 route recording [RFC0791], an in-band OAM approach has the
   following capabilities:

   a.  A flexible data format to allow different types of information to
       be captured as part of an in-band OAM operation, including not
       only path tracing information, but additional operational and
       telemetry information such as timestamps, sequence numbers, or
       even generic data such as queue size, geo-location of the node
       that forwarded the packet, etc.

   b.  A data format to express node as well as link identifiers to
       record the path a packet takes with a fixed amount of added data.

   c.  The ability to detect whether any nodes were skipped while
       recording in-band OAM information (i.e., in-band OAM is not
       supported or not enabled on those nodes).

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   d.  The ability to actively process information in the packet, for
       example to prove in a cryptographically secure way that a packet
       really took a pre-defined path using some traffic steering method
       such as service chaining or traffic engineering.

   e.  The ability to include OAM data beyond simple path information,
       such as timestamps or even generic data of a particular use case.

   f.  The ability to include OAM data in various different transport
       protocols.

2.  Conventions

   Abbreviations used in this document:

   ECMP:      Equal Cost Multi-Path

   MTU:       Maximum Transmit Unit

   NFV:       Network Function Virtualization

   OAM:       Operations, Administration, and Maintenance

   PMTU:      Path MTU

   SLA:       Service Level Agreement

   SFC:       Service Function Chain

   SR:        Segment Routing

   This document defines in-band Operations, Administration, and
   Maintenance (in-band OAM), as the subset in which OAM information is
   carried along with data packets.  This is as opposed to "out-of-band
   OAM", where specific packets are dedicated to carrying OAM
   information.

3.  Motivation for In-band OAM

   In several scenarios it is beneficial to make information about which
   path a packet took through the network available to the operator.
   This includes not only tasks like debugging, troubleshooting, as well
   as network planning and network optimization but also policy or
   service level agreement compliance checks.  This section discusses
   the motivation to introduce new methods for enhanced in-band network
   diagnostics.

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3.1.  Path Congruency Issues with Dedicated OAM Packets

   Mechanisms which add tracing information to the regular data traffic,
   sometimes also referred to as "in-band" or "passive OAM" can
   complement active, probe-based mechanisms such as ping or traceroute,
   which are sometimes considered as "out-of-band", because the messages
   are transported independently from regular data traffic.  "In-band"
   mechanisms do not require extra packets to be sent and hence don't
   change the packet traffic mix within the network.  Traceroute and
   ping for example use ICMP messages: New packets are injected to get
   tracing information.  Those add to the number of messages in a
   network, which already might be highly loaded or suffering
   performance issues for a particular path or traffic type.

   Packet scheduling algorithms, especially for balancing traffic across
   equal cost paths or links, often leverage information contained
   within the packet, such as protocol number, IP-address or MAC-
   address.  Probe packets would thus either need to be sent from the
   exact same endpoints with the exact same parameters, or probe packets
   would need to be artificially constructed as "fake" packets and
   inserted along the path.  Both approaches are often not feasible from
   an operational perspective, be it that access to the end-system is
   not feasible, or that the diversity of parameters and associated
   probe packets to be created is simply too large.  An in-band
   mechanism is an alternative in those cases.

   In-band mechanisms also don't suffer from implementations, where
   probe traffic is handled differently (and potentially forwarded
   differently) by a router than regular data traffic.

3.2.  Results Sent to a System Other Than the Sender

   Traditional ping and traceroute tools return the OAM results to the
   sender of the probe.  Even when the ICMP messages that are used with
   these tools are enhanced, and additional telemetry is collected
   (e.g., ICMP Multi-Part [RFC4884] supporting MPLS information
   [RFC4950], Interface and Next-Hop Identification [RFC5837], etc.), it
   would be advantageous to separate the sending of an OAM probe from
   the receiving of the telemetry data.  In this context, it is desired
   to not assume there is a bidirectional working path.

3.3.  Overlay and Underlay Correlation

   Several network deployments leverage tunneling mechanisms to create
   overlay or service-layer networks.  Examples include VXLAN-GPE, GRE,
   or LISP.  One often observed attribute of overlay networks is that
   they do not offer the user of the overlay any insight into the
   underlay network.  This means that the path that a particular

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   tunneled packet takes, nor other operational details such as the per-
   hop delay/jitter in the underlay are visible to the user of the
   overlay network, giving rise to diagnosis and debugging challenges in
   case of connectivity or performance issues.  The scope of OAM tools
   like ping or traceroute is limited to either the overlay or the
   underlay which means that the user of the overlay has typically no
   access to OAM in the underlay, unless specific operational procedures
   are put in place.  With in-band OAM the operator of the underlay can
   offer details of the connectivity in the underlay to the user of the
   overlay.  The operator of the egress tunnel router could choose to
   share the recorded information about the path with the user of the
   overlay.

   Coupled with mechanisms such as Segment Routing (SR)
   [I-D.ietf-spring-segment-routing], overlay network and underlay
   network can be more tightly coupled: The user of the overlay has
   detailed diagnostic information available in case of failure
   conditions.  The user of the overlay can also use the path recording
   information as input to traffic steering or traffic engineering
   mechanisms, to for example achieve path symmetry for the traffic
   between two endpoints.  [I-D.brockners-lisp-sr] is an example for how
   these methods can be applied to LISP.

3.4.  SLA Verification

   In-band OAM can help users of an overlay-service to verify that
   negotiated SLAs for the real traffic are met by the underlay network
   provider.  Different from solutions which rely on active probes to
   test an SLA, in-band OAM based mechanisms avoid wrong interpretations
   and "cheating", which can happen if the probe traffic that is used to
   perform SLA-check is prioritized by the network provider of the
   underlay.

3.5.  Analytics and Diagnostics

   Network planners and operators benefit from knowledge of the actual
   traffic distribution in the network.  When deriving an overall
   network connectivity traffic matrix one typically needs to correlate
   data gathered from each individual devices in the network.  If the
   path of a packet is recorded while the packet is forwarded, the
   entire path that a packet took through the network is available to
   the egress system.  This obviates the need to retrieve individual
   traffic statistics from every device in the network and correlate
   those statistics, or employ other mechanisms such as leveraging
   traffic engineering with null-bandwidth tunnels just to retrieve the
   appropriate statistics to generate the traffic matrix.

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   In addition, with individual path tracing, information is available
   at packet level granularity, rather than only at aggregate level - as
   is usually the case with IPFIX-style methods which employ flow-
   filters at the network elements.  Data-center networks which use
   equal-cost multipath (ECMP) forwarding are one example where detailed
   statistics on flow distribution in the network are highly desired.
   If a network supports ECMP, one can create detailed statistics for
   the different paths packets take through the network at the egress
   system, without a need to correlate/aggregate statistics from every
   router in the system.  Transit devices are off-loaded from the task
   of gathering packet statistics.

3.6.  Frame Replication/Elimination Decision for Bi-casting/Active-
      active Networks

   Bandwidth- and power-constrained, time-sensitive, or loss-intolerant
   networks (e.g., networks for industry automation/control, health
   care) require efficient OAM methods to decide when to replicate
   packets to a secondary path in order to keep the loss/error-rate for
   the receiver at a tolerable level - and also when to stop replication
   and eliminate the redundant flow.  Many IoT networks are time
   sensitive and cannot leverage automatic retransmission requests (ARQ)
   to cope with transmission errors or lost packets.  Transmitting the
   data over multiple disparate paths (often called bi-casting or live-
   live) is a method used to reduce the error rate observed by the
   receiver.  TSN receive a lot of attention from the manufacturing
   industry as shown by a various standardization activities and
   industry forums being formed (see e.g., IETF 6TiSCH, IEEE P802.1CB,
   AVnu).

3.7.  Proof of Transit

   Several deployments use traffic engineering, policy routing, segment
   routing or Service Function Chaining (SFC) [RFC7665] to steer packets
   through a specific set of nodes.  In certain cases regulatory
   obligations or a compliance policy require to prove that all packets
   that are supposed to follow a specific path are indeed being
   forwarded across the exact set of nodes specified.  If a packet flow
   is supposed to go through a series of service functions or network
   nodes, it has to be proven that all packets of the flow actually went
   through the service chain or collection of nodes specified by the
   policy.  In case the packets of a flow weren't appropriately
   processed, a verification device would be required to identify the
   policy violation and take corresponding actions (e.g., drop or
   redirect the packet, send an alert etc.) corresponding to the policy.
   In today's deployments, the proof that a packet traversed a
   particular service chain is typically delivered in an indirect way:
   Service appliances and network forwarding are in different trust

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   domains.  Physical hand-off-points are defined between these trust
   domains (i.e., physical interfaces).  Or in other terms, in the
   "network forwarding domain" things are wired up in a way that traffic
   is delivered to the ingress interface of a service appliance and
   received back from an egress interface of a service appliance.  This
   "wiring" is verified and trusted.  The evolution to Network Function
   Virtualization (NFV) and modern service chaining concepts (using
   technologies such as LISP, NSH, Segment Routing, etc.) blurs the line
   between the different trust domains, because the hand-off-points are
   no longer clearly defined physical interfaces, but are virtual
   interfaces.  Because of that very reason, networks operators require
   that different trust layers not to be mixed in the same device.  For
   an NFV scenario a different proof is required.  Offering a proof that
   a packet traversed a specific set of service functions would allow
   network operators to move away from the above described indirect
   methods of proving that a service chain is in place for a particular
   application.

   Deployed service chains without the presence of a "proof of transit"
   mechanism are typically operated as fail-open system: The packets
   that arrive at the end of a service chain are processed.  Adding
   "proof of transit" capabilites to a service chain allows an operator
   to turn a fail-open system into a fail-close system, i.e.  packets
   that did not properly traverse the service chain can be blocked.

   A solution approach could be based on OAM data which is added to
   every packet for achieving Proof Of Transit.  The OAM data is updated
   at every hop and is used to verify whether a packet traversed all
   required nodes.  When the verifier receives each packet, it can
   validate whether the packet traversed the service chain correctly.
   The detailed mechanisms used for path verification along with the
   procedures applied to the OAM data carried in the packet for path
   verification are beyond the scope of this document.  Details are
   addressed in [draft-brockners-proof-of-transit].  In this document
   the term "proof" refers to a discrete set of bits that represents an
   integer or string carried as OAM data.  The OAM data is used to
   verify whether a packet traversed the nodes it is supposed to
   traverse.

3.8.  Use Cases

   In-band OAM could be leveraged for several use cases, including:

   o  Traffic Matrix: Derive the network traffic matrix: Traffic for a
      given time interval between any two edge nodes of a given domain.
      Could be performed for all traffic or per QoS-class.

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   o  Flow Debugging: Discover which path(s) a particular set of traffic
      (identified by an n-tuple) takes in the network.  Such a procedure
      is particularly useful in case traffic is balanced across multiple
      paths, like with link aggregation (LACP) or equal cost multi-
      pathing (ECMP).

   o  Loss Statistics per Path: Retrieve loss statistics per flow and
      path in the network.

   o  Path Heat Maps: Discover highly utilized links in the network.

   o  Trend Analysis on Traffic Patterns: Analyze if (and if so how) the
      forwarding path for a specific set of traffic changes over time
      (can give hints to routing issues, unstable links etc.).

   o  Network Delay Distribution: Show delay distribution across network
      by node or links.  If enabled per application or for a specific
      flow then display the path taken along with the delay incurred at
      every hop.

   o  SLA Verification: Verify that a negotiated service level agreement
      (SLA), e.g., for packet drop rates or delay/jitter is conformed to
      by the actual traffic.

   o  Low-power Networks: Include application level OAM information
      (e.g., battery charge level, cache or buffer fill level) into data
      traffic to avoid sending extra OAM traffic which incur an extra
      cost on the devices.  Using the battery charge level as example,
      one could avoid sending extra OAM packets just to communicate
      battery health, and as such would save battery on sensors.

   o  Path Verification or Service Function Path Verification: Proof and
      verification of packets traversing check points in the network,
      where check points can be nodes in the network or service
      functions.

   o  Geo-location Policy: Network policy implemented based on which
      path packets took.  Example: Only if packets originated and stayed
      within the trading-floor department, access to specific
      applications or servers is granted.

4.  Considerations for In-band OAM

   The implementation of an in-band OAM mechanism needs to take several
   considerations into account, including administrative boundaries, how
   information is recorded, Maximum Transfer Unit (MTU), Path MTU
   discovery and packet size, etc.

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4.1.  Type of information to be recorded

   The information gathered for in-band OAM can be categorized into
   three main categories: Information with a per-hop scope, such as path
   tracing; information which applies to a specific set of nodes, such
   as path or service chain verification; information which only applies
   to the edges of a domain, such as sequence numbers.

   o  "edge to edge": Information that needs to be shared between
      network edges (the "edge" of a network could either be a host or a
      domain edge device): Edge to edge data e.g., packet and octet
      count of data entering a well-defined domain and leaving it is
      helpful in building traffic matrix, sequence number (also called
      "path packet counters") is useful for the flow to detect packet
      loss.

   o  "selected hops": Information that applies to a specific set of
      nodes only.  In case of path verification, only the nodes which
      are "check points" are required to interpret and update the
      information in the packet.

   o  "per hop": Information that is gathered at every hop along the
      path a packet traverses within an administrative domain:

      *  Hop by Hop information e.g., Nodes visited for path tracing,
         Timestamps at each hop to find delays along the path

      *  Stats collection at each hop to optimize communication in
         resource constrained networks e.g., Battery, CPU, memory status
         of each node piggy backed in a data packet is useful in low
         power lossy networks where network nodes are mostly asleep and
         communication is expensive

4.2.  MTU and packet size

   The recorded data at every hop may lead to packet size exceeding the
   Maximum Transmit Unit (MTU).  Based on the transport protocol used
   MTU is discovered as a configuration parameter or Path MTU (PMTU) is
   discovered dynamically.  Example: IPv6 recommends PMTU discovery
   before data packets are sent to prevent packet fragmentation.  It
   specifies 1280 octets as the default PDU to be carried in a IPv6
   datagram.  A detailed discussion of the implications of oversized
   IPv6 header chains if found in [RFC7112].

   The Path MTU restricts the amount of data that can be recorded for
   purpose of OAM within a data packet.  The total size of data to be
   recorded needs to be preset to avoid packet size exceeding the MTU.

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   It is recommended to pre-calculate and configures network devices to
   limit the in-band OAM data that is attached to a packet.

4.3.  Administrative boundaries

   There are several challenges in enabling in-band OAM in the public
   Internet as well as in corporate/enterprise networks across
   administrative domains, which include but are not limited to:

   o  Deployment dependent, the data fields that in-band OAM requires as
      part of a specific transport protocol may not be supported across
      administrative boundaries.

   o  Current OAM implementations are often done in the slow path, i.e.,
      OAM packets are punted to router's CPU for processing.  This leads
      to performance and scaling issues and opens up routers for attacks
      such as Denial of Service (DoS) attacks.

   o  Discovery of network topology and details of the network devices
      across administrative boundaries may open up attack vectors
      compromising network security.

   o  Specifically on IPv6: At the administrative boundaries IPv6
      packets with extension headers are dropped for several reasons
      described in [RFC7872].

   The following considerations will be discussed in a future version of
   this document: If the packet is dropped due to the presence of the
   in-band OAM; If the policy failure is treated as feature disablement
   and any further recording is stopped but the packet itself is not
   dropped, it may lead to every node in the path to make this policy
   decision.

4.4.  Selective enablement

   Deployment dependent, in-band OAM could either be used for all, or
   only a subset of the overall traffic.  While it might be desirable to
   apply in-band OAM to all traffic and then selectively use the data
   gathered in case needed, it might not always be feasible.  Depending
   on the forwarding infrastructure used, in-band OAM can have an impact
   on forwarding performance.  The SPUD prototype for example uses the
   notion of "pipes" to describe the portion of the traffic that could
   be subject to in-path inspection.  Mechanisms to decide which traffic
   would be subject to in-band OAM are outside the scope of this
   document.

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4.5.  Optimization of node and interface identifiers

   Since packets have a finite maximum size, the data recording or
   carrying capacity of one packet in which the in-band OAM meta data is
   present is limited.  In-band OAM should use its own dedicated
   namespace (confined to the domain in-band OAM operates in) to
   represent node and interface IDs to save space in the header.
   Generic representations of node and interface identifiers which are
   globally unique (such as a UUID) would consume significantly more
   bits of in-band OAM data.

4.6.  Loop communication path (IPv6-specifics)

   When recorded data is required to be analyzed on a source node that
   issues a packet and inserts in-band OAM data, the recorded data needs
   to be carried back to the source node.

   One way to carry the in-band OAM data back to the source is to
   utilize an ICMP Echo Request/Reply (ping) or ICMPv6 Echo Request/
   Reply (ping6) mechanism.  In order to run the in-band OAM mechanism
   appropriately on the ping/ping6 mechanism, the following two
   operations should be implemented by the ping/ping6 target node:

   1.  All of the in-band OAM fields would be copied from an Echo
       Request message to an Echo Reply message.

   2.  The Hop Limit field of the IPv6 header of these messages would be
       copied as a continuous sequence.  Further considerations are
       addressed in a future version of this document.

5.  Requirements for In-band OAM Data Types

   The above discussed use cases require different types of in-band OAM
   data.  This section details requirements for in-band OAM derived from
   the discussion above.

5.1.  Generic Requirements

   REQ-G1:  Classification: It should be possible to enable in-band OAM
            on a selected set of traffic.  The selected set of traffic
            can also be all traffic.

   REQ-G2:  Scope: If in-band OAM is used only within a specific domain,
            provisions need to be put in place to ensure that in-band
            OAM data stays within the specific domain only.

   REQ-G3:  Transport independence: Data formats for in-band OAM shall
            be defined in a transport independent way.  In-band OAM

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            applies to a variety of transport protocols.  Encapsulations
            should be defined how the generic data formats are carried
            by a specific protocol.

   REQ-G4:  Layering: It should be possible to have in-band OAM
            information for different transport protocol layers be
            present in several fields within a single packet.  This
            could for example be the case when tunnels are employed and
            in-band OAM information is to be gathered for both the
            underlay as well as the overlay network.

   REQ-G5:  MTU size: With in-band OAM information added, packets should
            not become larger than the path MTU.

   REQ-G6:  Data Structure Reusability: The data types and data formats
            defined and used for in-band OAM ought to be reusable for
            out-of-band OAM telemetry as well.

5.2.  In-band OAM Data with Per-hop Scope

   REQ-H1:  Missing nodes detection: Data shall be present that allows a
            node to detect whether all nodes that should participate in
            in-band OAM operations have indeed participated.

   REQ-H2:  Node, instance or device identifier: Data shall be present
            that allows to retrieve the identity of the entity reporting
            telemetry information.  The entity can be a device, or a
            subsystem/component within a device.  The latter will allow
            for packet tracing within a device in much the same way as
            between devices.

   REQ-H3:  Ingress interface identifier: Data shall be present that
            allows the identification of the interface a particular
            packet was received from.  The interface can be a logical or
            physical entity.

   REQ-H4:  Egress interface identifier: Data shall be present that
            allows the identification of the interface a particular
            packet was forwarded to.  Interface can be a logical or
            physical entity.

   REQ-H5:  Time-related requirements

            REQ-H5.1:  Delay: Data shall be present that allows to
                       retrieve the delay between two or more points of
                       interest within the system.  Those points can be
                       within the same device or on different devices.

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            REQ-H5.2:  Jitter: Data shall be present that allows to
                       retrieve the jitter between two or more points of
                       interest within the system.  Those points can be
                       within the same device or on different devices.

            REQ-H5.3:  Wall-clock time: Data shall be present that
                       allows to retrieve the wall-clock time visited a
                       particular point of interest in the system.

            REQ-H5.4:  Time precision: The precision of the time related
                       data should be configurable.  Use-case dependent,
                       the required precision could e.g., be nano-
                       seconds, micro-seconds, milli-seconds, or
                       seconds.

   REQ-H6:  Generic data records (like e.g., GPS/Geo-location
            information): It should be possible to add user-defined OAM
            data at select hops to the packet.  The semantics of the
            data are defined by the user.

5.3.  In-band OAM with Selected Hop Scope

   REQ-S1:  Proof of transit: Data shall be present which allows to
            securely prove that a packet has visited or ore several
            particular points of interest (i.e., a particular set of
            nodes).

            REQ-S1.1:  In case "Shamir's secret sharing scheme" is used
                       for proof of transit, two data records, "random"
                       and "cumulative" shall be present.  The number of
                       bits used for "random" and "cumulative" data
                       records can vary between deployments and should
                       thus be configurable.

            REQ-S1.2:  Enable a fail-open service chaining system to be
                       converted into a fail-closed service chaining
                       system.

5.4.  In-band OAM with End-to-end Scope

   REQ-E1:  Sequence numbering:

            REQ-E1.1:  Reordering detection: It should be possible to
                       detect whether packets have been reordered while
                       traversing an in-band OAM domain.

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            REQ-E1.2:  Duplicates detection: It should be possible to
                       detect whether packets have been duplicated while
                       traversing an in-band OAM domain.

            REQ-E1.3:  Detection of packet drops: It should be possible
                       to detect whether packets have been dropped while
                       traversing an in-band OAM domain.

6.  Security Considerations and Requirements

   General Security considerations will be addressed in a later version
   of this document.  Security considerations for Proof of Transit alone
   are discussed below.

6.1.  Proof of Transit

   Threat Model: Attacks on the deployments could be due to malicious
   administrators or accidental misconfigurations resulting in bypassing
   of certain nodes.  The solution approach should meet the following
   requirements:

   REQ-SEC1:  Sound Proof of Transit: A valid and verifiable proof that
              the packet definitively traversed through all the nodes as
              expected.  Probabilistic methods to achieve this should be
              avoided, as the same could be exploited by an attacker.

   REQ-SEC2:  Tampering of meta data: An active attacker should not be
              able to insert or modify or delete meta data in whole or
              in parts and bypass few (or all) nodes.  Any deviation
              from the expected path should be accurately determined.

   REQ-SEC3:  Replay Attacks: A attacker (active/passive) should not be
              able to reuse the proof of transit bits in the packet by
              observing the OAM data in the packet, packet
              characteristics (like IP addresses, octets transferred,
              timestamps) or even the proof bits themselves.  The
              solution approach should consider usage of these
              parameters for deriving any secrets cautiously.
              Mitigating replay attacks beyond a window of longer
              duration could be intractable to achieve with fixed number
              of bits allocated for proof.

   REQ-SEC4:  Recycle Secrets: Any configuration of the secrets (like
              cryptographic keys, initialisation vectors etc.) either in
              the controller or service functions should be
              reconfigurable.  Solution approach should enable controls,
              API calls etc. needed in order to perform such recycling.
              It is desirable to provide recommendations on the duration

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              of rotation cycles needed for the secure functioning of
              the overall system.

   REQ-SEC5:  Secret storage and distribution: Secrets should be shared
              with the devices over secure channels.  Methods should be
              put in place so that secrets cannot be retrieved by non
              authorized personnel from the devices.

7.  IANA Considerations

   [RFC Editor: please remove this section prior to publication.]

   This document has no IANA actions.

8.  Acknowledgements

   The authors would like to thank Eric Vyncke, Nalini Elkins, Srihari
   Raghavan, Ranganathan T S, Karthik Babu Harichandra Babu, Akshaya
   Nadahalli, and Andrew Yourtchenko for the comments and advice.  This
   document leverages and builds on top of several concepts described in
   [draft-kitamura-ipv6-record-route].  The authors would like to
   acknowledge the work done by the author Hiroshi Kitamura and people
   involved in writing it.

9.  Informative References

   [draft-brockners-proof-of-transit]
              Brockners, F., Bhandari, S., and S. Dara, "Proof of
              transit", July 2016.

   [draft-kitamura-ipv6-record-route]
              Kitamura, H., "Record Route for IPv6 (PR6),Hop-by-Hop
              Option Extension", November 2000.

   [I-D.brockners-lisp-sr]
              Brockners, F., Bhandari, S., Maino, F., and D. Lewis,
              "LISP Extensions for Segment Routing", draft-brockners-
              lisp-sr-01 (work in progress), February 2014.

   [I-D.hildebrand-spud-prototype]
              Hildebrand, J. and B. Trammell, "Substrate Protocol for
              User Datagrams (SPUD) Prototype", draft-hildebrand-spud-
              prototype-03 (work in progress), March 2015.

   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
              and R. Shakir, "Segment Routing Architecture", draft-ietf-
              spring-segment-routing-09 (work in progress), July 2016.

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   [I-D.lapukhov-dataplane-probe]
              Lapukhov, P. and r. remy@barefootnetworks.com, "Data-plane
              probe for in-band telemetry collection", draft-lapukhov-
              dataplane-probe-01 (work in progress), June 2016.

   [P4]       Kim, , "P4: In-band Network Telemetry (INT)", September
              2015.

   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791,
              DOI 10.17487/RFC0791, September 1981,
              <http://www.rfc-editor.org/info/rfc791>.

   [RFC4884]  Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
              "Extended ICMP to Support Multi-Part Messages", RFC 4884,
              DOI 10.17487/RFC4884, April 2007,
              <http://www.rfc-editor.org/info/rfc4884>.

   [RFC4950]  Bonica, R., Gan, D., Tappan, D., and C. Pignataro, "ICMP
              Extensions for Multiprotocol Label Switching", RFC 4950,
              DOI 10.17487/RFC4950, August 2007,
              <http://www.rfc-editor.org/info/rfc4950>.

   [RFC5837]  Atlas, A., Ed., Bonica, R., Ed., Pignataro, C., Ed., Shen,
              N., and JR. Rivers, "Extending ICMP for Interface and
              Next-Hop Identification", RFC 5837, DOI 10.17487/RFC5837,
              April 2010, <http://www.rfc-editor.org/info/rfc5837>.

   [RFC7112]  Gont, F., Manral, V., and R. Bonica, "Implications of
              Oversized IPv6 Header Chains", RFC 7112,
              DOI 10.17487/RFC7112, January 2014,
              <http://www.rfc-editor.org/info/rfc7112>.

   [RFC7276]  Mizrahi, T., Sprecher, N., Bellagamba, E., and Y.
              Weingarten, "An Overview of Operations, Administration,
              and Maintenance (OAM) Tools", RFC 7276,
              DOI 10.17487/RFC7276, June 2014,
              <http://www.rfc-editor.org/info/rfc7276>.

   [RFC7665]  Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
              Chaining (SFC) Architecture", RFC 7665,
              DOI 10.17487/RFC7665, October 2015,
              <http://www.rfc-editor.org/info/rfc7665>.

   [RFC7872]  Gont, F., Linkova, J., Chown, T., and W. Liu,
              "Observations on the Dropping of Packets with IPv6
              Extension Headers in the Real World", RFC 7872,
              DOI 10.17487/RFC7872, June 2016,
              <http://www.rfc-editor.org/info/rfc7872>.

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Authors' Addresses

   Frank Brockners
   Cisco Systems, Inc.
   Hansaallee 249, 3rd Floor
   DUESSELDORF, NORDRHEIN-WESTFALEN  40549
   Germany

   Email: fbrockne@cisco.com

   Shwetha Bhandari
   Cisco Systems, Inc.
   Cessna Business Park, Sarjapura Marathalli Outer Ring Road
   Bangalore, KARNATAKA 560 087
   India

   Email: shwethab@cisco.com

   Sashank Dara
   Cisco Systems, Inc.
   Cessna Business Park, Sarjapura Marathalli Outer Ring Road
   Bangalore, KARNATAKA 560 087
   India

   Email: sadara@cisco.com

   Carlos Pignataro
   Cisco Systems, Inc.
   7200-11 Kit Creek Road
   Research Triangle Park, NC  27709
   United States

   Email: cpignata@cisco.com

   Hannes Gredler
   RtBrick Inc.

   Email: hannes@rtbrick.com

   John Leddy
   Comcast

   Email: John_Leddy@cable.comcast.com

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   Stephen Youell
   JP Morgan Chase
   25 Bank Street
   London  E14 5JP
   United Kingdom

   Email: stephen.youell@jpmorgan.com

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