IP Flow Information Export                                  C. Munukutla
Internet-Draft                                                   S. Vaid
Intended status: Standards Track                  Juniper Networks, Inc.
Expires: 11 August 2022                                        A. Mahale
                                                                D. Patel
                                                            Google, Inc.
                                                         7 February 2022


 IP Flow Information Export (IPFIX) Information Elements Extension for
                         Forwarding Exceptions
               draft-mvmd-opsawg-ipfix-fwd-exceptions-04

Abstract

   This draft proposes couple of new Forwarding exceptions related
   Information Elements (IEs) and Templates for the IP Flow Information
   Export (IPFIX) protocol.  These new Information Elements and
   Exception Template can be used to export information about any
   forwarding errors in a network.  This essential information is
   adequate to correlate packet drops to any control plane entity and
   map it to an impacted service.  Once exceptions are correlated to a
   particular entity, an action can be assigned to mitigate such
   problems essentially enabling self-driving networks.

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 https://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 11 August 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Information Elements  . . . . . . . . . . . . . . . . . . . .   4
   4.  New Information Elements  . . . . . . . . . . . . . . . . . .   6
     4.1.  Proposed New Information Elements . . . . . . . . . . . .   6
     4.2.  Definition of Exceptions  . . . . . . . . . . . . . . . .   7
       4.2.1.  forwardingExceptionCode . . . . . . . . . . . . . . .   7
       4.2.2.  forwardingNexthopId . . . . . . . . . . . . . . . . .   8
       4.2.3.  forwardingLookupType  . . . . . . . . . . . . . . . .   9
       4.2.4.  underlyingIngressInterface  . . . . . . . . . . . . .   9
   5.  Exception Templates . . . . . . . . . . . . . . . . . . . . .  10
     5.1.  IPFIX Exception Template 1 for Forwarding Exceptions  . .  10
     5.2.  IPFIX Exception Template 2 for Forwarding Exceptions  . .  11
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
     6.1.  Information Elements  . . . . . . . . . . . . . . . . . .  11
     6.2.  Forwarding Exception Codes  . . . . . . . . . . . . . . .  12
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  13
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   All networks are susceptible to traffic drops due to a number of
   factors.  Traffic drops can go unnoticed unless they are service
   impacting.  In a multi-layered network architecture, it is tedious
   manual work to localize and root cause traffic blackholing issues.
   Transient drops are even harder to detect.  Existing methodologies
   that rely on periodically monitoring interfaces on several hosts in a
   network does not guarantee timely detection, and are not scalable for
   large networks.





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   In order to eliminate this tedious monitoring work-flow, objective is
   to simplify localization and build correlation of dropped packets to
   particular entity.  The network entity shall identify the dropped
   packets by monitoring dropped counters or doing a deep packet
   inspection of the packet discarded by the forwarding ASIC.  The
   implementation of the method used to detect the drop is outside the
   scope of this document.  Dropped packets will be sampled in the
   forwarding-path and sent to a host or software queue along with type
   of exception, in/out interface information and other relevant meta
   data.  This will be a push model where the node encountering the
   error will emit the information about dropped packets and associated
   meta-data.  Techniques for IP Packet Selection [RFC5475] describes
   Sampling and Filtering techniques for IP packet selection either
   using Systematic Sampling or Random Sampling.

   The IPFIX Protocol Specification [RFC7011] defines a generic exchange
   mechanism for collecting flow information.  It supports source-
   triggered export of information via the push model approach.  The
   IPFIX Information Model [IANA-IPFIX] defines a list of standard
   Information Elements (IEs) which can be carried by the IPFIX
   protocol.

   This document focuses on telemetry information for dropped packet
   exceptions, and proposes an extension to IPFIX message format for
   collecting sampled exceptions.  Some of the IPFIX Information
   Elements (IEs) already exist, some will be defined along with
   corresponding formats.  It is also possible to achieve sampling of
   the dropped packets by using sampling methods like SFLOW but details
   of other sampling methods are outside the scope of this document.

1.1.  Terminology

   IPFIX-specific terminology (e.g.  Information Element, Template,
   Template Record, Options Template Record, Template Set, Collector,
   Exporter, Data Record) used in this document is defined in Section 2
   of [RFC7011].  As in [RFC7011] these IPFIX-specific terms have the
   first letter of a word capitalized.  This document also makes use of
   the same terminology and definitions as Section 2 of [RFC5470].

1.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.





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2.  Scope

   This document specifies the information model used for reporting
   packet-based forwarding exceptions.  [RFC7011] provides guidance on
   the choices of the transport protocols used for IPFIX and their
   effects.  Encoded IPFIX exception packets need to be reliably
   transported to the collector.  The choice of the actual transport
   protocol is beyond the scope of this document.

   This document assumes that all devices reporting exceptions will use
   existing IPFIX framework/module to send encoded packets to the
   collector.  This would mean that the network device will specify the
   template that it is going to use for each of the events.  The
   templates can be of varying length, and there could be multiple
   templates that a network device could use to encode the exceptions.

   The implementation details of the collector application are beyond
   the scope of this document.

3.  Information Elements

   The Exception template could contain a subset of the IEs shown in
   Table 1, depending upon the exception reported.

   Whenever packet drop happens inside forwarding plane, following
   information is key to understanding the issue: reason for packet
   drop, flow which encountered the drop (packet content), additional
   meta-data e.g. flow direction (ingress/egress), nexthop index, input
   interface, output interface, etc. on which this packet was flowing.

   The following table includes all the existing IEs that a device
   reporting IPFIX Exceptions using various Exception Templates would
   typically need.  The formats of IEs and IPFIX IDs are listed in the
   table below.

















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     +-------------------------------+--------+-------+--------------+
     | Field Name                    |  Size  |  IANA | Description  |
     |                               | (bits) | IPFIX |              |
     |                               |        |   ID  |              |
     +-------------------------------+--------+-------+--------------+
     | flowDirection                 |   8    |  61   | The direction|
     |                               |        |       | of the Flow  |
     |                               |        |       | observed at  |
     |                               |        |       | Observation  |
     |                               |        |       | point.       |
     |                               |        |       |              |
     | ingressInterface              |   32   |  10   | Index of IP  |
     |                               |        |       | interface    |
     |                               |        |       | where packets|
     |                               |        |       | of this flow |
     |                               |        |       | are being    |
     |                               |        |       | received.    |
     |                               |        |       |              |
     | egressInterface               |   32   |  14   | Index of IP  |
     |                               |        |       | interface    |
     |                               |        |       | where packets|
     |                               |        |       | of this flow |
     |                               |        |       | are being    |
     |                               |        |       | sent.        |
     |                               |        |       |              |
     | dataLinkFrameSize             |   16   |  312  | Specified    |
     |                               |        |       | length of    |
     |                               |        |       | data link    |
     |                               |        |       | frame.       |
     |                               |        |       |              |
     | dataLinkFrameSection          |  65535 |  315  | Carries n    |
     |                               |        |       | octets from  |
     |                               |        |       | data link    |
     |                               |        |       | frame of     |
     |                               |        |       | selected     |
     |                               |        |       | frame.       |
     |                               |        |       |              |
     | commonPropertiesID            |   64   |  137  | Identifier of|
     |                               |        |       | a set of     |
     |                               |        |       | common       |
     |                               |        |       | properties   |
     |                               |        |       | that is      |
     |                               |        |       | unique per   |
     |                               |        |       | observation  |
     |                               |        |       | domain.      |
     +-------------------------------+--------+-------+--------------+
             Table 1: Forwarding Exception Information Elements




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                       Figure 1: Information Elements

4.  New Information Elements

4.1.  Proposed New Information Elements

   The proposed new IEs that a device reporting Exceptions using
   Exception template would need are listed in Table 2 below.

   +---------------------------+---------------------+-----------------+
   | Field Name                | Abstract Data Type  | Description     |
   |                           |                     |                 |
   +---------------------------+---------------------+-----------------+
   | forwardingExceptionCode   | unsigned32          | Unique code for |
   |                           |                     | every exception |
   |                           |                     |                 |
   | forwardingNextHopID       | unsigned64          | Forwarding NH - |
   |                           |                     | index associated|
   |                           |                     | with packet that|
   |                           |                     | encountered     |
   |                           |                     | this exception  |
   |                           |                     |                 |
   | forwardingLookupType      | unsigned8           | Last Lookup     |
   |                           |                     | type performed  |
   |                           |                     | on the packet in|
   |                           |                     | in ingress path.|
   |                           |                     | For instance,   |
   |                           |                     | IPV4, IPV6,     |
   |                           |                     | Bridge, MPLS,   |
   |                           |                     | Unknown etc.    |
   |                           |                     |                 |
   | underlyingIngressInterface| unsigned32          | Underlying      |
   |                           |                     | interface from  |
   |                           |                     | which a packet  |
   |                           |                     | arrived in      |
   |                           |                     | ingress path.   |
   |                           |                     | For instance,   |
   |                           |                     | child interface |
   |                           |                     | of aggregate    |
   |                           |                     | interface on    |
   |                           |                     | which packet    |
   |                           |                     | came in ingress;|
   |                           |                     | where aggregate |
   |                           |                     | interface is    |
   |                           |                     | captured in     |
   |                           |                     | ingressInterface|
   +---------------------------+---------------------+-----------------+
               Table 2: New Information Elements



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                     Figure 2: New Information Elements

   The Information Elements defined in Table 2 are proposed to be
   incorporated into the IANA IPFIX Information Elements registry
   [IANA-IPFIX]

4.2.  Definition of Exceptions

   Every network will encounter issues like packet loss, from time to
   time.  Some of the causes for such a loss of traffic or a block in
   transmission of data packets include overloaded system conditions,
   misconfiguration, profiles and policies that restrict the bandwidth
   or priority of traffic, network outages, or disruption with physical
   cable faults.  Packet loss could also happen because of incorrect
   stitching of the forwarding path or a mismatch between control plane
   and data plane state.  Exception code entails the reason/error code
   due to which this packet has been dropped.

4.2.1.  forwardingExceptionCode

   forwardingExceptionCode will be defined in "IPFIX Information
   Elements" registry.  This list can be expanded in the future as
   necessary.  The data record will have corresponding exception code
   value to indicate forwarding error that caused the traffic drop.

   An implementation may choose to encode device internal exception
   codes as forwardingExceptionCode.  In such scenarios, Enterprise Bit
   MUST be set to 1 and corresponding Enterprise Number MUST be present
   as described in [RFC7011]

   There is an existing IE 89 - forwardingStatus [IANA-IPFIX] but it
   allows a very limited number of exceptions to be reported from the
   system (6-bit reason code).  The exception codes also need to be
   standardized for use.  Different forwarding ASICs would have
   different pipelines and hence discard reasons (which could be very
   specific to that pipeline) cannot be generalized.  Hence it makes
   sense to have a standalone IE for reporting exception which not only
   provides support to report larger number of exceptions but also
   provides freedom for reporting application specific exceptions using
   the enterprise bit.

   forwardingExceptionCode will also describe status of the flow with
   first two bits.  An implementation may choose to export
   forwardingExceptionCode instead of IE89 - forwardingStatus.

   A list of commonly used forwarding Exception codes will be identified
   and listed as part of Table 3 below.




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   +----------------+--------------------------------------------------+
   | Forwarding     |           Reason                                 |
   | Exception Code |                                                  |
   +----------------+--------------------------------------------------+
   |       1        | FIREWALL_DISCARD                                 |
   |       2        | TTL_EXPIRY                                       |
   |       3        | DISCARD_ROUTE                                    |
   |       4        | BAD_IPV4_CHECKSUM                                |
   |       5        | REJECT_ROUTE                                     |
   |       6        | BAD_IPV4_HEADER (Version incorrect or IHL < 5)|
   |       7        | BAD_IPV6_HEADER (Version incorrect)              |
   |       8        | BAD_IPV4_HEADER_LENGTH (V4 frame is too short)   |
   |       9        | BAD_IPV6_HEADER_LENGTH                           |
   |       10       | BAD_IPV6_OPTIONS_PACKET(too many option headers) |
   |       ..       | ..                                               |
   +----------------+--------------------------------------------------+

                     Figure 3: Table 3: Exception Codes

4.2.2.  forwardingNexthopId

   In terms of a network device, next hop is the gateway to which packet
   should be forwarded corresponding to the path to final destination.
   A given router doesn't need to store the entire forwarding path
   information for a destination.  As long as it can identify the next
   hop to be used for forwarding to a destination, the end to end
   forwarding can happen.  This helps reduce size of forwarding table.
   The nexthop index uniquely identifies the egress path a packet would
   take to reach the destination.  This could include information about
   the outgoing interface, layer 2 address to be used, forwarding
   features configured for the packet path etc.

   For instance, consider we have a L3VPN topology like below

               CE1 -------- PE1 ----- MPLS Network ----- PE2 ------- CE2

                    Figure 4: Figure 1: MPLS VPN Network

   Figure 1 above illustrates an example where reporting of exception
   can provide an insight into the error scenario.  CE1 and CE2
   communicate with each other over an MPLS VPN network.  The labels are
   typically advertised using protocols like RSVP or LDP.  When a packet
   is received from core network on PE1, a lookup on MPLS label results
   in packet getting forwarded towards CE1.  The entries in MPLS table
   are populated by corresponding protocol.  If label entries don't get
   populated in the MPLS table due to a probable glitch in the protocol
   configuration or some software inconsistency, the packets traversing
   on that LSP tunnel path shall get discarded on PE1.



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   In case of route lookups, that result in hierarchical forwarding
   chains, the mis-programming may manifest at different levels of the
   forwarding structure.  The forwarding lookup may fail on any level of
   the hierarchy in the forwarding chain.  It is expected that software
   at least report the nexthop where the lookup terminates.  Its
   desirable for software to report the top level nexthop in the chain.

   Using the mechanism described in this RFC, it will be possible to
   capture such packets and report them in IPFIX format with
   corresponding exception set (eg.  DISCARD_ROUTE) along with relevant
   packet bytes and meta-data.  This can help the operator/software to
   immediately understand root cause of the problem and take appropriate
   action.

   An implementation may choose to report linecard number, linecard
   type, forwarding ASIC type and forwarding ASIC number on which an
   exception occurs, but mechanism to export these fields is out of the
   scope of this document.

4.2.3.  forwardingLookupType

   A packet might undergo multiple lookups in the forwarding chain.
   Lookup may fail at any level of the lookup hierarchy.  When an
   exception is reported in such cases, type of the last lookup
   performed on the packet may help in identifying nature of the
   erroneous path.

   For instance, a Firewall Discard may happen for Layer2 or Layer3
   packet.  All such packets may be treated as FIREWALL_DISCARD for
   generic exception reporting purposes.  However, exact place of error
   in the pipeline (IPV4, IPV6, MPLS etc.) may help with easily
   correlating the exception.

4.2.4.  underlyingIngressInterface

   A packet can arrive on an aggregate ethernet(ae) interface where the
   receive interface is the ae but actual physical interface is a child
   member of this ae.  If such a packet gets dropped because of an
   exception, it will be very useful not only to know about the ae on
   which it arrived but also the child link of that ae on which the
   packet was received.

   underlyingIngressInterface represents the interface underlying the
   received interface (which in case of ae would be its child link) on
   which the packet arrived in ingress.  This helps in providing more
   context about the nature of the packet processing for this path.





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5.  Exception Templates

   This section presents a list of templates for reporting exceptions
   using newly proposed IEs in addition to few existing Information
   Elements (IEs).

   Templates listed below are sample templates to demonstrate the
   utility of newly introduced Information Elements in conjuction with
   existing Information Elements to report meaningful data to the
   collector.  A specific implementation may add or remove Information
   Elements from below templates based on their reporting requirements.

5.1.  IPFIX Exception Template 1 for Forwarding Exceptions

   Exception Template defined in Figure 1 demonstrates a sample set of
   data to export forwarding Exceptions.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Set ID = 2                |      Length = N octets        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID = 256           |       Field Count = N         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   forwardingExceptionCode       |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   forwardingNextHopId           |       Field Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   forwardingLookupType          |       Field Length = 1        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|      flowDirection              |       Field Length = 1        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     ingressInterface            |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     egressInterface             |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     dataLinkFrameSize           |       Field Length = 2        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|    dataLinkFrameSection         |       Field Length = 65535    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Padding (opt)                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 5: IPFIX Exception Template for Forwarding Exceptions









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5.2.  IPFIX Exception Template 2 for Forwarding Exceptions

   Alternatively, Exception Template defined in Figure 2 is a sample
   template to export forwarding exceptions.  This template demonstrates
   the use of Information Element 137 to represent following fields:
   forwardingExceptionCode, forwardingNexthopId, ingressInterface,
   underlyingIngressInterface and egressInterface.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Set ID = 2                |      Length = N octets        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID = 256           |       Field Count = N         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     commonPropertiesId1         |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|      flowDirection              |       Field Length = 1        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   forwardingLookupType          |       Field Length = 1        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     commonPropertiesId2         |       Field Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     commonPropertiesId3         |       Field Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     commonPropertiesId4         |       Field Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     commonPropertiesId5         |       Field Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     dataLinkFrameSize           |       Field Length = 2        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|    dataLinkFrameSection         |       Field Length = 65535    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Padding (opt)                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Figure 6: IPFIX Exception Template 2 for Forwarding Exceptions

6.  IANA Considerations

6.1.  Information Elements

   IANA manages the IPFIX Information Elements registry at [IANA-IPFIX].
   This document introduces two new IPFIX Information Elements.

   Name: forwardingExceptionCode ElementID: TBD Description: Exception
   code is an identifier uniquely describing cause of irregularity or
   traffic drop on a device.  Abstract Data Type: unsigned32 Data Type
   Semantics: identifier




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   Name: forwardingNexthopId ElementID: TBD Description: Nexthop ID is a
   unique identifier for a Nexthop on a device.  Abstract Data Type:
   unsigned64 Data Type Semantics: identifier

   Name: forwardingLookupType ElementID: TBD Description: Represents the
   last lookup performed on the packet in forwarding path.  Abstract
   Data Type: unsigned8 Data Type Semantics: identifier

   Name: underlyingIngressInterface ElementID: TBD Description: The
   underlying interface index of the interface from where packet of a
   given flow are received in ingress.  For example, child interface of
   an aggregate ethernet interface.  Abstract Data Type: unsigned32 Data
   Type Semantics: identifier

6.2.  Forwarding Exception Codes

   This document requests addition of a new registry for Forwarding
   Exception Codes.

   +----------------+--------------------------------------------------+
   | Forwarding     |           Reason                                 |
   | Exception Code |                                                  |
   +----------------+--------------------------------------------------+
   |       1        | FIREWALL_DISCARD                                 |
   |       2        | TTL_EXPIRY                                       |
   |       3        | DISCARD_ROUTE                                    |
   |       4        | BAD_IPV4_CHECKSUM                                |
   |       5        | REJECT_ROUTE                                     |
   |       6        | BAD_IPV4_HEADER (Version incorrect or IHL < 5)|
   |       7        | BAD_IPV6_HEADER (Version incorrect)              |
   |       8        | BAD_IPV4_HEADER_LENGTH (V4 frame is too short)   |
   |       9        | BAD_IPV6_HEADER_LENGTH                           |
   |       10       | BAD_IPV6_OPTIONS_PACKET(too many option headers) |
   |       ..       | ..                                               |
   +----------------+--------------------------------------------------+

                     Figure 7: Table 3: Exception Codes

   All assignments in this registry are to be performed via Expert
   Review.











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7.  Security Considerations

   Security Considerations listed in detail for IPFIX in [RFC7011] apply
   to this document as well.  As described in [RFC7011], the IPFIX
   messages exchanged between network device and collector MUST be
   protected to provide confidentiality, integrity, and authenticity.
   Without those characteristics, the messages are subject to various
   kinds of attacks.  These attacks are described in great detail in
   [RFC7011].

8.  Contributors

     Manikandan Musuvathi Poornachary
     Juniper Networks, Inc.
     Electra Exora Business Park~Marathahalli-Sarjapur Outer Ring Road,
     Bangalore, KA - 560103
     India
     Email: mpoornachary@juniper.net

     Vishnu Pavan Beeram
     Juniper Networks, Inc.
     1133 Innovation Way
     Sunnyvale, CA  94089
     USA
     Email: vbeeram@juniper.net

     Raveendra Torvi
     Juniper Networks, Inc.
     10 Technology Park Dr
     Westford, MA  01886
     USA
     Email: rtorvi@juniper.net

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5475]  Zseby, T., Molina, M., Duffield, N., Niccolini, S., and F.
              Raspall, "Sampling and Filtering Techniques for IP Packet
              Selection", RFC 5475, DOI 10.17487/RFC5475, March 2009,
              <https://www.rfc-editor.org/info/rfc5475>.





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   [RFC7011]  Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
              "Specification of the IP Flow Information Export (IPFIX)
              Protocol for the Exchange of Flow Information", STD 77,
              RFC 7011, DOI 10.17487/RFC7011, September 2013,
              <https://www.rfc-editor.org/info/rfc7011>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

9.2.  Informative References

   [IANA-IPFIX]
              IANA, "IP Flow Information Export (IPFIX) Entities",
              <https://www.iana.org/assignments/ipfix>.

   [RFC5470]  Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
              "Architecture for IP Flow Information Export", RFC 5470,
              DOI 10.17487/RFC5470, March 2009,
              <https://www.rfc-editor.org/info/rfc5470>.

Authors' Addresses

   Venkata Naga Chaitanya Munukutla
   Juniper Networks, Inc.
   10 Technology Park Dr
   Westford, MA 01886
   United States of America

   Email: vmunuku@juniper.net


   Shivam Vaid
   Juniper Networks, Inc.
   Electra, Exora Business Park- Marathahalli-Sarjapur Outer Ring Road
   Bangalore 560103
   Karnataka
   India

   Email: shivamv@juniper.net


   Aditya Mahale
   Google, Inc.
   1600 Amphitheatre Parkway
   Mountain View, CA 94043
   United States of America




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   Email: amahale@google.com


   Devang Patel
   Google, Inc.
   1600 Amphitheatre Parkway
   Mountain View, CA 94043
   United States of America

   Email: pateldevang@google.com









































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