Operations and Management Area Working Group J. Evans
Internet-Draft O. Pylypenko
Intended status: Standards Track Amazon
Expires: 4 September 2025 J. Haas
Juniper Networks
A. Kadosh
Cisco Systems, Inc.
M. Boucadair
Orange
3 March 2025
Information and Data Models for Packet Discard Reporting
draft-ietf-opsawg-discardmodel-05
Abstract
This document defines an information model and corresponding data
model for packet discard reporting. The information model provides
an implementation-independent framework for classifying packet loss
to enable automated network mitigation of unintended packet loss.
The data model specifies a YANG implementation of this framework for
network elements.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at https://o-
pylypenko.github.io/draft-ietf-opsawg-discardmodel/draft-ietf-opsawg-
discardmodel.html. Status information for this document may be found
at https://datatracker.ietf.org/doc/draft-ietf-opsawg-discardmodel/.
Discussion of this document takes place on the Operations and
Management Area Working Group mailing list (mailto:opsawg@ietf.org),
which is archived at https://mailarchive.ietf.org/arch/browse/
opsawg/. Subscribe at https://www.ietf.org/mailman/listinfo/opsawg/.
Source for this draft and an issue tracker can be found at
https://github.com/o-pylypenko/draft-ietf-opsawg-discardmodel.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on 4 September 2025.
Copyright Notice
Copyright (c) 2025 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 (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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 5
4. Information Model . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Structure . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Sub-type Definitions . . . . . . . . . . . . . . . . . . 12
4.3. Information Model - YANG Module . . . . . . . . . . . . . 13
5. Data Model . . . . . . . . . . . . . . . . . . . . . . . . . 28
5.1. Structure . . . . . . . . . . . . . . . . . . . . . . . . 28
5.2. Implementation Requirements . . . . . . . . . . . . . . . 32
5.3. Usage Examples . . . . . . . . . . . . . . . . . . . . . 33
5.4. Data model - YANG Module . . . . . . . . . . . . . . . . 34
6. Security Considerations . . . . . . . . . . . . . . . . . . . 36
6.1. Information Model . . . . . . . . . . . . . . . . . . . . 36
6.2. Data Model . . . . . . . . . . . . . . . . . . . . . . . 36
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 38
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 38
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 38
10.1. Normative References . . . . . . . . . . . . . . . . . . 38
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10.2. Informative References . . . . . . . . . . . . . . . . . 38
Appendix A. Where do packets get dropped? . . . . . . . . . . . 40
Appendix B. Example signal-to-mitigation action mapping . . . . 41
Appendix C. Implementation Experience . . . . . . . . . . . . . 43
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 44
1. Introduction
The primary function of a network is to transport and deliver packets
according to service level objectives. For network operators,
understanding both where and why packet loss occurs within a network
is essential for effective operation. Device-reported packet loss
provides the most direct signal for identifying service impact.
While certain types of packet loss, such as policy-based discards,
are intentional and part of normal network operation, unintended
packet loss can impact customer services. To automate network
operations, operators must be able to detect customer-impacting
packet loss, determine its root cause, and apply appropriate
mitigation actions. Precise classification of packet loss is crucial
to ensure that anomalous packet loss is easily detected and that the
right action is taken to mitigate the impact. Taking the wrong
action can make problems worse; for example, removing a congested
device from service can exacerbate congestion by redirecting traffic
to other already congested links or devices.
Existing metrics for reporting packet loss, such as ifInDiscards,
ifOutDiscards, ifInErrors, and ifOutErrors defined in MIB-II
[RFC1213] and the YANG Data Model for Interface Management [RFC8343],
are insufficient for automating network operations. First, they lack
precision; for instance, ifInDiscards aggregates all discarded
inbound packets without specifying the cause, making it challenging
to distinguish between intended and unintended discards. Second,
these definitions are ambiguous, leading to inconsistent vendor
implementations. For example, in some implementations ifInErrors
accounts only for errored packets that are dropped, while in others,
it includes all errored packets, whether they are dropped or not.
Many implementations support more discard metrics than these,
however, they have been inconsistently implemented due to the lack of
a standardised classification scheme and clear semantics for packet
loss reporting. For example, [RFC7270] provides support for
reporting discards per flow in IPFIX using forwardingStatus, however,
the defined drop reason codes also lack sufficient clarity to
facilitate automated root cause analysis and impact mitigation, e.g.,
the "For us" reason code.
This document defines an information model and corresponding data
model for packet loss reporting which address these issues. The
information model provides precise classification of packet loss to
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enable accurate automated mitigation. The data model specifies a
YANG implementation of this framework for network elements, while
maintaining consistency through clear semantics.
The scope of this document is limited to reporting packet loss at
Layer 3 and frames discarded at Layer 2. This document considers
only the signals that may trigger automated mitigation actions and
not how the actions are defined or executed.
Section 3 describes the problem space and requirements. Section 4
defines the information model and classification scheme. Section 5
specifies the corresponding data model and implementation
requirements together with a set of usage examples, and the complete
YANG module definition for the data model. The appendices provide
additional context and implementation guidance.
2. Terminology
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.
A packet discard accounts for any instance where a packet is dropped
by a device, regardless of whether the discard was intentional or
unintentional.
Intended discards are packets dropped due to deliberate network
policies or configurations designed to enforce security or quality of
service. For example, packets dropped because they match an Access
Control List (ACL) denying certain traffic types.
Unintended discards are packets that were dropped, which the network
operator otherwise intended to deliver, i.e. which indicates an error
state. There are many possible reasons for unintended packet loss,
including: erroring links may corrupt packets in transit; incorrect
routing tables may result in packets being dropped because they do
not match a valid route; configuration errors may result in a valid
packet incorrectly matching an ACL and being dropped.
Tree diagrams used in this document follow the notation defined in
[RFC8340].
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3. Problem Statement
The fundamental problem for network operators is how to automatically
detect when unintended packet loss is occurring and determine the
appropriate action to mitigate it. For any network there are a small
set of potential actions that can be taken to mitigate customer
impact when unintended packet loss is detected:
1. Take a problematic device, link, or set of devices and/or links
out of service.
2. Return a device, link, or set of devices and/or links back into
service.
3. Move traffic to other links or devices to alleviate congestion or
avoid problematic paths.
4. Roll back a recent change to a device that might have caused the
problem.
5. Escalate to a network operator as a last resort when automated
mitigation is not possible.
The ability to select the appropriate mitigation action depends on
four key features of packet loss:
FEATURE-DISCARD-LOCATION: Determines which devices, interfaces and/
or flows are impacted.
FEATURE-DISCARD-RATE: The rate and/or magnitude of the discards,
indicating the severity and urgency of the problem.
FEATURE-DISCARD-DURATION: The duration of the discards which helps
to distinguish transient from persistent issues.
FEATURE-DISCARD-CLASS: The type or class of discards, which is
crucial for selecting the appropriate of mitigation - for example:
error discards may require taking faulty components out of
service; no-buffer discards may require traffic redistribution;
policy discards typically require no automated action
While FEATURE-DISCARD-LOCATION, FEATURE-DISCARD-RATE, and FEATURE-
DISCARD-DURATION are implicitly supported by MIB-II [RFC1213] and the
YANG Data Model for Interface Management [RFC8343], FEATURE-DISCARD-
CLASS requires a more detailed classification scheme than they
define. The following information model defines such a
classification scheme to enable automated mapping from loss signals
to appropriate mitigation actions.
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4. Information Model
The information model is defined using YANG [RFC6020] with Data
Structure Extensions [RFC8791], allowing the model to remain abstract
and decoupled from specific implementations in accordance with
[RFC3444]. This abstraction supports different data model
implementations - for example, in YANG, IPFIX [RFC7011], gMNI [gMNI]
or SNMP [RFC1157] - while ensuring consistency across
implementations. Using YANG for the information model enables this
abstraction, leverages the community's familiarity with its syntax,
and ensures lossless translation to the corresponding YANG data
model, which is defined in Section 5.
4.1. Structure
The information model defines a hierarchical classification scheme
for packet discards, which captures where in a device the discards
are accounted (component), in which direction they were flowing
(direction), whether they were successfully processed or discarded
(type), what protocol layer they belong to (layer), and the specific
reason for any discards (sub-types). This organisation enables both
high-level monitoring of total discards and more detailed triage to
map to mitigation actions.
A complete classification path follows the pattern:
component/direction/type/layer/sub-type/sub-sub-type/.../metric.
Appendix A illustrates where these discards typically occur in a
network device. The elements of the tree are defined as follows:
* Component:
- interface: discards of traffic to or from a specific network
interface.
- device: discards of traffic transiting the device.
- control-plane: discards of traffic to or from the device's
control plane.
- flow: discards of traffic associated with a specific traffic
flow.
* Direction:
- ingress: counters for incoming packets or frames.
- egress: counters for outgoing packets or frames.
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* Type:
- traffic: counters for successfully received or transmitted
packets or frames.
- discards: counters for packets or frames that were dropped.
* Layer:
- l2: Layer 2 traffic and discards, i.e. frame and byte counts.
- l3: Layer 3 traffic and discards, i.e. packet and byte counts.
The hierarchical structure allows for future extension while
maintaining backward compatibility. New discard types can be added
as new branches without affecting existing implementations.
The following YANG tree diagram shows the complete structure:
module: ietf-packet-discard-reporting-sx
structure packet-discard-reporting:
+-- control-plane {control-plane-stats}?
| +-- traffic* [direction]
| | +-- direction identityref
| | +-- packets? uint32
| | +-- bytes? uint32
| +-- discards* [direction]
| +-- direction identityref
| +-- packets? uint32
| +-- bytes? uint32
| +-- policy
| +-- packets? uint32
+-- interface* [name] {per-interface-stats}?
| +-- name string
| +-- traffic* [direction]
| | +-- direction identityref
| | +-- l2
| | | +-- frames? uint64
| | | +-- bytes? uint64
| | +-- l3
| | | +-- address-family-stat* [address-family]
| | | +-- address-family identityref
| | | +-- packets? uint64
| | | +-- bytes? uint64
| | | +-- unicast
| | | | +-- packets? uint64
| | | | +-- bytes? uint64
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| | | +-- multicast
| | | +-- packets? uint64
| | | +-- bytes? uint64
| | +-- qos
| | +-- class* [id]
| | +-- id string
| | +-- packets? uint64
| | +-- bytes? uint64
| +-- discards* [direction]
| +-- direction identityref
| +-- l2
| | +-- frames? uint64
| | +-- bytes? uint64
| +-- l3
| | +-- address-family-stat* [address-family]
| | +-- address-family identityref
| | +-- packets? uint64
| | +-- bytes? uint64
| | +-- unicast
| | | +-- packets? uint64
| | | +-- bytes? uint64
| | +-- multicast
| | +-- packets? uint64
| | +-- bytes? uint64
| +-- errors
| | +-- l2
| | | +-- rx
| | | | +-- frames? uint32
| | | | +-- crc-error? uint32
| | | | +-- invalid-mac? uint32
| | | | +-- invalid-vlan? uint32
| | | | +-- invalid-frame? uint32
| | | +-- tx
| | | +-- frames? uint32
| | +-- l3
| | | +-- rx
| | | | +-- packets? uint32
| | | | +-- checksum-error? uint32
| | | | +-- mtu-exceeded? uint32
| | | | +-- invalid-packet? uint32
| | | +-- ttl-expired? uint32
| | | +-- no-route? uint32
| | | +-- invalid-sid? uint32
| | | +-- invalid-label? uint32
| | | +-- tx
| | | +-- packets? uint32
| | +-- internal
| | +-- packets? uint32
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| | +-- parity-error? uint32
| +-- policy
| | +-- l2
| | | +-- frames? uint32
| | | +-- acl? uint32
| | +-- l3
| | +-- packets? uint32
| | +-- acl? uint32
| | +-- policer
| | | +-- packets? uint32
| | | +-- bytes? uint32
| | +-- null-route? uint32
| | +-- rpf? uint32
| | +-- ddos? uint32
| +-- no-buffer
| +-- class* [id]
| +-- id string
| +-- packets? uint64
| +-- bytes? uint64
+-- flow* [direction] {flow-reporting}?
| +-- direction identityref
| +-- traffic
| | +-- l2
| | | +-- frames? uint64
| | | +-- bytes? uint64
| | +-- l3
| | | +-- address-family-stat* [address-family]
| | | +-- address-family identityref
| | | +-- packets? uint64
| | | +-- bytes? uint64
| | | +-- unicast
| | | | +-- packets? uint64
| | | | +-- bytes? uint64
| | | +-- multicast
| | | +-- packets? uint64
| | | +-- bytes? uint64
| | +-- qos
| | +-- class* [id]
| | +-- id string
| | +-- packets? uint64
| | +-- bytes? uint64
| +-- discards
| +-- l2
| | +-- frames? uint64
| | +-- bytes? uint64
| +-- l3
| | +-- address-family-stat* [address-family]
| | +-- address-family identityref
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| | +-- packets? uint64
| | +-- bytes? uint64
| | +-- unicast
| | | +-- packets? uint64
| | | +-- bytes? uint64
| | +-- multicast
| | +-- packets? uint64
| | +-- bytes? uint64
| +-- errors
| | +-- l2
| | | +-- rx
| | | | +-- frames? uint32
| | | | +-- crc-error? uint32
| | | | +-- invalid-mac? uint32
| | | | +-- invalid-vlan? uint32
| | | | +-- invalid-frame? uint32
| | | +-- tx
| | | +-- frames? uint32
| | +-- l3
| | | +-- rx
| | | | +-- packets? uint32
| | | | +-- checksum-error? uint32
| | | | +-- mtu-exceeded? uint32
| | | | +-- invalid-packet? uint32
| | | +-- ttl-expired? uint32
| | | +-- no-route? uint32
| | | +-- invalid-sid? uint32
| | | +-- invalid-label? uint32
| | | +-- tx
| | | +-- packets? uint32
| | +-- internal
| | +-- packets? uint32
| | +-- parity-error? uint32
| +-- policy
| | +-- l2
| | | +-- frames? uint32
| | | +-- acl? uint32
| | +-- l3
| | +-- packets? uint32
| | +-- acl? uint32
| | +-- policer
| | | +-- packets? uint32
| | | +-- bytes? uint32
| | +-- null-route? uint32
| | +-- rpf? uint32
| | +-- ddos? uint32
| +-- no-buffer
| +-- class* [id]
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| +-- id string
| +-- packets? uint64
| +-- bytes? uint64
+-- device {per-device-stats}?
+-- traffic
| +-- l2
| | +-- frames? uint64
| | +-- bytes? uint64
| +-- l3
| | +-- address-family-stat* [address-family]
| | +-- address-family identityref
| | +-- packets? uint64
| | +-- bytes? uint64
| | +-- unicast
| | | +-- packets? uint64
| | | +-- bytes? uint64
| | +-- multicast
| | +-- packets? uint64
| | +-- bytes? uint64
| +-- qos
| +-- class* [id]
| +-- id string
| +-- packets? uint64
| +-- bytes? uint64
+-- discards
+-- l2
| +-- frames? uint64
| +-- bytes? uint64
+-- l3
| +-- address-family-stat* [address-family]
| +-- address-family identityref
| +-- packets? uint64
| +-- bytes? uint64
| +-- unicast
| | +-- packets? uint64
| | +-- bytes? uint64
| +-- multicast
| +-- packets? uint64
| +-- bytes? uint64
+-- errors
| +-- l2
| | +-- rx
| | | +-- frames? uint32
| | | +-- crc-error? uint32
| | | +-- invalid-mac? uint32
| | | +-- invalid-vlan? uint32
| | | +-- invalid-frame? uint32
| | +-- tx
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| | +-- frames? uint32
| +-- l3
| | +-- rx
| | | +-- packets? uint32
| | | +-- checksum-error? uint32
| | | +-- mtu-exceeded? uint32
| | | +-- invalid-packet? uint32
| | +-- ttl-expired? uint32
| | +-- no-route? uint32
| | +-- invalid-sid? uint32
| | +-- invalid-label? uint32
| | +-- tx
| | +-- packets? uint32
| +-- internal
| +-- packets? uint32
| +-- parity-error? uint32
+-- policy
| +-- l2
| | +-- frames? uint32
| | +-- acl? uint32
| +-- l3
| +-- packets? uint32
| +-- acl? uint32
| +-- policer
| | +-- packets? uint32
| | +-- bytes? uint32
| +-- null-route? uint32
| +-- rpf? uint32
| +-- ddos? uint32
+-- no-buffer
+-- class* [id]
+-- id string
+-- packets? uint64
+-- bytes? uint64
The corresponding YANG module is defined in Section 4.3.
4.2. Sub-type Definitions
discards/policy/: These are intended discards, meaning packets
dropped by a device due to a configured policy, including: ACLs,
traffic policers, Reverse Path Forwarding (RPF) checks, DDoS
protection rules and explicit null routes
discards/error/: These are unintended discards due to errors in
processing packets or frames. There are multiple sub-classes.
discards/error/l2/rx/: These are frames discarded due to errors in
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the received Layer 2 frame, including: CRC errors, invalid MAC
addresses, invalid VLAN tags, frame size violations and other
malformed frame conditions
discards/error/l3/rx/: These are discards which occur due to errors
in the received packet, indicating an upstream problem rather than
an issue with the device dropping the errored packets, including:
header checksum errors, MTU exceeded, invalid packet errors, i.e.
incorrect version, incorrect header length, invalid options and
other malformed packet conditions
discards/error/l3/rx/ttl-expired: These are discards due to TTL (or
Hop limit) expiry, which can occur for the following reasons:
normal trace-route operations, end-system TTL/Hop limit set too
low, routing loops in the network.
discards/error/l3/no-route/: These are discards which occur due to a
packet not matching any route in the routing table, e.g. which may
be due to routing configuration errors or may be transient
discards during convergence.
discards/error/local/: These are discards due to internal device
issues, including: parity errors in device memory or other
internal hardware errors. Any errored discards not explicitly
assigned to other classes are also accounted for here.
discards/no-buffer/: These are discards due to buffer exhaustion,
i.e. congestion related discards. These can be tail-drop discards
or due to an active queue management algorithm, such as RED
[RED93] or CODEL [RFC8289].
An example of possible signal-to-mitigation action mapping is
provided in Appendix B.
4.3. Information Model - YANG Module
The "ietf-packet-discard-reporting" module uses the "sx" structure
defined in [RFC8791].
<CODE BEGINS>
module ietf-packet-discard-reporting-sx {
yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:ietf-packet-discard-reporting-sx";
prefix plr-sx;
import ietf-yang-structure-ext {
prefix sx;
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reference
"RFC 8791: YANG Data Structure Extensions";
}
organization
"IETF OPSAWG (Operations and Management Area Working Group)";
contact
"WG Web: https://datatracker.ietf.org/wg/opsawg/
WG List: mailto:opsawg@ietf.org
Author: John Evans
<mailto:jevanamz@amazon.co.uk>
Author: Oleksandr Pylypenko
<mailto:opyl@amazon.com>
Author: Jeffrey Haas
<mailto:jhaas@juniper.net>
Author: Aviran Kadosh
<mailto:akadosh@cisco.com>
Author: Mohamed Boucadair
<mailto:mohamed.boucadair@orange.com>";
description
"This module defines an information model for packet discard
reporting.
Copyright (c) 2025 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Revised BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see the
RFC itself for full legal notices.";
revision 2024-06-04 {
description
"Initial revision.";
reference
"RFC XXXX: Information and Data Models for Packet Discard
Reporting";
}
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/*
* Features
*/
feature per-interface-stats {
description
"Indicates support of per-interface statistics on this
device.";
}
feature per-device-stats {
description
"Indicates support of global device statistics on this
device.";
}
feature control-plane-stats {
description
"Indicates support of control plane statistics on this
device.";
}
feature flow-reporting {
description
"Indicates support of flow reporting on this device";
}
/*
* Identities
*/
identity direction {
description
"Defines a direction for the reported statistics";
}
identity ingress {
base direction;
description
"Reports statistics for the received from the network
packets";
}
identity egress {
base direction;
description
"Reports statistics for the sent to the network
packets";
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}
identity address-family {
description
"Defines a type for the address family.";
}
identity ipv4 {
base address-family;
description
"Identity for an IPv4 address family.";
}
identity ipv6 {
base address-family;
description
"Identity for an IPv6 address family.";
}
identity all {
base address-family;
description
"Identity for all address families.";
}
/*
* Groupings
*/
grouping basic-packets-64 {
description
"Grouping for 64-bit Layer 3 packet counters.";
leaf packets {
type uint64;
description
"Number of Layer 3 packets.";
}
}
grouping basic-packets-bytes-64 {
description
"Grouping for 64-bit Layer 3 packet and byte
counters.";
uses basic-packets-64;
leaf bytes {
type uint64;
description
"Number of Layer 3 bytes.";
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}
}
grouping basic-frames-64 {
description
"Grouping for 64-bit Layer 2 frame counters.";
leaf frames {
type uint64;
description
"Number of Layer 2 frames.";
}
}
grouping basic-frames-bytes-64 {
description
"Grouping for 64-bit Layer 2 frame and byte
counters.";
uses basic-frames-64;
leaf bytes {
type uint64;
description
"Number of Layer 2 bytes.";
}
}
grouping basic-packets-32 {
description
"Grouping for 32-bit Layer 3 packet counters.";
leaf packets {
type uint32;
description
"Number of Layer 3 packets.";
}
}
grouping basic-packets-bytes-32 {
description
"Grouping for 32-bit Layer 3 packet and byte
counters.";
uses basic-packets-32;
leaf bytes {
type uint32;
description
"Number of Layer 3 bytes.";
}
}
grouping basic-frames-32 {
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description
"Grouping for 32-bit Layer 2 frame counters.";
leaf frames {
type uint32;
description
"Number of Layer 2 frames.";
}
}
grouping basic-frames-bytes-32 {
description
"Grouping for 32-bit Layer 2 frame and byte counters.";
uses basic-frames-32;
leaf bytes {
type uint32;
description
"Number of Layer 2 bytes.";
}
}
grouping l2-traffic {
description
"Layer 2 traffic counters.";
uses basic-frames-bytes-64;
}
grouping ip {
description
"Layer 3 traffic counters per address family.";
list address-family-stat {
key "address-family";
description
"Reports per address family traffic counters.";
leaf address-family {
type identityref {
base address-family;
}
description
"Specifies an address family.";
}
uses basic-packets-bytes-64;
container unicast {
description
"Unicast traffic counters.";
uses basic-packets-bytes-64;
}
container multicast {
description
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"Multicast traffic counters.";
uses basic-packets-bytes-64;
}
}
}
grouping l3-traffic {
description
"Layer 3 traffic counters.";
uses ip;
}
grouping qos {
description
"Quality of Service (QoS) traffic counters.";
list class {
key "id";
min-elements 1;
description
"QoS class traffic counters.";
leaf id {
type string;
description
"QoS class identifier.";
}
uses basic-packets-bytes-64;
}
}
grouping traffic {
description
"All traffic counters.";
container l2 {
description
"Layer 2 traffic counters.";
uses l2-traffic;
}
container l3 {
description
"Layer 3 traffic counters.";
uses l3-traffic;
}
container qos {
description
"QoS traffic counters.";
uses qos;
}
}
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grouping errors-l2-rx {
description
"Layer 2 ingress frame error discard counters.";
container rx {
description
"Layer 2 ingress frame receive error discard
counters.";
leaf frames {
type uint32;
description
"The number of frames discarded due to errors
with the received frame.";
}
leaf crc-error {
type uint32;
description
"The number of frames discarded due to CRC error.";
}
leaf invalid-mac {
type uint32;
description
"The number of frames discarded due to an invalid
MAC address.";
}
leaf invalid-vlan {
type uint32;
description
"The number of frames discarded due to an invalid
VLAN tag.";
}
leaf invalid-frame {
type uint32;
description
"The number of invalid frames discarded due to other
reasons, not limited to: malformed frames, frame-size
violations.";
}
}
}
grouping errors-l3-rx {
description
"Layer 3 ingress packet error discard counters.";
container rx {
description
"Layer 3 ingress packet receive error discard
counters.";
leaf packets {
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type uint32;
description
"The number of Layer 3 packets discarded due to
errors in the received packet.";
}
leaf checksum-error {
type uint32;
description
"The number of received packets discarded due
to a checksum error.";
}
leaf mtu-exceeded {
type uint32;
description
"The number of received packets discarded due to
MTU exceeded.";
}
leaf invalid-packet {
type uint32;
description
"The number of invalid packets discarded due to other
reasons, not limited to: invalid packet length, invalid
header fields, invalid options, invalid protocol version,
invalid flags or control bits, malformed packets.";
}
}
leaf ttl-expired {
type uint32;
description
"The number of received packets discarded due to
expired TTL.";
}
leaf no-route {
type uint32;
description
"The number of packets discarded due to not matching
a valid route.";
}
leaf invalid-sid {
type uint32;
description
"The number of packets discarded due to an invalid
Segment Routing (SR) SID.";
}
leaf invalid-label {
type uint32;
description
"The number of packets discarded due to an invalid
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MPLS label.";
}
}
grouping errors-l3-int {
description
"Internal error discard counters.";
leaf packets {
type uint32;
description
"The number of packets discarded due to internal
errors.";
}
leaf parity-error {
type uint32;
description
"The number of packets discarded due to parity
errors.";
}
}
grouping errors-l2-tx {
description
"Layer 2 transmit error discard counters.";
container tx {
description
"Layer 2 transmit frame error discard counters.";
leaf frames {
type uint32;
description
"The number of Layer 2 frames discarded due to
errors when transmitting.";
}
}
}
grouping errors-l3-tx {
description
"Layer 3 transmit error discard counters.";
container tx {
description
"Layer 3 transmit packet error discard counters.";
leaf packets {
type uint32;
description
"The number of Layer 3 packets discarded due to
errors when transmitting.";
}
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}
}
grouping errors {
description
"Error discard counters.";
container l2 {
description
"Layer 2 frame error discard counters.";
uses errors-l2-rx;
uses errors-l2-tx;
}
container l3 {
description
"Layer 3 packet error discard counters.";
uses errors-l3-rx;
uses errors-l3-tx;
}
container internal {
description
"Internal error discard counters.";
uses errors-l3-int;
}
}
grouping policy-l2 {
description
"Layer 2 policy frame discard counters.";
leaf frames {
type uint32;
description
"The number of Layer 2 frames discarded due
to policy.";
}
leaf acl {
type uint32;
description
"The number of frames discarded due to Layer 2 ACLs.";
}
}
grouping policy-l3 {
description
"Layer 3 policy packet discard counters.";
leaf packets {
type uint32;
description
"The number of Layer 3 packets discarded due to policy.";
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}
leaf acl {
type uint32;
description
"The number of packets discarded due to Layer 3 ACLs.";
}
container policer {
description
"The number of packets discarded due ingress
policer violations.";
uses basic-packets-bytes-32;
}
leaf null-route {
type uint32;
description
"The number of packets discarded due to matching
a null route.";
}
leaf rpf {
type uint32;
description
"The number of packets discarded due to failing
Reverse Path Forwarding (RPF) check.";
}
leaf ddos {
type uint32;
description
"The number of packets discarded due to DDoS
protection policies.";
}
}
grouping discards {
description
"Discard counters.";
container l2 {
description
"Ingress Layer 2 frame discard counters.";
uses l2-traffic;
}
container l3 {
description
"Ingress Layer 3 packet discard counters.";
uses l3-traffic;
}
container errors {
description
"Ingress error discard counters.";
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uses errors;
}
container policy {
description
"Ingress policy-related discard counters.";
uses policy;
}
container no-buffer {
description
"Ingress discard counters due to buffer
unavailability.";
uses qos;
}
}
grouping policy {
description
"Policy-related discard counters.";
container l2 {
description
"Layer 2 policy frame discard counters.";
uses policy-l2;
}
container l3 {
description
"Layer 3 policy packet discard counters.";
uses policy-l3;
}
}
grouping device {
description
"Device-level traffic and discard counters.";
container traffic {
description
"Traffic counters.";
uses traffic;
}
container discards {
description
"Discard counters.";
uses discards;
}
}
grouping interface {
description
"Interface-level traffic and discard counters.";
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list traffic {
key "direction";
description
"Traffic counters.";
leaf direction {
type identityref {
base direction;
}
description
"Specifies a direction.";
}
uses traffic;
}
list discards {
key "direction";
description
"Discard counters.";
leaf direction {
type identityref {
base direction;
}
description
"Specifies a direction.";
}
uses discards;
}
}
grouping control-plane {
description
"Control plane packet counters.";
list traffic {
key "direction";
description
"Total control plane packets.";
leaf direction {
type identityref {
base direction;
}
description
"Specifies a direction.";
}
uses basic-packets-bytes-32;
}
list discards {
key "direction";
description
"Control plane packet discard counters.";
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leaf direction {
type identityref {
base direction;
}
description
"Specifies a direction.";
}
uses basic-packets-bytes-32;
container policy {
description
"Number of control plane packets discarded due to policy.";
uses basic-packets-32;
}
}
}
/*
* Main structure definition
*/
sx:structure packet-discard-reporting {
description
"Specifies the abstract structure of packet discard
reporting data.";
container control-plane {
if-feature "control-plane-stats";
description
"Control plane packet counters.";
uses control-plane;
}
list interface {
if-feature "per-interface-stats";
key "name";
description
"Indicates a list of interfaces for which packet
discard reporting data is provided.";
leaf name {
type string;
description
"Indicates the name of the interface.";
}
uses interface;
}
list flow {
if-feature "flow-reporting";
key "direction";
leaf direction {
type identityref {
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base direction;
}
description
"Specifies a direction.";
}
description
"Flow packet counters.";
uses device;
}
container device {
if-feature "per-device-stats";
description
"Device level packet counters.";
uses device;
}
}
}
<CODE ENDS>
5. Data Model
This data model implements the information model defined in Section 4
for the interface and device components. This is classed as a
Network Element model as defined by [RFC1157].
5.1. Structure
There is a direct mapping between the information model components
and their data model implementations, with each component in the
hierarchy represented by corresponding YANG containers and leaves.
The following YANG tree diagram shows the complete structure:
module: ietf-packet-discard-reporting
+--rw interface* [name] {per-interface-stats}?
| +--rw name string
| +--rw traffic* [direction]
| | +--rw direction identityref
| | +--rw l2
| | | +--rw frames? uint64
| | | +--rw bytes? uint64
| | +--rw l3
| | | +--rw address-family-stat* [address-family]
| | | +--rw address-family identityref
| | | +--rw packets? uint64
| | | +--rw bytes? uint64
| | | +--rw unicast
| | | | +--rw packets? uint64
| | | | +--rw bytes? uint64
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| | | +--rw multicast
| | | +--rw packets? uint64
| | | +--rw bytes? uint64
| | +--rw qos
| | +--rw class* [id]
| | +--rw id string
| | +--rw packets? uint64
| | +--rw bytes? uint64
| +--rw discards* [direction]
| +--rw direction identityref
| +--rw l2
| | +--rw frames? uint64
| | +--rw bytes? uint64
| +--rw l3
| | +--rw address-family-stat* [address-family]
| | +--rw address-family identityref
| | +--rw packets? uint64
| | +--rw bytes? uint64
| | +--rw unicast
| | | +--rw packets? uint64
| | | +--rw bytes? uint64
| | +--rw multicast
| | +--rw packets? uint64
| | +--rw bytes? uint64
| +--rw errors
| | +--rw l2
| | | +--rw rx
| | | | +--rw frames? uint32
| | | | +--rw crc-error? uint32
| | | | +--rw invalid-mac? uint32
| | | | +--rw invalid-vlan? uint32
| | | | +--rw invalid-frame? uint32
| | | +--rw tx
| | | +--rw frames? uint32
| | +--rw l3
| | | +--rw rx
| | | | +--rw packets? uint32
| | | | +--rw checksum-error? uint32
| | | | +--rw mtu-exceeded? uint32
| | | | +--rw invalid-packet? uint32
| | | +--rw ttl-expired? uint32
| | | +--rw no-route? uint32
| | | +--rw invalid-sid? uint32
| | | +--rw invalid-label? uint32
| | | +--rw tx
| | | +--rw packets? uint32
| | +--rw internal
| | +--rw packets? uint32
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| | +--rw parity-error? uint32
| +--rw policy
| | +--rw l2
| | | +--rw frames? uint32
| | | +--rw acl? uint32
| | +--rw l3
| | +--rw packets? uint32
| | +--rw acl? uint32
| | +--rw policer
| | | +--rw packets? uint32
| | | +--rw bytes? uint32
| | +--rw null-route? uint32
| | +--rw rpf? uint32
| | +--rw ddos? uint32
| +--rw no-buffer
| +--rw class* [id]
| +--rw id string
| +--rw packets? uint64
| +--rw bytes? uint64
+--rw device! {per-device-stats}?
+--rw traffic
| +--rw l2
| | +--rw frames? uint64
| | +--rw bytes? uint64
| +--rw l3
| | +--rw address-family-stat* [address-family]
| | +--rw address-family identityref
| | +--rw packets? uint64
| | +--rw bytes? uint64
| | +--rw unicast
| | | +--rw packets? uint64
| | | +--rw bytes? uint64
| | +--rw multicast
| | +--rw packets? uint64
| | +--rw bytes? uint64
| +--rw qos
| +--rw class* [id]
| +--rw id string
| +--rw packets? uint64
| +--rw bytes? uint64
+--rw discards
+--rw l2
| +--rw frames? uint64
| +--rw bytes? uint64
+--rw l3
| +--rw address-family-stat* [address-family]
| +--rw address-family identityref
| +--rw packets? uint64
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| +--rw bytes? uint64
| +--rw unicast
| | +--rw packets? uint64
| | +--rw bytes? uint64
| +--rw multicast
| +--rw packets? uint64
| +--rw bytes? uint64
+--rw errors
| +--rw l2
| | +--rw rx
| | | +--rw frames? uint32
| | | +--rw crc-error? uint32
| | | +--rw invalid-mac? uint32
| | | +--rw invalid-vlan? uint32
| | | +--rw invalid-frame? uint32
| | +--rw tx
| | +--rw frames? uint32
| +--rw l3
| | +--rw rx
| | | +--rw packets? uint32
| | | +--rw checksum-error? uint32
| | | +--rw mtu-exceeded? uint32
| | | +--rw invalid-packet? uint32
| | +--rw ttl-expired? uint32
| | +--rw no-route? uint32
| | +--rw invalid-sid? uint32
| | +--rw invalid-label? uint32
| | +--rw tx
| | +--rw packets? uint32
| +--rw internal
| +--rw packets? uint32
| +--rw parity-error? uint32
+--rw policy
| +--rw l2
| | +--rw frames? uint32
| | +--rw acl? uint32
| +--rw l3
| +--rw packets? uint32
| +--rw acl? uint32
| +--rw policer
| | +--rw packets? uint32
| | +--rw bytes? uint32
| +--rw null-route? uint32
| +--rw rpf? uint32
| +--rw ddos? uint32
+--rw no-buffer
+--rw class* [id]
+--rw id string
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+--rw packets? uint64
+--rw bytes? uint64
5.2. Implementation Requirements
The following requirements apply to the implementation of the data
model and are intended to ensure consistent implementation across
different vendors and platforms while allowing for platform-specific
optimisations where needed. While the model defines a comprehensive
set of counters and statistics, implementations MAY support a subset
of the defined features based on device capabilities and operational
requirements. However, implementations MUST clearly document which
features are supported and how they map to the model.
Requirements 1-10 relate to packets forwarded or discarded by the
device, while requirement 11 relates to packets destined for or
originating from the device:
1. All instances of Layer 2 frame or Layer 3 packet receipt,
transmission, and discards MUST be accounted for.
2. All instances of Layer 2 frame or Layer 3 packet receipt,
transmission, and discards SHOULD be attributed to the physical
or logical interface of the device where they occur. Where they
cannot be attributed to the interface, they MUST be attributed
to the device.
3. An individual frame MUST only be accounted for by either the
Layer 2 traffic class or the Layer 2 discard classes within a
single direction or context, i.e., ingress or egress or device.
This is to avoid double counting.
4. An individual packet MUST only be accounted for by either the
Layer 3 traffic class or the Layer 3 discard classes within a
single direction or context, i.e., ingress or egress or device.
This is to avoid double counting.
5. A frame accounted for at Layer 2 SHOULD NOT be accounted for at
Layer 3 and vice versa. An implementation MUST indicate which
layers traffic and discards are counted against. This is to
avoid double counting.
6. The aggregate Layer 2 and Layer 3 traffic and discard classes
SHOULD account for all underlying frames or packets received,
transmitted, and discarded across all other classes.
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7. The aggregate Quality of Service (QoS) traffic and no buffer
discard classes MUST account for all underlying packets
received, transmitted, and discarded across all other classes.
8. In addition to the Layer 2 and Layer 3 aggregate classes, an
individual discarded packet MUST only account against a single
error, policy, or no-buffer discard subclass.
9. When there are multiple reasons for discarding a packet, the
ordering of discard class reporting MUST be defined.
10. If Diffserv [RFC2475] is not used, no-buffer discards SHOULD be
reported as class0, which represents the default class.
11. Traffic to the device control plane has its own class, however,
traffic from the device control plane SHOULD be accounted for in
the same way as other egress traffic.
5.3. Usage Examples
If all of the requirements are met, a "good" unicast IPv4 packet
received would increment:
* interface/ingress/traffic/l3/v4/unicast/packets
* interface/ingress/traffic/l3/v4/unicast/bytes
* interface/ingress/traffic/qos/class_0/packets
* interface/ingress/traffic/qos/class_0/bytes
A received unicast IPv6 packet discarded due to Hop Limit expiry
would increment:
* interface/ingress/discards/l3/v6/unicast/packets
* interface/ingress/discards/l3/v6/unicast/bytes
* interface/ingress/discards/l3/rx/ttl-expired/packets
An IPv4 packet discarded on egress due to no buffers would increment:
* interface/egress/discards/l3/v4/unicast/packets
* interface/egress/discards/l3/v4/unicast/bytes
* interface/egress/discards/no-buffer/class_0/packets
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* interface/egress/discards/no-buffer/class_0/bytes
A multicast IPv6 packet dropped due to RPF check failure would
increment:
* interface/ingress/discards/l3/v6/multicast/packets
* interface/ingress/discards/l3/v6/multicast/bytes
* interface/ingress/discards/policy/l3/rpf/packets
5.4. Data model - YANG Module
<CODE BEGINS>
module ietf-packet-discard-reporting {
yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:ietf-packet-discard-reporting";
prefix plr;
import ietf-packet-discard-reporting-sx {
prefix plr-sx;
reference
"RFC XXXX: Information and Data Models for Packet Discard
Reporting";
}
organization
"IETF OPSAWG (Operations and Management Area Working Group)";
contact
"WG Web: https://datatracker.ietf.org/wg/opsawg/
WG List: mailto:opsawg@ietf.org
Author: John Evans
<mailto:jevanamz@amazon.co.uk>
Author: Oleksandr Pylypenko
<mailto:opyl@amazon.com>
Author: Jeffrey Haas
<mailto:jhaas@juniper.net>
Author: Aviran Kadosh
<mailto:akadosh@cisco.com>
Author: Mohamed Boucadair
<mailto:mohamed.boucadair@orange.com>";
description
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"This module defines a data model for packet discard reporting.
Copyright (c) 2025 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Revised BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see the
RFC itself for full legal notices.";
revision 2025-03-03 {
description
"Initial revision.";
reference
"RFC XXXX: Information and Data Models for Packet Discard
Reporting";
}
/*
* Features
*/
feature per-interface-stats {
description
"Indicates support of per-interface statistics on this
device.";
}
feature per-device-stats {
description
"Indicates support of global device statistics on this
device.";
}
/*
* Main structure definition
*/
/**TO DO: Need to find where to graft the reporting***/
list interface {
if-feature "per-interface-stats";
key "name";
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description
"Indicates a list of interfaces for which packet discard
reporting data is provided.";
leaf name {
type string;
description
"Indicates the name of the interface.";
}
uses plr-sx:interface;
}
container device {
if-feature "per-device-stats";
presence "Device-level statistics are available.";
description
"Device level packet counters.";
uses plr-sx:device;
}
}
<CODE ENDS>
6. Security Considerations
This section discusses security considerations for both the
information model and its implementation as a data model.
6.1. Information Model
The information model defined in Section 4.3 specifies a YANG module
using [RFC8791] data extensions. It defines a set of identities,
types, and groupings. These nodes are intended to be reused by other
YANG modules. The module by itself does not expose any data nodes
that are writable, data nodes that contain read-only state, or RPCs.
As such, there are no additional security issues related to the YANG
module that need to be considered.
6.2. Data Model
This section is modeled after the template described in Section 3.7
of [I-D.ietf-netmod-rfc8407bis].
The YANG module specified in Section 5.4 defines a data model that is
designed to be accessed via YANG-based management protocols, such as
NETCONF [RFC6241] and RESTCONF [RFC8040]. These protocols have to
use a secure transport layer (e.g., SSH [RFC4252], TLS [RFC8446], and
QUIC [RFC9000]) and have to use mutual authentication.
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The Network Configuration Access Control Model (NACM) [RFC8341]
provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or
RESTCONF protocol operations and content.
There are a number of data nodes defined in this YANG module that are
writable/creatable/deletable (i.e., "config true", which is the
default). All writable data nodes are likely to be reasonably
sensitive or vulnerable in some network environments. Write
operations (e.g., edit-config) and delete operations to these data
nodes without proper protection or authentication can have a negative
effect on network operations. The following subtrees and data nodes
have particular sensitivities/vulnerabilities:
interfaces: TBC
devices: tbc
7. IANA Considerations
IANA is requested to register the following URI in the "ns"
subregistry within the "IETF XML Registry" [RFC3688]:
URI: urn:ietf:params:xml:ns:ietf-packet-discard-reporting-sx
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:ietf-packet-discard-reporting
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
IANA is requested to register the following YANG module in the "YANG
Module Names" subregistry [RFC6020] within the "YANG Parameters"
registry:
Name: ietf-packet-discard-reporting-sx
Namespace: urn:ietf:params:xml:ns:ietf-packet-discard-reporting-sx
Prefix: plr-sx
Maintained by IANA? N
Reference: RFC XXXX
Name: ietf-packet-discard-reporting
Namespace: urn:ietf:params:xml:ns:ietf-packet-discard-reporting
Prefix: plr
Maintained by IANA? N
Reference: RFC XXXX
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8. Contributors
Nadav Chachmon
Cisco Systems, Inc.
170 West Tasman Dr.
San Jose, CA 95134
United States of America
Email: nchachmo@cisco.com
9. Acknowledgments
The content of this document has benefitted from feedback from JR
Rivers, Ronan Waide, Chris DeBruin, and Marcoz Sanz.
10. References
10.1. 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/rfc/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/rfc/rfc3688>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/rfc/rfc6020>.
[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/rfc/rfc8174>.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/rfc/rfc8341>.
[RFC8791] Bierman, A., Björklund, M., and K. Watsen, "YANG Data
Structure Extensions", RFC 8791, DOI 10.17487/RFC8791,
June 2020, <https://www.rfc-editor.org/rfc/rfc8791>.
10.2. Informative References
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[gMNI] Marrow, C., "gRPC Network Management Interface, IETF 98,
March 2017,
<https://datatracker.ietf.org/meeting/98/materials/slides-
98-rtgwg-gnmi-intro-draft-openconfig-rtgwg-gnmi-spec-00>",
n.d..
[I-D.ietf-netmod-rfc8407bis]
Bierman, A., Boucadair, M., and Q. Wu, "Guidelines for
Authors and Reviewers of Documents Containing YANG Data
Models", Work in Progress, Internet-Draft, draft-ietf-
netmod-rfc8407bis-22, 14 January 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
rfc8407bis-22>.
[RED93] Jacobson, V., "Random Early Detection gateways for
Congestion Avoidance", n.d..
[RFC1157] Case, J., Fedor, M., Schoffstall, M., and J. Davin,
"Simple Network Management Protocol (SNMP)", RFC 1157,
DOI 10.17487/RFC1157, May 1990,
<https://www.rfc-editor.org/rfc/rfc1157>.
[RFC1213] McCloghrie, K. and M. Rose, "Management Information Base
for Network Management of TCP/IP-based internets: MIB-II",
STD 17, RFC 1213, DOI 10.17487/RFC1213, March 1991,
<https://www.rfc-editor.org/rfc/rfc1213>.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<https://www.rfc-editor.org/rfc/rfc2475>.
[RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
Information Models and Data Models", RFC 3444,
DOI 10.17487/RFC3444, January 2003,
<https://www.rfc-editor.org/rfc/rfc3444>.
[RFC4252] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
January 2006, <https://www.rfc-editor.org/rfc/rfc4252>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/rfc/rfc6241>.
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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/rfc/rfc7011>.
[RFC7270] Yourtchenko, A., Aitken, P., and B. Claise, "Cisco-
Specific Information Elements Reused in IP Flow
Information Export (IPFIX)", RFC 7270,
DOI 10.17487/RFC7270, June 2014,
<https://www.rfc-editor.org/rfc/rfc7270>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/rfc/rfc8040>.
[RFC8289] Nichols, K., Jacobson, V., McGregor, A., Ed., and J.
Iyengar, Ed., "Controlled Delay Active Queue Management",
RFC 8289, DOI 10.17487/RFC8289, January 2018,
<https://www.rfc-editor.org/rfc/rfc8289>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/rfc/rfc8340>.
[RFC8343] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
<https://www.rfc-editor.org/rfc/rfc8343>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/rfc/rfc8446>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/rfc/rfc9000>.
Appendix A. Where do packets get dropped?
Understanding where packets are discarded in a network device is
essential for interpreting discard signals and determining
appropriate mitigation actions. Figure 1 depicts an example of where
and why packets may be discarded in a typical single-ASIC, shared-
buffered type device. While actual device architectures vary between
vendors and platforms, with some using multiple ASICs, distributed
forwarding, or different buffering architectures, this example
illustrates the common processing stages where packets may be
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dropped. The logical model for classifying and reporting discards
remains consistent regardless of the underlying hardware
architecture.
Packets ingress on the left and egress on the right:
+----------+
| |
| CPU |
| |
+--+---^---+
from_cpu | | to_cpu
| |
+------------------------------v---+-------------------------------+
| |
+----------+ +----------+ +----------+ +----------+ +----------+ +----------+ +----------+
| | | | | | | | | | | | | |
Packet rx -> Phy +--> Mac +--> Ingress +--> Buffers +--> Egresss +--> Mac +--> Phy +-> Packet tx
| | | | | Pipeline| | | | Pipeline| | | | |
+----------+ +----------+ +----------+ +----------+ +----------+ +----------+ +----------+
Intended policy/acl policy/acl
Discards: policy/policer policy/policer
policy/urpf
policy/null-route
Unintended error/rx/l2 error/l3/rx no-buffer error/l3/tx
Discards: error/local
error/l3/no-route
error/l3/rx/ttl-expired
Figure 1: Example of where packets get dropped
See Appendix B for examples of how these discard signals map to root
causes and mitigation actions.
Appendix B. Example signal-to-mitigation action mapping
The effectiveness of automated mitigation depends on correctly
mapping discard signals to root causes and appropriate actions.
Table 1 gives example discard signal-to-mitigation action mappings
based on the features described in section 3.
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+==============================+===========+==========+========+===========+========+
|DISCARD-CLASS |Discard |DISCARD- |DISCARD-|Unintended?|Possible|
| |cause |RATE |DURATION| |actions |
+==============================+===========+==========+========+===========+========+
|ingress/discards/errors/l2/rx |Upstream |>Baseline |O(1min) | Y |Take |
| |device or | | | |upstream|
| |link error | | | |link or |
| | | | | |device |
| | | | | |out-of- |
| | | | | |service |
+------------------------------+-----------+----------+--------+-----------+--------+
|ingress/discards/errors/l3/rx/|Tracert |<=Baseline| | N |no |
|ttl-expired | | | | |action |
+------------------------------+-----------+----------+--------+-----------+--------+
|ingress/discards/errors/l3/rx/|Convergence|>Baseline | O(1s) | Y |No |
|ttl-expired | | | | |action |
+------------------------------+-----------+----------+--------+-----------+--------+
|ingress/discards/errors/l3/rx/|Routing |>Baseline |O(1min) | Y |Roll- |
|ttl-expired |loop | | | |back |
| | | | | |change |
+------------------------------+-----------+----------+--------+-----------+--------+
|.*/policy/.* |Policy | | | N |No |
| | | | | |action |
+------------------------------+-----------+----------+--------+-----------+--------+
|ingress/discards/errors/l3/no-|Convergence|>Baseline | O(1s) | Y |No |
|route | | | | |action |
+------------------------------+-----------+----------+--------+-----------+--------+
|ingress/discards/errors/l3/no-|Config |>Baseline |O(1min) | Y |Roll- |
|route |error | | | |back |
| | | | | |change |
+------------------------------+-----------+----------+--------+-----------+--------+
|ingress/discards/errors/l3/no-|Invalid |>Baseline |O(10min)| N |Escalate|
|route |destination| | | |to |
| | | | | |operator|
+------------------------------+-----------+----------+--------+-----------+--------+
|ingress/discards/errors/local |Device |>Baseline |O(1min) | Y |Take |
| |errors | | | |device |
| | | | | |out-of- |
| | | | | |service |
+------------------------------+-----------+----------+--------+-----------+--------+
|egress/discards/no-buffer |Congestion |<=Baseline| | N |No |
| | | | | |action |
+------------------------------+-----------+----------+--------+-----------+--------+
|egress/discards/no-buffer |Congestion |>Baseline |O(1min) | Y |Bring |
| | | | | |capacity|
| | | | | |back |
| | | | | |into |
| | | | | |service |
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| | | | | |or move |
| | | | | |traffic |
+------------------------------+-----------+----------+--------+-----------+--------+
Table 1: Example Signal-Cause-Mitigation Mapping
The 'Baseline' in the 'DISCARD-RATE' column is both DISCARD-CLASS and
network dependent.
Appendix C. Implementation Experience
This appendix captures practical insights gained from implementing
this information model across multiple vendors' platforms, as
guidance for future implementers.
1. The number and granularity of discard classes defined in the
information model represent a compromise. It aims to provide
sufficient detail to enable appropriate automated actions while
avoiding excessive detail, which may hinder quick problem
identification. Additionally, it helps to limit the quantity of
data produced per interface, constraining the data volume and
device CPU impacts. While further granularity is possible, the
defined schema has generally proven to be sufficient for the
task of mitigating unintended packet loss.
2. There are many possible ways to define the discard
classification tree. For example, we could have used a multi-
rooted tree, rooted in each protocol. Instead, we opted to
define a tree where protocol discards and causal discard classes
are accounted for orthogonally. This decision reduces the
number of combinations of classes and has proven sufficient for
determining mitigation actions.
3. NoBuffer discards can be realized differently with different
memory architectures. Whether a NoBuffer discard is attributed
to ingress or egress can differ accordingly. For successful
auto-mitigation, discards due to egress interface congestion
should be reported on egress, while discards due to device-level
congestion (e.g. due to exceeding the device forwarding rate)
should be reported on ingress.
4. Platforms often account for the number of packets discarded
where the TTL has expired (or Hop Limit exceeded), and the
device CPU has returned an ICMP Time Exceeded message. There is
typically a policer applied to limit the number of packets sent
to the device CPU, however, which implicitly limits the rate of
TTL discards that are processed. One method to account for all
packet discards due to TTL expired, even those that are dropped
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by a policer when being forwarded to the CPU, is to use
accounting of all ingress packets received with TTL=1 as a proxy
measure.
5. Where no route discards are implemented with a default null
route, separate discard accounting is required for any explicit
null routes configured, in order to differentiate between
interface/ingress/discards/policy/null-route/packets and
interface/ingress/discards/errors/no-route/packets.
6. It is useful to account separately for transit packets discarded
by ACLs or policers, and packets discarded by ACLs or policers
which limit the number of packets to the device control plane.
7. It is not possible to identify a configuration error - e.g.,
when intended discards are unintended - with device discard
metrics alone. For example, additional context is needed to
determine if ACL discards are intended or due to a misconfigured
ACL, i.e., with configuration validation before deployment or by
detecting a significant change in ACL discards after a
configuration change compared to before.
8. Where traffic byte counters need to be 64-bit, packet and
discard counters that increase at a lower rate may be encoded in
32-bit.
9. Aggregate counters need to be able to deal with the possibility
of discontinuities in the underlying counters.
10. In cases where the reporting device is the source or destination
of a tunnel, the ingress protocol for a packet may differ from
the egress protocol; if IPv4 is tunnelled over IPv6 for example.
Some implementations may attribute egress discards to the
ingress protocol.
11. While the classification tree is seven layers deep, a minimal
implementation may only implement the top six layers.
Authors' Addresses
John Evans
Amazon
1 Principal Place, Worship Street
London
EC2A 2FA
United Kingdom
Email: jevanamz@amazon.co.uk
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Oleksandr Pylypenko
Amazon
410 Terry Ave N
Seattle, WA 98109
United States of America
Email: opyl@amazon.com
Jeffrey Haas
Juniper Networks
1133 Innovation Way
Sunnyvale, CA 94089
United States of America
Email: jhaas@juniper.net
Aviran Kadosh
Cisco Systems, Inc.
170 West Tasman Dr.
San Jose, CA 95134
United States of America
Email: akadosh@cisco.com
Mohamed Boucadair
Orange
France
Email: mohamed.boucadair@orange.com
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