Internet DRAFT - draft-brockners-opsawg-ioam-deployment
draft-brockners-opsawg-ioam-deployment
opsawg F. Brockners
Internet-Draft Cisco
Intended status: Best Current Practice S. Bhandari, Ed.
Expires: December 26, 2021 Thoughtspot
D. Bernier
Bell Canada
T. Mizrahi, Ed.
Huawei
June 24, 2021
In-situ OAM Deployment
draft-brockners-opsawg-ioam-deployment-03
Abstract
In-situ Operations, Administration, and Maintenance (IOAM) records
operational and telemetry information in the packet while the packet
traverses a path between two points in the network. This document
provides a framework for IOAM deployment and provides best current
practices.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. IOAM Deployment: Domains And Nodes . . . . . . . . . . . . . 4
4. Types of IOAM . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Per-hop Tracing IOAM . . . . . . . . . . . . . . . . . . 6
4.2. Proof of Transit IOAM . . . . . . . . . . . . . . . . . . 8
4.3. Edge to Edge IOAM . . . . . . . . . . . . . . . . . . . . 8
4.4. Direct Export IOAM . . . . . . . . . . . . . . . . . . . 8
5. IOAM Encapsulations . . . . . . . . . . . . . . . . . . . . . 8
5.1. IPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.2. NSH . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.3. GRE . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.4. Geneve . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.5. Segment Routing . . . . . . . . . . . . . . . . . . . . . 10
5.6. Segment Routing for IPv6 . . . . . . . . . . . . . . . . 10
5.7. VXLAN-GPE . . . . . . . . . . . . . . . . . . . . . . . . 10
6. IOAM Data Export . . . . . . . . . . . . . . . . . . . . . . 10
7. IOAM Deployment Considerations . . . . . . . . . . . . . . . 11
7.1. IOAM Namespaces . . . . . . . . . . . . . . . . . . . . . 12
7.2. IOAM Layering . . . . . . . . . . . . . . . . . . . . . . 13
7.3. IOAM Trace Option Types . . . . . . . . . . . . . . . . . 14
7.4. Traffic-sets That IOAM Is Applied To . . . . . . . . . . 16
7.5. IOAM Loopback Mode . . . . . . . . . . . . . . . . . . . 16
7.6. IOAM Active Mode . . . . . . . . . . . . . . . . . . . . 16
7.7. Brown Field Deployments: IOAM Unaware Nodes . . . . . . . 17
8. IOAM Manageability . . . . . . . . . . . . . . . . . . . . . 17
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
10. Security Considerations . . . . . . . . . . . . . . . . . . . 18
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
12.1. Normative References . . . . . . . . . . . . . . . . . . 19
12.2. Informative References . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23
1. Introduction
"In-situ" Operations, Administration, and Maintenance (IOAM) records
OAM information within the packet while the packet traverses a
particular network domain. The term "in-situ" refers to the fact
that the OAM data is added to the data packets rather than is being
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sent within packets specifically dedicated to OAM. IOAM is to
complement mechanisms such as Ping, Traceroute, or other active
probing mechanisms. In terms of "active" or "passive" OAM, "in-situ"
OAM can be considered a hybrid OAM type. "In-situ" mechanisms do not
require extra packets to be sent. IOAM adds information to the
already available data packets and therefore cannot be considered
passive. In terms of the classification given in [RFC7799] IOAM
could be portrayed as Hybrid Type 1. IOAM mechanisms can be
leveraged where mechanisms using e.g. ICMP do not apply or do not
offer the desired results, such as proving that a certain traffic
flow takes a pre-defined path, SLA verification for the live data
traffic, detailed statistics on traffic distribution paths in
networks that distribute traffic across multiple paths, or scenarios
in which probe traffic is potentially handled differently from
regular data traffic by the network devices.
2. Conventions
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.
Abbreviations used in this document:
E2E Edge to Edge
Geneve: Generic Network Virtualization Encapsulation
[I-D.ietf-nvo3-geneve]
GRE Generic Routing Encapsulation
IOAM: In-situ Operations, Administration, and Maintenance
MTU: Maximum Transmit Unit
NSH: Network Service Header [RFC8300]
OAM: Operations, Administration, and Maintenance
POT: Proof of Transit
SFC: Service Function Chain
SID: Segment Identifier
SR: Segment Routing
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VXLAN-GPE: Virtual eXtensible Local Area Network, Generic Protocol
Extension [I-D.ietf-nvo3-vxlan-gpe]
3. IOAM Deployment: Domains And Nodes
IOAM is a network domain specific feature, with "network domain"
being a set of network devices or entities within a single
administration. IOAM is not targeted for a deployment on the global
Internet. The part of the network which employs IOAM is referred to
as the "IOAM-Domain". For example, an IOAM-domain can include an
enterprise campus using physical connections between devices or an
overlay network using virtual connections / tunnels for connectivity
between said devices. An IOAM-domain is defined by its perimeter or
edge. The operator of an IOAM-domain is expected to put provisions
in place to ensure that packets which contain IOAM data fields do not
leak beyond the edge of an IOAM domain, e.g. using for example packet
filtering methods. The operator should consider the potential
operational impact of IOAM to mechanisms such as ECMP processing
(e.g. load-balancing schemes based on packet length could be impacted
by the increased packet size due to IOAM), path MTU (i.e. ensure that
the MTU of all links within a domain is sufficiently large to support
the increased packet size due to IOAM) and ICMP message handling.
An IOAM-Domain consists of "IOAM encapsulating nodes", "IOAM
decapsulating nodes" and "IOAM transit nodes". The role of a node
(i.e. encapsulating, transit, decapsulating) is defined within an
IOAM-Namespace (see below). A node can have different roles in
different IOAM-Namespaces.
An "IOAM encapsulating node" incorporates one or more IOAM-Option-
Types into packets that IOAM is enabled for. If IOAM is enabled for
a selected subset of the traffic, the IOAM encapsulating node is
responsible for applying the IOAM functionality to the selected
subset.
An "IOAM transit node" updates one or more of the IOAM-Data-Fields.
If both the Pre-allocated and the Incremental Trace Option-Types are
present in the packet, each IOAM transit node will update at most one
of these Option-Types. A transit node does not add new IOAM-Option-
Types to a packet, and does not change the IOAM-Data-Fields of an
IOAM Edge-to-Edge Option-Type.
An "IOAM decapsulating node" removes IOAM-Option-Type(s) from
packets.
The role of an IOAM-encapsulating, IOAM-transit or IOAM-decapsulating
node is always performed within a specific IOAM-Namespace. This
means that an IOAM node which is e.g. an IOAM-decapsulating node for
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IOAM-Namespace "A" but not for IOAM-Namespace "B" will only remove
the IOAM-Option-Types for IOAM-Namespace "A" from the packet. An
IOAM decapsulating node situated at the edge of an IOAM domain
removes all IOAM-Option-Types and associated encapsulation headers
for all IOAM-Namespaces from the packet.
IOAM-Namespaces allow for a namespace-specific definition and
interpretation of IOAM-Data-Fields. An interface-id could for
example point to a physical interface (e.g., to understand which
physical interface of an aggregated link is used when receiving or
transmitting a packet) whereas in another case it could refer to a
logical interface (e.g., in case of tunnels). Please refer to
Section 7.1 for a discussion of IOAM-Namespaces.
Export of Export of Export of Export of
IOAM data IOAM data IOAM data IOAM data
(optional) (optional) (optional) (optional)
^ ^ ^ ^
| | | |
| | | |
User +---+----+ +---+----+ +---+----+ +---+----+
packets |Encapsu-| | Transit| | Transit| |Decapsu-|
-------->|lating |====>| Node |====>| Node |====>|lating |-->
|Node | | A | | B | |Node |
+--------+ +--------+ +--------+ +--------+
Figure 1: Roles of IOAM nodes
IOAM nodes which add or remove the IOAM-Data-Fields can also update
the IOAM-Data-Fields at the same time. Or in other words, IOAM
encapsulating or decapsulating nodes can also serve as IOAM transit
nodes at the same time. Note that not every node in an IOAM domain
needs to be an IOAM transit node. For example, a deployment might
require that packets traverse a set of firewalls which support IOAM.
In that case, only the set of firewall nodes would be IOAM transit
nodes rather than all nodes.
4. Types of IOAM
IOAM supports different modes of operation, which are differentiated
by the type of IOAM data fields being carried in the packet, the data
being collected, the type of nodes which collect or update data as
well as whether and how nodes export IOAM information.
o Per-hop tracing: OAM information about each IOAM node a packet
traverses is collected and stored within the user data packet as
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the packet progresses through the IOAM domain. Potential uses of
IOAM per-hop tracing include:
* Optimization: Understand the different paths different packets
traverse between a source and a sink in a network that uses
load balancing such as Equal Cost Load Balancing (ECMP). This
information could be used to tune the algorithm for ECMP for
optimized network resource usage.
* Operations/Troubleshooting: Understand which path a particular
packet or set of packets take as well as what amount of jitter
and delay different nodes in the path contribute to the overall
end-to-end delay and jitter.
o Proof-of-transit: Information that a verifier node can use to
verify whether a packet has traversed all nodes that is supposed
to traverse is stored within the user data packet. Proof-of-
transit could for example be used to verify that a packet indeed
passes through all services of a service function chain (e.g.
verify whether a packet indeed traversed the set of firewalls that
it is expected to traverse), or whether a packet indeed took the
expected path.
o Edge-to-edge: OAM information which is specific to the edges of an
IOAM domain is collected and stored within the user data packet.
Edge-to-Edge OAM could be used to gather operational information
about a particular network domain, such as the delay and jitter
incurred by that network domain or the traffic matrix of the
network domain.
o Direct export: OAM information about each IOAM node a packet
traverses is collected and immediately exported to a collector.
Direct export could be used in situations where per-hop tracing
information is desired, but gathering the information within the
packet - as with per-hop tracing - is not feasible. Rather than
automatically correlating the per-hop tracing information, as done
with per-hop tracing, direct export requires a collector to
correlate the information from the individual nodes. In addition,
all nodes enabled for direct export need to be capable to export
the IOAM information to the collector.
4.1. Per-hop Tracing IOAM
"IOAM tracing data" is expected to be collected at every IOAM transit
node that a packet traverses to ensure visibility into the entire
path a packet takes within an IOAM-Domain. I.e., in a typical
deployment all nodes in an IOAM-Domain would participate in IOAM and
thus be IOAM transit nodes, IOAM encapsulating or IOAM decapsulating
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nodes. If not all nodes within a domain are IOAM capable, IOAM
tracing information (i.e., node data, see below) will only be
collected on those nodes which are IOAM capable. Nodes which are not
IOAM capable will forward the packet without any changes to the IOAM-
Data-Fields. The maximum number of hops and the minimum path MTU of
the IOAM domain is assumed to be known.
IOAM offers two different trace Option-Types, the "incremental"
Option-Type as well as the "pre-allocated" Option-Type. For a
discussion which of the two option types is the most suitable for an
implementation and/or deployment, see Section 7.3.
Every node data entry holds information for a particular IOAM transit
node that is traversed by a packet. The IOAM decapsulating node
removes the IOAM-Option-Type(s) and processes and/or exports the
associated data. All IOAM-Data-Fields are defined in the context of
an IOAM-Namespace.
IOAM tracing can collect the following types of information:
o Identification of the IOAM node. An IOAM node identifier can
match to a device identifier or a particular control point or
subsystem within a device.
o Identification of the interface that a packet was received on,
i.e. ingress interface.
o Identification of the interface that a packet was sent out on,
i.e. egress interface.
o Time of day when the packet was processed by the node as well as
the transit delay. Different definitions of processing time are
feasible and expected, though it is important that all devices of
an in-situ OAM domain follow the same definition.
o Generic data: Format-free information where syntax and semantic of
the information is defined by the operator in a specific
deployment. For a specific IOAM-Namespace, all IOAM nodes should
interpret the generic data the same way. Examples for generic
IOAM data include geo-location information (location of the node
at the time the packet was processed), buffer queue fill level or
cache fill level at the time the packet was processed, or even a
battery charge level.
o Information to detect whether IOAM trace data was added at every
hop or whether certain hops in the domain weren't IOAM transit
nodes.
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o Data that relates to how the packet traversed a node (transit
delay, buffer occupancy in case the packet was buffered, queue
depth in case the packet was queued)
The Option-Types of incremental tracing and pre-allocated tracing are
defined in [I-D.ietf-ippm-ioam-data].
4.2. Proof of Transit IOAM
IOAM Proof of Transit Option-Type is to support path or service
function chain [RFC7665] verification use cases. Proof-of-transit
uses methods like nested hashing or nested encryption of the IOAM
data or mechanisms such as Shamir's Secret Sharing Schema (SSSS).
The IOAM Proof of Transit Option-Type consist of a fixed size "IOAM
proof of transit option header" and "IOAM proof of transit option
data fields". For details see [I-D.ietf-ippm-ioam-data].
4.3. Edge to Edge IOAM
The IOAM Edge-to-Edge Option-Type is to carry data that is added by
the IOAM encapsulating node and interpreted by IOAM decapsulating
node. The IOAM transit nodes may process the data but must not
modify it.
The IOAM Edge-to-Edge Option-Type consist of a fixed size "IOAM Edge-
to-Edge Option-Type header" and "IOAM Edge-to-Edge Option-Type data
fields". For details see [I-D.ietf-ippm-ioam-data].
4.4. Direct Export IOAM
Direct Export is an IOAM mode of operation within which IOAM data to
be directly exported to a collector rather than being collected
within the data packets. The IOAM Direct Export Option-Type consist
of a fixed size "IOAM direct export option header". Direct Export
for IOAM is defined in [I-D.ietf-ippm-ioam-direct-export].
5. IOAM Encapsulations
IOAM data fields and associated data types for in-situ OAM are
defined in [I-D.ietf-ippm-ioam-data]. The in-situ OAM data field can
be transported by a variety of transport protocols, including NSH,
Segment Routing, Geneve, IPv6, etc.
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5.1. IPv6
IOAM encapsulation for IPv6 is defined in
[I-D.ietf-ippm-ioam-ipv6-options]. IOAM deployment considerations
for IPv6 networks are found in
[I-D.ioametal-ippm-6man-ioam-ipv6-deployment].
5.2. NSH
IOAM encapsulation for NSH is defined in [I-D.ietf-sfc-ioam-nsh].
5.3. GRE
IOAM encapsulation for GRE is outlined as part of the "EtherType
Protocol Identification of In-situ OAM Data" in
[I-D.weis-ippm-ioam-eth], though no example protocol header stacks
are provided in the document. When used with GRE, the IOAM-Option-
Types (the below diagram uses "IOAM" as shorthand for IOAM-Option-
Types) are sequenced in behind the GRE header that follows the
"outer" IP header. Figure 2 shows two example protocol header stacks
that use GRE along with IOAM.
Example 1 Example 2
| ... | | ... |
+----------------+ +----------------+
| TCP/UDP header | | IP, ... |
+----------------+ +----------------+
| IP header | | Eth. header |
+----------------+ +----------------+
| IOAM | | IOAM |
+----------------+ +----------------+
| GRE header | | GRE header |
+----------------+ +----------------+
| IP header | | IP header |
+----------------+ +----------------+
| Layer 2 | | Layer 2 |
+----------------+ +----------------+
| Layer 1 | | Layer 1 |
+----------------+ +----------------+
Figure 2: GRE with IOAM examples
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5.4. Geneve
IOAM encapsulation for Geneve is defined in
[I-D.brockners-ippm-ioam-geneve].
5.5. Segment Routing
IOAM encapsulation for Segment Routing is defined in
[I-D.gandhi-spring-ioam-sr-mpls].
5.6. Segment Routing for IPv6
IOAM encapsulation for Segment Routing over IPv6 is defined in
[I-D.ali-spring-ioam-srv6].
5.7. VXLAN-GPE
IOAM encapsulation for VXLAN-GPE is defined in
[I-D.brockners-ippm-ioam-vxlan-gpe].
6. IOAM Data Export
IOAM nodes collect information for packets traversing a domain that
supports IOAM. IOAM decapsulating nodes as well as IOAM transit
nodes can choose to retrieve IOAM information from the packet,
process the information further and export the information using
e.g., IPFIX.
Raw data export of IOAM data using IPFIX is discussed in
[I-D.spiegel-ippm-ioam-rawexport]. "Raw export of IOAM data" refers
to a mode of operation where a node exports the IOAM data as it is
received in the packet. The exporting node neither interprets,
aggregates nor reformats the IOAM data before it is exported. Raw
export of IOAM data is to support an operational model where the
processing and interpretation of IOAM data is decoupled from the
operation of encapsulating/updating/decapsulating IOAM data, which is
also referred to as IOAM data-plane operation. The figure below
shows the separation of concerns for IOAM export: Exporting IOAM data
is performed by the "IOAM node" which performs IOAM data-plane
operation, whereas the interpretation of IOAM data is performed by
one or several IOAM data processing systems. The separation of
concerns is to off-load interpretation, aggregation and formatting of
IOAM data from the node which performs data-plane operations. In
other words, a node which is focused on data-plane operations, i.e.
forwarding of packets and handling IOAM data will not be tasked to
also interpret the IOAM data, but can leave this task to another
system or a set of systems. For scalability reasons, a single IOAM
node could choose to export IOAM data to several IOAM data processing
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systems. Similarly, there several monitoring systems or analytics
systems can be used to further process the data received from the
IOAM preprocessing systems. Figure 3 shows an overview of IOAM
export, including IOAM data processing systems and monitoring/
analytics systems.
+--------------+
+-------------+ |
| Monitoring/ | |
| Analytics | |
| system(s) |-+
+-------------+
^
| Processed/interpreted/
| aggregated IOAM data
|
+--------------+
+-------------+ |
| IOAM data | |
| processing | |
| system(s) |-+
+-------------+
^
| Raw export of
| IOAM data
|
+--------------+-------+------+--------------+
| | | |
| | | |
User +---+----+ +---+----+ +---+----+ +---+----+
packets |Encapsu-| | Transit| | Transit| |Decapsu-|
-------->|lating |====>| Node |====>| Node |====>|lating |-->
|Node | | A | | B | |Node |
+--------+ +--------+ +--------+ +--------+
Figure 3: IOAM framework with data export
7. IOAM Deployment Considerations
This section discusses several aspects of an IOAM deployment,
including IOAM Namespaces, IOAM Layering, traffic-sets that IOAM is
applied to and IOAM loopback mode.
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7.1. IOAM Namespaces
IOAM-Namespaces add further context to IOAM-Option-Types and
associated IOAM-Data-Fields. IOAM-Namespaces support several
different uses:
o IOAM-Namespaces can be used by an operator to distinguish
different operational domains. Devices at domain edges can filter
on Namespace-IDs to provide for proper IOAM-Domain isolation.
o IOAM-Namespaces provide additional context for IOAM-Data-Fields
and thus ensure that IOAM-Data-Fields are unique and can be
interpreted properly by management stations or network
controllers. While, for example, the node identifier field does
not need to be unique in a deployment (e.g. an operator may wish
to use different node identifiers for different IOAM layers, even
within the same device; or node identifiers might not be unique
for other organizational reasons, such as after a merger of two
formerly separated organizations), the combination of node_id and
Namespace-ID should always be unique. Similarly, IOAM-Namespaces
can be used to define how certain IOAM-Data-Fields are
interpreted: IOAM offers three different timestamp format options.
The Namespace-ID can be used to determine the timestamp format.
IOAM-Data-Fields (e.g. buffer occupancy) which do not have a unit
associated are to be interpreted within the context of a IOAM-
Namespace.
o IOAM-Namespaces can be used to identify different sets of devices
(e.g., different types of devices) in a deployment: If an operator
desires to insert different IOAM-Data-Fields based on the device,
the devices could be grouped into multiple IOAM-Namespaces. This
could be due to the fact that the IOAM feature set differs between
different sets of devices, or it could be for reasons of optimized
space usage in the packet header. It could also stem from
hardware or operational limitations on the size of the trace data
that can be added and processed, preventing collection of a full
trace for a flow.
* Assigning different IOAM Namespace-IDs to different sets of
nodes or network partitions and using the Namespace-ID as a
selector at the IOAM encapsulating node, a full trace for a
flow could be collected and constructed via partial traces in
different packets of the same flow. Example: An operator could
choose to group the devices of a domain into two IOAM-
Namespaces, in a way that at average, only every second hop
would be recorded by any device. To retrieve a full view of
the deployment, the captured IOAM-Data-Fields of the two IOAM-
Namespaces need to be correlated.
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* Assigning different IOAM Namespace-IDs to different sets of
nodes or network partitions and using a separate instance of an
IOAM-Option-Type for each Namespace-ID, a full trace for a flow
could be collected and constructed via partial traces from each
IOAM-Option-Type in each of the packets in the flow. Example:
An operator could choose to group the devices of a domain into
two IOAM-Namespaces, in a way that each IOAM-Namespace is
represented by one of two IOAM-Option-Types in the packet.
Each node would record data only for the IOAM-Namespace that it
belongs to, ignoring the other IOAM-Option-Type with a IOAM-
Namespace to which it doesn't belong. To retrieve a full view
of the deployment, the captured IOAM-Data-Fields of the two
IOAM-Namespaces need to be correlated.
7.2. IOAM Layering
If several encapsulation protocols (e.g., in case of tunneling) are
stacked on top of each other, IOAM-Data-Fields could be present in
different protocol fields at different layers. Layering allows
operators to instrument the protocol layer they want to measure. The
behavior follows the ships-in-the-night model, i.e. IOAM-Data-Fields
in one layer are independent from IOAM-Data-Fields in another layer.
Or in other words: Even though the term "layering" often implies some
form of hierarchy and relationship, in IOAM, layers are independent
from each other and don't assume any relationship among them. The
different layers could, but do not have to share the same IOAM
encapsulation mechanisms. Similarly, the sematics of the IOAM-Data-
Fields, can, do not have to be associated to across different layers.
For example, a node which inserts node-id information into two
different layers could use "node-id=10" for one layer and "node-
id=1000" for the second layer.
Figure 4 shows an example of IOAM layering. The figure shows a
Geneve tunnel carried over IPv6 which starts at node A and ends at
node D. IOAM information is encapsulated in IPv6 as well as in
Geneve. At the IPv6 layer, node A is IOAM encapsulating node (into
IPv6), node D is the IOAM decapsulating node and node B and node C
are IOAM transit nodes. At the Geneve layer, node A is IOAM
encapsulating node (into Geneve) and node D is IOAM decapsulating
node (from Geneve). The use of IOAM at both layers as shown in the
example here could be used to reveal which nodes of an underlay (here
the IPv6 network) are traversed by tunneled packet in an overlay
(here the Geneve network) - which assumes that the IOAM information
encapsulated by nodes A and D into Geneve and IPv6 is associated to
each other.
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+---+----+ +---+----+
User |Geneve | |Geneve |
packets |Encapsu-| |Decapsu-|
-------->|lating |==================================>|lating |-->
| Node | | Node |
| A | | D |
+--------+ +--------+
^ ^
| |
v v
+--------+ +--------+ +--------+ +--------+
|IPv6 | | IPv6 | | IPv6 | |IPv6 |
|Encapsu-| | Transit| | Transit| |Decapsu-|
|lating |====>| Node |====>| Node |====>|lating |
| Node | | | | | | Node |
| A | | B | | C | | D |
+--------+ +--------+ +--------+ +--------+
Figure 4: IOAM layering example
7.3. IOAM Trace Option Types
IOAM offers two different IOAM Option-Types for tracing:
"Incremental" Trace-Option-Type and "Pre-allocated" Trace-Option-
Type. "Incremental" refers to a mode of operation where the packet
is expanded at every IOAM node that addes IOAM-Data-Fields. "Pre-
Allocated" describes a mode of operation where the IOAM encapsulating
node allocates room for all IOAM-Data-Fields in the entire IOAM
domain. More specifically:
Pre-allocated Trace-Option: This trace option is defined as a
container of node data fields with pre-allocated space for each
node to populate its information. This option is useful for
implementations where it is efficient to allocate the space once
and index into the array to populate the data during transit
(e.g., software forwarders often fall into this class).
Incremental Trace-Option: This trace option is defined as a
container of node data fields where each node allocates and pushes
its node data immediately following the option header.
A deployment can choose to configure and support one or both of the
IOAM Trace-Option-Types. The operator decides by means of
configuration which Trace-Option-Type(s) will be used for a
particular domain. Deployments can mix devices which include either
the Incremental Trace-Option-Type or the Pre-allocated Trace-Option-
Type, e.g. in case different types of packet forwarders and
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associated different types of IOAM implementations exist in a
deployment. As a result, both Option-Types can be present in a
packet. IOAM decapsulating nodes remove both types of Trace-Option-
Types from the packet.
The two different Option-Types cater to different packet forwarding
infrastructures and are to allow an optimized implementation of IOAM
tracing:
Pre-allocated Trace-Option: For some implementations of packet
forwarders it is efficient to allocate the space for the maximum
number of nodes that IOAM Trace Data-Fields should be collected
from and insert/update information in the packet at flexible
locations, based on a pointer retrieved from a field in the
packet. The IOAM encapsulating node allocates an array of the
size of the maximum number of nodes that IOAM Trace Data-Fields
should be collected from. IOAM transit nodes index into the array
to populate the data during transit. Software forwarders often
fall into this class of packet forwarder implementations. The
maximum number of nodes that IOAM information could be collected
from is configured by the operator on the IOAM encapsulating node.
The operator has to ensure that the packet with the pre-allocated
array that carries the IOAM Data-Fields does not exceed the MTU of
any of the links in the IOAM domain.
Incremental Trace-Option: Looking up a pointer contained in the
packet and inserting/updating information at a flexible location
in the packet as a result of the pointer lookup is costly for some
forwarding infrastructures. Hardware-based packet forwarding
infrastructures often fall into this category. Consequently,
hardware-based packet forwarders could choose to support the
incremental IOAM-Trace-Option-Type. The incremental IOAM-Trace-
Option-Type eliminates the need for the IOAM transit nodes to read
the full array in the Trace-Option-Type and allows packets to grow
to the size of the MTU of the IOAM domain. IOAM transit nodes
will expand the packet and insert the IOAM-Data-Fields as long as
there is space available in the packet, i.e. as long as the size
of the packet stays within the bounds of the MTU of any of the
links in the IOAM domain. There is no need for the operator to
configure the IOAM encapsulation node with the maximum number of
nodes that IOAM information could be collected from. The operator
has to ensure that the minimum MTU of any of the links in the IOAM
domain is known to all IOAM transit nodes.
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7.4. Traffic-sets That IOAM Is Applied To
IOAM can be deployed on all or only on subsets of the live user
traffic,e.g. per interface, based on an access control list or flow
specification defining a specific set of traffic, etc.
7.5. IOAM Loopback Mode
IOAM Loopback is used to trigger each transit device along the path
of a packet to send a copy of the data packet back to the source.
Loopback allows an IOAM encapsulating node to trace the path to a
given destination, and to receive per-hop data about both the forward
and the return path. Loopback is enabled by the encapsulating node
setting the loopback flag. Looped-back packets use the source
address of the original packet as destination address and the address
of the node which performs the loopback operation as source address.
Nodes which loop back a packet clear the loopback flag before sending
the copy back towards the source. Loopack applies to IOAM
deployments where the encapsulating node is either a host or the
start of a tunnel: For details on IOAM loopback, please refer to
[I-D.ietf-ippm-ioam-flags].
7.6. IOAM Active Mode
The IOAM active mode flag indicates that a packet is an active OAM
packet as opposed to regular user data traffic. Active mode is
expected to be used for active measurement using IOAM. Example use-
cases include:
o Endpoint detailed active measurement: Synthetic probe packets are
sent between the source and destination, traversing the IOAM
domain. These probe packets include a Trace Option-Type (i.e.,
either incremental or pre-allocated). Since the probe packets are
sent between the endpoints, these packets are treated as data
packets by the IOAM domain, and do not require special treatment
at the IOAM layer.The encapsulating node can choose to set the
Active flag, providing an explicit indication that these probe
packets are meant for telemetry collection.
o IOAM active measurement using probe packets: Probe packets are
generated and transmitted by the IOAM encapsulating node, and are
expected to be terminated by the decapsulating node. Probe
packets include a Trace Option-Type (i.e., either incremental or
pre-allocated) which has its Active flag set, indicating that the
decapsulating node must terminate them.
o IOAM active measurement using replicated data packets: Probe
packets are created by the encapsulating node by selecting some or
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all of the en route data packets and replicating them. A selected
data packet that is replicated, and its (possibly truncated) copy
is forwarded with one or more IOAM option, while the original
packet is forwarded normally, without IOAM options. To the extent
possible, the original data packet and its replica are forwarded
through the same path. The replica includes a Trace Option-Type
that has its Active flag set, indicating that the decapsulating
node should terminate it.
For details on IOAM active mode, please refer to
[I-D.ietf-ippm-ioam-flags].
7.7. Brown Field Deployments: IOAM Unaware Nodes
A network can consist of a mix of IOAM aware and IOAM unaware nodes.
The encapsulation of IOAM-Data-Fields into different protocols (see
also Section 5) are defined such that data packets that include IOAM-
Data-Fields do not get dropped by IOAM unaware nodes. For example,
packets which contain the IOAM-Trace-Option-Types in IPv6 Hop by Hop
extension headers are defined with bits to indicate "00 - skip over
this option and continue processing the header". This will ensure
that when a node that is IOAM unaware receives a packet with IOAM-
Data-Fields included, does not drop the packet.
Deployments which leverage the IOAM-Trace-Option-Type(s) could
benefit from the ability to detect the presence of IOAM unaware
nodes, i.e. nodes which forward the packet but do not update/add
IOAM-Data-Fields in IOAM-Trace-Option-Type(s). The node data that is
defined as part of the IOAM-Trace-Option-Type(s) includes a Hop_Lim
field associated to the node identifier to detect missed nodes, i.e.
"holes" in the trace. Monitoring/Analytics system(s) could utilize
this information to account for the presence of IOAM unaware nodes in
the network.
8. IOAM Manageability
The YANG model for configuring IOAM in network nodes which support
IOAM is defined in [I-D.zhou-ippm-ioam-yang].
A deployment can leverage IOAM profiles is to limit the scope of IOAM
features, allowing simpler implementation, verification, and
interoperability testing in the context of specific use cases that do
not require the full functionality of IOAM. An IOAM profile defines
a use case or a set of use cases for IOAM, and an associated set of
rules that restrict the scope and features of the IOAM specification,
thereby limiting it to a subset of the full functionality. IOAM
profiles are defined in [I-D.mizrahi-ippm-ioam-profile].
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9. IANA Considerations
This document does not request any IANA actions.
10. Security Considerations
As discussed in [RFC7276], a successful attack on an OAM protocol in
general, and specifically on IOAM, can prevent the detection of
failures or anomalies, or create a false illusion of nonexistent
ones.
The Proof of Transit Option-Type (Section Section 4.2) is used for
verifying the path of data packets. The security considerations of
POT are further discussed in [I-D.ietf-sfc-proof-of-transit].
Security considerations related to the use of IOAM flags, in
particular the loopback flag are found in [I-D.ietf-ippm-ioam-flags].
IOAM data can be subject to eavesdropping. Although the
confidentiality of the user data is not at risk in this context, the
IOAM data elements can be used for network reconnaissance, allowing
attackers to collect information about network paths, performance,
queue states, buffer occupancy and other information. Recon is an
improbable security threat in an IOAM deployment that is within a
confined physical domain. However, in deployments that are not
confined to a single LAN, but span multiple inter-connected sites
(for example, using an overlay network), the inter-site links can be
secured (e.g., by IPsec) in order to avoid external eavesdropping.
Another possible mitigation approach is to use the "direct exporting"
mode [I-D.ietf-ippm-ioam-direct-export]. In this case the IOAM
related trace information would not be available in the customer data
packets, but would trigger exporting of (secured) packet-related IOAM
information at every node. IOAM data export and securing IOAM data
export is outside the scope of this document.
IOAM can be used as a means for implementing Denial of Service (DoS)
attacks, or for amplifying them. For example, a malicious attacker
can add an IOAM header to packets or modify an IOAM header in en
route packets in order to consume the resources of network devices
that take part in IOAM or collectors that analyze the IOAM data.
Another example is a packet length attack, in which an attacker
pushes headers associated with IOAM Option-Types into data packets,
causing these packets to be increased beyond the MTU size, resulting
in fragmentation or in packet drops. Such DoS attacks can be
mitigated by deploying IOAM in confined administrative domains, and
by defining performance limits on IOAM encapsulation and IOAM
exporting. By limiting the rate and/or percentage of packets that
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are subject to IOAM encpasulation and the rate of exported traffic,
it is possible to cofine the impact of such attacks.
Since IOAM options may include timestamps, if network devices use
synchronization protocols then any attack on the time protocol
[RFC7384] can compromise the integrity of the timestamp-related data
fields. Synchronization attacks can be mitigated by combining a
secured time distribution scheme, e.g., [RFC8915], and by using
redundant clock sources [RFC5905] and/or redundant network paths for
the time distribution protocol [RFC8039].
At the management plane, attacks may be implemented by misconfiguring
or by maliciously configuring IOAM-enabled nodes in a way that
enables other attacks. Thus, IOAM configuration should be secured in
a way that authenticates authorized users and verifies the integrity
of configuration procedures.
Notably, IOAM is expected to be deployed in specific network domains,
thus confining the potential attack vectors to within the network
domain. Indeed, in order to limit the scope of threats to within the
current network domain the network operator is expected to enforce
policies that prevent IOAM traffic from leaking outside of the IOAM
domain, and prevent IOAM data from outside the domain to be processed
and used within the domain. Note that the Immediate Export mode
(reference to be added in a future revision) can mitigate the
potential threat of IOAM data leaking through data packets.
11. Acknowledgements
The authors would like to thank Tal Mizrahi, Eric Vyncke, Nalini
Elkins, Srihari Raghavan, Ranganathan T S, Barak Gafni, Karthik Babu
Harichandra Babu, Akshaya Nadahalli, LJ Wobker, Erik Nordmark,
Vengada Prasad Govindan, Andrew Yourtchenko, Aviv Kfir, Tianran Zhou,
Zhenbin (Robin), Joe Clarke, Al Morton, Tom Herbet, Haoyu song, and
Mickey Spiegel for the comments and advice on IOAM.
12. References
12.1. 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>.
[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>.
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12.2. Informative References
[I-D.ali-spring-ioam-srv6]
Ali, Z., Gandhi, R., Filsfils, C., Brockners, F., Nainar,
N., Pignataro, C., Li, C., Chen, M., and G. Dawra,
"Segment Routing Header encapsulation for In-situ OAM
Data", draft-ali-spring-ioam-srv6-03 (work in progress),
November 2020.
[I-D.brockners-ippm-ioam-geneve]
Brockners, F., Bhandari, S., Govindan, V. P., Pignataro,
C., Nainar, N. K., Gredler, H., Leddy, J., Youell, S.,
Mizrahi, T., Lapukhov, P., Gafni, B., Kfir, A., and M.
Spiegel, "Geneve encapsulation for In-situ OAM Data",
draft-brockners-ippm-ioam-geneve-05 (work in progress),
November 2020.
[I-D.brockners-ippm-ioam-vxlan-gpe]
Brockners, F., Bhandari, S., Govindan, V. P., Pignataro,
C., Gredler, H., Leddy, J., Youell, S., Mizrahi, T., Kfir,
A., Gafni, B., Lapukhov, P., and M. Spiegel, "VXLAN-GPE
Encapsulation for In-situ OAM Data", draft-brockners-ippm-
ioam-vxlan-gpe-03 (work in progress), November 2019.
[I-D.gandhi-spring-ioam-sr-mpls]
Gandhi, R., Ali, Z., Filsfils, C., Brockners, F., Wen, B.,
and V. Kozak, "Segment Routing with MPLS Data Plane
Encapsulation for In-situ OAM Data", draft-gandhi-spring-
ioam-sr-mpls-02 (work in progress), August 2019.
[I-D.ietf-ippm-ioam-data]
Brockners, F., Bhandari, S., and T. Mizrahi, "Data Fields
for In-situ OAM", draft-ietf-ippm-ioam-data-12 (work in
progress), February 2021.
[I-D.ietf-ippm-ioam-direct-export]
Song, H., Gafni, B., Zhou, T., Li, Z., Brockners, F.,
Bhandari, S., Sivakolundu, R., and T. Mizrahi, "In-situ
OAM Direct Exporting", draft-ietf-ippm-ioam-direct-
export-03 (work in progress), February 2021.
[I-D.ietf-ippm-ioam-flags]
Mizrahi, T., Brockners, F., Bhandari, S., Sivakolundu, R.,
Pignataro, C., Kfir, A., Gafni, B., Spiegel, M., and J.
Lemon, "In-situ OAM Flags", draft-ietf-ippm-ioam-flags-04
(work in progress), February 2021.
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[I-D.ietf-ippm-ioam-ipv6-options]
Bhandari, S., Brockners, F., Pignataro, C., Gredler, H.,
Leddy, J., Youell, S., Mizrahi, T., Kfir, A., Gafni, B.,
Lapukhov, P., Spiegel, M., Krishnan, S., Asati, R., and M.
Smith, "In-situ OAM IPv6 Options", draft-ietf-ippm-ioam-
ipv6-options-05 (work in progress), February 2021.
[I-D.ietf-nvo3-geneve]
Gross, J., Ganga, I., and T. Sridhar, "Geneve: Generic
Network Virtualization Encapsulation", draft-ietf-
nvo3-geneve-16 (work in progress), March 2020.
[I-D.ietf-nvo3-vxlan-gpe]
(Editor), F. M., (editor), L. K., and U. E. (editor),
"Generic Protocol Extension for VXLAN (VXLAN-GPE)", draft-
ietf-nvo3-vxlan-gpe-11 (work in progress), March 2021.
[I-D.ietf-sfc-ioam-nsh]
Brockners, F. and S. Bhandari, "Network Service Header
(NSH) Encapsulation for In-situ OAM (IOAM) Data", draft-
ietf-sfc-ioam-nsh-05 (work in progress), December 2020.
[I-D.ietf-sfc-proof-of-transit]
Brockners, F., Bhandari, S., Mizrahi, T., Dara, S., and S.
Youell, "Proof of Transit", draft-ietf-sfc-proof-of-
transit-08 (work in progress), November 2020.
[I-D.ioametal-ippm-6man-ioam-ipv6-deployment]
Bhandari, S., Brockners, F., Mizrahi, T., Kfir, A., Gafni,
B., Spiegel, M., Krishnan, S., and M. Smith, "Deployment
Considerations for In-situ OAM with IPv6 Options", draft-
ioametal-ippm-6man-ioam-ipv6-deployment-03 (work in
progress), March 2020.
[I-D.mizrahi-ippm-ioam-profile]
Mizrahi, T., Brockners, F., Bhandari, S., Sivakolundu, R.,
Pignataro, C., Kfir, A., Gafni, B., Spiegel, M., Zhou, T.,
and J. Lemon, "In Situ OAM Profiles", draft-mizrahi-ippm-
ioam-profile-04 (work in progress), February 2021.
[I-D.spiegel-ippm-ioam-rawexport]
Spiegel, M., Brockners, F., Bhandari, S., and R.
Sivakolundu, "In-situ OAM raw data export with IPFIX",
draft-spiegel-ippm-ioam-rawexport-04 (work in progress),
November 2020.
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[I-D.weis-ippm-ioam-eth]
Weis, B., Brockners, F., Hill, C., Bhandari, S., Govindan,
V. P., Pignataro, C., Gredler, H., Leddy, J., Youell, S.,
Mizrahi, T., Kfir, A., Gafni, B., Lapukhov, P., and M.
Spiegel, "EtherType Protocol Identification of In-situ OAM
Data", draft-weis-ippm-ioam-eth-04 (work in progress), May
2020.
[I-D.zhou-ippm-ioam-yang]
Zhou, T., Guichard, J., Brockners, F., and S. Raghavan, "A
YANG Data Model for In-Situ OAM", draft-zhou-ippm-ioam-
yang-08 (work in progress), July 2020.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<https://www.rfc-editor.org/info/rfc5905>.
[RFC7276] Mizrahi, T., Sprecher, N., Bellagamba, E., and Y.
Weingarten, "An Overview of Operations, Administration,
and Maintenance (OAM) Tools", RFC 7276,
DOI 10.17487/RFC7276, June 2014,
<https://www.rfc-editor.org/info/rfc7276>.
[RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in
Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
October 2014, <https://www.rfc-editor.org/info/rfc7384>.
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<https://www.rfc-editor.org/info/rfc7665>.
[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with
Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
May 2016, <https://www.rfc-editor.org/info/rfc7799>.
[RFC8039] Shpiner, A., Tse, R., Schelp, C., and T. Mizrahi,
"Multipath Time Synchronization", RFC 8039,
DOI 10.17487/RFC8039, December 2016,
<https://www.rfc-editor.org/info/rfc8039>.
[RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
"Network Service Header (NSH)", RFC 8300,
DOI 10.17487/RFC8300, January 2018,
<https://www.rfc-editor.org/info/rfc8300>.
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[RFC8915] Franke, D., Sibold, D., Teichel, K., Dansarie, M., and R.
Sundblad, "Network Time Security for the Network Time
Protocol", RFC 8915, DOI 10.17487/RFC8915, September 2020,
<https://www.rfc-editor.org/info/rfc8915>.
Authors' Addresses
Frank Brockners
Cisco Systems, Inc.
Hansaallee 249, 3rd Floor
DUESSELDORF, NORDRHEIN-WESTFALEN 40549
Germany
Email: fbrockne@cisco.com
Shwetha Bhandari (editor)
Thoughtspot
3rd Floor, Indiqube Orion, 24th Main Rd, Garden Layout, HSR Layout
Bangalore, KARNATAKA 560 102
India
Email: shwetha.bhandari@thoughtspot.com
Daniel Bernier
Bell Canada
Canada
Email: daniel.bernier@bell.ca
Tal Mizrahi (editor)
Huawei
8-2 Matam
Haifa 3190501
Israel
Email: tal.mizrahi.phd@gmail.com
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