IOAM Trace Option Extensions for Incorporating the Alternate-Marking Method
draft-he-ippm-ioam-extensions-incorporating-am-00
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | hexiaoming , Xiao Min , Frank Brockners , Giuseppe Fioccola , Chongfeng Xie | ||
| Last updated | 2024-03-03 | ||
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draft-he-ippm-ioam-extensions-incorporating-am-00
IPPM Working Group X. He
Internet-Draft China Telecom
Intended status: Standards Track X. Min
Expires: 4 September 2024 ZTE Corp.
F. Brockners
Cisco
G. Fioccola
Huawei
C. Xie
China Telecom
3 March 2024
IOAM Trace Option Extensions for Incorporating the Alternate-Marking
Method
draft-he-ippm-ioam-extensions-incorporating-am-00
Abstract
In situ Operation, Administration, and Maintenance (IOAM) is used for
recording and collecting operational and telemetry information.
Specifically, passport-based IOAM allows telemetry data generated by
each node along the path to be pushed into data packets when they
traverse the network, while postcard-based IOAM allows IOAM data
generated by each node to be directly exported without being pushed
into in-flight data packets. This document extends IOAM Trace Option
for incorporating the Alternate-Marking Method.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 4 September 2024.
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Copyright Notice
Copyright (c) 2024 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
extracted from this document must include Revised BSD License text as
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
3. The Extended IOAM Trace Option Format . . . . . . . . . . . . 4
4. The IOAM Operation . . . . . . . . . . . . . . . . . . . . . 6
4.1. Packet Loss Measurement . . . . . . . . . . . . . . . . . 6
4.2. Packet Delay Measurement . . . . . . . . . . . . . . . . 7
4.3. Flow Identification . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5.1. IOAM Type . . . . . . . . . . . . . . . . . . . . . . . . 9
5.2. Reserved Field . . . . . . . . . . . . . . . . . . . . . 9
6. Performance Considerations . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
IOAM [RFC9197], which defines two possible IOAM Trace Option-Types:
Pre-allocated Trace and Incremental Trace, is used for monitoring
traffic in the network and for incorporating IOAM data fields into
in-flight data packets. IOAM Trace Option is known as the passport
mode, in which each node on the path can add telemetry data to the
user packets (i.e., stamps the passport). IOAM Direct Export (DEX)
[RFC9326] is used as a trigger for IOAM nodes to directly export IOAM
data to a receiving entity such as a collector, analyzer, or
controller. IOAM DEX is also referred as the postcard mode, in which
each node directly exports the telemetry data using an independent
packet (i.e., sends a postcard) while the user packets are
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unmodified.
The disadvantage of the passport mode is that if a packet is dropped
on the path, the IOAM data collected are also lost. So the passport
mode such as IOAM Trace Option-Type has no ability to monitor packet
drop and packet drop location.
IOAM DEX Option-Type can complement IOAM Trace Option-Type in that
even if a packet is dropped on the path, the partial data collected
are still available. By correlating the data from different nodes,
the number of the discarded packets can be counted accurately and
packet drop location can be pinpointed.
The Alternate-Marking [RFC9341] technique has been proven to work
well to perform packet loss, delay, and jitter measurements on live
traffic. RFC9343 describes how the Alternate-Marking Method can be
used to measure performance metrics in IPv6. It defines an Extension
Header Option to encode Alternate-Marking information in both the
Hop-by-Hop Options Header and Destination Options Header. In order
to facilitate the deployment and improve the scalability of the
Alternate-Marking Method, the Flow Monitoring Identification
(FlowMonID) field is introduced. The benefits of introducing
FlowMonID are obvious: First, it helps to reduce the per-node
configuration; Second, it simplifies the counters handling; Third, it
eases the data export encapsulation and correlation for the
collectors.
[draft-he-ippm-integrating-am-into-ioam] presents the problems and
challenges currently faced by IOAM DEX Option in measuring
performance metrics such as packet loss, delay, and jitter. In order
to augment performance measurement of IOAM, it also defines the IOAM
DEX Option extension to incorporate the Alternate-Marking Method into
IOAM.
This document defines the IOAM Trace Option extension for
incorporating the Alternate-Marking Method to augment performance
measurement of IOAM.
2. Conventions
2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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2.2. Terminology
Abbreviations used in this document:
DEX: Direct Exporting
IOAM: In situ Operation, Administration, and Maintenance
MPN: Measurement Period Number
OAM: Operation, Administration, and Maintenance
SN: Sequence Number
3. The Extended IOAM Trace Option Format
The format of the extended trace Option-Type is depicted in Figure 1.
All fields are same as IOAM Trace Option-Type header Format defined
in RFC9197 except the 8-bit Reserved field. The extended Trace
Option-Type Format uses the most significant 5 bits of the Reserved
field.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Namespace-ID | NodeLen | Flags | RemainingLen|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IOAM-Trace-Type |D|L|F|S|M|Resvd|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flow ID (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Measurement Period Number (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: The Extended IOAM Trace Option header Format
Where:
Namespace-ID: 16-bit identifier of the IOAM namespace, as defined in
[RFC9197].
NodeLen: 5-bit unsigned integer, as defined in [RFC9197].
Flags: 4-bit field, as defined in [RFC9197].
RemainingLen: 7-bit unsigned integer, as defined in [RFC9197].
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IOAM-Trace-Type: 24-bit identifier that specifies which data types
are used in the node data list, as defined in [RFC9197].
L: 1-bit Loss flag, defined in this document for Packet Loss
Measurement as described in Section 4.1.
D: 1-bit Delay flag, defined in this document for Packet Delay
Measurement as described in Section 4.2.
F: 1-bit Flow ID flag, defined in this document. This flag that is
set to 1 indicates the existence of a corresponding optional 4-octet
field.
S: 1-bit Sequence Number (SN) flag, defined in this document. This
flag that is set to 1 indicates the existence of a corresponding
optional 4-octet field.
M: 1-bit Measurement Period Number (MPN) flag, defined in this
document. This flag that is set to 1 indicates the existence of a
corresponding optional 4-octet field.
Reserved: 3-bit field, reserved for future use. These bits MUST be
set to zero on transmission and ignored on receipt.
Optional fields: The optional fields, if present, reside after the
Reserved field. The order of the optional fields is according to the
order of the respective bits, which are enabled in the F, S and M
Flags field. Each optional field is 4 octets long.
Flow ID: An optional 32-bit field representing the flow identifier.
If the actual Flow ID is shorter than 32 bits, it is zero padded in
its most significant bits. The field is set at the encapsulating
node and exported to the receiving entity by the forwarding nodes.
The Flow ID can be used to correlate the exported data of the same
flow from multiple nodes and from multiple packets. Flow ID values
are expected to be allocated in a way that avoids collisions. For
example, random assignment of Flow ID values can be subject to
collisions, while centralized allocation can avoid this problem. The
specification of the Flow ID allocation method is not within the
scope of this document.
Sequence Number: An optional 32-bit sequence number, starting from 0
and incremented by 1 for each packet from the same flow at the
encapsulating node that includes the DEX option. The Sequence
Number, when combined with the Flow ID, provides a convenient
approach to correlate the exported data from the same user packet.
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Measurement Period Number(MPN): An optional 32-bit field representing
the measurement period number of the monitored flow, starting from 0
and incremented by 1 for the specified flow with the same Flow ID.
The field is set at the encapsulating node and exported to the
receiving entity by the forwarding nodes. The MPN, when combined
with the Flow ID, provides a convenient approach to correlate the
exported data of the same flow during the same measurement period
from multiple nodes.
4. The IOAM Operation
The extended Trace Option-Type SHOULD support to perform both
performance measurement and IOAM trace monitoring concurrently.
While both performance measurement and IOAM trace monitoring are
implemented concurrently, an IOAM encapsulating node MUST incorporate
the extended Trace Option-Type into all the service traffic packets
of interest it forwards. For performance measurement, an IOAM
encapsulating node MUST mark every monitored packet it forwards in
"L" and "D" flag of the extended Trace Option-Type; for IOAM trace
monitoring, all the traffic of interest or only a subset of the
packets COULD be selected by an IOAM encapsulating node. For every
selected packet, an IOAM encapsulating node MUST set corresponding
bit flag to 1 in IOAM- Trace-Type field of the extended Trace Option-
Type so that every node along the path needs to generate the
specified IOAM data filled in the node data list field of packet; for
all the other packets not selected, an IOAM encapsulating node MUST
set all 24 bits flag to 0 in IOAM-Trace-Type field of the extended
Trace Option-Type, such that each node along the path does not need
to generate the IOAM data filled in the node data list field of
packet.
4.1. Packet Loss Measurement
The measurement of the packet loss is detailed in [RFC9341]and
[RFC9343]. The packets of the flow identified by Flow ID are grouped
into batches, and all the packets within a batch are marked by
setting the L bit (Loss flag) to a same value. The source node (IOAM
encapsulating node) can switch the value of the L bit between 0 and 1
after a fixed number of packets or according to a fixed timer, and
this depends on the implementation. The source node is the only one
that marks the packets to create the batches, while the intermediate
nodes only read the marking values and identify the packet batches.
By counting the number of packets in each batch using packet counter
and comparing the values measured by different network nodes along
the path, it is possible to measure the packet loss that occurred in
any single batch between any two nodes. Each batch represents a
measurable entity recognizable by all network nodes along the path,
which export the counter value of this batch along with the Flow ID
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and the MPN (if it exists) to the receiving entity (e.g., the
collector).
4.2. Packet Delay Measurement
Delay metrics MAY be calculated using the following two
possibilities:
Single-Marking Methodology: This approach uses only the L bit to
calculate both packet loss and delay. In this case, the D flag MUST
be set to zero on transmit and ignored by the monitoring points. The
alternation of the values of the L bit can be used as a time
reference to calculate the delay. Whenever the L bit changes and a
new batch starts, a network node can store the timestamp of the first
packet of the new batch; that timestamp can be compared with the
timestamp of the first packet of the same batch on a second node to
compute packet delay. But, this measurement is accurate only if no
packet loss occurs and if there is no packet reordering at the edges
of the batches. A different approach can also be considered, and it
is based on the concept of the mean delay. The mean delay for each
batch is calculated by considering the average arrival time of the
packets for the relative batch. There are limitations also in this
case indeed; each node needs to collect all the timestamps and
calculate the average timestamp for each batch. In addition, the
information is limited to a mean value.
Double-Marking Methodology: This approach is more complete and uses
the L bit only to calculate packet loss, and the D bit (Delay flag)
is fully dedicated to delay measurements. The idea is to use the
first marking with the L bit to create the alternate flow and, within
the batches identified by the L bit, a second marking with the D bit
set to 1 is used to select the packets for measuring delay. The D
bit creates a new set of marked packets that are fully identified
over the network so that a forwarding node can store and export the
timestamps of these packets; these timestamps can be compared with
the timestamps of the same packets on a second node to compute packet
delay values for each packet. The most efficient and robust mode is
to select a single double-marked packet for each batch; in this way,
there is no time gap to consider between the double-marked packets to
avoid their reorder. If a double-marked packet is lost, the delay
measurement for the considered batch is simply discarded, but this is
not a big problem because it is easy to recognize the problematic
batch and skip the measurement just for that one. So in order to
have more information about the delay and to overcome out-of-order
issues, this method is preferred.
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In summary, the approach with Double Marking is better than the
approach with Single Marking. In the implementation, the timestamps
along with Flow ID and Sequence Number and MPN(if they exist) can be
sent out to the receiving entity that is responsible for the
calculation.
4.3. Flow Identification
The Flow Identification (Flow ID) identifies the flow to be measured
and is required for some general reasons, which is described in
Section 5.3 of [RFC9343]. [RFC9343] uses 20-bit FlowMonID to
determine a monitored flow within the measurement domain. Compared
to the FlowMonID, the Flow ID in this document is a 32-bit field,
which amplifies the FlowMonID space by 4096 times. Accordingly, a
chance of collision is greatly reduced in a distributed way.
When the 32-bit Flow ID is used for every source node, if there are N
edge nodes (source nodes) in a large-scale operator network, and each
source node can generate a unique Flow ID for every measured flow
independently and pseudo-randomly in a distributed way. Assuming
that each node randomly generates M different Flow IDs from the
available K flow identification space, then the total possible sample
space is
the Nth power of C (K, M)
and the total possible sample space not duplicate is
C1 (K, M)*C2 (K-M, M )*....*CN (k-(N-1)M, M)
Theoritically, the non-collision probability is calculated as the
total possible sample space not duplicate divided by the total
possible sample space.
Take K=32nd power of 2, N=100, M=100 as an example, and the non-
collision probability is 0.9885. That is to say, when generating
10000 concurrent flows, there might be 115 measured flow identifiers
incurring a chance of collision. If K=20th power of 2 is taken,
which corresponds to 20-bit Flow ID space, the collision probability
will drastically increases to approximately 100%. In practical
deployment scenarios of large-scale networks, the simultaneous
measurement flows could reach orders of magnitude of 100000 or even
higher, thus the collision probability will rise sharply.
It is preferred that Flow ID be assigned by the central controller.
Since the controller knows the network topology, it can allocate the
value properly to guarantee the uniqueness of Flow ID allocation.
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5. IANA Considerations
5.1. IOAM Type
The "IOAM Option-Type" registry is defined in Section 7.1 of
[RFC9197].
IANA is requested to allocate the following code point from the "IOAM
Option-Type" registry as follows:
TBA-type IOAM Extended Trace Option Type.
If possible, IANA is requested to allocate code point 6 (TBA-type).
5.2. Reserved Field
IANA is requested to allocate the following 5-bit flags for
performance measurement from the 8-bit Reserved field created by
IANA.
Bit 0 (the most significant bit): 1-bit Loss flag for Packet Loss
Measurement and described in Section 4.1.
Bit 1: 1-bit Delay flag for Packet Delay Measurement and described in
Section 4.2.
Bit 2: 1-bit Flow ID flag and described in Section 3.
Bit 3: 1-bit SN flag and described in Section 3.
Bit 4: 1-bit MPN flag and described in Section3.
6. Performance Considerations
The extended Trace Option-Type triggers IOAM trace data to be filled
in live data packets and performance measurement data to be exported
to a receiving entity.
Performance measurement is implemented based on the Alternate-Marking
Method. In Hop-by-Hop mode for loss measurement, every node along
the path only exports a packet carrying the counter value of each
measurement block including a batch of packets; In End-to-End mode
for loss measurement, only the IOAM encapsulating node and the IOAM
decapsulating node export a packet carrying the counter value of each
measurement block. Similarly, in Hop-by-Hop mode for delay
measurement, every node along the path only exports a packet carrying
the timestamp of the marked packet in each measurement block; In End-
to-End mode for delay measurement, only the IOAM encapsulating node
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and the IOAM decapsulating node export a packet carrying the
timestamp of the same marked packet in each measurement block.
Because of the very small amount of exported traffic, it would not
affect the network bandwidth and would not overload the receiving
entity. In addition, compared with IOAM DEX Option-Type for packet
loss calculation, due to a significant reduction in the number of
exported packets, the receiving entity needs much less processing
overhead to correlate these counter values for packet loss
computations.
7. Security Considerations
The security considerations of IOAM in general are discussed in
[RFC9197]. There are not additional security considerations in this
extended IOAM Trace Option-Type.
8. References
8.1. 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>.
[RFC9197] Brockners, F., Ed., Bhandari, S., Ed., and T. Mizrahi,
Ed., "Data Fields for In Situ Operations, Administration,
and Maintenance (IOAM)", RFC 9197, DOI 10.17487/RFC9197,
May 2022, <https://www.rfc-editor.org/info/rfc9197>.
[RFC9326] Song, H., Gafni, B., Brockners, F., Bhandari, S., and T.
Mizrahi, "In Situ Operations, Administration, and
Maintenance (IOAM) Direct Exporting", RFC 9326,
DOI 10.17487/RFC9326, November 2022,
<https://www.rfc-editor.org/info/rfc9326>.
[RFC9341] Fioccola, G., Ed., Cociglio, M., Mirsky, G., Mizrahi, T.,
and T. Zhou, "Alternate-Marking Method", RFC 9341,
DOI 10.17487/RFC9341, December 2022,
<https://www.rfc-editor.org/info/rfc9341>.
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[RFC9343] Fioccola, G., Zhou, T., Cociglio, M., Qin, F., and R.
Pang, "IPv6 Application of the Alternate-Marking Method",
RFC 9343, DOI 10.17487/RFC9343, December 2022,
<https://www.rfc-editor.org/info/rfc9343>.
8.2. Informative References
[I-D.he-ippm-integrating-am-into-ioam]
hexiaoming, X., Brockners, F., Song, H., Fioccola, G., and
A. Wang, "Integrating the Alternate-Marking Method into In
Situ Operations, Administration, and Maintenance (IOAM)",
Work in Progress, Internet-Draft, draft-he-ippm-
integrating-am-into-ioam-01, 8 January 2024,
<https://datatracker.ietf.org/doc/html/draft-he-ippm-
integrating-am-into-ioam-01>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC9486] Bhandari, S., Ed. and F. Brockners, Ed., "IPv6 Options for
In Situ Operations, Administration, and Maintenance
(IOAM)", RFC 9486, DOI 10.17487/RFC9486, September 2023,
<https://www.rfc-editor.org/info/rfc9486>.
Authors' Addresses
Xiaoming He
China Telecom
Email: hexm4@chinatelecom.cn
Xiao Min
ZTE Corp.
Email: xiao.min2@zte.com.cn
Frank Brockners
Cisco
Email: fbrockne@cisco.com
Giuseppe Fioccola
Huawei
Email: giuseppe.fioccola@huawei.com
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Chongfeng Xie
China Telecom
Email: xiechf@chinatelecom.cn
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