Internet DRAFT - draft-mzbc-ippm-transit-measurement-option
draft-mzbc-ippm-transit-measurement-option
IPPM T. Mizrahi
Internet-Draft T. Zhou
Intended status: Standards Track S. Belkar
Expires: 16 August 2024 R. Cohen
Huawei
13 February 2024
The Transit Measurement Option
draft-mzbc-ippm-transit-measurement-option-03
Abstract
This document specifies an IPv6 option that contains a compact set of
fields which can be used for transit delay measurement and congestion
detection. This option can be incorporated into data packets and
updated by transit nodes along the path, enabling lightweight
measurement and monitoring using constant-length data that does not
depend on the number of hops in the network.
Status of This Memo
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This Internet-Draft will expire on 16 August 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Requirement Language . . . . . . . . . . . . . . . . . . 4
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
3. Transit Measurement Option . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
4.1. IPv6 Option Type . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
This document introduces an IPv6 option that includes a compact set
of performance-related fields. This option can be incorporated into
data packets and updated by transit nodes along the path.
There is a number of in-progress documents in the IETF that define
IPv6 options that can be used for tracing a path and its performance,
including for example, [I-D.ietf-ippm-ioam-ipv6-options],
[I-D.filsfils-spring-path-tracing], [I-D.ali-spring-ioam-srv6],
[I-D.kumar-ippm-ifa], [I-D.zhou-ippm-enhanced-alternate-marking].
Some of these extensions use per-hop fields which are updated by
intermediate nodes, collecting information about the performance
along the path. While these extension provide detailed and fine-
grained information, they incur high per-packet bandwidth and
processing overhead.
The Transit Measurement option, which is defined in this document,
provides coarse-grained performance information using a set of fields
that have a constant length that does not depend on the number of
hops along the path. These fields are defined as a new IPv6 option
type, referred to as the Transit Measurement option.
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The Transit Measurement option includes two main fields: Accumulated
Delay and Status Bitmap. The Accumulated Delay field is used for
measuring the one-way delay along the path. Each transit node
incrementally adds its internal transit delay to the Accumulated
Delay field, and thus at the end of the path this field includes the
sum of the transit delay values of the nodes along the path. The
Status Bitmap field includes a per-hop bit that indicates its
congestion status. Each node along the path updates its
corresponding status bit, indicating whether the node is congested.
The criterion for deciding whether a node is congested is similar to
the "Congestion Experienced" trigger in ECN [RFC3168].
The Transit Measurement option can be incorporated into all or a
subset of the traffic that is forwarded by the source node. Notably,
the Transit Measurement option adds a fixed and low overhead to data
packets, which remains constant along the path.
There are several potential use cases for the Transit Measurement
option, including:
* Performance Monitoring: the Transit Measurement option can be used
for continuously tracking the network and for detecting a
potentially problematic state that requires further analysis. In
case a potential problem is detected by the destination node, the
node may take further steps to report and to analyze the problem.
For example, the node can export the packet, along with additional
telemetry data to a collector, or it may log the problem locally.
Upon detecting such a problem, a centralized collector/analyzer
may trigger a more fine-grained measurement, e.g., an IOAM trace
option [RFC9197] can be enabled in order to obtain detailed
information about the performance along the path and to pinpoint
the potential problem. It should be noted that logging,
exporting, and further analysis by the central entity are not
within the scope of the current document.
* Path Selection: in a network that uses segment routing a source
can choose which of the available paths to use to each
destination. By using the Transit Measurement option the source
can probe each of the available paths to a given destination, and
choose the path with the best performance. If there is a
performance issue along one of the paths, the fine-grained status
bitmap enables the source to pinpoint the location of the issue,
and to try to pick an alternative path that avoids this point.
Alternatively, a path can be selected by the combination of the
measured delay along the path and the status bitmap; for example,
the path with less bits set in the status bitmap can be the
preferred path, and the measured delay can be used as a
tiebreaker.
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* Congestion control: existing congestion control algorithms
periodically measure the round-trip time (RTT), and can optionally
use ECN indications as a criterion for determining the congestion
window. It has been shown [SIGCOMM-HPCC] that congestion control
can benefit from using fine-grained information about the
congestion state of the routers along the path that is sent back
to the source over acknowledgment packets. The Transit
Measurement option provides fine-grained measurement information
that has a lightweight cost in comparison to alternative per-hop
measurement protocols.
2. Conventions
2.1. Requirement 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.
2.2. Terminology
Abbreviations used in this document:
OAM: Operations, Administration, and Maintenance
ECN: Explicit Congestion Notification
3. Transit Measurement Option
This document defines a new IPv6 Option type, the Transit Measurement
type, which can be included either in the Hop-by-Hop Options header
or in the Destination Options header. Figure 1 presents the format
of the Transit Measurement option type.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Accumulated Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop Count | Status Bitmap |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Figure 1: Transit Measurement Option Type
A node that complies to this draft MUST support the following fields,
as depicted in Figure 1:
Option Type: This document assigns the value TBD-type, which
indicates that this is the Transit Measurement option. The two
highest order bits are "00", indicating that nodes that cannot
process this option skip over it and continue processing the
header, as defined in [RFC8200]. The third-highest-order bit is
set to "1", indicating that this option may change en route.
Opt Data Len: The length in octets of the two fields that follow,
which is 8.
Accumulated Delay: represents the sum of the transit delay values in
nanoseconds along the path of the packet, including the current
node. This field is a 4-octet unsigned integer in the range 0 to
2^31-1. A transit node that receives the Accumulated Delay field
updates its value by adding the transit delay of the current node
to the value of the Accumulated Delay field in the received
packet. The 'transit delay' in this context is the time in
nanoseconds the packet spent in the transit node. If the
Accumulated Delay exceeds 2^31-1 nanoseconds then the most
significant bit is set to indicate overflow and the value is set
to 0x80000000. If a transit node receives this field with the
value 0x80000000 or if the node is not able to update the value of
the field it SHOULD forward the packet with the unmodified field.
Hop Count/Status Bitmap: indicates the devices along the path that
have experienced congestion.
Hop Count: a one-octet field that indicates the number of hops
since the source node. The source node initializes this field
to 0. Every transit node that supports this option increments
this field by 1. A maximum of 24 hops is supported. If a
transit node receives this field with the value 24 it assigns
the value of all '1's (0xFF = 255), which indicates that the
number of hops has exceeded the maximum.
Status Bitmap: a three octet field that represents the congestion
status of each transit node along the path. The value '1'
indicates that the current packet was enqueued in a queue that
is congested. The criterion for whether a queue is congested
or not is identical to the "Congestion Experienced" trigger in
ECN. Every transit node that supports the Transit Measurement
option updates the bit corresponding to the current Hop Count,
after having updated the value of the Hop Count. For example,
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the first transit node along the path updates the Hop Count to
1, and then updates the first (most significant bit) of the
Status Bitmap. The source and destination nodes do not update
the Status Bitmap. If a node detects that the Hop Count has
exceeded its maximal value (24), it does not update the Status
Bitmap field.
4. IANA Considerations
4.1. IPv6 Option Type
IANA is requested to allocate a value from the IPv6 Destination
Options and Hop-by-Hop Options registry:
Value: TBD-type
act: 00
chg: 1
Description: Transit Measurement
5. Security Considerations
The Transit Option, and specifically the Accumulated Delay field,
which is defined in this document, may be used for reconnaissance,
which in turn can facilitate other types of attacks. As in other
types of Operations, Administration and Maintenance (OAM) protocols,
a malicious attacker can manipulate the Accumulated Delay value in
order to create a false illusion of nonexistent network issues or
prevent the detection of actual ones.
6. References
6.1. 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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[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
6.2. Informative References
[I-D.ali-spring-ioam-srv6]
Ali, Z., Gandhi, R., Filsfils, C., Brockners, F., Nainar,
N. K., Pignataro, C., Li, C., Chen, M., and G. Dawra,
"Segment Routing Header encapsulation for In-situ OAM
Data", Work in Progress, Internet-Draft, draft-ali-spring-
ioam-srv6-06, 10 July 2022,
<https://datatracker.ietf.org/doc/html/draft-ali-spring-
ioam-srv6-06>.
[I-D.filsfils-spring-path-tracing]
Filsfils, C., Abdelsalam, A., Camarillo, P., Yufit, M.,
Graf, T., Su, Y., Matsushima, S., Valentine, M., and
Dhamija, "Path Tracing in SRv6 networks", Work in
Progress, Internet-Draft, draft-filsfils-spring-path-
tracing-05, 23 October 2023,
<https://datatracker.ietf.org/doc/html/draft-filsfils-
spring-path-tracing-05>.
[I-D.ietf-ippm-ioam-ipv6-options]
Bhandari, S. and F. Brockners, "In-situ OAM IPv6 Options",
Work in Progress, Internet-Draft, draft-ietf-ippm-ioam-
ipv6-options-12, 7 May 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-ippm-
ioam-ipv6-options-12>.
[I-D.kumar-ippm-ifa]
Kumar, J., Anubolu, S., Lemon, J., Manur, R., Holbrook,
H., Ghanwani, A., Cai, D., Ou, H., Li, Y., and X. Wang,
"Inband Flow Analyzer", Work in Progress, Internet-Draft,
draft-kumar-ippm-ifa-07, 7 September 2023,
<https://datatracker.ietf.org/doc/html/draft-kumar-ippm-
ifa-07>.
[I-D.zhou-ippm-enhanced-alternate-marking]
Zhou, T., Fioccola, G., Liu, Y., Cociglio, M., Pang, R.,
Xiong, L., Lee, S., and W. Li, "Enhanced Alternate Marking
Method", Work in Progress, Internet-Draft, draft-zhou-
ippm-enhanced-alternate-marking-14, 23 November 2023,
<https://datatracker.ietf.org/doc/html/draft-zhou-ippm-
enhanced-alternate-marking-14>.
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[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001,
<https://www.rfc-editor.org/info/rfc3168>.
[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>.
[SIGCOMM-HPCC]
Li, Y., Miao, R., Liu, H., Zhuang, Y., Fei Feng, F., Tang,
L., Cao, Z., Zhang, M., Kelly, F., Alizadeh, M., and M.
Yu, "HPCC: High Precision Congestion Control", ACM
SIGCOMM Beijing, China, August 2019.
Authors' Addresses
Tal Mizrahi
Huawei
8-2 Matam
Haifa 3190501
Israel
Email: tal.mizrahi.phd@gmail.com
Tianran Zhou
Huawei
156 Beiqing Rd.
Beijing
100095
China
Email: zhoutianran@huawei.com
Shahar Belkar
Huawei
8-2 Matam
Haifa 3190501
Israel
Email: shahar.belkar@huawei.com
Reuven Cohen
Huawei
8-2 Matam
Haifa 3190501
Israel
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Email: reuven.cohen@huawei.com
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