Hybrid Two-Step Performance Measurement Method
draft-ietf-ippm-hybrid-two-step-03
| Document | Type | Active Internet-Draft (ippm WG) | |
|---|---|---|---|
| Authors | Greg Mirsky , Wang Lingqiang , Guo Zhui , Haoyu Song , Pascal Thubert | ||
| Last updated | 2024-10-19 | ||
| Replaces | draft-mirsky-ippm-hybrid-two-step | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
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| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
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| Send notices to | (None) |
draft-ietf-ippm-hybrid-two-step-03
IPPM Working Group G. Mirsky
Internet-Draft Ericsson
Intended status: Standards Track W. Lingqiang
Expires: 22 April 2025 G. Zhui
ZTE Corporation
H. Song
Futurewei Technologies
P. Thubert
Independent
19 October 2024
Hybrid Two-Step Performance Measurement Method
draft-ietf-ippm-hybrid-two-step-03
Abstract
The development and advancements in network operation automation have
brought new measurement methodology requirements. mong them is the
ability to collect instant network state as the packet being
processed by the networking elements along its path through the
domain. That task can be solved using on-path telemetry, also called
hybrid measurement. An on-path telemetry method allows the
collection of essential information that reflects the operational
state and network performance experienced by the packet. This
document introduces a method complementary to on-path telemetry that
causes the generation of telemetry information. This method,
referred to as Hybrid Two-Step (HTS), separates the act of measuring
and/or calculating the performance metric from collecting and
transporting network state. The HTS packet traverses the same set of
nodes and links as the trigger packet, thus simplifying the
correlation of informational elements originating on nodes traversed
by the trigger packet.
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
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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."
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This Internet-Draft will expire on 22 April 2025.
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/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 4
2.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
3. Problem Overview . . . . . . . . . . . . . . . . . . . . . . 4
4. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 6
4.1. Operation of the HTS Ingress Node . . . . . . . . . . . . 8
4.2. Operation of the HTS Intermediate Node . . . . . . . . . 10
4.3. Operation of the HTS Egress Node . . . . . . . . . . . . 11
5. Operationaal Considerations . . . . . . . . . . . . . . . . . 12
5.1. Deploying HTS in a Multicast Network . . . . . . . . . . 12
6. Authentication in HTS . . . . . . . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7.1. IOAM Option-Type for HTS . . . . . . . . . . . . . . . . 14
7.2. HTS TLV Registry . . . . . . . . . . . . . . . . . . . . 14
7.3. HTS Sub-TLV Type Sub-registry . . . . . . . . . . . . . . 15
7.4. HMAC Type Sub-registry . . . . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . 17
10.2. Informative References . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
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1. Introduction
Successful resolution of challenges of automated network operation,
as part of, for example, overall service orchestration or data center
operation, relies on a timely collection of accurate information that
reflects the state of network elements on an unprecedented scale.
Because performing the analysis and act upon the collected
information requires considerable computing and storage resources,
the network state information is unlikely to be processed by the
network elements themselves but will be relayed into the data storage
facilities, e.g., data lakes. The process of producing, collecting
network state information also referred to in this document as
network telemetry, and transporting it for post-processing should
work equally well with data flows or injected in the network test
packets. [RFC7799] describes a combination of elements of passive
and active measurement as a hybrid measurement.
Several technical methods have been proposed to enable the collection
of network state information instantaneous to the packet processing,
among them [P4.INT] and [RFC9197]. The instantaneous, i.e., in the
data packet itself, collection of telemetry information simplifies
the process of attribution of telemetry information to the particular
monitored flow. On the other hand, this collection method impacts
the data packets, potentially changing their treatment by the
networking nodes. Also, the amount of information the instantaneous
method collects might be incomplete because of the limited space it
can be allotted. Other proposals defined methods to collect
telemetry information in a separate packet from each node traversed
by the monitored data flow. Examples of this approach to collecting
telemetry information are [RFC9326] and
[I-D.song-ippm-postcard-based-telemetry]. These methods allow data
collection from any arbitrary path and avoid directly impacting data
packets. On the other hand, the correlation of data and the
monitored flow requires that each packet with telemetry information
also includes characteristic information about the monitored flow.
This document introduces Hybrid Two-Step (HTS) as a new method of
telemetry collection that improvers accuracy of a measurement by
separating the act of measuring or calculating the performance metric
from the collecting and transporting this information while
minimizing the overhead of the generated load in a network. HTS
method extends the two-step mode of Residence Time Measurement (RTM)
defined in [RFC8169] to on-path network state collection and
transport. HTS allows the collection of telemetry information from
any arbitrary path, does not change data packets of the monitored
flow and makes the process of attribution of telemetry to the data
flow simple.
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2. Conventions used in this document
2.1. Acronyms
RTM Residence Time Measurement
ECMP Equal Cost Multipath
MTU Maximum Transmission Unit
HTS Hybrid Two-Step
HMAC Hashed Message Authentication Code
TLV Type-Length-Value
RTT Round-Trip Time
Network telemetry - the process of collecting and reporting of
network state
2.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Problem Overview
Performance measurements are meant to provide data that characterize
conditions experienced by traffic flows in the network and possibly
trigger operational changes (e.g., re-route of flows, or changes in
resource allocations). Modifications to a network are determined
based on the performance metric information available when a change
is to be made. The correctness of this determination is based on the
quality of the collected metrics data. The quality of collected
measurement data is defined by:
* the resolution and accuracy of each measurement;
* predictability of both the time at which each measurement is made
and the timeliness of measurement collection data delivery for
use.
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Consider the case of delay measurement that relies on collecting time
of packet arrival at the ingress interface and time of the packet
transmission at the egress interface. The method includes recording
a local clock value on receiving the first octet of an affected
message at the device ingress, and again recording the clock value on
transmitting the first byte of the same message at the device egress.
In this ideal case, the difference between the two recorded clock
times corresponds to the time that the message spent in traversing
the device. In practice, the time recorded can differ from the ideal
case by any fixed amount. A correction can be applied to compute the
same time difference taking into account the known fixed time
associated with the actual measurement. In this way, the resulting
time difference reflects any variable delay associated with queuing.
Depending on the implementation, it may be a challenge to compute the
difference between message arrival and departure times and - on the
fly - add the necessary residence time information to the same
message. And that task may become even more challenging if the
packet is encrypted. Recording the departure of a packet time in the
same packet may be decremental to the accuracy of the measurement
because the departure time includes the variable time component (such
as that associated with buffering and queuing of the packet). A
similar problem may lower the quality of, for example, information
that characterizes utilization of the egress interface. If unable to
obtain the data consistently, without variable delays for additional
processing, information may not accurately reflect the egress
interface state. To mitigate this problem [RFC8169] defined an RTM
two-step mode.
Another challenge associated with methods that collect network state
information into the actual data packet is the risk to exceed the
Maximum Transmission Unit (MTU) size on the path, especially if the
packet traverses overlay domains or VPNs. Since the fragmentation is
not available at the transport network, operators may have to reduce
MTU size advertised to the client layer or risk missing network state
data for the part, most probably the latter part, of the path.
In some networks, for example, wireless that are in the scope of
[RFC9450], it is beneficial to collect the telemetry, including the
calculated performance metrics, that reflects conditions experienced
by the monitored flow at a node, other than the egress. For example,
a head-end can optimize path selection based on the compounded
information that reflects network conditions, resource utilization.
This mode is referred to as the upstream collection and the other -
downstream collection to differentiate between two modes of telemetry
collection.
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4. Theory of Operation
The HTS method consists of two phases:
* performing a measurement and/or obtaining network state
information on a node;
* collecting and transporting the measurement and/or the telemetry
information.
HTS may use an HTS Trigger carried in a data packet or a specially
constructed test packet. For example, an HTS Trigger could be a
packet that has IOAM Option-Type set to the "IOAM Hybrid Two-Step
Option-Type" value (TBA1) allocated by IANA (see Section 7.1). The
HTS Trigger includes HTS IOAM Header (shown in Figure 1) consists of:
* IOAM Namespace-ID - as defined in Section 5.3 [RFC9197];
* Flags - as defined in Section 3.2 [RFC9326];
* Extension-Flags - as defined in Section 3.2 [RFC9326];
* IOAM-Trace-Type - as defined in Section 5.4 [RFC9197];
* optional Flow ID - as defined in Section 3.2 [RFC9326];
* optional Sequence Number - as defined in Section 3.2 [RFC9326].
A packet in the flow to which the Alternate-Marking method, defined
in [RFC9341] and [RFC9342], is applied can be used as an HTS Trigger.
The nature of the HTS Trigger is a transport network layer-specific,
and its description is outside the scope of this document. The
packet that includes the HTS Trigger in this document is also
referred to as the trigger packet.
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 | Flags |Extension-Flags|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IOAM-Trace-Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flow ID (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Figure 1: Hybrid Two-Step Trace IOAM Header
The HTS method uses the HTS Follow-up packet, referred to as the
follow-up packet, to collect measurement and network state data from
the nodes. The node that creates the HTS Trigger also generates the
HTS Follow-up packet. In some use cases, e.g., when HTS is used to
collect the telemetry, including performance metrics, calculated
based on a series of measurements, an HTS follow-up packet can be
originated without using the HTS Trigger. The follow-up packet
contains characteristic information sufficient for participating HTS
nodes to associate it with the monitored data flow. The
characteristic information can be obtained using the information of
the trigger packet or constructed by a node that originates the
follow-up packet. As the follow-up packet is expected to traverse
the same sequence of nodes, one element of the characteristic
information is the information that determines the path in the data
plane. For example, in a segment routing domain [RFC8402], a list of
segment identifiers of the trigger packet is applied to the follow-up
packet. And in the case of the service function chain based on the
Network Service Header [RFC8300], the Base Header and Service Path
Header of the trigger packet will be applied to the follow-up packet.
Also, when HTS is used to collect the telemetry information in an
IOAM domain, the IOAM trace option header [RFC9197] of the trigger
packet is applied in the follow-up packet. The follow-up packet also
uses the same network information used to load-balance flows in
equal-cost multipath (ECMP) as the trigger packet, e.g., IPv6 Flow
Label [RFC6437] or an entropy label [RFC6790]. The exact composition
of the characteristic information is specific for each transport
network, and its definition is outside the scope of this document.
Only one outstanding follow-up packet MUST be on the node for the
given path. That means that if the node receives an HTS Trigger for
the flow on which it still waits for the follow-up packet to the
previous HTS Trigger, the node will originate the follow-up packet to
transport the former set of the network state data and transmit it
before it sends the follow-up packet with the latest collection of
network state information.
The following sections describe the operation of HTS nodes in the
downstream mode of collecting the telemetry information. In the
upstream mode, the bahavior of HTS nodes, in general, identical with
the exception that the HTS Trigger packet does not precede the HTS
Follow-up packet.
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4.1. Operation of the HTS Ingress Node
A node that originates the HTS Trigger is referred to as the HTS
ingress node. As stated, the ingress node originates the follow-up
packet. The follow-up packet has the transport network encapsulation
identical with the trigger packet followed by the HTS shim and one or
more telemetry information elements encoded as Type-Length-Value
(TLV). Figure 2 displays an example of the follow-up packet format.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Transport Network ~
| Encapsulation |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver|HTS Shim L | Flags |Sequence Number| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HTS Max Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Telemetry Data Profile ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Telemetry Data TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Follow-up Packet Format
Fields of the HTS shim are as follows:
Version (Ver) is the two-bits long field. It specifies the
version of the HTS shim format. This document defines the format
for the 0b00 value of the field.
HTS Shim Length is the six bits-long field. It defines the length
of the HTS shim in octets. The minimal value of the field is
eight octets.
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|F| Reserved |
+-+-+-+-+-+-+-+-+
Figure 3: Flags Field Format
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Flags is eight-bits long. The format of the Flags field displayed
in Figure 3.
- Full (F) flag MUST be set to zero by the node originating the
HTS follow-up packet and MUST be set to one by the node that
does not add its telemetry data to avoid exceeding MTU size.
- The node originating the follow-up packet MUST zero the
Reserved field and ignore it on the receipt.
Sequence Number is one octet-long field. The zero-based value of
the field reflects the place of the HTS follow-up packet in the
sequence of the HTS follow-up packets that originated in response
to the same HTS trigger. The ingress node MUST set the value of
the field to zero.
Reserved is one octet-long field. It MUST be zeroed on
transmission and ignored on recepit.
HTS Max Length is four octet-long field. The value of th HTS Max
Length field indicates the maximum length of the HTS Follow-up
packet in octets. An operator MUST be able to configure the HTS
Max Length field's value. The value SHOULD be set equal to the
path MTU.
Telemetry Data Profile is the optional variable-length field of
bit-size flags. Each flag indicates the requested type of
telemetry data to be collected at each HTS node. The increment of
the field is four bytes with a minimum length of zero. For
example, IOAM-Trace-Type information defined in [RFC9197],
Sequence Number and/or Flow ID (Figure 1) can be used in the
Telemetry Data Profile 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Reserved | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Value ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Telemetry Data TLV Format
Telemetry Data TLV is a variable-length field. Multiple TLVs MAY
be placed in an HTS packet. Additional TLVs may be enclosed
within a given TLV, subject to the semantics of the (outer) TLV in
question. Figure 4 presents the format of a Telemetry Data TLV,
where fields are defined as the following:
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- Type - a one-octet-long field that characterizes the
interpretation of the Value field.
- Reserved - one-octet-long field.
- Length - two-octet-long field equal to the length of the Value
field in octets.
- Value - a variable-length field. The value of the Type field
determines its interpretation and encoding. IOAM data fields,
defined in [RFC9197], MAY be carried in the Value field.
All multibyte fields defined in this specification are in network
byte order.
4.2. Operation of the HTS Intermediate Node
Upon receiving the trigger packet, the HTS intermediate node MUST:
* copy the transport information;
* start the HTS Follow-up Timer for the obtained flow;
* transmit the trigger packet.
Upon receiving the follow-up packet, the HTS intermediate node MUST:
1. verify that the matching transport information exists and the
Full flag is cleared, then stop the associated HTS Follow-up
Timer;
2. otherwise, transmit the received packet. Proceed to Step 8;
3. collect telemetry data requested in the Telemetry Data Profile
field or defined by the local HTS policy;
4. if adding the collected telemetry would not exceed HTS Max Length
field's value, then append data as a new Telemetry Data TLV and
transmit the follow-up packet. Proceed to Step 8;
5. otherwise, set the value of the Full flag to one, copy the
transport information from the received follow-up packet and
transmit it accordingly. Proceed to Step 8;
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6. originate the new follow-up packet using the transport
information copied from the received follow-up packet. The value
of the Sequence Number field in the HTS shim MUST be set to the
value of the field in the received follow-up packet incremented
by one;
7. copy collected telemetry data into the first Telemetry Data TLV's
Value field and then transmit the packet;
8. processing completed.
If the HTS Follow-up Timer expires, the intermediate node MUST:
* originate the follow-up packet using transport information
associated with the expired timer;
* initialize the HTS shim by setting the Version field's value to
0b00 and Sequence Number field to 0. Values of HTS Shim Length
and Telemetry Data Profile fields MAY be set according to the
local policy.
* copy telemetry information into Telemetry Data TLV's Value field
and transmit the packet.
If the intermediate node receives a "late" follow-up packet, i.e., a
packet to which the node has no associated HTS Follow-up timer, the
node MUST forward the "late" packet.
4.3. Operation of the HTS Egress Node
Upon receiving the trigger packet, the HTS egress node MUST:
* copy the transport information;
* start the HTS Collection timer for the obtained flow.
When the egress node receives the follow-up packet for the known
flow, i.e., the flow to which the Collection timer is running, the
node for each of Telemetry Data TLVs MUST:
* if HTS is used in the authenticated mode, verify the
authentication of the Telemetry Data TLV using the Authentication
sub-TLV (see Section 6);
* copy telemetry information from the Value field;
* restart the corresponding Collection timer.
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When the Collection timer expires, the egress relays the collected
telemetry information for processing and analysis to a local or
remote agent.
5. Operationaal Considerations
Correctly attributing information originated by the particular
trigger packet to the proper HTS Follow-up packet is essential for
the HTS protocol. That can be achieved using characteristic
information that uniquely idetifies the trigger packet within a given
HTS domain. For example, a combination of the flow identifier and
packet's sequence number within that flow, as Flow ID and Sequence
Number in IOAM Direct Export [RFC9326], can be used to correlate
between stored telemetry information and the appropriate HTS Follow-
up packet. In case the trigger packet doesn't include data that
distinguish it from other trigger packets in the HTS domain, then for
the particular flow, there MUST be no more than one HTS Trigger,
values of HTS timers bounded by the rate of the trigger generation
for that flow. In practice, the minimal interval between HTS Trigger
packets SHOULD be selected from the range determined by the round-
trip time (RTT) between HTS Ingress and HTS Egress nodes as [RTT/2,
RTT].
5.1. Deploying HTS in a Multicast Network
Previous sections discussed the operation of HTS in a unicast
network. Multicast services are important, and the ability to
collect telemetry information is invaluable in delivering a high
quality of experience. While the replication of data packets is
necessary, replication of HTS follow-up packets is not. Replication
of multicast data packets down a multicast tree may be set based on
multicast routing information or explicit information included in the
special header, as, for example, in Bit-Indexed Explicit Replication
[RFC8296]. A replicating node processes the HTS packet as defined
below:
* the first transmitted multicast packet MUST be followed by the
received corresponding HTS packet as described in Section 4.2;
* each consecutively transmitted copy of the original multicast
packet MUST be followed by the new HTS packet originated by the
replicating node that acts as an intermediate HTS node when the
HTS Follow-up timer expired.
As a result, there are no duplicate copies of Telemetry Data TLV for
the same pair of ingress and egress interfaces. At the same time,
all ingress/egress pairs traversed by the given multicast packet
reflected in their respective Telemetry Data TLV. Consequently, a
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centralized controller would reconstruct and analyze the state of the
particular multicast distribution tree based on HTS packets collected
from egress nodes.
6. Authentication in HTS
Telemetry information may be used to drive network operation, closing
the control loop for self-driving, self-healing networks. Thus it is
critical to provide a mechanism to protect the telemetry information
collected using the HTS method. This document defines an optional
authentication of a Telemetry Data TLV that protects the collected
information's integrity.
The format of the Authentication sub-TLV is displayed in Figure 5.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Authentic. Type| HMAC Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Digest |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: HMAC sub-TLV
where fields are defined as follows:
* Authentication Type - is a one-octet-long field, value 1 is
allocated by IANA Section 7.2.
* Length - two-octet-long field, set equal to the length of the
Digest field in octets.
* HMAC Type - is a one-octet-long field that identifies the type of
the HMAC and the length of the digest and the length of the digest
according to the HTS HMAC Type sub-registry (see Section 7.4).
* Digest - is a variable-length field that carries HMAC digest of
the text that includes the encompassing TLV.
This specification defines the use of HMAC-SHA-256 truncated to 128
bits ([RFC4868]) in HTS. Future specifications may define the use in
HTS of more advanced cryptographic algorithms or the use of digest of
a different length. HMAC is calculated as defined in [RFC2104] over
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text as the concatenation of the Sequence Number field of the follow-
up packet (see Figure 2) and the preceding data collected in the
Telemetry Data TLV. The digest then MUST be truncated to 128 bits
and written into the Digest field. Distribution and management of
shared keys are outside the scope of this document. In the HTS
authenticated mode, the Authentication sub-TLV MUST be present in
each Telemetry Data TLV. HMAC MUST be verified before using any data
in the included Telemetry Data TLV. If HMAC verification fails, the
system MUST stop processing corresponding Telemetry Data TLV and
notify an operator. Specification of the notification mechanism is
outside the scope of this document.
7. IANA Considerations
7.1. IOAM Option-Type for HTS
The IOAM Option-Type registry is requested in [RFC9197]. IANA is
requested to allocate a new code point as listed in Table 1.
+=======+======================+=============+===============+
| Value | Name | Description | Reference |
+=======+======================+=============+===============+
| TBA1 | IOAM Hybrid Two-Step | HTS | This document |
| | (HTS) Option-Type | Exporting | |
+-------+----------------------+-------------+---------------+
Table 1: IOAM Option-Type for HTS
7.2. HTS TLV Registry
IANA is requested to create "Hybrid Two-Step" registry group. IANA
is requested to create the HTS TLV Type registry in "Hybrid Two-Step"
registry group. All code points in the range 1 through 175 in this
registry shall be allocated according to the "IETF Review" procedure
specified in [RFC8126]. Code points in the range 176 through 239 in
this registry shall be allocated according to the "First Come First
Served" procedure specified in [RFC8126]. The remaining code points
are allocated according to Table 2:
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+===========+==============+===============+
| Value | Description | Reference |
+===========+==============+===============+
| 0 | Reserved | This document |
+-----------+--------------+---------------+
| 1- 175 | Unassigned | This document |
+-----------+--------------+---------------+
| 176 - 239 | Unassigned | This document |
+-----------+--------------+---------------+
| 240 - 251 | Experimental | This document |
+-----------+--------------+---------------+
| 252 - 254 | Private Use | This document |
+-----------+--------------+---------------+
| 255 | Reserved | This document |
+-----------+--------------+---------------+
Table 2: HTS TLV Type Registry
7.3. HTS Sub-TLV Type Sub-registry
IANA is requested to create the HTS sub-TLV Type sub-registry as part
of the HTS TLV Type registry. All code points in the range 1 through
175 in this registry shall be allocated according to the "IETF
Review" procedure specified in [RFC8126]. Code points in the range
176 through 239 in this registry shall be allocated according to the
"First Come First Served" procedure specified in [RFC8126]. The
remaining code points are allocated according to Table 3:
+===========+==============+==========+===============+
| Value | Description | TLV Used | Reference |
+===========+==============+==========+===============+
| 0 | Reserved | None | This document |
+-----------+--------------+----------+---------------+
| 1 | HMAC | Any | This document |
+-----------+--------------+----------+---------------+
| 2 - 175 | Unassigned | | This document |
+-----------+--------------+----------+---------------+
| 176 - 239 | Unassigned | | This document |
+-----------+--------------+----------+---------------+
| 240 - 251 | Experimental | | This document |
+-----------+--------------+----------+---------------+
| 252 - 254 | Private Use | | This document |
+-----------+--------------+----------+---------------+
| 255 | Reserved | None | This document |
+-----------+--------------+----------+---------------+
Table 3: HTS Sub-TLV Type Sub-registry
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7.4. HMAC Type Sub-registry
IANA is requested to create the HMAC Type sub-registry as part of the
HTS TLV Type registry. All code points in the range 1 through 127 in
this registry shall be allocated according to the "IETF Review"
procedure specified in [RFC8126]. Code points in the range 128
through 239 in this registry shall be allocated according to the
"First Come First Served" procedure specified in [RFC8126]. The
remaining code points are allocated according to Table 4:
+===========+=============================+===============+
| Value | Description | Reference |
+===========+=============================+===============+
| 0 | Reserved | This document |
+-----------+-----------------------------+---------------+
| 1 | HMAC-SHA-256 16 octets long | This document |
+-----------+-----------------------------+---------------+
| 2 - 127 | Unassigned | This document |
+-----------+-----------------------------+---------------+
| 128 - 239 | Unassigned | This document |
+-----------+-----------------------------+---------------+
| 240 - 249 | Experimental | This document |
+-----------+-----------------------------+---------------+
| 250 - 254 | Private Use | This document |
+-----------+-----------------------------+---------------+
| 255 | Reserved | This document |
+-----------+-----------------------------+---------------+
Table 4: HMAC Type Sub-registry
8. Security Considerations
Nodes that practice the HTS method are presumed to share a trust
model that depends on the existence of a trusted relationship among
nodes. This is necessary as these nodes are expected to correctly
modify the specific content of the data in the follow-up packet, and
the degree to which HTS measurement is useful for network operation
depends on this ability. In practice, this means either
confidentiality or integrity protection cannot cover those portions
of messages that contain the network state data. Though there are
methods that make it possible in theory to provide either or both
such protections and still allow for intermediate nodes to make
detectable yet authenticated modifications, such methods do not seem
practical at present, particularly for protocols that used to measure
latency and/or jitter.
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This document defines the use of authentication (Section 6) to
protect the integrity of the telemetry information collected using
the HTS method. Privacy protection can be achieved by, for example,
sharing the IPsec tunnel with a data flow that generates information
that is collected using HTS.
While it is possible for a supposed compromised node to intercept and
modify the network state information in the follow-up packet; this is
an issue that exists for nodes in general - for all data that to be
carried over the particular networking technology - and is therefore
the basis for an additional presumed trust model associated with an
existing network.
9. Acknowledgments
Authors express their gratitude and appreciation to Joel Halpern for
the most helpful and insightful discussion on the applicability of
HTS in a Service Function Chaining domain. Also, authors thank Bjørn
Ivar Teigen for the discussion about ensuring proper correlation
between generated telemetry information and an HTS Follow-up packet.
10. References
10.1. Normative References
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
DOI 10.17487/RFC2104, February 1997,
<https://www.rfc-editor.org/info/rfc2104>.
[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>.
[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>.
[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>.
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[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>.
10.2. Informative References
[I-D.song-ippm-postcard-based-telemetry]
Song, H., Mirsky, G., Zhou, T., Li, Z., Graf, T., Mishra,
G. S., Shin, J., and K. Lee, "On-Path Telemetry using
Packet Marking to Trigger Dedicated OAM Packets", Work in
Progress, Internet-Draft, draft-song-ippm-postcard-based-
telemetry-16, 2 June 2023,
<https://datatracker.ietf.org/doc/html/draft-song-ippm-
postcard-based-telemetry-16>.
[P4.INT] "In-band Network Telemetry (INT)", P4.org Specification,
October 2017.
[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
384, and HMAC-SHA-512 with IPsec", RFC 4868,
DOI 10.17487/RFC4868, May 2007,
<https://www.rfc-editor.org/info/rfc4868>.
[RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
"IPv6 Flow Label Specification", RFC 6437,
DOI 10.17487/RFC6437, November 2011,
<https://www.rfc-editor.org/info/rfc6437>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012,
<https://www.rfc-editor.org/info/rfc6790>.
[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>.
[RFC8169] Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S.,
and A. Vainshtein, "Residence Time Measurement in MPLS
Networks", RFC 8169, DOI 10.17487/RFC8169, May 2017,
<https://www.rfc-editor.org/info/rfc8169>.
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[RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
for Bit Index Explicit Replication (BIER) in MPLS and Non-
MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
2018, <https://www.rfc-editor.org/info/rfc8296>.
[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>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[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>.
[RFC9342] Fioccola, G., Ed., Cociglio, M., Sapio, A., Sisto, R., and
T. Zhou, "Clustered Alternate-Marking Method", RFC 9342,
DOI 10.17487/RFC9342, December 2022,
<https://www.rfc-editor.org/info/rfc9342>.
[RFC9450] Bernardos, CJ., Ed., Papadopoulos, G., Thubert, P., and F.
Theoleyre, "Reliable and Available Wireless (RAW) Use
Cases", RFC 9450, DOI 10.17487/RFC9450, August 2023,
<https://www.rfc-editor.org/info/rfc9450>.
Authors' Addresses
Greg Mirsky
Ericsson
Email: [email protected]
Wang Lingqiang
ZTE Corporation
No 19 ,East Huayuan Road
Beijing
100191
China
Phone: +86 10 82963945
Email: [email protected]
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Guo Zhui
ZTE Corporation
No 19 ,East Huayuan Road
Beijing
100191
China
Phone: +86 10 82963945
Email: [email protected]
Haoyu Song
Futurewei Technologies
2330 Central Expressway
Santa Clara,
United States of America
Email: [email protected]
Pascal Thubert
Independent
06330 Roquefort-les-Pins
France
Email: [email protected]
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