ALTO Performance Cost Metrics
draft-ietf-alto-performance-metrics-15
ALTO Working Group Q. Wu
Internet-Draft Huawei
Intended status: Standards Track Y. Yang
Expires: August 7, 2021 Yale University
Y. Lee
Samsung
D. Dhody
Huawei
S. Randriamasy
Nokia Bell Labs
L. Contreras
Telefonica
February 3, 2021
ALTO Performance Cost Metrics
draft-ietf-alto-performance-metrics-15
Abstract
Cost metric is a basic concept in Application-Layer Traffic
Optimization (ALTO), and different applications may use different
cost metrics. Since the ALTO base protocol (RFC 7285) defines only a
single cost metric (i.e., the generic "routingcost" metric), if an
application wants to issue a cost map or an endpoint cost request to
determine the resource provider that offers better delay performance,
the base protocol does not define the cost metric to be used.
This document addresses the issue by introducing network performance
metrics, including network delay, jitter, packet loss rate, hop
count, and bandwidth.
There are multiple sources (e.g., estimation based on measurements or
service-level agreement) to derive a performance metric. This
document introduces an additional "cost-context" field to the ALTO
"cost-type" field to convey the source of a performance metric.
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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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-
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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."
This Internet-Draft will expire on August 7, 2021.
Copyright Notice
Copyright (c) 2021 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
(http://trustee.ietf.org/license-info) in effect on the date of
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Performance Metric Attributes . . . . . . . . . . . . . . . . 5
2.1. Performance Metric Context: cost-context . . . . . . . . 6
2.2. Performance Metric Statistics . . . . . . . . . . . . . . 8
3. Packet Performance Metrics . . . . . . . . . . . . . . . . . 9
3.1. Cost Metric: One-Way Delay (delay-ow) . . . . . . . . . . 10
3.1.1. Base Identifier . . . . . . . . . . . . . . . . . . . 10
3.1.2. Value Representation . . . . . . . . . . . . . . . . 10
3.1.3. Intended Semantics and Use . . . . . . . . . . . . . 10
3.1.4. Cost-Context Specification Considerations . . . . . . 12
3.2. Cost Metric: Round-trip Delay (delay-rt) . . . . . . . . 12
3.2.1. Base Identifier . . . . . . . . . . . . . . . . . . . 12
3.2.2. Value Representation . . . . . . . . . . . . . . . . 12
3.2.3. Intended Semantics and Use . . . . . . . . . . . . . 12
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3.2.4. Cost-Context Specification Considerations . . . . . . 14
3.3. Cost Metric: Delay Variation (delay-variation) . . . . . 14
3.3.1. Base Identifier . . . . . . . . . . . . . . . . . . . 14
3.3.2. Value Representation . . . . . . . . . . . . . . . . 14
3.3.3. Intended Semantics and Use . . . . . . . . . . . . . 14
3.3.4. Cost-Context Specification Considerations . . . . . . 16
3.4. Cost Metric: Hop Count (hopcount) . . . . . . . . . . . . 16
3.4.1. Base Identifier . . . . . . . . . . . . . . . . . . . 16
3.4.2. Value Representation . . . . . . . . . . . . . . . . 16
3.4.3. Intended Semantics and Use . . . . . . . . . . . . . 16
3.4.4. Cost-Context Specification Considerations . . . . . . 18
3.5. Cost Metric: Loss Rate (lossrate) . . . . . . . . . . . . 18
3.5.1. Base Identifier . . . . . . . . . . . . . . . . . . . 18
3.5.2. Value Representation . . . . . . . . . . . . . . . . 18
3.5.3. Intended Semantics and Use . . . . . . . . . . . . . 18
3.5.4. Cost-Context Specification Considerations . . . . . . 19
4. Bandwidth Performance Metrics . . . . . . . . . . . . . . . . 20
4.1. Cost Metric: TCP Throughput (tput) . . . . . . . . . . . 20
4.1.1. Base Identifier . . . . . . . . . . . . . . . . . . . 20
4.1.2. Value Representation . . . . . . . . . . . . . . . . 20
4.1.3. Intended Semantics and Use . . . . . . . . . . . . . 20
4.1.4. Cost-Context Specification Considerations . . . . . . 21
4.2. Cost Metric: Residual Bandwidth (bw-residual) . . . . . . 22
4.2.1. Base Identifier . . . . . . . . . . . . . . . . . . . 22
4.2.2. Value Representation . . . . . . . . . . . . . . . . 22
4.2.3. Intended Semantics and Use . . . . . . . . . . . . . 22
4.2.4. Cost-Context Specification Considerations . . . . . . 23
4.3. Cost Metric: Maximum Reservable Bandwidth (bw-maxres) . . 24
4.3.1. Base Identifier . . . . . . . . . . . . . . . . . . . 24
4.3.2. Value Representation . . . . . . . . . . . . . . . . 24
4.3.3. Intended Semantics and Use . . . . . . . . . . . . . 24
4.3.4. Cost-Context Specification Considerations . . . . . . 25
5. Operational Considerations . . . . . . . . . . . . . . . . . 26
5.1. Source Considerations . . . . . . . . . . . . . . . . . . 26
5.2. Metric Timestamp Consideration . . . . . . . . . . . . . 27
5.3. Backward Compatibility Considerations . . . . . . . . . . 27
5.4. Computation Considerations . . . . . . . . . . . . . . . 27
5.4.1. Configuration Parameters Considerations . . . . . . . 27
5.4.2. Availability Considerations . . . . . . . . . . . . . 28
6. Security Considerations . . . . . . . . . . . . . . . . . . . 28
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 29
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
9.1. Normative References . . . . . . . . . . . . . . . . . . 29
9.2. Informative References . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
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1. Introduction
Cost Metric is a basic concept in Application-Layer Traffic
Optimization (ALTO). It is used in both the ALTO cost map service
and the ALTO endpoint cost service in the ALTO base protocol
[RFC7285].
Since different applications may use different cost metrics, the ALTO
base protocol introduces an ALTO Cost Metric Registry (Section 14.2
of [RFC7285]), as a systematic mechanism to allow different metrics
to be specified. For example, a delay-sensitive application may want
to use latency related metrics, and a bandwidth-sensitive application
may want to use bandwidth related metrics. However, the ALTO base
protocol has registered only a single cost metric, i.e., the generic
"routingcost" metric (see Sec. 14.2 of [RFC7285]); no latency or
bandwidth related metrics are defined.
This document registers a set of new cost metrics specified in
Table 1, to allow applications to determine "where" to connect based
on network performance criteria such as delay and bandwidth related
metrics. This document follows the guideline defined in Section 14.2
of the ALTO base protocol [RFC7285]) on registering ALTO cost
metrics. Hence it specifies the identifier, the intended semantics,
and the security considerations of each one of the metrics defined in
Table 1.
+--------------------------+-------------+-------------------+
| Metric | Definition | Origin Example |
+--------------------------+-------------+-------------------+
| One-way Delay | Section 3.1 | [RFC7679] |
| Round-trip Delay | Section 3.2 | [RFC2681] |
| Delay Variation | Section 3.3 | [RFC3393] |
| Hop Count | Section 3.4 | [RFC7285] |
| Loss Rate | Section 3.5 | [RFC7680] |
| | | |
| TCP Throughput | Section 4.1 | [RFC6349] |
| Residual Bandwidth | Section 4.2 | [RFC8570] |
| Max Reservable Bandwidth | Section 4.3 | [RFC5305] |
+------------+-----------------------------------------------+
Table 1. Cost Metrics Defined in this Document.
The purpose of this document is to ensure proper usage of the
performance metrics defined in Table 1; it does not claim novelty of
the metrics. The "Origin Example" column of Table 1 gives an example
RFC that has defined each metric.
The performance metrics can be classified into two categories: those
derived from the performance of individual packets (i.e., one-way
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delay, round-trip delay, delay variation, hop count, and loss rate),
and those related with bandwidth (TCP throughput, residual bandwidth,
and maximum reservable bandwidth). These two categories are defined
in Sections 3 and 4 respectively. Note that all metrics except round
trip delay in Table 1 are unidirectional; hence, a client will need
to query both directions if needed.
An ALTO server may provide only a subset of the metrics described in
this document. For example, those that are subject to privacy
concerns should not be provided to unauthorized ALTO clients. Hence,
all cost metrics defined in this document are optional and not all of
them need to be exposed to a given application. When an ALTO server
supports a cost metric defined in this document, it should announce
this metric in its information resource directory (IRD).
[RFC7285] specifies that cost values should be assumed by default as
JSONNumber. When defining the value representation of each metric in
Table 1, this document conforms to this specification, but specifies
additional, generic constraints on valid JSONNumbers for each metric.
For example, each metric in Table 1 will be specified as non-negative
(>= 0); Hop Count is specified to be an integer.
An ALTO server introducing these metrics should consider security
issues. As a generic security consideration on the reliability and
trust in the exposed metric values, applications SHOULD rapidly give
up using ALTO-based guidance if they detect that the exposed
information does not preserve their performance level or even
degrades it. This document discusses security considerations in more
detail in Section 6.
Following the ALTO base protocol, this document uses JSON to specify
the value type of each defined metric. See [RFC8259] for JSON data
type specification.
2. Performance Metric Attributes
When defining the metrics in Table 1, this document considers the
guidelines specified in [RFC6390], which requires fine-grained
specification of (i) Metric Name, (ii) Metric Description, (iii)
Method of Measurement or Calculation, (iv) Units of Measurement, (v)
Measurement Points, and (vi) Measurement Timing. In particular, for
each metric, this document defines (i) Metric Name, (ii) Metric
Description, and (iv) Units of Measurement. The Measurement Points
are always specified by the specific ALTO services; for example,
endpoint cost service is between the two endpoints.
On the other hand, to be able to use coarse-grained information such
as routing system information (e.g., [RFC8571]), which may not
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provide fine-grained information such as (iii) Method of Measurement
or Calculation and (vi) Measurement Timing, this document provides
context information to indicate the source of information and hence
available metric details.
2.1. Performance Metric Context: cost-context
The details of a performance metric depend on the source that defines
the metric. Specifically, this document defines four types of
information sources: "nominal", and "sla" (service level agreement),
"import", and "estimation".
For a given type of source, precise interpretation of a performance
metric value can depend on particular measurement and computation
parameters. For example, see Section 3.8 of [RFC7679] on items that
a more complete measurement-based report should include.
To make it possible to specify the source and the aforementioned
parameters, this document introduces an optional "cost-context" field
to the "cost-type" field defined by the ALTO base protocol
(Section 10.7 of [RFC7285]) as the following:
object {
CostMetric cost-metric;
CostMode cost-mode;
[CostContext cost-context;]
[JSONString description;]
} CostType;
object {
JSONString cost-source;
[JSONValue parameters;]
} CostContext;
The "cost-source" field of the "cost-context" field MUST be one of
four category values: "nominal", "sla", "import", and "estimation".
"cost-context" will not be used as a key to distinguish among
performance metrics. Hence, an ALTO information resource MUST NOT
announce multiple CostType with the same "cost-metric" and "cost-
mode". They must be placed into different information resources.
The "nominal" category indicates that the metric value is statically
configured by the underlying devices. Not all metrics have
reasonable "nominal" values. For example, throughput can have a
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nominal value, which indicates the configured transmission rate of
the devices; latency typically does not have a nominal value.
The "sla" category indicates that the metric value is derived from
some commitment which this document refers to as service-level
agreement (SLA). Some operators also use terms such as "target" or
"committed" values. For an "sla" metric, it is RECOMMENDED that the
"parameters" field provides a link to the SLA definition.
The "estimation" category indicates that the metric value is computed
through an estimation process. An ALTO server may compute
"estimation" values by retrieving and/or aggregating information from
routing protocols (e.g., [RFC8571]) and traffic measurement
management tools (e.g., TWAMP [RFC5357]), with corresponding
operational issues. A potential architecture on estimating these
metrics is shown in Figure 1 below. Section 5 will discuss in more
detail the operational issues and how a network may address them.
+--------+ +--------+ +--------+
| Client | | Client | | Client |
+----^---+ +---^----+ +---^----+
| | |
+-----------|-----------+
NBI |ALTO protocol
|
|
+--+-----+ retrieval +-----------+
| ALTO |<----------------| Routing |
| Server | and aggregation| |
| |<-------------+ | Protocols |
+--------+ | +----------+
|
| +-----------+
| |Management |
---| |
| Tool |
+-----------+
Figure 1. A framework to compute estimation to performance metrics
A particular type of "estimation" is direct "import", which indicates
that the metric value is imported directly from a specific existing
protocol or system. Specifying "import" as the source instead of the
more generic "estimation" may allow better tracking of information
flow. For an "import" metric, it is RECOMMENDED that the
"parameters" field provides details to the system from which raw data
is imported. In particular, one may notice that the set of end-to-
end metrics defined in Table 1 has a large overlap with the set
defined in [RFC8571], in the setting of IGP traffic engineering
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performance metrics for each link (i.e., unidirectional link delay,
min/max unidirectional link delay, unidirectional delay variation,
unidirectional link loss, unidirectional residual bandwidth,
unidirectional available bandwidth, unidirectional utilized
bandwidth). Hence, an ALTO server may use "import" to indicate that
its end-to-end metrics are computed from link metrics imported from
[RFC8571].
There can be multiple choices in deciding the cost-source category.
It is the operator of an ALTO server who chooses the category. If a
metric does not include a "cost-source" value, the application MUST
assume that the value of "cost-source" is the most generic
"estimation".
2.2. Performance Metric Statistics
The measurement of a performance metric often yields a set of samples
from an observation distribution ([Prometheus]), instead of a single
value. This document considers that the samples are aggregated as a
statistic when reported. Hence, each performance metric's identifier
should indicate the statistic (i.e., an aggregation operation), to
become
<metric-identifier> ::= <metric-base-identifier> [ '-' <stat> ]
where <stat> MUST be one of the following:
percentile, with letter 'p' followed by a number:
gives the p percentile. Specifically, consider the samples coming
from a random variable X. The metric returns x, relative to 100,
such that the probability of X is less than or equal to x, i.e.,
Prob(X <= x) = p/100. The number p MUST be a non-negative JSON
number in the range [0, 100] (i.e., greater than or equal to 0 and
less than or equal to 100). To avoid complex identifiers, the
number MUST NOT include the minus or the exp component (Section 6
of [RFC8259]). For example, delay-ow-p75 gives the 75% percentile
of observed one-way delay; delay-ow-p99.9 gives the 99.9%
percentile of delay. Note that some systems use quantile, which
is in the range [0, 1]. This document uses percentile to make the
identifier easier to read.
min:
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the minimal value of the observations.
max:
the maximal value of the observations.
median:
the mid point (i.e., p50) of the observations.
mean:
the arithmetic mean value of the observations.
stddev:
the standard deviation of the observations.
stdvar:
the standard variance of the observations.
If a metric has no <stat> (i.e., <metric-identifier> does not include
'-' <stat>), the metric MUST be considered as the 50 percentile
(median).
3. Packet Performance Metrics
This section introduces ALTO network performance metrics on one way
delay, round trip delay, delay variation, hop count, and packet loss
rate. They measure the "quality of experience" of the stream of
packets sent from a resource provider to a resource consumer. The
measures of each individual packet (pkt) can include the delay from
the time when the packet enters the network to the time when the
packet leaves the network (pkt.delay); the number of network hops
that the packet traverses (pkt.hopcount); and whether the packet is
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dropped before reaching the destination (pkt.dropped). The semantics
of the performance metrics defined in this section is that they are
statistics (percentiles) computed from these measures; for example,
the x-percentile of the one-way delay is the x-percentile of the set
of delays {pkt.delay} for the packets in the stream.
3.1. Cost Metric: One-Way Delay (delay-ow)
3.1.1. Base Identifier
The base identifier for this performance metric is "delay-ow".
3.1.2. Value Representation
The metric value type is a single 'JSONNumber' type value conforming
to the number specification of [RFC8259] Section 6. The unit is
expressed in milliseconds. Hence, the number can be a floating point
number to express delay that is smaller than milliseconds. The
number MUST be non-negative.
3.1.3. Intended Semantics and Use
Intended Semantics: To specify the spatial and temporal aggregated
delay of a stream of packets from the specified source and the
specified destination. The spatial aggregation level is specified in
the query context (e.g., PID to PID, or endpoint to endpoint).
Use: This metric could be used as a cost metric constraint attribute
or as a returned cost metric in the response.
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Example 1: Delay value on source-destination endpoint pairs
POST /endpointcost/lookup HTTP/1.1
Host: alto.example.com
Content-Length: TBA
Content-Type: application/alto-endpointcostparams+json
Accept:
application/alto-endpointcost+json,application/alto-error+json
{
"cost-type": {"cost-mode" : "numerical",
"cost-metric" : "delay-ow"},
"endpoints" : {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2001:db8::1234:5678"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta" :{
"cost-type": {"cost-mode" : "numerical",
"cost-metric" : "delay-ow"
}
},
"endpoint-cost-map" : {
"ipv4:192.0.2.2": {
"ipv4:192.0.2.89" : 10,
"ipv4:198.51.100.34" : 20,
"ipv6:2001:db8::1234:5678" : 30,
}
}
}
Comment: Since the "cost-type" does not include the "cost-source"
field, the values are based on "estimation". Since the identifier
does not include the -<percentile> component, the values will
represent median values.
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3.1.4. Cost-Context Specification Considerations
"nominal": Typically network one-way delay does not have a nominal
value.
"sla": Many networks provide delay in their application-level service
level agreements. It is RECOMMENDED that the "parameters" field of
an "sla" one-way delay metric provides a link (i.e., a field named
"link") to the SLA definition, if available.
"import": There can be multiple sources to import one-way delay. For
example, if the import is from [RFC8571] (by using unidirectional
link delay, min/max unidirectional link delay), it is RECOMMENDED
that "parameters" provides "protocol" as a field and "RFC8571" as the
value. During import, the server should be cognizant of potential
issues when computing an end-to-end summary statistic from link
statistics. Another example of an import source is the IPPM
framework. For IPPM, it is recommended that "parameters" provides
"protocol" as a field and "ippm" as the value; see Section 4 of [I-
D.ietf-ippm-initial-registry] for additional fields which can be
specified for "ippm" in "parameters".
"estimation": The exact estimation method is out of the scope of this
document. It is RECOMMENDED that the "parameters" field of an
"estimation" one-way delay metric provides a link ("link") to a
description of the "estimation" method.
3.2. Cost Metric: Round-trip Delay (delay-rt)
3.2.1. Base Identifier
The base identifier for this performance metric is "delay-rt".
3.2.2. Value Representation
The metric value type is a single 'JSONNumber' type value conforming
to the number specification of [RFC8259] Section 6. The number MUST
be non-negative. The unit is expressed in milliseconds.
3.2.3. Intended Semantics and Use
Intended Semantics: To specify spatial and temporal aggregated round-
trip delay between the specified source and specified destination.
The spatial aggregation level is specified in the query context
(e.g., PID to PID, or endpoint to endpoint).
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Note that it is possible for a client to query two one-way delays and
then compute the round-trip delay. The server should be cognizant of
the consistency of values.
Use: This metric could be used either as a cost metric constraint
attribute or as a returned cost metric in the response.
Example 2: Round-trip Delay of source-destination endpoint pairs
POST /endpointcost/lookup HTTP/1.1
Host: alto.example.com
Content-Length: TBA
Content-Type: application/alto-endpointcostparams+json
Accept:
application/alto-endpointcost+json,application/alto-error+json
{
"cost-type": {"cost-mode" : "numerical",
"cost-metric" : "delay-rt"},
"endpoints" : {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2001:db8::1234:5678"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta" :{
"cost-type": {"cost-mode" : "numerical",
"cost-metric" : "delay-rt"
}
},
"endpoint-cost-map" : {
"ipv4:192.0.2.2": {
"ipv4:192.0.2.89" : 4,
"ipv4:198.51.100.34" : 3,
"ipv6:2001:db8::1234:5678" : 2,
}
}
}
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3.2.4. Cost-Context Specification Considerations
"nominal": Typically network round-trip delay does not have a nominal
value.
"sla": It is RECOMMENDED that the "parameters" field of an "sla"
round-trip delay metric provides a link ("link") to the SLA
definition.
"import": There can be multiple sources to import round-trip delay.
If the import is from [RFC8571] (by using unidirectional link delay,
min/max unidirectional link delay), it is RECOMMENDED that
"parameters" provides "protocol" as a field and "RFC8571" as the
value; see Section 3.1.4 for discussions on summing up link metrics
to obtain end-to-end metrics. If the import is from the IPPM
framework, it is recommended that "parameters" provides "protocol" as
a field and "ippm" as the value; see Section 4 of [I-D.ietf-ippm-
initial-registry] for additional fields which can be specified for
"ippm" in "parameters".
"estimation": The exact estimation method is out of the scope of this
document. It is RECOMMENDED that the "parameters" field of an
"estimation" round-trip delay metric provides a link ("link") to a
description of the "estimation" method.
3.3. Cost Metric: Delay Variation (delay-variation)
3.3.1. Base Identifier
The base identifier for this performance metric is "delay-variation".
3.3.2. Value Representation
The metric value type is a single 'JSONNumber' type value conforming
to the number specification of [RFC8259] Section 6. The number MUST
be non-negative. The unit is expressed in milliseconds.
3.3.3. Intended Semantics and Use
Intended Semantics: To specify spatial and temporal aggregated delay
variation (also called delay jitter)) with respect to the minimum
delay observed on the stream over the specified source and
destination. The spatial aggregation level is specified in the query
context (e.g., PID to PID, or endpoint to endpoint).
Note that in statistics, variations are typically evaluated by the
distance from samples relative to the mean. In networking context,
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it is more commonly defined from samples relative to the min. This
definition follows the networking convention.
Use: This metric could be used either as a cost metric constraint
attribute or as a returned cost metric in the response.
Example 3: Delay variation value on source-destination endpoint pairs
POST /endpointcost/lookup HTTP/1.1
Host: alto.example.com
Content-Length: TBA
Content-Type: application/alto-endpointcostparams+json
Accept:
application/alto-endpointcost+json,application/alto-error+json
{
"cost-type": {"cost-mode" : "numerical",
"cost-metric" : "delay-variation"},
"endpoints" : {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2001:db8::1234:5678"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta": {
"cost type": {
"cost-mode": "numerical",
"cost-metric":"delay-variation"
}
},
"endpoint-cost-map": {
"ipv4:192.0.2.2": {
"ipv4:192.0.2.89" : 0
"ipv4:198.51.100.34" : 1
"ipv6:2001:db8::1234:5678" : 5
}
}
}
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3.3.4. Cost-Context Specification Considerations
"nominal": Typically network delay variation does not have a nominal
value.
"sla": It is RECOMMENDED that the "parameters" field of an "sla"
delay variation metric provides a link ("link") to the SLA
definition.
"import": There can be multiple sources to import delay variation.
If the import is from [RFC8571] (by using unidirectional delay
variation), it is RECOMMENDED that "parameters" provides "protocol"
as a field and "RFC8571" as the value; see Section 3.1.4 for
discussions on summing up link metrics to obtain end-to-end metrics.
If the import is from the IPPM framework, it is recommended that
"parameters" provides "protocol" as a field and "ippm" as the value;
see Section 4 of [I-D.ietf-ippm-initial-registry] for additional
fields which can be specified for "ippm" in "parameters".
"estimation": The exact estimation method is out of the scope of this
document. It is RECOMMENDED that the "parameters" field of an
"estimation" delay variation metric provides a link ("link") to a
description of the "estimation" method.
3.4. Cost Metric: Hop Count (hopcount)
The metric hopcount is mentioned in [RFC7285] Section 9.2.3 as an
example. This section further clarifies its properties.
3.4.1. Base Identifier
The base identifier for this performance metric is "hopcount".
3.4.2. Value Representation
The metric value type is a single 'JSONNumber' type value conforming
to the number specification of [RFC8259] Section 6. The number MUST
be a non-negative integer (greater than or equal to 0). The value
represents the number of hops.
3.4.3. Intended Semantics and Use
Intended Semantics: To specify the number of hops in the path from
the specified source to the specified destination. The hop count is
a basic measurement of distance in a network and can be exposed as
the number of router hops computed from the routing protocols
originating this information. The spatial aggregation level is
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specified in the query context (e.g., PID to PID, or endpoint to
endpoint).
Use: This metric could be used as a cost metric constraint attribute
or as a returned cost metric in the response.
Example 4: hopcount value on source-destination endpoint pairs
POST /endpointcost/lookup HTTP/1.1
Host: alto.example.com
Content-Length: TBA
Content-Type: application/alto-endpointcostparams+json
Accept:
application/alto-endpointcost+json,application/alto-error+json
{
"cost-type": {"cost-mode" : "numerical",
"cost-metric" : "hopcount"},
"endpoints" : {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2001:db8::1234:5678"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta": {
"cost type": {
"cost-mode": "numerical",
"cost-metric":"hopcount"}
}
},
"endpoint-cost-map": {
"ipv4:192.0.2.2": {
"ipv4:192.0.2.89" : 5,
"ipv4:198.51.100.34": 3,
"ipv6:2001:db8::1234:5678" : 2,
}
}
}
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3.4.4. Cost-Context Specification Considerations
"nominal": Typically hop count does not have a nominal value.
"sla": Typically hop count does not have an SLA value.
"import": There can be multiple sources to import hop count, such as
from IGP routing protocols.
"estimation": The exact estimation method is out of the scope of this
document. It is RECOMMENDED that the "parameters" field of an
"estimation" hop count metric provides a link ("link") to a
description of the "estimation" method.
3.5. Cost Metric: Loss Rate (lossrate)
3.5.1. Base Identifier
The base identifier for this performance metric is "lossrate".
3.5.2. Value Representation
The metric value type is a single 'JSONNumber' type value conforming
to the number specification of [RFC8259] Section 6. The number MUST
be non-negative. The value represents the percentage of packet
losses.
3.5.3. Intended Semantics and Use
Intended Semantics: To specify spatial and temporal aggregated packet
loss rate from the specified source and the specified destination.
The spatial aggregation level is specified in the query context
(e.g., PID to PID, or endpoint to endpoint).
Use: This metric could be used as a cost metric constraint attribute
or as a returned cost metric in the response.
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Example 5: Loss rate value on source-destination endpoint pairs
POST /endpointcost/lookup HTTP/1.1
Host: alto.example.com
Content-Length: TBA
Content-Type: application/alto-endpointcostparams+json
Accept:
application/alto-endpointcost+json,application/alto-error+json
{
"cost-type": {"cost-mode" : "numerical",
"cost-metric" : "lossrate"
},
"endpoints" : {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2001:db8::1234:5678"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta": {
"cost-type": {
"cost-mode": "numerical",
"cost-metric":"lossrate"
}
},
"endpoint-cost-map": {
"ipv4:192.0.2.2": {
"ipv4:192.0.2.89" : 0,
"ipv4:198.51.100.34": 0,
"ipv6:2001:db8::1234:5678" : 0,
}
}
}
3.5.4. Cost-Context Specification Considerations
"nominal": Typically packet loss rate does not have a nominal value,
although some networks may specify zero losses.
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"sla": It is RECOMMENDED that the "parameters" field of an "sla"
packet loss rate provides a link ("link") to the SLA definition.
"import": There can be multiple sources to import packet loss rate.
If the import is from [RFC8571] (by using unidirectional link loss),
it is RECOMMENDED that "parameters" provides "protocol" as a field
and "RFC8571" as the value; see Section 3.1.4 for discussions on
summing up link metrics to obtain end-to-end metrics. If the import
is from the IPPM framework, it is recommended that "parameters"
provides "protocol" as a field and "ippm" as the value; see Section 4
of [I-D.ietf-ippm-initial-registry] for additional fields which can
be specified for "ippm" in "parameters".
"estimation": The exact estimation method is out of the scope of this
document. It is RECOMMENDED that the "parameters" field of an
"estimation" packet loss rate metric provides a link ("link") to a
description of the "estimation" method.
4. Bandwidth Performance Metrics
This section introduces three bandwidth related metrics. Given a
specified source to a specified destination, these metrics reflect
the volume of traffic that the network can carry from the source to
the destination.
4.1. Cost Metric: TCP Throughput (tput)
4.1.1. Base Identifier
The base identifier for this performance metric is "tput".
4.1.2. Value Representation
The metric value type is a single 'JSONNumber' type value conforming
to the number specification of [RFC8259] Section 6. The number MUST
be non-negative. The unit is bytes per second.
4.1.3. Intended Semantics and Use
Intended Semantics: To give the throughput of a TCP flow from the
specified source to the specified destination. The spatial
aggregation level is specified in the query context (e.g., PID to
PID, or endpoint to endpoint).
Use: This metric could be used as a cost metric constraint attribute
or as a returned cost metric in the response.
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Example 5: TCP throughput value on source-destination endpoint pairs
POST /endpointcost/lookup HTTP/1.1
Host: alto.example.com
Content-Length: TBA
Content-Type: application/alto-endpointcostparams+json
Accept:
application/alto-endpointcost+json,application/alto-error+json
{
"cost-type": {"cost-mode" : "numerical",
"cost-metric" : "tput"},
"endpoints" : {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2001:db8::1234:5678"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta": {
"cost type": {
"cost-mode": "numerical",
"cost-metric":"tput"
}
}
"endpoint-cost-map": {
"ipv4:192.0.2.2": {
"ipv4:192.0.2.89" : 256000,
"ipv4:198.51.100.34": 128000,
"ipv6:2001:db8::1234:5678" : 428000,
}
}
4.1.4. Cost-Context Specification Considerations
"nominal": Typically TCP throughput does not have a nominal value.
"sla": Typically TCP throughput does not have an SLA value.
"import": Typically there is not a routing protocol through which one
can import TCP throughput. If the import is from the IPPM framework,
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it is recommended that "parameters" provides "protocol" as a field
and "ippm" as the value; see Section 4 of [I-D.ietf-ippm-initial-
registry] for additional fields which can be specified for "ippm" in
"parameters".
"estimation": The exact estimation method is out of the scope of this
document. See [Prophet] for a method to estimate TCP throughput. It
is RECOMMENDED that the "parameters" field of an "estimation" TCP
throughput metric provides a link ("link") to a description of the
"estimation" method.
4.2. Cost Metric: Residual Bandwidth (bw-residual)
4.2.1. Base Identifier
The base identifier for this performance metric is "bw-residual".
4.2.2. Value Representation
The metric value type is a single 'JSONNumber' type value that is
non-negative. The unit of measurement is bytes per second.
4.2.3. Intended Semantics and Use
Intended Semantics: To specify spatial and temporal residual
bandwidth from the specified source and the specified destination.
The value is calculated by subtracting tunnel reservations from
Maximum Bandwidth (motivated from [RFC8570], Section 4.5). The
spatial aggregation unit is specified in the query context (e.g., PID
to PID, or endpoint to endpoint).
Use: This metric could be used either as a cost metric constraint
attribute or as a returned cost metric in the response.
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Example 7: bw-residual value on source-destination endpoint pairs
POST/ endpointcost/lookup HTTP/1.1
Host: alto.example.com
Content-Length: TBA
Content-Type: application/alto-endpointcostparams+json
Accept:
application/alto-endpointcost+json,application/alto-error+json
{
"cost-type": { "cost-mode": "numerical",
"cost-metric": "bw-residual"},
"endpoints": {
"srcs": [ "ipv4 : 192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2001:db8::1234:5678"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta": {
"cost-type" {
"cost-mode": "numerical",
"cost-metric": "bw-residual"
}
},
"endpoint-cost-map" {
"ipv4:192.0.2.2" {
"ipv4:192.0.2.89" : 0,
"ipv4:198.51.100.34": 2000,
"ipv6:2001:db8::1234:5678" : 5000,
}
}
}
4.2.4. Cost-Context Specification Considerations
"nominal": Typically residual bandwidth does not have a nominal
value.
"sla": Typically residual bandwidth does not have an "sla" value.
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"import": There can be multiple sources to import residual bandwidth.
If the import is from [RFC8571] (by using unidirectional residual
bandwidth), it is RECOMMENDED that "parameters" provides "protocol"
as a field and "RFC8571" as the value. The server should be
cognizant of issues when computing end-to-end summary statistics from
link statistics. For example, the min of the end-to-end path
residual bandwidth is the min of all links on the path.
"estimation": The exact estimation method is out of the scope of this
document. It is RECOMMENDED that the "parameters" field of an
"estimation" residual bandwidth metric provides a link ("link") to a
description of the "estimation" method.
4.3. Cost Metric: Maximum Reservable Bandwidth (bw-maxres)
4.3.1. Base Identifier
The base identifier for this performance metric is "bw-maxres".
4.3.2. Value Representation
The metric value type is a single 'JSONNumber' type value that is
non-negative. The unit of measurement is bytes per second.
4.3.3. Intended Semantics and Use
Intended Semantics: To specify spatial and temporal maximum
reservable bandwidth from the specified source to the specified
destination. The value corresponds to the maximum bandwidth that can
be reserved (motivated from [RFC3630] Section 2.5.7). The spatial
aggregation unit is specified in the query context (e.g., PID to PID,
or endpoint to endpoint).
Use: This metric could be used either as a cost metric constraint
attribute or as a returned cost metric in the response.
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Example 6: bw-maxres value on source-destination endpoint pairs
POST/ endpointcost/lookup HTTP/1.1
Host: alto.example.com
Content-Length: TBA
Content-Type: application/alto-endpointcostparams+json
Accept:
application/alto-endpointcost+json,application/alto-error+json
{
"cost-type" { "cost-mode": "numerical",
"cost-metric": "bw-maxres"},
"endpoints": {
"srcs": [ "ipv4 : 192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2001:db8::1234:5678"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta": {
"cost-type": {
"cost-mode": "numerical",
"cost-metric": "bw-maxres"
}
},
"endpoint-cost-map": {
"ipv4:192.0.2.2" {
"ipv4:192.0.2.89" : 0,
"ipv4:198.51.100.34": 2000,
"ipv6:2001:db8::1234:5678" : 5000,
}
}
}
4.3.4. Cost-Context Specification Considerations
"nominal": Typically maximum reservable bandwidth does not have a
nominal value.
"sla": Typically maximum reservable bandwidth does not have an "sla"
value.
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"import": There can be multiple sources to import maximum reservable
bandwidth. For example, Maximum reservable bandwidth is defined by
IS-IS/OSPF TE, and measures the reservable bandwidth between two
directly connected IS-IS neighbors or OSPF neighbors; see Section 3.5
of [RFC5305]. If the import is from [RFC8571] (by using
unidirectional maximum reservable bandwidth), it is RECOMMENDED that
"parameters" provides "protocol" as a field and "RFC8571" as the
value.
"estimation": The exact estimation method is out of the scope of this
document. It is RECOMMENDED that the "parameters" field of an
"estimation" maximum reservable bandwidth metric provides a link
("link") to a description of the "estimation" method.
5. Operational Considerations
The exact measurement infrastructure, measurement condition, and
computation algorithms can vary from different networks, and are
outside the scope of this document. Both the ALTO server and the
ALTO clients, however, need to be cognizant of the operational issues
discussed below.
Also, the performance metrics specified in this document are similar,
in that they may use similar data sources and have similar issues in
their calculation. Hence, we specify common issues unless one metric
has its unique challenges.
5.1. Source Considerations
The addition of the "cost-source" field is to solve a key issue: An
ALTO server needs data sources to compute the cost metrics described
in this document, and an ALTO client needs to know the data sources
to better interpret the values.
To avoid too fine-grained information, this document introduces
"cost-source" to indicate only the high-level type of data sources:
"estimation" or "sla", where "estimation" is a type of measurement
data source, and "sla" is a type that is more based on policy.
For estimation, for example, the ALTO server may use log servers or
the OAM system as its data source as recommended by [RFC7971]. In
particular, the cost metrics defined in this document can be computed
using routing systems as the data sources.
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5.2. Metric Timestamp Consideration
Despite the introduction of the additional cost-context information,
the metrics do not have a field to indicate the timestamps of the
data used to compute the metrics. To indicate this attribute, the
ALTO server SHOULD return HTTP "Last-Modified", to indicate the
freshness of the data used to compute the performance metrics.
If the ALTO client obtains updates through an incremental update
mechanism [RFC8895]), the client SHOULD assume that the metric is
computed using a snapshot at the time that is approximated by the
receiving time.
5.3. Backward Compatibility Considerations
One potential issue introduced by the optional "cost-source" field is
backward compatibility. Consider that an IRD which defines two cost-
types with the same "cost-mode" and "cost-metric", but one with
"cost-source" being "estimation" and the other being "sla". Then an
ALTO client that is not aware of the extension will not be able to
distinguish between these two types. A similar issue can arise even
with a single cost-type, whose "cost-source" is "sla": an ALTO client
that is not aware of this extension will ignore this field and
consider the metric estimation.
To address this issue, the only defined "routingcost" metric can be
only "estimation".
5.4. Computation Considerations
The metric values exposed by an ALTO server may result from
additional processing on measurements from data sources to compute
exposed metrics. This may involve data processing tasks such as
aggregating the results across multiple systems, removing outliers,
and creating additional statistics. There are two challenges on the
computation of ALTO performance metrics.
5.4.1. Configuration Parameters Considerations
Performance metrics often depend on configuration parameters. For
example, the value of packet loss rate depends on the measurement
interval and varies over time. To handle this issue, an ALTO server
may collect data on time periods covering the previous and current
time or only collect data on present time. The ALTO server may
further aggregate these data to provide an abstract and unified view
that can be more useful to applications. To make the ALTO client
better understand how to use these performance data, the ALTO server
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may provide the client with the validity period of the exposed metric
values.
5.4.2. Availability Considerations
Applications value information relating to bandwidth availability,
whereas bandwidth related metrics can often be measured only at the
link level. This document specifies a set of link-level bandwidth
related values that may be exposed as such by an ALTO server. The
server may also expose other metrics derived from their aggregation,
using different levels of endpoint granularity, e.g., link endpoints
or session endpoints. The metric specifications may also expose the
utilized aggregation laws.
6. Security Considerations
The properties defined in this document present no security
considerations beyond those in Section 15 of the base ALTO
specification [RFC7285].
However, concerns addressed in Sections "15.1 Authenticity and
Integrity of ALTO Information", "15.2 Potential Undesirable Guidance
from Authenticated ALTO Information", and "15.3 Confidentiality of
ALTO Information" remain of utmost importance. Indeed, TE
performance is a highly sensitive ISP information; therefore, sharing
TE metric values in numerical mode requires full mutual confidence
between the entities managing the ALTO server and the ALTO client.
ALTO servers will most likely distribute numerical TE performance to
ALTO clients under strict and formal mutual trust agreements. On the
other hand, ALTO clients must be cognizant on the risks attached to
such information that they would have acquired outside formal
conditions of mutual trust.
7. IANA Considerations
IANA has created and now maintains the "ALTO Cost Metric Registry",
listed in Section 14.2, Table 3 of [RFC7285]. This registry is
located at <http://www.iana.org/assignments/alto-protocol/alto-
protocol.xhtml#cost-metrics>. This document requests to add the
following entries to "ALTO Cost Metric Registry".
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+-----------------+--------------------+
| Identifier | Intended Semantics |
+-----------------+--------------------+
| delay-ow | See Section 3.1 |
| delay-rt | See Section 3.2 |
| delay-variation | See Section 3.3 |
| hopcount | See Section 3.4 |
| lossrate | See Section 3.5 |
| tput | See Section 4.1 |
| bw-residual | See Section 4.2 |
| bw-maxres | See Section 4.3 |
+-----------------+--------------------+
This document requests the creation of the "ALTO Cost Source
Registry" with the following currently defined values:
+------------+-----------------------------+
| Identifier | Intended Semantics |
+------------+-----------------------------+
| nominal | Values in nominal cases |
| sla | Values reflecting service |
| | level agreement |
| import | Values from a given protocol|
| estimation | Values by estimation |
+------------+-----------------------------+
8. Acknowledgments
The authors of this document would also like to thank Brian Trammell,
Haizhou Du, Kai Gao, Lili Liu, Geng Li, Danny Alex Lachos Perez for
the reviews and comments.
9. References
9.1. 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>.
[RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New
Performance Metric Development", BCP 170, RFC 6390, DOI
10.17487/RFC6390, October 2011, <https://www.rfc-
editor.org/info/rfc6390>.
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[RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S.,
Previdi, S., Roome, W., Shalunov, S., and R. Woundy,
"Application-Layer Traffic Optimization (ALTO) Protocol",
RFC 7285, DOI 10.17487/RFC7285, September 2014,
<https://www.rfc-editor.org/info/rfc7285>.
[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>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259, DOI 10.17487/
RFC8259, December 2017, <https://www.rfc-editor.org/info/
rfc8259>.
[RFC8895] Roome, W. and Y. Yang, "Application-Layer Traffic
Optimization (ALTO) Incremental Updates Using Server-Sent
Events (SSE)", RFC 8895, DOI 10.17487/RFC8895, November
2020, <https://www.rfc-editor.org/info/rfc8895>.
9.2. Informative References
[I-D.ietf-ippm-initial-registry]
Morton, A., Bagnulo, M., Eardley, P., and K. D'Souza,
"Initial Performance Metrics Registry Entries", draft-
ietf-ippm-initial-registry-16 (work in progress), March
2020.
[Prometheus]
Volz, J. and B. Rabenstein, "Prometheus: A Next-Generation
Monitoring System", 2015.
[Prophet] Gao, K., Zhang, J., and YR. Yang, "Prophet: Fast, Accurate
Throughput Prediction with Reactive Flows", ACM/IEEE
Transactions on Networking July, 2020.
[RFC2681] Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
Delay Metric for IPPM", RFC 2681, DOI 10.17487/RFC2681,
September 1999, <https://www.rfc-editor.org/info/rfc2681>.
[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
Metric for IP Performance Metrics (IPPM)", RFC 3393, DOI
10.17487/RFC3393, November 2002, <https://www.rfc-
editor.org/info/rfc3393>.
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[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, DOI
10.17487/RFC3630, September 2003, <https://www.rfc-
editor.org/info/rfc3630>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <https://www.rfc-editor.org/info/rfc5305>.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, DOI 10.17487/RFC5357, October 2008,
<https://www.rfc-editor.org/info/rfc5357>.
[RFC6349] Constantine, B., Forget, G., Geib, R., and R. Schrage,
"Framework for TCP Throughput Testing", RFC 6349, DOI
10.17487/RFC6349, August 2011, <https://www.rfc-
editor.org/info/rfc6349>.
[RFC7679] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
Ed., "A One-Way Delay Metric for IP Performance Metrics
(IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January
2016, <https://www.rfc-editor.org/info/rfc7679>.
[RFC7680] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
Ed., "A One-Way Loss Metric for IP Performance Metrics
(IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January
2016, <https://www.rfc-editor.org/info/rfc7680>.
[RFC7971] Stiemerling, M., Kiesel, S., Scharf, M., Seidel, H., and
S. Previdi, "Application-Layer Traffic Optimization (ALTO)
Deployment Considerations", RFC 7971, DOI 10.17487/
RFC7971, October 2016, <https://www.rfc-editor.org/info/
rfc7971>.
[RFC8570] Ginsberg, L., Ed., Previdi, S., Ed., Giacalone, S., Ward,
D., Drake, J., and Q. Wu, "IS-IS Traffic Engineering (TE)
Metric Extensions", RFC 8570, DOI 10.17487/RFC8570, March
2019, <https://www.rfc-editor.org/info/rfc8570>.
[RFC8571] Ginsberg, L., Ed., Previdi, S., Wu, Q., Tantsura, J., and
C. Filsfils, "BGP - Link State (BGP-LS) Advertisement of
IGP Traffic Engineering Performance Metric Extensions",
RFC 8571, DOI 10.17487/RFC8571, March 2019,
<https://www.rfc-editor.org/info/rfc8571>.
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Authors' Addresses
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
CHINA
Email: bill.wu@huawei.com
Y. Richard Yang
Yale University
51 Prospect St
New Haven, CT 06520
USA
Email: yry@cs.yale.edu
Young Lee
Samsung
1700 Alma Drive, Suite 500
Plano, TX 75075
USA
Email: young.lee@gmail.com
Dhruv Dhody
Huawei
Leela Palace
Bangalore, Karnataka 560008
INDIA
Email: dhruv.ietf@gmail.com
Sabine Randriamasy
Nokia Bell Labs
Route de Villejust
Nozay 91460
FRANCE
Email: sabine.randriamasy@nokia-bell-labs.com
Wu, et al. Expires August 7, 2021 [Page 32]
Internet-Draft ALTO Performance Cost Metrics February 2021
Luis Miguel Contreras Murillo
Telefonica
Madrid
SPAIN
Email: luismiguel.contrerasmurillo@telefonica.com
Wu, et al. Expires August 7, 2021 [Page 33]