ALTO Performance Cost Metrics
draft-ietf-alto-performance-metrics-09
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9439.
|
|
|---|---|---|---|
| Authors | Qin Wu , Y. Richard Yang , Dhruv Dhody , Sabine Randriamasy , Luis M. Contreras | ||
| Last updated | 2020-03-09 (Latest revision 2019-11-04) | ||
| Replaces | draft-wu-alto-te-metrics | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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draft-ietf-alto-performance-metrics-09
ALTO Working Group Q. Wu
Internet-Draft Huawei
Intended status: Standards Track Y. Yang
Expires: September 10, 2020 Yale University
D. Dhody
Huawei
S. Randriamasy
Nokia Bell Labs
L. Contreras
Telefonica
March 09, 2020
ALTO Performance Cost Metrics
draft-ietf-alto-performance-metrics-09
Abstract
Cost metric is a basic concept in Application-Layer Traffic
Optimization (ALTO), and is used in basic ALTO services including
both the cost map service and the endpoint cost service.
Different applications may use different cost metrics, but the ALTO
base protocol [RFC7285] documents only one single cost metric, i.e.,
the generic "routingcost" metric; see Sec. 14.2 of [RFC7285]. Hence,
if the resource consumer of an application prefers a resource
provider that offers low-delay delivery to the resource consumer, the
base protocol does not define the cost metric to be used.
ALTO cost metrics can be generic metrics and this document focuses on
network performance metrics, including network delay, jitter, packet
loss, hop count, and bandwidth.
When using an ALTO performance metric, an application may need
additional contextual information beyond the metric value. For
example, whether the metric is an estimation based on measurements or
a service-level agreement (SLA) can define the meaning of a
performance metric. Hence, this document introduces an additional
"cost-context" field to the ALTO "cost-type" field to convey such
information. To report an estimated value of a performance metric,
the ALTO server may derive and aggregate from routing protocols with
different granularity and scope, such as BGP-LS, OSPF-TE and ISIS-TE,
or from end-to-end traffic management tools. These metrics may then
be exposed by an ALTO Server to allow applications to determine
"where" to connect based on network performance criteria.
Requirements Language The key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
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and "OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 10, 2020.
Copyright Notice
Copyright (c) 2020 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
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Performance Metric Context: cost-context . . . . . . . . . . 5
3. Network Performance Cost Metrics . . . . . . . . . . . . . . 7
3.1. Cost Metric: One Way Delay (owdelay) . . . . . . . . . . 7
3.1.1. Identifier . . . . . . . . . . . . . . . . . . . . . 7
3.1.2. Value Representation . . . . . . . . . . . . . . . . 7
3.1.3. Intended Semantics and Use . . . . . . . . . . . . . 7
3.1.4. Measurement Considerations and Parameters . . . . . . 8
3.2. Cost Metric: RoundTrip Time (rtt) . . . . . . . . . . . . 9
3.2.1. Identifier . . . . . . . . . . . . . . . . . . . . . 9
3.2.2. Value Representation . . . . . . . . . . . . . . . . 9
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3.2.3. Intended Semantics and Use . . . . . . . . . . . . . 9
3.2.4. Measurement Considerations and Parameters . . . . . . 10
3.3. Cost Metric: Packet Delay Variation (pdv) . . . . . . . . 11
3.3.1. Identifier . . . . . . . . . . . . . . . . . . . . . 11
3.3.2. Value Representation . . . . . . . . . . . . . . . . 11
3.3.3. Intended Semantics and Use . . . . . . . . . . . . . 11
3.3.4. Measurement Considerations and Parameters . . . . . . 12
3.4. Cost Metric: Hop Count . . . . . . . . . . . . . . . . . 13
3.4.1. Identifier . . . . . . . . . . . . . . . . . . . . . 13
3.4.2. Value Representation . . . . . . . . . . . . . . . . 13
3.4.3. Intended Semantics and Use . . . . . . . . . . . . . 13
3.4.4. Measurement Considerations and Parameters . . . . . . 14
3.5. Cost Metric: Packet Loss . . . . . . . . . . . . . . . . 15
3.5.1. Identifier . . . . . . . . . . . . . . . . . . . . . 15
3.5.2. Value Representation . . . . . . . . . . . . . . . . 15
3.5.3. Intended Semantics and Use . . . . . . . . . . . . . 15
3.5.4. Measurement Considerations and Parameters . . . . . . 16
3.6. Cost Metric: Throughput . . . . . . . . . . . . . . . . . 16
3.6.1. Identifier . . . . . . . . . . . . . . . . . . . . . 16
3.6.2. Value Representation . . . . . . . . . . . . . . . . 16
3.6.3. Intended Semantics and Use . . . . . . . . . . . . . 16
3.6.4. Measurement Considerations and Parameters . . . . . . 17
4. Traffic Engineering Performance Cost Metrics . . . . . . . . 18
4.1. Cost Metric: Link Maximum Reservable Bandwidth . . . . . 18
4.1.1. Identifier . . . . . . . . . . . . . . . . . . . . . 18
4.1.2. Value Representation . . . . . . . . . . . . . . . . 18
4.1.3. Intended Semantics and Use . . . . . . . . . . . . . 18
4.1.4. Measurement Considerations and Parameters . . . . . . 19
4.2. Cost Metric: Link Residue Bandwidth . . . . . . . . . . . 20
4.2.1. Identifier . . . . . . . . . . . . . . . . . . . . . 20
4.2.2. Value Representation . . . . . . . . . . . . . . . . 20
4.2.3. Intended Semantics and Use . . . . . . . . . . . . . 20
4.2.4. Measurement Considerations and Parameters . . . . . . 21
5. Operational Considerations . . . . . . . . . . . . . . . . . 22
5.1. Source Considerations . . . . . . . . . . . . . . . . . . 22
5.2. Backward Compatibility Considerations . . . . . . . . . . 23
5.3. Computation Considerations . . . . . . . . . . . . . . . 23
5.3.1. Configuration Parameters Considerations . . . . . . . 23
5.3.2. Availability Considerations . . . . . . . . . . . . . 23
6. Security Considerations . . . . . . . . . . . . . . . . . . . 24
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
9.1. Normative References . . . . . . . . . . . . . . . . . . 25
9.2. Informative References . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
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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, to allow applications to request
network cost metrics.
Different applications may use different cost metrics. Hence, the
ALTO base protocol [RFC7285] 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. The
ALTO base protocol [RFC7285], however, has registered only one single
cost metric, i.e., the generic "routingcost" metric; no latency or
bandwidth related metrics are defined.
This document registers a set of new cost metrics specified in
Table 1, to support the aforementioned applications, to allow them to
better determine "where" to connect based on network performance
criteria. This document follows the guideline (Section 14.2 of
[RFC7285]) of the ALTO base protocol 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 |
+--------------------------+-------------+-------------+
| One Way Delay | Section 2.1 | [RFC7679] |
| Round Trip Delay | Section 2.2 | [RFC2681] |
| Packet Delay Variation | Section 2.3 | [RFC3393] |
| Hop Count | Section 2.4 | [RFC7285] |
| Packet Loss | Section 2.5 | [RFC7680] |
| Throughput | Section 2.6 | [RFC6349] |
| Max Reservable Bandwidth | Section 3.1 | [RFC5305] |
| Residue Bandwidth | Section 3.2 | [RFC7810] |
+------------+-----------------------------------------+
Table 1. Cost Metrics Defined in this Document.
The purpose of this document is to ensure proper usage of the metrics
by ALTO clients. It does not claim novelty of the metrics; see
Table 1 for the source definition of each metric.
An ALTO server may provide only a subset of the cost metrics
described in this document. Hence, all cost metrics defined in this
document are optional and not all of them need to be exposed to a
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given application. For example, those that are subject to privacy
concerns should not be provided to unauthorized ALTO clients.
When an ALTO server supports a cost metric defined in this document,
it MUST announce this metric in its information resource directory
(IRD).
An ALTO server introducing these metrics should also 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. We discuss security considerations in more details
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 Context: cost-context
The semantics of a performance metric depends on the context.
Specifically, this document defines three sources when defining
performance metrics: "estimation", "nominal", and "sla".
Even given the source, precise interpretation of a performance metric
value, if needed, depends on an additional set of measurement and
computation parameters. For example, see Section 3.8 of [RFC7679] on
items which a more complete measurement-based report should include.
To make it possible to specify both the source and the additional
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:
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object {
CostMetric cost-metric;
CostMode cost-mode;
[CostContext cost-context;]
[JSONString description;]
} CostType;
object {
JSONString cost-source;
[JSONValue parameters;]
} CostContext;
The "cost-source" MUST be one of only three values: "estimation",
"nominal", and "sla". If a "cost-type" does not include the optional
"cost-context" field which includes the "cost-source" field, the
application MUST assume that the value of "cost-source" is
"estimation".
An ALTO server may compute "estimation" values by retrieving and/or
aggregating information from routing protocols or other traffic
measurement management tools, with corresponding operational issues.
A potential architecture on estimating these metrics is shown in
Figure 1 below. In Section 5, we 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| |
| |<-------------+ | Protocol|
+--------+ | +---------+
|
| +---------+
| |Management
---| |
| Tool |
+---------+
Figure 1. Potential framework to compute performance cost metrics
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3. Network Performance Cost Metrics
This section introduces generic ALTO network performance metrics such
as one way delay, round trip delay, hop count, packet loss, and
throughput.
3.1. Cost Metric: One Way Delay (owdelay)
3.1.1. Identifier
The identifier for this performance metric is "owdelay".
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 number MUST
be non-negative. The unit is expressed in milliseconds.
3.1.3. Intended Semantics and Use
Intended Semantics: To specify spatial and temporal aggregated delay
of a stream of packets exchanged between the specified source and
destination or the time that the packet spends to travel from source
to 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
used either together with cost metric attribute 'routingcost' or on
its own 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" : "owdelay"},
"endpoints" : {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2000::1:2345:6789:abcd"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta" :{
"cost-type": {"cost-mode" : "numerical",
"cost-metric" : "owdelay"
}
},
"endpoint-cost-map" : {
"ipv4:192.0.2.2": {
"ipv4:192.0.2.89" : 10,
"ipv4:198.51.100.34" : 20,
"ipv6:2000::1:2345:6789:abcd" : 30,
}
}
}
Comment: Since the "cost-type" does not include the "cost-source"
field, the values are based on "estimation".
3.1.4. Measurement Considerations and Parameters
See Section 4 of [I-D.ietf-ippm-initial-registry] for measurement
considerations and parameters which may be specified in "parameters".
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Note that the "parameters" field is an optional field providing non-
normative information.
3.2. Cost Metric: RoundTrip Time (rtt)
3.2.1. Identifier
The identifier for this performance metric is "rtt".
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 destination or the time
that the packet spends to travel from source to destination and then
from destination to source. 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
used either together with cost metric attribute 'routingcost' or on
its own or as a returned cost metric in the response.
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Example 2: Roundtrip 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" : "rtt"},
"endpoints" : {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2000::1:2345:6789:abcd"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta" :{
"cost-type": {"cost-mode" : "numerical",
"cost-metric" : "rtt"
}
},
"endpoint-cost-map" : {
"ipv4:192.0.2.2": {
"ipv4:192.0.2.89" : 4,
"ipv4:198.51.100.34" : 3,
"ipv6:2000::1:2345:6789:abcd" : 2,
}
}
}
3.2.4. Measurement Considerations and Parameters
See Section 4 of [I-D.ietf-ippm-initial-registry] for measurement
considerations and parameters which may be specified in "parameters".
Note that the "parameters" field is an optional field providing non-
normative information.
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3.3. Cost Metric: Packet Delay Variation (pdv)
3.3.1. Identifier
The identifier for this performance metric is "pdv".
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 jitter
(packet delay variation) 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).
Use: This metric could be used as a cost metric constraint attribute
used either together with cost metric attribute 'routingcost' or on
its own or as a returned cost metric in the response.
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Example 3: PDV 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" : "pdv"},
"endpoints" : {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2000::1:2345:6789:abcd"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta": {
"cost type": {
"cost-mode": "numerical",
"cost-metric":"delayjitter"
}
},
"endpoint-cost-map": {
"ipv4:192.0.2.2": {
"ipv4:192.0.2.89" : 0
"ipv4:198.51.100.34" : 1
"ipv6:2000::1:2345:6789:abcd" : 5
}
}
}
3.3.4. Measurement Considerations and Parameters
See Section 5 of [I-D.ietf-ippm-initial-registry] for measurement
considerations and parameters which may be specified in "parameters".
Note that the "parameters" field is an optional field providing non-
normative information.
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3.4. Cost Metric: Hop Count
The metric hopcount is mentioned in [RFC7285] Section 9.2.3 as an
example. This section further clarifies its properties.
3.4.1. Identifier
The 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 an integer and non-negative. 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 between
the source endpoint and the destination endpoint. The hop count is a
basic measurement of distance in a network and can be exposed as
Router Hops, in direct relation to the routing protocols originating
this information.
Use: This metric could be used as a cost metric constraint attribute
used either together with cost metric attribute 'routingcost' or on
its own or as a returned cost metric in the response.
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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",
"ipv6:2000::1:2345:6789:abcd"
]
}
}
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,
"ipv6:2000::1:2345:6789:abcd" : 2,
}
}
}
3.4.4. Measurement Considerations and Parameters
The hop count can be calculated based on the number of routers from
the source endpoint through which data must pass to reach the
destination endpoint. This count can be measured at the source
endpoint by traceroute.
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Upon need, the traceroute can use UDP probe message or other
implementations that use ICMP and TCP to discover the hop counts
along the path from source endpoint to destination endpoint.
3.5. Cost Metric: Packet Loss
3.5.1. Identifier
The identifier for this performance metric is "pktloss".
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 loss.
3.5.3. Intended Semantics and Use
Intended Semantics: To specify spatial and temporal aggregated packet
loss 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).
Use: This metric could be used as a cost metric constraint attribute
used either together with cost metric attribute 'routingcost' or on
its own or as a returned cost metric in the response.
Example 5: pktloss 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" : "pktloss"},
"endpoints" : {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2000::1:2345:6789:abcd"
]
}
}
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HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta": {
"cost type": {
"cost-mode": "numerical",
"cost-metric":"pktloss"}
}
},
"endpoint-cost-map": {
"ipv4:192.0.2.2": {
"ipv4:192.0.2.89" : 0,
"ipv4:198.51.100.34": 0,
"ipv6:2000::1:2345:6789:abcd" : 0,
}
}
}
3.5.4. Measurement Considerations and Parameters
See Section 4 of [I-D.ietf-ippm-initial-registry] for measurement
considerations and parameters which may be specified in "parameters".
Note that the "parameters" field is an optional field providing non-
normative information.
3.6. Cost Metric: Throughput
3.6.1. Identifier
The identifier for this performance metric is "throughput".
3.6.2. 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 Mbps.
3.6.3. Intended Semantics and Use
Intended Semantics: To specify spatial and temporal throughput 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).
Use: This metric could be used as a cost metric constraint attribute
used either together with cost metric attribute 'routingcost' or on
its own or as a returned cost metric in the response.
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Example 5: throughtput 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" : "throughput"},
"endpoints" : {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2000::1:2345:6789:abcd"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta": {
"cost type": {
"cost-mode": "numerical",
"cost-metric":"throughput"
}
}
"endpoint-cost-map": {
"ipv4:192.0.2.2": {
"ipv4:192.0.2.89" : 25.6,
"ipv4:198.51.100.34": 12.8,
"ipv6:2000::1:2345:6789:abcd" : 42.8,
}
}
3.6.4. Measurement Considerations and Parameters
See Section 3.3 of [RFC6349] for measurement method and parameters
which may be specified in "parameters". Note that the "parameters"
field is an optional field providing non-normative information.
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4. Traffic Engineering Performance Cost Metrics
This section introduces ALTO network performance metrics that may be
aggregated from network metrics measured on links and specified in
other documents. In particular, the bandwidth related metrics
specified in this section are only available through link level
measurements. For some of these metrics, the ALTO Server may further
expose aggregated values while specifying the aggregation laws.
4.1. Cost Metric: Link Maximum Reservable Bandwidth
4.1.1. Identifier
The identifier for this performance metric is "maxresbw".
4.1.2. Value Representation
The metric value type is a single 'JSONNumber' type value that is
non-negative. The unit of measurement is Mbps.
4.1.3. Intended Semantics and Use
Intended Semantics: To specify spatial and temporal maximum
reservable bandwidth over the specified source and destination. The
value is corresponding to the maximum bandwidth that can be reserved
(motivated from RFC 3630 Sec. 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 as a cost metric constraint attribute
used either together with cost metric attribute 'routingcost' or on
its own or as a returned cost metric in the response.
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Example 6: maxresbw 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": "maxresbw"},
"endpoints": {
"srcs": [ "ipv4 : 192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2000::1:2345:6789:abcd"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta": {
"cost-type": {
"cost-mode": "numerical",
"cost-metric": "maxresbw"
}
},
" endpoint-cost-map": {
"ipv4:192.0.2.2" {
"ipv4:192.0.2.89" : 0,
"ipv4:198.51.100.34": 2000,
"ipv6:2000::1:2345:6789:abcd": 5000,
}
}
}
4.1.4. Measurement Considerations and Parameters
Method of Measurement or Calculation:
Maximum Reservable Bandwidth is the bandwidth measured between two
directly connected IS-IS neighbors or OSPF neighbors. See
Section 3.5 of [RFC5305] for Measurement Method.
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Measurement Point(s) with Potential Measurement Domain:
See Section 4.1 this document for discussions.
Measurement Timing:
See Section 3.5 of [RFC5305] and Section 5 of [RFC7810] for
Measurement Timing.
4.2. Cost Metric: Link Residue Bandwidth
4.2.1. Identifier
The identifier for this performance metric is "residuebw".
4.2.2. Value Representation
The metric value type is a single 'JSONNumber' type value that is
non-negative. The unit of measurement is Mbps.
4.2.3. Intended Semantics and Use
Intended Semantics: To specify spatial and temporal residual
bandwidth over the specified source and destination. The value is
calculated by subtracting tunnel reservations from Maximum Bandwidth
(motivated from [RFC7810], 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 as a cost metric constraint attribute
used either together with cost metric attribute 'routingcost' or on
its own or as a returned cost metric in the response.
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Example 7: residuebw 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": "residuebw"},
"endpoints": {
"srcs": [ "ipv4 : 192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv6:2000::1:2345:6789:abcd"
]
}
}
HTTP/1.1 200 OK
Content-Length: TBA
Content-Type: application/alto-endpointcost+json
{
"meta": {
"cost-type" {
"cost-mode": "numerical",
"cost-metric": "residuebw"
}
},
"endpoint-cost-map" {
"ipv4:192.0.2.2" {
"ipv4:192.0.2.89" : 0,
"ipv4:198.51.100.34": 2000,
"ipv6:2000::1:2345:6789:abcd": 5000,
}
}
}
4.2.4. Measurement Considerations and Parameters
Method of Measurement or Calculation:
Residue Bandwidth is the Unidirectional Residue bandwidth measured
between two directly connected IS-IS neighbors or OSPF neighbors.
See Section 4.5 of [RFC7810] for Measurement Method.
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Measurement Point(s) with Potential Measurement Domain:
See Section 4.1 of this document.
Measurement Timing:
See Section 5 of [RFC7810] for Measurement Timing.
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 [RFC7971]. In particular, the cost
metrics defined in this document can be computed using routing
systems as the data sources. Mechanisms defined in [RFC2681],
[RFC3393], [RFC7679], [RFC7680], [RFC3630], [RFC3784], [RFC7471],
[RFC7810], [RFC7752] and [I-D.ietf-idr-te-pm-bgp] that allow an ALTO
Server to retrieve and derive the necessary information to compute
the metrics that we describe in this document.
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5.2. 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 which has "cost-source" being "sla", but the
backward client will ignore this field and consider the metric
estimation.
To address this issue, the only defined "routingcost" metric can be
ONLY "estimation".
5.3. 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.
5.3.1. 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
may provide the client with the validity period of the exposed metric
values.
5.3.2. Availability Considerations
Applications value information relating to bandwidth availability
whereas bandwidth related metrics can often be only measured 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
and having different levels of endpoint granularity, e.g., link
endpoints or session endpoints. The metric specifications may also
expose the utilized aggregation laws.
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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 Client. Numerical
TE performance information will most likely be distributed by ALTO
Servers to 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".
+------------+--------------------+
| Identifier | Intended Semantics |
+------------+--------------------+
| owdelay | See Section 2.1 |
| rtt | See Section 2.2 |
| pdv | See Section 2.3 |
| hopcount | See Section 2.4 |
| pktloss | See Section 2.5 |
| throughput | See Section 2.6 |
| maxresbw | See Section 3.1 |
| residuebw | See Section 3.2 |
+------------+--------------------+
This document requests the creation of the "ALTO Cost Source
Registry" with the following currently defined values:
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+------------+---------------------------+
| Identifier | Intended Semantics |
+------------+---------------------------+
| estimation | Values by estimation |
| nominal | Values in nominal cases |
| sla | Values reflecting service |
| | level agreement |
+------------+---------------------------+
8. Acknowledgments
The authors of this document would also like to thank Brian Trammell,
Haizhou Du, Kai Gao, Lili Liu, Li, Geng, Danny Alex Lachos Perez for
the reviews and comments. Young Lee is an author of an earlier
version of the document.
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>.
[RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Delay Metric for IPPM", RFC 2679, DOI 10.17487/RFC2679,
September 1999, <https://www.rfc-editor.org/info/rfc2679>.
[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>.
[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>.
[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>.
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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>.
[RFC7810] Previdi, S., Ed., Giacalone, S., Ward, D., Drake, J., and
Q. Wu, "IS-IS Traffic Engineering (TE) Metric Extensions",
RFC 7810, DOI 10.17487/RFC7810, May 2016,
<https://www.rfc-editor.org/info/rfc7810>.
[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>.
9.2. Informative References
[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>.
[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>.
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
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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
Luis Miguel Contreras Murillo
Telefonica
Email: luismiguel.contrerasmurillo@telefonica.com
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