ALTO Performance Cost Metrics
draft-ietf-alto-performance-metrics-07
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 , Young Lee , Dhruv Dhody , Sabine Randriamasy | ||
| Last updated | 2019-07-08 | ||
| Replaces | draft-wu-alto-te-metrics | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
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draft-ietf-alto-performance-metrics-07
ALTO Working Group Q. Wu
Internet-Draft Huawei
Intended status: Standards Track Y. Yang
Expires: January 9, 2020 Yale University
Y. Lee
D. Dhody
Huawei
S. Randriamasy
Nokia Bell Labs
July 08, 2019
ALTO Performance Cost Metrics
draft-ietf-alto-performance-metrics-07
Abstract
Cost metric is a basic concept in Application-Layer Traffic
Optimization (ALTO), and is used in basic services including both the
cost map service and the endpoint cost service.
Different applications may use different cost metrics, but the ALTO
base protocol documents only one single cost metric, i.e., the
generic "routingcost" metric; see Sec. 14.2 of ALTO base
specification [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. These metrics can be derived and
aggregated 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. Additional cost metrics may
be documented in other documents.
Requirements Language The key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" in this document are to be interpreted as described in
RFC 2119 [RFC2119].
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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-
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 January 9, 2020.
Copyright Notice
Copyright (c) 2019 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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Network Performance Cost Metrics . . . . . . . . . . . . . . 5
2.1. Cost Metric: One Way Delay (owdelay) . . . . . . . . . . 5
2.1.1. Intended Semantics . . . . . . . . . . . . . . . . . 6
2.1.2. Use and Example . . . . . . . . . . . . . . . . . . . 6
2.1.3. Measurement Considerations . . . . . . . . . . . . . 7
2.2. Cost Metric: RoundTrip Time (rtt) . . . . . . . . . . . . 7
2.2.1. Intended Semantics . . . . . . . . . . . . . . . . . 8
2.2.2. Use and Example . . . . . . . . . . . . . . . . . . . 8
2.2.3. Measurement Considerations . . . . . . . . . . . . . 9
2.3. Cost Metric: Packet Delay Variation (pdv) . . . . . . . . 9
2.3.1. Intended Semantics . . . . . . . . . . . . . . . . . 10
2.3.2. Use and Example . . . . . . . . . . . . . . . . . . . 10
2.3.3. Measurement Considerations . . . . . . . . . . . . . 11
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2.4. Cost Metric: Hop Count . . . . . . . . . . . . . . . . . 12
2.4.1. Intended Semantics . . . . . . . . . . . . . . . . . 12
2.4.2. Use and Example . . . . . . . . . . . . . . . . . . . 13
2.4.3. Measurement Considerations . . . . . . . . . . . . . 14
2.5. Cost Metric: Packet Loss . . . . . . . . . . . . . . . . 14
2.5.1. Intended Semantics . . . . . . . . . . . . . . . . . 14
2.5.2. Use and Example . . . . . . . . . . . . . . . . . . . 15
2.5.3. Measurement Considerations . . . . . . . . . . . . . 16
2.6. Cost Metric: Throughput . . . . . . . . . . . . . . . . . 16
2.6.1. Intended Semantics . . . . . . . . . . . . . . . . . 17
2.6.2. Use and Example . . . . . . . . . . . . . . . . . . . 17
2.6.3. Measurement Considerations . . . . . . . . . . . . . 18
3. Traffic Engineering Performance Cost Metrics . . . . . . . . 18
3.1. Cost Metric: Link Maximum Reservable Bandwidth . . . . . 19
3.1.1. Intended Semantics . . . . . . . . . . . . . . . . . 19
3.1.2. Use and Example . . . . . . . . . . . . . . . . . . . 19
3.1.3. Measurement Considerations . . . . . . . . . . . . . 20
3.2. Cost Metric: Link Residue Bandwidth . . . . . . . . . . . 21
3.2.1. Intended Semantics . . . . . . . . . . . . . . . . . 21
3.2.2. Use and Example . . . . . . . . . . . . . . . . . . . 21
3.2.3. Measurement Considerations . . . . . . . . . . . . . 22
4. Operational Considerations . . . . . . . . . . . . . . . . . 23
4.1. Data Source Considerations . . . . . . . . . . . . . . . 23
4.2. Computation Considerations . . . . . . . . . . . . . . . 24
4.2.1. Configuration Parameters Considerations . . . . . . . 24
4.2.2. Availability Considerations . . . . . . . . . . . . . 24
5. Security Considerations . . . . . . . . . . . . . . . . . . . 24
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.1. Normative References . . . . . . . . . . . . . . . . . . 25
8.2. Informative References . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
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 more delay-
sensitive application may want to use latency related metrics, and a
more bandwidth-sensitive application may want to use bandwidth
related metrics. The ALTO base protocol [RFC7285], however, has
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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
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 | [RFC2679] Section 3.6 |
| Round Trip Delay | Section 2.2 | [RFC2681] Section 2.6 |
| Packet Delay Variation | Section 2.3 | [RFC3393] Section 2.6 |
| Hop Count | Section 2.4 | [RFC7285] |
| Packet Loss | Section 2.5 | [RFC7680] Section 2.6 |
| Throughput | Section 2.6 | [RFC6349] Section 3.3 |
| Max Reservable Bandwidth | Section 3.1 | [RFC5305] Section 3.5 |
| Residue Bandwidth | Section 3.2 | [RFC7810] Section 4.5 |
+------------+---------------------------------------------------+
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. Some of
these metrics are already specified by standards such as IPPM; some
are ISP dependent such as those registered in ISIS or OSPF-TE. This
document will refer to the relevant specifications.
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 them need to be exposed to
applications. 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).
The cost metrics defined in this document can be retrieved and
aggregated from routing protocols or other traffic measurement
management tools, with corresponding operational issues. A potential
architecture on computing these metrics is shown in Figure 1 below.
In Section 4, we discuss in more detail the operations issues and how
to address them.
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+--------+ +--------+ +--------+
| Client | | Client | | Client |
+----^---+ +---^----+ +---^----+
| | |
+-----------|-----------+
NBI |ALTO protocol
|
|
+--+-----+ retrieval +---------+
| ALTO |<----------------| Routing |
| Server | and aggregation| |
| |<-------------+ | Protocol|
+--------+ | +---------+
|
| +---------+
| |Management
---| |
| Tool |
+---------+
Figure 1. Potential framework to compute performance cost metrics
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 feel the
exposed information does not preserve their performance level or even
degrades it. We discuss security considerations in more details in
Section 5.
Following the ALTO base protocol, this document uses JSON to specify
the value type of each defined metric. See [RFC4627] for JSON data
type specification.
2. Network Performance Cost Metrics
This section introduces generic ALTO network performance metrics such
as one way delay,round trip delay,hop count,packet loss,throughput
derived and aggregated from routing protocols or from end to end
traffic management tools.
2.1. Cost Metric: One Way Delay (owdelay)
Metric name:
One Way Delay
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Metric Identifier:
owdelay
2.1.1. Intended Semantics
Metric Description: 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).
Metric Representation: The metric value type is a single 'JSONNumber'
type value containing a non-negative integer component that may be
followed by an exponent part. See section 8.4.3 of [I-D.ietf-ippm-
initial-registry] for metric unit. The unit is expressed in
milliseconds in this document.
2.1.2. Use and Example
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 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"
]
}
}
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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" : "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,
}
}
}
2.1.3. Measurement Considerations
Method of Measurement or Calculation:
See section 8.3 of [I-D.ietf-ippm-initial-registry] for potential
measurement method.
Measurement Point(s) with Potential Measurement Domain:
See Section 4.1, Data sources for potential data sources.
Measurement Timing:
See section 8.3.5 of [I-D.ietf-ippm-initial-registry] for
potential measurement timing considerations.
2.2. Cost Metric: RoundTrip Time (rtt)
Metric name:
Round Trip Time
Metric Identifier:
rtt
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2.2.1. Intended Semantics
Metric Description: 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).
Metric Representation: The metric value type is a single 'JSONNumber'
type value containing a non-negative integer component that may be
followed by an exponent part. See section 4.4.3 of [I-D.ietf-ippm-
initial-registry] for Measurement Unit. The unit is expressed in
milliseconds in this document.
2.2.2. Use and Example
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 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"
]
}
}
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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" : "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,
}
}
}
2.2.3. Measurement Considerations
Method of Measurement or Calculation:
See section 4.3 of [I-D.ietf-ippm-initial-registry] for potential
measurement method.
Measurement Point(s) with Potential Measurement Domain:
See section 4.1, Data sources.
Measurement Timing:
See section 4.3.5 of [I-D.ietf-ippm-initial-registry] for
Measurement Timing.
2.3. Cost Metric: Packet Delay Variation (pdv)
Metric name:
Packet Delay Variation
Metric Identifier:
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pdv
2.3.1. Intended Semantics
Metric Description: 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).
Metric Representation: The metric value type is a single 'JSONNumber'
type value containing a non-negative integer component that may be
followed by an exponent part. See section 5.4.4 of [I-D.ietf-ippm-
initial-registry] for Measurement Unit. The unit is expressed in
milliseconds in this document.
2.3.2. Use and Example
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
}
}
}
2.3.3. Measurement Considerations
Method of Measurement or Calculation:
See Section 5.3 of [I-D.ietf-ippm-initial-registry] for potential
measurement method.
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Measurement Point(s) with Potential Measurement Domain:
See Section 4.1, Data sources for potential data sources.
Measurement Timing:
See Section 5.3.5 of [I-D.ietf-ippm-initial-registry] for
Measurement Timing.
2.4. Cost Metric: Hop Count
The metric hopcount is mentioned in [RFC7285] Section 9.2.3 as an
example. This section further clarifies its properties.
Metric name:
Hop count
Metric Identifier:
hopcount
2.4.1. Intended Semantics
Metric Description:
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.
Metric Representation:
The metric value type is a single 'JSONNumber' type value
containing a non-negative integer component. The unit is integer
number.
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2.4.2. Use and Example
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 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,
}
}
}
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2.4.3. Measurement Considerations
Method of Measurement or Calculation:
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.
Measurement Point(s) with Potential Measurement Domain:
The hop count can be measured at the source endpoint by
traceroute.
Measurement Timing:
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.
2.5. Cost Metric: Packet Loss
Metric name:
Packet loss
Metric Identifier:
pktloss
2.5.1. Intended Semantics
Metric Description:
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).
Metric Representation:
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The metric value type is a single 'JSONNumber' type value which be
be non-negative integer. The unit is percentile.
2.5.2. Use and Example
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,
}
}
}
2.5.3. Measurement Considerations
Method of Measurement or Calculation:
See Section 2.6 of [RFC7680] for Measurement Method.
Measurement Point(s) with Potential Measurement Domain:
See Section 4.1 this document, Data sources.
Measurement Timing:
See Section 2 and Section 3 of [RFC7680] for Measurement Timing.
2.6. Cost Metric: Throughput
Metric name:
Throughput
Metric Identifier:
throughput
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2.6.1. Intended Semantics
Metric Description:
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).
Metric Representation:
The unit is Mbps.
2.6.2. Use and Example
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: 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"
]
}
}
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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":"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,
}
}
2.6.3. Measurement Considerations
Method of Measurement or Calculation:
See Section 3.3 of [RFC6349] for Measurement Method.
Measurement Point(s) with Potential Measurement Domain:
See Section 4.1 of this document.
Measurement Timing:
Similar to RTT. See Section 4.3.5 of [I-D.ietf-ippm-initial-
registry] for Measurement Timing.
3. 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.
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3.1. Cost Metric: Link Maximum Reservable Bandwidth
Metric name:
Maximum Reservable Bandwidth
Metric Identifier:
maxresbw
3.1.1. Intended Semantics
Metric Description:
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).
Metric Representation:
The metric value type is a single 'JSONNumber' type value that is
non-negative. The unit of measurement is mbps.
3.1.2. Use and Example
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,
}
}
}
3.1.3. Measurement Considerations
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.
3.2. Cost Metric: Link Residue Bandwidth
Metric name:
Residue Bandwidth
Metric Identifier:
residuebw
3.2.1. Intended Semantics
Metric Description:
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).
Metric Representation:
The metric value type is a single 'JSONNumber' type value that is
non-negative. The unit of measurement is mbps.
3.2.2. Use and Example
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,
}
}
}
3.2.3. Measurement Considerations
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.
4. Operational Considerations
It can be non-trivial for an ALTO server to derive the metrics.
Also, the exact infrastructure and algorithms can vary from different
networks, and are outside the scope of this document. However, since
they present challenges, we discuss these common challenges.
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.
4.1. Data Source Considerations
An ALTO server needs data sources to compute the cost metrics
described in this document. This document does not define the exact
data sources. 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.
One challenge lies in the data sources originating the ALTO metric
values. The very important purpose of ALTO is to guide application
traffic with provider network centric information that may be exposed
to ALTO Clients in the form of network performance metric values.
Not all of these metrics have values produced by standardized
measurement methods or routing protocols. Some of them involve
provider-centric policy considerations. Some of them may describe
wireless or cellular networks. To reliably guide users and
applications while preserving provider privacy, ALTO performance
metric values may also add abstraction to measurements or provide
unitless performance scores.
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4.2. 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.
4.2.1. 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.
4.2.2. 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.
5. 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.
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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.
6. 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 |
+------------+--------------------+
7. 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.
8. References
8.1. Normative References
[I-D.ietf-idr-te-pm-bgp]
Ginsberg, L., Previdi, S., Wu, Q., Tantsura, J., and C.
Filsfils, "BGP-LS Advertisement of IGP Traffic Engineering
Performance Metric Extensions", draft-ietf-idr-te-pm-
bgp-18 (work in progress), December 2018.
[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-11 (work in progress), March
2019.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.
[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>.
[RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, DOI
10.17487/RFC4627, July 2006, <https://www.rfc-
editor.org/info/rfc4627>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/
RFC5234, January 2008, <https://www.rfc-editor.org/info/
rfc5234>.
[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>.
[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>.
[RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S.
Previdi, "OSPF Traffic Engineering (TE) Metric
Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015,
<https://www.rfc-editor.org/info/rfc7471>.
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[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>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016, <https://www.rfc-
editor.org/info/rfc7752>.
[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>.
8.2. Informative References
[RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric
Development", RFC 6390, July 2011.
[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
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Y. Richard Yang
Yale University
51 Prospect St
New Haven, CT 06520
USA
Email: yry@cs.yale.edu
Young Lee
Huawei
1700 Alma Drive, Suite 500
Plano, TX 75075
USA
Email: leeyoung@huawei.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
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