Network Working Group S. Randriamasy
Internet-Draft Nokia Bell Labs
Intended status: Standards Track R. Yang
Expires: March 25, 2019 Yale University
Q. Wu
Huawei
L. Deng
China Mobile
N. Schwan
Thales Deutschland
September 21, 2018
ALTO Cost Calendar
draft-ietf-alto-cost-calendar-08
Abstract
This document is an extension to the base ALTO protocol [RFC7285].
It extends the ALTO cost information service such that applications
decide not only 'where' to connect, but also 'when'. This is useful
for applications that need to perform bulk data transfer and would
like to schedule these transfers during an off-peak hour, for
example. This extension introduces ALTO Cost Calendars, with which
an ALTO Server exposes ALTO cost values in JSON arrays where each
value corresponds to a given time interval. The time intervals as
well as other Calendar attributes are specified in the Information
Resources Directory and ALTO Server responses.
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].
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 https://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
Randriamasy, et al. Expires March 25, 2019 [Page 1]
Internet-Draft ALTO Cost Calendar September 2018
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 March 25, 2019.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/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. Overview of ALTO Cost Calendars . . . . . . . . . . . . . . . 4
2.1. ALTO Cost Calendar information features . . . . . . . . . 5
2.2. ALTO Calendar design characteristics . . . . . . . . . . 5
2.2.1. ALTO Cost Calendar for all cost modes . . . . . . . . 6
2.2.2. Compatibility with legacy ALTO Clients . . . . . . . 6
3. ALTO Calendar specification: IRD extensions . . . . . . . . . 7
3.1. Calendar attributes in the IRD resources capabilities . . 7
3.2. Calendars in a delegate IRD . . . . . . . . . . . . . . . 9
3.3. Example IRD with ALTO Cost Calendars . . . . . . . . . . 9
4. ALTO Calendar specification: Service Information Resources . 13
4.1. Calendar extensions for filtered cost maps . . . . . . . 13
4.1.1. Calendar extensions in Filtered Cost Map requests . . 13
4.1.2. Calendar extensions in Filtered Cost Map responses . 14
4.1.3. Use case and example: FCM with a bandwidth Calendar . 16
4.2. Calendar extensions in the Endpoint Cost Service . . . . 18
4.2.1. Calendar specific input in Endpoint Cost requests . 18
4.2.2. Calendar attributes in the Endpoint Cost response . . 18
4.2.3. Use case and example: ECS with a routingcost Calendar 19
4.2.4. Use case and example: ECS with a multi-cost calendar
for routingcost and owdelay . . . . . . . . . . . . . 22
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
6. Security Considerations . . . . . . . . . . . . . . . . . . . 24
7. Operational Considerations . . . . . . . . . . . . . . . . . 25
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
Randriamasy, et al. Expires March 25, 2019 [Page 2]
Internet-Draft ALTO Cost Calendar September 2018
9.1. Normative References . . . . . . . . . . . . . . . . . . 25
9.2. Informative References . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction
The ALTO protocol provides guidance to overlay applications needing
to select one or several hosts from a set of candidates able to
provide a desired resource. This guidance is based on parameters
that affect performance and efficiency of the data transmission
between the hosts such as the topological distance. The goal of ALTO
is to improve the Quality of Experience (QoE) in the application
while optimizing resource usage in the underlying network
infrastructure.
The ALTO protocol in [RFC7285] specifies a network map which defines
groupings of endpoints in provider-defined network regions (called
PIDs). The Cost Map Service, Endpoint Cost Service (ECS) and
Endpoint Ranking Service then provide ISP-defined costs and rankings
for connections among the specified endpoints and PIDs and thus
incentives for application clients to connect to ISP preferred
locations, e.g. to reduce their costs. ALTO intentionally avoids
provisioning realtime information as explained in the ALTO Problem
Statement [RFC5693] and ALTO Requirements [RFC5693]. Thus the
current Cost Map and Endpoint Cost Service are providing, for a given
Cost Type, exactly one path cost value. Applications have to query
one of these two services to retrieve the currently valid cost
values. They therefore need to plan their ALTO information requests
according to their own estimation of the frequency of cost value
change.
With [RFC7285], an ALTO client should interpret the returned costs as
those at the query moment. However, Network costs can fluctuate,
e.g. due to diurnal patterns of traffic demand or planned events such
as network maintenance, holidays or highly publicized events.
Providing network costs for only the current time thus may not be
sufficient, in particular for applications that can schedule their
traffic in a span of time, for example by deferring backups or other
background traffic to off-peak hours.
In case the ALTO Cost value changes are predictable over a certain
period of time and the application does not require immediate data
transfer, it can save time to get the whole set of cost values over
this period in one single ALTO response. Using this set to schedule
data transfers allows optimizing the network resources usage and QoE.
ALTO Clients and Servers can also minimize their workload by reducing
and accordingly scheduling their data exchanges.
Randriamasy, et al. Expires March 25, 2019 [Page 3]
Internet-Draft ALTO Cost Calendar September 2018
This document extends [RFC7285] to allow an ALTO server to provide
network costs for a given duration of time. A sequence of network
costs across a time span for a given pair of network locations is
named an "ALTO Cost Calendar". The Filtered Cost Map Service and
Endpoint Cost Service are extended to provide Cost Calendars. In
addition to this functional ALTO enhancement, we expect to further
save network and storage resources by gathering multiple Cost Values
for one Cost Type into one single ALTO Server response.
In this draft an "ALTO Cost Calendar" is specified by information
resources capabilities that are applicable to time-sensitive ALTO
metrics. An ALTO Cost Calendar exposes ALTO Cost Values in JSON
arrays where each value corresponds to a given time interval. The
time intervals as well as other Calendar attributes are specified in
the IRD and in the Server response to allow the ALTO Client to
interpret the received ALTO values. Last, the proposed extensions
for ALTO Calendars are applicable to any Cost Mode and they ensure
backwards compatibility with legacy ALTO clients.
In the rest of this document, Section 2 provides the design
characteristics. Sections 3 and 4 define the formal specifications
for the IRD and the information resources. IANA, security and
operational considerations are addressed respectively in sections
Section 5, Section 6 and Section 7.
2. Overview of ALTO Cost Calendars
An ALTO Cost calendar provided by the ALTO Server provides 2
information items:
o an array of values for a given metric, where each value
corresponds to a time interval, where the value array can
sometimes be a cyclic pattern that repeats a certain number of
times.
o attributes describing the time scope of the calendar such as the
size and number of the intervals and the date of the starting
point of the calendar, allowing an ALTO Client to properly
interpret the values.
An ALTO Cost Calendar can be used like a "time table" to figure out
the best time to schedule data transfers and also to proactively
manage application traffic given predictable events such as flash
crowds, traffic intensive holidays and network maintenance. It may
be viewed as a synthetic abstraction of real measurements that can be
historic or be a prediction for upcoming time periods.
Randriamasy, et al. Expires March 25, 2019 [Page 4]
Internet-Draft ALTO Cost Calendar September 2018
Most likely, the ALTO Cost Calendar would be used for the Endpoint
Cost Service, assuming that a limited set of feasible Endpoints for a
non-real time application is already identified, that they do not
need to be accessed immediately and that their access can be
scheduled within a given time period. The Filtered Cost Map Service
is also applicable as long as the size of the Map allows it.
2.1. ALTO Cost Calendar information features
The Calendar attributes are provided in the Information Resources
Directory (IRD) and in ALTO Server responses. The IRD announces
attributes with dateless values in its information resources
capabilities, where as attributes with time dependent values are
provided in the "meta" of Server responses. The ALTO Cost Calendar
attributes provide the following information:
o attributes to interpret the time scope of the Calendar value
array:
* generic time zone,
* applicable time interval size for each calendar value:
combining a number and a time unit to reflect for example: 1
hour, 2 minutes, 10 seconds, 1 week, 1 month,
* duration of the Calendar: e.g. the number of intervals provided
in the calendar.
o "calendar-start-date": specifying when the calendar starts, that
is to which date the first value of the cost calendar is
applicable.
o "repeated": an optional attribute indicating for how many
iterations the provided calendar will have the same values. The
server may use it to allow the client to schedule its next request
and thus save its own workload by avoiding to process useless
requests.
2.2. ALTO Calendar design characteristics
To realize an ALTO Calendar, this document extends: the IRD, the ALTO
requests and responses for Cost Calendars.
This extension is designed to be light and ensure backwards
compatibility with base protocol ALTO Clients and with other
extensions. As recommended, it relies on section 8.3.7 "Parsing of
Unknown Fields" of [RFC7285] that writes: "Extensions may include
additional fields within JSON objects defined in this document. ALTO
Randriamasy, et al. Expires March 25, 2019 [Page 5]
Internet-Draft ALTO Cost Calendar September 2018
implementations MUST ignore unknown fields when processing ALTO
messages."
The calendar-specific capabilities are integrated in the information
resources of the IRD and in the "meta" member of ALTO responses to
Cost Calendars requests. A calendar and its capabilities are
associated with a given information resource and within this
information resource with a given cost type. This design has several
advantages:
o it does not introduce a new mode,
o it does not introduce new media types,
o it allows an ALTO Server to offer calendar capabilities on a cost
type, with attributes values adapted to each information resource.
The Applicable Calendared information resources are:
o the Filtered Cost Map,
o the Endpoint Cost Map.
The ALTO Server can choose in which frequency it provides cost
Calendars to ALTO Clients. It may either provide calendar updates
starting at the request date, or carefully schedule its updates so as
to take profit from a potential repetition/periodicity of calendar
values.
2.2.1. ALTO Cost Calendar for all cost modes
ALTO Calendars are well-suited for values encoded in the "numerical"
mode. Actually, Calendars can also represent metrics in other modes
considered as compatible with time-varying values. For example,
types of Cost values such as JSONBool can also be expressed as
calendars, as their value may be 'true' or 'false' depending on given
time periods or likewise, values represented by strings, such as
"medium", "high", "low", "blue", "open".
Note also that a Calendar is suitable as well for time-varying
metrics provided in the "ordinal" mode, if these values are time-
varying and their update is carefully managed by the ALTO Server.
2.2.2. Compatibility with legacy ALTO Clients
The ALTO protocol extensions for Cost Calendars have been defined so
as to ensure that Calendar capable ALTO Servers can provide legacy
ALTO Clients with legacy information resources as well. That is a
Randriamasy, et al. Expires March 25, 2019 [Page 6]
Internet-Draft ALTO Cost Calendar September 2018
legacy ALTO Client can request resources and receive responses as
specified in [RFC7285].
A Calendar-aware ALTO Server MUST implement the base protocol
specified in [RFC7285].
When a metric is available as a calendar, it MUST be available as a
single value as well.
For compatibility with legacy ALTO Clients specified in [RFC7285],
calendared information resources are not applicable for full cost
maps for the following reason: a legacy ALTO client would receive a
calendared cost map via an HTTP 'GET' command. As specified in
section 8.3.7 of [RFC7285], it will ignore the Calendar Attributes
indicated in the "meta" of the responses. Therefore, lacking
information on calendar attributes, it will not be able to correctly
interpret and process the values of the received array of calendar
cost values.
Therefore, calendared information resources MUST be requested via the
Filtered Cost Map Service or the Endpoint Cost Service, using a POST
method.
3. ALTO Calendar specification: IRD extensions
The Calendar attributes in the IRD information resources capabilities
carry constant dateless values. A calendar is associated with an
information resource rather than a cost type. For example, a Server
can provide a "routingcost" calendar for the Filtered Cost Map
Service at a granularity of one day and a "routingcost" calendar for
the Endpoint Cost service at a finer granularity but for a limited
number of endpoints.
3.1. Calendar attributes in the IRD resources capabilities
When for an applicable resource, an ALTO Server provides a Cost
Calendar for a given Cost Type, it MUST indicate this in the IRD
capabilities of this resource, by an object of type
'CalendarAttributes', associated with this Cost Type and specified
below.
The capabilities of a Calendar-aware information resource entry have
a member named "calendar-attributes" which is an array of objects of
type CalendarAttributes. It is necessary to use an array because of
resources such as Filtered Cost Map and Endpoint Cost Map, for which
the member "cost-type-names" is an array of 1 or more values.
Randriamasy, et al. Expires March 25, 2019 [Page 7]
Internet-Draft ALTO Cost Calendar September 2018
A member "calendar-attributes" MUST appear only once for each
applicable cost type name of a resource entry. If "calendar-
attributes" are specified several times for a same "cost-type-name"
in the capabilities of a resource entry, the ALTO client SHOULD
ignore any additional occurrence of "calendar-attributes", for this
cost type name.
An ALTO Client should assume that the time interval size specified in
the IRD is the smallest possible one that the ALTO Server can
provide. The Client can aggregate cost values on its own if it needs
a larger granularity.
CalendarAttributes calendar-attributes <1..*>;
object{
JSONString cost-type-names <1..*>;
JSONString time-interval-size;
JSONNumber number-of-intervals;
} CalendarAttributes;
o "cost-type-names":
* An array of one or more elements indicating the cost-type-names
in the IRD entry to which the capabilities apply.
o "time-interval-size":
* is the duration of an ALTO calendar time interval. A "time-
interval-size" value contains 2 entities separated by exactly
one whitespace: a JSONNumber and a string representing a time
unit and taking values in {second, minute, hour, day, week,
month, year}. Example values are: "5 minute" , "2 hour",
meaning that each calendar value applies on a time interval
that lasts respectively 5 minutes and 2 hours.
o "number-of-intervals":
* the integer number of values of the cost calendar array, at
least equal to 1.
- Attribute "cost-type-name" , if used, provides a better readability
to the calendar attributes specified in the IRD and avoids confusion
with calendar attributes of other cost-types.
- Multiplying Attributes 'time-interval-size' and 'number-of-
intervals' provides the duration of the provided calendar. For
example an ALTO Server may provide a calendar for ALTO values
changing every 'time-interval-size' equal to 5 minutes. If 'number-
Randriamasy, et al. Expires March 25, 2019 [Page 8]
Internet-Draft ALTO Cost Calendar September 2018
of-intervals' has the value 12, then the duration of the provided
calendar is "1 hour".
3.2. Calendars in a delegate IRD
One option to clarify IRD resources is that a "root" ALTO Server
implementing base protocol resources delegates "specialized"
information resources such as the ones providing Cost Calendars to
another ALTO Server running in a subdomain specified with its URI in
the "root" ALTO Server. This option is described in Section 9.2.4
"Delegation using IRDs" of [RFC7285].
This document provides an example, where a "root" ALTO Server runs in
a domain called "alto.example.com". It delegates the announcement of
Calendars capabilities to an ALTO Server running in a subdomain
called "custom.alto.example.com". The location of the "delegate
Calendar IRD" is assumed to be indicated in the "root" IRD by the
resource entry: "custom-calendared-resources".
Another advantage is that some Cost Types for some resources may be
more advantageous as Cost Calendars and it makes few sense to get
them as a single value. For example, Cost Types with predictable and
frequently changing values, calendared in short time intervals such
as a minute.
3.3. Example IRD with ALTO Cost Calendars
This section provides an example IRD with various cost metrics and
cost modes. As [RFC7285] makes it mandatory, it uses metric
"routingcost" in the "numerical" mode.
For illustrative purposes, this section introduces 3 other fictitious
example metrics and modes that should be understood as examples and
should not be used or considered as normative.
The cost type names used in the example IRD as thus as follows:
o "num-routingcost": refers to metric "routingcost" in the numerical
mode as defined in [RFC7285] and registered at the IANA.
o "num-owdelay": refers to some fictitious performance metric
"owdelay" in the "numerical" mode,to reflect the one way packet
transmission delay on a path. A related performance metric is
currently under definition in
[draft-ietf-alto-performance-metrics].
Randriamasy, et al. Expires March 25, 2019 [Page 9]
Internet-Draft ALTO Cost Calendar September 2018
o "num-throughputrating": refers to some fictitious metric
"throughputrating" in the "numerical" mode, to reflect the
provider preference in terms of end to end throughput.
o "string-servicestatus": refers to some fictitious metric
"servicestatus" in some example mode "string", to reflect the
availability, defined by the provider, of for instance path
connectivity.
The example IRD includes 2 particular URIs providing calendars:
o "http://custom.alto.example.com/calendar/costmap/filtered": a
filtered cost map in which calendar capabilities are indicated for
cost type names: "num-routingcost", "num-throughputrating" and
"string-servicestatus",
o "http://custom.alto.example.com/calendar/endpointcost/lookup": an
endpoint cost map in which calendar capabilities are indicated for
cost type names: "num-routingcost", "num-owdelay", "num-
throughputrating", "string-servicestatus".
The design of the Calendar capabilities allows that some calendars on
a cost type name are available in several information resources with
different Calendar Attributes. This is the case for calendars on
"num-routingcost", "num-throughputrating" and "string-servicestatus"
, available in both the Filtered Cost map and Endpoint Cost Service,
but with different time interval sizes for "num-throughputrating" and
"string-servicestatus".
GET /calendars-directory HTTP/1.1
Host: custom.alto.example.com
Accept: application/alto-directory+json,application/alto-error+json
---------------
HTTP/1.1 200 OK
Content-Length: 2663
Content-Type: application/alto-directory+json
{
"meta" : {
"default-alto-network-map" : "my-default-network-map",
"cost-types": {
"num-routingcost": {
"cost-mode" : "numerical",
"cost-metric" : "routingcost"
},
"num-owdelay": {
"cost-mode" : "numerical",
Randriamasy, et al. Expires March 25, 2019 [Page 10]
Internet-Draft ALTO Cost Calendar September 2018
"cost-metric": "owdelay"
},
"num-throughputrating": {
"cost-mode" : "numerical",
"cost-metric": "throughputrating",
},
"string-servicestatus": {
"cost-mode" : "string",
"cost-metric": "servicestatus",
}
}
},
"resources" : {
"filtered-cost-map-calendar" : {
"uri" :
"http://custom.alto.example.com/calendar/costmap/filtered",
"media-type" : "application/alto-costmap+json",
"accepts" : "application/alto-costmapfilter+json",
"capabilities" : {
"cost-constraints" : true,
"cost-type-names" : [ "num-routingcost",
"num-throughputrating",
"string-servicestatus" ],
"calendar-attributes" : [
{"cost-type-names" : [ "num-routingcost",
"num-throughputrating" ],
"time-interval-size" : "1 hour",
"number-of-intervals" : 24
},
{"cost-type-names" : [ "string-servicestatus" ],
"time-interval-size" : "30 minute",
"number-of-intervals" : 48
}
]
}
"uses": [ "my-default-network-map" ]
},
"endpoint-cost-calendar-map" : {
"uri" :
"http://custom.alto.example.com/calendar/endpointcost/lookup",
"media-type" : "application/alto-endpointcost+json",
"accepts" : "application/alto-endpointcostparams+json",
"capabilities" : {
"cost-constraints" : true,
"cost-type-names" : [ "num-routingcost",
"num-owdelay",
"num-throughputrating",
"string-servicestatus" ],
Randriamasy, et al. Expires March 25, 2019 [Page 11]
Internet-Draft ALTO Cost Calendar September 2018
"calendar-attributes" : [
{"cost-type-names" : [ "num-routingcost" ],
"time-interval-size" : "1 hour",
"number-of-intervals" : 24
},
{"cost-type-names" : [ "num-owdelay" ],
"time-interval-size" : "5 minute",
"number-of-intervals" : 12
},
{"cost-type-names" : [ "num-throughputrating" ],
"time-interval-size" : "1 minute",
"number-of-intervals" : 60
},
{"cost-type-names" : [ "string-servicestatus" ],
"time-interval-size" : "2 minute",
"number-of-intervals" : 30
}
]
}
}
}
}
In this example IRD, for the Filtered Cost map Service:
o the Calendar for "num-routingcost" and "num-throughputrating" is
an array of 24 values each provided on a time interval lasting 1
hour.
o the Calendar for "string-servicestatus": "is an array of 48 values
each provided on a time interval lasting 30 minutes.
For the Endpoint Cost service:
o the Calendar for "num-routingcost": is an array of 24 values each
provided on a time interval lasting 1 hour.
o the Calendar for "owdelay": is an array of 12 values each provided
on a time interval lasting 5 minutes.
o the Calendar for "num-throughputrating": is an array of 60 values
each provided on a time interval lasting 1 minute.
o the Calendar for "string-servicestatus": "is an array of 30 values
each provided on a time interval lasting 2 minutes.
Randriamasy, et al. Expires March 25, 2019 [Page 12]
Internet-Draft ALTO Cost Calendar September 2018
4. ALTO Calendar specification: Service Information Resources
This section documents the individual information resources defined
to provide the Calendared information services defined in this
document.
The reference time zone for the provided time values is GMT because
the option chosen to express the time format is the HTTP header
fields format:
Date: Tue, 15 Nov 2014 08:12:31 GMT
4.1. Calendar extensions for filtered cost maps
A legacy ALTO client requests and gets Filtered Cost Map responses as
specified in [RFC7285].
4.1.1. Calendar extensions in Filtered Cost Map requests
The input parameters of a "legacy" request for a filtered cost map,
defined by object ReqFilteredCostMap in section 11.3.2 of [RFC7285],
are augmented with one additional member.
A Calendar-aware ALTO client requesting a Calendar on a given Cost
Type for a filtered cost map resource having Calendar capabilities
MUST add the following field to its input parameters:
JSONBoolean calendared<1..*>;
This field is an array of 1 to N boolean values, where N is the
number of requested metrics. Each boolean value indicates whether or
not the ALTO Server should provide the values for this Cost Type as a
calendar. The array MUST contain exactly N boolean values, otherwise
the server returns an error.
This field SHOULD NOT be specified if no member "calendar-attributes"
is specified in this information resource.
If a value of field 'calendared' is 'true' for a cost type name for
which no calendar attributes have been specified: a Calendar-aware
Server will return a response with a single cost value as specified
in [RFC7285].
If this field is not present, it MUST be assumed to have only values
equal to 'false'.
Randriamasy, et al. Expires March 25, 2019 [Page 13]
Internet-Draft ALTO Cost Calendar September 2018
A Calendar-aware ALTO client supporting single cost type values, as
specified in [RFC7285], that aims to request a Calendar MUST provide
an array of 1 element:
"calendared" : [true];
A Calendar-aware ALTO client that is also Multi-Cost aware MUST
provide an array of N values set to 'true' or 'false', depending
whether it wants the applicable Cost Type values as a single or
calendared value.
4.1.2. Calendar extensions in Filtered Cost Map responses
The calendared costs are JSONArrays instead of JSONNumbers for the
legacy ALTO implementation. All arrays have a number of values equal
to 'number-of-intervals'.
The "meta" field of a Calendared Filtered Cost Map response MUST
include at least:
o if the ALTO Client supports cost values for one Cost Type at a
time only: the "meta" fields specified in [RFC7285] for these
information service responses:
* "dependent-vtags ",
* "cost-type" field.
o if the ALTO Client supports cost values for several Cost Types at
a time, as specified in [RFC8189] : the "meta" fields specified in
[RFC8189] for these information service responses:
* "dependent-vtags ",
* "cost-type" field with value set to '{}', for backwards
compatibility with [RFC7285].
* "multi-cost-types" field.
o If the client request does not provide member "calendared" or if
it provides it with a value equal to 'false', for all the
requested Cost Types, then the ALTO Server response is exactly as
specified in [RFC7285] and [RFC8189].
o If the value of member "calendared" is equal to 'false' for a
given requested Cost Type, the ALTO Server must return, for these
Cost Types, a single cost value as specified in [RFC7285].
Randriamasy, et al. Expires March 25, 2019 [Page 14]
Internet-Draft ALTO Cost Calendar September 2018
In addition, the "meta" field of a Calendared Filtered Cost map
response MUST include the member "calendar-response-attributes" for
the requested information resource, together with the values provided
by the ALTO Server for these attributes. This member is an array of
objects of type "CalendarResponseAttributes", defined as follows:
CalendarResponseAttributes calendar-response-attributes <1..*>;
object{
[JSONString cost-type-names <1..*>];
JSONString calendar-start-time;
JSONString time-interval-size;
JSONNumber number-of-intervals;
[JSONNumber repeated;]
} CalendarResponseAttributes;
Object CalendarResponseAttributes has the following attributes:
o "cost-type-names": member indicating the cost-type-names to which
the capabilities apply. This field MUST appear in responses to
Multi-Cost ALTO requests.
o "calendar-start-time": indicates the date at which the first value
of the calendar applies. By default, the value provided for the
"calendar-start-time" attribute SHOULD be no later than the
request date.
o "time-interval-size": as specified in section "Calendar attributes
in the IRD resources capabilities",
o "number-of-intervals": as specified in section "Calendar
attributes in the IRD resources capabilities",
o "repeated": is an optional field provided for Calendars. It is an
integer N greater or equal to '1' that indicates how many
iterations of the calendar value array starting at the date
indicated by "calendar-start-time" have the same values. The
number N includes the provided iteration.
For example: suppose the "calendar-start-time" member has value "Mon,
30 Jun 2014 at 00:00:00 GMT", the "time-interval-size" member has
value "1 hour", the "number-of-intervals" member has value "24" and
the value of member "repeated" is equal to 4. This means that the
calendar values are the same on Monday, Tuesday, Wednesday and
Thursday on a period of 24 hours starting at 00:00:00 GMT. The ALTO
Client thus may use the same calendar for the next 4 days starting at
"calendar-start-time" and will only need to request a new one for
Friday July 4th at 00:00:00 GMT.
Randriamasy, et al. Expires March 25, 2019 [Page 15]
Internet-Draft ALTO Cost Calendar September 2018
4.1.3. Use case and example: FCM with a bandwidth Calendar
An example of non-real time information that can be provisioned in a
'calendar' is the expected path throughput. While the transmission
rate can be measured in real time by end systems, the operator of a
data center is in the position of formulating preferences for given
paths, at given time periods for example to avoid traffic peaks due
to diurnal usage patterns. In this example, we assume that an ALTO
Client requests a calendar of network provider defined throughput
ratings, as specified in the IRD, to schedule its bulk data transfers
as described in the use cases.
In the example IRD, calendars for cost type name "num-
throughputrating" are available for the information resources:
"filtered-cost-calendar-map" and "endpoint-cost-calendar-map". The
ALTO Client requests a calendar for "num-throughputrating" via a POST
request for a filtered cost map.
We suppose in this example that the ALTO Client sends its request on
Tuesday July 1st 2014 at 13:15 and, to calculate the Content-Length
in the server response, that the values for metric "throughputrating"
are encoded in 2 digits.
Randriamasy, et al. Expires March 25, 2019 [Page 16]
Internet-Draft ALTO Cost Calendar September 2018
POST /calendar/costmap/filtered HTTP/1.1
Host: alto.example.com
Content-Length: 218
Content-Type: application/alto-costmapfilter+json
Accept: application/alto-costmap+json,application/alto-error+json
{
"cost-type" : {"cost-mode" : "numerical",
"cost-metric" : "throughputrating"},
"calendared" : [true],
"pids" : {
"srcs" : [ "PID1", "PID2" ],
"dsts" : [ "PID1", "PID2", "PID3" ]
}
}
HTTP/1.1 200 OK
Content-Length: 904
Content-Type: application/alto-costmap+json
{
"meta" : {
"dependent-vtags" : [
{"resource-id": "my-default-network-map",
"tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e"
}
],
"cost-type" : {"cost-mode" : "numerical",
"cost-metric" : "throughputrating"},
"calendar-response-attributes" : [
"calendar-start-time" : Tue, 1 Jul 2014 13:00:00 GMT,
"time-interval-size" : "2 hour",
"number-of-intervals" : 12
]
},
"cost-map" : {
"PID1": { "PID1": [v1,v2, ... v12],
"PID2": [v1,v2, ... v12],
"PID3": [v1,v2, ... v12] },
"PID2": { "PID1": [v1,v2, ... v12],
"PID2": [v1,v2, ... v12],
"PID3": [v1,v2, ... v12] }
}
}
Randriamasy, et al. Expires March 25, 2019 [Page 17]
Internet-Draft ALTO Cost Calendar September 2018
4.2. Calendar extensions in the Endpoint Cost Service
This document extends the Endpoint Cost Service, as defined in
{11.5.1} of [RFC7285], by adding new input parameters and
capabilities, and by returning JSONArrays instead of JSONNumbers as
the cost values. The media type {11.5.1.1} and HTTP method
{11.5.1.2} are unchanged.
4.2.1. Calendar specific input in Endpoint Cost requests
The extensions to the requests for calendared Endpoint Cost Maps are
the same as for the Filtered Cost Map Service, specified in section
Section 4.1.1 of this draft.
The ReqEndpointCostMap object for a Calendared ECM request will have
the following format:
object {
[CostType cost-type;]
[CostType multi-cost-types<1..*>;]
[JSONBoolean calendared<1..*>;]
EndpointFilter endpoints;
} ReqEndpointCostMap;
object {
[TypedEndpointAddr srcs<0..*>;]
[TypedEndpointAddr dsts<0..*>;]
} EndpointFilter;
4.2.2. Calendar attributes in the Endpoint Cost response
The "meta" field of a Calendared Endpoint Cost response MUST include
at least:
o if the ALTO Client supports cost values for one Cost Type at a
time only: the "meta" fields specified in {11.5.1.6} of [RFC7285]
for the Endpoint Cost response:
* "cost-type" field.
o if the ALTO Client supports cost values for several Cost Types at
a time, as specified in [RFC8189] : the "meta" fields specified in
[RFC8189] for the the Endpoint Cost response:
* "cost-type" field with value set to '{}', for backwards
compatibility with [RFC7285].
Randriamasy, et al. Expires March 25, 2019 [Page 18]
Internet-Draft ALTO Cost Calendar September 2018
* "multi-cost-types" field.
If the client request does not provide member "calendared" or if it
provides it with a value equal to 'false', for all the requested Cost
Types, then the ALTO Server response is exactly as specified in
[RFC7285] and [RFC8189].
If the ALTO client provides member "calendared" in the input
parameters with a value equal to 'true' for given requested Cost
Types, the "meta" member of a Calendared Endpoint Cost response MUST
include, for these Cost Types, the same additional member "calendar-
response-attributes", as specified for the Filtered Cost Map Service.
The Server response is thus changed as follows, w.r.t [RFC7285] and
[RFC8189]:
o the "meta" member has one additional field
"CalendarResponseAttributes", as specified for the Filtered Cost
Map Service,
o the calendared costs are JSONArrays instead of JSONNumbers for the
legacy ALTO implementation. All arrays have a number of values
equal to 'number-of-intervals'.
If the value of member "calendared" is equal to 'false' for a given
requested Cost Type, the ALTO Server MUST return, for these Cost
Types, a single cost value as specified in [RFC7285].
4.2.3. Use case and example: ECS with a routingcost Calendar
Let us assume an Application Client is located in an end system with
limited resources and having an access to the network that is either
intermittent or provides an acceptable quality in limited but
predictable time periods. Therefore, it needs to both schedule its
resources greedy networking activities and its ALTO transactions.
The Application Client has the choice to trade content or resources
with a set of Endpoints and needs to decide with which one it will
connect and at what time. For instance, the Endpoints are spread in
different time-zones, or have intermittent access. In this example,
the 'routingcost' is assumed to be time-varying, with values provided
as ALTO Calendars.
The ALTO Client associated with the Application Client queries an
ALTO Calendar on 'routingcost' and will get the Calendar covering the
24 hours time period "containing" the date and time of the ALTO
client request.
Randriamasy, et al. Expires March 25, 2019 [Page 19]
Internet-Draft ALTO Cost Calendar September 2018
For Cost Type "num-routingcost", the solicited ALTO Server has
defined 3 different daily patterns each represented by a Calendar, to
cover the week of Monday June 30th at 00:00 to Sunday July 6th 23:59:
- C1 for Monday, Tuesday, Wednesday, Thursday, (week days)
- C2 for Saturday, Sunday, (week end)
- C3 for Friday (maintenance outage on July 4, 2014 from 02:00:00 GMT
to 04:00:00 GMT, or big holiday such as New Year evening).
In the following example, the ALTO Client sends its request on
Tuesday July 1st 2014 at 13:15.
To calculate the Content-Length in the server response, the
"routingcost" values are assumed to be encoded in 3 digits.
Randriamasy, et al. Expires March 25, 2019 [Page 20]
Internet-Draft ALTO Cost Calendar September 2018
POST /calendar/endpointcost/lookup HTTP/1.1
Host: alto.example.com
Content-Length: 316
Content-Type: application/alto-endpointcostparams+json
Accept: application/alto-endpointcost+json,application/alto-error+json
{
"cost-type" : {"cost-mode" : "numerical",
"cost-metric" : "routingcost"},
"calendared" : [true],
"endpoints" : {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv4:203.0.113.45",
"ipv6:2000::1:2345:6789:abcd"
]
}
}
HTTP/1.1 200 OK
Content-Length: 1007
Content-Type: application/alto-endpointcost+json
{
"meta" : {
"cost-type" : {"cost-mode" : "numerical",
"cost-metric" : "routingcost"},
"calendar-response-attributes" : [
{"calendar-start-time" : Mon, 30 Jun 2014 00:00:00 GMT,
"time-interval-size" : "1 hour",
"number-of-intervals" : 24,
"repeated": 4
}
],
}
"endpoint-cost-map" : {
"ipv4:192.0.2.2": {
"ipv4:192.0.2.89" : [v1, v2, ... v24],
"ipv4:198.51.100.34" : [v1, v2, ... v24],
"ipv4:203.0.113.45" : [v1, v2, ... v24],
"ipv6:2000::1:2345:6789:abcd" : [v1, v2, ... v24]
}
}
}
Randriamasy, et al. Expires March 25, 2019 [Page 21]
Internet-Draft ALTO Cost Calendar September 2018
When the Client gets the Calendar for "routingcost", it sees that the
"calendar-start-time" is Monday at 00h00 GMT and member "repeated" is
equal to '4'. It understands that the provided values are valid
until Thursday included and will only need to get a Calendar update
on Friday.
4.2.4. Use case and example: ECS with a multi-cost calendar for
routingcost and owdelay
In this example, it is assumed that the ALTO Server implements multi-
cost capabilities, as specified in [RFC8189] . That is, an ALTO
client can request and receive values for several cost types in one
single transaction. An illustrating use case is a path selection
done on the basis of 2 metrics: routing cost and owdelay.
As in the previous example, the IRD indicates that the ALTO Server
provides "routingcost" Calendars in terms of 24 time intervals of 1
hour each.
For metric "owdelay", the IRD indicates that the ALTO Server provides
Calendars in terms of 12 time intervals values lasting each 5
minutes.
In the following example transaction, the ALTO Client sends its
request on Tuesday July 1st 2014 at 13:15.
This example assumes that the values of metric "owdelay" are encoded
in 3 digits.
POST calendar/endpointcost/lookup HTTP/1.1
Host: alto.example.com
Content-Length: 401
Content-Type: application/alto-endpointcostparams+json
Accept: application/alto-endpointcost+json,application/alto-error+json
{
"cost-type" : {},
"multi-cost-types" : [
{"cost-mode" : "numerical", "cost-metric" : "routingcost"},
{"cost-mode" : "numerical", "cost-metric" : "owdelay"}
],
"calendared" : [true, true],
"endpoints" : {
"srcs": [ "ipv4:192.0.2.2" ],
"dsts": [
"ipv4:192.0.2.89",
"ipv4:198.51.100.34",
"ipv4:203.0.113.45",
Randriamasy, et al. Expires March 25, 2019 [Page 22]
Internet-Draft ALTO Cost Calendar September 2018
"ipv6:2000::1:2345:6789:abcd"
]
}
}
HTTP/1.1 200 OK
Content-Length: 1597
Content-Type: application/alto-endpointcost+json
{
"meta" : {
"multi-cost-types" : [
{"cost-mode" : "numerical", "cost-metric" : "routingcost"},
{"cost-mode" : "numerical", "cost-metric" : "owdelay"}
],
"calendar-response-attributes" : [
{"cost-type-name : num-routingcost"
"calendar-start-time" : Mon, 30 Jun 2014 00:00:00 GMT,
"time-interval-size" : "1 hour",
"number-of-intervals" : 24,
"repeated": 4 },
{"cost-type-name : num-owdelay"
"calendar-start-time" : Tue, 1 Jul 2014 13:00:00 GMT,
"time-interval-size" : "5 minute",
"number-of-intervals" : 12}
],
}
"endpoint-cost-map" : {
"ipv4:192.0.2.2": {
"ipv4:192.0.2.89" : [[r1, r2, ... r24], [o1, o2, ... o12]],
"ipv4:198.51.100.34" : [[r1, r2, ... r24], [o1, o2, ... o12]],
"ipv4:203.0.113.45" : [[r1, r2, ... r24], [o1, o2, ... o12]],
"ipv6:2000::1:2345:6789:abcd" : [[r1, r2, ... r24],
[o1, o2, ... o12]]
}
}
}
When receiving the response, the client sees that the calendar values
for 'routing cost' are repeated for 4 iterations. Therefore, in its
next requests until the routing cost calendar is expected to change,
the client will only need to request a calendar for "owdelay".
Without the ALTO Calendar extensions, the ALTO client would have no
clue on the dynamicity of the metric value change and would spend
needless time requesting values at an inappropriate pace. In
Randriamasy, et al. Expires March 25, 2019 [Page 23]
Internet-Draft ALTO Cost Calendar September 2018
addition, without the Multi-Cost ALTO capabilities, the ALTO client
would duplicate this waste of time as it would need to send one
request per cost metric.
5. IANA Considerations
This document does not define any new media types or introduce any
new IANA considerations.
6. Security Considerations
As an extension of the base ALTO protocol [RFC7285], this document
fits into the architecture of the base protocol, and hence the
Security Considerations (Section 15) of the base protocol fully apply
when this extension is provided by an ALTO server. For example, the
same authenticity and integrity considerations (Section 15.1 of
[RFC7285] still fully apply; the same considerations for the privacy
of ALTO users (Section 15.4 of [RFC7285]) also still fully apply.
The calendaring information provided by this extension requires
additional considerations on three security considerations discussed
in the base protocol: potential undesirable guidance to clients
(Section 15.2 of [RFC7285]), confidentiality of ALTO information
(Section 15.2 of [RFC7285]), and availability of ALTO (Section 15.5
of [RFC7285]). For example, by providing network information in the
future in a calendar, this extension may improve availability of
ALTO, when the ALTO server is unavailable but related information is
already provided in the calendar.
For confidentiality of ALTO information, an operator should be
cognizant that this extension may introduce a new risk: an ALTO
client may get information for future events that are scheduled
through calendaring. Possessing such information, the client may use
it to achieve its goal: (1) initiating connections only at
advantageous network costs, leading to unexpected network load; (2)
generating massive connections to the network at times where its load
is expected to be high.
To mitigate this risk, the operator should address the risk of ALTO
information being leaked to malicious clients or third parties. As
specified in Section 15.3.2 ("Protection Strategies") of [RFC7285],
the ALTO server should authenticate ALTO clients and use the
Transport Layer Security (TLS) protocol so that Man In The Middle
(MITM) attacks to intercept an ALTO Calendar are not possible.
[RFC7285] ensures the availability of such a solution in its
Section 8.3.5. "Authentication and Encryption", which specifies that
"ALTO server implementations as well as ALTO client implementations
Randriamasy, et al. Expires March 25, 2019 [Page 24]
Internet-Draft ALTO Cost Calendar September 2018
MUST support the "https" URI scheme [RFC2818] and Transport Layer
Security (TLS) [RFC5246]".
For potential undesirable guidance of ALTO information, an ALTO
client should be cognizant that using calendaring information can
have risks: (1) a repeat pattern may be only statistical, and (2)
future events may change. Hence, a more robust ALTO client should
adapt and extend protection strategies specified in Section 15.2 of
the base protocol: it should develop self check and also ensure
information update, to reduce the impact of this risk.
7. Operational Considerations
Conveying ALTO Cost Calendars tends to reduce the on-the-wire data
exchange volume compared to multiple single cost ALTO transactions,
as an application has a set of time-dependent values upon which it
can plan its connections in advance with no need for the ALTO Client
to query information at each time. Additionally, the Calendar
response attribute "repeated", when provided, saves additional data
exchanges in that it indicates that the ALTO Client does not need to
query Calendars during a period indicated by this attribute.
8. Acknowledgements
The authors would like to thank Fred Baker, Li Geng, Diego Lopez, He
Peng and Haibin Song for fruitful discussions and feedback on earlier
draft versions. Dawn Chan, Vijay Gurbani, Yichen Qian and Jensen
Zhang provided substantial review feedback and suggestions to the
protocol design.
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>.
[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>.
Randriamasy, et al. Expires March 25, 2019 [Page 25]
Internet-Draft ALTO Cost Calendar September 2018
[RFC8189] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost
Application-Layer Traffic Optimization (ALTO)", RFC 8189,
DOI 10.17487/RFC8189, October 2017,
<https://www.rfc-editor.org/info/rfc8189>.
9.2. Informative References
[draft-ietf-alto-performance-metrics]
Q. Wu, Y. Yang, Y. Lee, D. Dhody, S. Randriamasy, "ALTO
Performance Cost Metrics (work in progress)", June 2018.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000,
<https://www.rfc-editor.org/info/rfc2818>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic
Optimization (ALTO) Problem Statement", RFC 5693,
DOI 10.17487/RFC5693, October 2009,
<https://www.rfc-editor.org/info/rfc5693>.
Authors' Addresses
Sabine Randriamasy
Nokia Bell Labs
Route de Villejust
NOZAY 91460
FRANCE
Email: Sabine.Randriamasy@nokia-bell-labs.com
Richard Yang
Yale University
51 Prospect st
New Haven, CT 06520
USA
Email: yry@cs.yale.edu
Randriamasy, et al. Expires March 25, 2019 [Page 26]
Internet-Draft ALTO Cost Calendar September 2018
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: sunseawq@huawei.com
Lingli Deng
China Mobile
China
Email: denglingli@chinamobile.com
Nico Schwan
Thales Deutschland
Lorenzstrasse 10
Stuttgart 70435
Germany
Email: nico.schwan@thalesgroup.com
Randriamasy, et al. Expires March 25, 2019 [Page 27]