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, . [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, . 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, . 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, . [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008, . [RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic Optimization (ALTO) Problem Statement", RFC 5693, DOI 10.17487/RFC5693, October 2009, . 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]