Network Working Group S. Randriamasy, Ed. Internet-Draft N. Schwan Intended status: Experimental Alcatel-Lucent Bell Labs Expires: September 6, 2012 March 5, 2012 ALTO Cost Schedule draft-randriamasy-alto-cost-schedule-00 Abstract The goal of Application-Layer Traffic Optimization (ALTO) is to bridge the gap between network and applications by provisioning network related information. This allows applications to make informed decisions, for example when selecting a target host from a set of candidates. The ALTO problem statement [RFC5693] considers typical applications as file sharing, real-time communication and live streaming peer-to-peer networks. Recently other use cases focused on Content Distribution Networks and Data Centers have emerged [draft-jenkins-alto-cdn-use-cases-01]. The present draft proposes to extend the cost information provided by the ALTO protocol. The purpose is to broaden the decision possibilities of applications to not only decide 'where' to connect to, but also 'when' to connect. This is useful to applications that have a degree of freedom on when to schedule data transfers, such as non-instantaneous data replication between data centers. The draft therefore specifies a new cost mode, called the "schedule" mode. In this mode the ALTO server offers cost maps that contain link ratings that are valid for a given timeframe (e.g. hourly) for a period of time (e.g. a day). Besides the functional time-shift enhancement providing multi-timeframe cost values the extansion also allows the saving of a number of ALTO transactions and thus resources on the ALTO server and clients. 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 Randriamasy & Schwan Expires September 6, 2012 [Page 1] Internet-Draft ALTO Cost Schedule March 2012 working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on September 6, 2012. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Randriamasy & Schwan Expires September 6, 2012 [Page 2] Internet-Draft ALTO Cost Schedule March 2012 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Use cases for ALTO Cost Schedule . . . . . . . . . . . . . . . 5 2.1. Bulk Data Transfer scheduling . . . . . . . . . . . . . . 5 2.2. Endsystems with limited access to datacenters using schedule mode . . . . . . . . . . . . . . . . . . . . . . 5 3. ALTO Cost Schedule . . . . . . . . . . . . . . . . . . . . . . 7 3.1. Cost Schedule Attributes . . . . . . . . . . . . . . . . . 7 3.1.1. ALTO Cost-Mode: Schedule . . . . . . . . . . . . . . . 7 3.2. ALTO Capability: Cost-Scope . . . . . . . . . . . . . . . 7 3.2.1. Example of time scope for a cost schedule . . . . . . 8 3.3. Example of scheduled information resources in the IRD . . 8 3.3.1. Example scenario and response with a cost schedule . . 10 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 4.1. Information for IANA on proposed Cost Types . . . . . . . 12 4.2. Information for IANA on proposed Endpoint Propeeries . . . 12 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.1. Normative References . . . . . . . . . . . . . . . . . . . 13 6.2. Informative References . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Randriamasy & Schwan Expires September 6, 2012 [Page 3] Internet-Draft ALTO Cost Schedule March 2012 1. Introduction IETF is currently standardizing the ALTO protocol which aims for providing guidance to overlay applications, that need to select one or several hosts from a set of candidates that are able to provide a desired resource. This guidance is based on parameters that affect performance and efficiency of the data transmission between the hosts, e.g., the topological distance. The goal of ALTO is to improve the Quality of Experience (QoE) in the application while simultaneously optimizing resource usage in the underlying network infrastructure. The ALTO protocol therefore [ID-alto-protocol] specifies a Network Map, which defines groupings of endpoints in a network region (called a PID) as seen by the ALTO server. The Endpoint Cost Service and the Endpoint (EP) Ranking Service then provide rankings for connections between the specified network regions and thus incentives for application clients to connect to ISP preferred endpoints, e.g. to reduce costs imposed to the network provider. Thereby ALTO intentionally avoids the provisioning of realtime information (cmp. ALTO Problem Statement [RFC5693] and ALTO Requirements [RFC5693]), as "Such information is better suited to be transferred through an in- band technique at the transport layer instead". Thus the current Cost Map and Endpoint Cost Service are providing, for a given Cost Type, exactly one rating per link between two PIDs or to en Endpoint. Applications are expected to query one of these two services in order to retrieve the currently valid cost values. They therefore need to plan their ALTO information requests according to the estimated frequency of cost value change. In case these value changes are predicable over a certain period of time and the application does not require immediate data transfer, it would save time to get the whole set of cost values over the period in one ALTO response and using these values to schedule data transfers would allow to optimise the network resources usage and QoE. In this draft we introduce use cases that describe applications that have a degree of freedom on scheduling data transfers over a period of time, thus they do not need to start a transfer instantaneously on a retrieved request. For this kind of applications we propose to extend the Cost Map and Endpoint Cost Services by adding a schedule on the cost values, allowing applications to time-shift data transfers. In addition to this functional ALTO enhancement, we expect to further gain by gathering multiple Cost Values for one cost type as one Cost Map reporting on N Cost Values is less bulky than N Cost Maps containing one Cost value each, in addition to reducing N ALTO transactions to a single one. This is valuable for both the storage Randriamasy & Schwan Expires September 6, 2012 [Page 4] Internet-Draft ALTO Cost Schedule March 2012 of these maps and their transfer. Similar gains can be obtained for the ALTO Endpoint Cost Service. The remainder of this draft first provides use cases that motivate the need for a 'schedule' cost mode. It then specifies the needed extensions to the ALTO protocol and details some example messages. 2. Use cases for ALTO Cost Schedule 2.1. Bulk Data Transfer scheduling Some CDNs are prepopulating caches with content before it actually gets available for the user and thus there is a degree of freedom on when the content is transmitted from the origin server to the chaching node. Other applications like Facebook or YouTube rely on data replication across multiple sites for several reasons, such as offloading the core network or increasing user experience through short latency. Typically the usage pattern of these data centers or caches follows a location dependent diurnal pattern. In the examples above data needs to be replicated across the various locations of a CDN provider, leading to bulk data transfers between datacenters. Scheduling these data transfers is a non-trivial task as the transfer should not infer with the user peak demand to avoid degradation of user experience and to decrease billing costs for the datacenter operator by leveraging off-peak hours for the transfer. This peak demand typically follows a diurnal pattern according to the geographic region of the datacenter. One precondition to schedule transfers however is to have a good knowledge about the demand and link utilization patterns between the different datacenters and networks. While this usage data today already is gathered and also used for the scheduling of data transfer, provisioning this data gets increasingly complex with the number of CDN nodes and in particular the number of datacenter operators that are involved. For example, privacy concerns prevent that this kind of data is shared across administrative domains. Therefore the Cost schedule specified later in this document avoids this problem by presenting an abstracted view of time sensitive utilization maps through a dedicated ALTO service to allow CDN operators a mutual scheduling of such data transfers across administrative domains. 2.2. Endsystems with limited access to datacenters using schedule mode Another use case that benefits from the availability of multi- timeframe cost information is based on applications that are limited Randriamasy & Schwan Expires September 6, 2012 [Page 5] Internet-Draft ALTO Cost Schedule March 2012 by their connectivity either in time or resources or both. For example applications running on devices in remote locations or in developing countries that need to synchronize their state with a data center periodically, in particular if sometimes there is no connection at all. Example applications is enterprise database update, remote learning, remote computation. Another challenge arises with endsystems using resources located in datacenters and trading content and resources scattered around the world. For non-real time applications, the interaction with Endpoints can be scheduled at the time slots corresponding to the best possible QoE. For instance, resource Ra downloaded from Endpoint (EP) 1 at time Ta, Resource Rb uploaded to EP2 at time Tb, some batch computation results RC downloaded from EP3 at Tc. Example applications are similar to the ones cited in the previous paragraph. These examples describe situations where a client has the choice of trading content or resources with several Endpoints and needs to decide with which Endpoint it will trade and at what time. For instance, one may assume that the Endpoints are spread over different time-zones, or have intermittent access. The ALTO schedule mode specified below allows these clients to retrieve Endpoint cost maps valid for a certain timeframe (e.g. 24 hours), and get a set of values, each applicable on a (e.g. hourly) slot. Thus the application can optimize the needed data transfer according to this information. Let us assume an Application Client is located in an end sytem with limited resources and/or has an access to the network that is either intermittent or provides an acceptable QoE in limited but predictable time periods. Therefore, it needs to both schedule its resources demanding networking activities. Instead of carefully schedule multiple ALTO requests for Cost values and having to figure out when the cost values may change it could benefit from relying on Cost attributes indicating the time granularity, the validity and time scope of the cost information, together with the values themselves. Suppose that for some Cost Types, the ALTO cost values are available in the "schedule" mode. If the values of Cost type 'routingcost' and/or another time-sensitive Cost Type named for example 'pathoccupationcost' are available in the "schedule" mode for the 24 following the last update, the ALTO Client embedded in the Application Client may query ALTO information on 'routingcost' or 'pathoccupationcost' for these 24 hours, and get a set of values, each applicable to an hour slot. If appropriate Cost Attributes are provided together with the cost values, the Application client also knows the date of their last update. An example ALTO transaction is provided later in this draft. Randriamasy & Schwan Expires September 6, 2012 [Page 6] Internet-Draft ALTO Cost Schedule March 2012 3. ALTO Cost Schedule One example of non-realtime information that can be provisioned in a 'schedule' is the expected path bandwidth. 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 on given time scales, for example to avoid hotspots due to diurnal usage patterns. The entity managing the ALTO Server values can decide to integrate path bandwidth in the ALTO 'routingcost' metric. However to better highlight the purpose of the cost schedule we will use the Cost Type name 'pathoccupationcost' in the remainder of this document. The usage of a time related cost is more proactive in that it can be used like a "time table" to figure out the best time to schedule data transfer and also anticipate predictable events including predictable flash crowds. The time-related information is not necessarily historical and statistic. This is why the proposed time-sensitive Costs should be viewed as synthetic or as abstraction of real measurements rather than as statistics. 3.1. Cost Schedule Attributes For further extensions, specifications on the cost "schedule" are proposed and will be completed in further versions of this draft. 3.1.1. ALTO Cost-Mode: Schedule The "schedule" mode applies to Costs that are eligible for a single- valued Cost Mode and can also be expressed as such. In that sense, when the "numerical" mode is available for a Cost-Type, the cost expressed in the "schedule" mode is an extension of its expression in the "numerical" mode to an array of several values varying over time. Types of Cost values such as JSONBool can also be expressed in the "schedule" mode, as states may be "true" or "false" depending on given time periods. It may be expressed as a single value which is either "true" or "false" following a decision rule outside the ALTO protocol. 3.2. ALTO Capability: Cost-Scope To ensure that the application client uses the NP provided information in the cost schedule in an unambiguous way we define the Cost Scope capability, which defines the validity of the "scheduled" cost values. Randriamasy & Schwan Expires September 6, 2012 [Page 7] Internet-Draft ALTO Cost Schedule March 2012 o Unit: expresses the time interval applicable to each value. A 2 element array where the first element is the time unit, ranging from "second" to "year", and the second one the number of units of this duration. For example: '["minute", 5]' means the values are provided on time interval lasting 5 minutes. o Size: the number of values of the cost schedule array, o Reference time zone, e.g. "CET", "PT". o Begin: the index of the first unit in the array, o Next update: the date at which the sample will be re-computed, o Last update: the last re-computation day. Attributes 'Last update 'and 'Next update' report on the update frequency and age of the information. 3.2.1. Example of time scope for a cost schedule For example: a metric called 'pathoccupationcost' (POC for short) is computed with a granularity of 2 hours, starting a 0h00, for 24 hours, with reference time GMT. The goal is to enable applications to see which time intervals in a day are the most favorable to operate, and in particular which hotspot time intervals to avoid. 3.3. Example of scheduled information resources in the IRD The example IRD given in this Section includes 2 particular URIs: o "http://alto.example.com/endpointcost/lookup", in which the ALTO Server offers several Endpoint Costs including a Cost called "pathoccupationcost" for which the "schedule" Cost Mode is available. The Endpoint Costs available are the "hopcount", "routingcost" and "pathoccupationcost" Cost Types, with the two first ones in the "numerical" Cost Mode and "pathoccupationcost" in the "schedule" Cost Mode. o "http://custom.alto.example.com/endpointcost/lookup", in which the ALTO Server provides the 'routingcost' in both "numerical" and "schedule" modes. This resource is accessible via a separate subdomain called "custom.alto.example.com". The ALTO Client may either get the last update of the 'routingcost' value or request for a previsonal sample of 24 values established each for 1 hour. An ALTO Client can discover the services available by "custom.alto.example.com" by successfully performing an OPTIONS request to "http://custom.alto.example.com/endpointcost". Randriamasy & Schwan Expires September 6, 2012 [Page 8] Internet-Draft ALTO Cost Schedule March 2012 OPTIONS /multi/endpointmulticost HTTP/1.1 Host: custom.alto.example.com Accept: application/alto-directory+json,application/alto-error+json HTTP/1.1 200 OK Content-Length: [TODO] Content-Type: application/alto-directory+json { ... usual ALTO resources ... "resources" : [ { "uri" : "http://alto.example.com/endpointcost", "media-types" : [ "application/alto-endpointcost+json" ], "accepts" : [ "application/alto-endpointcostparams+json" ], "capabilities" : { "cost-constraints" : true, "cost-modes" : [ "numerical", "numerical", "schedule" ], "cost-types" : [ "routingcost", "hopcount", "pathoccupationcost" ], "cost-scope": [ "permanent", "permanent", {"unit": ["hour", 1], "size": 24, "begin": 0, "time zone": "GMT", "lastupdate": mm/hh/dd/mm/yyyy, "nextupdate": mm/hh/dd/mm/yyyy} ] }, { "uri" : "http://custom.alto.example.com/endpointcost", "media-types" : [ "application/alto-endpointcost+json" ], "accepts" : [ "application/alto-endpointcostparams+json" ], "capabilities" : { "cost-constraints" : true, "cost-modes" : [ "numerical", "schedule" ], "cost-types" : [ "routingcost", "routingcost" ], "cost-scope": [ "permanent", {"unit": ["hour", 1], "size": 24, "begin": 0, "time zone": "GMT", "lastupdate": mm/hh/dd/mm/yyyy, "nextupdate": mm/hh/dd/mm/yyyy} ] } } ] } Randriamasy & Schwan Expires September 6, 2012 [Page 9] Internet-Draft ALTO Cost Schedule March 2012 3.3.1. Example scenario and response with a cost schedule The Application Client is located in an end sytem with limited resources and has an access to the network that is either intermittent or provides an acceptable quality in limited but possibly predictable time periods. Therefore, it needs to both schedule its resources demanding networking activities and minimize its ALTO transactions. The Application Client has the choice to trade content or resources with a set of Endpoints of moderate 'routingcost', and needs to decide with which Endpoint it will trade at what time. For instance, one may assume that the Endpoints are spread on different time-zones, or have intermittent access. In this example, the 'routingcost' is assumed constant for the scheduling period and the time sentitive decision metric is the path bandwidth reflected by a Cost type called 'pathoccupationcost'. The ALTO Client embedded in the Application Client queries ALTO information on 'pathoccupationcost' for the 24 hours following (implicitely) the date of "lastupdate", as this resource is listed in the IRD. Randriamasy & Schwan Expires September 6, 2012 [Page 10] Internet-Draft ALTO Cost Schedule March 2012 POST /endpointcost/lookup HTTP/1.1 Host: alto.example.com Content-Length: [TODO] Content-Type: application/alto-endpointcostparams+json Accept: application/alto-endpointcost+json,application/alto-error+json { "cost-type" : ["pathoccupationcost"], "cost-mode" : ["schedule"], "endpoints" : { "srcs": [ "ipv4:192.0.2.2" ], "dsts": [ "ipv4:192.0.2.89", "ipv4:198.51.100.34", "ipv4:203.0.113.45" ] } } HTTP/1.1 200 OK Content-Length: [TODO] Content-Type: application/alto-endpointcost+json { "meta" : {}, "data" : { "cost-type" : ["pathoccupationcost"], "cost-mode" : ["schedule"], "map" : { "ipv4:192.0.2.2": { "ipv4:192.0.2.89" : [7, ... 24 values], "ipv4:198.51.100.34" : [4, ... 24 values], "ipv4:203.0.113.45" : [2, ... 24 values] } } } } 4. IANA Considerations Information for the ALTO Endpoint property registry maintained by the IANA and related to the new Endpoints supported by the acting ALTO server. These definitions will be formulated according to the syntax defined in Section on "ALTO Endpoint Property Registry" of Randriamasy & Schwan Expires September 6, 2012 [Page 11] Internet-Draft ALTO Cost Schedule March 2012 [ID-alto-protocol], Information for the ALTO Cost Type Registry maintained by the IANA and related to the new Cost Types supported by the acting ALTO server. These definitions will be formulated according to the syntax defined in Section on "ALTO Cost Type Registry" of [ID-alto-protocol], 4.1. Information for IANA on proposed Cost Types When a new ALTO Cost Type is defined, accepted by the ALTO working group and requests for IANA registration MUST include the following information, detailed in Section 11.2: Identifier, Intended Semantics, Security Considerations. 4.2. Information for IANA on proposed Endpoint Propeeries Likewise, an ALTO Endpoint Property Registry could serve the same purposes as the ALTO Cost Type registry. Application to IANA registration for Endpoint Properties would follow a similar process. 5. Acknowledgements Thank you to Dave Mac Dysan (Verizon) for fruitful discussions. Sabine Randriamasy is partially supported by the MEVICO project (http ://www.celtic-initiative.org/Projects/Celtic-projects/Call7/MEVICO/ mevico-default.asp), a research project supported by the European Commission under its 7th Framework Program CELTIC initiative (project no. CP 07-011). The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the MEVICO project or the European Commission. Nico Schwan is partially supported by the ENVISION project (http://www.envision-project.org), a research project supported by the European Commission under its 7th Framework Program (contract no. 248565). The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the ENVISION project or the European Commission. 6. References Randriamasy & Schwan Expires September 6, 2012 [Page 12] Internet-Draft ALTO Cost Schedule March 2012 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic Optimization (ALTO) Problem Statement", RFC 5693, October 2009. 6.2. Informative References [ID-alto-protocol] , Eds., ""ALTO Protocol" draft-ietf-alto-protocol-10.txt", October 2011. [draft-jenkins-alto-cdn-use-cases-01] ""Use Cases for ALTO within CDNs" draft-jenkins-alto-cdn-use-cases-01", June 2011. Authors' Addresses Sabine Randriamasy (editor) Alcatel-Lucent Bell Labs Route de Villejust NOZAY 91460 FRANCE Email: Sabine.Randriamasy@alcatel-lucent.com Nico Schwan Alcatel-Lucent Bell Labs Lorenzstrasse 10 STUTTGART 70435 GERMANY Email: Nico.Schwan@alcatel-lucent.com Randriamasy & Schwan Expires September 6, 2012 [Page 13]