Internet DRAFT - draft-randriamasy-alto-cost-schedule

draft-randriamasy-alto-cost-schedule







Network Working Group                                S. Randriamasy, Ed.
Internet-Draft                                  Alcatel-Lucent Bell Labs
Intended status: Experimental                                  N. Schwan
Expires: August 18, 2014
                                                       February 14, 2014


                           ALTO Cost Schedule
                draft-randriamasy-alto-cost-schedule-03

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.

   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'.  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 or service
   provisioning to end systems with irregular connectivity.  The draft
   therefore specifies a new cost mode, called the "schedule" mode.  In
   this mode the ALTO server offers cost maps that contain path 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 ALTO Cost Schedule also
   allows to save a number of ALTO transactions and thus resources on
   the ALTO server and clients.  Last, guidance to schedule application
   traffic can also efficiently help for load balancing and resources
   efficiency.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].







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Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on August 18, 2014.

Copyright Notice

   Copyright (c) 2014 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Use cases for ALTO Cost Schedule  . . . . . . . . . . . . . .   4
     2.1.  Bulk Data Transfer scheduling . . . . . . . . . . . . . .   5
     2.2.  Endsystems with limited connectivity or access to
           datacenters . . . . . . . . . . . . . . . . . . . . . . .   5
     2.3.  SDN Controller guided access to application endpoints . .   7
     2.4.  Large flow scheduling on extended ALTO topologies . . . .   9
     2.5.  Providing values for time-sensitve TE metrics . . . . . .  10
   3.  ALTO Cost Schedule extension  . . . . . . . . . . . . . . . .  10
     3.1.  Cost Schedule Attributes  . . . . . . . . . . . . . . . .  11
       3.1.1.  ALTO Cost-Mode: Schedule  . . . . . . . . . . . . . .  11
     3.2.  ALTO Capability: Cost-Scope . . . . . . . . . . . . . . .  11
       3.2.1.  Example of time scope for a cost schedule . . . . . .  12
     3.3.  Example of scheduled information resources in the IRD . .  12



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       3.3.1.  Example scenario and ALTO transaction with a Cost
               Schedule  . . . . . . . . . . . . . . . . . . . . . .  15
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
     4.1.  Information for IANA on proposed Cost Types . . . . . . .  17
     4.2.  Information for IANA on proposed Endpoint Propeeries  . .  17
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

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 an 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



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   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 firstly
   one Cost Map reporting on N Cost Values is less bulky than N Cost
   Maps containing one Cost value each and secondly, this reduces N ALTO
   transactions to a single one.  This is valuable for both the storage
   of these ALTO 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.
   Note that the example ALTO transactions are provided with the ALTO
   syntax as specified in previous ALTO protocol draft versions, see
   [ID-alto-protocol-13].  The syntax will be updated when the base ALTO
   protocol will be finalized.

2.  Use cases for ALTO Cost Schedule

   This section introduces use cases showing the benefits of providing
   ALTO Cost values in 'schedule' mode.  Most likely, the ALTO Cost
   Schedule would be used for the Endpoint Cost Service where a limited
   set of feasible non real time application Endpoints is already
   identified, they need to be accessed neither simultaneously nor
   immediately and 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 is manageable.  An ALTO Cost schedule can be used
   in several ways:

   o  the ALTO Server may provide values on past time periods that can
      be interpreted as historical experience and used to anticipate
      future cost values in order to schedule transfers of application
      data or services,

   o  the ALTO Server may provide stationary values on present or future
      time periods that can be interpreted as predictions on cost values
      and used to schedule transfers of application data or services,

   o  the ALTO Server may provide stationary values on time periods
      covering the past, present and future and logically be all
      interpreted as predictions and used to schedule transfers of
      application data or services.




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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 caching
   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.  The ALTO 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 connectivity or access to datacenters

   Another use case that benefits from the availability of multi-
   timeframe cost information is based on applications that are limited
   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 distributed on several
   data center endpoints.

   Wireless connectivity has a variable quality or may even be
   intermittent.  On the other hand, the connectivity conditions are



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   often predicable.  For non real time applications, it is thus
   desirable to provide ALTO clients with routing costs to connection
   nodes (i.e.  Application Endpoints) over different time periods.
   This would allow end systems using ALTO aware application clients to
   schedule their connections to application endpoints.

   Another challenge arises with end systems 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 EPa at time t1, Resource Rb uploaded to EPb at time t2, some
   batch computation involving Ra and Rb done on EPc at time t3 and
   results R(A,B) downloaded to EPd and EPe at time t4.  Example
   applications are similar to the ones cited in the previous paragraph.

     +-----+                                           +-----+
     | EPa |                                           | EPb | <----- Rb
     +-----+                                           +-----+   (t2=50)
        |                   +-------+                     |
        Ra -------------->  | EPc   |                     |
        (time t1=10)        |       |                     |
                            |t3=100 |  <----------------- Rb
                            +-------+
                                | \
                                |  \
                              R(Ra,Rb)
                             (t4=200)
                                |     \
                                |      -------------------.
                                V                         V
                             +-----+                   +-----+
                             | EPd |                   | EPe |
                             +-----+                   +-----+



   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.




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   Last, the ALTO Cost schedule is beneficial to optimizing ALTO
   transactions themselves.  Indeed, let us assume that 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.  In that
   case, it needs to both schedule its resources demanding networking
   activities and its ALTO requests.  Instead of having to figure out
   when the cost values may change and having to carefully schedule
   multiple ALTO requests, it could aviod this by relying on Cost
   Shedule attributes that indicate the time granularity, the validity
   and time scope of the cost information, together with the time
   related cost 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
   hours 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.

2.3.  SDN Controller guided access to application endpoints

   The Software Defined Networking (SDN), see [sdnrg], is a model that
   attempts to manage and reconfigure networks in a more flexible way in
   order to better cope with the traffic challenges posed by nowadays
   resources greedy applications.  To this end, one option is "moving
   the control plane out of the network elements into "controllers", see
   [SDN charter, http://www.1-4-5.net/~dmm/sdnrg/sdnrg.html], that
   implements the network control and management.  The SDN Controllers
   are deemed to gather the network state information and provide it in
   an abstracted form to SDN aware applications while gathering their
   requirements in QoE and exchanging other application "management"
   information and commands.

   The relevance of ALTO to perform a number of SDN functions has been
   recently highlighted.  An ALTO Server can assist an SDN Controller by
   hosting abstracted network information that can be provided to SDN
   aware applications via an ALTO Client.  It can also assist other SDN
   Control operations using information in and outside the ALTO scope.

   In particular, [article-gslh-alto-sdn] identifies SDN Controller
   functions that ALTO is well suited to perform: the primitives of
   Abstraction, Get network topology, Get network resources and Event



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   notification.  Additonally, the interaction between ALTO and SDN has
   been investigated in [draft-xie-alto-sdn] to provide applications
   with a path selection meeting QoS requirements on bandwidth and
   delay.

   Currently, the base ALTO protocol allows to perform the following SDN
   services, see [article-gslh-alto-sdn]:

   1.  Abstraction: through aggregation into PIDs, ranking and a generic
       cost type.

   2.  Get network topology: through the Map and the Cost Map Services

   3.  Get device capabilities: through the Endpoint Property Service.

   Another SDN primitive "Get network resources" provides applications
   with informations allowing them to evaluate the expected QoE.  QoE
   related information includes delay and bandwidth at the application
   endpoints as well as on the network paths.  Such information may be
   provided via the ALTO Service by proposed extensions of the ALTO
   protocol that define new ALTO Cost Types allowing to abstract and
   report QoE to applications.

   One key objective of an SDN controller is the ability to balance the
   application traffic whenever possible.  For non real time
   applications, data and resources transfer can be time shifted,
   resources availability may often be predicable and last, strong
   incentives for applications to time shift their traffic may be given
   by network operators appropriately setting routing cost values at
   different time values, according to their policy to cope with network
   occupation over time.

   To achieve this objective, the SDN controller can:

   1.  get the network state history from its controlled network
       elements through its southbound API

   2.  possibly derive an estimation or a prediction of these values
       over given time frames

   3.  store their abstraction in an ALTO Server in the form of ALTO
       Cost Schedule values defined for different time periods

   4.  deliver these values to the SDN applications via the ALTO
       Endpoint Cost Service, either as history or prediction or as
       estimations covering both the past and the future.

   This way:



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   o  One one hand, the applications get the best possible QoE, as they
      can pick the best time for them to access one or more Endpoints,

   o  One the other hand the SDN controller achieves load balancing as
      it may guide the application traffic so as to better distribute
      the traffic over time, and thus optimize its resources usage.

2.4.  Large flow scheduling on extended ALTO topologies

   [draft-yang-alto-topology-00] presents initial thinking on extending
   ALTO for topology exposure services, that would provide flexible
   abstractions based on the raw network topology.  Among other
   features, an ALTO topology may expose several paths between a source
   (src) and destination (dst), or topology details may be provided on
   restricted parts.  This work was presented to the ALTO WG at IETF88.

   The presentation slides [slides-88-alto-5-topology] on
   [draft-yang-alto-topology-00] expose a use case entitled "Large Flow
   Scheduling".  This case includes a "daylife example" where a Google
   Map service proposes multiple routes between 2 points A and B, each
   calculated w.r.t. length and estimated time.  For each of these
   selected paths, the map service exposes a time-sensitive qualitative
   value taking 4 values between Slow and Fast.  A user of this
   application may thus organize its transfer w.r.t. metrics, paths and
   time, provided s/he does not have to commute immediately.

   The use case on Large flow scheduling on extended ALTO topologies in
   the present section illustrates one modality of ALTO topology
   service, that would expose several paths between end to end (src,
   dst) pairs, computed w.r.t. one of more metrics, possibly under given
   constraints.  On top of this enriched topology service, non real-time
   applications may also choose the time of data/resources transfer,
   taking thus advantage of a richer set of decision variables.

   The use case "Large Flow Scheduling" of presentation
   [slides-88-alto-5-topology]can thus be adapted as follows:

   o  Step1 - obtain the set T transfer tasks {(src, dest, data)}

   o  Step2 - identify one or more paths for each (src, dst): several
      information sources exist among which:

      *  (a) ALTO CostMap with a "path" metric, // not specified here

      *  (b) an ALTO Topology Service providing a path computation hint
         (e.g. w.r.t. routingcost and/or other metrics)

   o  Step 3- while T not empty:



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      *  1 - query for example values for some metric 'available
         bandwidth' on paths:

         +  to this end, query the values in the ALTO 'schedule' Mode:
            on the selected (src, dst) for a set of time intervals.
            With this mode, the ALTO client will receive an array of
            values, each applicable to a time slot .

      *  2 - schedule data transfer at the time slots corresponding to
         the preferred value.

2.5.  Providing values for time-sensitve TE metrics

   Draft [draft-wu-alto-te-metrics-01], proposes to extend the set of
   ALTO metrics with traffic engineering (TE) metrics, in order to
   closely meet applications requirementsand under appropriate trust
   agreements.  This draft exposes a number of TE metrics that are time-
   sensitive, either by nature such as bandwidth and delay related
   metrics, or due to "normally" changing network conditions or both.

   The draft assumes that the values of ALTO TE metrics are typically
   collected from routing protocols and provided in a non-real time
   manner.  In "normally" changing network conditions TE metric values
   remain uniformly distributed over given time intervals and can be
   aggregated over bigger sample intervals of periodic patterns.  For
   instance an ALTO Server may collect values from a routing protocol
   produced by measurements done every second over a period of 30
   seconds.  The ALTO Server may then aggregate these values over ALTO
   Sample intervals of 60 seconds and every hour, provide the values in
   'schedule' mode endcoded as an array of 60 values.

   All time sensitive ALTO TE metrics are potentially applicable to a
   cost schedule.  The real applicability actually depend on the network
   topology and structure.  A small topology with low density and
   capacity that carries inpredictable heavy and bursty traffic has few
   chances to exhibit stationary TE metric value patterns over large
   periods and would benefit to use the ALTO Schedule over smaller time
   slots.

3.  ALTO Cost Schedule extension

   One example of non-real time 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 of 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



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   ALTO 'routingcost' metric.  However to better highlight the purpose
   of the cost schedule the remainder of this document will use a Cost
   Type named 'pathoccupationcost' and assumed to report an abstracted
   form of available bandwidth.  A definition and usage of such a Cost-
   Type is proposed in [draft-randriamasy-multi-cost-alto].

   The usage of a time related cost is rather 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.  An ALTO Cost Schedule should be viewed as
   a synthetic abstraction of real measurements that can be historic or
   be a prediction for upcoming time periods.

3.1.  Cost Schedule Attributes

   Specifications on the cost "schedule" are proposed here 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
   from one value 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.

   For Cost Types whose values are provided in a mode different than
   'schedule', the Cost Scope capability is specified by the string
   "permanent".  The Cost Scope attributes provided for the 'schedule'
   mode are listed below.  The reference time zone for the provided
   values is UTC.

   o  Unit: expresses the time interval applicable to each value.  A two
      element array where the first element is the time unit, ranging



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      from "second" to "year", and the second one the number of units of
      this duration.  For example: '["minute", 5]' means that each value
      is provided on a time interval lasting 5 minutes.

   o  Size: the number of values of the cost schedule array,

   o  Begin: the index of the first unit in the array,

   o  Reference time zone: set to "UTC",

   o  Next update: the date at which the sample will be re-computed,

   o  Last update: the last re-computation date.

   The reference time zone is UTC.

   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

   Let us assume that the metric 'pathoccupationcost' (POC for short) is
   computed for 24 hours, on time intervals lasting 2 hours, with the
   first interval starting at 0h00.  The ALTO Server thus provides an
   array 12 values.  This information is then used to enable
   applications to see which time intervals in a day are the most
   favorable to operate, and which "busy " time intervals should be
   avoided.  If the "Begin" date is past, the application can also use
   the information to compute statistics or infer a some customized
   prediction.

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 Cost Types, 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/schedule/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



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      or request for a previsonal sample of 24 values established each
      for 1 hour.  An ALTO Client can discover the services available at
      "custom.alto.example.com" by successfully performing an OPTIONS
      request to "http://custom.alto.example.com/endpointcost".















































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GET /directory HTTP/1.1
   Host: 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/lookup",
         "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": "UTC",
                             "lastupdate": mm/hh/dd/mm/yyyy,
                             "nextupdate": mm/hh/dd/mm/yyyy}
           ]
         },
      {
         "uri" : "http://custom.alto.example.com/endpointcost/schedule/lookup",
         "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": "UTC",
                             "lastupdate": mm/hh/dd/mm/yyyy,
                             "nextupdate": mm/hh/dd/mm/yyyy}
           ]
         }
       }
     ]
   }




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3.3.1.  Example scenario and ALTO transaction with a Cost Schedule

   Let us assume an Application Client located in an end sytem with
   limited resources and having 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.





























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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
   [ID-alto-protocol],



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   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 D. Lopez, R. Yang, H. Peng, Q. Wu and the ALTO WG for
   fruitful discussions.

6.  References

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-13]
              R.Alimi, R. Penno, Y. Yang, Eds., "ALTO Protocol, draft-
              ietf-alto-protocol-13.txt", September 2012.

   [ID-alto-protocol]
              R.Alimi, R. Penno, Y. Yang, Eds., "ALTO Protocol, draft-
              ietf-alto-protocol-25.txt", January 2014.







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   [article-gslh-alto-sdn]
              V. Gurbani, M. Scharf, T.Lakshman, and V. Hilt, ,
              "Abstracting network state in Software Defined Networks
              (SDN) for rendezvous services, IEEE International
              Conference on Communications (ICC) Workshop on Software
              Defined Networks (SDN)", June 2012.

   [draft-jenkins-alto-cdn-use-cases-01]
              B. Niven-Jenkins (Ed.), G. Watson, N. Bitar, J. Medved, S.
              Previdi, , "Use Cases for ALTO within CDNs, draft-jenkins-
              alto-cdn-use-cases-01", June 2011.

   [draft-randriamasy-multi-cost-alto]
              S. Randriamasy, Ed., B. Roome, N. Schwan, , "Multi-Cost
              ALTO, draft-randriamasy-alto-multi-cost-07", October 2012.

   [draft-wu-alto-te-metrics-01]
              Q. Wu, Y. Yang, Y. Lee, D. Dhody, S. Randriamasy, , "ALTO
              Traffic Engineering Cost Metrics (work in progress)",
              February 2014.

   [draft-xie-alto-sdn]
              H. Xie, T. Tsou, D. Lopez, H. Yin, , "Use Cases for ALTO
              with Software Defined Networks, draft-xie-alto-sdn-
              extension-use-cases-00", June 2012.

   [draft-yang-alto-topology-00]
              Y. Yang, , "ALTO Topology Considerations (work in
              progress)", July 2013.

   [sdnrg]    "Software Defined Network Research Group,
              http://trac.tools.ietf.org/group/irtf/trac/wiki/sdnrg", .

   [slides-88-alto-5-topology]
              G. Bernstein, Y. Lee, Y. Yang, , , "ALTO Topology Service:
              Use Cases, Requirements and Framework (presentation slides
              IETF88 ALTO WG session), http://tools.ietf.org/agenda/88/
              slides/slides-88-alto-5.pdf", November 2013.

Authors' Addresses

   Sabine Randriamasy (editor)
   Alcatel-Lucent Bell Labs
   Route de Villejust
   NOZAY  91460
   FRANCE

   Email: Sabine.Randriamasy@alcatel-lucent.com



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   Nico Schwan

   Email: ietf@nico-schwan.de
















































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