Network Working Group                                S. Randriamasy, Ed.
Internet-Draft                                                 N. Schwan
Intended status: Experimental                   Alcatel-Lucent Bell Labs
Expires: January 17, 2013                                  July 16, 2012


                           ALTO Cost Schedule
                draft-randriamasy-alto-cost-schedule-01

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 January 17, 2013                [Page 1]


Internet-Draft             ALTO Cost Schedule                  July 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 January 17, 2013.

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 January 17, 2013                [Page 2]


Internet-Draft             ALTO Cost Schedule                  July 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 . . 11
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
     4.1.  Information for IANA on proposed Cost Types  . . . . . . . 13
     4.2.  Information for IANA on proposed Endpoint Propeeries . . . 13
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 14
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14





























Randriamasy & Schwan    Expires January 17, 2013                [Page 3]


Internet-Draft             ALTO Cost Schedule                  July 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 January 17, 2013                [Page 4]


Internet-Draft             ALTO Cost Schedule                  July 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 January 17, 2013                [Page 5]


Internet-Draft             ALTO Cost Schedule                  July 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 January 17, 2013                [Page 6]


Internet-Draft             ALTO Cost Schedule                  July 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.

   For Cost Types whose values are provided in a mode different than



Randriamasy & Schwan    Expires January 17, 2013                [Page 7]


Internet-Draft             ALTO Cost Schedule                  July 2012


   '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 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 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

   For example: a metric called '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"



Randriamasy & Schwan    Expires January 17, 2013                [Page 8]


Internet-Draft             ALTO Cost Schedule                  July 2012


      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 at
      "custom.alto.example.com" by successfully performing an OPTIONS
      request to "http://custom.alto.example.com/endpointcost".








































Randriamasy & Schwan    Expires January 17, 2013                [Page 9]


Internet-Draft             ALTO Cost Schedule                  July 2012


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/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}
           ]
         }
       }
     ]
   }




Randriamasy & Schwan    Expires January 17, 2013               [Page 10]


Internet-Draft             ALTO Cost Schedule                  July 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 January 17, 2013               [Page 11]


Internet-Draft             ALTO Cost Schedule                  July 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 January 17, 2013               [Page 12]


Internet-Draft             ALTO Cost Schedule                  July 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 the ALTO WG 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 January 17, 2013               [Page 13]


Internet-Draft             ALTO Cost Schedule                  July 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 January 17, 2013               [Page 14]