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ALTO WG                                                     G. Bernstein
Internet-Draft                                         Grotto Networking
Intended status: Standards Track                                  Y. Lee
Expires: January 7, 2016                                          Huawei
                                                                W. Roome
                                                               M. Scharf
                                                          Alcatel-Lucent
                                                                 Y. Yang
                                                         Yale University
                                                            July 6, 2015


          ALTO Extension: Abstract Path Vector as a Cost Mode
                   draft-yang-alto-path-vector-01.txt

Abstract

   The Application-Layer Traffic Optimization (ALTO) Service has defined
   network and cost maps to provide basic network information, where the
   cost maps allow only scalar (numerical or ordinal) cost mode values.
   This document introduces a new cost mode called path-vector to allow
   ALTO clients to better distinguish cost information.  This document
   starts with a non-normative use case called multi-flow scheduling to
   illustrate that ALTO cost maps without path vectors cannot provide
   sufficient information.  This document then defines path-vector as a
   new cost mode.

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 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."




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   This Internet-Draft will expire on January 7, 2016.

Copyright Notice

   Copyright (c) 2015 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  The Multi-flow Scheduling Use Case  . . . . . . . . . . . . .   3
   3.  Path-Vector as a new Cost Mode  . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Appendix A.  Network Element Properties Map . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The ALTO base protocol [RFC7285] is designed for a setting of
   exposing network topology using the extreme "my-Internet-view"
   representation, which abstracts a whole network as a single node that
   has a set of access ports, with each port connects to a set of
   endhosts.  The base protocol refers to each access port as a PID.
   This "single-node" abstraction is simple and can support a wide range
   of applications already.

   A problem of this abstraction, however, is that it does not provide
   sufficient information for use cases (e.g., multi-flow scheduling;
   see Section 3) that require exposure of topology information beyond
   the single-node abstraction, to detect sharing of the resources in
   the underlying topology.





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   This document goes beyond the single-node topology by introducing
   path vector as a new ALTO cost mode, where each path vector specifies
   abstracted network elements on the routing path from a set of source
   endhosts to a set of destination endhosts.  Since the network
   elements on a path vector are abstract network elements defined by
   ALTO servers, the new path-vector cost mode provides a mechanism to
   allow a network to control the level of topology exposure, and at the
   same time better support application traffic optimization.  The
   design of path vector is based on the ALTO WG discussions at IETF 89,
   with summary slides at http://tools.ietf.org/agenda/89/slides/slides-
   89-alto-2.pdf.

   The organization of this document is organized as follows.  Section 2
   gives a non-normative use case called multi-flow scheduling to
   illustrate the need to introduce path vectors.  Section 3 formally
   specifies the path vector cost mode.  Section 4 gives the Sections 4
   and 5 discuss security and IANA considerations.

2.  The Multi-flow Scheduling Use Case

   ALTO uses a simple single-node network abstraction.  Specifically,
   each network map in ALTO defines an abstract, single node network.
   Endhosts are partitioned to a set of access ports, with each access
   port called a PID.  For a given network map, a cost map of a given
   cost metric provides a scalar (numerical or ranking) cost value for
   each pair of source and destination PIDs.

   Although simple, the single-node, simple scalar cost maps may not
   convey enough information to the applications about pair-wise
   connection properties between one PID and another PID.  See [I-
   D.bernstein-alto-topo] for a survey of use-cases where extended
   network topology information is needed.

   This document uses a simple use case to illustrate the issue.
   Consider a network as shown in Figure 1.  The network has 7 switches
   (sw1 to sw7) forming a dumb-bell topology.  Switches sw1/sw3 provide
   access on one side, s2/s4 provide access on the other side, and
   sw5-sw7 form the backbone.  Endhosts eh1 to eh4 are connected to
   access switches sw1 to sw4 respectively.  Assume that the bandwidth
   of each link is 100 Mbps.  Assume that the network is abstracted with
   4 PIDs, with each representing the hosts at one access switch.










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                               +------+
                               |      |
                             --+ sw6  +--
                           /   |      |  \
     PID1 +-----+         /    +------+   \          +-----+  PID2
     eh1__|     |_       /                 \     ____|     |__eh2
          | sw1 | \   +--+---+         +---+--+ /    | sw2 |
          +-----+  \  |      |         |      |/     +-----+
                    \_| sw5  +---------+ sw7  |
     PID3 +-----+   / |      |         |      |\     +-----+  PID4
     eh3__|     |__/  +------+         +------+ \____|     |__eh4
          | sw3 |                                    | sw4 |
          +-----+                                    +-----+


                      Figure 1: Raw Network Topology.

   The single-node ALTO topology abstraction of the network is shown in
   Figure 2.

                    +----------------------+
           {eh1}    |                      |     {eh2}
           PID1     |                      |     PID2
             +------+                      +------+
                    |                      |
                    |                      |
           {eh3}    |                      |     {eh4}
           PID3     |                      |     PID4
             +------+                      +------+
                    |                      |
                    +----------------------+

             Figure 2: Base Single-Node Topology Abstraction.

   Consider an application overlay (e.g., a large data analysis system)
   which needs to schedule the traffic among a set of endhost source-
   destination pairs, say eh1 -> eh2, and eh3 -> eh4.  The application
   can request a cost map providing end-to-end available bandwidth,
   using 'available bw' as cost-metric and 'numerical' as cost-mode,
   where the 'available bw' between two PIDs represents available
   bandwidth for PIDi -> PIDj, if no other applications use shared
   resources.

   Assume that the application receives from the cost map that both PID1
   -> PID2 and PID3 -> PID4 have bandwidth 100 Mbps.  It cannot
   determine that if it schedules the two flows together, whether it
   will obtain a total of 100 Mbps or 200 Mbps.  This depends on whether




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   the routing of the two flows shares a bottleneck in the underlying
   topology:

   o  Case 1: If PID1 -> PID2 and PID3 -> PID4 use different paths, for
      example, when the first uses sw1 -> sw5 -> sw7 -> sw2, and the
      second uses sw3 -> sw5 -> sw6 -> sw7 -> sw4.  Then the application
      will obtain 200 Mbps.

   o  Case 2: If PID1 -> PID2 and PID3 -> PID4 share the bottleneck, for
      example, when both use the direct link sw5 -> sw7, then the
      application will obtain only 100 Mbps.

   To allow applications to distinguish the two aforementioned cases,
   the network needs to provide more details.  This document introduces
   path vector to resolve the issue.

3.  Path-Vector as a new Cost Mode

   An extension supporting the path-vector cost-mode MUST support the
   following extension of Section 11.2.3.6 of [RFC7285]:



     object {
       cost-map.DstCosts.JSONValue -> JSONString<0,*>;
       meta.cost-mode = "path-vector";
     } InfoResourcePVCostMap : InfoResourceCostMap;



   Specifically, the preceding specifies that InfoResourcePVCostMap
   extends InfoResourceCostMap.  The body specifies that the first
   extension is achieved by changing the type of JSONValue defined in
   DstCosts of cost-map to be an array of JSONString; the second
   extension is that the cost-mode of meta MUST be "path-vector".

   An example cost map using path-vector is the following:



     GET /costmap/pv HTTP/1.1
     Host: alto.example.com
     Accept: application/alto-costmap+json,application/alto-error+json








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     HTTP/1.1 200 OK
     Content-Length: TDB
     Content-Type: application/alto-costmap+json

     {
       "meta" : {
         "dependent-vtags" : [
           { "resource-id": "my-default-network-map",
             "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e"
           },
           {"resource-id": "my-topology-map", // See below
            "tag": "4xee2cb7e8d63d9fab71b9b34cbf76443631554de"
           }
         ],
         "cost-type" : { // removed: "cost-metric": "routingcost",
                        "cost-mode"  : "path-vector"
         }
       },

       "cost-map" : {
         "PID1": { "PID1":[],
                   "PID2":["ne56", "ne67"],
                   "PID3":[],
                   "PID4":["ne57"]
         },
         "PID2": { "PID1":["ne75"],
                   "PID2":[],
                   "PID3":["ne75"],
                   "PID4":[]
         },
         "PID3": { "PID1":[],
                   "PID2":["ne57"],
                   "PID3":[],
                   "PID4":["ne57"]
         },
         "PID4": { "PID1":["ne75"],
                   "PID2":[],
                   "PID3":["ne75"],
                   "PID4":[]}
       }
     }


   To interpret the path vectors in a cost map that provides path
   vectors, an ALTO client will need access to the properties of the
   abstract network elements named in the path vectors.  Such properties
   should be provided from a network element property service (e.g., the
   unified properties draft).  Hence, the "dependent-tags" of a cost map



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   supporting path vectors MUST include two dependent resources: one for
   a network map, which defines the grouping of endhosts, and the other
   for an element property service.  The network element property
   service (map) MUST provide a key-value service, where the key is a
   JSON string, and the value is the a map by itself, which has the
   property/metric name as key.  This document does not define the
   property service.  The appendix gives one definition, but it can be a
   different one.

4.  Security Considerations

   This document has not conducted its security analysis.

5.  IANA Considerations

   This document requires the definition of a new cost-mode named path-
   vector.

6.  Acknowledgments

   The author thanks discussions with Xiao Shi, Xin Wang, Erran Li,
   Tianyuan Liu, Andreas Voellmy, Haibin Song, and Yan Luo.

7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

7.2.  Informative References

   [I-D.amante-i2rs-topology-use-cases]
              Medved, J., Previdi, S., Lopez, V., and S. Amante,
              "Topology API Use Cases", draft-amante-i2rs-topology-use-
              cases-01 (work in progress), October 2013.

   [I-D.clemm-i2rs-yang-network-topo]
              Clemm, A., Medved, J., Tkacik, T., Varga, R., Bahadur, N.,
              and H. Ananthakrishnan, "A YANG Data Model for Network
              Topologies", draft-clemm-i2rs-yang-network-topo-01 (work
              in progress), October 2014.









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   [I-D.lee-alto-app-net-info-exchange]
              Lee, Y., Bernstein, G., Choi, T., and D. Dhody, "ALTO
              Extensions to Support Application and Network Resource
              Information Exchange for High Bandwidth Applications",
              draft-lee-alto-app-net-info-exchange-02 (work in
              progress), July 2013.

   [RFC7285]  Alimi, R., Penno, R., Yang, Y., Kiesel, S., Previdi, S.,
              Roome, W., Shalunov, S., and R. Woundy, "Application-Layer
              Traffic Optimization (ALTO) Protocol", RFC 7285, September
              2014.

Appendix A.  Network Element Properties Map

   A missing piece to complete the path-vector design to resolve the
   ambiguity in the use case is how to provide information on the
   elements of the path vectors.  A minimal approach is to introduce
   network element properties (NEP) maps, where each NEP map provides a
   mapping from a network element to its properties such as bandwidth or
   shared risk link group (srlg).

   A schema of an NEP map is:



     object-map {
       JSONString -> NetworkElementProperties; // name to properties
     } NetworkElementMapData;

     object-map {
       JSONString bw;
       JSONString srlg<0,*>;
       [JSONString type;] // should be from an enumeration only
     } NetworkElementProperties;


   An example network element property map:



     GET /nepmap HTTP/1.1
     Host: alto.example.com
     Accept: application/alto-nepmap+json,application/alto-error+json








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     HTTP/1.1 200 OK
     Content-Length: TBD
     Content-Type: application/alto-nepmap+json

     {
       "meta" : {
         "vtag": {
           "resource-id": "my-topology-map",
           "tag": "da65eca2eb7a10ce8b059740b0b2e3f8eb1d4785"
         }
       },
       "nep-map" : {
         "ne57" : {"bw" : 100, "srlg" : [1, 3]}, // link sw5->sw7
         "ne75" : {"bw" : 100, "srlg" : [1, 3]}, // link sw7->sw5
         "ne56" : {"bw" : 100, "srlg" : [1]},    // link sw5->sw6
         "ne65" : {"bw" : 100, "srlg" : [1]},    // link sw6->sw5
         "ne67" : {"bw" : 100, "srlg" : [3]},    // link sw6->sw7
         "ne76" : {"bw" : 100, "srlg" : [3]},    // link sw7->sw6
       }
     }


Authors' Addresses

   Greg Bernstein
   Grotto Networking
   Fremont, CA
   USA

   Email: gregb@grotto-networking.com


   Young Lee
   Huawei
   TX
   USA

   Email: leeyoung@huawei.com


   Wendy Roome
   Alcatel-Lucent Technologies/Bell Labs
   600 Mountain Ave, Rm 3B-324
   Murray Hill, NJ  07974
   USA

   Phone: +1-908-582-7974
   Email: w.roome@alcatel-lucent.com



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   Michael Scharf
   Alcatel-Lucent Technologies
   Germany

   Email: michael.scharf@alcatel-lucent.com


   Y. Richard Yang
   Yale University
   51 Prospect St
   New Haven  CT
   USA

   Email: yry@cs.yale.edu





































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