ALTO Extension: Path Vector Cost Map
draft-yang-alto-path-vector-02

ALTO WG                                                     G. Bernstein
Internet-Draft                                         Grotto Networking
Intended status: Standards Track                                  K. Gao
Expires: January 9, 2017                             Tsinghua University
                                                                  Y. Lee
                                                                  Huawei
                                                                W. Roome
                                                               M. Scharf
                                                                   Nokia
                                                                 Y. Yang
                                                         Yale University
                                                            July 8, 2016

                  ALTO Extension: Path Vector Cost Map
                   draft-yang-alto-path-vector-02.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 support use cases such as capacity regions for
   applications.  This document starts with a non-normative example
   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
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any

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   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 9, 2017.

Copyright Notice

   Copyright (c) 2016 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Example: Application-Capacity Region  . . . . . . . . . . . .   3
   3.  Path-Vector as a new Cost Mode  . . . . . . . . . . . . . . .   5
   4.  Capacity Region Query . . . . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Appendix A.  Network Element Properties Map . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

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.  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 that require exposure of
   topology information beyond the single-node abstraction, to detect
   sharing of the resources in the underlying topology (see Section 3).

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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 paths of a set of flows.
   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 example called multi-flow scheduling to
   illustrate the need to introduce path vectors.  Section 3 formally
   specifies the path vector cost mode.  Sections 4 and 5 discuss
   security and IANA considerations.

2.  Example: Application-Capacity Region

   Consider the case that routing is given.  Then what application-layer
   traffic optimization will focus on is traffic scheduling among
   application-layer paths.  Specifically, assume that an application
   has a set of flows F = {f1, f2, ..., f_|F|}. If routing is given,
   what the application can control is x1, x2, ..., x_|F|, where xi is
   the amount of traffic for flow i.  Let x = [x1, ..., x_|F|] be the
   vector of the flow traffic amounts.  Due to shared links, feasible
   values of x where link capacities are not exceeded can be a complex
   polytope.

   Specifically, 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.

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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.

   Assume that the application receives from the cost map that both eh1
   -> eh2 and eh3 -> eh4 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 the routing
   of the two flows shares a bottleneck in the underlying topology:

   o  Case 1: If eh1 -> eh2 and eh3 -> eh4 use different paths, for
      example, when the first uses sw1 -> sw5 -> sw7 -> sw2, and the

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      second uses sw3 -> sw5 -> sw6 -> sw7 -> sw4.  Then the application
      will obtain 200 Mbps.

   o  Case 2: If eh1 -> eh2 and eh3 -> eh4 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.  The path vector extension
   defined in this document resolves this issue.

   See [I-D.bernstein-alto-topo] for a survey of use-cases where
   extended network topology information is needed.

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".

   Also, to support such queries for both grouping of endpoints (PIDs)
   and individual endpoints, we extend cost map to use generic typed
   locations.

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

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

   {
       "dependent-vtags" : [    // defines the resource id providing nep
         { "resource-id": "my-nep-map",
           "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e"
         }
       ],

       "meta" : {
         "vtag" : {
           "resource-id": "my-costmap",
           "tag": "c0ce023b8678a7b9ec00324673b98e54656d1f6d"
         }
         "cost-type" : {"cost-mode": "path-vector"}
       }
     },

     "cost-map" : {
       "ipv4:192.0.2.2": {
                 "ipv4:192.0.2.89":    ["ne56"],
                 "ipv4:198.51.100.34": ["ne56", "ne57"],
                 "ipv4:203.0.113.45":  ["ne57"]
       },
       "ipv4:192.0.2.3": {
                 "ipv4:203.0.113.45":  ["ne57"]
       }
     }
   }

   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 [I-D.roome-alto-unified-props]).  Hence, the
   "dependent-tags" of a cost map supporting path vectors MUST include a
   resource id for unified properties.  If the location includes PIDs,
   the dependent resource should also include one for a network map, to
   define the grouping of endhosts.

4.  Capacity Region Query

   Path-vector cost maps can be used in many settings.  Below, we
   specify the concurrent flow capacity region service.  The result of
   the query below is already shown in the preceding section.

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     POST /capacityregion/lookup HTTP/1.1
     Host: alto.example.com
     Content-Length: TBD
     Content-Type: application/alto-flowparams+json
     Accept: application/alto-costmap+json,application/alto-error+json

     {
       "cost-type" : {"cost-mode":   "path-vector",
                      "cost-metric": "available-bw"}
       },
       "flows" : [
         {"src": "ipv4:192.0.2.2", "dst": "ipv4:192.0.2.89"},
         {"src": "ipv4:192.0.2.2", "dst": "ipv4:198.51.100.34"},
         {"src": "ipv4:192.0.2.2", "dst": "ipv4:203.0.113.45"},
         {"src": "ipv4:192.0.2.3", "dst": "ipv4:203.0.113.45"}
       ]
     }

5.  Security Considerations

   This document has not conducted its security analysis.

6.  IANA Considerations

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

7.  Acknowledgments

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

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

8.2.  Informative References

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   [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.

   [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.

   [I-D.roome-alto-unified-props]
              Roome, W., "Extensible Property Maps for the ALTO
              Protocol", draft-roome-alto-unified-props-00 (work in
              progress), July 2015.

   [RFC7285]  Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S.,
              Previdi, S., Roome, W., Shalunov, S., and R. Woundy,
              "Application-Layer Traffic Optimization (ALTO) Protocol",
              RFC 7285, DOI 10.17487/RFC7285, September 2014,
              <http://www.rfc-editor.org/info/rfc7285>.

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:

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     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

     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
       }
     }

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Authors' Addresses

   Greg Bernstein
   Grotto Networking
   Fremont, CA
   USA

   Email: gregb@grotto-networking.com

   Kai Gao
   Tsinghua University
   Beijing  Beijing
   China

   Email: gaok12@mails.tsinghua.edu.cn

   Young Lee
   Huawei
   TX
   USA

   Email: leeyoung@huawei.com

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

   Phone: +1-908-582-7974
   Email: wendy.roome@nokia.com

   Michael Scharf
   Nokia
   Germany

   Email: michael.scharf@nokia.com

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

   Email: yry@cs.yale.edu

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