[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-yang-alto-path-vector) 00 01 02 03 04 05 06 07 08

ALTO WG                                                           K. Gao
Internet-Draft                                        Sichuan University
Intended status: Standards Track                                  Y. Lee
Expires: January 23, 2020                                         Huawei
                                                          S. Randriamasy
                                                         Nokia Bell Labs
                                                                 Y. Yang
                                                         Yale University
                                                                J. Zhang
                                                       Tongji University
                                                           July 22, 2019


                      ALTO Extension: Path Vector
                     draft-ietf-alto-path-vector-08

Abstract

   This document defines an ALTO extension that allows a resource to
   provide not only preferences of network paths but also correlations
   of network paths, including aggregations of network components and
   their properties on the paths between different PIDs or endpoints.
   The extended information can be used to improve the robustness and
   performance for applications in some new usage scenarios, such as
   high-speed data transfers and traffic optimization using in-network
   storage and computation.  This document introduces abstract network
   element (ANE) as an abstraction for aggregations of network
   components.  It extends the base protocol and the Unified Property
   extension to enable the capability of encoding such information in a
   "path vector", i.e., an array of ANEs that are traversed by traffic
   from a source to a destination.

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/.




Gao, et al.             Expires January 23, 2020                [Page 1]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   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 23, 2020.

Copyright Notice

   Copyright (c) 2019 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  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Shared Risk Resource Group  . . . . . . . . . . . . . . .   6
     3.2.  Capacity Region . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  In-Network Caching  . . . . . . . . . . . . . . . . . . .   9
   4.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
     4.1.  Workflow  . . . . . . . . . . . . . . . . . . . . . . . .  10
     4.2.  Abstract Network Element  . . . . . . . . . . . . . . . .  11
     4.3.  Protocol Extensions . . . . . . . . . . . . . . . . . . .  12
       4.3.1.  Path Vector Cost Type . . . . . . . . . . . . . . . .  12
       4.3.2.  Property Negotiation  . . . . . . . . . . . . . . . .  12
       4.3.3.  Multipart/Related Message . . . . . . . . . . . . . .  13
   5.  Basic Data Types  . . . . . . . . . . . . . . . . . . . . . .  14
     5.1.  ANE Identifier  . . . . . . . . . . . . . . . . . . . . .  15
     5.2.  Path Vector Cost Type . . . . . . . . . . . . . . . . . .  15
       5.2.1.  Cost Metric: ane-path . . . . . . . . . . . . . . . .  15
       5.2.2.  Cost Mode: array  . . . . . . . . . . . . . . . . . .  15
     5.3.  ANE Domain  . . . . . . . . . . . . . . . . . . . . . . .  15
       5.3.1.  Entity Domain Type  . . . . . . . . . . . . . . . . .  16
       5.3.2.  Domain-Specific Entity Identifier . . . . . . . . . .  16
       5.3.3.  Hierarchy and Inheritance . . . . . . . . . . . . . .  16
     5.4.  New Resource-Specific Entity Domain Exports . . . . . . .  16
       5.4.1.  ANE Domain of Cost Map Resource . . . . . . . . . . .  16



Gao, et al.             Expires January 23, 2020                [Page 2]


Internet-Draft         ALTO Extension: Path Vector             July 2019


       5.4.2.  ANE Domain of Endpoint Cost Resource  . . . . . . . .  16
     5.5.  ANE Properties  . . . . . . . . . . . . . . . . . . . . .  16
       5.5.1.  ANE Property: Maximum Reservable Bandwidth  . . . . .  16
       5.5.2.  ANE Property: Persistent Entity . . . . . . . . . . .  17
     5.6.  Part Resource ID  . . . . . . . . . . . . . . . . . . . .  17
   6.  Service Extensions  . . . . . . . . . . . . . . . . . . . . .  17
     6.1.  Multipart Filtered Cost Map for Path Vector . . . . . . .  17
       6.1.1.  Media Type  . . . . . . . . . . . . . . . . . . . . .  17
       6.1.2.  HTTP Method . . . . . . . . . . . . . . . . . . . . .  17
       6.1.3.  Accept Input Parameters . . . . . . . . . . . . . . .  18
       6.1.4.  Capabilities  . . . . . . . . . . . . . . . . . . . .  18
       6.1.5.  Uses  . . . . . . . . . . . . . . . . . . . . . . . .  19
       6.1.6.  Response  . . . . . . . . . . . . . . . . . . . . . .  19
     6.2.  Multipart Endpoint Cost Service for Path Vector . . . . .  20
       6.2.1.  Media Type  . . . . . . . . . . . . . . . . . . . . .  20
       6.2.2.  HTTP Method . . . . . . . . . . . . . . . . . . . . .  20
       6.2.3.  Accept Input Parameters . . . . . . . . . . . . . . .  20
       6.2.4.  Capabilities  . . . . . . . . . . . . . . . . . . . .  21
       6.2.5.  Uses  . . . . . . . . . . . . . . . . . . . . . . . .  21
       6.2.6.  Response  . . . . . . . . . . . . . . . . . . . . . .  21
   7.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  22
     7.1.  Example: Information Resource Directory . . . . . . . . .  22
     7.2.  Example: Multipart Filtered Cost Map  . . . . . . . . . .  24
     7.3.  Example: Multipart Endpoint Cost Resource . . . . . . . .  26
     7.4.  Example: Incremental Updates  . . . . . . . . . . . . . .  28
   8.  Compatibility . . . . . . . . . . . . . . . . . . . . . . . .  29
     8.1.  Compatibility with Legacy ALTO Clients/Servers  . . . . .  29
     8.2.  Compatibility with Multi-Cost Extension . . . . . . . . .  29
     8.3.  Compatibility with Incremental Update . . . . . . . . . .  29
     8.4.  Compatibility with Cost Calendar  . . . . . . . . . . . .  29
   9.  General Discussions . . . . . . . . . . . . . . . . . . . . .  30
     9.1.  Provide Calendar for Property Map . . . . . . . . . . . .  30
     9.2.  Constraint Tests for General Cost Types . . . . . . . . .  30
     9.3.  General Multipart Resources Query . . . . . . . . . . . .  31
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  31
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  32
     11.1.  ALTO Cost Mode Registry  . . . . . . . . . . . . . . . .  32
     11.2.  ALTO Entity Domain Registry  . . . . . . . . . . . . . .  32
     11.3.  ALTO Entity Property Type Registry . . . . . . . . . . .  32
     11.4.  ALTO Resource Entity Domain Export Registries  . . . . .  32
       11.4.1.  costmap  . . . . . . . . . . . . . . . . . . . . . .  33
       11.4.2.  endpointcost . . . . . . . . . . . . . . . . . . . .  33
   12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  33
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  33
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  33
     13.2.  Informative References . . . . . . . . . . . . . . . . .  34
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  34




Gao, et al.             Expires January 23, 2020                [Page 3]


Internet-Draft         ALTO Extension: Path Vector             July 2019


1.  Introduction

   The ALTO protocol is aimed to provide applications with knowledge of
   the underlying network topologies from the point of views of ISPs.
   The base protocol [RFC7285] defines cost maps and endpoint cost
   services that expose the preferences of network paths for a set of
   source and destination pairs.

   While the preferences of network paths are already sufficient for a
   wide range of applications, new application traffic patterns and new
   network technologies are emerging that are well beyond the domain for
   which existing ALTO maps are engineered, including but not limited
   to:

   Very-high-speed data transfers:  Applications, such as Content
      Distribution Network (CDN) overlays, geo-distributed data centers
      and large-scale data analytics, are foundations of many Internet
      services today and have very large traffic between a source and a
      destination.  Thus, the interference between traffic of different
      source and destination pairs cannot be omitted, which cannot be
      provided by or inferred from existing ALTO base protocol and
      extensions.

   In-network storage and computation:  Emerging networking technologies
      such as network function virtualization and mobile edge computing
      provide storage and computation inside the network.  Applications
      can leverage these resources to further improve their performance,
      for example, using in-network caching to reduce latency and
      bandwidth from a given source to multiple clients.  However,
      existing ALTO extensions provide no map resources to discover
      available in-network services, nor any information to help ALTO
      clients determine how to effectively and efficiently use these
      services.

   This document specifies a new extension to incorporate these newly
   emerged scenarios into the ALTO framework.  The essence of this
   extension is that an ALTO server exposes correlations of network
   paths in additional to preferences of network paths.

   The correlations of network paths are represented by path vectors.
   Each element in a path vector, which is referred to as an abstract
   network element (ANE), is the aggregation of network components on
   the path, such as routers, switches, links and clusters of in-network
   servers.  If an abstract network element appears in multiple network
   paths, the traffic along these paths will join at this abstract
   network element and are subject to the corresponding resource
   constraints.




Gao, et al.             Expires January 23, 2020                [Page 4]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   The availability of the path correlations by itself can help ALTO
   clients conduct better traffic scheduling.  For example, an ALTO
   client can use the path correlations to conduct more intelligent end-
   to-end measurement and identify traffic bottlenecks.

   By augmenting these abstract network elements with different
   properties, an ALTO server can provide a more fine-grained view of
   the network.  ALTO clients can use this view to derive information
   such as shared risk resource groups, capacity regions and available
   in-network cache locations, which can be used to improve the
   robustness and performance of the application traffic.

2.  Terminology

   This document extends the ALTO base protocol [RFC7285] and the
   Unified Property Map extension [I-D.ietf-alto-unified-props-new].  In
   additional to the ones defined in these documents, this document also
   uses the following additional terms:

   o  Abstract network element (ANE): An abstract network element is an
      abstraction of network components.  It can be a link, a
      middleboxes, a virtualized network function (VNF), etc., or their
      aggregations.  In a response, each abstract network element has a
      unique ANE identifier.

   o  Path vector: A path vector is an array of ANE identifiers.  It
      presents an abstract network path between source/destination
      points such as PIDs or endpoints.

   o  Path vector resource: A path vector resource refers to an ALTO
      resource which supports the extension defined in this document.

   o

   o  Path vector response: A path vector response refers to the
      multipart/related message returned by a path vector resource.  It
      consists of a path vector part, i.e., the (endpoint) cost map part
      which contains the path vector information, and a property map
      part.

3.  Use Cases

   This section describes typical use cases of the path vector
   extension.  These use cases provide new usage scenarios of the ALTO
   framework.






Gao, et al.             Expires January 23, 2020                [Page 5]


Internet-Draft         ALTO Extension: Path Vector             July 2019


3.1.  Shared Risk Resource Group

   Consider an application which controls 4 end hosts (eh1, eh2, eh3 and
   eh4), which are connected by an ISP network with 5 switches (sw1,
   sw2, sw3, sw4 and sw5) and 5 links (l1, l2, l3, l4 and l5), as shown
   in Figure 1.  Assume the end hosts are running data storage services
   and some analytics tasks, which requires high data availability.  In
   order to determine the replica placement, the application must know
   how the end hosts will be partitioned if certain network failures
   happen.

                              +-----------------+
                ------------->|                 |<---------
               /   ---------->|   ALTO Client   |<------   \
              /   /           +-----------------+       \   \
             |   |                    ^                  |   |
             |   |                    |                  |   |
             |   |                    v                  |   |
             |   |            +-----------------+        |   |
             |   |  ..........|                 |......  |   |
             |   |  .         |   ALTO Server   |     .  |   |
             |   |  .         +-----------------+     .  |   |
             |   |  .                                 .  |   |
             |   v  . +-----+                 +-----+ .  v   |
             |  eh1 --|     |-         l3.   -|     |-- eh3  |
             |      . | sw1 | \..l1       ../ | sw4 | .      |
             |      . +-----+  \  +-----+  /  +-----+ .      |
             |      .           --|     |--      |    .      |
             |      .             | sw3 |    l5..|    .      |
             |      .           --|     |--      |    .      |
             |      . +-----+  /  +-----+  \  +-----+ .      |
             |      . |     | /..l2     l4..\ |     | .      |
             -->eh2 --| sw2 |-               -| sw5 |-- eh4<--
                    . +-----+                 +-----+ .
                    ...................................

       Figure 1: Topology for the Shared Risk Resource Group and the
                         Capacity Region Use Cases

   For that purpose, the application uses an ALTO client, which
   communicates with an ALTO server provided by the ISP network.  Since
   the Endpoint Cost Service with only scalar cost values cannot provide
   essential information for the application, thus, both the client and
   the server have the path vector extension enabled.

   Assume the ISP uses shortest path routing.  For simplicity, consider
   the data availability on eh4.  The network components on the paths
   from all other end hosts to eh4 are as follows:



Gao, et al.             Expires January 23, 2020                [Page 6]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   eh1->eh4: sw1, l1, sw3, l4, sw5
   eh2->eh4: sw2, l2, sw3, l4, sw5
   eh3->eh4: sw4, l5, sw5

   These network components can be categorized into 5 categories:

   1.  Failure will only disconnect eh1 to eh4: sw1, l1.

   2.  Failure will only disconnect eh2 to eh4: sw2, l2.

   3.  Failure will only disconnect eh3 to eh4: sw4, l5.

   4.  Failure will only disconnect eh1 and eh2 to eh4: sw3, l4.

   5.  Failure will disconnect eh1, eh2 and eh3 to eh4: sw5.

   The ALTO server can then aggregate sw1 and l1 as an abstract network
   element, ane1.  By applying the aggregation to the categories, the
   response may be as follows:

   eh1->eh4: ane1, ane4, ane5
   eh2->eh4: ane2, ane4, ane5
   eh3->eh4: ane3, ane5

   Thus, the application can still derive the potential network
   partitions for all possible network failures without knowing the
   exact network topology, which protects the privacy of the ISP.

3.2.  Capacity Region

   This use case uses the same topology and application settings as in
   Section 3.1 as shown in Figure 1.  Assume the capacity of each link
   is 10 Gbps, except l5 whose capacity is 5 Gbps . Assume the
   application is running a map-reduce task, where the optimal traffic
   scheduling is usually referred to the co-flow scheduling problem.
   Consider a simplified co-flow scheduling problem, e.g., the first
   stage of a map-reduce task which needs to transfer data from two data
   nodes (eh1 and eh3) to the mappers (eh2 and eh4).  In order to
   optimize the job completion time, the application needs to determine
   the bottleneck of the transfers.

   If the ALTO server encodes the routing cost as bandwidth of the path,
   the client will obtain the following information:

   eh1->eh2: 10 Gbps,
   eh1->eh4: 10 Gbps,
   eh3->eh2: 10 Gbps,
   eh3->eh4:  5 Gbps.



Gao, et al.             Expires January 23, 2020                [Page 7]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   However, it does not provide sufficient information to determine the
   bottleneck.  With the path vector extension, the ALTO server will
   first return the correlations of network paths between eh1, eh3 and
   eh2, eh4, as follows:

   eh1->eh2: ane1 (l1), ane2 (l2),
   eh1->eh4: ane1 (l1), ane4 (l4),
   eh3->eh2: ane3 (l3), ane2 (l2),
   eh3->eh3: ane5 (l5).

   Meanwhile, the ALTO server can also return the capacity of each ANE:

   ane1.capacity = 10 Gbps,
   ane2.capacity = 10 Gbps,
   ane3.capacity = 10 Gbps,
   ane4.capacity = 10 Gbps,
   ane5.capacity =  5 Gbps.

   With the correlation of network paths and the link capacity property,
   the client is able to derive the capacity region of data transfer
   rates.  Let x1 denote the transfer rate of eh1->eh2, x2 denote the
   rate of eh1->eh4, x3 denote the rate of eh3->eh2, and x4 denote the
   rate of eh3->eh4.  The application can derive the following
   information from the responses:

         eh1->eh2  eh1->eh4  eh3->eh2  eh3->eh4      capaity
   ane1     1         1         0         0      |   10 Gbps
   ane2     1         0         1         0      |   10 Gbps
   ane3     0         0         1         0      |   10 Gbps
   ane4     0         1         0         0      |   10 Gbps
   ane5     0         0         0         1      |    5 Gbps

   Specifically, the coefficient matrix on the left hand side is the
   transposition of the matrix directly derived from the path vector
   part, and the right-hand-side vector is directly derived from the
   property map part.  Thus, the bandwidth constraints of the data
   transfers are as follows:

   x1 + x2 <= 10 Gbps (ane1),
   x1 + x3 <= 10 Gbps (ane2),
   x2 + x3 <= 10 Gbps (ane3),
   x2      <= 10 Gbps (ane4),
   x4      <=  5 Gbps (ane5).








Gao, et al.             Expires January 23, 2020                [Page 8]


Internet-Draft         ALTO Extension: Path Vector             July 2019


3.3.  In-Network Caching

   Consider an application which controls 3 end hosts (eh1, eh2 and
   eh3), which are connected by an ISP network and the Internet, as
   shown in Figure 2.  Assume two clients at end hosts eh2 and eh3 are
   downloading the same data from a data server at eh1.  Meanwhile, the
   network provider offers an in-network caching service at the gateway.

                       +-------------+
               ------->|             |<-----------------------
              /  ----->| ALTO Client |<-------                \
             /  /      +-------------+       |                 \
            /  /                             v                  |
           /  /                          +-------------+        |
          /  /   ........................| ALTO Server |......  |
         /  /    .                       +-------------+     .  |
        /  /     .                     +---------+           .  |
       |  |      .                    -+ Caching |           .  |
       |  |      .                   / | Proxy   |           .  |
       |  |S     .+-------+         /  +---------+           .  |
       |  -->eh1--| sub   |_       |                         .  |
       |         .| net 1 | \   +------+         +----------+.  |
       |         .+-------+  ---|      |         |          |.  v C2
       |         .              | Gate +---------+ Internet |--eh3
       |   C1    .+-------+   --| way  |         |          |.
       ----->eh2--| sub   |__/  +------+         +----------+.
                 .| net 2 |                                  .
                 .+-------+                                  .
                 .............................................

          Figure 2: Topology for the In-Network Caching Use Case.

   With the path vector extension enabled, the ALTO server can expose
   two types of information

   Without the traffic correlation information, the ALTO client cannot
   know whether or how the traffic goes through the proxy.  For example,
   if subnet1 and subnet2 are directly connected and the traffic from
   eh1 to eh2 bypasses the gateway, the in-network cache can only be
   used for traffic from C2 to S and is less effective.

4.  Overview

   This section gives a top-down overview of approaches adopted by the
   path vector extension, with discussions to fully explore the design
   space.  It is assumed that readers are familiar with both the base
   protocol [RFC7285] and the Unified Property Map extension
   [I-D.ietf-alto-unified-props-new].



Gao, et al.             Expires January 23, 2020                [Page 9]


Internet-Draft         ALTO Extension: Path Vector             July 2019


4.1.  Workflow

   The workflow of the base ALTO protocol consists of one round of
   communication: An ALTO client sends a request to an ALTO server, and
   the ALTO server returns a response, as shown in Figure 3.  Each
   response contains only one type of ALTO resources, e.g., network
   maps, cost maps, or property maps.

         +-------------+                          +-------------+
         | ALTO Client |                          | ALTO Server |
         +-------------+                          +-------------+
                |               Request                  |
                |--------------------------------------->|
                |                                        |
                |               Response                 |
                |<---------------------------------------|
                |                                        |
                .                   .                    .
                .                   .                    .
                .                   .                    .
                |              PV Request                |
                |--------------------------------------->|
                |                                        |
                |       PV Response (Cost Map Part)     |
                |<---------------------------------------|
                |                                        |
                |      PV Response (Property Map Part)  |
                |<---------------------------------------|
                |                                        |

   Figure 3: Information Exchange Process of the base ALTO Protocol and
                         the Path Vector Extension

   The path vector extension, on the other hand, CAN be decomposed to
   two types of information resources.  First, path vectors, which
   represent the correlations of network paths for all <source,
   destination> pairs in the requst, CAN be encoded as an (endpoint)
   cost map with an extended cost type.  Second, properties associated
   with the ANEs CAN be encoded as a property map.

   Instead of making two consecutive queries, however, the path vector
   extension adopts a workflow which also consists of only one round of
   communication, based on the following reasons:

   1.  ANE Computation Flexibility.  For better scalability, flexibility
       and privacy, Abstract Network Elements MAY be constructed on
       demand, and potentially based on the properties (See Section 4.2
       for more details).  If sources and destinations are not in the



Gao, et al.             Expires January 23, 2020               [Page 10]


Internet-Draft         ALTO Extension: Path Vector             July 2019


       same request as the properties, an ALTO server either CANNOT
       construct ANEs on-demand, or MUST wait until both requests are
       received.

   2.  Server Scalability.  As ANEs are constructed on demand, mappings
       of each ANE to its underlying network devices and resources CAN
       be different in different queries.  In order to respond to the
       second request correctly, an ALTO server MUST store the mapping
       of each path vector request until the client fully retrieves the
       property information, which CAN substantially harm the server
       scalability and potentially lead to Denial-of-Service attacks.

   Thus, the path vector extension encapsulates all essential
   information in one request, and returns both path vectors and
   properties associated with the ANEs in a single response.  See
   Section 4.3 for more details.

4.2.  Abstract Network Element

   A key design in the path vector extension is abstract network
   element.  Abstract network elements can be statically generated, for
   example, based on geo-locations, OSPF areas, or simply the raw
   network topology.  They CAN also be generated dynamically, based on a
   client's request.  This on-demand ANE generation allows for better
   scalability, flexibility and privacy enhancement.

   Consider an extreme case where the client only queries the bandwidth
   between one source and one destination in the topology shown in
   Figure 4.  Without knowing in prior the desired property, an ALTO
   server MAY need to include all network components on the paths for
   high accuracy.  However, with the prior knowledge that the client
   only asks for the bandwidth information, an ALTO server CAN either 1)
   selectively pick the link with the smallest available bandwidth, or
   2) dynamically generate a new ANE whose available bandwidth is the
   smallest value of the links' on the path.  Thus, an ALTO server can
   provide accurate information with very little leak of its internal
   network topology.  ANEs MAY also be constructed based on algebraic
   aggregations, please see [TON2019] for more details.

                      +-----+  +-----+       +-----+
                eh1 --| sw1 |--| sw2 |--...--| swN |-- eh2
                      +-----+  +-----+       +-----+

                Figure 4: Topology for Dynamic ANE Example.

   An ANE is uniquely identified by an ANE identifier (see Section 5.1)
   in the same response.  However, since ANEs CAN be generated
   dynamically, an ALTO client MUST NOT assume that ANEs with the same



Gao, et al.             Expires January 23, 2020               [Page 11]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   identifier but from different queries refer to the same aggregation
   of network components.  This approach simplifies the management of
   ANE identifiers at ALTO servers, and increases the difficulty to
   infer the real network topology with cross queries.  It is
   RECOMMENDED that the identifiers of statically generated ANEs be
   anonymized in the path vector response, for example, by shuffling the
   ANEs and shrinking their identifier space to [1, N], where N is the
   number of ANEs etc.

4.3.  Protocol Extensions

   Section 4.1 has well articulated the reasons to complete the
   information exchange in a single round of communication.  This
   section introduces the three major extended components to the base
   ALTO protocol and the Unified Property Map extension, as shown in
   Table 1.

         +------------------------+-------+----------+-----------+
         | Component              | IRD   | Request  | Response  |
         +------------------------+-------+----------+-----------+
         | Path Vector Cost Type  | Yes   | Yes      | Yes       |
         | Property Negotiation   | Yes   | Yes      | Yes       |
         | Multipart Message      | Yes   | No       | Yes       |
         +------------------------+-------+----------+-----------+

            Table 1: Extended Components and Where They Apply.

4.3.1.  Path Vector Cost Type

   Existing cost modes defined in [RFC7285] allow only scalar cost
   values.  However, the path vector extension MUST convey vector format
   information.  To fulfill this requirement, this document defines a
   new cost mode named "array", which indicates that the cost value MUST
   be interpreted as an array of JSONValue.  This document also
   introduces a new cost metric "ane-path" to convey an array of ANE
   identifiers.

   The combination of the "array" cost mode and the "ane-path" cost
   metric also complies best with the ALTO base protocol, where cost
   mode specifies the interpretation of a cost value, and cost metric
   conveys the meaning.

4.3.2.  Property Negotiation

   Similar to cost types, an ALTO server MAY only support a given set of
   ANE properties in a path vector information resource.  Meanwhile, an
   ALTO client MAY only require a subset of the available properties.
   Thus, a property negotiation process is required.



Gao, et al.             Expires January 23, 2020               [Page 12]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   This document uses a similar approach as the negotiation process of
   cost types: the available properties for a given resource are
   announced in the Information Resource Directory and more
   specifically, in a new capability called "ane-properties"; the
   selected properties SHOULD be specified in a new filter called "ane-
   properties" in the request body; the response MUST return and only
   return the selected properties for the ANEs in the response, if
   applicable.

4.3.3.  Multipart/Related Message

   Path vectors and the property map containing the ANEs are two
   different types of objects, but they need to be encoded in one
   message.  One approach is to define a new media type to contain both
   objects, but this violates modular design.

   This document uses standard-conforming usage of "multipart/related"
   media type defined in [RFC2387] to elegantly combine the objects.
   Path vectors are encoded as a cost map or an endpoint cost map, and
   the property map is encoded as a Unified Propert Map. They are
   encapsulated as parts of a multipart message.  The modular
   composition allows ALTO servers and clients to reuse the data models
   of the existing information resources.  Specifically, this document
   addresses the following practical issues using "multipart/related".

4.3.3.1.  Identifying the Media Type of the Root Object

   ALTO uses media type to indicate the type of an entry in the
   Information Resource Directory (IRD) (e.g., "application/alto-
   costmap+json" for cost map and "application/alto-endpointcost+json"
   for endpoint cost map).  Simply putting "multipart/related" as the
   media type, however, makes it impossible for an ALTO client to
   identify the type of service provided by related entries.

   To address this issue, this document uses the "type" parameter to
   indicate the root object of a multipart/related message.  For a cost
   map resource, the "media-type" in the IRD entry MUST be "multipart/
   related" with the parameter "type=application/alto-costmap+json"; for
   an Endpoint Cost Service, the parameter MUST be "type=application/
   alto-endpointcost+json".

4.3.3.2.  References to Part Messages

   The ALTO SSE extension (see [I-D.ietf-alto-incr-update-sse]) uses
   "client-id" to demultiplex push updates.  However, "client-id" is
   provided for each request, which introduces ambiguity when applying
   SSE to a path vector resource.




Gao, et al.             Expires January 23, 2020               [Page 13]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   To address this issue, an ALTO server MUST assign a unique identifier
   to each part of the "multipart/related" response message.  This
   identifier, referred to as a Part Resource ID (See Section 5.6 for
   details), MUST be present in the part message's "Resource-Id" header.
   The MIME part header MUST also contain the "Content-Type" header,
   whose value is the media type of the part (e.g., "application/alto-
   costmap+json", "application/alto-endpointcost+json", or "application/
   alto-propmap+json").

   If an ALTO server provides incremental updates for this path vector
   resource, it MUST generate incremental updates for each part
   separately.  The client-id MUST have the following format:

      pv-client-id '.' part-resource-id

   where pv-client-id is the client-id assigned to the path vector
   request, and part-resource-id is the "Resource-Id" header value of
   the part.  The media-type MUST match the "Content-Type" of the part.

   The same problem happens inside the part messages as well.  The two
   parts MUST contain a version tag, which SHOULD contain a unique
   Resource ID.  This document requires the resource-id in a Version Tag
   to have the following format:

      pv-resource-id '.' part-resource-id

   where pv-resource-id is the resource ID of the path vector resource
   in the IRD entry, and the part-resource-id has the same value as the
   "Resource-Id" header of the part.

4.3.3.3.  Order of Part Messages

   According to RFC 2387 [RFC2387], the path vector part, whose media
   type is the same as the "type" parameter of the multipart response
   message, is the root object.  Thus, it is the element the application
   processes first.  Even though the "start" parameter allows it to be
   placed anywhere in the part sequence, it is RECOMMENDED that the
   parts arrive in the same order as they are processed, i.e., the path
   vector part is always put as the first part, followed by the property
   map part.  It is also RECOMMENDED that when doing so, an ALTO server
   SHOULD NOT set the "start" parameter, which implies the first part is
   the root object.

5.  Basic Data Types







Gao, et al.             Expires January 23, 2020               [Page 14]


Internet-Draft         ALTO Extension: Path Vector             July 2019


5.1.  ANE Identifier

   An ANE identifier is encoded as a JSON string.  The string MUST be no
   more than 64 characters, and it MUST NOT contain characters other
   than US-ASCII alphanumeric characters (U+0030-U+0039, U+0041-U+005A,
   and U+0061-U+007A), the hyphen ("-", U+002D), the colon (":",
   U+003A), the at sign ("@", code point U+0040), the low line ("_",
   U+005F), or the "." separator (U+002E).  The "." separator is
   reserved for future use and MUST NOT be used unless specifically
   indicated in this document, or an extension document.

   The type ANEIdentifier is used in this document to indicate a string
   of this format.

5.2.  Path Vector Cost Type

   This document defines a new cost type, which is referred to as the
   "path vector" cost type.  An ALTO server MUST offer this cost type if
   it supports the path vector extension.

5.2.1.  Cost Metric: ane-path

   This cost metric conveys an array of ANE identifiers, where each
   identifier uniquely represents an ANE traversed by traffic from a
   source to a destination.

5.2.2.  Cost Mode: array

   This cost mode indicates that every cost value in a cost map or an
   endpoint cost map MUST be interpreted as a JSON array object.

   Note that this cost mode only requires the cost value to be a JSON
   array of JSONValue.  However, an ALTO server that enables this
   extension MUST return a JSON array of ANEIdentifier (Section 5.1)
   when the cost metric is "ane-path".

5.3.  ANE Domain

   This document specifies a new ALTO entity domain called "ane" in
   addition to the ones in [I-D.ietf-alto-unified-props-new].  The ANE
   domain associates property values with the ANEs in a network.  The
   entity in ANE domain is often used in the path vector by cost maps or
   endpoint cost resources.  Accordingly, the ANE domain always depends
   on a cost map or an endpoint cost map.







Gao, et al.             Expires January 23, 2020               [Page 15]


Internet-Draft         ALTO Extension: Path Vector             July 2019


5.3.1.  Entity Domain Type

   ane

5.3.2.  Domain-Specific Entity Identifier

   The entity identifier of ANE domain uses the same encoding as
   ANEIdentifier (Section 5.1).

5.3.3.  Hierarchy and Inheritance

   There is no hierarchy or inheritance for properties associated with
   ANEs.

5.4.  New Resource-Specific Entity Domain Exports

5.4.1.  ANE Domain of Cost Map Resource

   If an ALTO cost map resource supports "ane-path" cost metric, it can
   export an "ane" typed entity domain defined by the union of all sets
   of ANE names, where each set of ANE names are an "ane-path" metric
   cost value in this ALTO cost map resource.

5.4.2.  ANE Domain of Endpoint Cost Resource

   If an ALTO endpoint cost resource supports "ane-path" cost metric, it
   can export an "ane" typed entity domain defined by the union of all
   sets of ANE names, where each set of ANE names are an "ane-path"
   metric cost value in this ALTO endpoint cost resource.

5.5.  ANE Properties

5.5.1.  ANE Property: Maximum Reservable Bandwidth

   The maximum reservable bandwidth property conveys the maximum
   bandwidth that can be reserved for traffic from a source to a
   destination and is indicated by the property name "maxresbw".  The
   value MUST be encoded as a numerical cost value as defined in
   Section 6.1.2.1 of [RFC7285] and the unit is bit per second.

   If this property is requested but is missing for a given ANE, it MUST
   be interpreted as that the ANE does not support bandwidth reservation
   but have sufficiently large bandwidth for all traffic that traverses
   it.







Gao, et al.             Expires January 23, 2020               [Page 16]


Internet-Draft         ALTO Extension: Path Vector             July 2019


5.5.2.  ANE Property: Persistent Entity

   The persistent entity property conveys the physical or logical
   network entities (e.g., links, in-network caching service) that are
   contained by an abstract network element.  It is indicated by the
   property name "persistent-entity".  The value is encoded as a JSON
   array of entity identifiers ([I-D.ietf-alto-unified-props-new]).
   These entity identifiers are persistent so that a client CAN further
   query their properties for future use.

   If this property is requested but is missing for a given ANE, it MUST
   be interpreted as that no such entities exist in this ANE.

5.6.  Part Resource ID

   A Part Resource ID is encoded as a JSON string with the same format
   as that of the Resource ID (Section 10.2 of [RFC7285]).

   WARNING: Even though the client-id assigned to a path vector request
   and the Part Resource ID MAY contain up to 64 characters by their own
   definition.  Their concatenation (see Section 4.3.3.2) MUST also
   conform to the same length constraint.  The same requirement applies
   to the resource ID of the path vector resource, too.  Thus, it is
   RECOMMENDED to limit the length of resource ID and client ID related
   to a path vector resource to 31 characters.

6.  Service Extensions

6.1.  Multipart Filtered Cost Map for Path Vector

   This document introduces a new ALTO resource called multipart
   filtered cost map resource, which allows an ALTO server to provide
   other ALTO resources associated to the cost map resource in the same
   response.

6.1.1.  Media Type

   The media type of the multipart filtered cost map resource is
   "multipart/related;type=application/alto-costmap+json".

6.1.2.  HTTP Method

   The multipart filtered cost map is requested using the HTTP POST
   method.







Gao, et al.             Expires January 23, 2020               [Page 17]


Internet-Draft         ALTO Extension: Path Vector             July 2019


6.1.3.  Accept Input Parameters

   The input parameters of the multipart filtered cost map are supplied
   in the body of an HTTP POST request.  This document extends the input
   parameters to a filtered cost map with a data format indicated by the
   media type "application/alto-costmapfilter+json", which is a JSON
   object of type PVReqFilteredCostMap, where:

   object {
     [PropertyName ane-properties<0..*>;]
   } PVReqFilteredCostMap : ReqFilteredCostMap;

   with fields:

   ane-properties:  A list of properties that are associated with the
      ANEs.  Each property in this list MUST match one of the supported
      ANE properties indicated in the resource's "ane-properties"
      capability.  If the field is NOT present, it MUST be interpreted
      as an empty list, indicating that the ALTO server MUST NOT return
      any property in the unified property part.

6.1.4.  Capabilities

   The multipart filtered cost map resource extends the capabilities
   defined in Section 11.3.2.4 of [RFC7285].  The capabilities are
   defined by a JSON object of type PVFilteredCostMapCapabilities:

   object {
     [PropertyName ane-properties<0..*>;]
   } PVFilteredCostMapCapabilities : FilteredCostMapCapabilities;

   with fields:

   cost-type-names:  The "cost-type-names" field MUST only include the
      path vector cost type, unless explicitly documented by a future
      extension.  This also implies that the path vector cost type MUST
      be defined in the "cost-types" of the Information Resource
      Directory's "meta" field.

   ane-properties:  Defines a list of ANE properties that can be
      returned.  If the field is NOT present, it MUST be interpreted as
      an empty list, indicating the ALTO server CANNOT provide any ANE
      property.








Gao, et al.             Expires January 23, 2020               [Page 18]


Internet-Draft         ALTO Extension: Path Vector             July 2019


6.1.5.  Uses

   The resource ID of the network map based on which the PIDs in the
   returned cost map will be defined.  If this resource supports
   "persistent-entities", it MUST also include ALL the resources that
   exposes the entities that MAY appear in the response.

6.1.6.  Response

   The response MUST indicate an error, using ALTO protocol error
   handling, as defined in Section 8.5 of [RFC7285], if the request is
   invalid.

   The "Content-Type" header of the response MUST be "multipart/related"
   as defined by [RFC2387] with the following parameters:

   type:  The type parameter MUST be "application/alto-costmap+json".
      Note that [RFC2387] permits both parameters with and without the
      double quotes.

   start:  The start parameter MUST be a quoted string where the quoted
      part has the same value as the "Resource-ID" header in the first
      part.

   boundary:  The boundary parameter is as defined in [RFC2387].

   The body of the response consists of two parts.

   The first part MUST include "Resource-Id" and "Content-Type" in its
   header.  The value of "Resource-Id" MUST has the format of a Part
   Resource ID.  The "Content-Type" MUST be "application/alto-
   costmap+json".

   The body of the first part MUST be a JSON object with the same format
   as defined in Section 11.2.3.6 of [RFC7285].  The JSON object MUST
   include the "vtag" field in the "meta" field, which provides the
   version tag of the returned cost map.  The resource ID of the version
   tag MUST follow the format in Section 4.3.3.2.  The "meta" field MUST
   also include the "dependent-vtags" field, whose value is a single-
   element array to indicate the version tag of the network map used,
   where the network map is specified in the "uses" attribute of the
   multipart filtered cost map resource in IRD.

   The second part MUST also include "Resource-Id" and "Content-Type" in
   its header.  The value of "Resource-Id" has the format of a Part
   Resource ID.  The "Content-Type" MUST be "application/alto-
   propmap+json".




Gao, et al.             Expires January 23, 2020               [Page 19]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   The body of the second part MUST be a JSON object with the same
   format as defined in Section 4.6 of
   [I-D.ietf-alto-unified-props-new].  The JSON object MUST include the
   "dependent-vtags" field in the "meta" field.  The value of the
   "dependent-vtags" field MUST be an array of VersionTag objects as
   defined by Section 10.3 of [RFC7285].  The "vtag" of the first part
   MUST be included in the "dependent-vtags".  If "persistent-entities"
   is requested, the version tags of the dependent resources that MAY
   expose the entities in the response MUST also be included.  The
   PropertyMapData has one member for each ANE identifier that appears
   in the first part, where the EntityProps has one member for each
   property requested by the client if applicable.

6.2.  Multipart Endpoint Cost Service for Path Vector

   This document introduces a new ALTO resource called multipart
   endpoint cost resource, which allows an ALTO server to provide other
   ALTO resources associated to the endpoint cost resource in the same
   response.

6.2.1.  Media Type

   The media type of the multipart endpoint cost resource is
   "multipart/related;type=application/alto-endpointcost+json".

6.2.2.  HTTP Method

   The multipart endpoint cost resource is requested using the HTTP POST
   method.

6.2.3.  Accept Input Parameters

   The input parameters of the multipart endpoint cost resource are
   supplied in the body of an HTTP POST request.  This document extends
   the input parameters to an endpoint cost map with a data format
   indicated by the media type "application/alto-
   endpointcostparams+json", which is a JSON object of type
   PVEndpointCostParams, where

   object {
     [PropertyName ane-properties<0..*>;]
   } PVReqEndpointcost : ReqEndpointcost;

   with fields:

   ane-properties:  This document defines the "ane-properties" in
      PVReqEndpointcost as the same as in PVReqFilteredCostMap.  See
      Section 6.1.3.



Gao, et al.             Expires January 23, 2020               [Page 20]


Internet-Draft         ALTO Extension: Path Vector             July 2019


6.2.4.  Capabilities

   The capabilities of the multipart endpoint cost resource are defined
   by a JSON object of type PVEndpointcostCapabilities, which is defined
   as the same as PVFilteredCostMapCapabilities.  See Section 6.1.4.

6.2.5.  Uses

   If a multipart endpoint cost resource supports "persistent-entities",
   the "uses" field in its IRD entry MUST include ALL the resources
   which exposes the entities that MAY appear in the response.

6.2.6.  Response

   The response MUST indicate an error, using ALTO protocol error
   handling, as defined in Section 8.5 of [RFC7285], if the request is
   invalid.

   The "Content-Type" header of the response MUST be "multipart/related"
   as defined by [RFC2387] with the following parameters:

   type:  The type parameter MUST be "application/alto-
      endpointcost+json".

   start:  The start parameter MUST be a quoted string where the quoted
      part has the same value as the "Resource-ID" header in the first
      part.

   boundary:  The boundary parameter is as defined in [RFC2387].

   The body consists of two parts:

   The first part MUST include "Resource-Id" and "Content-Type" in its
   header.  The value of "Resource-Id" MUST has the format of a Part
   Resource ID.  The "Content-Type" MUST be "application/alto-
   endpointcost+json".

   The body of the first part MUST be a JSON object with the same format
   as defined in Section 11.5.1.6 of [RFC7285].  The JSON object MUST
   include the "vtag" field in the "meta" field, which provides the
   version tag of the returned endpoint cost map.  The resource ID of
   the version tag MUST follow the format in Section 4.3.3.2.

   The second part MUST also include "Resource-Id" and "Content-Type" in
   its header.  The value of "Resource-Id" MUST has the format of a Part
   Resource ID.  The "Content-Type" MUST be "application/alto-
   propmap+json".




Gao, et al.             Expires January 23, 2020               [Page 21]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   The body of the second part MUST be a JSON object with the same
   format as defined in Section 4.6 of
   [I-D.ietf-alto-unified-props-new].  The JSON object MUST include the
   "dependent-vtags" field in the "meta" field.  The value of the
   "dependent-vtags" field MUST be an array of VersionTag objects as
   defined by Section 10.3 of [RFC7285].  The "vtag" of the first part
   MUST be included in the "dependent-vtags".  If "persistent-entities"
   is requested, the version tags of the dependent resources that MAY
   expose the entities in the response MUST also be included.  The
   PropertyMapData has one member for each ANE identifier that appears
   in the first part, where the EntityProps has one member for each
   property requested by the client if applicable.

7.  Examples

   This section lists some examples of path vector queries and the
   corresponding responses.  Some long lines are truncated for better
   readability.

7.1.  Example: Information Resource Directory

   Below is an example of an Information Resource Directory which
   enables the path vector extension.  Some critical modifications
   include:

   o  The "path-vector" cost type (Section 5.2) is defined in the "cost-
      types" of the "meta" field.

   o  The "cost-map-pv" information resource provides a multipart
      filtered cost map resource, which exposes the Maximum Reservable
      Bandwidth ("maxresbw") property.

   o  The "http-proxy-props" information resource provides a filtered
      unified property map resource, which exposes the HTTP proxy entity
      domain (encoded as "http-proxy") and the "price" property.  Note
      that HTTP proxy is NOT a valid entity domain yet and is used here
      only for demonstration.

   o  The "endpoint-cost-pv" information resource provides a multipart
      endpoint cost resource.  It exposes the Maximum Reservable
      Bandwidth ("maxresbw") property and the Persistent Entity property
      ("persistent-entities").  The persistent entities MAY come from
      the "http-proxy-props" resource.

   o  The "update-pv" information resource provides the incremental
      update ([I-D.ietf-alto-incr-update-sse]) service for the
      "endpoint-cost-pv" resource.




Gao, et al.             Expires January 23, 2020               [Page 22]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   {
     "meta": {
       "cost-types": {
         "path-vector": {
           "cost-mode": "array",
           "cost-metric": "ane-path"
         }
       }
     },
     "resources": {
       "my-default-networkmap": {
         "uri" : "http://alto.example.com/networkmap",
         "media-type" : "application/alto-networkmap+json"
       },
       "cost-map-pv": {
         "uri": "http://alto.example.com/costmap/pv",
         "media-type": "multipart/related;
                        type=application/alto-costmap+json",
         "accepts": "application/alto-costmapfilter+json",
         "capabilities": {
           "cost-type-names": [ "path-vector" ],
           "ane-properties": [ "maxresbw" ]
         },
         "uses": [ "my-default-networkmap" ]
       },
       "http-proxy-props": {
         "uri": "http://alto.example.com/proxy-props",
         "media-type": "application/alto-propmap+json",
         "accpets": "application/alto-propmapparams+json",
         "capabilities": {
           "mappings": {
             "http-proxy": [ "price" ]
           }
         }
       },
       "endpoint-cost-pv": {
         "uri": "http://alto.exmaple.com/endpointcost/pv",
         "media-type": "multipart/related;
                        type=application/alto-endpointcost+json",
         "accepts": "application/alto-endpointcostparams+json",
         "capabilities": {
           "cost-type-names": [ "path-vector" ],
           "ane-properties": [ "maxresbw", "persistent-entities" ]
         },
         "uses": [ "http-proxy-props" ]
       },
       "update-pv": {
         "uri": "http://alto.example.com/updates/pv",



Gao, et al.             Expires January 23, 2020               [Page 23]


Internet-Draft         ALTO Extension: Path Vector             July 2019


         "media-type": "text/event-stream",
         "uses": [ "endpoint-cost-pv" ],
         "accepts": "application/alto-updatestreamparams+json",
         "capabilities": {
           "support-stream-control": true
         }
       }
     }
   }

7.2.  Example: Multipart Filtered Cost Map

   The following examples demonstrate the request to the "cost-map-pv"
   resource and the corresponding response.

   The request uses the path vector cost type in the "cost-type" field.
   The "ane-properties" field is missing, indicating that the client
   only requests for the path vector but not the ANE properties.

   The response consists of two parts.  The first part returns the array
   of ANE identifiers for each source and destination pair.  There are
   three ANEs, where "ane:L001" is shared by traffic from "PID1" to both
   "PID2" and "PID3".

   The second part returns an empty property map.  Note that the ANE
   entries are omitted since they have no properties (See Section 3.1 of
   [I-D.ietf-alto-unified-props-new]).

   POST /costmap/pv HTTP/1.1
   Host: alto.example.com
   Accept: multipart/related;type=application/alto-costmap+json,
           application/alto-error+json
   Content-Length: [TBD]
   Content-Type: application/alto-costmapfilter+json

   {
     "cost-type": {
       "cost-mode": "array",
       "cost-metric": "ane-path"
     },
     "pids": {
       "srcs": [ "PID1" ],
       "dsts": [ "PID2", "PID3" ]
     }
   }

   HTTP/1.1 200 OK
   Content-Length: [TBD]



Gao, et al.             Expires January 23, 2020               [Page 24]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   Content-Type: multipart/related; boundary=example-1;
                 type=application/alto-costmap+json

   --example-1
   Resource-Id: costmap
   Content-Type: application/alto-costmap+json

   {
     "meta": {
       "vtag": {
         "resource-id": "cost-map-pv.costmap",
         "tag": "d827f484cb66ce6df6b5077cb8562b0a"
       },
       "dependent-vtags": [
         {
           "resource-id": "my-default-networkmap",
           "tag": "75ed013b3cb58f896e839582504f6228"
         }
       ],
       "cost-type": {
         "cost-mode": "array",
         "cost-metric": "ane-path"
       }
     },
     "cost-map": {
       "PID1": {
         "PID2": [ "ane:L001", "ane:L003" ],
         "PID3": [ "ane:L001", "ane:L004" ]
       }
     }
   }
   --example-1
   Resource-Id: propmap
   Content-Type: application/alto-propmap+json

   {
     "meta": {
       "dependent-vtags": [
         {
           "resource-id": "cost-map-pv.costmap",
           "tag": "d827f484cb66ce6df6b5077cb8562b0a"
         }
       ]
     },
     "property-map": {
     }
   }




Gao, et al.             Expires January 23, 2020               [Page 25]


Internet-Draft         ALTO Extension: Path Vector             July 2019


7.3.  Example: Multipart Endpoint Cost Resource

   The following examples demonstrate the request to the "endpoint-cost-
   pv" resource and the corresponding response.

   The request uses the path vector cost type in the "cost-type" field,
   and queries the Maximum Reservable Bandwidth ANE property and the
   Persistent Entity property.

   The response consists of two parts.  The first part returns the array
   of ANE identifiers for each valid source and destination pair.

   The second part returns the requested properties of ANEs in the first
   part.  The "ane:NET001" element contains an HTTP proxy entity, which
   can be further used by the client.  Since it does not contain a
   "maxresbw" property, the client SHOULD assume it does NOT support
   bandwidth reservation but will NOT become a traffic bottleneck, as
   specified in Section 5.5.1.

   POST /endpointcost/pv HTTP/1.1
   Host: alto.example.com
   Accept: multipart/related;
           type=application/alto-endpointcost+json,
           application/alto-error+json
   Content-Length: [TBD]
   Content-Type: application/alto-endpointcostparams+json

   {
     "cost-type": {
       "cost-mode": "array",
       "cost-metric": "ane-path"
     },
     "endpoints": {
       "srcs": [ "ipv4:192.0.2.2" ],
       "dsts": [ "ipv4:192.0.2.89",
                 "ipv4:203.0.113.45",
                 "ipv6:2001:db8::10" ]
     },
     "ane-properties": [ "maxresbw", "persistent-entities" ]
   }

   HTTP/1.1 200 OK
   Content-Length: [TBD]
   Content-Type: multipart/related; boundary=example-2;
                 type=application/alto-endpointcost+json

   --example-2
   Resource-Id: ecs



Gao, et al.             Expires January 23, 2020               [Page 26]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   Content-Type: application/alto-endpointcost+json

   {
     "meta": {
       "vtags": {
         "resource-id": "endpoint-cost-pv.ecs",
         "tag": "bb6bb72eafe8f9bdc4f335c7ed3b10822a391cef"
       },
       "cost-type": {
         "cost-mode": "array",
         "cost-metric": "ane-path"
       }
     },
     "endpoint-cost-map": {
       "ipv4:192.0.2.2": {
         "ipv4:192.0.2.89":   [ "ane:NET001", "ane:L002" ],
         "ipv4:203.0.113.45": [ "ane:NET001", "ane:L003" ]
       }
     }
   }
   --example-2
   Resource-Id: propmap
   Content-Type: application/alto-propmap+json

   {
     "meta": {
       "dependent-vtags": [
         {
           "resource-id": "endpoint-cost-pv.ecs",
           "tag": "bb6bb72eafe8f9bdc4f335c7ed3b10822a391cef"
         },
         {
           "resource-id": "http-proxy-props",
           "tag": "bf3c8c1819d2421c9a95a9d02af557a3"
         }
       ]
     },
     "property-map": {
       "ane:NET001": {
         "persistent-entities": [ "http-proxy:192.0.2.1" ]
       },
       "ane:L002": { "maxresbw": 48000000 },
       "ane:L003": { "maxresbw": 35000000 }
     }
   }






Gao, et al.             Expires January 23, 2020               [Page 27]


Internet-Draft         ALTO Extension: Path Vector             July 2019


7.4.  Example: Incremental Updates

   In this example, an ALTO client subscribes to the incremental update
   for the multipart endpoint cost resource "endpoint-cost-pv".

   POST /updates/pv HTTP/1.1
   Host: alto.example.com
   Accept: text/event-stream
   Content-Type: application/alto-updatestreamparams+json
   Content-Length: [TBD]

   {
     "add": {
       "ecspvsub1": {
         "resource-id": "endpoint-cost-pv",
         "input": <ecs-input>
       }
     }
   }

   Based on the server-side process defined in
   [I-D.ietf-alto-incr-update-sse], the ALTO server will send the
   "control-uri" first using Server-Sent Event (SSE), followed by the
   full response of the multipart message.

   HTTP/1.1 200 OK
   Connection: keep-alive
   Content-Type: text/event-stream

   event: application/alto-updatestreamcontrol+json
   data: {"control-uri": "http://alto.example.com/updates/streams/1414"}

   event: multipart/related;boundary=example-3;
          type=application/alto-endpointcost+json,ecspvsub1
   data: --example-3
   data: Resource-ID: ecsmap
   data: Content-Type: application/alto-endpointcost+json
   data:
   data: <endpoint-cost-map-entry>
   data: --example-3
   data: Resource-ID: propmap
   data: Content-Type: application/alto-propmap+json
   data:
   data: <property-map-entry>
   data: --example-3--

   When the contents change, the ALTO server will publish the updates
   for each node in this tree separately.



Gao, et al.             Expires January 23, 2020               [Page 28]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   event: application/merge-patch+json, ecspvsub1.ecsmap
   data: <Merge patch for endpoint-cost-map-update>

   event: application/merge-patch+json, ecspvsub1.propmap
   data: <Merge patch for property-map-update>

8.  Compatibility

8.1.  Compatibility with Legacy ALTO Clients/Servers

   The multipart filtered cost map resource and the multipart endpoint
   cost resource has no backward compatibility issue with legacy ALTO
   clients and servers.  Although these two types of resources reuse the
   media types defined in the base ALTO protocol for the accept input
   parameters, they have different media types for responses.  If the
   ALTO server provides these two types of resources, but the ALTO
   client does not support them, the ALTO client will ignore the
   resources without conducting any incompatibility.

8.2.  Compatibility with Multi-Cost Extension

   This document does not specify how to integrate the "path-vector"
   cost mode with the multi-cost extension [RFC8189].  Although there is
   no reason why somebody has to compound the path vectors with other
   cost types in a single query, there is no compatible issue doing it
   without constraint tests.

8.3.  Compatibility with Incremental Update

   The extension specified in this document is NOT compatible with the
   original incremental update extension
   [I-D.ietf-alto-incr-update-sse].  A legacy ALTO client CANNOT
   recognize the compound client-id, and a legacy ALTO server MAY use
   the same client-id for updates of both parts.

   ALTO clients and servers MUST follow the specifications given in this
   document to ensure compatibility with the incremental update
   extension.

8.4.  Compatibility with Cost Calendar

   The extension specified in this document is compatible with the Cost
   Calendar extension [I-D.ietf-alto-cost-calendar].  When used together
   with the Cost Calendar extension, the cost value between a source and
   a destination is an array of path vectors, where the k-th path vector
   refers to the abstract network paths traversed in the k-th time
   interval by traffic from the source to the destination.




Gao, et al.             Expires January 23, 2020               [Page 29]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   When used with time-varying properties, e.g., maximum reservable
   bandwidth (maxresbw), a property of a single entity may also have
   different values in different time intervals.  In this case, an ANE
   with different property values MUST be considered as different ANEs.

   The two extensions combined together CAN provide the historical
   network correlation information for a set of source and destination
   pairs.  A network broker or client MAY use this information to derive
   other resource requirements such as Time-Block-Maximum Bandwidth,
   Bandwidth-Sliding-Window, and Time-Bandwidth-Product (TBP) (See
   [SENSE] for details.)

9.  General Discussions

9.1.  Provide Calendar for Property Map

   Fetching the historical network information is useful for many
   traffic optimization problem.  [I-D.ietf-alto-cost-calendar] already
   proposes an ALTO extension called Cost Calendar which provides the
   historical cost values using filtered cost map and endpoint cost
   service.  However, the calendar for only path costs is not enough.

   For example, as the properties of ANEs (e.g., available bandwidth and
   link delay) are usually the real-time network states, they change
   frequently in the real network.  It is very helpful to get the
   historical value of these properties.  Applications may predicate the
   network status using these information to better optimize their
   performance.

   So the coming requirement may be a general calendar service for the
   ALTO information resources.

9.2.  Constraint Tests for General Cost Types

   The constraint test is a simple approach to query the data.  It
   allows users to filter the query result by specifying some boolean
   tests.  This approach is already used in the ALTO protocol.
   [RFC7285] and [RFC8189] allow ALTO clients to specify the
   "constraints" and "or-constraints" tests to better filter the result.

   However, the current defined syntax is too simple and can only be
   used to test the scalar cost value.  For more complex cost types,
   like the "array" mode defined in this document, it does not work
   well.  It will be helpful to propose more general constraint tests to
   better perform the query.

   In practice, it is too complex to customize a language for the
   general-purpose boolean tests, and can be a duplicated work.  So it



Gao, et al.             Expires January 23, 2020               [Page 30]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   may be a good idea to integrate some already defined and widely used
   query languages (or their subset) to solve this problem.  The
   candidates can be XQuery and JSONiq.

9.3.  General Multipart Resources Query

   Querying multiple ALTO information resources continuously MAY be a
   general requirement.  And the coming issues like inefficiency and
   inconsistency are also general.  There is no standard solving these
   issues yet.  So we need some approach to make the ALTO client request
   the compound ALTO information resources in a single query.

10.  Security Considerations

   This document is an extension of the base ALTO protocol, so the
   Security Considerations [RFC7285] of the base ALTO protocol fully
   apply when this extension is provided by an ALTO server.

   The path vector extension requires additional considerations on two
   security considerations discussed in the base protocol:
   confidentiality of ALTO information (Section 15.3 of [RFC7285]) and
   availability of ALTO service (Section 15.5 of [RFC7285]).

   For confidentiality of ALTO information, a network operator should be
   aware of that this extension may introduce a new risk: the path
   vector information may make network attacks easier.  For example, as
   the path vector information may reveal more network internal
   structures than the base protocol, an ALTO client may detect the
   bottleneck link and start a distributed denial-of-service (DDoS)
   attack involving minimal flows to conduct the in-network congestion.

   To mitigate this risk, the ALTO server should consider protection
   mechanisms to reduce information exposure or obfuscate the real
   information, in particular, in settings where the network and the
   application do not belong to the same trust domain.  But the
   implementation of path vector extension involving reduction or
   obfuscation should guarantees the constraints on the requested
   properties are still accurate.

   For availability of ALTO service, an ALTO server should be cognizant
   that using path vector extension might have a new risk: frequent
   requesting for path vectors might conduct intolerable increment of
   the server-side storage and break the ALTO server.  It is known that
   the computation of path vectors is unlikely to be cacheable, in that
   the results will depend on the particular requests (e.g., where the
   flows are distributed).  Hence, the service providing path vectors
   may become an entry point for denial-of-service attacks on the




Gao, et al.             Expires January 23, 2020               [Page 31]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   availability of an ALTO server.  To avoid this risk, authenticity and
   authorization of this ALTO service may need to be better protected.

11.  IANA Considerations

11.1.  ALTO Cost Mode Registry

   This document specifies a new cost mode "path-vector".  However, the
   base ALTO protocol does not have a Cost Mode Registry where new cost
   mode can be registered.  This new cost mode will be registered once
   the registry is defined either in a revised version of [RFC7285] or
   in another future extension.

11.2.  ALTO Entity Domain Registry

   As proposed in Section 9.2 of [I-D.ietf-alto-unified-props-new],
   "ALTO Domain Entity Registry" is requested.  Besides, a new domain is
   to be registered, listed in Table 2.

   +-------------+--------------------------+--------------------------+
   | Identifier  | Entity Address Encoding  | Hierarchy & Inheritance  |
   +-------------+--------------------------+--------------------------+
   | ane         | See Section 5.3.2        | None                     |
   +-------------+--------------------------+--------------------------+

                        Table 2: ALTO Entity Domain

11.3.  ALTO Entity Property Type Registry

   The "ALTO Entity Property Type Registry" is required by the ALTO
   Domain "ane", listed in Table 3.

   +-------------------------+-----------------------------------------+
   | Identifier              | Intended Semantics                      |
   +-------------------------+-----------------------------------------+
   | ane:maxresbw            | The maximum reservable bandwidth for    |
   |                         | the ANE                                 |
   | ane:persistent-entities | An array of identifiers of persistent   |
   |                         | entities that reside in an ANE          |
   +-------------------------+-----------------------------------------+

                    Table 3: ALTO Entity Property Types

11.4.  ALTO Resource Entity Domain Export Registries







Gao, et al.             Expires January 23, 2020               [Page 32]


Internet-Draft         ALTO Extension: Path Vector             July 2019


11.4.1.  costmap

               +---------------------+--------------------+
               | Entity Domain Type  | Export Function    |
               +---------------------+--------------------+
               | ane                 | See Section 5.4.1  |
               +---------------------+--------------------+

               Table 4: ALTO Cost Map Entity Domain Export.

11.4.2.  endpointcost

               +---------------------+--------------------+
               | Entity Domain Type  | Export Function    |
               +---------------------+--------------------+
               | ane                 | See Section 5.4.2  |
               +---------------------+--------------------+

             Table 5: ALTO Endpoint Cost Entity Domain Export.

12.  Acknowledgments

   The authors would like to thank discussions with Andreas Voellmy,
   Erran Li, Haibin Song, Haizhou Du, Jiayuan Hu, Qiao Xiang, Tianyuan
   Liu, Xiao Shi, Xin Wang, and Yan Luo. The authors thank Greg
   Bernstein (Grotto Networks), Dawn Chen (Tongji University), Wendy
   Roome, and Michael Scharf for their contributions to earlier drafts.

13.  References

13.1.  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, <https://www.rfc-
              editor.org/info/rfc2119>.

   [RFC2387]  Levinson, E., "The MIME Multipart/Related Content-type",
              RFC 2387, DOI 10.17487/RFC2387, August 1998,
              <https://www.rfc-editor.org/info/rfc2387>.

   [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,
              <https://www.rfc-editor.org/info/rfc7285>.





Gao, et al.             Expires January 23, 2020               [Page 33]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   [RFC8189]  Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost
              Application-Layer Traffic Optimization (ALTO)", RFC 8189,
              DOI 10.17487/RFC8189, October 2017, <https://www.rfc-
              editor.org/info/rfc8189>.

13.2.  Informative References

   [I-D.bernstein-alto-topo]
              Bernstein, G., Yang, Y., and Y. Lee, "ALTO Topology
              Service: Uses Cases, Requirements, and Framework", draft-
              bernstein-alto-topo-00 (work in progress), October 2013.

   [I-D.ietf-alto-cost-calendar]
              Randriamasy, S., Yang, Y., Wu, Q., Lingli, D., and N.
              Schwan, "ALTO Cost Calendar", draft-ietf-alto-cost-
              calendar-01 (work in progress), February 2017.

   [I-D.ietf-alto-incr-update-sse]
              Roome, W. and Y. Yang, "ALTO Incremental Updates Using
              Server-Sent Events (SSE)", draft-ietf-alto-incr-update-
              sse-16 (work in progress), March 2019.

   [I-D.ietf-alto-performance-metrics]
              Wu, Q., Yang, Y., Lee, Y., Dhody, D., and S. Randriamasy,
              "ALTO Performance Cost Metrics", draft-ietf-alto-
              performance-metrics-06 (work in progress), November 2018.

   [I-D.ietf-alto-unified-props-new]
              Roome, W., Randriamasy, S., Yang, Y., and J. Zhang,
              "Unified Properties for the ALTO Protocol", draft-ietf-
              alto-unified-props-new-07 (work in progress), March 2019.

   [SENSE]    "Services - SENSE", 2019, <http://sense.es.net/services>.

   [TON2019]  Gao, K., Xiang, Q., Wang, X., Yang, Y., and J. Bi, "An
              objective-driven on-demand network abstraction for
              adaptive applications", IEEE/ACM Transactions on
              Networking (TON) 27, no. 2 (2019): 805-818., 2019.

Authors' Addresses

   Kai Gao
   Sichuan University
   Chengdu  610000
   China

   Email: kaigao@scu.edu.cn




Gao, et al.             Expires January 23, 2020               [Page 34]


Internet-Draft         ALTO Extension: Path Vector             July 2019


   Young Lee
   Huawei
   TX
   USA

   Email: leeyoung@huawei.com


   Sabine Randriamasy
   Nokia Bell Labs
   Route de Villejust
   NOZAY  91460
   FRANCE

   Email: Sabine.Randriamasy@nokia-bell-labs.com


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

   Email: yry@cs.yale.edu


   Jingxuan Jensen Zhang
   Tongji University
   4800 Caoan Road
   Shanghai  201804
   China

   Email: jingxuan.n.zhang@gmail.com


















Gao, et al.             Expires January 23, 2020               [Page 35]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/