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ALTO WG                                                         J. Zhang
Internet-Draft                                         Tongji University
Intended status: Standards Track                                  K. Gao
Expires: September 6, 2018                           Tsinghua University
                                                                 J. Wang
                                                       Tongji University
                                                                Q. Xiang
                                                  Tongji/Yale University
                                                                 Y. Yang
                                                         Yale University
                                                           March 5, 2018


                 ALTO Extension: Flow-based Cost Query
                       draft-gao-alto-fcs-05.txt

Abstract

   ALTO cost maps and endpoint cost services map a source-destination
   pair into a cost value.  However, current filter specifications,
   which define the set of source-destination pairs in an ALTO query,
   have two limitations: 1) Only very limited address types are
   supported (IPv4 and IPv6), which is not sufficient to uniquely
   identify a flow in networks with fine-grained routing, such as the
   emerging Software Defined Networks. 2) The base ALTO protocol only
   defines filters enumerating all sources and all destinations, leading
   to redundant information in the response.  To address these two
   issues, this document extends the base ALTO protocol with a more
   fine-grained filter type which allows ALTO clients to select only the
   concerned source-destination pairs, and a more expressive address
   space which allows ALTO clients to make queries beyond the limited IP
   addresses.

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/.



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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
   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 September 6, 2018.

Copyright Notice

   Copyright (c) 2018 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Flow  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Overview of Approaches  . . . . . . . . . . . . . . . . . . .   4
     3.1.  Extended Endpoint Address . . . . . . . . . . . . . . . .   5
     3.2.  Flow-based Filter . . . . . . . . . . . . . . . . . . . .   5
   4.  Changes Since Version -01 . . . . . . . . . . . . . . . . . .   5
   5.  Extended Endpoint Address . . . . . . . . . . . . . . . . . .   6
     5.1.  Address Type  . . . . . . . . . . . . . . . . . . . . . .   7
     5.2.  Endpoint Address  . . . . . . . . . . . . . . . . . . . .   7
       5.2.1.  MAC Address . . . . . . . . . . . . . . . . . . . . .   7
       5.2.2.  Domain Name . . . . . . . . . . . . . . . . . . . . .   8
       5.2.3.  IPv4 Socket Address . . . . . . . . . . . . . . . . .   8
       5.2.4.  IPv6 Socket Address . . . . . . . . . . . . . . . . .   8
     5.3.  Address Type Compatibility  . . . . . . . . . . . . . . .   8
     5.4.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Extended Cost Query Filters . . . . . . . . . . . . . . . . .   9
     6.1.  Filtered Cost Map Extension . . . . . . . . . . . . . . .   9
       6.1.1.  Capabilities  . . . . . . . . . . . . . . . . . . . .   9
       6.1.2.  Accept Input Parameters . . . . . . . . . . . . . . .  10
     6.2.  Endpoint Cost Service Extension . . . . . . . . . . . . .  10
       6.2.1.  Capabilities  . . . . . . . . . . . . . . . . . . . .  11
       6.2.2.  Accept Input Parameters . . . . . . . . . . . . . . .  11
     6.3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  12



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       6.3.1.  Information Resource Directory  . . . . . . . . . . .  12
       6.3.2.  Flow-based Filtered Cost Map Service  . . . . . . . .  13
       6.3.3.  Flow-based Endpoint Cost Service Example  . . . . . .  14
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
     8.1.  ALTO Address Type Registry  . . . . . . . . . . . . . . .  16
     8.2.  ALTO Address Type Compatibility Registry  . . . . . . . .  16
   9.  Acknowledgment  . . . . . . . . . . . . . . . . . . . . . . .  17
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  17
     10.2.  Informative References . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   ALTO cost query services (Filtered Cost Map and Endpoint Cost
   Service) can be regarded as functions transforming a given subset of
   a specific query space into a network view abstract.  However, the
   current specification has some limitations.

   First, in the base ALTO protocol [RFC7285], the endpoint cost filter
   only contains the source and destination IP addresses.  In practice,
   both Internet Service Providers (ISP) and local network
   administrators MAY conduct policy-based routing, e.g., P2P traffic
   may be constrained and has a smaller bandwidth than HTTP traffic.
   Also, web services with different QoS requirements may be hosted on
   the same machine and have the same IP address but different paths
   with different QoS metrics.

   Second, in the base ALTO protocol [RFC7285], the query space is
   defined by the lists of sources and destinations.  For a query with N
   sources and M destinations, the response contains NM entries.  While
   such a query schema is well suited for peer-to-peer (P2P)
   applications where files of the same seed are stored on all hosts, it
   may lead to a lot of redundancy in use cases such as modern data
   analytics systems where replicas of the same dataset are stored on
   only a small subset of servers.  Consider a system where the number
   of replicas is 3 (the default in HDFS), jointly scheduling N
   concurrent transfers only needs a maximum of 3N entries but the base
   ALTO protocol MAY return up to N^2 entries.

   Thus, we can conclude that the following additional requirements (AR)
   MUST be satisfied to allow ALTO clients make more accurate and
   efficient cost queries.

   AR-1:  ALTO clients SHOULD be able to specify accurate query space in
      cost query services.




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      The base ALTO protocol only includes IPv4 and IPv6 addresses as
      endpoint address types, which may not be sufficient to accurately
      identify an endpoint with emerging flow-based routing mechanisms.
      ALTO clients MAY suffer from suboptimal decisions because of such
      inaccuracy.  Thus, the ALTO protocol SHOULD be extended so that
      clients CAN be able to specify accurate query space, i.e., with
      more fine-grained endpoint address types.

   AR-2:  ALTO clients SHOULD be able to specify only the essential
      query space in cost query services.

      Existing PIDFilter (see Sec 11.3.2.3 in [RFC7285]) and
      EndpointFilter (see Sec 11.5.1.3 in [RFC7285]) represent the
      cross-product of sources and destinations, and can introduce a lot
      of redundancy in certain use cases.  This limitation CAN greatly
      harm the scalability of the ALTO protocol.  Thus, the ALTO
      protocol SHOULD be extended so that ALTO clients CAN specify only
      the essential cost query space, i.e., the concerned source-
      destination pairs.

   In this document, we describe an ALTO extension specifying flow-based
   cost queries.  The rest of this document is organized as follows.
   Section 5 introduces several new address types that extend the query
   space of ALTO cost services.  Section 6 describes the extended schema
   on Filtered Cost Map (FCM) and Endpoint Cost Service (ECS) to support
   cost queries of arbitrary source-destination combinations.  Section 7
   and Section 8 discuss security and IANA considerations.

2.  Terminology

   This document uses the same terms as defined in [RFC7285] and
   [RFC8189] with the following additional term:

2.1.  Flow

   In this document, a flow refers to all communications between two
   endpoints.  A flow is valid if and only if there CAN be valid
   communications between the two endpoints, which oftentimes requires
   that that two endpoint addresses have compatible address types.

3.  Overview of Approaches

   This section presents a non-normative overview of the extension to
   support flow-based cost query.  It assumes the readers are familiar
   with Filtered Cost Map and Endpoint Cost Service defined in [RFC7285]
   and their extensions defined in [RFC8189].





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3.1.  Extended Endpoint Address

   To allow ALTO clients specify accurate query space in cost query
   services (AR-1), this document defines several new endpoint address
   types.  An endpoint address with a new type is referred to as an
   extended endpoint address.

   Since the address types of both the source and the destination
   correspond to the same network flow, they MUST NOT conflict.  This
   document defines an address type conflict table to indicate
   conflicts.  If some source and destination address types in a query
   conflict with each others, ALTO servers SHOULD return the
   corresponding error.

3.2.  Flow-based Filter

   To allow ALTO clients specify only the essential query space in cost
   query services (AR-2), both PIDFilter and EndpointFilter in the base
   protocol MUST be extended.  The extended filters are referred to as
   flow-based filters.

   A straight-forward way of satisfying AR-1 is to have an ALTO client
   list all its concerned flows.  Despite its simplicity, it MAY be too
   large in size, especially when many flows have common sources or
   common destinations in the query.  Also from the implementation's
   perspective, it cannot reuse the functionality to parse a PIDFilter/
   EndpointFilter.

   Thus, the flow-based filters defined in this document allow ALTO
   clients to include multiple PIDFilter/EndpointFilter objects in the
   same query.  Apparently, if we replace each PIDFilter/EndpointFilter
   of N sources and M destinations with NM filters that have exactly one
   source and destination, the two representations refer to the same set
   of flows.  As a result, one can aggregate flows with common sources
   or destinations in one PIDFilter/EndpointFilter object without
   introducing redundant flows.

   From the implementation's perspective, one MAY reuse an ALTO library
   which parses PIDFilter/EndpointFilter and/or converts them into a set
   of source-destination pairs.

4.  Changes Since Version -01

   Note to Editor: Please remove this section prior to publication.

   This section records the change logs of the draft updates.

   Changes since -04 revision:



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   o  Improve the clarity of the document by explicitly stating the
      problems.

   o  Keep only flow in the terminology section.

   o  Move section 6 Advanced Flow-based Query out of this document.

   o  Change ALTO Address Type Conflicts Registry to ALTO Address Type
      Compatibility Registry.

   Changes since older versions:

   Since -03 revision:

   o  Remove some irrelevant content from the draft.

   o  Improve the description of the new endpoint address type
      identifier registry.  And add a new registry to declare the
      conflicting address type identifiers.

   Since -02 revision:

   o  Change "EndpointURI" to "AddressType::EndpointAddr" for
      consistency.

   o  Replace Cost Confidence by Cost Statistics for compatibility.

   Since -01 revision:

   o  Define the basic flow-based query extensions for Filtered Cost Map
      and Endpoint Cost service.  The basic flow-based query is downward
      compatible with the legacy ALTO service.  It does not introduce
      any new media types.

   o  Move the service of media-type application/alto-flowcost+json to
      the advanced flow-based query extension.  It will ask ALTO server
      to support the new media type.

   Since -00 revision:

   o  Change the schema of pid-flows and endpoint-flows fields from pair
      list to pair mesh list.

5.  Extended Endpoint Address

   This document registers new address types and defines the
   corresponding formats for endpoint addresses of each new address
   type.



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5.1.  Address Type

   The new AddressType identifiers defined in this document are as
   follows:

   eth:  An endpoint address with type eth is the address of an Ethernet
      interface.  It is used to uniquely identify an endpoint in the
      data link layer.

   domain:  An endpoint address with type domain is the domain name of a
      web service.  It is used to uniquely identify a web service which
      MAY be translated to one or more IPv4 address(es).

   domain6:  An endpoint address with type domain6 is the domain name of
      a web service.  It is used to uniquely identify a web service
      which MAY be translated to one or more IPv6 address(es).

   tcp:  An endpoint address with type tcp is the address of a TCP
      socket.  It is used to uniquely identify an IPv4 TCP socket in the
      transport layer.

   tcp6:  An endpoint address with type tcp6 is the address of a TCP
      socket.  It is used to uniquely identify an IPv6 TCP socket in the
      transport layer.

   udp:  An endpoint address with type udp is the address of a UDP
      socket.  It is used to uniquely identify an IPv4 UDP socket in the
      transport layer.

   udp6:  An endpoint address with type udp6 is the address of a UDP
      socket.  It is used to uniquely identify an IPv6 UDP socket in the
      transport layer.

5.2.  Endpoint Address

   This document defines EndpointAddr when AddressType is in
   Section 8.1.

5.2.1.  MAC Address

   An Endpoint Address of type eth is encoded as a MAC address, whose
   format is encoded as specified by either format EUI-48 in [EUI48] or
   EUI-64 in [EUI64].








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5.2.2.  Domain Name

   An Endpoint Address of type domain or domain6 is encoded as a domain
   name, as specified in Section 11 of [RFC2181].  It MUST have at least
   one corresponding A (domain) or AAAA (domain6) record in the DNS.

5.2.3.  IPv4 Socket Address

   An Endpoint Address of type tcp or udp is encoded as an IPv4 socket
   address.  It is encoded as a string of the format Host:Port with the
   : character as a separator.  The Host component of an IPv4 socket
   address is encoded as specified by either an IPv4 address (see
   Section 10.4.3.1 of [RFC7285]) or an IPv4-compatible domain name (see
   Section 5.2.2).  The Port component of an IPv4 socket address is
   encoded as an integer between 1 and 65535.

5.2.4.  IPv6 Socket Address

   An Endpoint Address of type tcp6 or udp6 is encoded as an IPv6 socket
   address.  It is also encoded as a string of the format Host:Port with
   the : character as a separator.  The Host component of an IPv6 socket
   address is encoded as specified by either an IPv6 address (see
   Section 10.4.3.2 of [RFC7285]) enclosed in the [" and "] characters
   or an IPv6-compatible domain name (see Section 5.2.2).  The Port
   component of IPv6 socket address is encoded as an integer between 1
   and 65535.

5.3.  Address Type Compatibility

   In practice, a flow with endpoint addresses with different types MAY
   NOT be valid.  For example, a source endpoint with an IPv4 address
   CANNOT establish a network connection with a destination endpoint
   with an IPv6 address.  Neither can a source with a TCP socket address
   and a destination with a UDP socket address.

   Thus, to explicitly define the compatibility between AddressType
   identifiers, every ALTO AddressType identifier MUST provide a list of
   AddressType identifiers that are compatible with it in the ALTO
   Address Type Compatibility Registry Section 8.2.  For all sources and
   destinations in a PIDFilter/EndpointFilter, if the AddressType
   identifiers of a given pair DO NOT appear in the ALTO Address Type
   Compatibility Registry, an ALTO server MUST return an ALTO error
   response with the error code "E_INVALID_FIELD_VALUE" with optional
   information to help diagnose the incompatibility.







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5.4.  Examples

   Some valid endpoint addresses are demonstrated as follows:

       "eth:98-e0-d9-9c-df-81"
       "domain:www.example.com"
       "tcp:198.51.100.34:5123"
       "udp6:[2000::1:2345:6789:abcd]:8080"

6.  Extended Cost Query Filters

   This section describes extensions to [RFC7285] and [RFC8189] to
   support flow-based cost queries.

   This document uses the notation rules specified in Section 8.2 of
   [RFC7285] and also the notation rule for optional fields in Section 4
   of [RFC8189].

6.1.  Filtered Cost Map Extension

   This document extends the Filtered Cost Map as defined in
   Section 11.3.2 of [RFC7285] and Section 4.1 of [RFC8189], by adding a
   new capability and input parameters.

   The media type, HTTP method, and uses specifications (described in
   Sections 11.3.2.1, 11.3.2.2, and 11.3.2.5 of [RFC7285], respectively)
   are unchanged.

   The response is the same as defined in Section 4.1.3 of [RFC8189].

6.1.1.  Capabilities

   The Filtered Cost Map capabilities are extended with a new member:

   o  flow-based-filter

   The capability flow-based-filter indicates whether this resource
   supports flow-based cost queries.  The FilteredCostMapCapabilities
   object in Section 4.1.1 of [RFC8189] is extended as follows:

       object {
         JSONString cost-type-names<1..*>;
         [JSONBool cost-constraints;]
         [JSONNumber max-cost-types;]
         [JSONString testable-cost-type-names<1..*>;]
         [JSONBool flow-based-filter;]
       } FilteredCostMapCapabilities;




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   cost-type-names and cost-constraints:  As defined in Section 11.3.2.4
      of [RFC7285].

   max-cost-types and testable-cost-type-names:  As defined in
      Section 4.1.1 of [RFC8189].

   flow-based-filter:  If true, an ALTO Server allows a field pid-flows
      to be included in the requests.  If not present, this field MUST
      be interpreted as if it is false.

6.1.2.  Accept Input Parameters

   The ReqFilteredCostMap object in Section 4.1.2 of [RFC8189] is
   extended as follows:

       object {
         [CostType cost-type;]
         [CostType multi-cost-types<1..*>;]
         [CostType testable-cost-types<1..*>;]
         [JSONString constraints<0..*>;]
         [JSONString or-constraints<1..*><1..*>;]
         [PIDFilter  pids;]
         [PIDFilter  pid-flows<1..*>;]
       } ReqFilteredCostMap;

   cost-type, multi-cost-types, testable-cost-types, constraints, or-
   constraints: As defined in Section 4.1.2 of [RFC8189].

   pids:  As defined in Section 11.3.2.3 of [RFC7285].

   pid-flows:  Defined as a list of PIDFilter objects.  The ALTO server
      MUST interpret PID pairs appearing in multiple PIDFilter objects
      as if they appeared only once.

   An ALTO client MUST include either pids or pid-flows in a query but
   MUST NOT include both at the same time.

6.2.  Endpoint Cost Service Extension

   This document extends the Endpoint Cost Service as defined in
   Section 11.5.1 of [RFC7285] and Section 4.2 of [RFC8189], by adding a
   new capability and input parameters.

   The media type, HTTP method, and uses specifications (described in
   Sections 11.5.1.1, 11.5.1.2, and 11.5.1.5 of [RFC7285], respectively)
   are unchanged.

   The response is the same as defined in Section 4.2.3 of [RFC8189].



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6.2.1.  Capabilities

   The extension to EndpointCostCapabilities includes two new members:

   o  address-types

   o  flow-based-filter

   Only if the capability "flow-based-filter" is present and its value
   is "true", the ALTO server supports the flow-based extension for this
   endpoint cost service.  The capability "address-types" indicates
   which endpoint address types are supported by this resource, it MUST
   NOT be included if "flow-based-filter" is absent or the value is
   false.

       object {
         [JSONString  address-types<0..*>;]
         [JSONBool    flow-based-filter;]
       } EndpointCostCapabilities : FilteredCostMapCapabilities;

   flow-based-filter:  If true, an ALTO Server MUST accept field
      "endpoint-flows" in the requests.  If not present, this field MUST
      be interpreted as if it is specified false.

   address-types:  Defines a list of AddressType identifiers encoded as
      a JSONArray of JSONString.  All AddressType identifiers MUST be
      registered in the "ALTO Address Type Registry" (see Section 14.4
      of [RFC7285]).  An ALTO server SHOULD NOT claim "ipv4" and "ipv6"
      in this field explicitly, because they are supported by default.
      If not present, this field MUST be interpreted as if it is an
      empty array, i.e., the ALTO server only supports the default
      "ipv4" and "ipv6" address types.

6.2.2.  Accept Input Parameters

   The ReqEndpointCostMap object in Section 4.2.2 of [RFC8189] is
   extended as follows:

       object {
         [CostType cost-type;]
         [CostType multi-cost-types<1..*>;]
         [CostType testable-cost-types<1..*>;]
         [JSONString constraints<0..*>;]
         [JSONString or-constraints<1..*><1..*>;]
         [EndpointFilter endpoints;]
         [EndpointFilter endpoint-flows<1..*>;]
       } ReqEndpointCostMap;




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   cost-type, multi-cost-types, testable-cost-types, constraints, or-
   constraints:
      As defined in Section 4.1.2 of [RFC8189].

   endpoints:  As defined in Section 11.5.1.3 of [RFC7285].

   endpoint-flows:  Defined as a list of EndpointFilter objects.  The
      ALTO server MUST interpret endpoint pairs appearing in multiple
      EndpointFilter objects as if they appeared only once.

   If the AddressType of the source and destination in the same
   EndpointFilter do NOT conform the compatibility rule defined in
   Table 1 of Section 8.1, an ALTO server MUST return an ALTO error
   response with the error code "E_INVALID_FIELD_VALUE".

   An ALTO client MUST specify either "endpoints" or "endpoint-flows",
   but MUST NOT specify both in the same query.

6.3.  Examples

6.3.1.  Information Resource Directory

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

   HTTP/1.1 200 OK
   Content-Length: [TODO]
   Content-Type: application/alto-directory+json
   {
     "meta" : {
      "default-alto-network-map" : "my-default-network-map",
      "cost-types" : {
        "num-routingcost" : {
          "cost-mode" : "numerial",
          "cost-metric" : "routingcost"},
        "ord-routingcost" : {
          "cost-mode" : "ordinal",
          "cost-metric" : "routingcost"}
      },
       .....
       Other ALTO cost types as described in RFC7285
       .....
     },
     "resources" : {
       "my-default-network-map" : {
         "uri" : "http://alto.example.com/networkmap",
         "media-type" : "application/alto-networkmap+json"



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       },
       "basic-flow-based-cost-map" : {
         "uri" : "http://alto.example.com/costmap/multi/filtered",
         "media-type" : "application/alto-costmap+json",
         "accepts" : "application/alto-costmapfilter+json",
         "uses" : [ "my-default-network-map" ],
         "capabilities" : {
           "max-cost-types" : 2,
           "flow-based-filter" : true,
           "cost-type-names" : [ "ord-routingcost" , "num-routingcost" ]
         }
       },
       "basic-flow-based-endpoint-cost" : {
         "uri" : "http://alto.example.com/endpointcost/lookup",
         "media-type" : "application/alto-endpointcost+json",
         "accepts" : "application/alto-endpointcostparams+json",
         "capabilities" : {
           "protocols": ["tcp", "http"],
           "flow-based-filter" : true,
           "cost-type-names" : [ "ord-routingcost" , "num-routingcost" ]
         }
       },
       "flow-cost-map": {
         "uri" : "http://alto.example.com/flowcost/lookup",
         "media-type" : "application/alto-flowcost+json",
         "accepts" : "application/alto-flowcostparams+json",
         "capabilities" : {
           "or-required" : [ [ "ethernet:destination" ],
                             [ "ipv4:destination" ] ],
           "optional" : [ "ethernet:source", "ethernet:destination",
                          "ipv4:source", "ipv4:destination",
                          "tcp:source", "tcp:destination"]
         }
       }
     }
   }

6.3.2.  Flow-based Filtered Cost Map Service













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     POST /costmap/multi/filtered HTTP/1.1
     Host: alto.example.com
     Accept: application/alto-costmap+json,application/alto-error+json
     Content-Length: [TBD]
     Content-Type: application/alto-costmapfilter+json

     {
       "cost-type": {
         "cost-mode": "numerical",
         "cost-metric": "routingcost"
       },
       "pid-flows": [
         { "srcs": ["PID1"], "dsts": ["PID2", "PID3"] },
         { "srcs": ["PID3"], "dsts": ["PID4"] }
       ]
     }

     HTTP/1.1 200 OK
     Content-Length: [TBD]
     Content-Type: application/alto-costmap+json

     {
       "meta": {
         "dependent-vtags": [
           {
             "resource-id": "my-default-network-map",
             "tag": "75ed013b3cb58f896e839582504f622838ce670f"
           }
         ],
         "cost-type": {
           "cost-mode": "numerical",
           "cost-metric": "routingcost"
         }
       },
       "cost-map": {
         "PID1": { "PID2": 100 },
         "PID1": { "PID3": 20 },
         "PID3": { "PID4": 80 }
       }
     }

6.3.3.  Flow-based Endpoint Cost Service Example









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  POST /endpointcost/lookup HTTP/1.1
  Host: alto.example.com
  Accept: application/alto-endpointcost+json,application/alto-error+json
  Content-Length: [TBD]
  Content-Type: application/alto-endpointcostparams+json

  {
    "cost-type": {
      "cost-mode": "numerical",
      "cost-metric": "hopcount"
    },
    "endpoint-flows": [
      { "srcs": ["ipv4:192.0.2.2"],
        "dsts": ["ipv4:192.0.2.89", "http:cdn1.example.com"] },
      { "srcs": ["tcp:203.0.113.45:54321"],
        "dsts": ["http:cdn1.example.com"] }
    ]
  }


  HTTP/1.1 200 OK
  Content-Length: [TBD]
  Content-Type: application/alto-endpointcost+json

  {
    "meta": {
      "cost-type": {
        "cost-mode": "numerical",
        "cost-metric": "hopcount"
      }
    },
    "endpoint-cost-map": {
      "ipv4:192.0.2.2": {
        "ipv4:192.0.2.89": 3,
        "http:cdn1.example.com": 6
      },
      "tcp:203.0.113.45:54321": {
        "http:cdn1.example.com": 10
      }
    }
  }

7.  Security Considerations

   As discussed in Section 15.4 of [RFC7285], an ALTO server or a third
   party who is able to intercept the flow-based cost query messages MAY
   store and process the obtained information in order to analyze user
   behaviors and communication patterns.  Since flow-based cost queries



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   MAY potentially provide more accurate information, an ALTO client
   should be cognizant about the trade-off between redundancy and
   privacy.

8.  IANA Considerations

   This document defines new address types to be registered to an
   existing ALTO registry, and a new registry for their compatible
   address types.

8.1.  ALTO Address Type Registry

   This document defines several new address types to be registered to
   ALTO Address Type Registry, listed in Table 1.

   +------------+--------------------+-------------+-------------------+
   | Identifier | Address Encoding   | Prefix      | Mapping to/from   |
   |            |                    | Encoding    | IPv4/v6           |
   +------------+--------------------+-------------+-------------------+
   | eth        | See Section 5.2.1  | None        | Mapping to/from   |
   |            |                    |             | IPv4 by [RFC0903] |
   |            |                    |             | and [RFC0826];    |
   |            |                    |             | Mapping to/from   |
   |            |                    |             | IPv6 by [RFC3122] |
   |            |                    |             | and [RFC4861]     |
   | domain     | See Section 5.2.2  | None        | Mapping to/from   |
   |            |                    |             | IPv4 by [RFC1034] |
   | domain6    | See Section 5.2.2  | None        | Mapping to/from   |
   |            |                    |             | IPv6 by [RFC3596] |
   | tcp        | See Section 5.2.3  | None        | No mapping        |
   | tcp6       | See Section 5.2.4  | None        | No mapping        |
   | upd        | See Section 5.2.3  | None        | No mapping        |
   | udp6       | See Section 5.2.4  | None        | No mapping        |
   +------------+--------------------+-------------+-------------------+

                    Table 1: ALTO Address Type Registry

8.2.  ALTO Address Type Compatibility Registry

   This document proposes to create a new registry called ALTO Address
   Type Compatibility Registry, whose purpose is stated in Section 5.3.

   The compatible address type identifiers of the ones registered in the
   ALTO Address Type Registry are listed in Table 2.







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                 +-------------+-------------------------+
                 | Identifier  | Compatible Identifiers  |
                 +-------------+-------------------------+
                 | eth         | ipv4, ipv6              |
                 | domain      | eth, ipv4               |
                 | domain6     | eth, ipv6               |
                 | tcp         | eth, ipv4, domain       |
                 | tcp6        | eth, ipv6, domain6      |
                 | udp         | eth, ipv4, domain       |
                 | udp6        | eth, ipv6, domain6      |
                 +-------------+-------------------------+

             Table 2: ALTO Address Type Compatibility Registry

   The entry of an address type identifier SHOULD only include the
   identifiers registered before it.  The compatibility between address
   types are bidirectional.  For example, although "eth" does not
   register "tcp" as its compatible identifier, an ALTO server MUST
   recognize them as compatible because eth is registered as a
   compatible identifier of "tcp".

   Any new ALTO address type identifier registered after this document
   MUST register their compatible identifiers in this registry
   simultaneously.

9.  Acknowledgment

   The authors would like to thank Dawn Chen, Haizhou Du, Sabine
   Randriamasy and Wendy Roome for their fruitful discussions and
   feedback on this document.  Shawn Lin also gave substantial review
   feedback and suggestions on the protocol design.

10.  References

10.1.  Normative References

   [RFC0826]  Plummer, D., "Ethernet Address Resolution Protocol: Or
              Converting Network Protocol Addresses to 48.bit Ethernet
              Address for Transmission on Ethernet Hardware", STD 37,
              RFC 826, DOI 10.17487/RFC0826, November 1982,
              <https://www.rfc-editor.org/info/rfc826>.

   [RFC0903]  Finlayson, R., Mann, T., Mogul, J., and M. Theimer, "A
              Reverse Address Resolution Protocol", STD 38, RFC 903,
              DOI 10.17487/RFC0903, June 1984, <https://www.rfc-
              editor.org/info/rfc903>.





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   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <https://www.rfc-editor.org/info/rfc1034>.

   [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>.

   [RFC2181]  Elz, R. and R. Bush, "Clarifications to the DNS
              Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
              <https://www.rfc-editor.org/info/rfc2181>.

   [RFC2732]  Hinden, R., Carpenter, B., and L. Masinter, "Format for
              Literal IPv6 Addresses in URL's", RFC 2732,
              DOI 10.17487/RFC2732, December 1999, <https://www.rfc-
              editor.org/info/rfc2732>.

   [RFC3122]  Conta, A., "Extensions to IPv6 Neighbor Discovery for
              Inverse Discovery Specification", RFC 3122,
              DOI 10.17487/RFC3122, June 2001, <https://www.rfc-
              editor.org/info/rfc3122>.

   [RFC3596]  Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,
              "DNS Extensions to Support IP Version 6", STD 88,
              RFC 3596, DOI 10.17487/RFC3596, October 2003,
              <https://www.rfc-editor.org/info/rfc3596>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007, <https://www.rfc-
              editor.org/info/rfc4861>.

10.2.  Informative References

   [EUI48]    IEEE, , "Guidelines for use of a 48-bit Extended Unique
              Identifier (EUI-48)", 2012,
              <http://standards.ieee.org/develop/regauth/tut/eui48.pdf>.

   [EUI64]    IEEE, , "Guidelines for use of a 64-bit Extended Unique
              Identifier (EUI-64)", November 2012,
              <http://standards.ieee.org/develop/regauth/tut/eui64.pdf>.




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   [OF15]     Foundation, O., "OpenFlow Switch Specification v1.5.0",
              2014,
              <https://www.opennetworking.org/images/stories/downloads/
              sdn-resources/onf-specifications/openflow/openflow-switch-
              v1.5.0.noipr.pdf>.

   [OPENFLOW]
              McKeown, N., Anderson, T., Balakrishnan, H., Parulkar, G.,
              Peterson, L., Rexford, J., Shenker, S., and J. Turner,
              "OpenFlow: enabling innovation in campus networks", 2008.

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <https://www.rfc-editor.org/info/rfc7159>.

   [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>.

   [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>.

Authors' Addresses

   Jingxuan Jensen Zhang
   Tongji University
   4800 Cao'an Hwy
   Shanghai  201804
   China

   Email: jingxuan.n.zhang@gmail.com


   Kai Gao
   Tsinghua University
   30 Shuangqinglu Street
   Beijing  100084
   China

   Email: gaok12@mails.tsinghua.edu.cn







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   Junzhuo Austin Wang
   Tongji University
   4800 Cao'an Hwy, Jiading District
   Shanghai
   China

   Email: wangjunzhuo200@gmail.com


   Qiao Xiang
   Tongji/Yale University
   51 Prospect Street
   New Haven, CT
   USA

   Email: qiao.xiang@cs.yale.edu


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

   Email: yry@cs.yale.edu


























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