draft-ietf-alto-multi-cost-02.txt   draft-ietf-alto-multi-cost-03.txt 
Network Working Group S. Randriamasy Network Working Group S. Randriamasy
Internet-Draft W. Roome Internet-Draft W. Roome
Intended status: Standards Track Nokia Bell Labs Intended status: Standards Track Nokia Bell Labs
Expires: December 15, 2016 N. Schwan Expires: February 11, 2017 N. Schwan
Thales Deutschland Thales Deutschland
June 13, 2016 August 10, 2016
Multi-Cost ALTO Multi-Cost ALTO
draft-ietf-alto-multi-cost-02 draft-ietf-alto-multi-cost-03
Abstract Abstract
The ALTO (Application Layer-Traffic Optimization) Protocol The ALTO (Application Layer-Traffic Optimization) Protocol
([RFC7285]) defines several services that return various metrics ([RFC7285]) defines several services that return various metrics
describing the costs between network endpoints. For example, when describing the costs between network endpoints. An ALTO Server may
downloading a file that is mirrored on several sites, a user offer a variety of cost metrics, based on latency,bandwidth, hop
application may use these ALTO cost metrics to determine the most count, jitter, or whatever else the ALTO Server deems useful. For
efficient mirror site. example, when downloading a file that is mirrored on several sites, a
user application may consider more than one metric, perhaps trading
bandwidth for latency to determine the most efficient mirror site.
An ALTO Server may offer a variety of cost metrics, based on latency, While the base ALTO Protocol allows a client to use more than one
bandwidth, hop count, jitter, or whatever else the ALTO Server deems cost metric, to do so, the client must request each metric
useful. When selecting a mirror site, a client may consider more separately. This document defines a new service that allows a client
than one metric, perhaps trading bandwidth for latency. While the to retrieve several cost metrics with one request, which is
base ALTO Protocol allows a client to use more than one cost metric, considerably more efficient. In addition, this document extends the
to do so, the client must request each metric separately. This ALTO constraint tests to allow a user to specify an arbitrary logical
document defines a new service that allows a client to retrieve combination of tests on several cost metrics.
several cost metrics with one request, which is considerably more
efficient. In addition, this document extends the ALTO constraint
tests to allow a user to specify an arbitrary logical combination of
tests on several cost metrics.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 15, 2016. This Internet-Draft will expire on February 11, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Overview Of Approach . . . . . . . . . . . . . . . . . . . . 5 3. Overview Of Approach . . . . . . . . . . . . . . . . . . . . 5
3.1. Multi-Cost Data Format . . . . . . . . . . . . . . . . . 5 3.1. Multi-Cost Data Format . . . . . . . . . . . . . . . . . 5
3.2. Compatibility With Legacy Clients . . . . . . . . . . . . 6 3.2. Compatibility With Legacy ALTO Clients . . . . . . . . . 6
3.3. Filtered Multi Cost Map Resources . . . . . . . . . . . . 6 3.3. Filtered Multi Cost Map Resources . . . . . . . . . . . . 6
3.4. Endpoint Cost Service Resources . . . . . . . . . . . . . 7 3.4. Endpoint Cost Service Resources . . . . . . . . . . . . . 7
3.5. Full Cost Map Resources . . . . . . . . . . . . . . . . . 7 3.5. Full Cost Map Resources . . . . . . . . . . . . . . . . . 7
3.6. Extended Constraint Tests . . . . . . . . . . . . . . . . 8 3.6. Extended Constraint Tests . . . . . . . . . . . . . . . . 8
3.6.1. Extended constraint predicates . . . . . . . . . . . 8 3.6.1. Extended constraint predicates . . . . . . . . . . . 8
3.6.2. Extended logical combination of predicates . . . . . 8 3.6.2. Extended logical combination of predicates . . . . . 8
3.6.3. Testable Cost Types in constraints . . . . . . . . . 9 3.6.3. Testable Cost Types in constraints . . . . . . . . . 9
3.6.4. Testable Cost Type Names in IRD capabilities . . . . 9 3.6.4. Testable Cost Type Names in IRD capabilities . . . . 9
3.6.5. Legacy client issues . . . . . . . . . . . . . . . . 10 3.6.5. Legacy ALTO Client issues . . . . . . . . . . . . . . 10
4. Protocol Extensions for Multi-Cost ALTO Transactions . . . . 11 4. Protocol Extensions for Multi-Cost ALTO Transactions . . . . 11
4.1. Filtered Cost Map Extensions . . . . . . . . . . . . . . 11 4.1. Filtered Cost Map Extensions . . . . . . . . . . . . . . 11
4.1.1. Capabilities . . . . . . . . . . . . . . . . . . . . 11 4.1.1. Capabilities . . . . . . . . . . . . . . . . . . . . 11
4.1.2. Accept Input Parameters . . . . . . . . . . . . . . . 12 4.1.2. Accept Input Parameters . . . . . . . . . . . . . . . 12
4.1.3. Response . . . . . . . . . . . . . . . . . . . . . . 15 4.1.3. Response . . . . . . . . . . . . . . . . . . . . . . 15
4.2. Endpoint Cost Service Extensions . . . . . . . . . . . . 15 4.2. Endpoint Cost Service Extensions . . . . . . . . . . . . 16
4.2.1. Capabilities . . . . . . . . . . . . . . . . . . . . 16 4.2.1. Capabilities . . . . . . . . . . . . . . . . . . . . 16
4.2.2. Accept Input Parameters . . . . . . . . . . . . . . . 16 4.2.2. Accept Input Parameters . . . . . . . . . . . . . . . 16
4.2.3. Response . . . . . . . . . . . . . . . . . . . . . . 17 4.2.3. Response . . . . . . . . . . . . . . . . . . . . . . 17
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.1. Information Resource Directory . . . . . . . . . . . . . 17 5.1. Information Resource Directory . . . . . . . . . . . . . 18
5.2. Multi-Cost Filtered Cost Map: Example #1 . . . . . . . . 19 5.2. Multi-Cost Filtered Cost Map: Example #1 . . . . . . . . 20
5.3. Multi-Cost Filtered Cost Map: Example #2 . . . . . . . . 20 5.3. Multi-Cost Filtered Cost Map: Example #2 . . . . . . . . 21
5.4. Multi-Cost Filtered Cost Map: Example #3 . . . . . . . . 21 5.4. Multi-Cost Filtered Cost Map: Example #3 . . . . . . . . 23
5.5. Multi-Cost Filtered Cost Map: Example #4 . . . . . . . . 23 5.5. Multi-Cost Filtered Cost Map: Example #4 . . . . . . . . 24
5.6. Endpoint Cost Service . . . . . . . . . . . . . . . . . . 25 5.6. Endpoint Cost Service . . . . . . . . . . . . . . . . . . 26
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
7. Privacy And Security Considerations . . . . . . . . . . . . . 26 7. Privacy And Security Considerations . . . . . . . . . . . . . 27
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 28
9.1. Normative References . . . . . . . . . . . . . . . . . . 26 9.1. Normative References . . . . . . . . . . . . . . . . . . 28
9.2. Informative References . . . . . . . . . . . . . . . . . 27 9.2. Informative References . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
1. Introduction 1. Introduction
IETF has designed a new service called ALTO that provides guidance to IETF has defined ALTO services in [RFC7285] to provide guidance to
overlay applications, which have to select one or several hosts from overlay applications, which have to select one or several hosts from
a set of candidates that are able to provide a desired resource. a set of candidates that are able to provide a desired resource.
This guidance is based on parameters such as the topological This guidance is based on parameters such as the topological
distance, that affect performance and efficiency of the data distance, that affect performance and efficiency of the data
transmission between the hosts. The purpose of ALTO is to improve transmission between the hosts. The purpose of ALTO is to improve
Quality of Experience (QoE) in the application while reducing Quality of Experience (QoE) in the application while reducing
resource consumption in the underlying network infrastructure. The resource consumption in the underlying network infrastructure. The
ALTO protocol conveys the Internet View from the perspective of a ALTO protocol conveys the Internet View from the perspective of a
Provider Network region that spans from a region to one or more Provider Network region that spans from a region to one or more
Autonomous System (AS) and is called a Network Map. ALTO may also Autonomous System (AS) and is called a Network Map. ALTO may also
provide the Provider determined Cost Map between locations of the provide the Provider determined Cost Map between locations of the
Network Map or Endpoint Cost Map between groups of individual Network Map or Endpoint Cost Map between groups of individual
endpoints. Last, these costs are provided as numerical or ordinal endpoints. Last, these costs are provided as numerical or ordinal
values. values.
Current ALTO Costs and their modes provide values that are seen to be Current ALTO Costs and their modes provide values such as hopcount
stable over a longer period of time, such as hopcount and and administrative routing cost to reflect ISP routing preferences.
administrative routing cost to reflect ISP routing preferences.
Recently, new use cases have extended the usage scope of ALTO to Recently, new use cases have extended the usage scope of ALTO to
Content Delivery Networks (CDN), Data Centers and applications that Content Delivery Networks (CDN), Data Centers and applications that
need additional information to select their Endpoints or handle their need additional information to select their Endpoints or handle their
PIDs. PIDs.
Thus a multitude of new Cost Types that better reflect the Thus a multitude of new Cost Types that better reflect the
requirements of these applications are expected to be specified, in requirements of these applications are expected to be specified.
particular cost values that change more frequently than previously Handling multiple costs, however, can add more complexities, such as
assumed. overheads and consistency. In particular, cost values that change
more frequently than previously assumed may require more frequent
The ALTO protocol [RFC7285] restricts ALTO Cost Maps and Endpoint ALTO requests. Moreover, to make sure to have up to date values,
Cost services to only one Cost Type and Cost Mode per ALTO request. applications using several frequently changing metrics will tend to
refresh their values simultaneously.
To retrieve information for several Cost Types, an ALTO client must The ALTO protocol [RFC7285], which this document refers to as the
send several separate requests to the server. base protocol, restricts ALTO Cost Maps and Endpoint Cost services to
only one Cost Type and Cost Mode per ALTO request. To retrieve
information for several Cost Types, an ALTO client must send several
separate requests to the Server.
It would be far more efficient, in terms of Round Trip Time (RTT), It would be far more efficient, in terms of Round Trip Time (RTT),
traffic, and processing load on the ALTO client and server, to get traffic, and processing load on the ALTO Client and Server, to get
all costs with a single query/response transaction. Vector costs all costs with a single query/response transaction. Vector costs
provide a robust and natural input to multi-variate path computation provide a robust and natural input to multi-variate path computation
as well as robust multi-variate selection of multiple Endpoints. In as well as robust multi-variate selection of multiple Endpoints. In
particular, one Cost Map reporting on N Cost Types is less bulky than particular, one Cost Map reporting on N Cost Types is less bulky than
N Cost Maps containing one Cost Type each. This is valuable for both N Cost Maps containing one Cost Type each. This is valuable for both
the storage of these maps and for their transmission. Additionally, the storage of these maps and for their transmission. Additionally,
for many emerging applications that need information on several Cost for many emerging applications that need information on several Cost
Types, having them gathered in one map will save time. Another Types, having them gathered in one map will save time. Another
potential advantage is consistency: providing values for several Cost potential advantage is consistency: providing values for several Cost
Types in one single batch is useful for Clients needing synchronized Types in one single batch is useful for ALTO clients needing
ALTO information updates. synchronized ALTO information updates.
Along with multi-cost values queries, the filtering capabilities need Along with multi-cost values queries, the filtering capabilities need
to be extended to allow constraints on multiple metrics. The base to be extended to allow constraints on multiple metrics. The base
protocol allows a client to provide optional constraint tests for a protocol allows an ALTO client to provide optional constraint tests
Filtered Cost Map or the Endpoint Cost Service. In the base for a Filtered Cost Map or the Endpoint Cost Service. In the base
protocol, the constraint tests are limited to the AND-combination of protocol, the constraint tests are limited to the AND-combination of
simple comparison tests on the value of the (single) requested Cost simple comparison tests on the value of the (single) requested Cost
Type. It is therefore necessary to allow constraints on multiple Type. It is therefore necessary to allow constraints on multiple
metrics. Beyond that, applications that are sensitive to several metrics. Beyond that, applications that are sensitive to several
metrics and struggle with complicated network conditions may need to metrics and struggle with complicated network conditions may need to
arbitrate between conflicting objectives such as routing cost and arbitrate between conflicting objectives such as routing cost and
network performance. To address this issue, this document proposes network performance. To address this issue, this document proposes
to extend the base protocol by extending constraints to test multiple to extend the base protocol by extending constraints to test multiple
metrics, and by allowing these constraints to be combined with metrics, and by allowing these constraints to be combined with
logical 'ORs' as well as logical 'ANDs'. This allows an application logical 'ORs' as well as logical 'ANDs'. This allows an application
to make requests such as: "select solutions with either (moderate to make requests such as: "select solutions with either (moderate
"hopcount" AND high "routingcost") OR (higher "hopcount" AND moderate "hopcount" AND high "routingcost") OR (higher "hopcount" AND moderate
"routingcost")". To ensure compatibility with legacy ALTO Clients, "routingcost")". To ensure compatibility with legacy ALTO clients,
only the Filtered Cost Map and Endpoint Cost Map services are only the Filtered Cost Map and Endpoint Cost Map services are
extended to return Multi-Cost values. Full Cost Map services remain extended to return Multi-Cost values. Full Cost Map services remain
unchanged, and are restricted to returning single cost values. unchanged, and are restricted to returning single cost values.
This document is organized as follows: Section 2 defines terminology This document is organized as follows: Section 2 defines terminology
used in this document. Section 3 gives a non-normative overview of used in this document. Section 3 gives a non-normative overview of
the multi-cost extensions, and Section 4 gives their formal the multi-cost extensions, and Section 4 gives their formal
definitions. Section 5 gives several complete examples. The definitions. Section 5 gives several complete examples. The
remaining sections describe the IANA and privacy considerations. remaining sections describe the IANA and privacy considerations.
2. Terminology 2. Terminology
o {1.2.3}: References with curly brackets are to sections in the o {1.2.3}: References with curly brackets are to sections in the
ALTO protocol specification [RFC7285]. ALTO protocol specification [RFC7285].
o Endpoint (EP): A Peer, a CDN storage location, a physical server o ALTO transaction: A request/response exchange between an ALTO
involved in a virtual server-supported application, a party in a client and an ALTO Server.
resource sharing swarm such as a computation grid or an online
multi-party game. o Application client (AC): This term generalizes the case of a P2P
client to include the case of a CDN client, a client of an
application running on a virtual server, a Grid application
client, or any application client that can choose between several
connection points for data or resource exchange.
o Client: this term refers to an ALTO client, when used with a
capital "C".
o Endpoint (EP): an endpoint can be for example a Peer, a CDN
storage location, a physical server involved in a virtual server-
supported application, a party in a resource sharing swarm such as
a computation grid or an online multi-party game.
o Endpoint Discovery (EP Discovery): This term covers the different o Endpoint Discovery (EP Discovery): This term covers the different
types of processes used to discover the eligible endpoints. types of processes used to discover the eligible endpoints.
o Network Service Provider (NSP): Includes both ISPs, who provide o Network Service Provider (NSP): Includes both ISPs, who provide
means to transport the data, and CDNs who care for the means to transport the data, and CDNs who care for the
dissemination, persistent storage and possibly identification of dissemination, persistent storage and possibly identification of
the best/closest content copy. the best/closest content copy.
o ALTO transaction: A request/response exchange between an ALTO o Server: this term refers to an ALTO server, when used with a
Client and an ALTO Server. capital "S".
o Application Client (AC): This term generalizes the case of a P2P
client to include the case of a CDN client, a client of an
application running on a virtual server, a Grid application
client, or any Client that can choose between several connection
points for data or resource exchange.
3. Overview Of Approach 3. Overview Of Approach
The following is a non-normative overview of the multi-cost The following is a non-normative overview of the multi-cost
extensions defined in this document. It assumes the reader is extensions defined in this document. It assumes the reader is
familiar with Cost Map resources in the ALTO Protocol ([RFC7285]). familiar with Cost Map resources in the ALTO Protocol ([RFC7285]).
3.1. Multi-Cost Data Format 3.1. Multi-Cost Data Format
Formally, the cost entries in an ALTO Cost Map can be any type of Formally, the cost entries in an ALTO Cost Map can be any type of
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Therefore this document extends the definition of a Cost Map to allow Therefore this document extends the definition of a Cost Map to allow
a cost to be an array of costs, one per metric, instead of just one a cost to be an array of costs, one per metric, instead of just one
number. For example, here is a Cost Map with the "routingcost" and number. For example, here is a Cost Map with the "routingcost" and
"hopcount" metrics. Note that this is identical to a regular ALTO "hopcount" metrics. Note that this is identical to a regular ALTO
Cost Map, except that the values are arrays instead of numbers. Cost Map, except that the values are arrays instead of numbers.
{ {
"meta" : { "meta" : {
"dependent-vtags" : [ ... ], "dependent-vtags" : [ ... ],
"cost-type" : {},
"multi-cost-types" : [ "multi-cost-types" : [
{"cost-mode": "numerical", "cost-metric": "routingcost"}, {"cost-mode": "numerical", "cost-metric": "routingcost"},
{"cost-mode": "numerical", "cost-metric": "hopcount"} {"cost-mode": "numerical", "cost-metric": "hopcount"}
] ]
} }
"cost-map" : { "cost-map" : {
"PID1": { "PID1":[1,0], "PID2":[5,23], "PID3":[10,5] }, "PID1": { "PID1":[1,0], "PID2":[5,23], "PID3":[10,5] },
... ...
} }
} }
3.2. Compatibility With Legacy Clients 3.2. Compatibility With Legacy ALTO Clients
The multi-cost extensions defined in this document must not break The multi-cost extensions defined in this document must not break
legacy implementations (that is, clients and servers which are not legacy implementations (that is, ALTO clients and servers which are
aware of these extensions). One way to achieve that would be to not aware of these extensions). One way to achieve that would be to
define a new media type for an array-valued Multi Cost Map. However, define a new media type for an array-valued Multi Cost Map. However,
as indicated above, an array-valued Multi Cost Map is almost as indicated above, an array-valued Multi Cost Map is almost
identical to a single-valued Cost Map, so it should be simple to identical to a single-valued Cost Map, so it should be simple to
write a parser which handles either type of cost map. Hence defining write a parser which handles either type of cost map. Hence defining
a new media type could result in a lot of wasteful duplication. a new media type could result in a lot of wasteful duplication.
Therefore this document does not define any new media types. Therefore this document does not define any new media types.
Instead, as described below, it extends the specifications in the Instead, as described below, it extends the specifications in the
ALTO Server's Information Resource Directory (IRD) so that legacy ALTO Server's Information Resource Directory (IRD) so that legacy
clients will not request array-valued Multi Cost Map resources. This clients will not request array-valued Multi Cost Map resources. This
relies on the requirement that ALTO Clients MUST ignore unknown relies on the requirement that ALTO clients MUST ignore unknown
fields ({8.3.7}). fields ({8.3.7}).
3.3. Filtered Multi Cost Map Resources 3.3. Filtered Multi Cost Map Resources
This document extends the Filtered Cost Map service to allow the same This document extends the Filtered Cost Map service to allow the same
resource to return either a single-valued Cost Map, as defined in resource to return either a single-valued Cost Map, as defined in
[RFC7285], or an array-valued Multi Cost Map, as defined in this [RFC7285], or an array-valued Multi Cost Map, as defined in this
document. An extended Filtered Cost Map resource has a new document. An extended Filtered Cost Map resource has a new
capability, "max-cost-types". The value is the maximum number of capability, "max-cost-types". The value is the maximum number of
cost types this resource can return for one request. The existence cost types this resource can return for one request. The existence
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"media-types" : [ "application/alto-costmap+json" ], "media-types" : [ "application/alto-costmap+json" ],
"accepts" : [ "application/alto-costmapfilter+json" ], "accepts" : [ "application/alto-costmapfilter+json" ],
"uses" : [ "my-default-network-map" ], "uses" : [ "my-default-network-map" ],
"capabilities" : { "capabilities" : {
"max-cost-types" : 2, "max-cost-types" : 2,
"cost-type-names" : [ "num-routingcost", "cost-type-names" : [ "num-routingcost",
"num-hopcount" ], "num-hopcount" ],
... ...
} }
A legacy client will ignore the "max-cost-types" capability, and will A legacy ALTO client will ignore the "max-cost-types" capability, and
send a request with the input parameter "cost-type" describing the will send a request with the input parameter "cost-type" describing
desired cost metric, as defined in [RFC7285]. The ALTO Server will the desired cost metric, as defined in [RFC7285]. The ALTO Server
return a single-valued legacy Cost Map. will return a single-valued legacy Cost Map.
However, a multi-cost-aware client will realize that this resource However, a multi-cost-aware ALTO client will realize that this
supports the multi-cost extensions, and can send a POST request with resource supports the multi-cost extensions, and can send a POST
the new input parameter "multi-cost-types", whose value is an array request with the new input parameter "multi-cost-types", whose value
of cost types. Because the request has the "multi-cost-types" is an array of cost types. Because the request has the "multi-cost-
parameter (rather than the "cost-type" parameter defined in the base types" parameter (rather than the "cost-type" parameter defined in
protocol), the server realizes that the client also supports the the base protocol), the Server realizes that the ALTO client also
extensions in this document, and hence responds with a Multi Cost supports the extensions in this document, and hence responds with a
Map, with the costs in the order listed in "multi-cost-types". Multi Cost Map, with the costs in the order listed in "multi-cost-
types".
3.4. Endpoint Cost Service Resources 3.4. Endpoint Cost Service Resources
This document uses the technique described in Section 3.3 to extend This document uses the technique described in Section 3.3 to extend
the Endpoint Cost Service to return array-valued costs to clients who the Endpoint Cost Service to return array-valued costs to ALTO
also are aware of these extensions. clients who also are aware of these extensions.
3.5. Full Cost Map Resources 3.5. Full Cost Map Resources
Full Cost Map resources are GET-mode requests, with no capabilities Full Cost Map resources are GET-mode requests, with no capabilities
other than the name of the cost type they return. Therefore unless other than the name of the cost type they return. Therefore unless
we create a new media type for array-valued Cost Maps, it is not we create a new media type for array-valued Cost Maps, it is not
possible to define a Multi-Cost Full Cost Map resource so that multi- possible to define a Multi-Cost Full Cost Map resource so that multi-
cost-aware clients can recognize it and legacy clients will ignore cost-aware ALTO clients can recognize it and legacy ALTO clients will
it. Indeed, the response for a Full Cost Map conveying multiple cost ignore it. Indeed, the response for a Full Cost Map conveying
types would include a "meta" field that would itself include a "cost- multiple cost types would include a "meta" field that would itself
type" field, that would list several values corresponding to the cost include a "cost-type" field, that would list several values
types of the cost map. A legacy client would not be able to corresponding to the cost types of the cost map. A legacy ALTO
understand this list. It would not know what the cost type of the client would not be able to understand this list. It would not know
map is and neither would it be able to interpret the cost values what the cost type of the map is and neither would it be able to
array provided by a Multi-Cost full maps. interpret the cost values array provided by a Multi-Cost full maps.
However {11.3.2.3} of [RFC7285] requires a Filtered Cost Map to However {11.3.2.3} of [RFC7285] requires a Filtered Cost Map to
return the entire Cost Map if the client omits the source and return the entire Cost Map if the ALTO client omits the source and
destination PIDs. Hence a client can use an extended Filtered Cost destination PIDs. Hence an ALTO client can use an extended Filtered
Map resource to get a full Multi Cost Map. Cost Map resource to get a full Multi Cost Map.
3.6. Extended Constraint Tests 3.6. Extended Constraint Tests
[RFC7285] defines a simple constraint test capability for Filtered [RFC7285] defines a simple constraint test capability for Filtered
Cost Maps and Endpoint Cost Services. If a resource supports Cost Maps and Endpoint Cost Services. If a resource supports
constraints, the server restricts the response to costs that satisfy constraints, the Server restricts the response to costs that satisfy
a list of simple predicates provided by the client. For example, if a list of simple predicates provided by the ALTO client. For
the client gives the constraints example, if the ALTO client gives the constraints
"constraints": ["ge 10", "le 20"] "constraints": ["ge 10", "le 20"]
Then the server only returns costs in the range [10,20]. Then the Server only returns costs in the range [10,20].
To be useful with multi-cost requests, the constraint tests require To be useful with multi-cost requests, the constraint tests require
several extensions. several extensions.
3.6.1. Extended constraint predicates 3.6.1. Extended constraint predicates
First, because a multi-cost request involves more than one cost First, because a multi-cost request involves more than one cost
metric, the simple predicates must be extended to specify the metric metric, the simple predicates must be extended to specify the metric
to test. Therefore we extend the predicate syntax to "[##] op to test. Therefore we extend the predicate syntax to "[##] op
value", where "##" is the index of a cost metric in this multi-cost value", where "##" is the index of a cost metric in this multi-cost
request. request.
3.6.2. Extended logical combination of predicates 3.6.2. Extended logical combination of predicates
Second, once multiple cost metrics are involved, the "AND" of simple Second, once multiple cost metrics are involved, the "AND" of simple
predicates is no longer sufficient. To be useful, clients must be predicates is no longer sufficient. To be useful, Clients must be
able to express "OR" tests. Hence we add a new field, "or- able to express "OR" tests. Hence we add a new field, "or-
constraints", to the client request. The value is an array of arrays constraints", to the Client request. The value is an array of arrays
of simple predicates, and represents the OR of ANDs of those of simple predicates, and represents the OR of ANDs of those
predicates. predicates.
Thus, the following request tells the server to limit its response to Thus, the following request tells the Server to limit its response to
cost points with "routingcost" <= 100 AND "hopcount" <= 2, OR else cost points with "routingcost" <= 100 AND "hopcount" <= 2, OR else
"routingcost" <= 10 AND "hopcount" <= 6: "routingcost" <= 10 AND "hopcount" <= 6:
{ {
"multi-cost-types": [ "multi-cost-types": [
{"cost-metric": "routingcost", "cost-mode": "numerical"}, {"cost-metric": "routingcost", "cost-mode": "numerical"},
{"cost-metric": "hopcount", "cost-mode": "numerical"} {"cost-metric": "hopcount", "cost-mode": "numerical"}
], ],
"or-constraints": [ "or-constraints": [
["[0] le 100", "[1] le 2"], ["[0] le 100", "[1] le 2"],
["[0] le 10", "[1] le 6"] ["[0] le 10", "[1] le 6"]
], ],
"pids": {...} "pids": {...}
} }
3.6.3. Testable Cost Types in constraints 3.6.3. Testable Cost Types in constraints
Finally, a client may want to test a cost type whose actual value is Finally, a Client may want to test a cost type whose actual value is
irrelevant, as long as it satisfies the tests. For example, a client irrelevant, as long as it satisfies the tests. For example, a Client
may want the value of the cost metric "routingcost" for all PID pairs may want the value of the cost metric "routingcost" for all PID pairs
that satisfy constraints on the metric "hopcount", without needing that satisfy constraints on the metric "hopcount", without needing
the actual value of "hopcount". the actual value of "hopcount".
For example, the following request tells the server to return just For example, the following request tells the Server to return just
"routingcost" for those source and destination pairs for which "routingcost" for those source and destination pairs for which
"hopcount" is <= 6: "hopcount" is <= 6:
{ {
"multi-cost-types": [ "multi-cost-types": [
{"cost-metric": "routingcost", "cost-mode": "numerical"}, {"cost-metric": "routingcost", "cost-mode": "numerical"},
], ],
"testable-cost-types": [ "testable-cost-types": [
{"cost-metric": "hopcount", "cost-mode": "numerical"}, {"cost-metric": "hopcount", "cost-mode": "numerical"},
], ],
skipping to change at page 9, line 48 skipping to change at page 9, line 48
} }
In this example, "[0]" means the constraint applies to "hopcount" In this example, "[0]" means the constraint applies to "hopcount"
because that is the first cost type in the "testable-cost-types" because that is the first cost type in the "testable-cost-types"
parameter. (If "testable-cost-types" is omitted, it is assumed to be parameter. (If "testable-cost-types" is omitted, it is assumed to be
the same as "multi-cost-types".) the same as "multi-cost-types".)
3.6.4. Testable Cost Type Names in IRD capabilities 3.6.4. Testable Cost Type Names in IRD capabilities
In [RFC7285], when a resource's capability "constraints" is true, the In [RFC7285], when a resource's capability "constraints" is true, the
server accepts constraints on all the cost types listed in the "cost- Server accepts constraints on all the cost types listed in the "cost-
type-names" capability. However, some ALTO Servers may not be type-names" capability. However, some ALTO Servers may not be
willing to allow contraint tests on all available cost metrics. willing to allow contraint tests on all available cost metrics.
Therefore the Multi-Cost ALTO protocol extension defines the Therefore the Multi-Cost ALTO protocol extension defines the
capability field "testable-cost-type-names". Like "cost-type-names", capability field "testable-cost-type-names". Like "cost-type-names",
it is an array of cost type names. If present, that resource only it is an array of cost type names. If present, that resource only
allows constraint tests on the cost types in that list. "testable- allows constraint tests on the cost types in that list. "testable-
cost-type-names" MUST be a subset of "cost-type-names". cost-type-names" MUST be a subset of "cost-type-names".
3.6.5. Legacy client issues 3.6.5. Legacy ALTO Client issues
While a multi-cost-aware client will recognize the "testable-cost- While a multi-cost-aware Client will recognize the "testable-cost-
type-names" field, and will honor those restrictions, a legacy client type-names" field, and will honor those restrictions, a legacy Client
will not. Hence a legacy may send a request with a constraint test will not. Hence a legacy may send a request with a constraint test
on any of the cost types listed in "cost-type-names". on any of the cost types listed in "cost-type-names".
To avoid that problem, the "testable-cost-type-names" and "cost- To avoid that problem, the "testable-cost-type-names" and "cost-
constraints" fields are mutually exclusive: a resource may define one constraints" fields are mutually exclusive: a resource may define one
or the other capability, but MUST NOT define both. Thus a resource or the other capability, but MUST NOT define both. Thus a resource
that does not allow constraint tests on all cost metrics will set that does not allow constraint tests on all cost metrics will set
"testable-cost-type-names" to the testable metrics, and will set "testable-cost-type-names" to the testable metrics, and will set
"cost-constraints" to "false". A multi-cost-aware client will "cost-constraints" to "false". A multi-cost-aware Client will
recognize the "testable-cost-type-names" field, and will realize that recognize the "testable-cost-type-names" field, and will realize that
its existence means the resource does allow (limited) contraint its existence means the resource does allow (limited) contraint
tests, while a legacy client will think that resource does not allow tests, while a legacy Client will think that resource does not allow
constraint tests at all. To allow legacy clients to use constraint constraint tests at all. To allow legacy Clients to use constraint
tests, the ALTO Server MAY define an additional resource with "cost- tests, the ALTO Server MAY define an additional resource with "cost-
constraints" set to "true" and "cost-type-names" set to the metrics constraints" set to "true" and "cost-type-names" set to the metrics
which can be tested. which can be tested.
In the IRD example below, the resource "filtered-cost-map-extended" In the IRD example below, the resource "filtered-cost-map-extended"
provides values for three metrics: "num-routingcost", "num-hopcount" provides values for three metrics: "num-routingcost", "num-hopcount"
and "num-bwscore". The capability "testable-cost-type-names" and "num-bwscore". The capability "testable-cost-type-names"
indicates that the server only allows constraints on "routingcost" indicates that the Server only allows constraints on "routingcost"
and "hopcount". A multi-cost capable client will see this and "hopcount". A multi-cost capable Client will see this
capability, and will limit its constraint tests to those metrics. capability, and will limit its constraint tests to those metrics.
Because capability "cost-constraints" is false (by default), a legacy Because capability "cost-constraints" is false (by default), a legacy
client will not use constraint tests on this resource at all. Client will not use constraint tests on this resource at all.
The second resource, "filtered-multicost-map", is similar to the The second resource, "filtered-multicost-map", is similar to the
first, except that all the metrics it returns are testable. first, except that all the metrics it returns are testable.
Therefore it sets "cost-constraints" to "true", and does not set the Therefore it sets "cost-constraints" to "true", and does not set the
"testable-cost-type-names" field. A legacy client that needs a "testable-cost-type-names" field. A legacy Client that needs a
constraint test will use this resource rather than the first. A constraint test will use this resource rather than the first. A
multi-cost-aware client that does not need to retrieve the "num- multi-cost-aware Client that does not need to retrieve the "num-
bwscore" metric may use either resource. bwscore" metric may use either resource.
"filtered-cost-map-extended" : { "filtered-cost-map-extended" : {
"uri" : "http://alto.example.com/multi/extn/costmap/filtered", "uri" : "http://alto.example.com/multi/extn/costmap/filtered",
"media-types" : [ "application/alto-costmap+json" ], "media-types" : [ "application/alto-costmap+json" ],
"accepts" : [ "application/alto-costmapfilter+json" ], "accepts" : [ "application/alto-costmapfilter+json" ],
"uses" : [ "my-default-network-map" ], "uses" : [ "my-default-network-map" ],
"capabilities" : { "capabilities" : {
"max-cost-types" : 3, "max-cost-types" : 3,
"cost-type-names" : [ "num-routingcost", "cost-type-names" : [ "num-routingcost",
skipping to change at page 12, line 39 skipping to change at page 12, line 39
testable-cost-type-names: If present, the resource allows constraint testable-cost-type-names: If present, the resource allows constraint
tests, but only on the cost type names in this array. Each name tests, but only on the cost type names in this array. Each name
in "testable-cost-type-names" MUST also be in "cost-type-names". in "testable-cost-type-names" MUST also be in "cost-type-names".
If "testable-cost-type-names" is present, the "cost-constraints" If "testable-cost-type-names" is present, the "cost-constraints"
capability MUST NOT be "true", and if "cost-constraints" is capability MUST NOT be "true", and if "cost-constraints" is
"true", "testable-cost-type-names" MUST NOT be present. Thus if "true", "testable-cost-type-names" MUST NOT be present. Thus if
"cost-constraints" is "true", the resource MUST accept constraint "cost-constraints" is "true", the resource MUST accept constraint
tests on any cost type in "cost-type-names". tests on any cost type in "cost-type-names".
As discussed in Section 3.6.4, this capability is useful when a As discussed in Section 3.6.4, this capability is useful when a
server is unable or unwilling to implement constraint tests on all Server is unable or unwilling to implement constraint tests on all
cost types. As discussed in Section 3.6.5, "testable-cost-type- cost types. As discussed in Section 3.6.5, "testable-cost-type-
names" and "cost-constraints" are mutually exclusive to prevent names" and "cost-constraints" are mutually exclusive to prevent
legacy clients from issuing constraint tests on untestable cost legacy Clients from issuing constraint tests on untestable cost
types. types.
4.1.2. Accept Input Parameters 4.1.2. Accept Input Parameters
The ReqFilteredCostMap object in {11.3.2.3} of [RFC7285] is extended The ReqFilteredCostMap object in {11.3.2.3} of [RFC7285] is extended
as follows: as follows:
object { object {
[CostType cost-type;] [CostType cost-type;]
[CostType multi-cost-types<1..*>;] [CostType multi-cost-types<1..*>;]
[CostType testable-cost-types<1..*>;] [CostType testable-cost-types<1..*>;]
[JSONString constraints<0..*>;] [JSONString constraints<0..*>;]
[JSONString or-constraints<0..*><0..*>;] [JSONString or-constraints<1..*><1..*>;]
PIDFilter pids; PIDFilter pids;
} ReqFilteredCostMap; } ReqFilteredCostMap;
object { object {
PIDName srcs<0..*>; PIDName srcs<0..*>;
PIDName dsts<0..*>; PIDName dsts<0..*>;
} PIDFilter; } PIDFilter;
cost-type: As defined in {11.3.2.3} of [RFC7285], with the cost-type: As defined in {11.3.2.3} of [RFC7285], with the
additional requirement that the client MUST specify either "cost- additional requirement that the Client MUST specify either "cost-
type" or "multi-cost-types", but MUST NOT specify both. type" or "multi-cost-types", but MUST NOT specify both.
multi-cost-types: If present, the ALTO Server MUST return array- multi-cost-types: If present, the ALTO Server MUST return array-
valued costs for the cost types in this list. For each entry, the valued costs for the cost types in this list. For each entry, the
"cost-metric" and "cost-mode" fields MUST match one of the "cost-metric" and "cost-mode" fields MUST match one of the
supported cost types indicated in member "cost-type-names" of this supported cost types indicated in member "cost-type-names" of this
resource's "capabilities" field (Section 4.1.1). The client MUST resource's "capabilities" field (Section 4.1.1). The Client MUST
NOT use this field unless this resource's "max-cost-types" NOT use this field unless this resource's "max-cost-types"
capability exists and has a value greater than 0. This field MUST capability exists and has a value greater than 0. This field MUST
NOT have more than "max-cost-types" cost types. The client MUST NOT have more than "max-cost-types" cost types. The Client MUST
specify either "cost-type" or "multi-cost-types", but MUST NOT specify either "cost-type" or "multi-cost-types", but MUST NOT
specify both. specify both.
Note that if "multi-cost-types" has one cost type, the values in Note that if "multi-cost-types" has one cost type, the values in
the cost map will be arrays with one value. the cost map will be arrays with one value.
testable-cost-types: A list of cost types used for extended testable-cost-types: A list of cost types used for extended
constraint tests, as described for the "constraints" and "or- constraint tests, as described for the "constraints" and "or-
constraints" parameters. These cost types must either be a subset constraints" parameters. These cost types must either be a subset
of the cost types in the resource's "testable-cost-type-names" of the cost types in the resource's "testable-cost-type-names"
capability (Section 4.1.1), or else, if the resource's capability capability (Section 4.1.1), or else, if the resource's capability
"cost-constraints" is true, a subset of the cost types in the "cost-constraints" is true, a subset of the cost types in the
resource's "cost-type-names" capability resource's "cost-type-names" capability.
If "testable-cost-types" is omitted, it is assumed to have the If "testable-cost-types" is omitted, it is assumed to have the
cost types in "multi-cost-types" or "cost-type". cost types in "multi-cost-types" or "cost-type".
This feature is useful when a client wants to test a cost type This feature is useful when a Client wants to test a cost type
whose actual value is irrelevant, as long as it satisfies the whose actual value is irrelevant, as long as it satisfies the
tests. For example, a client may want the cost metric tests. For example, a Client may want the cost metric
"routingcost" for those PID pairs whose "hopcount" is less than "routingcost" for those PID pairs whose "hopcount" is less than
10. The exact hopcount does not matter. 10. The exact hopcount does not matter.
constraints: If this resource's "max-cost-types" capability constraints: If this resource's "max-cost-types" capability
(Section 4.1.1) has the value 0 (or is not defined), this (Section 4.1.1) has the value 0 (or is not defined), this
parameter is as defined in {11.3.2.3} of [RFC7285]: an array of parameter is as defined in {11.3.2.3} of [RFC7285]: an array of
constraint tests related to each other by a logical AND. In this constraint tests related to each other by a logical AND. In this
case it MUST NOT be specified unless the resource's "cost- case it MUST NOT be specified unless the resource's "cost-
constraints" capability is "true". constraints" capability is "true".
If this resource's "max-cost-types" capability has a value greater If this resource's "max-cost-types" capability has a value greater
than 0, then a "constraints" parameter with the array of extended than 0, then this parameter is an array of extended constraint
predicates [P1, P2, ...] is equivalent to an "or-constraints" predicates as defined below and related to each other by a logical
parameter with the value [[P1, P2, ...]]. In this case, the AND. In this case, it MAY be specified if the resource allows
"constraints" parameter MUST NOT be specified if the "or- constraint tests (the resource's "cost-constraints" capability is
constraints" parameter is specified. "true" or its "testable-cost-type-names" capability is not empty).
or-constraints: A JSONArray of JSONArrays of JSONStrings, where each
string is an extended constraint predicate as defined below. The
"or-constraint" tests are interpreted as the logical OR of ANDs of
predicates. That is, the ALTO Server should return a cost point
only if it satisfies all constraints in any one of the sub-arrays.
This parameter MAY be specified if this resource's "max-cost-
types" capability is defined with a value greater than 0
(Section 4.1.1), and if the resource allows constraint tests (the
resource's "cost-constraints" capability is "true" or its
"testable-cost-type-names" capability is not empty). Otherwise
this parameter MUST NOT be specified.
This parameter MUST NOT be specified if the "constraints" This parameter MUST NOT be specified if the "or-constraints"
parameter is specified. parameter is specified.
An extended constraint predicate consists of two or three entities An extended constraint predicate consists of two or three entities
separated by white space: (1) an optional cost type index, of the separated by white space: (1) an optional cost type index, of the
form "[#]", with default value "[0]", (2) a required operator, and form "[#]", with default value "[0]", (2) a required operator, and
(3) a required target value. The operator and target value are as (3) a required target value. The operator and target value are as
defined in {11.3.2.3} of [RFC7285]. The cost type index, i, defined in {11.3.2.3} of [RFC7285]. The cost type index, i,
specifies the cost type to test. If the "testable-cost-type" specifies the cost type to test. If the "testable-cost-type"
parameter is present, the test applies to the i'th cost type in parameter is present, the test applies to the i'th cost type in
"testable-cost-types", starting with index 0. Otherwise if the "testable-cost-types", starting with index 0. Otherwise if the
"multi-cost-types" parameter is present, the test applies to the "multi-cost-types" parameter is present, the test applies to the
i'th cost type in that array. If neither parameters are present, i'th cost type in that array. If neither parameters are present,
the test applies to the cost type in the "cost-type" parameter, in the test applies to the cost type in the "cost-type" parameter, in
which this case the index MUST be 0. Regardless of how the tested which case the index MUST be 0. Regardless of how the tested cost
cost type is selected, it MUST be in the resource's "testable- type is selected, it MUST be in the resource's "testable-cost-
cost-type-names" capability, or, if not present, in the "cost- type-names" capability, or, if not present, in the "cost-type-
type-names" capability. names" capability.
As an example, suppose "multi-cost-types" has the single element As an example, suppose "multi-cost-types" has the single element
"routingcost", "testable-cost-types" has the single element "routingcost", "testable-cost-types" has the single element
"hopcount", and "or-constraints" has the single element "[0] le "hopcount", and "constraints" has the single element "[0] le 5".
5". This is equivalent to the database query "SELECT and provide This is equivalent to the database query "SELECT and provide
routingcost WHERE hopcount <= 5". routingcost WHERE hopcount <= 5".
Note that the index is optional, so a constraint test as defined Note that the index is optional, so a constraint test as defined
in {11.3.2.3}, such as "le 10", is equivalent to "[0] le 10". in {11.3.2.3}, such as "le 10", is equivalent to "[0] le 10".
Thus legacy constraint tests are also legal extended constraint Thus legacy constraint tests are also legal extended constraint
tests. tests.
Note that a "constraints" parameter with the array of extended
predicates [P1, P2, ...] is equivalent to an "or-constraints"
parameter as defined below, with the value [[P1, P2, ...]].
or-constraints: A JSONArray of JSONArrays of JSONStrings, where each
string is an extended constraint predicate as defined above. The
"or-constraint" tests are interpreted as the logical OR of ANDs of
predicates. That is, the ALTO Server should return a cost point
only if it satisfies all constraints in any one of the sub-arrays.
This parameter MAY be specified if this resource's "max-cost-
types" capability is defined with a value greater than 0
(Section 4.1.1), and if the resource allows constraint tests (the
resource's "cost-constraints" capability is "true" or its
"testable-cost-type-names" capability is not empty). Otherwise
this parameter MUST NOT be specified.
This parameter MUST NOT be specified if the "constraints"
parameter is specified.
This parameter MUST NOT contain any empty array of AND predicates.
As an example, suppose "multi-cost-types" has the two elements
"routingcost" and "bandwidthscore", and "testable-cost-types" has
the two elements "routingcost" and "hopcount", and "or-
constraints" has the two elements ["[0] le 100", "[1] le 2"] and
["[0] le 10", "[1] le 6"]. This is equivalent to the database
query: "SELECT and provide routingcost and bandwidth score WHERE
("routingcost" <= 100 AND "hopcount" <= 2) OR else ("routingcost"
<= 10 AND "hopcount" <= 6)".
Note that an empty array of AND predicates is equivalent to a
constraint that is allways "true". An OR combination including
such a constraint would be allways "true" and thus useless.
Also note that if the "max-cost-types" capability has a value Also note that if the "max-cost-types" capability has a value
greater than 0, a client MAY use the "or-constraints" parameter greater than 0, a Client MAY use the "or-constraints" parameter
together with the "cost-type" parameter. That is, if the client together with the "cost-type" parameter. That is, if the Client
and server are both aware of the extensions in this document, a and Server are both aware of the extensions in this document, a
client MAY use an "OR" test for a single-valued cost request. Client MAY use an "OR" test for a single-valued cost request.
pids, srcs, dsts: As defined in {11.3.2.3} of [RFC7285]. pids, srcs, dsts: As defined in {11.3.2.3} of [RFC7285].
4.1.3. Response 4.1.3. Response
If the client specifies the "cost-type" input parameter, the response If the Client specifies the "cost-type" input parameter, the response
is exactly as defined in {11.2.3.6} of [RFC7285]. If the client is exactly as defined in {11.2.3.6} of [RFC7285]. If the Client
provides the "multi-cost-types" instead, then the response is changed provides the "multi-cost-types" instead, then the response is changed
as follows: as follows:
o In "meta", the field "cost-type" is replaced with the field o In "meta", the field "cost-type" is provided with a dummy value.
"multi-cost-types", with the same value as the "multi-cost-types" Instead, the field "multi-cost-types" is added with the same value
input parameter. as the "multi-cost-types" input parameter.
o The costs are JSONArrays, instead of JSONNumbers. All arrays have o The costs are JSONArrays, instead of JSONNumbers. All arrays have
the same cardinality as the "multi-cost-types" input parameter, the same cardinality as the "multi-cost-types" input parameter,
and contain the cost type values in that order. If a cost type is and contain the cost type values in that order. If a cost type is
not available for a particular source and destination, the ALTO not available for a particular source and destination, the ALTO
Server MUST use the JSON "null" value for that array element. If Server MUST use the JSON "null" value for that array element. If
none of the cost types are available for a particular source and none of the cost types are available for a particular source and
destination, the ALTO Server MAY omit the entry for that source destination, the ALTO Server MAY omit the entry for that source
and destination. and destination.
skipping to change at page 16, line 21 skipping to change at page 17, line 10
4.2.2. Accept Input Parameters 4.2.2. Accept Input Parameters
The ReqEndpointCostMap object in {11.5.1.3} of [RFC7285] is extended The ReqEndpointCostMap object in {11.5.1.3} of [RFC7285] is extended
as follows: as follows:
object { object {
[CostType cost-type;] [CostType cost-type;]
[CostType multi-cost-types<1..*>;] [CostType multi-cost-types<1..*>;]
[CostType testable-cost-types<1..*>;] [CostType testable-cost-types<1..*>;]
[JSONString constraints<0..*>;] [JSONString constraints<0..*>;]
[JSONString or-constraints<0..*><0..*>;] [JSONString or-constraints<1..*><1..*>;]
EndpointFilter endpoints; EndpointFilter endpoints;
} ReqFilteredCostMap; } ReqFilteredCostMap;
object { object {
[TypedEndpointAddr srcs<0..*>;] [TypedEndpointAddr srcs<0..*>;]
[TypedEndpointAddr dsts<0..*>;] [TypedEndpointAddr dsts<0..*>;]
} EndpointFilter; } EndpointFilter;
cost-type: As defined in {11.5.1.3} of [RFC7285], with the cost-type: As defined in {11.5.1.3} of [RFC7285], with the
additional requirement that the client MUST specify either "cost- additional requirement that the Client MUST specify either "cost-
type" or "multi-cost-types", but MUST NOT specify both. type" or "multi-cost-types", but MUST NOT specify both.
multi-cost-types: If present, the ALTO Server MUST return array- multi-cost-types: If present, the ALTO Server MUST return array-
valued costs for the cost types in this list. For each entry, the valued costs for the cost types in this list. For each entry, the
"cost-metric" and "cost-mode" fields MUST match one of the "cost-metric" and "cost-mode" fields MUST match one of the
supported cost types indicated in this resource's "capabilities" supported cost types indicated in this resource's "capabilities"
field (Section 4.2.1). The client MUST NOT use this field unless field (Section 4.2.1). The Client MUST NOT use this field unless
this resource's "max-cost-types" capability exists and has a value this resource's "max-cost-types" capability exists and has a value
greater than 0. This field MUST NOT have more than "max-cost- greater than 0. This field MUST NOT have more than "max-cost-
types" cost types. The client MUST specify either "cost-type" or types" cost types. The Client MUST specify either "cost-type" or
"multi-cost-types", but MUST NOT specify both. "multi-cost-types", but MUST NOT specify both.
Note that if "multi-cost-types" has one cost type, the values in Note that if "multi-cost-types" has one cost type, the values in
the cost map will be arrays with one value. the cost map will be arrays with one value.
testable-cost-types, constraints, or-constraints: Defined testable-cost-types, constraints, or-constraints: Defined
equivalently to the corresponding input parameters for an extended equivalently to the corresponding input parameters for an extended
Filtered Cost Map (Section 4.1.2). Filtered Cost Map (Section 4.1.2).
endpoints, srcs, dsts: As defined in {11.5.1.3} of [RFC7285]. endpoints, srcs, dsts: As defined in {11.5.1.3} of [RFC7285].
4.2.3. Response 4.2.3. Response
The extensions to the Endpoint Cost Service response are similar to The extensions to the Endpoint Cost Service response are similar to
the extensions to the Filtered Cost Map response (Section 4.1.3). the extensions to the Filtered Cost Map response (Section 4.1.3).
Specifically, if the client specifies the "cost-type" input Specifically, if the Client specifies the "cost-type" input
parameter, the response is exactly as defined in {11.5.1.6} of parameter, the response is exactly as defined in {11.5.1.6} of
[RFC7285]. If the client provides the "multi-cost-types" instead, [RFC7285]. If the Client provides the "multi-cost-types" instead,
then the response is changed as follows: then the response is changed as follows:
o In "meta", the field "cost-type" is replaced with the field o In "meta", the field "cost-type" is provided with a dummy value.
"multi-cost-types", with the same value as the "multi-cost-types" Instead, the field "multi-cost-types" is added with the same value
input parameter. as the "multi-cost-types" input parameter.
o The costs are JSONArrays, instead of JSONNumbers. All arrays have o The costs are JSONArrays, instead of JSONNumbers. All arrays have
the same cardinality as the "multi-cost-types" input parameter, the same cardinality as the "multi-cost-types" input parameter,
and contain the cost type values in that order. If a cost type is and contain the cost type values in that order. If a cost type is
not available for a particular source and destination, the ALTO not available for a particular source and destination, the ALTO
Server MUST use the JSON "null" value for that array element. If Server MUST use the JSON "null" value for that array element. If
none of the cost types are available for a particular source and none of the cost types are available for a particular source and
destination, the ALTO Server MAY omit the entry for that source destination, the ALTO Server MAY omit the entry for that source
and destination. and destination.
skipping to change at page 20, line 33 skipping to change at page 21, line 15
Content-Type: application/alto-costmap+json Content-Type: application/alto-costmap+json
Content-Length: ### Content-Length: ###
{ {
"meta" : { "meta" : {
"dependent-vtags" : [ "dependent-vtags" : [
{"resource-id": "my-default-network-map", {"resource-id": "my-default-network-map",
"tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e" "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e"
} }
], ],
"cost-type" : {},
"multi-cost-types" : [ "multi-cost-types" : [
{"cost-mode": "numerical", "cost-metric": "routingcost"}, {"cost-mode": "numerical", "cost-metric": "routingcost"},
{"cost-mode": "numerical", "cost-metric": "hopcount"} {"cost-mode": "numerical", "cost-metric": "hopcount"}
] ]
} }
} }
"cost-map" : { "cost-map" : {
"PID1": { "PID1":[1,0], "PID2":[4,3], "PID3":[10,2] }, "PID1": { "PID1":[1,0], "PID2":[4,3], "PID3":[10,2] },
"PID2": { "PID1":[15,5], "PID2":[1,0], "PID3":[null,9] }, "PID2": { "PID1":[15,5], "PID2":[1,0], "PID3":[null,9] },
"PID3": { "PID1":[20,12], "PID2":[null,1], "PID3":[1,0] } "PID3": { "PID1":[20,12], "PID2":[null,1], "PID3":[1,0] }
skipping to change at page 21, line 35 skipping to change at page 22, line 35
Content-Type: application/alto-costmap+json Content-Type: application/alto-costmap+json
Content-Length: ### Content-Length: ###
{ {
"meta" : { "meta" : {
"dependent-vtags" : [ "dependent-vtags" : [
{"resource-id": "my-default-network-map", {"resource-id": "my-default-network-map",
"tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e" "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e"
} }
], ],
"cost-type" : {},
"multi-cost-types" : [ "multi-cost-types" : [
{"cost-mode": "numerical", "cost-metric": "routingcost"}, {"cost-mode": "numerical", "cost-metric": "routingcost"},
{"cost-mode": "numerical", "cost-metric": "hopcount"} {"cost-mode": "numerical", "cost-metric": "hopcount"}
] ]
} }
"cost-map" : { "cost-map" : {
"PID1": { "PID1": [1,0], "PID3": [10,5] }, "PID1": { "PID1": [1,0], "PID3": [10,5] },
"PID2": { "PID2": [1,0] } "PID2": { "PID2": [1,0] }
} }
} }
5.4. Multi-Cost Filtered Cost Map: Example #3 5.4. Multi-Cost Filtered Cost Map: Example #3
This example uses extended constraints to limit the response to cost This example uses extended constraints to limit the response to cost
points with ("routingcost" <= 10 and "hopcount" <= 2), or else points with ("routingcost" <= 10 and "hopcount" <= 2), or else
("routingcost" <= 3 and "hopcount" <= 6). Unlike the previous ("routingcost" <= 3 and "hopcount" <= 6). Unlike the previous
example, the client is only interested in the "routingcost" cost example, the Client is only interested in the "routingcost" cost
type, and uses the "cost-type" parameter instead of "multi-cost- type, and uses the "cost-type" parameter instead of "multi-cost-
types" to tell the server to return scalar costs instead of array types" to tell the Server to return scalar costs instead of array
costs: costs:
POST /multi/multicostmap/filtered HTTP/1.1 POST /multi/multicostmap/filtered HTTP/1.1
Host: alto.example.com Host: alto.example.com
Accept: application/alto-costmap+json,application/alto-error+json Accept: application/alto-costmap+json,application/alto-error+json
Content-Type: application/alto-costmapfilter+json Content-Type: application/alto-costmapfilter+json
Content-Length: ### Content-Length: ###
{ {
"cost-type" : { "cost-type" : {
skipping to change at page 23, line 31 skipping to change at page 24, line 31
"PID2": { "PID2": 1 }, "PID2": { "PID2": 1 },
"PID3": { "PID3": 1 } "PID3": { "PID3": 1 }
} }
} }
5.5. Multi-Cost Filtered Cost Map: Example #4 5.5. Multi-Cost Filtered Cost Map: Example #4
This example uses extended constraints to limit the response to cost This example uses extended constraints to limit the response to cost
points with ("routingcost" <= 10 and "hopcount" <= 2), or else points with ("routingcost" <= 10 and "hopcount" <= 2), or else
("routingcost" <= 3 and "hopcount" <= 6). In this example, the ("routingcost" <= 3 and "hopcount" <= 6). In this example, the
client is interested in the "routingcost" and "bandwidthscore" cost Client is interested in the "routingcost" and "bandwidthscore" cost
metrics, but not in the "hopcount" metric: metrics, but not in the "hopcount" metric:
POST /multi/extn/costmap/filtered HTTP/1.1 POST /multi/extn/costmap/filtered HTTP/1.1
Host: alto.example.com Host: alto.example.com
Accept: application/alto-costmap+json,application/alto-error+json Accept: application/alto-costmap+json,application/alto-error+json
Content-Type: application/alto-costmapfilter+json Content-Type: application/alto-costmapfilter+json
Content-Length: ### Content-Length: ###
{ {
"multi-cost-types" : [ "multi-cost-types" : [
skipping to change at page 24, line 41 skipping to change at page 26, line 15
Content-Type: application/alto-costmap+json Content-Type: application/alto-costmap+json
Content-Length: ### Content-Length: ###
{ {
"meta" : { "meta" : {
"dependent-vtags" : [ "dependent-vtags" : [
{"resource-id": "my-default-network-map", {"resource-id": "my-default-network-map",
"tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e" "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e"
} }
], ],
"cost-type" : {},
"multi-cost-types" : [ "multi-cost-types" : [
{"cost-mode": "numerical", "cost-metric": "routingcost"}, {"cost-mode": "numerical", "cost-metric": "routingcost"},
{"cost-mode": "numerical", "cost-metric": "bandwidthscore"} {"cost-mode": "numerical", "cost-metric": "bandwidthscore"}
] ]
} }
"cost-map" : { "cost-map" : {
"PID1": { "PID1": [1,16] "PID3": [10,19] }, "PID1": { "PID1": [1,16] "PID3": [10,19] },
"PID2": { "PID2": [1,8] }, "PID2": { "PID2": [1,8] },
"PID3": { "PID3": [1,19] } "PID3": { "PID3": [1,19] }
} }
skipping to change at page 26, line 28 skipping to change at page 28, line 8
IANA considerations. IANA considerations.
7. Privacy And Security Considerations 7. Privacy And Security Considerations
This document does introduce any privacy or security issues not This document does introduce any privacy or security issues not
already present in the ALTO protocol. already present in the ALTO protocol.
8. Acknowledgements 8. Acknowledgements
The authors would like to thank Richard Alimi, Fred Baker, Dhruv The authors would like to thank Richard Alimi, Fred Baker, Dhruv
Dhodi, Vijay Gurbani, Gao Kai, Dave Mac Dysan, Young Lee, Richard Dhodi, Vijay Gurbani, Gao Kai, Dave Mac Dysan, Young Lee, Hans
Yang, Qiao Xiang and Wang Xin for fruitful discussions and feedback Seidel, Richard Yang, Qiao Xiang and Wang Xin for fruitful
on this document and previous versions. discussions and feedback on this document and previous versions.
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
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