ALTO WG G. Bernstein Internet-Draft Grotto Networking Intended status: Standards Track S. Chen Expires: January 4, 2018 Tongji University K. Gao Tsinghua University Y. Lee Huawei W. Roome M. Scharf Nokia Y. Yang Yale University J. Zhang Tongji University July 3, 2017 ALTO Extension: Path Vector Cost Mode draft-ietf-alto-path-vector-01.txt Abstract The Application-Layer Traffic Optimization (ALTO) protocol [RFC7285] has defined several resources and services to provide clients with basic network information. However, the base ALTO protocol and latest extensions only provide end-to-end metrics, which are insufficient to satisfy the demands of solving more complex network optimization problems. This document introduces an extension to the base ALTO protocol, namely the path-vector extension, which allows ALTO clients to query information such as capacity regions for a given set of flows. A non-normative example called multi-flow scheduling is presented to illustrate the limitations of existing ALTO (endpoint) cost maps. After that, details of the extension are defined. 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. Bernstein, et al. Expires January 4, 2018 [Page 1] Internet-Draft ALTO Extension: Path Vector July 2017 Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on January 4, 2018. Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Use Case: Capacity Region for Multi-Flow Scheduling . . . . . 5 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.1. Path Vector . . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Cost Type Extension . . . . . . . . . . . . . . . . . . . 8 4.3. Abstract Network Element Property Map . . . . . . . . . . 8 4.4. New Media Type: multipart/related . . . . . . . . . . . . 8 5. Path-Vector Extension: Basic Data Types . . . . . . . . . . . 9 5.1. Cost Type . . . . . . . . . . . . . . . . . . . . . . . . 9 5.1.1. Cost Metric . . . . . . . . . . . . . . . . . . . . . 9 5.1.2. Cost Mode . . . . . . . . . . . . . . . . . . . . . . 10 5.2. ANE Domain . . . . . . . . . . . . . . . . . . . . . . . 10 5.2.1. Domain Name . . . . . . . . . . . . . . . . . . . . . 10 5.2.2. Domain-Specific Entity Addresses . . . . . . . . . . 10 5.3. Abstract Network Element Name . . . . . . . . . . . . . . 11 5.4. Version Tag . . . . . . . . . . . . . . . . . . . . . . . 11 6. Path-Vector Extension: Services . . . . . . . . . . . . . . . 11 6.1. IRD Extensions . . . . . . . . . . . . . . . . . . . . . 11 Bernstein, et al. Expires January 4, 2018 [Page 2] Internet-Draft ALTO Extension: Path Vector July 2017 6.2. Cost Map Extensions . . . . . . . . . . . . . . . . . . . 12 6.2.1. Media Type . . . . . . . . . . . . . . . . . . . . . 12 6.2.2. Capabilities . . . . . . . . . . . . . . . . . . . . 12 6.2.3. Property-map . . . . . . . . . . . . . . . . . . . . 12 6.2.4. Response . . . . . . . . . . . . . . . . . . . . . . 13 6.3. Filtered Cost Map Extensions . . . . . . . . . . . . . . 13 6.3.1. Media Type . . . . . . . . . . . . . . . . . . . . . 13 6.3.2. Capabilities . . . . . . . . . . . . . . . . . . . . 13 6.3.3. Property-map . . . . . . . . . . . . . . . . . . . . 14 6.3.4. Accept Input Parameters . . . . . . . . . . . . . . . 14 6.3.5. Response . . . . . . . . . . . . . . . . . . . . . . 14 6.4. Endpoint Cost Service Extensions . . . . . . . . . . . . 14 6.4.1. Media Type . . . . . . . . . . . . . . . . . . . . . 15 6.4.2. Capabilities . . . . . . . . . . . . . . . . . . . . 15 6.4.3. Property-map . . . . . . . . . . . . . . . . . . . . 15 6.4.4. Accept Input Parameters . . . . . . . . . . . . . . . 15 6.4.5. Response . . . . . . . . . . . . . . . . . . . . . . 15 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 16 7.1. Workflow . . . . . . . . . . . . . . . . . . . . . . . . 16 7.2. Information Resource Directory Example . . . . . . . . . 17 7.3. Single Query Example # 1 . . . . . . . . . . . . . . . . 18 7.4. Single Query Example # 2 . . . . . . . . . . . . . . . . 20 7.5. Multiple Queries Example . . . . . . . . . . . . . . . . 21 7.5.1. Endpoint Cost Service Example . . . . . . . . . . . . 21 7.5.2. Abstract Network Element Property Map Example . . . . 23 8. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 23 8.1. Compatibility with Legacy ALTO Clients/Servers . . . . . 23 8.2. Compatibility with Multi-Cost Extensions . . . . . . . . 23 8.3. Compatibility with Incremental Update . . . . . . . . . . 24 9. Design Decisions and Discussions . . . . . . . . . . . . . . 24 9.1. Provide More General Calendar Extension . . . . . . . . . 24 10. Security Considerations . . . . . . . . . . . . . . . . . . . 24 10.1. Privacy Concerns . . . . . . . . . . . . . . . . . . . . 24 10.2. Resource Consumption on ALTO Servers . . . . . . . . . . 25 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 11.1. ALTO Cost Mode Registry . . . . . . . . . . . . . . . . 25 11.2. ALTO Cost Metric Registry . . . . . . . . . . . . . . . 25 11.3. ALTO Entity Domain Registry . . . . . . . . . . . . . . 26 11.4. ALTO Network Element Property Type Registry . . . . . . 26 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 13.1. Normative References . . . . . . . . . . . . . . . . . . 27 13.2. Informative References . . . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28 Bernstein, et al. Expires January 4, 2018 [Page 3] Internet-Draft ALTO Extension: Path Vector July 2017 1. Introduction The ALTO base protocol [RFC7285] is designed for exposing network information through services such as the Network Map service and the Cost Map service. These services use an extreme "single-node" abstraction, which represents the whole network with a single node and hosts with "endpoint groups" directly connected to the node. Although the "single-node" abstraction works well in many settings, it lacks the ability to support new emerging use cases, such as inter-datacenter flow scheduling and scientific high-performance computing data transfers. Specifically, the base ALTO protocol MUST provide the following two functionalities: o Providing information on shared bottlenecks: In the aforementioned use cases, the volume of a single flow can reach 10s - 100s Gbps, so that the network cannot treat the flows as independent like in the base ALTO protocol. In this case, ALTO servers MUST be able to provide information on shared bottlenecks to help applications avoid congestion. o Encapsulating multiple cost values in a single session: Some flow scheduling problems take multiple metrics into consideration. Making multiple queries introduces larger communication overhead, and more importantly, out-of-sync data for different cost types. Encapsulating multiple cost values in a single query and response session reduces communication overhead and simplifies the synchronization in use cases involving multiple cost types. This draft aims to extend the base ALTO protocol to support these new functionalities, with the path-vector extension. The path-vector extension specifies how to encode the shared bottlenecks in a network for a given set of flows with many design details driven by effectiveness, performance and backward compatibility considerations. The second functionality for simple cost types, such as those introduced in the base protocol, is already addressed in a recent extension, e.g. [I-D.ietf-alto-multi-cost]. However, the path- vector extension in this document has introduced a new cost type which complicates the situation. Thus, the multiple cost encapsulation must still be taken into consideration. The document is organized as follows. Section 3 gives an example of flow scheduling and illustrates the limitations of the base ALTO protocol in such a use case. Section 4 gives an overview of the path-vector extension, before specifying the details of the extension in Section 5 and Section 6. Section 7 presents several examples, and Section 9 explains some design decisions. Section 8 discusses Bernstein, et al. Expires January 4, 2018 [Page 4] Internet-Draft ALTO Extension: Path Vector July 2017 compatibility issues with some other ALTO extensions. Section 10 and Section 11 discusses about security and IANA considerations. 2. Terminology This document uses the same terms as defined in [RFC7285], [I-D.ietf-alto-multi-cost] and [I-D.roome-alto-unified-props] with the following additional terms: Abstract Network Element, Abstract Network Element Name, Abstract Network Element Property, Abstract Network Element Property Map and Path Vector. o Abstract Network Element (ANE): An abstract network element is an abstraction of network components, it can be an aggregation of links, middle boxes, Virtualized Network Function (VNF), or even a sub-network. An abstract network element has two attributes: abstract network element name and abstract network element property, which are defined below. o Abstract Network Element Name (ANEN): An abstract network element name is an identifier which uniquely identifies an abstract network element, as defined in Section 5.3. o Abstract Network Element Property (ANEP): An abstract network element property is a specific metric associated with a given abstract network element, as introduced in Section 4.3. An abstract network element CAN have several network element properties. o Abstract Network Element Property Map (ANEP Map): An abstract network element property map is a Filtered Property Map defined in [I-D.roome-alto-unified-props] which supports the "ane" domain in its "domain-types" capability. o Path Vector (PV): A path vector is an array of abstract network elements, representing an abstract path between entities (PIDs or endpoints). 3. Use Case: Capacity Region for Multi-Flow Scheduling Consider the case that routing is given. Then what application-layer traffic optimization will focus on is traffic scheduling among application-layer paths. Specifically, assume that an application has control over a set of flows F = {f_1, f_2, ..., f_|F|}. If routing is given, what the application can control is x_1, x_2, ..., x_|F|, where x_i is the amount of traffic for flow i. Let x = [x_1, ..., x_|F|] be the vector of the flow traffic amounts. Due to shared links, feasible values of x where link capacities are not exceeded can be a complex polytype. Bernstein, et al. Expires January 4, 2018 [Page 5] Internet-Draft ALTO Extension: Path Vector July 2017 Specifically, consider a network as shown in Figure 1. The network has 7 switches (sw1 to sw7) forming a dumb-bell topology. Switches sw1/sw3 provide access on one side, sw2/sw4 provide access on the other side, and sw5-sw7 form the backbone. End hosts eh1 to eh4 are connected to access switches sw1 to sw4 respectively. Assume that the bandwidth of link eh1 -> sw1 and link sw1 -> sw5 are 150 Mbps, and the bandwidth of the rest links are 100 Mbps. +------+ | | --+ sw6 +-- / | | \ PID1 +-----+ / +------+ \ +-----+ PID2 eh1__| |_ / \ ____| |__eh2 | sw1 | \ +--|---+ +---|--+ / | sw2 | +-----+ \ | | | |/ +-----+ \_| sw5 +---------+ sw7 | PID3 +-----+ / | | | |\ +-----+ PID4 eh3__| |__/ +------+ +------+ \____| |__eh4 | sw3 | | sw4 | +-----+ +-----+ Figure 1: Raw Network Topology. The single-node ALTO topology abstraction of the network is shown in Figure 2. +----------------------+ {eh1} | | {eh2} PID1 | | PID2 +------+ +------+ | | | | {eh3} | | {eh4} PID3 | | PID4 +------+ +------+ | | +----------------------+ Figure 2: Base Single-Node Topology Abstraction. Consider an application overlay (e.g., a large data analysis system) which needs to schedule the traffic among a set of end host source- destination pairs, say eh1 -> eh2 and eh1 -> eh4. The application can request a cost map providing end-to-end available bandwidth, using 'availbw' as cost-metric and 'numerical' as cost-mode. Bernstein, et al. Expires January 4, 2018 [Page 6] Internet-Draft ALTO Extension: Path Vector July 2017 The application will receive from ALTO server that the bandwidth of eh1 -> eh2 and eh1 -> eh4 are both 100 Mbps. But this information is not enough. Consider the following two cases: o Case 1: If eh1 -> eh2 uses the path eh1 -> sw1 -> sw5 -> sw6 -> sw7 -> sw2 -> eh2 and eh1 -> eh4 uses path eh1 -> sw1 -> sw5 -> sw7 -> sw4 -> eh4, then the application will obtain 150 Mbps. o Case 2: If eh1 -> eh2 uses the path eh1 -> sw1 -> sw5 -> sw7 -> sw2 -> eh2 and eh1 -> eh4 uses the path eh1 -> sw1 -> sw5 -> sw7 -> sw4 -> eh4, then the application will obtain only 100 Mbps. To allow applications to distinguish the two aforementioned cases, the network needs to provide more details. In particular, it needs to provide the following new capabilities: o The network needs to expose more detailed routing information to show the shared bottlenecks. o The network needs to provide the necessary abstraction to hide the real topology information as possible. The path-vector extension defined in this document will satisfy all the requirements. See [I-D.bernstein-alto-topo] for a survey of use-cases where extended network topology information is needed. 4. Overview This section presents a non-normative overview of the path-vector extension. It assumes the readers are familiar with (Filtered) Cost Map and Endpoint Cost Service defined in [RFC7285], their extensions defined in [I-D.ietf-alto-multi-cost] and Filtered Property Map defined in [I-D.roome-alto-unified-props]. 4.1. Path Vector A path vector is an array of abstract network elements, representing an abstract path between entities (PIDs or endpoints). Each abstract network element has two attributes: name and property. The abstract network element names are encoded in cost maps and the abstract network element properties are encoded in abstract network element property maps. Bernstein, et al. Expires January 4, 2018 [Page 7] Internet-Draft ALTO Extension: Path Vector July 2017 4.2. Cost Type Extension To provide abstract network element names of a path in cost maps, each cost value is a list of abstract network element names. However, as defined in Section 6.1.2 of [RFC7285], a cost mode is either "numerical" or "ordinal", none of which can be used to present a list. This document specifies a new cost mode "array" and a new cost metric "ane-path". The new cost mode "array" means each cost value in the cost maps is a list. The new cost metric "ane-path" means each cost value represents an abstract path consisting of abstract network element names between two entities (PIDs or endpoints). The new cost type follows the convention of the cost types in the base protocol. For example: +------------+--------------+---------------------------------------+ | cost mode | cost metric | meaning | +------------+--------------+---------------------------------------+ | numerical | routingcost | a number representing the routing | | | | cost | | ordinal | hopcount | a ranking representing the hop count | | array | ane-path | a list representing the ane path | +------------+--------------+---------------------------------------+ Table 1: Cost Types and Their Meanings 4.3. Abstract Network Element Property Map Given that Cost Map and Endpoint Cost service now provide the abstract network element names along a flow path, ALTO clients can learn that there exist bottlenecks between different flows. However, only providing the abstract network element names without abstract network element properties is not enough, because ALTO clients often require the information on specific metric values like the link capacity. This document adopts the property map defined in a recent draft [I-D.roome-alto-unified-props] to encode the properties of abstract network elements. A new domain "ane" is registered in the property map. Each entity in the "ane" domain is an abstract network element. The property map which supports "ane" domain is an Abstract Network Element Property Map. 4.4. New Media Type: multipart/related In the base ALTO protocol, ALTO servers use media types in the HTTP header to indicate the type of the response. Typically one response only contains a single media type, such as "application/alto- Bernstein, et al. Expires January 4, 2018 [Page 8] Internet-Draft ALTO Extension: Path Vector July 2017 costmap+json" or "application/alto-propmap+json". This has limited the capability of ALTO servers to return multiple services in a single response. Thus, an ALTO client MUST make multiple queries to get the information from services of different types. This has led to the data synchronization problem between dependent ALTO services because when making the second query, the result for the first query may have already changed. The very same problem can happen to Network Map and Cost Map resources. However, unlike Network Map and Cost Map which are considered more stable, path vectors and the dependent abstract network element property maps might change more frequently. Instead of introducing a new media type to encapsulate multiple types in a single response, this documents adopts the "multipart" media type defined in [RFC2387]. Thus, a response can contain both the path vector as a Cost Map (or Endpoint Cost Map) and the corresponding abstract network element property map as a Property Map. The media types of the path vector and the abstract network element property map can still be retrieved from the response, achieving consistency with the base ALTO protocol. For backward compatibility, this extension also allows ALTO clients to make multiple queries instead of encapsulating abstract network element property map along with the path vector. Thus, each Cost Map or Endpoint Cost Service with this extension MUST include a "prop- map" in their capabilities to indicate where to retrieve the network element properties. An additional field "query-id" MUST also be added to the "vtag" field to uniquely identify a path vector query session. 5. Path-Vector Extension: Basic Data Types This section formally specifies the path-vector extension of some basic data types. 5.1. Cost Type This document extends the cost types defined in Section 6.1 of [RFC7285] by introducing a new cost mode "array" and a new cost metric "ane-path". 5.1.1. Cost Metric This document specifies a new cost metric: "ane-path". It is of type CostMetric as defined in Section 10.6 of [RFC7285]. The cost metric "ane-path" MUST NOT be used when the cost mode is not "array" unless it is explicitly specified by a future extension. Meanwhile, an ALTO Bernstein, et al. Expires January 4, 2018 [Page 9] Internet-Draft ALTO Extension: Path Vector July 2017 server with path-vector extension MUST support the cost metric "ane- path". Cost metric "ane-path": This cost metric MUST be encoded as the JSONString "ane-path". 5.1.2. Cost Mode This document extends the CostMode defined in Section 10.5 of [RFC7285] with a new cost mode: "array". The extended CostMode is encoded as a string and MUST have a value of either "numerical", "ordinal" or "array" unless it is explicitly specified by a future extension. In particular, this extension has specified that when the cost metric is "ane-path", the cost value MUST be interpreted as a JSONArray of Abstract Network Element Names (defined in Section 5.3). An ALTO cost service MUST return a JSONArray of JSONValue when the cost mode is "array" unless the interpretation is explicitly specified by an ALTO extension. Cost mode "array": This cost mode MUST be encoded as the JSONString "array". 5.2. ANE Domain This document specifies a new domain in addition to the ones in [I- D.roome-alto-unified-props]. 5.2.1. Domain Name ane 5.2.2. Domain-Specific Entity Addresses The entity address of ane domain is encoded as a JSON string. The string MUST be no more than 64 characters, and it MUST NOT contain characters other than US-ASCII alphanumeric characters (U+0030-U+0039, U+0041-U+005A, and U+0061-U+007A), the hyphen ('-', U+002D), the colon (':', U+003A), the at sign ('@', code point U+0040), the low line ('_', U+005F), or the '.' separator (U+002E). The '.' separator is reserved for future use and MUST NOT be used unless specifically indicated in this document, or an extension document. Bernstein, et al. Expires January 4, 2018 [Page 10] Internet-Draft ALTO Extension: Path Vector July 2017 5.3. Abstract Network Element Name An Abstract Network Element Name MUST be encoded as an EntityAddr as defined in Section 5.2.2. It MUST belong to the "ane" domain. 5.4. Version Tag This document extends the VersionTag, previously defined in Section 10.3 of [RFC7285] with an optional field "query-id". If an ALTO cost service supports the path-vector extension, this field MUST be included in the "vtag" field, and the "vtag" field MUST be included in the "meta" field in the response in order to provide the "query-id" information. object { ResourceID resource-id; JSONString tag; [JSONString query-id;] } VersionTag; resource-id, tag: As defined in Section 10.3 of [RFC7285]. query-id: A string used to uniquely identify the abstract network element names in the response and correlate abstract network element names with abstract network element properties. A "query- id" MUST be encoded in the same format as defined in Section 10.1 of [RFC7285]. 6. Path-Vector Extension: Services This section extends IRDResourceEntry, Cost Map Service and Endpoint Cost Service. 6.1. IRD Extensions This document extends IRDResourceEntry defined in Section 9.2.2 of [RFC7285] by introducing a new entry named "property-map", which indicates where the specific properties of the abstract network elements can be retrieved. The IRDResourceEntry object is extended as follows: Bernstein, et al. Expires January 4, 2018 [Page 11] Internet-Draft ALTO Extension: Path Vector July 2017 object { JSONString uri; JSONString media-type; [JSONString accepts;] [Capabilities capabilities;] [ResourceID uses<0..*>;] [ResourceID property-map;] } IRDResourceEntry; uri, media-type, accepts, capabilities, uses: The same as defined in Section 9.2.2 of [RFC7285]. property-map: A resource ID defined in the same IRD pointing to an abstract network element property map as defined in Section 2. 6.2. Cost Map Extensions This document extends the Cost Map defined in Section 11.2.3 of [RFC7285]. The specifications for "HTTP method", "accept input parameters" and "uses" are the same as defined in Section 11.2.3 of [RFC7285]. 6.2.1. Media Type The path vector extension now enables ALTO clients to receive multiple services in a cost map response. Specifically, if an ALTO client accepts "multipart/related", "application/alto-costmap+json" and "application/alto-propmap+json" at the same time, the ALTO server MUST use "multipart/related" as the media type in the HTTP header. 6.2.2. Capabilities If a service supports the path-vector extension, the "cost-type- names" field MUST include a single cost type with "ane-path" as cost metric and "array" as cost mode. 6.2.3. Property-map If a service supports the path-vector extension, the "property-map" field MUST be specified. This field is a resource ID of an abstract network element property map where the abstract network element properties are provided. Bernstein, et al. Expires January 4, 2018 [Page 12] Internet-Draft ALTO Extension: Path Vector July 2017 6.2.4. Response If an ALTO client accepts "multipart/related" as defined in Section 6.3.1, HTTP body of the response MUST consists of two parts with the media types "application/alto-costmap+json" and "application/alto-propmap+json" accordingly. Specifically, the part with media type "application/alto-costmap+json" MUST be the first part. The content of the "application/alto-costmap+json" part uses the format in Section 11.2.3.6 of [RFC7285] with the following constraints: o The cost value for a path vector query, e.g. the cost mode is "array" and the cost metric is "ane-path", MUST be encoded as a JSONArray of AbstractNetworkElementName. o If the query sent by the client includes cost type path vector, the "vtag" field defined in Section 5.4 has to be included in the response. And the "query-id" information in "vtag" MUST be provided to ALTO clients. 6.3. Filtered Cost Map Extensions This document extends the Filtered Cost Map defined in Section 4.1 of [I-D.ietf-alto-multi-cost]. The specifications for "HTTP method" and "uses" are the same as defined in Section 4.1 of [I-D.ietf-alto-multi-cost]. 6.3.1. Media Type The same as Section 6.2.1. 6.3.2. Capabilities The FilteredCostMapCapabilities object has the same format as defined in Section 4.1.1 of [I-D.ietf-alto-multi-cost] with the following constraint: testable-cost-type-names: The path vector cost type with "ane-path" as the cost metric and "array" as the cost mode MUST NOT be included in "testable-cost-type-names". Bernstein, et al. Expires January 4, 2018 [Page 13] Internet-Draft ALTO Extension: Path Vector July 2017 6.3.3. Property-map The same as Section 6.2.3. 6.3.4. Accept Input Parameters The ReqFilteredCostMap uses the same format as defined in Section 4.1.2 of [I-D.ietf-alto-multi-cost], with the following constraints: constraints, or-constraints: If the path vector cost type is included in either "cost-type" or "multi-cost-types", ALTO clients MUST NOT use it in "constraints" or "or-constraints". Otherwise, the ALTO server MUST return an error with error code "E_INVALID_FIELD_VALUE". testable-cost-types: The path vector cost type MUST NOT be included in the "testable-cost-types" field. Otherwise, the ALTO server MUST return an error with error code "E_INVALID_FIELD_VALUE". 6.3.5. Response If an ALTO client accepts "multipart/related" as defined in Section 6.3.1, HTTP body of the response MUST consist of two parts with the media types "application/alto-costmap+json" and "application/alto-propmap+json" accordingly. Specifically, the part with media type "application/alto-costmap+json" MUST be the first part. The content of the "application/alto-costmap+json" part has the same format as defined in Section 4.1.3 of [I-D.ietf-alto-multi-cost] with the following constraints: o When the path vector cost type is included in "cost type" or "multi-cost-type", the corresponding cost value MUST be encoded as a JSONArray of AbstractNetworkElementName. o If the query sent by the client includes cost type path vector, the "vtag" field defined in Section 5.4 has to be included in the response. And the "query-id" information in "vtag" MUST be provided to ALTO clients. 6.4. Endpoint Cost Service Extensions This document extends the Endpoint Cost Service defined in Section 4.2 in [I-D.ietf-alto-multi-cost]. Bernstein, et al. Expires January 4, 2018 [Page 14] Internet-Draft ALTO Extension: Path Vector July 2017 The specifications for "HTTP method" and "uses" are the same as defined in Section 4.2 in [I-D.ietf-alto-multi-cost]. 6.4.1. Media Type The path vector extension now enables ALTO clients to receive multiple objects from the endpoint cost service response. Specifically, if an ALTO client accepts "multipart/related", "application/alto-endpointcost+json" and "application/alto- propmap+json" at the same time, the ALTO server MUST use "multipart/ related" as the media type in the HTTP header. 6.4.2. Capabilities The same as defined in Section 6.3.2. 6.4.3. Property-map The same as Section 6.2.3. 6.4.4. Accept Input Parameters The ReqEndpointCostMap uses the same format as defined in Section 4.2.2 of [I-D.ietf-alto-multi-cost], with the following constraints: cost-type, multi-cost-types: ALTO clients MUST include the path vector cost type, e.g. the one with "ane-path" as cost metric and "array" as cost mode, in either "cost-type" or "multi-cost-types" to activate the path vector extension. constraints, or-constraints: If the path vector cost type is included in either "cost-type" or "multi-cost-types", ALTO clients MUST NOT use it in "constraints" or "or-constraints". Otherwise, the ALTO server MUST return an error with error code "E_INVALID_FIELD_VALUE". testable-cost-types: The path vector cost type MUST NOT be included in the "testable-cost-types" field. Otherwise, the ALTO server MUST return an error with error code "E_INVALID_FIELD_VALUE". 6.4.5. Response If an ALTO client accepts "multipart/related" as defined in Section 6.4.1, HTTP body of the response MUST consist of two parts with the media types "application/alto-endpointcost+json" and "application/alto-propmap+json" accordingly. Specifically, the part Bernstein, et al. Expires January 4, 2018 [Page 15] Internet-Draft ALTO Extension: Path Vector July 2017 with media type "application/alto-endpointcost+json" MUST be the first part. The content of the "application/alto-endpointcost+json" part has the same format as defined in Section 4.2.3 of [I-D.ietf-alto-multi-cost] with the following constraints: o When the path vector cost type is included in "cost type" or "multi-cost-type", the corresponding cost value MUST be encoded as a JSONArray of AbstractNetworkElementName. o If the query sent by the client includes cost type path vector, the "vtag" field defined in Section 5.4 has to be included in the response. And the "query-id" information in "vtag" MUST be provided to ALTO clients. 7. Examples This section lists a series of examples to proceed the flow scheduling use case in Section 3. 7.1. Workflow This section gives a typical workflow of an ALTO client using the path-vector extension. 1. Send a GET request for the whole Information Resource Directory. 2. Look for the resource of the (Filtered) Cost Map/Endpoint Cost Service which contains the path vector cost type and get the resource ID of the dependent abstract network element property map. 3. Check whether the capabilities of the property map includes the desired "prop-types". 4. Send a path-vector request which accepts "multipart/related" media type following Section 6.2.1, Section 6.3.1 or Section 6.4.1. Alternatively, one can replace step 4 with the following: 1. Send a path-vector request which accepts "application/alto- costmap+json" or "application/alto-endpointcost+json". 2. Find the "query-id" in "vtag" in the response. Bernstein, et al. Expires January 4, 2018 [Page 16] Internet-Draft ALTO Extension: Path Vector July 2017 3. Query the dependent abstract network element property map with the query ID and abstract network element names to retrieve the associated properties. 7.2. Information Resource Directory Example Here is an example of an Information Resource Directory. In this example, filtered cost map "cost-map-pv" doesn't support the multi- cost extension but support the path-vector extension, "endpoint- multicost-map" supports both multi-cost extension and path-vector extension. Filtered Property Map "propmap-delay-availbw" supports properties "availbw" and "delay", and "propmap-location" supports property "location". { "meta": { "cost-types": { "pv": { "cost-mode": "array", "cost-metric": "ane-path" }, "num-routingcost": { "cost-mode": "numerical", "cost-metric": "routingcost" }, "num-hopcount": { "cost-mode": "numerical", "cost-metric": "hopcount" } } }, "resources": { "my-default-networkmap": { "uri" : "http://alto.example.com/networkmap", "media-type" : "application/alto-networkmap+json" } "cost-map-pv" : { "uri": "http://alto.example.com/costmap/pv", "media-type": "application/alto-costmap+json", "accepts": "application/alto-costmapfilter+json", "capabilities": { "cost-type-names": [ "pv", "num-hopcount" ] }, "property-map": "propmap-delay", "uses": [ "my-default-networkmap" ] }, "endpoint-multicost-map" : { "uri": "http://alto.exmaple.com/endpointcostmap/multicost", Bernstein, et al. Expires January 4, 2018 [Page 17] Internet-Draft ALTO Extension: Path Vector July 2017 "media-type": "application/alto-endpointcost+json", "accepts": "application/alto-endpointcostparams+json", "capabilities": { "cost-constraints": true, "cost-type-names": [ "pv", "num-routingcost" ], "max-cost-types": 2 }, "property-map": "propmap-availbw" }, "propmap-availbw" : { "uri": "http://alto.exmaple.com/propmap/availbw", "media-type": "application/alto-propmap+json", "accepts": "application/alto-propmapparams+json", "capabilities": { "domain-types": [ "ane" ], "prop-types": [ "delay", "availbw" ] } }, "propmap-delay" : { "uri": "http://alto.exmaple.com/propmap/delay", "media-type": "application/alto-propmap+json", "accepts": "application/alto-propmapparams+json", "capabilities": { "domain-types": [ "ane" ], "prop-types": [ "delay" ] } } } } 7.3. Single Query Example # 1 POST /costmap/pv HTTP/1.1 Host: alto.example.com Accept: multipart/related, application/alto-costmap+json, application/alto-propmap+json, application/alto-error+json Content-Length: [TBD] Content-Type: application/alto-costmapfilter+json { "cost-type": { "cost-mode": "array", "cost-metric": "ane-path" }, "pids": { "srcs": [ "PID1" ], "dsts": [ "PID2", "PID3" ] } Bernstein, et al. Expires January 4, 2018 [Page 18] Internet-Draft ALTO Extension: Path Vector July 2017 } HTTP/1.1 200 OK Content-Length: [TBD] Content-Type: multipart/related; boundary=42 --42 Content-Type: application/alto-costmap+json { "meta": { "dependent-vtags": [ { "resource-id": "default-network-map", "tag": "75ed013b3cb58f896e839582504f622838ce670f" } ], "cost-type": { "cost-mode": "array", "cost-metric": "ane-path" }, "vtag": { "resource-id": "cost-map-pv", "tag": "27612897acf278ffu3287c284dd28841da78213", "query-id": "query1" } }, "cost-map": { "PID1": { "PID2": [ "ane:L001", "ane:L003" ], "PID3": [ "ane:L001", "ane:L004" ] } } } --42 Content-Type: application/alto-propmap+json { "property-map": { "ane:L001": { "delay": 46}, "ane:L003": { "delay": 50}, "ane:L004": { "delay": 70} } } --42-- Bernstein, et al. Expires January 4, 2018 [Page 19] Internet-Draft ALTO Extension: Path Vector July 2017 7.4. Single Query Example # 2 POST /endpointcostmap/multicost HTTP/1.1 Host: alto.example.com Accept: multipart/related, application/alto-costmap+json, application/alto-propmap+json, application/alto-error+json Content-Length: [TBD] Content-Type: application/alto-costmapfilter+json { "multi-cost-types": [ { "cost-mode": "array", "cost-metric": "ane-path" }, { "cost-mode": "numerical", "cost-metric": "routingcost" } ], "endpoints": { "srcs": [ "ipv4:192.0.2.2" ], "dsts": [ "ipv4:192.0.2.89", "ipv4:203.0.113.45", "ipv6:2001:db8::10" ] } } HTTP/1.1 200 OK Content-Length: [TBD] Content-Type: multipart/related; boundary=example-2 --example-2 Content-Type: application/alto-endpointcost+json { "meta": { "multi-cost-types": [ {"cost-mode": "array", "cost-metric": "ane-path"}, {"cost-mode": "numerical", "cost-metric": "routingcost"} ] "vtag": { "resource-id": "endpoint-multicost-map", "tag": "47612897acf278ffa3287cb84dd28841da78213", "query-id": "query2" } }, Bernstein, et al. Expires January 4, 2018 [Page 20] Internet-Draft ALTO Extension: Path Vector July 2017 "endpoint-cost-map": { "ipv4:192.0.2.2": { "ipv4:192.0.2.89": [[ "ane:L001", "ane:L003", "ane:L004" ], 77], "ipv4:203.0.113.45": [[ "ane:L001", "ane:L004", "ane:L005" ], 68], "ipv6:2001:db8::10": [[ "ane:L001", "ane:L005", "ane:L007" ], 98] } } } --example-2 Content-Type: application/alto-propmap+json { "property-map": { "ane:L001": { "availbw": 50 }, "ane:L003": { "availbw": 48 }, "ane:L004": { "availbw": 55 }, "ane:L005": { "availbw": 60 }, "ane:L007": { "availbw": 35 } } } --example-2-- 7.5. Multiple Queries Example 7.5.1. Endpoint Cost Service Example Bernstein, et al. Expires January 4, 2018 [Page 21] Internet-Draft ALTO Extension: Path Vector July 2017 POST /endpointcostmap/multicost 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 { "multi-cost-types": [ { "cost-mode": "array", "cost-metric": "ane-path" }, { "cost-mode": "numerical", "cost-metric": "routingcost" } ], "endpoints": { "srcs": [ "ipv6:2001:db8::10" ], "dsts": [ "ipv4:192.0.2.3", "ipv4:203.0.113.56" ] } } HTTP/1.1 200 OK Content-Length: [TBD] Content-Type: application/alto-endpointcost+json { "meta": { "vtag": { "resource-id": "endpoint-multicost-map", "tag": "f7622897bcf278ffu3287c284dd23841da78213", "query-id": "query3" }, "multi-cost-types": [ { "cost-mode": "array", "cost-metric": "ane-path" }, { "cost-mode": "numerical", "cost-metric": "routingcost"} ] }, "endpoint-cost-map": { "ipv6:2001:db8::10": { "ipv4:192.0.2.3": [ "ane:L001", "ane:L006" ], "ipv4:203.0.113.56": [ "ane:L001", "ane:L007" ] } } } Bernstein, et al. Expires January 4, 2018 [Page 22] Internet-Draft ALTO Extension: Path Vector July 2017 7.5.2. Abstract Network Element Property Map Example POST /propmap/availbw HTTP/1.1 Host: alto.example.com Accept: application/alto-propmap+json,application/alto-error+json Content-Length: [TBD] Content-Type: application/alto-propmapparams+json { "query-id": "query3", "entities" : [ "ane:L001", "ane:L006" ], "properties" : [ "availbw" ] } HTTP/1.1 200 OK Content-Length: [TBD] Content-Type: application/alto-propmap+json { "property-map": { "ane:L001": { "availbw": 25 }, "ane:L006": { "availbw": 40 } } } 8. Compatibility 8.1. Compatibility with Legacy ALTO Clients/Servers Legacy ALTO clients SHOULD NOT send queries with the path-vector extension and ALTO servers with this extension SHOULD NOT have any compatibility issue. Legacy ALTO servers do not support cost types with cost mode being "array" and cost metric being "ane-path", so they MUST NOT announce the extended cost types in IRD. Thus, ALTO clients MUST NOT send queries specified in this extension to legacy ALTO servers according to Section 11.3.2.3 [RFC7285]. 8.2. Compatibility with Multi-Cost Extensions Path Vector is not a testable cost type. Any format of constraints SHOULD NOT be applied to cost type path-vector in order for multi- cost to support the path-vector extension. Specifically, o Cost type path-vector MUST NOT be included in "testable-cost- types-names" or "testable-cost-types". Bernstein, et al. Expires January 4, 2018 [Page 23] Internet-Draft ALTO Extension: Path Vector July 2017 o When "testable-cost-types-names" is omitted in the "capabilities" and "testable-cost-types" is omitted in the input parameters, "constraints" or "or-constraints" SHOULD NOT add any format of constraints on cost type path-vector. 8.3. Compatibility with Incremental Update Without considering the incremental update of multipart/related information, there is no compatibility issue with incremental update extension. Compatibility issue with the incremental update of multipart/related information will be discussed and addressed in the next version. 9. Design Decisions and Discussions 9.1. Provide More General Calendar Extension Cost Calendar is proposed as a useful ALTO extension to provide the historical cost values for Filtered Cost Map Service and Endpoint Cost Service. Since path vector is an extension to these services, it SHOULD be compatible with Cost Calendar extension. However, the calendar of a path-vector (Endpoint) Cost Map is insufficient for the application which requires the historical data of routing state information. The (Endpoint) Cost Map can only provide the changes of the paths. But more useful information is the history of network element properties which are recorded in the dependent Network Element Property Map. Before the Unified Property Map is introduced as an ALTO extension, Filtered Cost Map Service and Endpoint Cost Service are the only resources which require the calendar supported. Because other resources don't have to be updated frequently. But Network Element Property Map as a use case of Unified Property Map will collect the real-time information of the network. It SHOULD be updated as soon as possible once the metrics of network elements change. So the requirement is to provide a general calendar extension which not only meets the Filtered Cost Map and Endpoint Cost Service but also applies to the Property Map Service. 10. Security Considerations 10.1. Privacy Concerns We can identify multiple potential security issues. A main security issue is network privacy, as the path-vector information may reveal more network internal structures than the more abstract single-node Bernstein, et al. Expires January 4, 2018 [Page 24] Internet-Draft ALTO Extension: Path Vector July 2017 abstraction. The network should consider protection mechanisms to reduce information exposure, in particular, in settings where the network and the application do not belong to the same trust domain. On the other hand, in a setting of the same trust domain, a key benefit of the path-vector abstraction is reduced information transfer from the network to the application. The path-vector query may also reveal more information about the application. In particular, the application may reveal all potential transfers sites (e.g., where the data source is replicated, and where the potential replication sites are). The application should evaluate the potential privacy concerns. Beyond the privacy issues, the computation of the path-vector is unlikely to be cachable, in that the results will depend on the particular requests (e.g., where the flows are distributed). Hence, this service may become an entry point for denial of service attacks on the availability of an ALTO server. Hence, authenticity and authorization of this ALTO service may need to be better protected. 10.2. Resource Consumption on ALTO Servers The Abstract Network Element Property Map is dynamically enriched when the (Filtered) Cost Map/Endpoint Cost Service is queried of the path-vector information. The properties of the abstract network elements can consume a large amount of resources when cached. So, a time-to-live is needed to remove outdated entries in the Network Element Property Map. 11. IANA Considerations 11.1. ALTO Cost Mode Registry This document specifies a new cost mode "array". However, the base ALTO protocol does not have a Cost Mode Registry where new cost mode can be registered. This new cost mode will be registered once the registry is defined either in a revised version of [RFC7285] or in another future extension. 11.2. ALTO Cost Metric Registry A new cost metric needs to be registered in the "ALTO Cost Metric Registry", listed in Table 2. Bernstein, et al. Expires January 4, 2018 [Page 25] Internet-Draft ALTO Extension: Path Vector July 2017 +-------------+---------------------+ | Identifier | Intended Semantics | +-------------+---------------------+ | ane-path | See Section 5.1.1 | +-------------+---------------------+ Table 2: ALTO Cost Metrics 11.3. ALTO Entity Domain Registry As proposed in Section 9.2 of [I-D.roome-alto-unified-props], "ALTO Entity Domain Registry" is requested. Besides, a new domain is to be registered, listed in Table 3. +-------------+--------------------------+--------------------------+ | Identifier | Entity Address Encoding | Hierarchy & Inheritance | +-------------+--------------------------+--------------------------+ | ane | See Section 5.2.2 | None | +-------------+--------------------------+--------------------------+ Table 3: ALTO Entity Domain 11.4. ALTO Network Element Property Type Registry The "ALTO Abstract Network Element Property Type Registry" is required by the ALTO Entity Domain "ane", listed in Table 4. +-------------+--------------------------+ | Identifier | Intended Semantics | +-------------+--------------------------+ | availbw | The available bandwidth | | delay | The transmission delay | +-------------+--------------------------+ Table 4: ALTO Abstract Network Element Property Types 12. Acknowledgments The authors would like to thank discussions with Andreas Voellmy, Erran Li, Haibin Son, Haizhou Du, Jiayuan Hu, Qiao Xiang, Tianyuan Liu, Xiao Shi, Xin Wang, and Yan Luo. 13. References Bernstein, et al. Expires January 4, 2018 [Page 26] Internet-Draft ALTO Extension: Path Vector July 2017 13.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . 13.2. Informative References [I-D.amante-i2rs-topology-use-cases] Medved, J., Previdi, S., Lopez, V., and S. Amante, "Topology API Use Cases", draft-amante-i2rs-topology-use- cases-01 (work in progress), October 2013. [I-D.bernstein-alto-topo] Bernstein, G., Yang, Y., and Y. Lee, "ALTO Topology Service: Uses Cases, Requirements, and Framework", draft- bernstein-alto-topo-00 (work in progress), October 2013. [I-D.clemm-i2rs-yang-network-topo] Clemm, A., Medved, J., Tkacik, T., Varga, R., Bahadur, N., and H. Ananthakrishnan, "A YANG Data Model for Network Topologies", draft-clemm-i2rs-yang-network-topo-01 (work in progress), October 2014. [I-D.gao-alto-fcs] Gao, K., Zhang, J., Wang, J., Xiang, Q., and Y. Yang, "ALTO Extension: Flow-based Cost Query", draft-gao-alto- fcs-01 (work in progress), March 2017. [I-D.ietf-alto-cost-calendar] Randriamasy, S., Yang, Y., Wu, Q., Lingli, D., and N. Schwan, "ALTO Cost Calendar", draft-ietf-alto-cost- calendar-01 (work in progress), February 2017. [I-D.ietf-alto-incr-update-sse] Roome, W. and Y. Yang, "ALTO Incremental Updates Using Server-Sent Events (SSE)", draft-ietf-alto-incr-update- sse-03 (work in progress), September 2016. [I-D.ietf-alto-multi-cost] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost ALTO", draft-ietf-alto-multi-cost-07 (work in progress), March 2017. Bernstein, et al. Expires January 4, 2018 [Page 27] Internet-Draft ALTO Extension: Path Vector July 2017 [I-D.lee-alto-app-net-info-exchange] Lee, Y., Bernstein, G., Choi, T., and D. Dhody, "ALTO Extensions to Support Application and Network Resource Information Exchange for High Bandwidth Applications", draft-lee-alto-app-net-info-exchange-02 (work in progress), July 2013. [I-D.roome-alto-unified-props] Roome, W., "Extensible Property Maps for the ALTO Protocol", draft-roome-alto-unified-props-01 (work in progress), July 2016. [RFC2387] Levinson, E., "The MIME Multipart/Related Content-type", RFC 2387, DOI 10.17487/RFC2387, August 1998, . [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, . Authors' Addresses Greg Bernstein Grotto Networking Fremont, CA USA Email: gregb@grotto-networking.com Shiwei Dawn Chen Tongji University 4800 Caoan Road Shanghai 201804 China Email: dawn_chen_f@hotmail.com Kai Gao Tsinghua University Beijing Beijing China Email: gaok12@mails.tsinghua.edu.cn Bernstein, et al. Expires January 4, 2018 [Page 28] Internet-Draft ALTO Extension: Path Vector July 2017 Young Lee Huawei TX USA Email: leeyoung@huawei.com Wendy Roome Nokia/Bell Labs 600 Mountain Ave, Rm 3B-324 Murray Hill, NJ 07974 USA Phone: +1-908-582-7974 Email: wendy.roome@nokia.com Michael Scharf Nokia Germany Email: michael.scharf@nokia.com Y. Richard Yang Yale University 51 Prospect St New Haven CT USA Email: yry@cs.yale.edu Jingxuan Jensen Zhang Tongji University 4800 Caoan Road Shanghai 201804 China Email: jingxuan.n.zhang@gmail.com Bernstein, et al. Expires January 4, 2018 [Page 29]