ALTO WG K. Gao Internet-Draft Sichuan University Intended status: Standards Track Y. Lee Expires: January 9, 2020 Huawei S. Randriamasy Nokia Bell Labs Y. Yang Yale University J. Zhang Tongji University July 8, 2019 ALTO Extension: Path Vector Cost Type draft-ietf-alto-path-vector-07 Abstract The Application-Layer Traffic Optimization (ALTO) protocol [RFC7285] has defined cost maps and endpoint cost maps to provide basic network information. However, they provide only scalar (numerical or ordinal) cost mode values, 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 the capacity region for a given set of flows (called co-flows). A non-normative example called co-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. 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 https://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 Gao, et al. Expires January 9, 2020 [Page 1] Internet-Draft ALTO Extension: Path Vector July 2019 time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on January 9, 2020. Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Use Case . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Capacity Region for Co-Flow Scheduling . . . . . . . . . 5 3.2. In-Network Caching . . . . . . . . . . . . . . . . . . . 7 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.1. New Cost Mode to Encode Path Vectors . . . . . . . . . . 8 4.2. New ALTO Entity Domain for ANE Properties . . . . . . . . 8 4.3. Multipart/Related Resource for Consistency . . . . . . . 9 5. Basic Data Types . . . . . . . . . . . . . . . . . . . . . . 10 5.1. ANE Identifier . . . . . . . . . . . . . . . . . . . . . 10 5.2. Path Vector Cost Type . . . . . . . . . . . . . . . . . . 10 5.2.1. Cost Metric: ane-path . . . . . . . . . . . . . . . . 11 5.2.2. Cost Mode: array . . . . . . . . . . . . . . . . . . 11 5.3. ANE Domain . . . . . . . . . . . . . . . . . . . . . . . 11 5.3.1. Domain Name . . . . . . . . . . . . . . . . . . . . . 11 5.3.2. Domain-Specific Entity Identifier . . . . . . . . . . 11 5.3.3. Hierarchy and Inheritance . . . . . . . . . . . . . . 11 5.4. ANE Properties . . . . . . . . . . . . . . . . . . . . . 11 5.4.1. ANE Property: Maximum Reservable Bandwidth . . . . . 11 5.4.2. ANE Property: Persistent Entity . . . . . . . . . . . 12 6. Service Extensions . . . . . . . . . . . . . . . . . . . . . 12 6.1. Multipart Filtered Cost Map for Path Vector . . . . . . . 12 6.1.1. Media Type . . . . . . . . . . . . . . . . . . . . . 12 6.1.2. HTTP Method . . . . . . . . . . . . . . . . . . . . . 12 6.1.3. Accept Input Parameters . . . . . . . . . . . . . . . 12 Gao, et al. Expires January 9, 2020 [Page 2] Internet-Draft ALTO Extension: Path Vector July 2019 6.1.4. Capabilities . . . . . . . . . . . . . . . . . . . . 13 6.1.5. Uses . . . . . . . . . . . . . . . . . . . . . . . . 13 6.1.6. Response . . . . . . . . . . . . . . . . . . . . . . 13 6.2. Multipart Endpoint Cost Service for Path Vector . . . . . 15 6.2.1. Media Type . . . . . . . . . . . . . . . . . . . . . 15 6.2.2. HTTP Method . . . . . . . . . . . . . . . . . . . . . 15 6.2.3. Accept Input Parameters . . . . . . . . . . . . . . . 15 6.2.4. Capabilities . . . . . . . . . . . . . . . . . . . . 15 6.2.5. Uses . . . . . . . . . . . . . . . . . . . . . . . . 15 6.2.6. Response . . . . . . . . . . . . . . . . . . . . . . 16 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 17 7.1. Information Resource Directory Example . . . . . . . . . 17 7.2. Example: Multipart Filtered Cost Map . . . . . . . . . . 19 7.3. Example: Multipart Endpoint Cost Service . . . . . . . . 20 7.4. Example: Incremental Updates . . . . . . . . . . . . . . 22 8. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 24 8.1. Compatibility with Base ALTO Clients/Servers . . . . . . 24 8.2. Compatibility with Multi-Cost Extension . . . . . . . . . 24 8.3. Compatibility with Incremental Update . . . . . . . . . . 24 9. General Discussions . . . . . . . . . . . . . . . . . . . . . 25 9.1. Provide Calendar for Property Map . . . . . . . . . . . . 25 9.2. Constraint Tests for General Cost Types . . . . . . . . . 25 9.3. General Multipart Resources Query . . . . . . . . . . . . 25 10. Security Considerations . . . . . . . . . . . . . . . . . . . 26 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 11.1. ALTO Cost Mode Registry . . . . . . . . . . . . . . . . 27 11.2. ALTO Entity Domain Registry . . . . . . . . . . . . . . 27 11.3. ALTO Property Type Registry . . . . . . . . . . . . . . 27 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 13.1. Normative References . . . . . . . . . . . . . . . . . . 28 13.2. Informative References . . . . . . . . . . . . . . . . . 28 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 1. Introduction The base ALTO protocol [RFC7285] is designed to expose network information through services such as cost maps and endpoint cost service. These services use an extreme "single-node" network abstraction, which represents a whole network as a single node, and hosts as "endpoint groups" directly connected to the node. Although the "single-node" abstraction works well in many settings, it lacks the ability to support emerging use cases, such as co-flow scheduling for large-scale data analytics. For such a use case, applications require a more powerful network view abstraction beyond the "single-node" abstraction. Gao, et al. Expires January 9, 2020 [Page 3] Internet-Draft ALTO Extension: Path Vector July 2019 To support capabilities like co-flow scheduling, this document uses a "path vector" abstraction to represent more detailed network graph information like capacity regions. A path vector is a sequence of abstract network elements (ANEs), and each ANE represents a network device that end-to-end traffic goes through, such as links, switches, middleboxes, and their aggregations. An ANE can have properties such as "bandwidth", and "delay". Providing such information can help both applications to achieve better application performance and networks to avoid network congestion. Providing path vector abstraction using ALTO introduces the following additional requirements (ARs): AR-1: The path vector abstraction requires the encoding of array- like cost values rather than scalar cost values in cost maps or endpoint cost maps. Specifically, the path vector abstraction requires the specification of the sequence of ANEs between sources and destinations. Such a sequence, however, cannot be encoded by the scalar types (numerical or ordinal) which the base ALTO protocol supports. AR-2: The path vector abstraction requires the encoding of the properties of aforementioned ANEs. Specifically, only the sequences of ANEs are not enough for existing use cases. Properties of ANEs such as "bandwidth" and "delay" are needed by applications to properly construct network constraints or states. AR-3: The path vector abstraction requires consistent encoding of path vectors (AR-1) and the properties of the ANEs in a path vector (AR-2). Specifically, path vectors and the properties of ANEs in the vectors are dependent. A mechanism to query both of them consistently is necessary. This document proposes the path vector extension to the ALTO protocol to satisfy these additional requirements . Specifically, the extension encodes the array (AR-1) of ANEs over an end-to-end path using a new cost type, and conveys the properties of ANEs (AR-2) using unified property map [I-D.ietf-alto-unified-props-new]. The path vector and ANE properties are conveyed in a single message encoded as a multipart/ related message to satisfy AR-3. Gao, et al. Expires January 9, 2020 [Page 4] Internet-Draft ALTO Extension: Path Vector July 2019 The rest of this document is organized as follows. Section 3.1 gives an example of co-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. Section 5.2 introduces a new cost type. Section 5.3 registers a new domain in Domain Registry. Section 6.1 and Section 6.2 define new ALTO resources to support Path Vector query by using the request format of Filtered Cost Map and Endpoint Cost Service. Section 7 presents several examples. Section 8 and Section 9 discusses compatibility issues with other existing ALTO extensions and design decisions. Section 10 and Section 11 review the security and IANA considerations. 2. Terminology Besides the terms defined in [RFC7285] and [I-D.ietf-alto-unified-props-new], this document also uses the following additional terms: Abstract Network Element 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, middleboxes, virtualized network function (VNF), etc. An abstract network element has two types of attributes: a name and a set of properties. o Path Vector: A path vector is an array of ANEs. It presents an abstract network path between source/destination points such as PIDs or endpoints. 3. Use Case 3.1. Capacity Region for Co-Flow Scheduling Assume that an application has control over a set of flows, which may go through shared links or switches and share a bottleneck. The application hopes to schedule the traffic among multiple flows to get better performance. The capacity region information for those flows will benefit the scheduling. However, existing cost maps cannot reveal such information. 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. Endhosts eh1 to eh4 are connected to access switches sw1 to sw4 respectively. Assume that the bandwidth all links are 100 Mbps. Gao, et al. Expires January 9, 2020 [Page 5] Internet-Draft ALTO Extension: Path Vector July 2019 +------+ | | --+ 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 wants to schedule the traffic among a set of end host source- destination pairs, say eh1 -> eh2 and eh3 -> eh4. The application can request a cost map providing end-to-end available bandwidth, using 'availbw' as cost-metric and 'numerical' as cost-mode. The application will receive from ALTO server that the bandwidth of eh1 -> eh2 and eh3 -> 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 eh3 -> eh4 uses path eh3 -> sw3 -> sw5 -> sw7 -> sw4 -> eh4, then the application will obtain 200 Mbps. Gao, et al. Expires January 9, 2020 [Page 6] Internet-Draft ALTO Extension: Path Vector July 2019 o Case 2: If eh1 -> eh2 uses the path eh1 -> sw1 -> sw5 -> sw7 -> sw2 -> eh2 and eh3 -> eh4 uses the path eh3 -> sw3 -> sw5 -> sw7 -> sw4 -> eh4, then the application will obtain only 100 Mbps due to the shared link from sw5 to sw7. To allow applications to distinguish the two aforementioned cases, the network needs to provide more details. In particular: 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 while providing enough information to applications. The path vector extension defined in this document provides a solution to address the preceding issue. See [I-D.bernstein-alto-topo] for a more comprehensive survey of use cases where extended network topology information is needed. 3.2. In-Network Caching Consider a network as shown in Figure 3. Two clients (C1/eh2 and C2/ eh3) are downloading data from a server (S/eh1) and the network provides an HTTP proxy which can cache results. The clients and the server are controlled by an ALTO client. +---------+ | Caching | -+ Proxy | / | | S +-------+ / +---------+ eh1__| sub |_ / | net 1 | \ +--|---+ +----------+ +-------+ ---| | | | C2 | Gate +---------+ Internet |__eh3 C1 +-------+ --| way | | | eh2__| sub |__/ +------+ +----------+ | net 2 | +-------+ Figure 3: Raw Topology for the In-Network Caching Use Case. Without the traffic correlation information, the ALTO client cannot know whether or how the traffic goes through the proxy. For example, if subnet1 and subnet2 are directly connected and the traffic from Gao, et al. Expires January 9, 2020 [Page 7] Internet-Draft ALTO Extension: Path Vector July 2019 eh1 to eh2 bypasses the gateway, the in-network cache can only be used for traffic from C2 to S and is less effective. 4. Overview This section presents an overview of approaches adopted by the path vector extension. It assumes that the readers are familiar with cost map and endpoint cost service defined in [RFC7285]. The path vector extension also requires the support of Filtered Property Map defined in [I-D.ietf-alto-unified-props-new]. The path vector extension is composed of three building blocks: (1) a new cost mode to encode path vectors in a cost map or an endpoint cost map; (2) a new ALTO entity domain to enable ANE property encoding using the unified property extension [I-D.ietf-alto-unified-props-new]; and (3) a generic mechanism to put multiple ALTO information objects in a single response to enforce consistency, to preserve modularity and to avoid complex linking of multiple responses. 4.1. New Cost Mode to Encode Path Vectors Existing cost modes defined in [RFC7285] allow only scalar cost values. However, the "path vector" abstraction requires to convey vector format information (AR-1). To fulfill this requirement, this document defines a new "cost-mode" named path vector to indicate that the cost value is an array of ANEs. A path vector abstraction should be computed for a specific performance metric, and this is achieved using the existing "cost-metric" component of cost type. The details of the new "cost-mode" is given in Section 5.2. 4.2. New ALTO Entity Domain for ANE Properties A path vector of ANEs contains only the abstracted routing elements between a source and a destination. Hence, an application can find shared ANEs of different source-destination pairs but cannot know the shared ANEs' properties. For the capacity region use case in Section 3.1, knowing that eh1->eh2 and eh3->eh4 share ANEs but not the available bandwidth of the shared ANEs, is not enough. To encode ANE properties like the available bandwidth in a path vector query response, this document uses the unified property extension defined in [I-D.ietf-alto-unified-props-new]. Specifically, for each path vector query, the ALTO server generates a property map associated to the (endpoint) cost map as follows: o a dynamic entity domain of an entity domain type "ane" is generated to contain the generated ANEs. Each ANE has the same Gao, et al. Expires January 9, 2020 [Page 8] Internet-Draft ALTO Extension: Path Vector July 2019 unique identifier in the path vectors and in the dynamic entity domain; o each entity in this dynamic entity domain has the properties specified by the client. Detailed information and specifications are given in Section 5.3. 4.3. Multipart/Related Resource for Consistency Path vectors and the property map containing the ANEs are two different types of objects, but they require strong consistency. One approach to achieving strong consistency is to define a new media type to contain both objects, but this violates modular design. Another approach is to provide the objects in two different information resources. Thus, an ALTO client needs to make separate queries to get the information of related services. This may cause a data synchronization problem between two queries. Also, as the generation of ANE is dynamic, an ALTO server must cache the results of a query before a client fully retrieves all related resources, which hurts the scalability and security of an ALTO server. This document uses standard-conforming usage of "multipart/related" media type defined in [RFC2387] to elegantly solve the problem. Specifically, using "multipart/related" needs to address two issues: o ALTO uses media type to indicate the type of an entry in the information resource directory (IRD) (e.g., "application/alto- costmap+json" for cost map and "application/alto- endpointcostmap+json" for endpoint cost map). Simply putting "multipart/related" as the media type, however, makes it impossible for an ALTO client to identify the type of service provided by related entries. o The ALTO SSE extension (see [I-D.ietf-alto-incr-update-sse]) depends on resource-id to identify push updates, but resource-id is provided only in IRD and hence each entry in the IRD has only one resource-id. This design addresses the two issues as follows: o To address the first issue, the multipart/related media type includes the type parameter to allow type indication of the root object. For a cost map service, the "media-type" will be "multipart/related" with the parameter "type=application/alto- costmap+json"; for an endpoint cost map service, the parameter Gao, et al. Expires January 9, 2020 [Page 9] Internet-Draft ALTO Extension: Path Vector July 2019 will be "type=application/alto-endpointcostmap+json". This design is highly extensible. The entries can still use "application/ alto-costmapfilter+json" or "application/alto- endpointcostparams+json" as the accept input parameters, and hence an ALTO client still sends the filtered cost map request or endpoint cost service request. The ALTO server sends the response as a "multipart/related" message. The body of the response includes two parts: the first one is of the media type specified by the "type" parameter; the second one is a property map associated to the first map. o To address the second issue, each part of the "multipart/related" response message has the MIME part header information including "Content-Type" and "Resource-Id". An ALTO server MAY generate incremental updates (see [I-D.ietf-alto-incr-update-sse]) for each part separately using the "Resource-Id" header. By applying the design above, for each path vector query, an ALTO server returns the path vectors and the associated property map modularly and consistently. An ALTO server can reuse the data models of the existing information resources. And an ALTO client can subscribe to the incremental updates for the dynamic generated information resources without any changes, if th ALTO server provides incremental updates for them. 5. Basic Data Types 5.1. ANE Identifier An ANE identifier is encoded as a JSON string. The string MUST be no more than 64 characters, and it MUST NOT contain characters other than US-ASCII alphanumeric characters (U+0030-U+0039, U+0041-U+005A, and U+0061-U+007A), the hyphen ("-", U+002D), the colon (":", U+003A), the at sign ("@", code point U+0040), the low line ("_", U+005F), or the "." separator (U+002E). The "." separator is reserved for future use and MUST NOT be used unless specifically indicated in this document, or an extension document. The type ANEIdentifier is used in this document to indicate a string of this format. 5.2. Path Vector Cost Type This document defines a new cost type, which is referred to as the "path vector" cost type. An ALTO server MUST offer this cost type if it supports the path vector extension. Gao, et al. Expires January 9, 2020 [Page 10] Internet-Draft ALTO Extension: Path Vector July 2019 5.2.1. Cost Metric: ane-path This cost metric conveys an array of ANE identifiers, where each identifier uniquely represents an ANE traversed by traffic from a source to a destination. 5.2.2. Cost Mode: array This cost mode indicates that every cost value in a cost map or an endpoint cost map MUST be interpreted as a JSON array object. Note that this cost mode only requires the cost value to be a JSON array of JSONValue. However, an ALTO server that enables this extension MUST return a JSON array of ANEIdentifier (Section 5.1) when the cost metric is "ane-path". 5.3. ANE Domain This document specifies a new ALTO entity domain called "ane" in addition to the ones in [I-D.ietf-alto-unified-props-new]. The ANE domain associates property values with the ANEs in a network. The entity in ANE domain is often used in the path vector by cost maps or endpoint cost resources. Accordingly, the ANE domain always depends on a cost map or an endpoint cost map. 5.3.1. Domain Name ane 5.3.2. Domain-Specific Entity Identifier The entity identifier of ANE domain uses the same encoding as ANEIdentifier (Section 5.1). 5.3.3. Hierarchy and Inheritance There is no hierarchy or inheritance for properties associated with ANEs. 5.4. ANE Properties 5.4.1. ANE Property: Maximum Reservable Bandwidth The maximum reservable bandwidth property conveys the maximum bandwidth that can be reserved for traffic from a source to a destination and is indicated by the property name "maxresbw". The value MUST be encoded as a numerical cost value as defined in Section 6.1.2.1 of [RFC7285] and the unit is bit per second. Gao, et al. Expires January 9, 2020 [Page 11] Internet-Draft ALTO Extension: Path Vector July 2019 If this property is requested but is missing for a given ANE, it MUST be interpreted as that the ANE does not support bandwidth reservation but have sufficiently large bandwidth for all traffic that traverses it. 5.4.2. ANE Property: Persistent Entity The persistent entity property conveys the physical or logical network entities (e.g., links, in-network caching service) that are contained by an abstract network element. It is indicated by the property name "persistent-entity". The value is encoded as a JSON array of entity identifiers ([I-D.ietf-alto-unified-props-new]). These entity identifiers are persistent so that a client CAN further query their properties for future use. If this property is requested but is missing for a given ANE, it MUST be interpreted as that no such entities exist in this ANE. 6. Service Extensions 6.1. Multipart Filtered Cost Map for Path Vector This document introduces a new ALTO resource called Multipart Filtered Cost Map resource, which allows an ALTO server to provide other ALTO resources associated to the Cost Map resource in the same response. 6.1.1. Media Type The media type of the Multipart Filtered Cost Map Resource is "multipart/related;type=application/alto-costmap+json". 6.1.2. HTTP Method The Multipart Filtered Cost Map is requested using the HTTP POST method. 6.1.3. Accept Input Parameters The input parameters of the Multipart Filtered Cost Map are supplied in the body of an HTTP POST request. This document extends the input parameters to a filtered Cost Map with a data format indicated by the media type "application/alto-costmapfilter+json", which is a JSON object of type PVReqFilteredCostMap, where: object { [PropertyName ane-properties<0..*>;] } PVReqFilteredCostMap : ReqFilteredCostMap; Gao, et al. Expires January 9, 2020 [Page 12] Internet-Draft ALTO Extension: Path Vector July 2019 with fields: ane-properties: A list of properties that are associated with the ANEs. Each property in this list MUST match one of the supported ANE properties indicated in the resource's "ane-properties" capability. If the field is NOT present, it MUST be interpreted as an empty list, indicating that the ALTO server MUST NOT return any property in the unified property part. 6.1.4. Capabilities The Multipart Filtered Cost Map resource extends the capabilities defined in Section 11.3.2.4 of [RFC7285]. The capabilities are defined by a JSON object of type PVFilteredCostMapCapabilities: object { [PropertyName ane-properties<0..*>;] } PVFilteredCostMapCapabilities : FilteredCostMapCapabilities; with fields: cost-type-names: The "cost-type-names" field MUST only include the path vector cost type, unless explicitly documented by a future extension. This also implies that the path vector cost type MUST be defined in the "cost-types" of the Information Resource Directory's "meta" field. ane-properties: Defines a list of ANE properties that can be returned. If the field is NOT present, it MUST be interpreted as an empty list, indicating the ALTO server CANNOT provide any ANE property. 6.1.5. Uses The resource ID of the network map based on which the PIDs in the returned cost map will be defined. If this resource supports "persistent-entities", it MUST also include ALL the resources that exposes the entities that MAY appear in the response. 6.1.6. Response The response MUST indicate an error, using ALTO protocol error handling, as defined in Section 8.5 of [RFC7285], if the request is invalid. The "Content-Type" header of the response MUST be "multipart/related" as defined by [RFC2387] with the following parameters: Gao, et al. Expires January 9, 2020 [Page 13] Internet-Draft ALTO Extension: Path Vector July 2019 type: The type parameter MUST be "application/alto-costmap+json". Note that [RFC2387] permits both parameters with and without the double quotes. start: The start parameter MUST be a quoted string where the quoted part has the same value as the "Resource-ID" header in the first part. boundary: The boundary parameter is as defined in [RFC2387]. The body of the response consists of two parts. The first part MUST include "Resource-Id" and "Content-Type" in its header. The value of "Resource-Id" MUST be prefixed by the resource id of the Multipart Filtered Cost Map appended by a "." character. The "Content-Type" MUST be "application/alto-costmap+json". The body of the first part MUST be a JSON object with the same format as defined in Section 11.2.3.6 of [RFC7285]. The JSON object MUST include the "vtag" field in the "meta" field, which provides the version tag of the returned cost map. The resource id of the version tag MUST be the same as the value of the "Resource-Id" header. The "meta" field MUST also include the "dependent-vtags" field, whose value is a single-element array to indicate the version tag of the network map used, where the network map is specified in the "uses" attribute of the Multipart Cost Map resource in IRD. The second part MUST also include "Resource-Id" and "Content-Type" in its header. The value of "Resource-Id" MUST be prefixed by the resource id of the Multipart Filtered Cost Map appended by a "." character. The "Content-Type" MUST be "application/alto- propmap+json". The body of the second part MUST be a JSON object with the same format as defined in Section 4.6 of [I-D.ietf-alto-unified-props-new]. The JSON object MUST include the "dependent-vtags" field in the "meta" field. The value of the "dependent-vtags" field MUST be an array of VersionTag objects as defined by Section 10.3 of [RFC7285]. The "vtag" of the first part MUST be included in the "dependent-vtags". If "persistent-entities" is requested, the version tags of the dependent resources that MAY expose the entities in the response MUST also be included. The PropertyMapData has one member for each ANE identifier that appears in the first part, where the EntityProps has one member for each property requested by the client if applicable. Gao, et al. Expires January 9, 2020 [Page 14] Internet-Draft ALTO Extension: Path Vector July 2019 6.2. Multipart Endpoint Cost Service for Path Vector This document introduces a new ALTO resource called Multipart Endpoint Cost resource, which allows an ALTO server to provide other ALTO resources associated to the Endpoint Cost resource in the same response. 6.2.1. Media Type The media type of the Multipart Endpoint Cost Resource is "multipart/related;type=application/alto-endpointcostmap+json". 6.2.2. HTTP Method The Multipart Endpoint Cost resource is requested using the HTTP POST method. 6.2.3. Accept Input Parameters The input parameters of the Multipart Endpoint Cost resource are supplied in the body of an HTTP POST request. This document extends the input parameters to an Endpoint Cost Map with a data format indicated by the media type "application/alto- endpointcostparams+json", which is a JSON object of type PVEndpointCostParams, where object { [PropertyName ane-properties<0..*>;] } PVReqEndpointCostMap : ReqEndpointCostMap; with fields: ane-properties: This document defines the "ane-properties" in PVReqEndpointCostMap as the same as in PVReqFilteredCostMap. See Section 6.1.3. 6.2.4. Capabilities The capabilities of the Multipart Endpoint Cost Service are defined by a JSON object of type PVEndpointCostMapCapabilities, which is defined as the same as PVFilteredCostMapCapabilities. See Section 6.1.4. 6.2.5. Uses If a Multipart Endpoint Cost resource supports "persistent-entities", the "uses" field in its IRD entry MUST include ALL the resources which exposes the entities that MAY appear in the response. Gao, et al. Expires January 9, 2020 [Page 15] Internet-Draft ALTO Extension: Path Vector July 2019 6.2.6. Response The response MUST indicate an error, using ALTO protocol error handling, as defined in Section 8.5 of [RFC7285], if the request is invalid. The "Content-Type" header of the response MUST be "multipart/related" as defined by [RFC2387] with the following parameters: type: The type parameter MUST be "application/alto- endpointcostmap+json". start: The start parameter MUST be a quoted string where the quoted part has the same value as the "Resource-ID" header in the first part. boundary: The boundary parameter is as defined in [RFC2387]. The body consists of two parts: The first part MUST include "Resource-Id" and "Content-Type" in its header. The value of "Resource-Id" MUST be prefixed by the resource id of the Multipart Endpoint Cost Service appended by a "." character (U+002E). The "Content-Type" MUST be "application/alto- endpointcostmap+json". The body of the first part MUST be a JSON object with the same format as defined in Section 11.5.1.6 of [RFC7285]; The JSON object MUST include the "vtag" field in the "meta" field, which provides the version tag of the returned endpoint cost map. The resource id of the version tag MUST be the same as the value of the "Resource-Id" header. The second part MUST also include "Resource-Id" and "Content-Type" in its header. The value of "Resource-Id" MUST be prefixed by the resource id of the Multipart Filtered Cost Map appended by a "." character (U+002E). The "Content-Type" MUST be "application/alto- propmap+json". The body of the second part MUST be a JSON object with the same format as defined in Section 4.6 of [I-D.ietf-alto-unified-props-new]. The JSON object MUST include the "dependent-vtags" field in the "meta" field. The value of the "dependent-vtags" field MUST be an array of VersionTag objects as defined by Section 10.3 of [RFC7285]. The "vtag" of the first part MUST be included in the "dependent-vtags". If "persistent-entities" is requested, the version tags of the dependent resources that MAY expose the entities in the response MUST also be included. The Gao, et al. Expires January 9, 2020 [Page 16] Internet-Draft ALTO Extension: Path Vector July 2019 PropertyMapData has one member for each ANE identifier that appears in the first part, where the EntityProps has one member for each property requested by the client if applicable. 7. Examples This section lists some examples of path vector queries and the corresponding responses. Some long lines are truncated for better readability. 7.1. Information Resource Directory Example Below is an example of an Information Resource Directory which enables the path vector extension. Some critical modifications include: o The "path-vector" cost type (Section 5.2) is defined in the "cost- types" of the "meta" field. o The "cost-map-pv" information resource provides a Multipart Cost Map resource, which exposes the Maximum Reservable Bandwidth ("maxresbw") property. o The "http-proxy-props" information resource provides a filtered Unified Property Map resource, which exposes the HTTP proxy entity domain (encoded as "http-proxy") and the "price" property. Note that HTTP proxy is NOT a valid entity domain yet and is used here only for demonstration. o The "endpoint-cost-pv" information resource provides a Multipart Endpoint Cost Service. It exposes the Maximum Reservable Bandwidth ("maxresbw") property and the Persistent Entity property. The persistent entities MAY come from the "http-proxy- props" resource. o The "update-pv" information resource provides the incremental update ([I-D.ietf-alto-incr-update-sse]) service for the "endpoint-cost-pv" resource. { "meta": { "cost-types": { "path-vector": { "cost-mode": "array", "cost-metric": "ane-path" } } }, Gao, et al. Expires January 9, 2020 [Page 17] Internet-Draft ALTO Extension: Path Vector July 2019 "resources": { "my-default-networkmap": { "uri" : "http://alto.example.com/networkmap", "media-type" : "application/alto-networkmap+json" }, "cost-map-pv": { "uri": "http://alto.example.com/costmap/pv", "media-type": "multipart/related; type=application/alto-costmap+json", "accepts": "application/alto-costmapfilter+json", "capabilities": { "cost-type-names": [ "path-vector" ], "ane-properties": [ "maxresbw" ] }, "uses": [ "my-default-networkmap" ] }, "http-proxy-props": { "uri": "http://alto.example.com/proxy-props", "media-type": "application/alto-propmap+json", "accpets": "application/alto-propmapparams+json", "capabilities": { "mappings": { "http-proxy": [ "price" ] } } }, "endpoint-cost-pv": { "uri": "http://alto.exmaple.com/endpointcost/pv", "media-type": "multipart/related; type=application/alto-endpointcost+json", "accepts": "application/alto-endpointcostparams+json", "capabilities": { "cost-type-names": [ "path-vector" ], "ane-properties": [ "maxresbw", "persistent-entities" ] }, "uses": [ "http-proxy-props" ] }, "update-pv": { "uri": "http://alto.example.com/updates/pv", "media-type": "text/event-stream", "uses": [ "endpoint-cost-pv" ], "accepts": "application/alto-updatestreamparams+json", "capabilities": { "support-stream-control": true } } } } Gao, et al. Expires January 9, 2020 [Page 18] Internet-Draft ALTO Extension: Path Vector July 2019 7.2. Example: Multipart Filtered Cost Map The following examples demonstrate the request to the "cost-map-pv" resource and the corresponding response. The request uses the path vector cost type in the "cost-type" field. The "ane-properties" field is missing, indicating that the client only requests for the path vector but not the ANE properties. The response consists of two parts. The first part returns the array of ANE identifiers for each source and destination pair. There are three ANEs, where "ane:L001" is shared by traffic from "PID1" to both "PID2" and "PID3". The second part returns an empty property map. Note that the ANE entries are omitted since they have no properties (See Section 3.1 of [I-D.ietf-alto-unified-props-new]). POST /costmap/pv HTTP/1.1 Host: alto.example.com Accept: multipart/related;type=application/alto-costmap+json, application/alto-error+json Content-Length: [TBD] Content-Type: application/alto-costmapfilter+json { "cost-type": { "cost-mode": "array", "cost-metric": "ane-path" }, "pids": { "srcs": [ "PID1" ], "dsts": [ "PID2", "PID3" ] } } HTTP/1.1 200 OK Content-Length: [TBD] Content-Type: multipart/related; boundary=example-1; start=cost-map-pv.costmap; type=application/alto-costmap+json --example-1 Resource-Id: cost-map-pv.costmap Content-Type: application/alto-costmap+json { Gao, et al. Expires January 9, 2020 [Page 19] Internet-Draft ALTO Extension: Path Vector July 2019 "meta": { "vtag": { "resource-id": "cost-map-pv.costmap", "tag": "d827f484cb66ce6df6b5077cb8562b0a" }, "dependent-vtags": [ { "resource-id": "my-default-networkmap", "tag": "75ed013b3cb58f896e839582504f6228" } ], "cost-type": { "cost-mode": "array", "cost-metric": "ane-path" } }, "cost-map": { "PID1": { "PID2": [ "ane:L001", "ane:L003" ], "PID3": [ "ane:L001", "ane:L004" ] } } } --example-1 Resource-Id: cost-map-pv.propmap Content-Type: application/alto-propmap+json { "meta": { "dependent-vtags": [ { "resource-id": "cost-map-pv.costmap", "tag": "d827f484cb66ce6df6b5077cb8562b0a" } ] }, "property-map": { } } 7.3. Example: Multipart Endpoint Cost Service The following examples demonstrate the request to the "endpoint-cost- pv" resource and the corresponding response. The request uses the path vector cost type in the "cost-type" field, and queries the Maximum Reservable Bandwidth ANE property and the Persistent Entity property. Gao, et al. Expires January 9, 2020 [Page 20] Internet-Draft ALTO Extension: Path Vector July 2019 The response consists of two parts. The first part returns the array of ANE identifiers for each valid source and destination pair. The second part returns the requested properties of ANEs in the first part. The "ane:NET001" element contains an HTTP proxy entity, which can be further used by the client. Since it does not contain a "maxresbw" property, the client SHOULD assume it does NOT support bandwidth reservation but will NOT become a traffic bottleneck, as specified in Section 5.4.1. POST /endpointcost/pv HTTP/1.1 Host: alto.example.com Accept: multipart/related; type=application/alto-endpointcost+json, application/alto-error+json Content-Length: [TBD] Content-Type: application/alto-endpointcostparams+json { "cost-type": { "cost-mode": "array", "cost-metric": "ane-path" }, "endpoints": { "srcs": [ "ipv4:192.0.2.2" ], "dsts": [ "ipv4:192.0.2.89", "ipv4:203.0.113.45", "ipv6:2001:db8::10" ] }, "ane-properties": [ "maxresbw", "persistent-entities" ] } HTTP/1.1 200 OK Content-Length: [TBD] Content-Type: multipart/related; boundary=example-2; start=endpoint-cost-pv.ecs; type=application/alto-endpointcost+json --example-2 Resource-Id: endpoint-cost-pv.ecs Content-Type: application/alto-endpointcost+json { "meta": { "vtags": { "resource-id": "endpoint-cost-pv.ecs", "tag": "bb6bb72eafe8f9bdc4f335c7ed3b10822a391cef" }, Gao, et al. Expires January 9, 2020 [Page 21] Internet-Draft ALTO Extension: Path Vector July 2019 "cost-type": { "cost-mode": "array", "cost-metric": "ane-path" } }, "endpoint-cost-map": { "ipv4:192.0.2.2": { "ipv4:192.0.2.89": [ "ane:NET001", "ane:L002" ], "ipv4:203.0.113.45": [ "ane:NET001", "ane:L003" ] } } } --example-2 Resource-Id: endpoint-cost-pv.propmap Content-Type: application/alto-propmap+json { "meta": { "dependent-vtags": [ { "resource-id": "endpoint-cost-pv.ecs", "tag": "bb6bb72eafe8f9bdc4f335c7ed3b10822a391cef" }, { "resource-id": "http-proxy-props", "tag": "bf3c8c1819d2421c9a95a9d02af557a3" } ] }, "property-map": { "ane:NET001": { "persistent-entities": [ "http-proxy:192.0.2.1" ] }, "ane:L002": { "maxresbw": 48000000 }, "ane:L003": { "maxresbw": 35000000 } } } 7.4. Example: Incremental Updates In this example, an ALTO client subscribes to the incremental update for the Multipart Endpoint Cost resource "endpoint-cost-pv". Gao, et al. Expires January 9, 2020 [Page 22] Internet-Draft ALTO Extension: Path Vector July 2019 POST /updates/pv HTTP/1.1 Host: alto.example.com Accept: text/event-stream Content-Type: application/alto-updatestreamparams+json Content-Length: [TBD] { "add": { "ecspvsub1": { "resource-id": "endpoint-cost-pv", "input": } } } Based on the server-side process defined in [I-D.ietf-alto-incr-update-sse], the ALTO server will send the "control-uri" first using Server-Sent Event (SSE), followed by the full response of the multipart message. HTTP/1.1 200 OK Connection: keep-alive Content-Type: text/event-stream event: application/alto-updatestreamcontrol+json data: {"control-uri": "http://alto.example.com/updates/streams/1414"} event: multipart/related;boundary=example-3;start=pvmap; type=application/alto-endpointcost+json,ecspvsub1 data: --example-3 data: Resource-ID: endpoint-cost-pv.ecsmap02695067 data: Content-Type: application/alto-endpointcost+json data: data: data: --example-3 data: Resource-ID: endpoint-cost-pv.propmapbbc868aa data: Content-Type: application/alto-propmap+json data: data: data: --example-3-- When the contents change, the ALTO server will publish the updates for each node in this tree separately. Gao, et al. Expires January 9, 2020 [Page 23] Internet-Draft ALTO Extension: Path Vector July 2019 event: application/merge-patch+json, ecspvsub1.endpoint-cost-pv.ecsmap02695067 data: event: application/merge-patch+json, ecspvsub1.endpoint-cost-pv.propmapbbc868aa data: 8. Compatibility 8.1. Compatibility with Base ALTO Clients/Servers The Multipart Filtered Cost Map resource and the Multipart Endpoint Cost resource has no backward compatibility issue with the base ALTO clients and servers. Although these two types of resources reuse the media types defined in the base ALTO protocol for the accept input parameters, they have different media types for responses. If the ALTO server provides these two types of resources, but the ALTO client does not support them, the ALTO client will ignore the resources without conducting any incompatibility. 8.2. Compatibility with Multi-Cost Extension This document does not specify how to integrate the "path-vector" cost mode with the multi-cost extension [RFC8189]. Although there is no reason why somebody has to compound the path vectors with other cost types in a single query, there is no compatible issue doing it without constraint tests. 8.3. Compatibility with Incremental Update As this document still follows the basic request/response protocol with JSON encoding, it is surely compatible with the incremental update service as defined by [I-D.ietf-alto-incr-update-sse]. But the following details are to be noticed: o When using the compound response, updates on both cost map and property map SHOULD be notified. o When not using the compound response, because the cost map is in the "uses" attribute of the property map, once the path vectors in the cost map change, the ALTO server MUST send the updates of the cost map before the updates of the property map. Gao, et al. Expires January 9, 2020 [Page 24] Internet-Draft ALTO Extension: Path Vector July 2019 9. General Discussions 9.1. Provide Calendar for Property Map Fetching the historical network information is useful for many traffic optimization problem. [I-D.ietf-alto-cost-calendar] already proposes an ALTO extension called Cost Calendar which provides the historical cost values using Filtered Cost Map and Endpoint Cost Service. However, the calendar for only path costs is not enough. For example, as the properties of ANEs (e.g., available bandwidth and link delay) are usually the real-time network states, they change frequently in the real network. It is very helpful to get the historical value of these properties. Applications may predicate the network status using these information to better optimize their performance. So the coming requirement may be a general calendar service for the ALTO information resources. 9.2. Constraint Tests for General Cost Types The constraint test is a simple approach to query the data. It allows users to filter the query result by specifying some boolean tests. This approach is already used in the ALTO protocol. [RFC7285] and [RFC8189] allow ALTO clients to specify the "constraints" and "or-constraints" tests to better filter the result. However, the current defined syntax is too simple and can only be used to test the scalar cost value. For more complex cost types, like the "array" mode defined in this document, it does not work well. It will be helpful to propose more general constraint tests to better perform the query. In practice, it is too complex to customize a language for the general-purpose boolean tests, and can be a duplicated work. So it may be a good idea to integrate some already defined and widely used query languages (or their subset) to solve this problem. The candidates can be XQuery and JSONiq. 9.3. General Multipart Resources Query Querying multiple ALTO information resources continuously MAY be a general requirement. And the coming issues like inefficiency and inconsistency are also general. There is no standard solving these issues yet. So we need some approach to make the ALTO client request the compound ALTO information resources in a single query. Gao, et al. Expires January 9, 2020 [Page 25] Internet-Draft ALTO Extension: Path Vector July 2019 10. Security Considerations This document is an extension of the base ALTO protocol, so the Security Considerations [RFC7285] of the base ALTO protocol fully apply when this extension is provided by an ALTO server. The path vector extension requires additional considerations on two security considerations discussed in the base protocol: confidentiality of ALTO information (Section 15.3 of [RFC7285]) and availability of ALTO service (Section 15.5 of [RFC7285]). For confidentiality of ALTO information, a network operator should be aware of that this extension may introduce a new risk: the path vector information may make network attacks easier. For example, as the path vector information may reveal more network internal structures than the more abstract single-node abstraction, an ALTO client may detect the bottleneck link and start a distributed denial- of-service (DDoS) attack involving minimal flows to conduct the in- network congestion. To mitigate this risk, the ALTO server should consider protection mechanisms to reduce information exposure or obfuscate the real information, in particular, in settings where the network and the application do not belong to the same trust domain. But the implementation of path vector extension involving reduction or obfuscation should guarantees the constraints on the requested properties are still accurate. For availability of ALTO service, an ALTO server should be cognizant that using path vector extension might have a new risk: frequent requesting for path vectors might conduct intolerable increment of the server-side storage and break the ALTO server. It is known that the computation of path vectors is unlikely to be cacheable, in that the results will depend on the particular requests (e.g., where the flows are distributed). Hence, the service providing path vectors may become an entry point for denial-of-service attacks on the availability of an ALTO server. To avoid this risk, authenticity and authorization of this ALTO service may need to be better protected. Even if there is no intentional attack, the dependent property map of path vector might be still dynamically enriched, in that every new request for path vectors will make the ALTO server generate a new property map. So the properties of the abstract network elements can consume a large amount of resources when cached. To avoid this, the ALTO server providing the path vector extension should support a time-to-live configuration for the property map, so that the outdated entries can be removed from the property map resource. Gao, et al. Expires January 9, 2020 [Page 26] Internet-Draft ALTO Extension: Path Vector July 2019 11. IANA Considerations 11.1. ALTO Cost Mode Registry This document specifies a new cost mode "path-vector". However, the base ALTO protocol does not have a Cost Mode Registry where new cost mode can be registered. This new cost mode will be registered once the registry is defined either in a revised version of [RFC7285] or in another future extension. 11.2. ALTO Entity Domain Registry As proposed in Section 9.2 of [I-D.ietf-alto-unified-props-new], "ALTO Domain Entity Registry" is requested. Besides, a new domain is to be registered, listed in Table 1. +-------------+--------------------------+--------------------------+ | Identifier | Entity Address Encoding | Hierarchy & Inheritance | +-------------+--------------------------+--------------------------+ | ane | See Section 5.3.2 | None | +-------------+--------------------------+--------------------------+ Table 1: ALTO Entity Domain 11.3. ALTO Property Type Registry The "ALTO Property Type Registry" is required by the ALTO Domain "ane", listed in Table 2. +-------------+------------+----------------------------------------+ | Identifier | Intended | Dependencies and Interpretation | | | Semantics | | +-------------+------------+----------------------------------------+ | ane:maxresb | The | application/alto-costmap+json, or | | w | maximum | application/alto-endpointcostmap+json, | | | reservable | where the ANE names are used. | | | bandwidth | | | | for the | | | | ANE | | +-------------+------------+----------------------------------------+ Table 2: 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. The authors thank Greg Gao, et al. Expires January 9, 2020 [Page 27] Internet-Draft ALTO Extension: Path Vector July 2019 Bernstein (Grotto Networks), Dawn Chen (Tongji University), Wendy Roome, and Michael Scharf for their contributions to earlier drafts. 13. References 13.1. Normative References [I-D.ietf-alto-incr-update-sse] Roome, W. and Y. Yang, "ALTO Incremental Updates Using Server-Sent Events (SSE)", draft-ietf-alto-incr-update- sse-16 (work in progress), March 2019. [I-D.ietf-alto-unified-props-new] Roome, W., Randriamasy, S., Yang, Y., and J. Zhang, "Unified Properties for the ALTO Protocol", draft-ietf- alto-unified-props-new-07 (work in progress), March 2019. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [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, . [RFC8189] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost Application-Layer Traffic Optimization (ALTO)", RFC 8189, DOI 10.17487/RFC8189, October 2017, . 13.2. Informative References [I-D.bernstein-alto-topo] Bernstein, G., Yang, Y., and Y. Lee, "ALTO Topology Service: Uses Cases, Requirements, and Framework", draft- bernstein-alto-topo-00 (work in progress), October 2013. [I-D.ietf-alto-cost-calendar] Randriamasy, S., Yang, Y., Wu, Q., Lingli, D., and N. Schwan, "ALTO Cost Calendar", draft-ietf-alto-cost- calendar-01 (work in progress), February 2017. Gao, et al. Expires January 9, 2020 [Page 28] Internet-Draft ALTO Extension: Path Vector July 2019 [I-D.ietf-alto-performance-metrics] Wu, Q., Yang, Y., Lee, Y., Dhody, D., and S. Randriamasy, "ALTO Performance Cost Metrics", draft-ietf-alto- performance-metrics-06 (work in progress), November 2018. Authors' Addresses Kai Gao Sichuan University Chengdu 610000 China Email: kai.gao@scu.edu.cn Young Lee Huawei TX USA Email: leeyoung@huawei.com Sabine Randriamasy Nokia Bell Labs Route de Villejust NOZAY 91460 FRANCE Email: Sabine.Randriamasy@nokia-bell-labs.com Y. Richard Yang Yale University 51 Prospect St New Haven CT USA Email: yry@cs.yale.edu Jingxuan Jensen Zhang Tongji University 4800 Caoan Road Shanghai 201804 China Email: jingxuan.n.zhang@gmail.com Gao, et al. Expires January 9, 2020 [Page 29]