ALTO WG K. Gao Internet-Draft Tsinghua University Intended status: Standards Track Y. Lee Expires: September 12, 2019 Huawei S. Randriamasy Nokia Bell Labs Y. Yang Yale University J. Zhang Tongji University March 11, 2019 ALTO Extension: Path Vector Cost Type draft-ietf-alto-path-vector-05 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 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 Gao, et al. Expires September 12, 2019 [Page 1] Internet-Draft ALTO Extension: Path Vector March 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 September 12, 2019. Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Use Case: Capacity Region for Co-Flow Scheduling . . . . . . 5 4. Overview of Path Vector Extensions . . . . . . . . . . . . . 7 4.1. New Cost Type to Encode Path Vectors . . . . . . . . . . 7 4.2. New ALTO Entity Domain to Provide ANE Properties . . . . 8 4.3. Extended Cost Map/Endpoint Cost Service for Compound Resources . . . . . . . . . . . . . . . . . . . . . . . . 8 5. Cost Type . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1. Cost Mode: array . . . . . . . . . . . . . . . . . . . . 9 5.2. Cost Metric: ane-path . . . . . . . . . . . . . . . . . . 9 5.3. Path Vector Cost Type Semantics . . . . . . . . . . . . . 9 6. ANE Domain . . . . . . . . . . . . . . . . . . . . . . . . . 10 6.1. Domain Name . . . . . . . . . . . . . . . . . . . . . . . 10 6.2. Domain-Specific Entity Addresses . . . . . . . . . . . . 10 6.3. Hierarchy and Inheritance . . . . . . . . . . . . . . . . 10 7. Protocol Extensions for Path Vector . . . . . . . . . . . . . 10 7.1. Filtered Cost Map Extensions . . . . . . . . . . . . . . 11 7.1.1. Accept Input Parameters . . . . . . . . . . . . . . . 11 7.1.2. Capabilities . . . . . . . . . . . . . . . . . . . . 11 7.1.3. Response . . . . . . . . . . . . . . . . . . . . . . 12 7.2. Endpoint Cost Service Extensions . . . . . . . . . . . . 12 7.2.1. Accept Input Parameters . . . . . . . . . . . . . . . 13 7.2.2. Capabilities . . . . . . . . . . . . . . . . . . . . 13 7.2.3. Response . . . . . . . . . . . . . . . . . . . . . . 13 8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Gao, et al. Expires September 12, 2019 [Page 2] Internet-Draft ALTO Extension: Path Vector March 2019 8.1. Workflow . . . . . . . . . . . . . . . . . . . . . . . . 13 8.2. Information Resource Directory Example . . . . . . . . . 14 8.3. Example # 1 . . . . . . . . . . . . . . . . . . . . . . . 16 8.4. Example # 2 . . . . . . . . . . . . . . . . . . . . . . . 18 8.5. Example #3 . . . . . . . . . . . . . . . . . . . . . . . 20 9. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 22 9.1. Compatibility with Base ALTO Clients/Servers . . . . . . 22 9.2. Compatibility with Multi-Cost Extension . . . . . . . . . 23 9.3. Compatibility with Incremental Update . . . . . . . . . . 23 10. General Discussions . . . . . . . . . . . . . . . . . . . . . 23 10.1. Provide Calendar for Property Map . . . . . . . . . . . 23 10.2. Constraint Tests for General Cost Types . . . . . . . . 24 10.3. General Compound Resources Query . . . . . . . . . . . . 24 11. Security Considerations . . . . . . . . . . . . . . . . . . . 24 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 12.1. ALTO Cost Mode Registry . . . . . . . . . . . . . . . . 25 12.2. ALTO Cost Metric Registry . . . . . . . . . . . . . . . 26 12.3. ALTO Entity Domain Registry . . . . . . . . . . . . . . 26 12.4. ALTO Network Element Property Type Registry . . . . . . 26 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 27 14.1. Normative References . . . . . . . . . . . . . . . . . . 27 14.2. Informative References . . . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 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. To support capabilities like co-flow scheduling, this document uses a "path vector" abstraction to represent more detailed network graph information like capacity regions. The path vector abstraction uses path vectors with abstract network elements to provide network graph view for applications. A path vector consists of a sequence of abstract network elements (ANEs) that end-to-end traffic goes through. Example ANEs include links, switches, middleboxes, and their aggregations. An ANE can have properties such as "bandwidth", "delay". Providing such information can help both applications to Gao, et al. Expires September 12, 2019 [Page 3] Internet-Draft ALTO Extension: Path Vector March 2019 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 capacity regions. AR-3: The path vector abstraction requires consistent encoding of path vectors (AR-1) and the properties of the elements in a path vector (AR-2). Specifically, path vectors and the properties of abstract network elements in the vectors are dependent. A mechanism to query both of them consistently is necessary. This document proposes the path vector extension which satisfies these additional requirements to the ALTO protocol. Specifically, the ALTO protocol encodes the array of ANEs over an end-to-end path using a new cost type, and conveys the properties of ANEs using unified property map [I-D.ietf-alto-unified-props-new]. We also provide an optional solution to query separated path vectors and properties of ANEs in a consistent way. But querying general separated resources consistently is not the scope in this document. The rest of this document is organized as follows. Section 3 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 introduces a new cost type. Section 6 registers a new domain in Domain Registry. Section 7 extends Filtered Cost Map and Endpoint Cost Service to support the compound resource query. Section 8 presents several Gao, et al. Expires September 12, 2019 [Page 4] Internet-Draft ALTO Extension: Path Vector March 2019 examples. Section 9 and Section 10 discusses compatibility issues with other existing ALTO extensions and design decisions. Section 11 and Section 12 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, 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), 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: 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 can not 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 of link eh1 -> sw1 and link sw1 -> sw5 are 150 Mbps, and the bandwidth of the rest links are 100 Mbps. Gao, et al. Expires September 12, 2019 [Page 5] Internet-Draft ALTO Extension: Path Vector March 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 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. 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 at most. Gao, et al. Expires September 12, 2019 [Page 6] Internet-Draft ALTO Extension: Path Vector March 2019 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 at most. 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 propose a solution to provide these details. See [I-D.bernstein-alto-topo] for a more comprehensive survey of use cases where extended network topology information is needed. 4. Overview of Path Vector Extensions This section presents an overview of approaches adopted by the path vector extension. It assumes 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 type to encode path vectors; (2) a new ALTO entity domain for unified property extension [I-D.ietf-alto-unified-props-new] to encode properties of ANEs; and (3) an extension to the cost map and endpoint cost resource to provide path vectors and properties of ANEs in a single response. 4.1. New Cost Type to Encode Path Vectors Existing cost types defined in [RFC7285] allow only scalar cost values. However, the "path vector" abstraction requires to convey vector format information. To achieve this requirement, this document defines a new cost mode to enable the cost value to carry an array of elements, and a new cost metric to take names of ANEs as elements in the array. We call such an array of ANEs a path vector. In this way, the cost map and endpoint cost service can convey the path vector to represent the routing information. Detailed information and specifications are given in Section 5.1 and Section 5.2. Gao, et al. Expires September 12, 2019 [Page 7] Internet-Draft ALTO Extension: Path Vector March 2019 4.2. New ALTO Entity Domain to Provide ANE Properties The path vector can only represent the route between the source and the destination. Although the application can find the shared ANEs among different paths, it is not enough for most use cases, which requires the bandwidth or delay information of the ANEs. So this document adopts the property map defined in [I-D.ietf-alto-unified-props-new] to provide the general properties of ANEs. The document registers a new entity domain called "ane" to represent the ANE. The address of the ANE entity is just the ANE name used by the path vector. By requesting the property map of entities in the "ane" domain, the client can retrieve the properties of ANEs in path vectors. 4.3. Extended Cost Map/Endpoint Cost Service for Compound Resources Providing the path vector information and the ANE properties by separated resources have several known benefits: (1) can be better compatible with the base ALTO protocol; (2) can make different property map resources reuse the same cost map or endpoint cost resource. However, it conducts two issues: o Efficiency: The separated resources will require the ALTO client to invoke multiple requests/responses to collect all needed information. It increases the communication overhead. o Consistency: The path vectors and properties of ANEs are correlated. So querying them one by one may conduct consistency issue. Once the path vector changes during the client requests the ANE properties, the ANE properties may be inconsistent with the previous path vector. To solve these issues, this document introduces an extension to cost map and endpoint cost service, which allows the ALTO server to attach a property map in the data entry of a cost map or an endpoint cost service response. These issues may exist in all general cases for querying separated ALTO information resources. But solving this general problem is not in the scope of this document. 5. 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". In the rest content, this document uses "path- vector" to indicate the combination cost type of the cost mode "array" and the cost metric "ane-path". Gao, et al. Expires September 12, 2019 [Page 8] Internet-Draft ALTO Extension: Path Vector March 2019 5.1. Cost Mode: array This document extends the CostMode defined in Section 10.5 of [RFC7285] with a new cost mode: "array". This cost mode indicates that every cost value in a cost map represents an array rather than a simple value. The values are arrays of JSONValue. The specific type of each element in the array depends on the cost metric. 5.2. Cost Metric: ane-path This document specifies a new cost metric: "ane-path". This cost metric indicates that the cost value is a list of ANEs which the path from a source to a destination goes across. The values are arrays of ANE names which are defined in Section 6.2. The cost metric "ane-path" SHOULD NOT be used when the cost mode is not "array" unless it is explicitly specified by a future extension. If an ALTO client send queries with the cost metric "ane-path" and a non "array" cost mode, the ALTO server SHOULD return an error with the error code "E_INVALID_FIELD_VALUE"; If an ALTO server declares the support of a cost type with the cost metric "ane-path" and a non "array" cost mode, the ALTO client SHOULD assume such a cost type is invalid and ignore it. 5.3. Path Vector Cost Type Semantics The new cost type follows the convention of the cost types in the base ALTO protocol. Table 1 lists some of the current defined cost types and their semantics. +------------+--------------+---------------------------------------+ | Cost Mode | Cost Metric | Semantics | +------------+--------------+---------------------------------------+ | numerical | routingcost | a number representing the routing | | | | cost | | numerical | hopcount | a number representing the hop count | | ordinal | routingcost | a ranking 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 Semantics The "routingcost" and "hopcount" can encoded in "numerical" or "ordinal", however, the cost metric "ane-path" can only be applied to the cost mode "array" defined in this document to convey path vector information. The cost metric "ane-path" can not be used in Gao, et al. Expires September 12, 2019 [Page 9] Internet-Draft ALTO Extension: Path Vector March 2019 "numerical" or "ordinal" unless it is defined in future extensions. If the ALTO server declares that it support cost type with cost metric being "ane-path" and cost mode not being "array", the ALTO client SHOULD ignore them. 6. 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. 6.1. Domain Name ane 6.2. 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. To simplify the description, we use "ANE name" to indicate the address of an entity in ANE domain in this document. The ANE name is usually unrelated to the physical device information. It is usually generated by the ALTO server on demand and used to distinguish from other ANEs in its dependent cost map or endpoint cost map. 6.3. Hierarchy and Inheritance There is no hierarchy or inheritance for properties associated with ANEs. 7. Protocol Extensions for Path Vector To make the ALTO client query the path vectors and properties of ANEs efficiently and consistently, this document extends the Filtered Cost Map and Endpoint Cost Service. Gao, et al. Expires September 12, 2019 [Page 10] Internet-Draft ALTO Extension: Path Vector March 2019 7.1. Filtered Cost Map Extensions This document extends Filtered Cost Map, as defined in Section 11.3.2 of [RFC7285], by adding new input parameters and capabilities, and by augmenting the property map into the data entry of the response. The "media type", "HTTP method", and "uses" specifications (described in Sections 11.3.2.1, 11.3.2.2, and 11.3.2.5 of [RFC7285], respectively) remain the same. 7.1.1. Accept Input Parameters The ReqFilteredCostMap object in Section 11.3.2.3 of [RFC7285] is extended as follows: object { [PropertyName compound-properties<1..*>;] } ReqPVFilteredCostMap : ReqFilteredCostMap; compound-properties: If the capability "allow-compound-response" is false, the ALTO client MUST NOT specify this field, and the ALTO server MUST reject the request and return "E_INVALID_FILED_VALUE" error when it receives a request including this field. If this field is specified and accepted, the ALTO server MUST augment the dependent property map with the properties in this field into the response automatically. 7.1.2. Capabilities The Filtered Cost Map capabilities are extended with two new members: o dependent-property-map o allow-compound-response The capability "dependent-property-map" indicates which property map this resource depends on, and the capability "allow-compound- response" indicates whether the ALTO server supports the resource to compound the property map with its own response data. With these two additional members, the FilteredCostMapCapabilities object in Section 11.3.2.4 of [RFC7285] is extended as follows: object { [ResourceID dependent-property-map;] [JSONBool allow-compound-response;] } PVFCMCapabilities : FilteredCostMapCapabilities; Gao, et al. Expires September 12, 2019 [Page 11] Internet-Draft ALTO Extension: Path Vector March 2019 dependent-property-map: This field MUST be specified when the "cost- type-names" includes a cost type name indicating a "ane-path" metric. Its value MUST be a resource id indicating a property map including "ane" domain. If not, the ALTO client SHOULD consider this resource is invalid. allow-compound-response: If present, the true value means the ALTO client can request the resource to augment its dependent property map into the response automatically; the false value means the ALTO client cannot request the compound response. If omitted, the default value is false; To be noticed that the capability "cost-constraints" is unexpected for the "array" cost mode. The syntax and semantics of constraint tests on the "array" cost mode depends on the implementation and can be defined in the future documents. But it is not in the scope of this document. 7.1.3. Response If the ALTO client specifies the "cost-type" input parameter with "ane-path" metric, the "dependent-vtags" field in the "meta" field of the response MUST include the version tag of its dependent property map following its dependent network map. If the ALTO client specifies the "compound-properties" input parameter which is accepted by the ALTO server, the response MUST include a "property-map" field following the "cost-map" field, and its value MUST be a PropertyMapData object. This PropertyMapData object MUST be equivalent to the result when query the dependent property map resource using the following request: the "entities" field includes all the ANE names appearing in the cost values of the "cost-map" field, the "properties" field has the same value as the "compound-properties" field does. The properties shown in the "compound-properties" input parameter but are not supported by the dependent property map SHOULD be omitted from the response. 7.2. Endpoint Cost Service Extensions This document extends the Endpoint Cost Service, as defined in Section 11.5.1 of [RFC7285], by adding new input parameters and capabilities and by augmenting the property map into the data entry of the response. The media type, HTTP method, and "uses" specifications (described in Sections 11.5.1.1, 11.5.1.2, and 11.5.1.5 of [RFC7285], respectively) are unchanged. Gao, et al. Expires September 12, 2019 [Page 12] Internet-Draft ALTO Extension: Path Vector March 2019 7.2.1. Accept Input Parameters The ReqEndpointCostMap object in Section 11.5.1.3 of [RFC7285] is extended as follows: object { [PropertyName compound-properties<1..*>;] } ReqPVEndpointCostMap : ReqEndpointCostMap; The "compound-properties" has the same interpretation as defined in Section 7.1.1. 7.2.2. Capabilities The extensions to the Endpoint Cost Service capabilities are identical to the extensions to the Filtered Cost Map (see Section 7.1.2). 7.2.3. Response If the ALTO client specifies the "cost-type" input parameter with "ane-path" metric, the response MUST include the "meta" field with the "dependent-vtags" in it, and the "dependent-vtags" field MUST include the version tag of its dependent property map. If the ALTO client specifies the "compound-properties" input parameter which is accepted by the ALTO server, the response MUST include a "property-map" field following the "endpoint-cost-map" field, and its value MUST be a PropertyMapData object. This PropertyMapData object MUST be equivalent to the result when query the dependent property map resource using the following request: the "entities" field includes all the ANE names appearing in the cost values of the "endpoint-cost-map" field, the "properties" field has the same value as the "compound-properties" field does. The properties shown in the "compound-properties" input parameter but are not supported by the dependent property map SHOULD be omitted from the response. 8. Examples This section lists some examples of path vector queries and the corresponding responses. 8.1. Workflow This section gives a typical workflow of how an ALTO client query path vectors using the extension. Gao, et al. Expires September 12, 2019 [Page 13] Internet-Draft ALTO Extension: Path Vector March 2019 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 supports the "ane-path" cost metric and get the resource ID of the dependent property map. 3. Check whether the capabilities of the property map includes the desired "prop-types". 4. Check whether the (Filtered) Cost Map/Endpoint Cost Service allows the compound response. 5. If allowed, the ALTO client can send a request including the desired ANE properties to the ALTO server and receive a compound response with the cost map/endpoint cost map and the property map. 6. If not allowed, the ALTO client sends a query for the cost map/ endpoint cost map first. After receiving the response, the ALTO client interprets all the ANE names appearing in the response and sends another query for the property map on those ANE names. 8.2. 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-availbw-delay" supports properties "availbw" and "delay". { "meta": { "cost-types": { "path-vector": { "cost-mode": "array", "cost-metric": "ane-path" }, "num-routingcost": { "cost-mode": "numerical", "cost-metric": "routingcost" }, "num-hopcount": { "cost-mode": "numerical", "cost-metric": "hopcount" } } }, Gao, et al. Expires September 12, 2019 [Page 14] Internet-Draft ALTO Extension: Path Vector March 2019 "resources": { "my-default-networkmap": { "uri" : "http://alto.example.com/networkmap", "media-type" : "application/alto-networkmap+json" }, "my-default-cost-map": { "uri": "http://alto.example.com/costmap/pv", "media-type": "application/alto-costmap+json", "accepts": "application/alto-costmapfilter+json", "capabilities": { "cost-type-names": [ "num-hopcount", "num-routingcost" ] }, "uses": [ "my-default-networkmap" ] }, "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": [ "path-vector" ], "dependent-property-map": "propmap-availbw-delay" }, "uses": [ "my-default-networkmap" ] }, "endpoint-cost-pv": { "uri": "http://alto.exmaple.com/endpointcost/pv", "media-type": "application/alto-endpointcost+json", "accepts": "application/alto-endpointcostparams+json", "capabilities": { "cost-type-names": [ "path-vector" ], "dependent-property-map": "propmap-availbw-delay", "allow-compound-response": true } }, "invalid-cost-map" : { "uri": "http://alto.example.com/costmap/invalid", "media-type": "application/alto-costmap+json", "accepts": "application/alto-costmapfilter+json", "capabilities": { "cost-type-names": [ "path-vector" ], "allow-compound-response": true }, "uses": [ "my-default-networkmap" ] }, "propmap-availbw-delay": { "uri": "http://alto.exmaple.com/propmap/ane-prop", "media-type": "application/alto-propmap+json", Gao, et al. Expires September 12, 2019 [Page 15] Internet-Draft ALTO Extension: Path Vector March 2019 "accepts": "application/alto-propmapparams+json", "capabilities": { "domain-types": [ "ane" ], "prop-types": [ "availbw", "delay" ] }, "uses": [ "cost-map-pv", "endpoint-cost-pv" ] } } } 8.3. Example # 1 Query filtered cost map to get the path vectors. POST /costmap/pv HTTP/1.1 Host: alto.example.com Accept: application/alto-costmap+json, application/alto-error+json Content-Length: [TBD] Content-Type: application/alto-costmapfilter+json { "cost-type": { "cost-mode": "array", "cost-metric": "ane-path" }, "pids": { "srcs": [ "PID1" ], "dsts": [ "PID2", "PID3" ] } } Gao, et al. Expires September 12, 2019 [Page 16] Internet-Draft ALTO Extension: Path Vector March 2019 HTTP/1.1 200 OK Content-Length: [TBD] Content-Type: application/alto-costmap+json { "meta": { "dependent-vtags": [ { "resource-id": "my-default-networkmap", "tag": "75ed013b3cb58f896e839582504f622838ce670f" } ], "cost-type": { "cost-mode": "array", "cost-metric": "ane-path" } }, "cost-map": { "PID1": { "PID2": [ "ane:L001", "ane:L003" ], "PID3": [ "ane:L001", "ane:L004" ] } } } Then query the properties of ANEs in path vectors. POST /propmap/ane-prop 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 { "entities": [ "ane:L001", "ane:L003", "ane:L004" ], "properties": [ "delay" ] } Gao, et al. Expires September 12, 2019 [Page 17] Internet-Draft ALTO Extension: Path Vector March 2019 HTTP/1.1 200 OK Content-Length: [TBD] Content-Type: application/alto-propmap+json { "meta": { "dependent-vtags": [ { "resource-id": "cost-map-pv", "tag": "a7d57e120ab63124e3c9a82f7a54bc120fc96216" } ] }, "property-map": { "ane:L001": { "delay": 46}, "ane:L003": { "delay": 50}, "ane:L004": { "delay": 70} } } 8.4. Example # 2 POST /endpointcost/pv HTTP/1.1 Host: alto.example.com Accept: application/alto-endpointcost+json, application/alto-error+json Content-Length: [TBD] Content-Type: application/alto-endpointcostparams+json { "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" ] } } Gao, et al. Expires September 12, 2019 [Page 18] Internet-Draft ALTO Extension: Path Vector March 2019 HTTP/1.1 200 OK Content-Length: [TBD] Content-Type: application/alto-endpointcost+json { "meta": { "cost-type": [ {"cost-mode": "array", "cost-metric": "ane-path"} ] }, "endpoint-cost-map": { "ipv4:192.0.2.2": { "ipv4:192.0.2.89": [ "ane:L001", "ane:L003", "ane:L004" ], "ipv4:203.0.113.45": [ "ane:L001", "ane:L004", "ane:L005" ], "ipv6:2001:db8::10": [ "ane:L001", "ane:L005", "ane:L007" ] } } } POST /endpointcost/pv HTTP/1.1 Host: alto.example.com Accept: application/alto-endpointcost+json, application/alto-error+json Content-Length: [TBD] Content-Type: application/alto-endpointcostparams+json { "entities": [ "ane:L001", "ane:L003", "ane:L004", "ane:L005", "ane:L007" ], "properties": [ "availbw" ] } Gao, et al. Expires September 12, 2019 [Page 19] Internet-Draft ALTO Extension: Path Vector March 2019 HTTP/1.1 200 OK Content-Length: [TBD] Content-Type: application/alto-propmap+json { "meta": { "dependent-vtags": [ { "resource-id": "endpoint-cost-pv", "tag": "12c0889c3c0892bb67df561ed16d93f5d1fa75cf" } ] }, "property-map": { "ane:L001": { "availbw": 50 }, "ane:L003": { "availbw": 48 }, "ane:L004": { "availbw": 55 }, "ane:L005": { "availbw": 60 }, "ane:L007": { "availbw": 35 } } } 8.5. Example #3 Gao, et al. Expires September 12, 2019 [Page 20] Internet-Draft ALTO Extension: Path Vector March 2019 POST /endpointcost/pv HTTP/1.1 Host: alto.example.com Accept: application/alto-endpointcost+json, application/alto-error+json Content-Length: [TBD] Content-Type: application/alto-endpointcostparams+json { "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" ] }, "properties": [ "delay", "availbw" ] } Gao, et al. Expires September 12, 2019 [Page 21] Internet-Draft ALTO Extension: Path Vector March 2019 HTTP/1.1 200 OK Content-Length: [TBD] Content-Type: application/alto-endpointcost+json { "meta": { "dependent-vtags": [ { "resource-id": "propmap-availbw-delay", "tag": "bb6bb72eafe8f9bdc4f335c7ed3b10822a391cef" } ], "cost-type": [ {"cost-mode": "array", "cost-metric": "ane-path"} ] }, "endpoint-cost-map": { "ipv4:192.0.2.2": { "ipv4:192.0.2.89": [ "ane:L001", "ane:L003", "ane:L004" ], "ipv4:203.0.113.45": [ "ane:L001", "ane:L004", "ane:L005" ], "ipv6:2001:db8::10": [ "ane:L001", "ane:L005", "ane:L007" ] } }, "property-map": { "ane:L001": { "availbw": 50, "delay": 46 }, "ane:L003": { "availbw": 48, "delay": 50 }, "ane:L004": { "availbw": 55, "delay": 70 }, "ane:L005": { "availbw": 60, "delay": 100 }, "ane:L007": { "availbw": 35, "delay": 100 } } } 9. Compatibility 9.1. Compatibility with Base ALTO Clients/Servers The path vector extension on Filtered Cost Map and Endpoint Cost Service is backward compatible with the base ALTO protocol: o If the ALTO server provides extended capabilities "dependent- property-map" and "allow-compound-response" for Filtered Cost Map or Endpoint Cost Service, but the client only supports the base ALTO protocol, then the client will ignore those capabilities without conducting any incompatibility. Gao, et al. Expires September 12, 2019 [Page 22] Internet-Draft ALTO Extension: Path Vector March 2019 o If the client sends a request with the input parameter "properties", but the server only supports the base ALTO protocol, the server will ignore this field. 9.2. Compatibility with Multi-Cost Extension This document does not specify how to integrate the "array" cost mode and the "ane-path" cost metric 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. As Section 7.1.2 mentions, the syntax and semantics of whether "constraints" or "or-constraints" field for the "array" cost mode is not specified in this document. So if an ALTO server provides a resource with the "array" cost mode and the capability "cost- constraints" or "testable-cost-types-names", the ALTO client MAY ignore the capability "cost-constraints" or "testable-cost-types- names" unless the implementation or future documents specify the behavior. 9.3. 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. 10. General Discussions 10.1. 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 Gao, et al. Expires September 12, 2019 [Page 23] Internet-Draft ALTO Extension: Path Vector March 2019 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. 10.2. 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. 10.3. General Compound Resources Query As the last paragraph of Section 4.3 mentions, querying multiple ALTO information resources continuously is 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. 11. Security Considerations This document is an extension of the base ALTO protocol, so the Security Considerations 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]). Gao, et al. Expires September 12, 2019 [Page 24] Internet-Draft ALTO Extension: Path Vector March 2019 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. 12. IANA Considerations 12.1. 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. Gao, et al. Expires September 12, 2019 [Page 25] Internet-Draft ALTO Extension: Path Vector March 2019 12.2. ALTO Cost Metric Registry A new cost metric needs to be registered in the "ALTO Cost Metric Registry", listed in Table 2. +-------------+---------------------+ | Identifier | Intended Semantics | +-------------+---------------------+ | ane-path | See Section 5.2 | +-------------+---------------------+ Table 2: ALTO Cost Metrics 12.3. 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 3. +-------------+--------------------------+--------------------------+ | Identifier | Entity Address Encoding | Hierarchy & Inheritance | +-------------+--------------------------+--------------------------+ | ane | See Section 6.2 | None | +-------------+--------------------------+--------------------------+ Table 3: ALTO Entity Domain 12.4. ALTO Network Element Property Type Registry The "ALTO Abstract Network Element Property Type Registry" is required by the ALTO 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 13. 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 Bernstein (Grotto Networks), Dawn Chen (Tongji University), Wendy Roome, and Michael Scharf for their contributions to earlier drafts. Gao, et al. Expires September 12, 2019 [Page 26] Internet-Draft ALTO Extension: Path Vector March 2019 14. References 14.1. 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, . 14.2. Informative References [I-D.bernstein-alto-topo] Bernstein, G., Yang, Y., and Y. Lee, "ALTO Topology Service: Uses Cases, Requirements, and Framework", draft- bernstein-alto-topo-00 (work in progress), October 2013. [I-D.ietf-alto-cost-calendar] Randriamasy, S., Yang, Y., Wu, Q., Lingli, D., and N. Schwan, "ALTO Cost Calendar", draft-ietf-alto-cost- calendar-01 (work in progress), February 2017. [I-D.ietf-alto-incr-update-sse] Roome, W., Yang, Y., and S. Chen, "ALTO Incremental Updates Using Server-Sent Events (SSE)", draft-ietf-alto- incr-update-sse-15 (work in progress), December 2018. [I-D.ietf-alto-unified-props-new] Roome, W., Chen, S., xinwang2014@hotmail.com, x., Yang, Y., and J. Zhang, "Extensible Property Maps for the ALTO Protocol", draft-ietf-alto-unified-props-new-01 (work in progress), December 2017. [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, . Authors' Addresses Gao, et al. Expires September 12, 2019 [Page 27] Internet-Draft ALTO Extension: Path Vector March 2019 Kai Gao Tsinghua University Beijing Beijing China Email: gaok12@mails.tsinghua.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. 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