ALTO WG K. Gao Internet-Draft Tsinghua University Intended status: Standards Track J. Zhang Expires: December 27, 2017 J. Wang Tongji University Q. Xiang Tongji/Yale University Y. Yang Yale University June 25, 2017 ALTO Extension: Flow-based Cost Query draft-gao-alto-fcs-02.txt Abstract The emergence of new networking datapath capabilities has substantially increased the flexibility of networking. For example, OpenFlow has emerged as a major southbound protocol for Software- Defined Networking, and OpenFlow allows flexible routing beyond simple destination-based routing. In this document, we define a new extention to ALTO, namely the Flow Cost Service, for ALTO clients in an OpenFlow-enabled network to query ALTO network information. 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 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 December 27, 2017. Gao, et al. Expires December 27, 2017 [Page 1] Internet-Draft Flow Cost Service June 2017 Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Changes Since Version -01 . . . . . . . . . . . . . . . . . . 4 3. ALTO Flow Cost Specification: Basic Flow-based Query . . . . 4 3.1. Flow-based Filtered Cost Map . . . . . . . . . . . . . . 4 3.1.1. Capabilities . . . . . . . . . . . . . . . . . . . . 4 3.1.2. Accept Input Parameters . . . . . . . . . . . . . . . 5 3.1.3. Response . . . . . . . . . . . . . . . . . . . . . . 6 3.2. Extend Endpoint Encoding . . . . . . . . . . . . . . . . 6 3.2.1. Protocol . . . . . . . . . . . . . . . . . . . . . . 6 3.2.2. EndpointName . . . . . . . . . . . . . . . . . . . . 6 3.2.3. Port . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2.4. EndpointURI Example . . . . . . . . . . . . . . . . . 7 3.3. Flow-based Endpoint Cost Service . . . . . . . . . . . . 7 3.3.1. Capabilities . . . . . . . . . . . . . . . . . . . . 7 3.3.2. Accept Input Parameters . . . . . . . . . . . . . . . 8 3.3.3. Response . . . . . . . . . . . . . . . . . . . . . . 8 3.4. Example . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.4.1. IRD Example . . . . . . . . . . . . . . . . . . . . . 9 3.4.2. Flow-based Filtered Cost Map Service Example . . . . 10 3.4.3. Flow-based Endpoint Cost Service Example . . . . . . 11 4. ALTO Flow Cost Specification: Advanced Flow-based Query . . . 12 4.1. Basic Data Types . . . . . . . . . . . . . . . . . . . . 12 4.1.1. Flow ID . . . . . . . . . . . . . . . . . . . . . . . 12 4.1.2. Typed Header Field . . . . . . . . . . . . . . . . . 12 4.1.3. Cost Confidence . . . . . . . . . . . . . . . . . . . 12 4.2. Flow Cost Service . . . . . . . . . . . . . . . . . . . . 13 4.2.1. Media Type . . . . . . . . . . . . . . . . . . . . . 13 4.2.2. HTTP Method . . . . . . . . . . . . . . . . . . . . . 13 4.2.3. Accept Input Parameters . . . . . . . . . . . . . . . 13 4.2.4. Capabilities . . . . . . . . . . . . . . . . . . . . 14 4.2.5. Response . . . . . . . . . . . . . . . . . . . . . . 15 Gao, et al. Expires December 27, 2017 [Page 2] Internet-Draft Flow Cost Service June 2017 4.2.6. Errors . . . . . . . . . . . . . . . . . . . . . . . 16 4.3. Advanced Flow-based Query Example . . . . . . . . . . . . 17 5. Security Considerations . . . . . . . . . . . . . . . . . . . 19 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 6.1. Media Types . . . . . . . . . . . . . . . . . . . . . . . 19 6.2. Header Field . . . . . . . . . . . . . . . . . . . . . . 20 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 20 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 8.1. Normative References . . . . . . . . . . . . . . . . . . 21 8.2. Informative References . . . . . . . . . . . . . . . . . 21 Appendix A. Tables . . . . . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 1. Introduction ALTO is now being considered as a solution for more flexible network scenario. The legacy ALTO services defined in [RFC7285] only provide the cost information for peer selection. It is enough for the P2P application. However, the network is becoming more and more flexible nowadays. There are two major changes in the coming network evolution: o Some new network architectures, such as Software Defined Networking (SDN), are adopting the logically central control solution, which makes the network optimization toward the higher- level view. The traffic optimizer can not only decide the source or the destination of the data transferring, but also make the flow-level traffic scheduling. To solve the flow-level scheduling problem, the cross-product query schema will be redundant. o With the emerging technologies in the data plane, where multiple header fields can be used to determine the forwarding path, networks are moving to more flexible routing mechanisms beyond the simple destination-based routing. As a consequence, the endpoint cost service (ECS), which depends on only source and destination IP addresses as currently defined, is no longer sufficient to provide accurate cost information. This document addresses the following issues in providing fine- grained flow-based endpoint cost query services: 1) The compatibility with the legacy ALTO ECS service; 2) The support for emerging network architectures such as Software Defined Networking; 3) The trade-off between fine-grained queries and query/response redundancy. In this document, we consider the extensions of ALTO service which provide the flow-based cost query. The basic solution is to extend the legacy ALTO services to support flow-based query schema. Section 3 describes the extended schema on Filtered Cost Map (FCM) Gao, et al. Expires December 27, 2017 [Page 3] Internet-Draft Flow Cost Service June 2017 and Endpoint Cost Service (ECS) to support endpoint cost queries of flows defined by the 5-tuple of protocol, src/dst name/address and ports. For networks using a more generic flow concept such as Software-Defined Networks, Section 4 defines a novel ALTO service named the Flow Cost Service (FCS) with the flow-oriented query schema. It SHOULD support the query of any fine-grained routing cost to satisfy the growing demand of obtaining accurate costs in a network using flow-based routing. Section 5 and Section 6 discuss security and IANA considerations. 2. Changes Since Version -01 Note to Editor: Please remove this section prior to publication. This section records the change log of the draft updates. o Change the schema of "pid-flows" and "endpoint-flows" fields from pair list to pair mesh list. Changes since older versions: o Define the basic flow-based query extensions for Filtered Cost Map and Endpoint Cost service. The basic flow-based query is downward compatible with the legacy ALTO service. It does not introduce any new media types. o Move the service of media-type "application/alto-flowcost+json" to the advanced flow-based query extension. It will ask ALTO server to support the new media type. 3. ALTO Flow Cost Specification: Basic Flow-based Query This section describes a downward compatible extension for Filtered Cost Map and Endpoint Cost Service to support flow-based query. 3.1. Flow-based Filtered Cost Map 3.1.1. Capabilities The Filtered Cost Map capabilities are extended with a new member: flow-based-filter. The capability "flow-based-filter" indicates whether this resource supports flow-based query. The FilteredCostMapCapabilities object in Section 4.1.1 of [I-D.ietf-alto-multi-cost] is extended as follows: Gao, et al. Expires December 27, 2017 [Page 4] Internet-Draft Flow Cost Service June 2017 object { JSONString cost-type-names<1..*>; [JSONBool cost-constraints;] [JSONNumber max-cost-types;] [JSONString testable-cost-type-names<1..*>;] [JSONBool flow-based-filter;] } FilteredCostMapCapabilities; cost-type-names and cost-constraints: As defined in Section 11.3.2.4 of [RFC7285]. max-cost-types and testable-cost-type-names: As defined in Section 4.1.1 of [I-D.ietf-alto-multi-cost]. flow-based-filter: If true, then the ALTO Server allows pid-flows to be queried in the requests. If not present, this field MUST be interpreted as if it is specified false. 3.1.2. Accept Input Parameters The ReqFilteredCostMap object in Section 4.1.2 of [I-D.ietf-alto-multi-cost] is extended as follows: object { [CostType cost-type;] [CostType multi-cost-types<1..*>;] [CostType testable-cost-types<1..*>;] [JSONString constraints<0..*>;] [JSONString or-constraints<0..*><0..*>;] [PIDFilter pids;] [PIDFilter pid-flows<1..*>;] } ReqFilteredCostMap; cost-type, multi-cost-types, testable-cost-types, constraints, or- constraints: As defined in Section 4.1.2 of [I-D.ietf-alto-multi-cost]. pids: As defined in Section 11.3.2.3 of [RFC7285]. pid-flows: Defined as a list of PIDFilter objects in which each object is as defined in Section 11.3.2.3 of [RFC7285]. The ALTO server MUST interpret PID pairs appearing in all objects multiple times as if they appeared only once. If the "pids" field is present, the "pid-flows" field MUST NOT be specified. Gao, et al. Expires December 27, 2017 [Page 5] Internet-Draft Flow Cost Service June 2017 3.1.3. Response The response is exactly as defined in Section 4.1.3 of [I-D.ietf-alto-multi-cost]. 3.2. Extend Endpoint Encoding The legacy endpoint encoding is TypedEndpointAddr, which is defined in Section 10.4 of [RFC7285]. This encoding only defines two address types: ipv4 and ipv6 to express IPv4 addresses and IPv6 addresses respectively. However, the flow-extended ECS may contain MAC addresses, domain names and port numbers to give a cost between hosts. Therefore, this document extends the endpoint encoding from TypedEndpointAddr to EndpointURI to measure the cost more precisely. The syntax of EndpointURI SHOULD be compatible with the definition of URI in [RFC3986]. The string encoded as type EndpointURI MUST be one of the following format: Protocol:EndpointName Protocol:EndpointName:Port This definition is downward compatible with the definition of TypedEndpointAddr . When the Protocol field only supports "ipv4" and "ipv6", EndpointURI is equivalent to TypedEndpointAddr. 3.2.1. Protocol The Protocol field is REQUIRED. The available values contain different protocols including layer two protocols (e.g. "eth") and layer three protocols (e.g. "ipv4", "ipv6"). It can also be specified upper-layer protocols (e.g. "udp", "tcp", "ssh", "http" and "ftp"). The source and destination protocols MUST NOT be conflict. In every EndpointFilter object of either "endpoints" field or "endpoint-flows" field, if the source protocol is conflict with the destination protocol, this endpoint pair is invalid. For different protocols, some additional constraints are defined in Section 3.2.3. 3.2.2. EndpointName The EndpointName field is REQUIRED. The value can be a MAC address, an IP address or a host/domain name. If the IP address type is "ipv6" and the Port field is specified, the address MUST be enclosed in "[" and "]" characters, as recommended in [RFC2732]. Gao, et al. Expires December 27, 2017 [Page 6] Internet-Draft Flow Cost Service June 2017 3.2.3. Port The Port field is OPTIONAL. It is introduced for more fine-gained requests when the protocol is upper-layer. It MUST be forbidden when the Protocol field is specified layer three (like "ipv4" and "ipv6") or layer two protocol (like "eth"). For some classic application- layer protocols, if the port is not specified, the ALTO server will use the default port. For example, the default port of "ssh" is 22, "ftp" is 21 and "http" is 80. 3.2.4. EndpointURI Example Some valid EndpointURI values look like follows: "eth:98:e0:d9:9c:df:81" "http:www.example.com" "ipv4:198.51.100.34" "telnet:198.51.100.34:23" "tcp:[2000::1:2345:6789:abcd]:8080" 3.3. Flow-based Endpoint Cost Service 3.3.1. Capabilities The extensions of EndpointCostCapabilities are based on FilteredCostMapCapabilities in Section 3.1.1 but with a new member: protocols. The capability "protocols" indicates which protocols are supported to be queried by this resource. For the capability "flow-based-filter", the true value means the ALTO server allows requests to have "endpoint-flows" field. If not present, this field MUST be interpreted as if it is specified false. object { [JSONString protocols<0..*>;] [JSONBool flow-based-filter;] } EndpointCostCapabilities : FilteredCostMapCapabilities; protocols: Defines a list of JSONString indicating the supported Protocol values of the EndpointURI in the request. The ALTO server does not have to claim "ipv4" and "ipv6" in this field explictly, because they are supported by default. If not present, this field MUST be interpreted as if it is specified the default supported protocols "ipv4" and "ipv6". Gao, et al. Expires December 27, 2017 [Page 7] Internet-Draft Flow Cost Service June 2017 flow-based-filter: If true, then the ALTO Server allows endpoint- flows to be queried in the requests. If not present, this field MUST be interpreted as if it is specified false. 3.3.2. Accept Input Parameters The ReqEndpointCostMap object in Section 4.2.2 of [I-D.ietf-alto-multi-cost] is extended as follows: object { [CostType cost-type;] [CostType multi-cost-types<1..*>;] [CostType testable-cost-types<1..*>;] [JSONString constraints<0..*>;] [JSONString or-constraints<0..*><0..*>;] [EndpointFilter endpoints;] [EndpointFilter endpoint-flows<1..*>;] } ReqEndpointCostMap; object { EndpointURI srcs<0..*>; EndpointURI dsts<0..*>; } EndpointFilter; cost-type, multi-cost-types, testable-cost-types, constraints, or- constraints: As defined in Section 4.1.2 of [I-D.ietf-alto-multi-cost]. endpoints: As defined in Section 11.5.1.3 of [RFC7285]. endpoint-flows: Defined as a list of EndpointFilter objects in which each object is as defined in Section 11.5.1.3 of [RFC7285]. The ALTO server MUST interpret endpoint pairs appearing multiple times in all EndpointFilter objects as if they appeared only once. The additional requirement is that the ALTO client MUST specify either "endpoints" or "endpoint-flows", but MUST NOT specify both. 3.3.3. Response The response is exactly as defined in Section 4.2.3 of [I-D.ietf-alto-multi-cost]. 3.4. Example Gao, et al. Expires December 27, 2017 [Page 8] Internet-Draft Flow Cost Service June 2017 3.4.1. IRD Example GET /directory HTTP/1.1 Host: alto.example.com Accept: application/alto-directory+json,application/alto-error+json HTTP/1.1 200 OK Content-Length: [TODO] Content-Type: application/alto-directory+json { "meta" : { "default-alto-network-map" : "my-default-network-map", "cost-types" : { "num-routingcost" : { "cost-mode" : "numerial", "cost-metric" : "routingcost"}, "ord-routingcost" : { "cost-mode" : "ordinal", "cost-metric" : "routingcost"} }, ..... Other ALTO cost types as described in RFC7285 ..... }, "resources" : { "my-default-network-map" : { "uri" : "http://alto.example.com/networkmap", "media-type" : "application/alto-networkmap+json" }, "basic-flow-based-cost-map" : { "uri" : "http://alto.example.com/costmap/multi/filtered", "media-types" : [ "application/alto-costmap+json" ], "accepts" : [ "application/alto-costmapfilter+json" ], "uses" : [ "my-default-network-map" ], "capabilities" : { "flow-based-filter" : true, "cost-type-names" : [ "ord-routingcost" , "num-routingcost" ] } }, "basic-flow-based-endpoint-cost" : { "uri" : "http://alto.example.com/endpointcost/lookup", "media-types" : [ "application/alto-endpointcost+json" ], "accepts" : [ "application/alto-endpointcostparams+json" ], "uses" : [ "my-default-network-map" ], "capabilities" : { "protocols": ["tcp", "http"], "flow-based-filter" : true, "cost-type-names" : [ "ord-routingcost" , "num-routingcost" ] Gao, et al. Expires December 27, 2017 [Page 9] Internet-Draft Flow Cost Service June 2017 } } } } 3.4.2. Flow-based Filtered Cost Map Service Example POST /costmap/multi/filtered HTTP/1.1 Host: alto.example.com Accept: application/alto-costmap+json,application/alto-error+json Content-Length: [TBD] Content-Type: application/alto-costmapfilter+json { "cost-type": { "cost-mode": "numerical", "cost-metric": "routingcost" }, "pid-flows": [ { "srcs": ["PID1"], "dsts": ["PID2", "PID3"] }, { "srcs": ["PID3"], "dsts": ["PID4"] } ] } HTTP/1.1 200 OK Content-Length: [TBD] Content-Type: application/alto-costmap+json { "meta": { "dependent-vtags": [ { "resource-id": "my-default-network-map", "tag": "75ed013b3cb58f896e839582504f622838ce670f" }, ], "cost-type": { "cost-mode": "numerical", "cost-metric": "routingcost" } }, "cost-map": { "PID1": { "PID2": 100 }, "PID1": { "PID3": 20 }, "PID3": { "PID4": 80 } } } Gao, et al. Expires December 27, 2017 [Page 10] Internet-Draft Flow Cost Service June 2017 3.4.3. Flow-based Endpoint Cost Service Example POST /endpointcost/lookup HTTP/1.1 Host: alto.example.com Accept: application/alto-endpointcost+json,application/alto-error+json Content-Length: [TBD] Content-Type: application/alto-endpointcostparams+json { "cost-type": { "cost-mode": "numerical", "cost-metric": "hopcount" }, "endpoint-flows": [ { "srcs": ["ipv4:192.0.2.2"], "dsts": ["ipv4:192.0.2.89", "http:cdn1.example.com"] }, { "srcs": ["tcp:203.0.113.45:54321"], "dsts": ["http:cdn1.example.com"] } ] } HTTP/1.1 200 OK Content-Length: [TBD] Content-Type: application/alto-endpointcost+json { "meta": { "cost-type": { "cost-mode": "numerical", "cost-metric": "hopcount" } }, "endpoint-cost-map": { "ipv4:192.0.2.2": { "ipv4:192.0.2.89": 3, "http:cdn1.example.com": 6 }, "tcp:203.0.113.45:54321": { "http:cdn1.example.com": 10 } } } Gao, et al. Expires December 27, 2017 [Page 11] Internet-Draft Flow Cost Service June 2017 4. ALTO Flow Cost Specification: Advanced Flow-based Query The basic flow-based query extends the ECS service to support querying the cost of flows. However, it only supports the cost query of flows defined by the 5-tuple of protocol, source/destination address (hostname, IP address, domain name or MAC address) and ports. However, in the emerging software-defined networking, the concept of flow is not confined by this 5-tuple anymore. Instead, [OF15] has defined 38 header match fields that could define a flow. This document next introduces an advanced flow-based query to support the flow-based cost queries for such a generic context of flows. 4.1. Basic Data Types The flow cost service introduces some new basic data types, as defined below. 4.1.1. Flow ID A flow ID has the same format as a PIDName, as defined in Section 10.1 of [RFC7285]. It is used to uniquely identify a flow in a flow cost service request. 4.1.2. Typed Header Field A typed header field represents a particular field in a network protocol that can be obtained at the application layer. It is represented by the protocol name and the field name, concatenated by the colon (':', U+003A). The typed header fields are case insensitive. For example, "ipv4:source" and "IPv4:source" both represent the source address field used in IPv4 and "tcp:destination" represents the destination port for a TCP connection. See Table 2 for a list of proposed typed header fields. 4.1.3. Cost Confidence A cost confidence is defined as a JSON integer within the range of [0, 100]. It represents the ALTO servers' estimation on the accuracy of the returned costs. The larger the cost confidence is, the more accurate the path cost SHOULD be. If the cost value is very accurate, for example, a unique path can be identified for a flow with the provided information, the ALTO server SHOULD provide a cost confidence of 100. Gao, et al. Expires December 27, 2017 [Page 12] Internet-Draft Flow Cost Service June 2017 The cost confidence CAN be used as an evidence of ambiguous paths, which is often associated with insufficient information in a query. If an ALTO client finds that the associated cost confidence value is low, it can narrow down the flow header space in the query, e.g., by adding optional fields or use IP addresses instead of prefixes. The cost confidence value can be computed in several ways. For example, an ALTO server MAY use the following formula for some cost metrics: c = 100 * (1 - |deviation / mean|) 0 if c <= 0 confidence = round(c) if c > 0 where mean and deviation are computed from the cost values of all possible paths. 4.2. Flow Cost Service A flow cost service provides information about costs for each individual flow specified in a request. 4.2.1. Media Type The media type of the flow cost service is "application/alto- flowcost+json". 4.2.2. HTTP Method The flow cost service is requested using the HTTP POST method. 4.2.3. Accept Input Parameters The input parameters of the flow cost service MUST be encoded as a JSON object of type FlowCostRequest in the body of an HTTP POST request. The media type of the request MUST be "application/alto- flowcostparams+json". object { FlowFilterMap flows; } FlowCostRequest : MultiCostRequestBase; Gao, et al. Expires December 27, 2017 [Page 13] Internet-Draft Flow Cost Service June 2017 object { [CostType cost-type;] [CostType multi-cost-types<1..*>;] [CostType testable-cost-types<1..*>;] [JSONString constraints<0..*>;] [JSONString or-constraints<0..*><0..*>;] } MultiCostRequestBase; object-map { FlowId -> FlowFilter; } FlowFilterMap; object-map { TypedHeaderField -> JSONValue; } FlowFilter; flows: A map of flow filters for which path costs are to be returned. Each flow filter is identified by a unique FlowId, as defined in Section 4.1.1. The value types of a field is protocol- specific, see Table 3 for the value types associated with typed header fields in Table 2. cost-type: The same as defined in Section 4.2.2 of [I-D.ietf-alto-multi-cost]. multi-cost-types: The same as defined in Section 4.2.2 of [I-D.ietf-alto-multi-cost]. testable-cost-types, constraints, or-constraints: The same as defined in Section 4.2.2 of [I-D.ietf-alto-multi-cost]. 4.2.4. Capabilities The capabilities of the flow cost service is a JSON object of type FlowCostCapabilities: object { TypedHeaderField required<1..*>; [TypedHeaderField optional<1..*>;] } FlowCostCapabilities : FilteredCostMapCapabilities; with fields: required: A list of required typed header fields. These fields are essential to find the path cost for a given flow and MUST be provided in a flow filter. Gao, et al. Expires December 27, 2017 [Page 14] Internet-Draft Flow Cost Service June 2017 optional: A list of optional typed header fields. The ALTO server MAY leverage the values of the optional fields to find more accurate costs. 4.2.5. Response The "meta" field of a flow cost response MUST contain the same cost type information as defined in Section 4.2.3 of [I-D.ietf-alto-multi-cost]. The data component of a flow cost service is named "flow-cost-map", which is a JSON object of type FlowCostMap: object { FlowCostMap flow-cost-map; [FlowCostMap flow-cost-confidences;] } FlowCostResponse : ResponseEntityBase; object-map { FlowId -> JSONValue; } FlowCostMap; flow-cost-map: A dictionary map with each key (flow ID) representing a flow specified in the request. For each flow, the cost MUST follow the format defined in Section 4.2.3 of [I-D.ietf-alto-multi-cost]. flow-cost-confidences: A dictionary map with each key (flow ID) representing a flow specified in the request. For a single cost, the cost confidence for each flow MUST follow the specification in Section 4.1.3. If the query is using multiple costs where the costs are returned as a JSONArray, the cost confidence MUST also be a JSONArray where each element represents the cost confidence value computed for the corresponding cost type. 4.2.5.1. Ambiguous Paths Since new forwarding abstractions support fine-grained routing, for example, OpenFlow 1.5 [OF15] has defined 38 header match fields, it is possible that the ALTO server cannot determine the path using the provided header fields. The computation for costs with ambiguous paths is implementation-specific, the servers can choose to return an integrated result of all possible paths, or simply use the cost of a random path. The ALTO servers SHOULD provide cost confidences to justify the accuracy of the provided cost values. Gao, et al. Expires December 27, 2017 [Page 15] Internet-Draft Flow Cost Service June 2017 The ALTO server SHOULD be able to determine a unique path when all the optional typed header fields are provided without masks for a flow, however, the client SHOULD NOT assume this always holds. 4.2.6. Errors The ALTO servers can provide more information to the clients when requests have errors. The FlowCostErrorMap below can provide basic information about two most common errors for the flow cost service. The ALTO servers MAY include it as the data component of an ALTO error response. If multiple errors are identified, the ALTO server MUST return exactly one error code according to Section 8.5.2 of [RFC7285] . object-map { FlowId -> FlowCostError; } FlowCostErrorMap; object { [TypedHeaderField conflicts<2..*>;] [TypedHeadreField missing<2..*>;] [TypedHeaderField unsupported<1..*>;] } FlowFilterError; conflicts: A list of conflicting typed header fields. See Section 4.2.6.1 for details. missing: A list of missing typed header fields. See Section 4.2.6.2 for details. unsupported: A list of unsupported typed header fields. See Section 4.2.6.3 for details. 4.2.6.1. Conflicts Some header fields may have conflicts. For example, IPv4 fields and IPv6 fields can never appear in the same packet, nor can TCP and UDP ports. These header fields MUST not be included in the same flow filter, otherwise the ALTO server MUST return an ALTO error response, with the error code "E_INVALID_FIELD_VALUE". As specified in Section 8.5.2 of [RFC7285], the ALTO server MAY include the "field" and the "value" in the "meta" field. In this case, the ALTO server MUST use the flow ID as the "field" and the flow filter as the "value". However, the recommended approach is to use the FlowCostErrorMap, where the server CAN provide the conflicting typed header fields in the "conflicts" field of the FlowFilterError associated with the corresponding flow ID. Gao, et al. Expires December 27, 2017 [Page 16] Internet-Draft Flow Cost Service June 2017 4.2.6.2. Missing Fields The "E_MISSING_FIELD" error code is originally designed to report the absence of required JSON fields. In the flow cost service, the required typed header fields are implementation-specific and the ALTO servers MUST declare the required fields in the capabilities. If any required header field is missing, the ALTO server MUST return an ALTO error response, with the error code "E_MISSING_FIELD". The ALTO server CAN follow the steps defined in Section 8.5.2 of [RFC7285] to indicate the location of the missing field. An alternative approach which is also recommended, is that the server provide the missing typed header fields in the "missing" field of the FlowFilterError associated with the corresponding flow ID. 4.2.6.3. Unsupported Fields If a query contains unsupported typed header fields, e.g., those not in the "required" nor the "optional" capabilities, the ALTO server MUST return an ALTO error response, with the error code "E_INVALID_FIELD_VALUE". Like how the conflicting header fields are handled in Section 4.2.6.1, the ALTO servers CAN report unsupported typed header fields in the "unsupported" field associated with the corresponding flow ID. 4.3. Advanced Flow-based Query Example Gao, et al. Expires December 27, 2017 [Page 17] Internet-Draft Flow Cost Service June 2017 POST /flowcost/lookup HTTP/1.1 HOST: alto.example.com Content-Length: 521 Content-Type: application/alto-flowcostparams+json Accept: application/alto-flowcost+json,application/alto-error+json { "cost-type": { "cost-mode": "numerical", "cost-metric": "routingcost" }, "flows": { "l3-flow": { "ipv4:source": "192.168.1.1", "ipv4:destination": "192.168.1.2" }, "optional-l2-flow": { "ethernet:source": "12:34:56:78:00:01", "ethernet:destination": "12:34:56:78:00:02" }, "l3-flow-aggr": { "ipv4:source": "192.168.1.0/24", "ipv4:destination": "192.168.2.0/24" } } } Gao, et al. Expires December 27, 2017 [Page 18] Internet-Draft Flow Cost Service June 2017 HTTP/1.1 200 OK Content-Length: 312 Content-Type: application/alto-flowcost+json { "meta": { "cost-type": { "cost-mode": "numerical", "cost-metric": "routingcost" }, }, "flow-cost-map": { "l3-flow": 10, "l3-flow-aggr": 50 "optional-l3-flow": 5, }, "flow-cost-confidences": { "l3-flow": 70, "l3-flow-aggr": 40, "optional-l2-flow": 90 } } 5. Security Considerations This document has not conducted its security analysis. 6. IANA Considerations This document defines two new entries to be registered to application/alto-* media types. 6.1. Media Types This document registers two media types listed in Table 1. +--------------+--------------------------+----------------+ | Type | Subtype | Specification | +--------------+--------------------------+----------------+ | application | alto-flowcost+json | Section 3.1.3 | | application | alto-flowcostparam+json | Section 3.3.2 | +--------------+--------------------------+----------------+ Table 1: ALTO FCS Media Types Type name: application Gao, et al. Expires December 27, 2017 [Page 19] Internet-Draft Flow Cost Service June 2017 Subtype name: This document registers two subtypes, as listed in Table 1. Required parameters: n/a Optional parameters: n/a Encoding considerations: Encoding considerations are identical to those specified for the "applicatoin/json" media type. See [RFC7159]. Security considerations: Security considerations are identical to those specified in Section 15 of [RFC7285] . Interoperability considerations: n/a Published specification: This document is the specification for these media types. See Table 1 for the section documenting each media type. Applications that use this media type: ALTO servers and ALTO clients with the extension to support the flow cost service, either standalone or embedded within other applications. Additional information: n/a Person & email address to contact for further information: See Authors' Addresses. Intended usage: COMMON Restrictions on usage: n/a Author: See Authors' Addresses. 6.2. Header Field TBD: Create the "ALTO Header Field Name Registry". 7. Acknowledgement The authors would like to thank Dawn Chen, Haizhou Du, Sabine Randriamasy and Wendy Roome for fruitful discussions and feedback on this document. Shawn Lin provided substantial review feedback and suggestions to the protocol design. Gao, et al. Expires December 27, 2017 [Page 20] Internet-Draft Flow Cost Service June 2017 8. References 8.1. 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, . [RFC2732] Hinden, R., Carpenter, B., and L. Masinter, "Format for Literal IPv6 Addresses in URL's", RFC 2732, DOI 10.17487/RFC2732, December 1999, . [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, . 8.2. Informative References [I-D.ietf-alto-multi-cost] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost ALTO", draft-ietf-alto-multi-cost-05 (work in progress), February 2017. [I-D.wang-alto-ecs-flows] Shen, X., Zhang, J., Wang, J., and Q. Xiang, "ALTO Extension: Endpoint Cost Service for Flows", draft-wang- alto-ecs-flows-01 (work in progress), April 2016. [OF15] Foundation, O., "Openflow switch specification v1. 5.0", 2014, . [openflow] McKeown, N., Anderson, T., Balakrishnan, H., Parulkar, G., Peterson, L., Rexford, J., Shenker, S., and J. Turner, "Openflow: enabling innovation in campus networks", 2008. [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 2014, . Gao, et al. Expires December 27, 2017 [Page 21] Internet-Draft Flow Cost Service June 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, . Appendix A. Tables +------------+--------------+------------------------------+ | Protocol | Field Name | Description | +------------+--------------+------------------------------+ | Ethernet | source | The source MAC address | | | destination | The destination MAC address | | | vlan-id | VLAN-ID from 802.1Q header | | IPv4 | source | IPv4 source address | | | destination | IPv4 destination address | | IPv6 | source | IPv6 source address | | | destination | IPv6 destination address | | TCP | source | TCP source port | | | destination | TCP destination port | | UDP | source | UDP source port | | | destination | UDP destination port | +------------+--------------+------------------------------+ Table 2: Protocols and Field Names. +-----------------------+-------------------------------------------+ | Typed Header Field | Acceptable Value Type | +-----------------------+-------------------------------------------+ | ethernet:source | JSONString as MAC address | | ethernet:destination | | | ethernet:vlan-id | JSONNumber in the range of [1, 4094] | | ipv4:source | JSONString as IPv4 address or IPv4 prefix | | ipv4:destination | | | ipv6:source | JSONString as IPv6 address or IPv6 prefix | | ipv6:destination | | | tcp:source | JSONNumber in the range of [0, 65535] | | tcp:destination | 0 serves as a wildcard value | | udp:source | | | udp:destination | | +-----------------------+-------------------------------------------+ Table 3: Value Types for Typed Header Fields Gao, et al. Expires December 27, 2017 [Page 22] Internet-Draft Flow Cost Service June 2017 Authors' Addresses Kai Gao Tsinghua University 30 Shuangqinglu Street Beijing 100084 China Email: gaok12@mails.tsinghua.edu.cn Jingxuan Jensen Zhang Tongji University 4800 Cao'an Hwy Shanghai 201804 China Email: jingxuan.n.zhang@gmail.com Junzhuo Austin Wang Tongji University 4800 Cao'an Hwy, Jiading District Shanghai China Email: wangjunzhuo200@gmail.com Qiao Xiang Tongji/Yale University 51 Prospect Street New Haven, CT USA Email: qiao.xiang@cs.yale.edu Y. Richard Yang Yale University 51 Prospect St New Haven CT USA Email: yry@cs.yale.edu Gao, et al. Expires December 27, 2017 [Page 23]