ALTO Working Group Y. Yang Internet-Draft Yale University Intended status: Standards Track October 24, 2021 Expires: April 27, 2022 ALTO Transport using HTTP/2 draft-yang-alto-http2-transport-01 Abstract The ALTO base protocol [RFC7285] uses HTTP/1.x as the transport protocol and hence ALTO transport includes the limitations of HTTP/1.x. ALTO/SSE [RFC8895] addresses some of the limitations, but is still based on HTTP/1.x. This document introduces ALTO/H2, which provides the transport of ALTO information resources on top of HTTP/2. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119][RFC8174] when, and only when, they appear in all capitals, as shown here. 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 April 27, 2022. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. Yang Expires April 27, 2022 [Page 1] Internet-Draft ALTO Transport Using HTTP/2 October 2021 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 2. ALTO/H2 Design Requirements . . . . . . . . . . . . . . . . . 3 3. ALTO/H2 Information Resource Directory (IRD) . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 5. ALTO based on HTTP/3 Considerations . . . . . . . . . . . . . 7 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.1. Normative References . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction Application-Layer Traffic Optimization (ALTO) provides a means for network applications to obtain network status information. The ALTO base protocol [RFC7285] is based on the sequential request and response model of HTTP/1.1 [RFC7230]; hence, in the base protocol, an ALTO client only can issue a sequence of requests on network information resources, and the ALTO server sends the information resources one-by-one, in the order of the request sequence. To address the use cases where an ALTO client may need to efficiently monitor changes to a set of network information resources and the protocol is still based on the HTTP/1.1 model, the ALTO Working Group introduces ALTO/SSE (ALTO Incremental Update based on Server-Sent- Event) [RFC8895], so that an ALTO client can manage (i.e., add and remove) a set of requests maintained at an ALTO server, and the server can continuously, concurrently, and incrementally push updates whenever a monitored network information resource changes. Figure 1 shows the architecture and message flow of ALTO/SSE, which can be considered as a more general transport protocol than the ALTO base transport protocol. Although ALTO/SSE allows the concurrent transport of multiple ALTO information resources, it has complexities and limitations: (1) it requires that the server provide a separate control URI, leading to complexity in management; (2) the data Yang Expires April 27, 2022 [Page 2] Internet-Draft ALTO Transport Using HTTP/2 October 2021 connection still suffers HTTP/1.x problems such as head-of-line (HOL) blocking. ------------------------------------------------------------------ | | | +-------+ +-------+ 1. init request +------+ | | | | | | <------------- | | | | | | | | -------------> | | | | 3.add/ | | | | 1'. control uri | | | | remove | | | | | | | | resource |Stream | |Update | | | | -------->|Control| private |Stream | 2a. data update |Client| -- |Server |<------->|Server | messages | | -------- | | | | --------------> | | <- | response | | | | --------------> | | | | | | | | 2b.control update| | | | +-------+ +-------+ messages +------+ | | | ------------------------------------------------------------------ Figure 1: ALTO SSE Architecture and Message Flow. This document specifies ALTO/H2, based on HTTP/2 [RFC7540]. The newer transport can provide multiple benefits: o ALTO based on HTTP/2 natively supports multiple concurrent requests pending at the server, realizing a main design goal of ALTO SSE. At the same time, instead of using multiple TCP connections (a control connection and a data connection) as ALTO/ SSE does, ALTO based on HTTP/2 can use a single TCP connection, achieving a design with only one connection. o ALTO based on HTTP/2 can take advantage of the benefit provided by HTTP/2 to avoid head-of-line blocking in the data connection, reducing latency. o ALTO based on HTTP/2 can take advantage of other benefits of HTTP/2, including potentially higher encoding efficiency and stronger enforcement of security (i.e., using https). 2. ALTO/H2 Design Requirements To realize the functions of ALTO/SSE, there are the following requirements: Yang Expires April 27, 2022 [Page 3] Internet-Draft ALTO Transport Using HTTP/2 October 2021 o R0: Client can request any resource using the connection, just as using ALTO base protocol using HTTP/1.x. o R1: The client can signal the addition (start) of incremental updates to a resource. o R2: The client can signal the deletion (stop) of incremental updates to a resource. o R3: The server can signal to the client the start or stop of incremental updates to a resource. o R4: The server can choose the type of each incremental update endcoding, as long as the type is indicated to be acceptable by the client. 3. ALTO/H2 Information Resource Directory (IRD) Extending the IRD example in Section 8.1 of [RFC8895], Figure 2 is the IRD of an ALTO server supporting ALTO base protocol, ALTO/SSE, and ALTO/H2. In particular, "my-network-map": { "uri": "https://alto.example.com/networkmap", "media-type": "application/alto-networkmap+json", }, "my-routingcost-map": { "uri": "https://alto.example.com/costmap/routingcost", "media-type": "application/alto-costmap+json", "uses": ["my-networkmap"], "capabilities": { "cost-type-names": ["num-routingcost"] } }, "my-hopcount-map": { "uri": "https://alto.example.com/costmap/hopcount", "media-type": "application/alto-costmap+json", "uses": ["my-networkmap"], "capabilities": { "cost-type-names": ["num-hopcount"] } }, "my-filtered-cost-map": { "uri": "https://alto.example.com/costmap/filtered/constraints", "media-type": "application/alto-costmap+json", "accepts": "application/alto-costmapfilter+json", Yang Expires April 27, 2022 [Page 4] Internet-Draft ALTO Transport Using HTTP/2 October 2021 "uses": ["my-networkmap"], "capabilities": { "cost-type-names": ["num-routingcost", "num-hopcount"], "cost-constraints": true } }, "my-simple-filtered-cost-map": { "uri": "https://alto.example.com/costmap/filtered/simple", "media-type": "application/alto-costmap+json", "accepts": "application/alto-costmapfilter+json", "uses": ["my-networkmap"], "capabilities": { "cost-type-names": ["num-routingcost", "num-hopcount"], "cost-constraints": false } }, "my-props": { "uri": "https://alto.example.com/properties", "media-type": "application/alto-endpointprops+json", "accepts": "application/alto-endpointpropparams+json", "capabilities": { "prop-types": ["priv:ietf-bandwidth"] } }, "my-pv": { "uri": "https://alto.example.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" ] } }, "update-my-costs": { "uri": "https://alto.example.com/updates/costs", "media-type": "text/event-stream", "accepts": "application/alto-updatestreamparams+json", "uses": [ "my-network-map", "my-routingcost-map", "my-hopcount-map", "my-simple-filtered-cost-map" ], "capabilities": { "incremental-change-media-types": { "my-network-map": "application/json-patch+json", "my-routingcost-map": "application/merge-patch+json", Yang Expires April 27, 2022 [Page 5] Internet-Draft ALTO Transport Using HTTP/2 October 2021 "my-hopcount-map": "application/merge-patch+json" }, "support-stream-control": true } }, "update-my-costs-h2": { "uri": "https://alto.example.com/updates-h2/costs", "media-type": "application/alto-h2", "accepts": "application/alto-updatestreamparams+json", "uses": [ "my-network-map", "my-routingcost-map", "my-hopcount-map", "my-simple-filtered-cost-map" ], "capabilities": { "incremental-change-media-types": { "my-network-map": "application/json-patch+json", "my-routingcost-map": "application/merge-patch+json", "my-hopcount-map": "application/merge-patch+json" }, "support-stream-control": true } }, "update-my-props": { "uri": "https://alto.example.com/updates/properties", "media-type": "text/event-stream", "uses": [ "my-props" ], "accepts": "application/alto-updatestreamparams+json", "capabilities": { "incremental-change-media-types": { "my-props": "application/merge-patch+json" }, "support-stream-control": true } }, "update-my-pv": { "uri": "https://alto.example.com/updates/pv", "media-type": "text/event-stream", "uses": [ "my-pv" ], "accepts": "application/alto-updatestreamparams+json", "capabilities": { "incremental-change-media-types": { "my-pv": "application/merge-patch+json" }, "support-stream-control": true } Yang Expires April 27, 2022 [Page 6] Internet-Draft ALTO Transport Using HTTP/2 October 2021 } Note that it is straightforward for an ALTO sever to run HTTP/2 and support concurrent retrieval of multiple resources such as "my- network-map" and "my-routingcost-map" using multiple HTTP/2 streams with the need to introducing ALTO/H2. The resource "update-my-costs-h2" provides an ALTO/H2 based connection, and this is indicated by the media-type "application/ alto-h2". For an ALTO/H2 connection, the client can send in a sequence of control requests using media type application/alto- updatestreamparams+json. The server creates HTTP/2 streams and pushes updates to the client. 4. Security Considerations The properties defined in this document present no security considerations beyond those in Section 15 of the base ALTO specification [RFC7285]. 5. ALTO based on HTTP/3 Considerations One consideration of the ALTO/H2 design is the pending deployment of HTTP3. 6. IANA Considerations IANA will need to register the alto-h2 media type under ALTO registry as defined in [RFC7285]. 7. Acknowledgments The authors of this document would also like to thank many for the reviews and comments. 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, . [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, DOI 10.17487/RFC7230, June 2014, . Yang Expires April 27, 2022 [Page 7] Internet-Draft ALTO Transport Using HTTP/2 October 2021 [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, . [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext Transfer Protocol Version 2 (HTTP/2)", RFC 7540, DOI 10.17487/RFC7540, May 2015, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8895] Roome, W. and Y. Yang, "Application-Layer Traffic Optimization (ALTO) Incremental Updates Using Server-Sent Events (SSE)", RFC 8895, DOI 10.17487/RFC8895, November 2020, . 8.2. Informative References [RFC7971] Stiemerling, M., Kiesel, S., Scharf, M., Seidel, H., and S. Previdi, "Application-Layer Traffic Optimization (ALTO) Deployment Considerations", RFC 7971, DOI 10.17487/ RFC7971, October 2016, . Author's Address Y. Richard Yang Yale University 51 Prospect St New Haven, CT 06520 USA Email: yry@cs.yale.edu Yang Expires April 27, 2022 [Page 8]