Internet DRAFT - draft-yang-alto-http2-transport

draft-yang-alto-http2-transport







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
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   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.




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   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   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



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   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:





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   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",



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       "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",



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           "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
       }



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     }

   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, <https://www.rfc-editor.org/info/
              rfc2119>.

   [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, <https://www.rfc-
              editor.org/info/rfc7230>.



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   [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,
              <https://www.rfc-editor.org/info/rfc7285>.

   [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540, DOI
              10.17487/RFC7540, May 2015, <https://www.rfc-
              editor.org/info/rfc7540>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [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, <https://www.rfc-editor.org/info/rfc8895>.

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, <https://www.rfc-editor.org/info/
              rfc7971>.

Author's Address

   Y. Richard Yang
   Yale University
   51 Prospect St
   New Haven, CT  06520
   USA

   Email: yry@cs.yale.edu














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