Application-Layer Traffic Optimization (ALTO) Incremental Updates Using Server-Sent Events (SSE)
RFC 8895

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Internet Engineering Task Force (IETF)                          W. Roome
Request for Comments: 8895                               Nokia Bell Labs
Category: Standards Track                                        Y. Yang
ISSN: 2070-1721                                          Yale University
                                                           November 2020

Application-Layer Traffic Optimization (ALTO) Incremental Updates Using
                        Server-Sent Events (SSE)

Abstract

   The Application-Layer Traffic Optimization (ALTO) protocol (RFC 7285)
   provides network-related information, called network information
   resources, to client applications so that clients can make informed
   decisions in utilizing network resources.  This document presents a
   mechanism to allow an ALTO server to push updates to ALTO clients to
   achieve two benefits: (1) updates can be incremental, in that if only
   a small section of an information resource changes, the ALTO server
   can send just the changes and (2) updates can be immediate, in that
   the ALTO server can send updates as soon as they are available.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8895.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
   2.  Terms
     2.1.  Requirements Language
   3.  Background
     3.1.  Incremental Encoding: JSON Merge Patch
       3.1.1.  JSON Merge Patch Encoding
       3.1.2.  JSON Merge Patch ALTO Messages
     3.2.  Incremental Encoding: JSON Patch
       3.2.1.  JSON Patch Encoding
       3.2.2.  JSON Patch ALTO Messages
     3.3.  Multiplexing and Server Push: HTTP/2
     3.4.  Server Push: Server-Sent Event
   4.  Overview of Approach and High-Level Protocol Message Flow
     4.1.  Update Stream Service Message Flow
     4.2.  Stream Control Service Message Flow
     4.3.  Service Announcement and Management Message Flow
   5.  Update Messages: Data Update and Control Update Messages
     5.1.  Generic ALTO Update Message Structure
     5.2.  ALTO Data Update Message
     5.3.  ALTO Control Update Message
   6.  Update Stream Service
     6.1.  Media Type
     6.2.  HTTP Method
     6.3.  Capabilities
     6.4.  Uses
     6.5.  Request: Accept Input Parameters
     6.6.  Response
     6.7.  Additional Requirements on Update Stream Service
       6.7.1.  Event Sequence Requirements
       6.7.2.  Cross-Stream Consistency Requirements
       6.7.3.  Multipart Update Requirements
     6.8.  Keep-Alive Messages
   7.  Stream Control Service
     7.1.  URI
     7.2.  Media Type
     7.3.  HTTP Method
     7.4.  IRD Capabilities & Uses
     7.5.  Request: Accept Input Parameters
     7.6.  Response
   8.  Examples
     8.1.  Example: IRD Announcing Update Stream Services
     8.2.  Example: Simple Network and Cost Map Updates
     8.3.  Example: Advanced Network and Cost Map Updates
     8.4.  Example: Endpoint Property Updates
     8.5.  Example: Multipart Message Updates
   9.  Operation and Processing Considerations
     9.1.  Considerations for Choosing Data Update Messages
     9.2.  Considerations for Client Processing Data Update Messages
     9.3.  Considerations for Updates to Filtered Cost Maps
     9.4.  Considerations for Updates to Ordinal Mode Costs
     9.5.  Considerations for SSE Text Formatting and Processing
   10. Security Considerations
     10.1.  Update Stream Server: Denial-of-Service Attacks
     10.2.  ALTO Client: Update Overloading or Instability
     10.3.  Stream Control: Spoofed Control Requests and Information
            Breakdown
   11. Requirements on Future ALTO Services to Use This Design
   12. IANA Considerations
     12.1.  application/alto-updatestreamparams+json Media Type
     12.2.  application/alto-updatestreamcontrol+json Media Type
   13. Appendix: Design Decision: Not Allowing Stream Restart