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Application-Layer Traffic Optimization (ALTO) Requirements
RFC 6708

Internet Engineering Task Force (IETF)                    S. Kiesel, Ed.
Request for Comments: 6708                       University of Stuttgart
Category: Informational                                       S. Previdi
ISSN: 2070-1721                                      Cisco Systems, Inc.
                                                          M. Stiemerling
                                                         NEC Europe Ltd.
                                                               R. Woundy
                                                     Comcast Corporation
                                                                 Y. Yang
                                                         Yale University
                                                          September 2012

       Application-Layer Traffic Optimization (ALTO) Requirements

Abstract

   Many Internet applications are used to access resources, such as
   pieces of information or server processes that are available in
   several equivalent replicas on different hosts.  This includes, but
   is not limited to, peer-to-peer file sharing applications.  The goal
   of Application-Layer Traffic Optimization (ALTO) is to provide
   guidance to applications that have to select one or several hosts
   from a set of candidates capable of providing a desired resource.
   This guidance shall be based on parameters that affect performance
   and efficiency of the data transmission between the hosts, e.g., the
   topological distance.  The ultimate goal is to improve performance or
   Quality of Experience in the application while reducing the
   utilization of the underlying network infrastructure.

   This document enumerates requirements for specifying, assessing, or
   comparing protocols and implementations.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6708.

Kiesel, et al.                Informational                     [Page 1]
RFC 6708                    ALTO Requirements             September 2012

Copyright Notice

   Copyright (c) 2012 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 and Architectural Framework  . . . . . . . . . . .  3
     2.1.  Requirements Notation  . . . . . . . . . . . . . . . . . .  3
     2.2.  ALTO Terminology . . . . . . . . . . . . . . . . . . . . .  3
     2.3.  Architectural Framework for ALTO . . . . . . . . . . . . .  5
   3.  ALTO Requirements  . . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  ALTO Client Protocol . . . . . . . . . . . . . . . . . . .  5
       3.1.1.  General Requirements . . . . . . . . . . . . . . . . .  5
       3.1.2.  Host-Group Descriptor Support  . . . . . . . . . . . .  6
       3.1.3.  Rating Criteria Support  . . . . . . . . . . . . . . .  7
       3.1.4.  Placement of Entities and Timing of Transactions . . .  9
       3.1.5.  Protocol Extensibility . . . . . . . . . . . . . . . . 11
       3.1.6.  Error Handling and Overload Protection . . . . . . . . 11
     3.2.  ALTO Server Discovery  . . . . . . . . . . . . . . . . . . 12
     3.3.  Security and Privacy . . . . . . . . . . . . . . . . . . . 13
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
     5.1.  High-Level Security Considerations . . . . . . . . . . . . 14
     5.2.  Information Disclosure Scenarios . . . . . . . . . . . . . 14
       5.2.1.  Classification of Information Disclosure Scenarios . . 14
       5.2.2.  Discussion of Information Disclosure Scenarios . . . . 16

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