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 2012Copyright Notice
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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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