Third-Party ALTO Server Discovery (3pdisc)
draft-kist-alto-3pdisc-02
The information below is for an old version of the document.
| Document | Type |
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|---|---|---|---|
| Authors | Sebastian Kiesel , Kilian Krause, Martin Stiemerling | ||
| Last updated | 2013-02-11 | ||
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draft-kist-alto-3pdisc-02
ALTO S. Kiesel
Internet-Draft K. Krause
Intended status: Experimental University of Stuttgart
Expires: August 15, 2013 M. Stiemerling
NEC Europe Ltd.
February 11, 2013
Third-Party ALTO Server Discovery (3pdisc)
draft-kist-alto-3pdisc-02
Abstract
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. ALTO is realized by a client-server protocol. Before an
ALTO client can ask for guidance it needs to discover one or more
ALTO servers that can provide suitable guidance.
This document specifies a procedure for third-party ALTO server
discovery, which can be used if the ALTO client is not co-located
with the actual resource consumer, but instead embedded in a third
party such as a peer-to-peer tracker.
This algorithm takes a resource consumer's IP address as argument,
performs several DNS lookups (for PTR, SOA, and U-NAPTR resource
records), and produces URIs of ALTO servers that are able to give
reasonable ALTO guidance to a resource consumer willing to
communicate using this IP address.
Starting with draft-kist-alto-3pdisc-02 the algorithm has
significantly changed compared to previous versions of this document,
including draft-kiesel-alto-3pdisc-* and
draft-ietf-alto-server-discovery-*. The new algorithm does not try
"DNS tree climbing" and it does not neccessarily rely on PTR records,
i.e., it can also produce results if no PTR records are populated in
the DNS, for example when IPv6 privacy exensions are in use.
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Terminology and Requirements Language
This document makes use of the ALTO terminology defined in RFC 5693
[RFC5693].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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 August 15, 2013.
Copyright Notice
Copyright (c) 2013 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.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Third-Party ALTO Server Discovery Procedure Overview . . . . . 5
2.1. Variant 1 . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2. Variant 2 . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Third-party ALTO Server Discovery Procedure Specification . . 8
4. Deployment Considerations and Operational Considerations . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1. Normative References . . . . . . . . . . . . . . . . . . . 12
7.2. Informative References . . . . . . . . . . . . . . . . . . 12
Appendix A. Contributors List and Acknowledgments . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
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1. Introduction
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 [RFC5693]. ALTO is realized by a client-server protocol;
see requirement AR-1 in [RFC6708]. Before an ALTO client can ask for
guidance it needs to discover one or more ALTO servers that can
provide suitable guidance. For applications that use a centralized
resource directory, such as tracker-based P2P applications, the
efficiency of ALTO is significantly improved if the ALTO client is
embedded in said resource directory instead of the resource consumer
(see Section 4.1 of [I-D.ietf-alto-deployments]). The ALTO client
embedded into the resource directory asks for guidance on behalf of
the resource consumers. To that end, it needs to discover ALTO
servers that can give guidance suitable for these resource consumers,
respectively. This is called third-party party ALTO server
discovery.
This document specifies a procedure for third-party ALTO server
discovery. In other words, this document tries to meet requirement
AR-33 in [RFC6708].
The ALTO protocol specification [I-D.ietf-alto-protocol] is based on
HTTP and expects the discovery procedure to yield the HTTP(S) URI of
an ALTO server's information resouce directory. Therefore, this
document specifies an algorithm that takes a resource consumer's IP
address as argument, performs several DNS lookups (for PTR, SOA, and
U-NAPTR [RFC4848] resource records), and produces URIs of ALTO
servers that are able to give reasonable ALTO guidance to a resource
consumer willing to communicate using this IP address.
To some extent, AR-32, i.e., resource consumer initiated ALTO server
discovery, can be seen as a special case of third-party ALTO server
discovery. For that matter, an ALTO client embedded in a ressouce
consumer would have to figure out its own "public" IP address (e.g.,
using STUN [RFC5389]), and then perform the procedures described in
this document. However, note that a less flexible yet simpler
approach for resource consumer initiated ALTO server discovery is
specified in [I-D.ietf-alto-server-discovery].
A more detailed discussion of various options where to place the
funcional entities comprising the overall ALTO architecture can be
found in [I-D.ietf-alto-deployments].
Comments and discussions about this memo should be directed to the
ALTO working group: alto@ietf.org.
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2. Third-Party ALTO Server Discovery Procedure Overview
There are currently two different algorithms for ALTO third-party
server discovery, which only differ slightly in respect to handling
of the MNAME. The following two figures give an overview on these
algorithms. For a detailed specification of the U-NAPTR lookups, see
Step 2 in [I-D.ietf-alto-server-discovery].
NOTE: only one of these algorithms will eventually be specified as
the official ALTO thirt-party discovery algorithm. An analysis of
their advantages and drawbacks, respecively, and a decision is for
further study.
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2.1. Variant 1
IPv4 address IPv6 address
| |
V V
Rev=d.c.b.a.in-addr.arpa. Rev=f.e ... 1.0.ip6.arpa.
| |
\-------+-------/
V
PTR query on Rev,
answer is called Ans-PTR
one or more PTR(s) | | NXDOMAIN or
found in Ans-PTR | | other error
V |
NAPTR lookup(s) |
on these PTR(s) |
one or more | | NXDOMAIN or |
usable results | | other error |
| | |
| \-------+-------/
| V
| Auth.Section with SOA present in Ans-PTR?
| Yes | | No
| | V
| | Explicit SOA query on Rev
| | OK | | Error
| \-------+ |
| V |
| NAPTR lookup on MNAME (Responsible |
| Name Server) extracted from SOA |
| OK | | NXDOMAIN |
| | | or other |
| | | error |
+-----------/ \-----------+
V V
One or more URIs as ALTO third Algorithm failed,
party server discovery result no result yielded
Note: for a detailed specification of the NAPTR lookups see
Step 2 (Section 3.2) of draft-ietf-alto-server-discovery-07.txt
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2.2. Variant 2
IPv4 address IPv6 address
| |
V V
Rev=d.c.b.a.in-addr.arpa. Rev=f.e ... 1.0.ip6.arpa.
| |
\-------+-------/
V
PTR query on Rev,
answer is called Ans-PTR
one or more PTR(s) | | NXDOMAIN or
found in Ans-PTR | | other error
V |
NAPTR lookup(s) |
on these PTR(s) |
one or more | | NXDOMAIN or |
usable results | | other error |
| | |
| \-------+-------/
| V
| Auth.Section with SOA present in Ans-PTR?
| Yes | | No
| | V
| | Explicit SOA query on Rev
| | OK | | Error
| \-------+ |
| V |
| Take MNAME (Responsible Name Server) |
| from SOA, remove first component |
| up to and including first dot |
| | |
| V |
| NAPTR lookup on shortened MNAME |
| OK | | NXDOMAIN |
| | | or other |
| | | error |
+-----------/ \-----------+
V V
One or more URIs as ALTO third Algorithm failed,
party server discovery result no result yielded
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3. Third-party ALTO Server Discovery Procedure Specification
TBD.
The third-party ALTO server discovery procedure is performed in two
steps:
1. A DNS domain name is yieleded, by means of a DNS PTR lookup on
the resouce consumer's IP address (or the "public" IP address of
the outermost NAT in front of the resource consumer). This IP
address is the source address of application protocol messages
arriving at the resource directory. If no PTR can be found, a
SOA lookup is performed instead, and the MNAME (Responsible Name
Server) entry is extracted from it.
The two proposed algorithms differ slightly: Variant 2 chops off
the first compinent from the MNAME, i.e., nameserver.domain.tld
becomes domain.tld before the U-NAPTR lookup is performed.
2. This DNS domain name is used for an U-NAPTR lookup yielding the
URI. Further DNS lookups may be neccessary to determine the ALTO
server's IP address(es).
Note: Step 2 is identical to Step 2 specified in
[I-D.ietf-alto-server-discovery], which already specifies two
alternatives for its Step 1. Therefore, it is possible to merge both
documents to one specification with three alternatives for Step 1 and
a common Step 2.
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4. Deployment Considerations and Operational Considerations
Individual PTR records per IP address and corresponding individual
ALTO U-NAPTR records for these names allow very fine-grained
discovery of ALTO "entry point" URIs on a per-IP-address basis. If
an operator considers this procedure too cumbersome, or if IPv6
privacy extensions is to be used without dynamic DNS updates, setting
up SOA records in the in-addr.arpa. or ip6.arpa. subdomains plus
setting up corresponding ALTO U-NAPTR records will also give
reasonable, yet less fine-grained results.
Note that the ALTO server discovery procedure is supposed to produce
only a first URI of an ALTO server that can give reasonable guidance
to the client. An ALTO server can still return different results
based on the client's address (or other identifying properties)
and/or redirect the client to another ALTO server using mechanisms of
the ALTO protocol (see Sect. 6.7 of [I-D.ietf-alto-protocol]).
We assume that if two organizations share parts of their DNS
infrastructure, i.e., have a common SOA record in their in-addr.arpa.
or ip6.arpa. subdomain(s), they will also be able to operate a common
ALTO server, which may do redirections if desired or required by
policies.
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5. Security Considerations
TBD. See also [I-D.ietf-alto-server-discovery].
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6. IANA Considerations
None.
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7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2. Informative References
[I-D.ietf-alto-deployments]
Stiemerling, M. and S. Kiesel, "ALTO Deployment
Considerations", draft-ietf-alto-deployments-03 (work in
progress), November 2011.
[I-D.ietf-alto-protocol]
Alimi, R., Penno, R., and Y. Yang, "ALTO Protocol",
draft-ietf-alto-protocol-13 (work in progress),
September 2012.
[I-D.ietf-alto-server-discovery]
Kiesel, S., Stiemerling, M., Schwan, N., Scharf, M., and
S. Yongchao, "ALTO Server Discovery",
draft-ietf-alto-server-discovery-04 (work in progress),
July 2012.
[RFC4848] Daigle, L., "Domain-Based Application Service Location
Using URIs and the Dynamic Delegation Discovery Service
(DDDS)", RFC 4848, April 2007.
[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389,
October 2008.
[RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic
Optimization (ALTO) Problem Statement", RFC 5693,
October 2009.
[RFC6708] Kiesel, S., Previdi, S., Stiemerling, M., Woundy, R., and
Y. Yang, "Application-Layer Traffic Optimization (ALTO)
Requirements", RFC 6708, September 2012.
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Appendix A. Contributors List and Acknowledgments
The initial version of this document was co-authored by Marco Tomsu
<marco.tomsu@alcatel-lucent.com>.
Hannes Tschofenig provided the initial input to the U-NAPTR solution
part. Hannes and Martin Thomson provided excellent feedback and
input to the server discovery.
This memo borrows some text from [I-D.ietf-alto-server-discovery], as
the 3pdisc was historically part of that memo. Special thanks to
Michael Scharf and Nico Schwan.
Martin Stiemerling is partially supported by the CHANGE project
(http://www.change-project.eu), a research project supported by the
European Commission under its 7th Framework Program (contract no.
257422). The views and conclusions contained herein are those of the
authors and should not be interpreted as necessarily representing the
official policies or endorsements, either expressed or implied, of
the CHANGE project or the European Commission.
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Authors' Addresses
Sebastian Kiesel
University of Stuttgart Information Center
Allmandring 30
Stuttgart 70550
Germany
Email: ietf-alto@skiesel.de
URI: http://www.rus.uni-stuttgart.de/nks/
Kilian Krause
University of Stuttgart Information Center
Allmandring 30
Stuttgart 70550
Germany
Email: schreibt@normalerweise.net
URI: http://www.rus.uni-stuttgart.de/nks/
Martin Stiemerling
NEC Laboratories Europe
Kurfuerstenanlage 36
Heidelberg 69115
Germany
Phone: +49 6221 4342 113
Email: martin.stiemerling@neclab.eu
URI: http://ietf.stiemerling.org
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