[p2pi] WG Review: Application-Layer Traffic Optimization (alto)

[IESG Secretary <[e-mail]>]

A new IETF working group has been proposed in the Applications Area.  The
IESG has not made any determination as yet.  The following draft charter
was submitted, and is provided for informational purposes only.  Please
send your comments to the IESG mailing list ([e-mail]) by Monday,
October 13, 2008.

Application-Layer Traffic Optimization (alto)
=============================================
Last Modified: 2008-09-29

Current Status: Proposed Working Group

Chair(s): TBD

Applications Area Director(s):

Lisa Dusseault (lisa at osafoundation.org)
Chris Newman (Chris.Newman at sun.com)

Applications Area Advisor:

Lisa Dusseault (lisa at osafoundation.org)

Mailing List:

General Discussion: p2pi at ietf.org
To Subscribe: https://www.ietf.org/mailman/listinfo/p2pi
Archive: http://www.ietf.org/pipermail/p2pi/

Description of Working Group:

A significant part of the Internet traffic today is generated by
peer-to-peer (P2P) applications used for file sharing, real-time
communications, and live media streaming.  P2P applications exchange
large amounts of data, often uploading as much as downloading.  In
contrast to client/server architectures, P2P applications often have  
a selection of peers and must choose.

One of the advantages of P2P systems comes from redundancy in resource
availability.  This requires choosing among download locations, yet
applications have at best incomplete information about the topology of
the network.  Applications can sometimes make empirical measurements
of link performance, but even when this is an option it takes time.
The application cannot always start out with an optimal arrangement of
peers, thus causing at least temporary reduced performance and
excessive cross-domain traffic.  Providing more information for use in
peer selection can improve P2P performance and lower ISP costs.

The Working Group will design and specify an Application-Layer Traffic
Optimization (ALTO) service that will provide applications with
information to perform better-than-random initial peer selection.
ALTO services may take different approaches at balancing factors
including maximum bandwidth, minimum cross-domain traffic, lowest cost
to the user, etc.  The WG will consider the needs of BitTorrent,
tracker-less P2P, and other applications, such as content delivery
networks (CDN) and mirror selection.

The WG will focus on the following items:

- A "problem statement" document providing a description of the
  problem and a common terminology.

- A requirements document.  This document will list requirements for
 the ALTO service, identifying, for example, what kind of information
 P2P applications will need for optimizing their choices.

- A request/response protocol for querying the ALTO service to obtain
information useful for peer selection, and a format for requests and
responses.   The WG does not require intermediaries between the ALTO
server and the peer querying it.  If the requirements analysis identifies
the need to allow clients to delegate third-parties to query the ALTO
service on their behalf, the WG will ensure that the protocol provides a
mechanism to assert the consent of the delegating client.

- A document defining core request and response formats and semantics to
communicate network preferences to applications.  Since ALTO services may
be run by entities with different level of knowledge about the underlying
network, such  preferences may have different representations. Initially
the WG will consider: IP ranges to prefer and to avoid, ranked lists of
the peers requested by the client, information about topological proximity
and approximate geographic locations.  Other usages will be considered as
extensions to the charter once the work for the initial services has been
completed.

- In order to query the ALTO server, clients must first know one or more
ALTO servers that might provide useful information.  The WG will look at
service discovery mechanisms that are in use, or defined elsewhere (e.g.
based on DNS SRV records or DHCP options).  If such discovery mechanisms
can be reused, the WG will produce a document to specify how they may be
adopted for locating such servers.  However, a new, general-purpose
service discovery mechanism is not in scope.

When the WG considers standardizing information that the ALTO server
could provide, the following criteria are important to ensure real
feasibility.

- Can the ALTO service technically provide that information?
- Is the ALTO service willing to obtain and divulge that information?
- Is it information that a client will find useful?
- Can a client get that information without excessive privacy concerns
  (e.g. by sending large lists of peers)?
- Is it information that a client cannot find easily some other way?

After these criteria are met, the generality of the data will be
considered for prioritizing standardization work, for example the
number of operators and clients that are likely to be able to provide
or use that particular data.  In any case, this WG will not propose
standards on how congestion is signaled, remediated, or avoided, and  
will not deal with information representing instantaneous network state. 
Such issues belong to other IETF areas and will be treated accordingly by
the specific area.

This WG will focus solely on the communication protocol between
applications and ALTO servers.  Note that ALTO services may be useful
in client-server environments as well as P2P environments, although
P2P environments are the first focus.  If, in the future, the IETF
considers changes to other protocols for actually implementing ALTO  
servers (e.g. application-layer protocols for Internet coordinate systems,
routing protocol extensions for ISP-based solutions), such work will
be done in strict coordination with the appropriate WGs.

Issues related to the content exchanged in P2P systems are also
excluded from the WG's scope, as is the issue dealing with enforcing
the legality of the content.

Goals and Milestones (very tentative dates):

Apr 2009: Working Group Last Call for problem statement
Jun 2009: Submit problem statement to IESG as Informational
Aug 2009: Working Group Last Call for requirements document
Oct 2009: Submit requirements document to IESG as Informational
Jan 2010: Working Group Last Call for request/response protocol
Jan 2010: Working Group Last Call for usage document for  
communicating network preferences
Mar 2010: Submit request/response protocol to IESG as Proposed  
Standard
Mar 2010: Submit usage document to IESG as Proposed Standard
May 2010: Working Group Last Call of discovery mechanism
Jul 2010: Submit discovery mechanism to IESG as Proposed Standard
Aug 2010: Dissolve or re-charter

Initial Drafts for Consideration
- draft-marocco-alto-problem-statement-02 -- Application-Layer Traffic
Optimization (ALTO) Problem Statement
- draft-kiesel-alto-reqs-00 -- Application-Layer Traffic Optimization
(ALTO) Requirements



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