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

Marshall Eubanks <> Fri, 10 October 2008 12:01 UTC

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Subject: Re: [p2pi] WG Review: Application-Layer Traffic Optimization (alto)
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I support this moving forward. My reading of the room in Dublin was  
that there was serious support
for this and certainly a critical mass to move forward.

Some comments in the charter below. This document clearly needs some  
more work. As a overall comment,
I think it is premature to discuss ALTO "servers" and would keep the  
charter focused on describing
the ALTO "service." I do not see consensus at this moment as to a  
central service solution versus a distributed


On Oct 6, 2008, at 4:35 PM, IESG Secretary wrote:

> 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 ( 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
> Chris Newman (Chris.Newman at
> Applications Area Advisor:
> Lisa Dusseault (lisa at
> Mailing List:
> General Discussion: p2pi at
> To Subscribe:
> Archive:
> 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.

s/choose/choose the best peer or peers to exchange data with/

> 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

This is strange wording, as WG themselves are not protocols.

More fundamentally, is this a requirement ? If so, it seems premature  
before a requirements draft is adopted.
Saying "The ALTO server" here also seems limiting - is there a  
solution draft describing a server ?
Others have already commented on central servers versus a distributed  
system, and to
me the charter is not the place to make such decisions.

I would remove this sentence entirely.

> 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?

I think that what is meant here is "Can the ALTO service realistically  
discover that information?"

> - Is the ALTO service willing to obtain and divulge that information?

Do computers have free will ?

More seriously, it seems very odd to assume that a P2P service will  
not do something that the owners of
the peers want it to do. In my opinion that drives P2P adoption
much more than the efficiencies of bandwidth sharing.

> - 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

What is meant by "the generality of the data" ?

> 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

Does this mean that congestion is not an issue to consider ?

If the closest peer to me was totally congested and had no available  
bandwidth, isn't that something that
I would want to know ?

> will not deal with information representing instantaneous network  
> state.

What is meant by "information representing instantaneous network  
state" ? Isn't
this a protocol to share information about the state of the network ?  
Or is this
an attempt to separate network topology from network performance ? But  
should network performance
also be an issue ?

> 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

Not according to the previous paragraphs. Service discovery is not  
part of
this communication protocol, Load balancing is not part of this, etc.

I would suggest changing "solely" to "primarily"

> 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,

What is an Internet coordinate system ?

> 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

s/is the issue/are issues/

> the legality of the content.

s/the legality of the content/copyrights/

> 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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