Re: [alto] I-D Action: draft-ietf-alto-protocol-08.txt

[manbhard <[e-mail]>]

Hi Richard,
Yes, the use-cases that you mention use a scalar distance, however I believe
that there will be distance metrics that are vectors. There has been
discussion of using network-topology information, and also some form of
geographical distance, all of which are vectors. So it would be good if the
draft covers the use-case of vector distance that have numerical costs to be
used for logical operations, which it lacks currently.

-Thanks,
Manish.


On 5/23/11 8:44 PM, "Richard Alimi" <[e-mail]> wrote:

> Hi Manish,
> 
> On Fri, May 20, 2011 at 11:32 PM, manbhard <[e-mail]> wrote:
>> Hi Richard,
>> Thanks for your response. However, the draft seems to suggest that the
>> client can perform numerical operations (addition/subtraction) using the
>> cost, while what we seem to agree is that the numerical Cost mode is for
>> logical operations (greater than, less than etc).
> 
> One example is an application minimizing the cost to an ISP as
> computed by bandwidth distance product, where bandwidth distance
> product is computed as the sum of (cost * bandwidth) over all
> source/destination pairs.  (Note that the approach in P4P doesn't
> immediately optimize for the network, but illustrates the concept
> related to the question you asked; see the P4P paper for more
> details).
> 
> The CDN draft (draft-penno-alto-cdn) suggests one way in which one
> ALTO Provider's costs (e.g., a CDN provider) might be summed with
> another ALTO Provider's costs (e.g., a peering ISP) in certain
> circumstances (i.e., after normalization, perhaps after agreement
> between the two providers) to produce a cost for a longer network
> path.
> 
> Both of these examples use the costs in mathematical formulations, as
> opposed to only logical comparisons.
> 
> Does this make more sense?
> 
> Thanks,
> Rich
> 
>> 
>> -Thanks,
>> Manish.
>> 
>> 
>> On 5/20/11 10:50 PM, "Richard Alimi" <[e-mail]> wrote:
>> 
>>> Hi Manish,
>>> 
>>> On Fri, May 20, 2011 at 8:46 PM, manbhard <[e-mail]> wrote:
>>>> Hi,
>>>> Perhaps a late comment but the draft states -
>>>> 
>>>> 5.1.2.1.  Cost Mode: numerical
>>>> 
>>>>   This Cost Mode is indicated by the string 'numerical'.  This mode
>>>>   indicates that it is safe to perform numerical operations (e.g.
>>>>   summation) on the returned costs.
>>>> 
>>>> It would seem that summation/subtraction is never safe in vector metrics
>>>> like routing costs, geographic distances etc. Is there a use-case for this?
>>> 
>>> The basic capability that numerical costs provide over ordinal costs
>>> is that they reveal relative preference. So, extending your example
>>> below, assume that A->B is 10, A->C is 15, and A->D is 100.  Then, an
>>> ALTO Client might conclude that A->B is much better than A->D and only
>>> somewhat better than A->C.  This numerical information can be used in
>>> the optimization objective for an application. One example of how to
>>> apply this is the P4P paper from SIGCOMM '08.
>>> 
>>> The semantics of a Cost Type (as determined in the registry) should
>>> indicate the semantics that apply.  "Ordinal" removes any such
>>> semantics and gives them in sorted order of preference.
>>> 
>>>> 
>>>> That said, numerical costs are important for logical operations, i.e., if
>>>> A->B is 10 and A->C is 20, we know that B is better than C and do not have
>>>> to send another alto ordinal query with B,C both as destinations to figure
>>>> that out.
>>> 
>>> Yes - you can convert from numerical to ordinal costs. Note that an
>>> ALTO Client could request a full ordinal Cost Map to receive all of
>>> the information in a single query.  I think the main distinction
>>> instead is what was mentioned above.
>>> 
>>> Thanks,
>>> Rich
>>> 
>>>> 
>>>> -Thanks,
>>>> Manish.
>>>> 
>>>> 
>>>> On 5/20/11 11:33 AM, "[e-mail]" <[e-mail]>
>>>> wrote:
>>>> 
>>>>> A New Internet-Draft is available from the on-line Internet-Drafts
>>>>> directories. This draft is a work item of the Application-Layer Traffic
>>>>> Optimization Working Group of the IETF.
>>>>> 
>>>>> Title           : ALTO Protocol
>>>>> Author(s)       : Richard Alimi
>>>>>                           Reinaldo Penno
>>>>>                           Y. Richard Yang
>>>>> Filename        : draft-ietf-alto-protocol-08.txt
>>>>> Pages           : 75
>>>>> Date            : 2011-05-20
>>>>> 
>>>>>    Networking applications today already have access to a great amount
>>>>>    of Inter-Provider network topology information.  For example, views
>>>>>    of the Internet routing table are easily available at looking glass
>>>>>    servers and entirely practical to be downloaded by clients.  What is
>>>>>    missing is knowledge of the underlying network topology from the ISP
>>>>>    or Content Provider (henceforth referred as Provider) point of view.
>>>>>    In other words, what a Provider prefers in terms of traffic
>>>>>    optimization -- and a way to distribute it.
>>>>> 
>>>>>    The ALTO Service provides information such as preferences of network
>>>>>    resources with the goal of modifying network resource consumption
>>>>>    patterns while maintaining or improving application performance.
>>>>>    This document describes a protocol implementing the ALTO Service.
>>>>>    While such service would primarily be provided by the network (i.e.,
>>>>>    the ISP), content providers and third parties could also operate this
>>>>>    service.  Applications that could use this service are those that
>>>>>    have a choice in connection endpoints.  Examples of such applications
>>>>>    are peer-to-peer (P2P) and content delivery networks.
>>>>> 
>>>>> 
>>>>> 
>>>>> A URL for this Internet-Draft is:
>>>>> http://www.ietf.org/internet-drafts/draft-ietf-alto-protocol-08.txt
>>>>> 
>>>>> Internet-Drafts are also available by anonymous FTP at:
>>>>> ftp://ftp.ietf.org/internet-drafts/
>>>>> 
>>>>> This Internet-Draft can be retrieved at:
>>>>> ftp://ftp.ietf.org/internet-drafts/draft-ietf-alto-protocol-08.txt
>>>>> _______________________________________________
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>>>> 
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