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

[Richard Alimi <[e-mail]>]

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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>
>