Subject: [alto] Endpoint Cost Service & Network Maps

From: Wendy Roome <[email-masked]>
Date: Fri, 26 Jul 2013 14:05:41 -0400

Does it make sense to allow an Endpoint Cost Service (ECS) resource to
"use" a Network Map resource?

If it does, then that ECS is equivalent resolving the endpoints to PIDs
with that map, and getting the costs from the associated cost map.

But if an ECS resource does not "use" a network map, then that ECS is
based on some unspecified source of cost data. It might use one of the
network & cost maps, or it might use some other mechanism altogether.

As far as I can tell, the current draft doesn't say anything about this --
it neither forbids nor requires an ECS to depend on a network map. The
only guideline is that the ECS example in {8.5.4} doesn't have a "uses"
attribute. But I wasn't sure if that omission was intentional.

	- Wendy Roome

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From: "Y. Richard Yang" <[email-masked]>
Date: Fri, 26 Jul 2013 14:30:11 -0400

Hi Wendy,

Another good observation. If I remember the intension, the "omission" was
intentional. Given your feedback, I think we should add a sentence to say
that ECS has internal implementation flexibility, using publicly announced
network/cost maps, internal maps, or other mechanisms.

Richard
On Jul 26, 2013 2:05 PM, "Wendy Roome" <[email-masked]> wrote:

> _______________________________________________
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>

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From: Wendy Roome <[email-masked]>
Date: Fri, 26 Jul 2013 14:49:11 -0400

Does that mean that an ECS should NOT be declared as "using" a particular
map?  That works for me. That would mean the server is free to select the
"appropriate" map for that set of endpoints. Or some other mechanism
altogether.

But if so, the protocol should say that. How about replacing the second
paragraph of {10.4.1} with the following (additions delimited by **):

"It is important to note that although this resource allows an ALTO Server
to reveal costs between individual endpoints, an ALTO Server is not required
to do so. A simple alternative would be to compute the cost between two
endpoints as the cost between the PIDs corresponding to the endpoints,
**using one of the network maps defined by the server**. See Section 14.3
for additional details.

"**Although the Endpoint Cost resource may be based on a specific network
map, the resource MUST NOT be declared as depending on that network map (see
the "uses" attribute in Section 8.5.2).**"

From:  "Y. Richard Yang" <[email-masked]>
Date:  Fri, July 26, 2013 14:30
To:  Wendy Roome <[email-masked]>
Cc:  IETF ALTO <[email-masked]>
Subject:  Re: [alto] Endpoint Cost Service & Network Maps

Hi Wendy,

Richard

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From: "Y. Richard Yang" <[email-masked]>
Date: Fri, 26 Jul 2013 16:15:22 -0400

Yes. Because if "using" does indicate one network, it has no operational
meaning and probably only causes confusion.

paragraph of {10.4.1} with the following (additions delimited by **):
>
> "It is important to note that although this resource allows an ALTO
Server to reveal costs between individual endpoints, an ALTO Server is not
required to do so. A simple alternative would be to compute the cost
between two endpoints as the cost between the PIDs corresponding to the
endpoints, **using one of the network maps defined by the server**. See
Section 14.3 for additional details.
> "**Although the Endpoint Cost resource may be based on a specific network
map, the resource MUST NOT be declared as depending on that network map
(see the "uses" attribute in Section 8.5.2).**"

The wording reads fine to me, and I support integrate it to -18.

Thanks a lot!

Richard

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From: Richard Alimi <[email-masked]>
Date: Sun, 28 Jul 2013 11:04:10 -0700

Agreed - thanks for pointing this out Wendy and your proposed text sounds
great.

On Fri, Jul 26, 2013 at 1:15 PM, Y. Richard Yang <[email-masked]> wrote:

> > Does that mean that an ECS should NOT be declared as "using" a
> particular map?  That works for me. That would mean the server is free to
> select the "appropriate" map for that set of endpoints. Or some other
> mechanism altogether.
>
> > "**Although the Endpoint Cost resource may be based on a specific
> network map, the resource MUST NOT be declared as depending on that network
> map (see the "uses" attribute in Section 8.5.2).**"
>
> > Another good observation. If I remember the intension, the "omission"
> was intentional. Given your feedback, I think we should add a sentence to
> say that ECS has internal implementation flexibility, using publicly
> announced network/cost maps, internal maps, or other mechanisms.
> >
> > Richard
> >