Wendy,

Thanks for clarifying the alternatives. I also thought that we agreed on #2, 
and the sentence at 11.5.1.5 is a left over. I think a clean, simple change is 
#2: "ECS MUST NOT use a Network or Cost Map. Hence, the ECS cost is the cost 
from the source to destination endpoint. A future extension may allow ECS to 
state that it “uses” a Network Map. The extension then will need to define the 
semantics.” Does this work for you?

Richard

On Feb 25, 2014, at 3:25 PM, Wendy Roome <[email protected]> wrote:

> Richard,
> 
> I don’t like that language — it’s too wishy-washy. If an ECS can “use” a 
> Network Map, we need to spell out what that means.
> 
> So I support either of two alternatives.  
> 
> (1) Say that an ECS MAY “use” a Network Map, and spell out what that means. 
> E..g., if an ECS “uses” a Network Map, then that ECS is equivalent to a 
> Filtered Cost Map resource on that Network Map, using the PIDs of the source 
> and destination endpoint addresses. This means the client can assume the ECS 
> will return the same cost for any endpoint in the source PID to any endpoint 
> in the destination PID (modulo cost updates).
> 
> If an ECS does not “use” a Network Map, then the client can make no 
> assumptions about how the ECS costs relate to the costs for any PIDs or 
> endpoints.
> 
> (2) Say that ECS MUST NOT “use” a Network or Cost Map. The ECS cost is the 
> cost from the source to destination endpoint; the client cannot draw any 
> conclusions about costs for PIDs or other endpoints.
> 
> BTW, I thought we’d agreed on #2, until a colleague pointed out that 11.5.1.5 
> says an ECS can use a map.
> 
>       - Wendy Roome
> 
> From: "Y. Richard Yang" <[email protected]>
> Date: Tue, February 25, 2014 at 10:52
> To: Wendy Roome <[email protected]>
> Cc: IETF ALTO <[email protected]>
> Subject: Re: [alto] Ambiguity in ALTO draft 25
> 
> Hi Wendy,
> 
> Good discussion. I believe that the previous conclusion is that ECS does not 
> reveal any dependency. Hence, a simple change will be the last sentence:
> 
> "...However, to preserve flexibility, there is no need for the ECS resource 
> to declare the network map and/or cost map on which it depends."
> 
> How does this sound?
> 
> Richard
> 

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