I just noticed that draft 25 says that an Endpoint Cost Service MAY be
declared as depending on a network/cost map:
> 11.5.1.5. Uses
> 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 implementation of an ECS resource
> may compute the cost between two endpoints as the cost between the
> PIDs corresponding to the endpoints, using one of the exposed network
> and cost maps defined by the server. However, to preserve
> flexibility, the ECS resource MAY omit declaring in the "uses"
> attribute the network map and/or cost map on which it depends.
>
The ambiguity is whether the ECS uses a Network Map, a Cost Map, or both.
ECS is a post-mode service, and can return one of several different cost
types, as selected by the client. So if an ECS uses a Cost Map, it would
have to use several Cost Maps, one for each cost-type it ca return.
The IRD example doesn¹t help, because that ECS resource doesn¹t have a
³uses² attribute.
My suggestion: say that if ECS uses anything, it just uses the Network Map.
The client can infer the related Cost Maps they¹re the ones that use that
Network Map. Eg, change the last sentence to:
> Accordingly, the ECS resource MAY declare a Network Map resource in its ³uses²
> attribute. If the ECS does so, the ECS costs should be consistent with those
> returned by the Cost Map resources associated with that Network Map.
>
and maybe add a ³uses² attribute to the ECS IRD example in 9.2.3, as in:
> "endpoint-cost" : {
>
> "uri" : "http://alto.example.com/endpointcost/lookup";,
>
> "media-type" : "application/alto-endpointcost+json",
>
> "accepts" : "application/alto-endpointcostparams+json²,
>
> "capabilities" : {
>
> "cost-constraints" : true,
>
> "cost-type-names" : [ "num-routing", "num-hop",
>
> "ord-routing", "ord-hop"]
>
> },
>
> ³uses² : [ ³my-default-network-map² ]
>
> }
>
>
If y¹all agree, can we get this in the rfc, or does it need to wait for an
errata?
- Wendy Roome
_______________________________________________
alto mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/alto
