Subject: [alto] Opaque Cost Types in ALTO Cost Maps

From: Richard Alimi <[email-masked]>
Date: Fri, 27 May 2011 09:33:15 -0700

Hi All,

This email describes a possible extension to ALTO Cost Maps that has
been discussed with a couple of people. We are looking for additional
feedback here.

It has been suggested that ALTO Cost Maps can convey additional
information beyond just raw "costs" (e.g., some numerical measurement
associated with a source, destination pair).  For example, one might
wish to allow an ALTO Cost Map to indicate that a source,destination
pair in an ALTO Cost Map has a particular enumerated value associated
with it (e.g., whether it is completely within an AS or not, crosses a
peering link, etc).

In this sense, it is more of a Path Property (an earlier version of
the protocol draft used this terminology, but "cost" seemed more
natural to readers at that time).  I'd proposed not to worry about the
terminology at this point; we can address on a separate thread when/if
making revisions to the draft to support this.

To be clear, the data type and semantics of the Cost Type will still
be indicated in the registration. This means that the registration
should indicate whether its a boolean, string, enumerated value (e.g.,
valid values and the meaning of each of the values), an array, or even
a JSON object itself.

Note that this is *not* a proposal to change the format of the
'routingcost' type. That is still a number and would remain as such.
This is a proposal to add another degree of freedom when registering
additional Cost Types.

Thoughts about this proposal? Objections?

Thanks,
Rich