I've performed a (late, apologies) early TSV-ART review of draft-ietf-alto-performance-metrics-03. 

The set of metrics chosen by the document seem broadly useful and sane, and the integration into ALTO makes sense. However, there are a few issues with the details.

Periodic One Way Delay, RTT, and PDV are defined in terms of section 8, section 4, and section 5, respectively, of draft-ietf-ippm-initial-registry, which specify active measurement test methodologies at layer 4 for one-way and round-trip delay using UDP packets. This does not seem it can be measured directly using the routing  technologies the authors have identified as their source of information. Is the intention that dedicated active measurement hardware be used to measure delay using UDP packets, or should these metrics reference [RFC2679] and [RFC2681] and leave the methodology undefined, instead?

The examples for these don't make much sense: the units are expressed in seconds, but Internet-scale delays are generally millisecond-scale, and the examples given contain only integers. Similarly, packet loss rate is given in percentile, but there are wide variations in usability between a path with 0%, 1%, and 2% packet loss. Is this simply an issue with the examples?

The hop count metric is underspecified: are these IP-experienced hops at layer 3, as can be measured by traceroute? 

Nit: section 2.1 refers to [OSPF-TE], [ISIS-TE], [BGP-LS] and [BGP-PM], but these are not listed as such as references in the references section. Please use consistent reference labels.

Thanks, cheers,

Brian