Summary: Needs 8 more YES or NO OBJECTION positions to pass.
Section 1 test. However, metrics for assessment of path components and related performance aspects had not been attempted in IPPM when the [RFC2330] framework was written. nit(?): this seems to be the only place in the document that uses the phrase "path component", and it was a bit confusing to me. That is, I'm used to seeing "path component" being (e.g.) one hop or link in a multi-link path from source to destination, but the context here suggests that it might be referring to something more like a single route within a route ensemble. I don't have a specific proposed change; I just wanted to mention that I puzzled over this wording for a bit. Section 2 Also, to specify a framework for active methods of measurement which use the techniques described in [PT] at a minimum, and a framework for hybrid active-passive methods of measurement, such as the Hybrid Type I method [RFC7799] described in [I-D.ietf-ippm-ioam-data](intended only for single administrative domains), which do not rely on ICMP and provide a protocol for explicit interrogation of nodes on a path. [...] nit: could you remind us that the "Also" refers to the scope of this work (the previous paragraph started with "The scope is" but there was a fair bit of intervening stuff between there and here). Hop A Hop MUST contain a Node Identity, and MAY contain arrival and/ or departure interface identification, round trip delay, and an arrival timestamp. In my head a "hop" is the operation of going from node A to node B, i.e., the journey and not the destination. So if we're associating a node identity with the hop, would we need to say if that's the source or destination node of the "hop" (or am I just misunderstanding things)? Section 3.3 Nmax, the largest value of i needed for a packet to be received at Dst (sent between T0 and Tf). Nmax may be equal to N. I'm not really sure I understand how Nmax works. That is, for any given packet, it has a value for 'i', and that packet may or may not be delivered. But with 'i' defined as the limit on the number of hops for "a specific packet may visit", I don't see how we get to do multiple tries for the same packet with different 'i', as we would need to do in order to determine the "largest value of i *needed*" (emphasis mine). That is, we can set 'i' unreasonably large and that would result in delivery, but that does not (as I understand it) meet the definition for Nmax -- Nmax is supposed to be a boundary value for some condition. I'm just not entirely clear on exactly what that boundary is, since we're talking about a specific packet, and my understanding is that we only get one crack at a specific packet. o t(i,j) Arrival Timestamp (where t(i,j) is ideally supplied by the Hop, or approximated from the sending time of the packet that revealed the Hop) I'm getting a bit of deja vu as I write this, but it seems risky to propose using the term "arrival timestamp" both for something generated at the Hop and something generated by the sender of the packet, since that loses information about the accuracy of the value for a given use case. Perhaps it's best to reserve the term for the ideal quantity and leave approximations for the processing pipeline (as opposed to the measurement pipeline). Section 3.4 RTL(i,j,T) is defined as a singleton of the [RFC6673] Round-trip Loss between the Node with address = Src and the Node at Hop h(i,j) at time T. Just to check my understanding: does the "singleton" and "at time T" force us into a logical (boolean) loss metric for this case, as opposed to a sample-ratio-type loss metric? Section 3.6 identities at a minimum. The models need to be expanded to include these features, as well as Arrival Interface ID, Departure Interface ID, and Arrival Timestamp, when available. [...] Is this expected to occur as future work? (Is there an I-D worth referencing?) Section 4.1 Internet routing is complex because it depends on the policies of thousands of Autonomous Systems (AS). While most of the routers perform load balancing on flows using Equal Cost Multiple Path (ECMP), a few still divide the workload through packet-based techniques. The former scenario is defined according to [RFC2991], while the latter generates a round-robin scheme to deliver every new outgoing packet. [...] I was surprised to see "packet-based techniques" refer to a round-robin scheme for queuing outgoing packets across interfaces, but assume this just means I need to do more background reading. Any tips for where to start? Formally, to maintain the same flow in the measurements to a particular hop, the Type-P-Route-Ensemble-Method-Variant packets should be[PT]: It's not entirely clear that we need a reference for these attributes; they seem to be fairly easy to verify independently, IIUC. o TCP case: For IPv4, the fields Src, Dst, port-Src, port_Dst, sequence number, and Diffserv Field SHOULD be the same. For IPv6, the field FlowLabel, Src and Dst SHOULD be the same. Are we happy to pair "to maintain the same flow" (previous paragraph) with "SHOULD be the same" (here, and subsequent bullet points)? Section 4.1 1. SHOULD occasionally check path portions which have exhibited stable results over time, particularly ingress and egress portions of the path. Do we want to give any (e.g., order of magnitude) guidance for "occasionally"? Section 4.2 In addition to node identity, nodes may also identify the ingress and egress interfaces utilized by the tracing packet, the time of day when the packet was processed, and other generic data (as described nit: I'd consider "absolute time" over "time of day", since the latter may have connotations of implying that there is 24-hour-periodic behavior. (It may also be subject to local time zone on the node inserting the value.) Section 4.3 1. Nodes at the ingress to the domain SHOULD be both Discoverable and Cooperating, and SHOULD reveal the same Node Identity in response to both active and hybrid methods. The second clause here seems redundant with point (2) that follows. (Similarly for point (3)'s similar clause.) That is, the recommendation to use the same identity for both methods can only ever apply when the node in question is both Discoverable and Cooperating -- if it's only one, then there will only be one identity available, and no need for consistency across methods. When Nodes follow these requirements, it becomes a simple matter to Perhaps a philosophical question, but are "SHOULD"-level directives more of "requirements" or "guidelines"? Section 5 traffic load is not stationary. Nonetheless, as the first approach, a link seems to be congested if, after sending several traceroute probes, it is possible to detect congestion observing different statistics parameters (e.g., see [IDCong]). Finally, to recognize nit: please check the wording of this sentence; I think there may be a missing word or similar. Section 6 every hop. This procedure could be done for a single Member Route flow, with parameter E set as False, or for every detected Route Ensemble flow (E=True). nit: I don't think we define 'E' until the full procedure, a few paragraphs below. made. Line 8 and 13 set a timer for each cycle of measurements. A cycle comprises the traceroutes packets, considering every possible Hop and the alternatives paths in the Alt variable (ensured in lines 9-12). [...] I recognize that this is pseudocode, but "what if the advanced-traceroute() operation takes longer than the i_t time?" Section 7 We could consider some bland statement about the measurement technologies (e.g., ICMP) not providing cryptographic protection for the requested/returned data, and the risks of processing untrusted data in general. This is particularly true for reverse DNS data, used in determining whether node identities represent the same node or not, since DNSSEC deployment remains inconsistent (especially for the reverse zone). The security considerations that apply to any active measurement of live paths are relevant here as well. See [RFC4656] and [RFC5357]. (The security considerations of 5357 don't seem to be adding much discussion, here, though I don't object to referencing it.) Section 9 Should we intuitively know who the "original 3 authors" are? Section 11.1 I was surprised to see draft-ietf-ippm-ioam-data in the normative references section, as all the previous discussion was consistent with merely an informative reference. Similarly, RFCs 5388, 5835, 6437, and 7312 do not seem to be referenced in a fashion that requires a normative reference.