This document has been reviewed as part of the transport area review team's ongoing effort to review key IETF documents. These comments were written primarily for the transport area directors, but are copied to the document's authors and WG to allow them to address any issues raised and also to the IETF discussion list for information. When done at the time of IETF Last Call, the authors should consider this review as part of the last-call comments they receive. Please always CC tsv-art@ietf.org if you reply to or forward this review. A) Section 2.1: I first missed that "SRH.Flags" is intended as reference to the flags field in the Segment Router Header. As this notation is prevalent through out the document, could you be more explicit about this notation and also maybe be clear on what a particular label represents. B) Section 2.1.1: When N receives a packet whose IPv6 DA is S and S is a local SID, the line S01 of the pseudo-code associated with the SID S, as defined in section 4.3.1.1 of [RFC8754], is modified as follows for the O-flag processing. S01.1. IF SRH.Flags.O-flag is set and local configuration permits O-flag processing THEN a. Make a copy of the packet. b. Send the copied packet, along with a timestamp to the OAM process for telemetry data collection and export. ;; Ref1 I would note that this results in the following psudo code as it states that it modifies line S01. Did you intended an insert so that S01.1 would be between S01 and SO2? This Psudeo code just lost its scoping to SRH. I would also note that it doesn't match the style of what is in RFC 8754. For example a { } the steps a and b should be present. Also with the modification in place you also have a spurious } at the end. S01.1. IF SRH.Flags.O-flag is set and local configuration permits O-flag processing THEN a. Make a copy of the packet. b. Send the copied packet, along with a timestamp to the OAM process for telemetry data collection and export. ;; Ref1 S02. If Segments Left is equal to zero { S03. Proceed to process the next header in the packet, whose type is identified by the Next Header field in the routing header. S04. } S05. Else { S06. If local configuration requires TLV processing { S07. Perform TLV processing (see TLV Processing) S08. } S09. max_last_entry = ( Hdr Ext Len / 2 ) - 1 S10. If ((Last Entry > max_last_entry) or S11. (Segments Left is greater than (Last Entry+1)) { S12. Send an ICMP Parameter Problem, Code 0, message to the Source Address, pointing to the Segments Left field, and discard the packet. S13. } S14. Else { S15. Decrement Segments Left by 1. S16. Copy Segment List[Segments Left] from the SRH to the destination address of the IPv6 header. S17. If the IPv6 Hop Limit is less than or equal to 1 { S18. Send an ICMP Time Exceeded -- Hop Limit Exceeded in Transit message to the Source Address and discard the packet. S19. } S20. Else { S21. Decrement the Hop Limit by 1 S22. Resubmit the packet to the IPv6 module for transmission to the new destination. S23. } S24. } S25. } S26. } I would also note that if you wanted more generality you could replace a and b with Execute the configured OAM process. E.g. if using IPFix that would be . C) Section 2.1.1 The processing node SHOULD rate-limit the number of packets punted to the OAM process to avoid hitting any performance impact. So this is protection against misconfiguration or an actual security breach isn't it. Because no entity outside of the domain should be able to set this on packets. So should this limit be configured by the management system or baked into the implementation. And in the later case, isn't the nodes capability to handle marked packets dependent on the total load across all packets processed at least in one processing pipe? And to me it appears that the limit will be dependent on what OAM Process that has been configured to be executed. Thus, how can this be robustly implemented so that it doesn't interfere with the telemetry? Because if there are a mismatch between the O flag marking entity and the rate limiting, then the telemetry usefulness could be compromised. Can you clarify the thoughts here? D) Section 3.1 and 3.2: I have the impression that quite a lot hides behind the "The echo reply message is IP routed." or corresponding. First of all there need to exist a return route for the source of the PING or Trace route. Secondly, as this is routed without SRV the packet can take a different return route, and in case any firewall or other filtering is in place the reply may not make it. Is this correctly interpret here? If correctly understood I am uncertain if any changes are needed. Cheers Magnus