Hi Greg, The use of HbH EH does not fit well in the case of SRH. Indeed, with the AltMark HbH Option, it is possible to monitor every router on the path with feature enabled, so it potentially allows the measurement to every nodes in the path and not only to the nodes that are identities in the SR path. While, with the Destination Option preceding a Routing Header, it is possible to apply the measurement to every destination node in the route list. This means that, when the AltMark Destination Option precedes the SRH, it allows the measurement for all the nodes that are identities in the SR path. The solution with SRH TLV is equivalent to DOH + SRH, but it can be an optimized solution for SRH since it leverages the SRH TLV capability, without adding an additional EH that can be a problem in some cases.
Regards, Giuseppe From: Greg Mirsky <gregimir...@gmail.com> Sent: Monday, November 8, 2021 2:57 PM To: Giuseppe Fioccola <giuseppe.fiocc...@huawei.com> Cc: draft-fz-spring-srv6-alt-m...@ietf.org; spring@ietf.org; i...@ietf.org Subject: Re: A question for draft-fz-spring-srv6-alt-mark Hi Giuseppe, thank you for the detailed explanation of what the authors consider as the problem. In the presentation, you've mentioned that the new AltMark SRH TLV allows for better control of which nodes along an SR Policy participate in the measurement. I imagine that the HbH IPv6 extension header that includes the AltMark TLV can be used to achieve the same result if only SR nodes are enabled for the AltMark processing. What do you think of using the HbH EH? Am I missing something? Regards, Greg On Mon, Nov 8, 2021 at 1:13 AM Giuseppe Fioccola <giuseppe.fiocc...@huawei.com<mailto:giuseppe.fiocc...@huawei.com>> wrote: Hi Greg, Thank you for your comment. It is very good to have your support on this draft. draft-ietf-6man-ipv6-alt-mark defines the AltMark DOH. In case of SRH, DOH + SRH can be used to implement the measurement for every node that is an identity in the SR path. But, the approach with DOH + SRH requires two extension headers and this can have operational implications. The goal of this draft is to find an optimized solution that best suits for SRH. Therefore we propose to use the SRH TLV. If accepted, this document would update draft-ietf-6man-ipv6-alt-mark only for SRv6: - in case of SRH there would be a single way to apply AltMark through SRH TLV, - while for all the other cases with IPv6 data plane the use of the HbH and DOH is the only choice to carry AltMark data fields. Regards, Giuseppe From: Greg Mirsky <gregimir...@gmail.com<mailto:gregimir...@gmail.com>> Sent: Sunday, November 7, 2021 9:01 PM To: draft-fz-spring-srv6-alt-m...@ietf.org<mailto:draft-fz-spring-srv6-alt-m...@ietf.org>; spring@ietf.org<mailto:spring@ietf.org>; i...@ietf.org<mailto:i...@ietf.org> Subject: A question for draft-fz-spring-srv6-alt-mark Dear Authors et al. thank you for this document. I am supporting and following the work on the Alternate Marking method in various IETF WGs. What do you see as the benefits of defining a new SRH TLV for the Alternate Marking method compared to solutions defined for IPv6 in draft-ietf-6man-ipv6-alt-mark<https://datatracker.ietf.org/doc/draft-ietf-6man-ipv6-alt-mark/>? Regards, Greg
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