[Lsr] Re: 答复: 答复: Re: 答复: I-D Action: draft-ietf-lsr-igp-ureach-prefix-announce-06.txt

[je_dr...@yahoo.com]

Right, the whole point of this extended exercise was that the steady state operation of the system relied upon covering prefixes so that individual advertisements did not  need to be sent inter-area    I think that was what Aijun intitally specified. Sent from my iPhone On May 26, 2025, at 5:53 AM, Peter Psenak <ppsenak=40cisco....@dmarc.ietf.org> wrote:  On 26/05/2025 10:26, Aijun Wang wrote: No,  summary can’t achieve the same aim of the “Explicit Withdrawn Signal”, for example, switch back to the application’s original state. you don't understand the basic operation of the protocol. 1. prefix p1/32 is summarized with p2/16. P1 is reachable via summary 2. router that generated p1 went down 3. UPA for p1/32 was generated 4. router that generated p1 came back 5. UPA was removed and we are back to state (1) Peter   发件人: Peter Psenak [mailto:ppse...@cisco.com] 发送时间: 2025年5月26日 15:41 收件人: Aijun Wang <wangai...@tsinghua.org.cn> 抄送: lsr@ietf.org 主题: Re: 答复: [Lsr] Re: 答复: I-D Action: draft-ietf-lsr-igp-ureach-prefix-announce-06.txt   On 26/05/2025 03:29, Aijun Wang wrote: Then one new deficiency for the mechanism is emerging:   The lack of the Explicit Withdrawn Signal(EWS) when the prefix is reachable again. Please note, stop sending the UPA message doesn’t mean the prefix is reachable again. If there is no EWS, then the network can’t back to its original state before the UPA signaling when the reachable of prefix recover. there is still a summary that covers the prefix reachability. Peter     Best Regards   Aijun Wang China Telecom       发件人: Peter Psenak [mailto:ppse...@cisco.com] 发送时间: 2025年5月23日 19:11 收件人: Aijun Wang <wangai...@tsinghua.org.cn> 抄送: lsr@ietf.org 主题: Re: [Lsr] Re: 答复: I-D Action: draft-ietf-lsr-igp-ureach-prefix-announce-06.txt   On 23/05/2025 12:48, Aijun Wang wrote: Then nothing needs to be standardized when the prefix becomes reachable again.   1) In some critical scenarios, when the ABR sends one UPA message out and the prefix becomes reachable immediately, what the ABR can do is to stop advertising UPA. and that is exactly what the text says. Peter     The sent UPA message will eventually trigger the action on the receiver, even the prefix is reachable immediately.   2) In normal situations, the ABR sends the UPA message for some time and stop sending it further. At this time, when the prefix becomes reachable, nothing needs to be done at ABR.   The receiver will also act on the UPA signaling.   It’s irrelevant then whether the prefix is reachable or not after the UPA signaling is sent out.      Aijun Wang China Telecom On May 23, 2025, at 17:18, Peter Psenak <ppse...@cisco.com> wrote: On 23/05/2025 10:10, Aijun Wang wrote: Then, what’s the differences between the two statements: first is for case when the prefix reachability is not regained after UPA was generated.  Second is when the prefix reachability was regained before the UPA was withdrawn. It basically says UPA must be  withdrawn at the time the prefix becomes reachable.     “UPA advertisements SHOULD therefore be withdrawn after some amount of time, that would provides sufficient time for UPA to be flooded network-wide and acted upon by receiving nodes, but limits the presence of UPA in the network.”   And:   “ABR or ASBR MUST withdraw the previously advertised UPA when the reason for which the UPA was generated was lost - e.g. prefix reachability was restored or its metric has changed such that it does not represent the protocol specific maximum prefix metric.”   Here, does  “withdraw” just mean to “stop advertisement”?  yes. Peter   If no, what’s the mechanism of second “withdraw”?     Best Regards   Aijun Wang China Telecom   发件人: forwardingalgori...@ietf.org [mailto:forwardingalgori...@ietf.org] 代表 Peter Psenak 发送时间: 2025年5月23日 14:55 收件人: Aijun Wang <wangai...@tsinghua.org.cn>; lsr@ietf.org 主题: [Lsr] Re: 答复: I-D Action: draft-ietf-lsr-igp-ureach-prefix-announce-06.txt   On 23/05/2025 03:32, Aijun Wang wrote: Hi, All:   I must point out that the updated draft doesn't address previous issues that described in [1]. Especially, the activation of flawed LSInfinity feature(there is detail analysis for this flawed feature that is defined in OSPF 2328).   And, some updated contents will deteriorate the traffic pattern within the network. For example, It says: “ABR or ASBR MUST withdraw the previously advertised UPA when the reason for which the UPA was generated was lost”. The above requirement will advertise the specific prefixes within the network, which will weaken the original summary effect, and attract the traffic via one or some of ABRs.  no, above is not true, the new text does not say to advertise reachablity for a summarized prefix, it only talks about removing the previously advertised UPA.  Please read carefully before commenting. Peter     [1]: Reasons of abandoning UPA: https://datatracker.ietf.org/doc/draft-wang-lsr-reasons-of-abandon-upa-proposal/     Best Regards   Aijun Wang China Telecom           -----邮件原件----- 发件人: forwardingalgori...@ietf.org [mailto:forwardingalgori...@ietf.org] 代表 internet-dra...@ietf.org 发送时间: 2025年5月22日 21:20 收件人: i-d-annou...@ietf.org 抄送: lsr@ietf.org 主题: [Lsr] I-D Action: draft-ietf-lsr-igp-ureach-prefix-announce-06.txt   Internet-Draft draft-ietf-lsr-igp-ureach-prefix-announce-06.txt is now available. It is a work item of the Link State Routing (LSR) WG of the IETF.      Title:   IGP Unreachable Prefix Announcement    Authors: Peter Psenak             Clarence Filsfils             Daniel Voyer             Shraddha Hegde             Gyan Mishra    Name:    draft-ietf-lsr-igp-ureach-prefix-announce-06.txt    Pages:   14    Dates:   2025-05-22   Abstract:      In the presence of summarization, there is a need to signal loss of    reachability to an individual prefix covered by the summary.  This    enables fast convergence by steering traffic away from the node which    owns the prefix and is no longer reachable.      This document describes how to use the existing protocol mechanisms    in IS-IS and OSPF, together with the two new flags, to advertise such    prefix reachability loss.   The IETF datatracker status page for this Internet-Draft is: https://datatracker.ietf.org/doc/draft-ietf-lsr-igp-ureach-prefix-announce/   There is also an HTMLized version available at: https://datatracker.ietf.org/doc/html/draft-ietf-lsr-igp-ureach-prefix-announce-06   A diff from the previous version is available at: https://author-tools.ietf.org/iddiff?url2=draft-ietf-lsr-igp-ureach-prefix-announce-06   Internet-Drafts are also available by rsync at: rsync.ietf.org::internet-drafts     _______________________________________________ Lsr mailing list -- lsr@ietf.org To unsubscribe send an email to lsr-le...@ietf.org     _______________________________________________ Lsr mailing list -- lsr@ietf.org To unsubscribe send an email to lsr-le...@ietf.org     _______________________________________________ Lsr mailing list -- lsr@ietf.org To unsubscribe send an email to lsr-le...@ietf.org

_______________________________________________
Lsr mailing list -- lsr@ietf.org
To unsubscribe send an email to lsr-le...@ietf.org