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 <[email protected]> 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was withdrawn. It basically says UPA must be withdrawn at the time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“UPA advertisements SHOULD therefore be withdrawn after some amount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:*[email protected]
[mailto:[email protected]] *代表 *Peter Psenak
*发送时间:*2025年5月23日14:55
*收件人:*Aijun Wang <[email protected]>; [email protected]
*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: [email protected]
[mailto:[email protected]
<mailto:[email protected]>] 代表 [email protected]
发送时间: 2025年5月22日21:20
收件人: [email protected]
抄送: [email protected]
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/
<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
<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
<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
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