Hi Aijun,
On 30/07/2020 13:44, Aijun Wang wrote:
Hi, Peter:
Currently, we have the following consideration:
1. If not all of the ABRs announce the unreachability of the specified
prefix(the specified prefix is still up), such PUA information will continue
advertising by the unreachable ABRs.
so the behavior of ABR is going to be dependent on the behavior of the
the other ABR(s)? That is a very thin ice you are dancing on.
2. If all of the ABRs announce the PUA of the specified prefix, such
information will be announced for a configurable duration, to make sure other
protocol(for example BGP) that based on the specified prefix has converged.
well, the problem is that no mater what is your configured time to
advertise the un-reachability, you have no way of knowing whether the
resource that became unreachable have done so intentionally and whether
it will ever come back. And guessing based on the timer is not going to
make it much better I'm afraid.
thanks,
Peter
How about the above consideration and
Do you have other thoughts ?
Aijun Wang
China Telecom
On Jul 30, 2020, at 17:21, Peter Psenak <ppsenak=40cisco....@dmarc.ietf.org>
wrote:
Hi Ajun,
one additional problem on top of others that have been mentioned is how are you going to
get rid of "old" un-reachability announcements/
Let's imagine you have the following prefixes in your area 1:
- 10.10.0.1/32 - 10.0.0.255/32 - used for loopback adresses
- 10.10.1.0/30 - 10.10.10.252/32 - used for transit links
For simplicity your summary for area 1 is 10.0.0.0/16
1. Everything is up, you generate 10.0.0.0/16 on the ABR that connects to area
1 to all remaining connected areas
2. A router in area 1 with loopback 10.10.0.25/32 goes down.
3. ABR in area 1 generates un-reachable announcement for 10.0.0.25/32 to all
other connected areas
4. When does ABR stop generating the un-reachable announcement for 10.0.0.25/32? In section 6 you
mention that "The receiver router should keep the black hole routes for PUA as one
configurable time(MAX_T_PUA)", but the draft does not say anything about when the
un-reachability announcements should be removed by ABR. We can not rely on 10.10.0.25/32 ever
coming back, as the user may have simply removed it for good. Keeping the "stale"
un-reachability announcements may result in the LSDB growth over the period of time.
thanks,
Peter
On 27/07/2020 03:32, Aijun Wang wrote:
Hi, LSR experts:
We have uploaded the new version of this PUA(Prefix Unreachable Announcement)
draft. The main updates are the followings:
1) Describes the solution that using tunnel to redirect traffic among ABRs,
when all ABRs reaches the PUA limit.
2) Describe fast rerouting to avoid routing black hole.
3) Defining PUA capabilities announcements for OSPFv2/OSPFv3 and ISIS.
There are also some arguments about the current solution for PUA, for example:
1) Is it suitable to set the "Prefix Originator" sub-TLV to NULL to indicate
the prefix is unreachable?
2) if not, what's the consideration? What's the other convincible solution?
Wish to hear comments and suggestions on the above issues. We will also have
the presentation on the coming IETF LSR meeting.
Best Regards
Aijun Wang
China Telecom
-----Original Message-----
From: internet-dra...@ietf.org [mailto:internet-dra...@ietf.org]
Sent: Monday, July 27, 2020 9:16 AM
To: Zhibo Hu <huzh...@huawei.com>; Aijun Wang <wang...@chinatelecom.cn>; Yaqun Xiao
<xiaoya...@huawei.com>
Subject: New Version Notification for
draft-wang-lsr-prefix-unreachable-annoucement-03.txt
A new version of I-D, draft-wang-lsr-prefix-unreachable-annoucement-03.txt
has been successfully submitted by Aijun Wang and posted to the IETF repository.
Name: draft-wang-lsr-prefix-unreachable-annoucement
Revision: 03
Title: Prefix Unreachable Announcement
Document date: 2020-07-27
Group: Individual Submission
Pages: 11
URL:
https://www.ietf.org/internet-drafts/draft-wang-lsr-prefix-unreachable-annoucement-03.txt
Status:
https://datatracker.ietf.org/doc/draft-wang-lsr-prefix-unreachable-annoucement/
Htmlized:
https://tools.ietf.org/html/draft-wang-lsr-prefix-unreachable-annoucement-03
Htmlized:
https://datatracker.ietf.org/doc/html/draft-wang-lsr-prefix-unreachable-annoucement
Diff:
https://www.ietf.org/rfcdiff?url2=draft-wang-lsr-prefix-unreachable-annoucement-03
Abstract:
This document describes the mechanism that can be used to announce
the unreachable prefixes for service fast convergence.
Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org.
The IETF Secretariat
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