Robert,
On 31/08/2023 01:18, Robert Raszuk wrote:
*Hi Les,*
But existing implementations will NOT ignore a prefix reachability advertisement just because
it has a source Router ID set to 0 as draft-wang-lsr-prefix-unreachable-annoucement defines.
True, but let's do not forget the bigger picture here. The dst is
already covered by summary so for the
app it really does not matter ... It is reachable anyway.
Bottom line is that both solutions need to have upgraded code to use the
new trigger.
*Dear LSR chairs,*
I am not sure what harm would it make to start WG adoption call on both
drafts and see the results.
So far I am not seeing strong and uniform adoption support for either
one :)
I hope you are not serious. Having two different ways of signalling the
same thing in a protocol is hardy something you would want.
thanks,
Peter
Not sure why some authors feel like their work was rejected.
Cheers,
R.
On Thu, Aug 31, 2023 at 4:57 AM Les Ginsberg (ginsberg)
<ginsberg=40cisco....@dmarc.ietf.org
<mailto:40cisco....@dmarc.ietf.org>> wrote:
Zhibo -____
__ __
Please see inline.____
__ __
> -----Original Message-----
> From: Huzhibo <huzhibo=40huawei....@dmarc.ietf.org
<mailto:40huawei....@dmarc.ietf.org>>
> Sent: Wednesday, August 30, 2023 6:33 PM
> To: Les Ginsberg (ginsberg) <ginsb...@cisco.com
<mailto:ginsb...@cisco.com>>; Peter Psenak (ppsenak)
> <ppse...@cisco.com <mailto:ppse...@cisco.com>>; linchangwang
<linchangwang.04...@h3c.com <mailto:linchangwang.04...@h3c.com>>;
> Acee Lindem <acee.i...@gmail.com <mailto:acee.i...@gmail.com>>;
lsr <lsr@ietf.org <mailto:lsr@ietf.org>>
> Cc: draft-ppsenak-lsr-igp-unreach-prefix-annou...@ietf.org
<mailto:draft-ppsenak-lsr-igp-unreach-prefix-annou...@ietf.org>
> Subject: RE: [Lsr] Working Group Adoption of "IGP Unreachable Prefix
> Announcement" - draft-ppsenak-lsr-igp-unreach-prefix-announce-04
>
> Hi Les:
>
> I think you may have connected something. Existing routers,
on receiving a
> prefix reachability advertisement with a
> U-Flag described in
https://datatracker.ietf.org/doc/draft-ppsenak-lsr-igp-
<https://datatracker.ietf.org/doc/draft-ppsenak-lsr-igp-ureach-prefix-announce/>
> ureach-prefix-announce/
<https://datatracker.ietf.org/doc/draft-ppsenak-lsr-igp-ureach-prefix-announce/>
also will interpret that prefix as being reachable.
__ __
[LES:] This statement is incorrect.____
RFC 5305 states:____
__ __
<snip>____
If a prefix is advertised with a metric larger then MAX_PATH_METRIC____
(0xFE000000, see paragraph 3.0), this prefix MUST NOT be
considered____
during the normal SPF computation. This allows advertisement of
a____
prefix for purposes other than building the normal IP routing
table.____
<end snip>____
__ __
(Equivalent statement in RFC 5308 for IPv6)____
__ __
Existing implementations will ignore the advertisement purely on the
basis of the metric value - this does not depend upon understanding
the U bit.____
__ __
But existing implementations will NOT ignore a prefix reachability
advertisement just because it has a source Router ID set to 0 as
draft-wang-lsr-prefix-unreachable-annoucement defines.____
__ __
It is worth noting that AFTER the publication of
draft-ppsenak-lsr-igp-pfx-reach-loss-00 in March 2022 (subsequently
renamed as draft-ppsenak-lsr-igp-ureach-prefix-announce), the
authors of draft-wang-lsr-prefix-unreachable-annoucement apparently
realized they had an interoperability problem with existing routers
(something many of us had been highlighting for years) and in V10
(published in Jul 2022) an option was added to advertise using
maximum metric (the solution already proposed by draft-ppsenak). But
because the authors apparently didn’t want to abandon the use of
"Router ID = 0", the new version of the draft proposed a dependency
on how the unreachable prefix should be advertised. If all routers
in the network indicated support for the new extension (indicated by
yet another protocol extension - a new Router Capability sub-TLV for
IS-IS) then the use of Router ID = 0 could be used, but if any
router in the network did not advertise the new capability, then the
use of max-metric is required. Which means the solution requires
routers advertising unreachability to potentially regenerate the
advertisement in a different form whenever the state of support by
all routers in the network for the extension changes.____
__ __
> Both two draft used The 0xFE000000 metric indicates that the
prefix is not
> reachable. Doesn't make a difference at this point.
__ __
[LES:] The solution defined in
draft-ppsenak-lsr-igp-unreach-prefix-announce does not introduce any
interoperability issues with existing routers, does not require
multiple encoding formats, and does not require a router to
regenerate advertisements in a different form based on the state of
support by all routers in the network.____
I think this makes a big difference. 😊____
__ __
Les____
__ __
>
> Thanks
>
> Zhibo Hu
>
> > -----Original Message-----
> > From: Lsr [mailto:lsr-boun...@ietf.org
<mailto:lsr-boun...@ietf.org>] On Behalf Of Les Ginsberg
> > (ginsberg)
> > Sent: Thursday, August 31, 2023 12:31 AM
> > To: Peter Psenak <ppsenak=40cisco....@dmarc.ietf.org
<mailto:ppsenak=40cisco....@dmarc.ietf.org>>; linchangwang
> > <linchangwang.04...@h3c.com
<mailto:linchangwang.04...@h3c.com>>; Acee Lindem
<acee.i...@gmail.com <mailto:acee.i...@gmail.com>>;
> > lsr <lsr@ietf.org <mailto:lsr@ietf.org>>
> > Cc: draft-ppsenak-lsr-igp-unreach-prefix-annou...@ietf.org
<mailto:draft-ppsenak-lsr-igp-unreach-prefix-annou...@ietf.org>
> > Subject: Re: [Lsr] Working Group Adoption of "IGP Unreachable
Prefix
> > Announcement" - draft-ppsenak-lsr-igp-unreach-prefix-announce-04
> >
> > Changwang -
> >
> > It is very important to note ...
> >
> > <snip>
> > > > 2. The Draft #1 utilizes the existing mechanisms [RFC7794] and
> > > > [RFC9084] to
> > > indicate reachability by checking whether the originator
information
> > > is
> > > > NULL.
> > <end snip>
> >
> > This statement is incorrect. There is no existing mechanism
defined in the
> > protocol that states that a prefix reachability advertisement
sent with a
> > source router ID == 0 implies unreachability.
> > Please see
https://www.rfc-editor.org/rfc/rfc7794.html#section-2.2
<https://www.rfc-editor.org/rfc/rfc7794.html#section-2.2>
> >
> > Existing routers, on receiving a prefix reachability
advertisement with a
> > Source Router ID == 0 will interpret that prefix as being
reachable - which
> > is exactly the opposite of the intent defined in
> >
https://www.ietf.org/archive/id/draft-wang-lsr-prefix-unreachable-annouc
<https://www.ietf.org/archive/id/draft-wang-lsr-prefix-unreachable-annouc>
> > ement-12.txt
> > This is one of the things which is broken in this draft.
> > This fact has been pointed out to the authors many times over
the years -
> > but they have consistently ignored it.
> >
> > On the other hand,
> >
https://www.ietf.org/archive/id/draft-ppsenak-lsr-igp-ureach-prefix-annou
<https://www.ietf.org/archive/id/draft-ppsenak-lsr-igp-ureach-prefix-annou>
> > nce-04.txt uses an existing mechanism defined in RFC 5305 to
insure that
> > legacy routers who do not understand the new use case or the
new flags
> > will ignore the prefix reachability advertisement. This has
been verified by
> > testing against multiple implementations.
> >
> > Please be accurate in the statements that you make.
> >
> > Les
> >
> >
> > > -----Original Message-----
> > > From: Lsr <lsr-boun...@ietf.org
<mailto:lsr-boun...@ietf.org>> On Behalf Of Peter Psenak
> > > Sent: Wednesday, August 30, 2023 8:43 AM
> > > To: linchangwang <linchangwang.04...@h3c.com
<mailto:linchangwang.04...@h3c.com>>; Acee Lindem
> > > <acee.i...@gmail.com <mailto:acee.i...@gmail.com>>; lsr
<lsr@ietf.org <mailto:lsr@ietf.org>>
> > > Cc: draft-ppsenak-lsr-igp-unreach-prefix-annou...@ietf.org
<mailto:draft-ppsenak-lsr-igp-unreach-prefix-annou...@ietf.org>
> > > Subject: Re: [Lsr] Working Group Adoption of "IGP Unreachable
Prefix
> > > Announcement" - draft-ppsenak-lsr-igp-unreach-prefix-announce-04
> > >
> > > Changwang,
> > >
> > > On 30/08/2023 08:15, linchangwang wrote:
> > > > Hi WG,
> > > >
> > > > When considering adoption, it's important to take into
account the
> > > > following
> > > drafts as well.
> > > >
> > > > Draft #1 link：https://www.ietf.org/archive/id/draft-wang-
lsr-prefix- <https://www.ietf.org/archive/id/draft-wang-lsr-prefix->
> > > unreachable-annoucement-12.txt
> > > > Draft #2 link：https://www.ietf.org/archive/id/draft-
ppsenak-lsr-igp-
<https://www.ietf.org/archive/id/draft-ppsenak-lsr-igp->
> > > ureach-prefix-announce-04.txt
> > > >
> > > > Reasons are as follows:
> > > >
> > > > 1. The two drafts mentioned above are similar in nature.
> > > > The draft #1 covers more scenarios than the draft #2 as
mentioned
> > > > by
> > > Zhibo Hu mail.
> > > > Therefore, a more in-depth discussion and technical
comparison
> > > > should
> > > take place before any adoption decision is made.
> > > >
> > > > 2. The Draft #1 utilizes the existing mechanisms [RFC7794] and
> > > > [RFC9084] to
> > > indicate reachability by checking whether the originator
information
> > > is
> > > > NULL. On the other hand, the draft #2 introduces a new
flag to
> > > > indicate
> > > reachability.
> > > > From an implementation perspective, it would be easier to
> > develop
> > > > using
> > > the existing RFC mechanisms.
> > > >
> > > > 3. The Draft #1 covers more scenarios and can address the
> > > > aggregation issues
> > > of multiple ABRs.
> > > > However, the Draft #2 explicitly states in Chapter 6
that it does
> > > > not support
> > > this scenario.
> > >
> > > to be more precise, draft #1 talks about more scenarios, it
does not
> > > solves any of them, as these scenarios can not be solved by
what the
> > > draft #1 introduces.
> > >
> > > draft#2 clearly states the fact that these scenarios are not
addressed.
> > >
> > > thanks,
> > > Peter
> > >
> > > >
> > > > 4. If we remove the additional scenarios covered in Draft
#1 and
> > > > compare the
> > > two drafts, the only remaining difference is the method of
indicating
> > > unreachable prefixes -
> > > > either through a UPA flag or using the originator TLV.
> > > >
> > > >
> > > > Thanks,
> > > > Changwang
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: Lsr [mailto:lsr-boun...@ietf.org
<mailto:lsr-boun...@ietf.org>] On Behalf Of Acee Lindem
> > > > Sent: Thursday, August 24, 2023 3:58 AM
> > > > To: lsr
> > > > Cc: draft-ppsenak-lsr-igp-unreach-prefix-annou...@ietf.org
<mailto:draft-ppsenak-lsr-igp-unreach-prefix-annou...@ietf.org>
> > > > Subject: [Lsr] Working Group Adoption of "IGP Unreachable
Prefix
> > > Announcement" - draft-ppsenak-lsr-igp-unreach-prefix-announce-04
> > > >
> > > > LSR Working Group,
> > > >
> > > > This begins the working group adoption call for “IGP
Unreachable
> > > > Prefix
> > > Announcement” - draft-ppsenak-lsr-igp-unreach-prefix-announce-04.
> > > > Please indicate your support or objection on this list prior to
> > > > September 7th,
> > > 2023.
> > > >
> > > > Thanks,
> > > > Acee
> > > > _______________________________________________
> > > > Lsr mailing list
> > > > Lsr@ietf.org <mailto:Lsr@ietf.org>
> > > > https://www.ietf.org/mailman/listinfo/lsr
<https://www.ietf.org/mailman/listinfo/lsr>
> > > >
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