Re: [Lsr] Warren Kumari's No Record on draft-ietf-lsr-ospf-prefix-originator-09: (with COMMENT)

Aijun Wang <wangaijun@tsinghua.org.cn> Thu, 01 April 2021 01:20 UTC

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From: "Aijun Wang" <wangaijun@tsinghua.org.cn>
To: "'Warren Kumari'" <warren@kumari.net>, "'Ketan Talaulikar \(ketant\)'" <ketant@cisco.com>
Cc: "'Christian Hopps'" <chopps@chopps.org>, <aretana.ietf@gmail.com>, <lsr-chairs@ietf.org>, "'The IESG'" <iesg@ietf.org>, <lsr@ietf.org>, <draft-ietf-lsr-ospf-prefix-originator@ietf.org>
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Date: Thu, 1 Apr 2021 09:20:17 +0800
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Subject: Re: [Lsr] Warren Kumari's No Record on draft-ietf-lsr-ospf-prefix-originator-09: (with COMMENT)
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Hi, Warren and Ketan:

 

As the co-author of this draft, I recommended to use “A received Prefix Source Router Address Sub-TLV that has an invalid length (i.e. not consistent with the prefix's address family) MUST be considered invalid and ignored”. or just remove it as Warren’s suggestion.

 

 

Best Regards

 

Aijun Wang

China Telecom

 

From: lsr-bounces@ietf.org <lsr-bounces@ietf.org> On Behalf Of Warren Kumari
Sent: Thursday, April 1, 2021 4:32 AM
To: Ketan Talaulikar (ketant) <ketant@cisco.com>
Cc: Christian Hopps <chopps@chopps.org>rg>; aretana.ietf@gmail.com; lsr-chairs@ietf.org; The IESG <iesg@ietf.org>rg>; lsr@ietf.org; draft-ietf-lsr-ospf-prefix-originator@ietf.org
Subject: Re: [Lsr] Warren Kumari's No Record on draft-ietf-lsr-ospf-prefix-originator-09: (with COMMENT)

 

... and apparently I'd lied to you, both in the Ballot itself, and also in this thread. I'd said that I had balloted NoObjection, but apparently  I'd hit No Comment instead. I'm fixing it now; mentioning just for the record...

W

 

On Wed, Mar 31, 2021 at 4:29 PM Warren Kumari <warren@kumari.net <mailto:warren@kumari.net> > wrote:

 

 

On Wed, Mar 31, 2021 at 2:46 AM Ketan Talaulikar (ketant) <ketant@cisco.com <mailto:ketant@cisco.com> > wrote:

Hi Warren,

Thanks for your review and please check inline below. Will look forward to your inputs on how best to incorporate them in the draft.

-----Original Message-----
From: Warren Kumari via Datatracker <noreply@ietf.org <mailto:noreply@ietf.org> > 
Sent: 31 March 2021 00:53
To: The IESG <iesg@ietf.org <mailto:iesg@ietf.org> >
Cc: draft-ietf-lsr-ospf-prefix-originator@ietf.org <mailto:draft-ietf-lsr-ospf-prefix-originator@ietf.org> ; lsr-chairs@ietf.org <mailto:lsr-chairs@ietf.org> ; lsr@ietf.org <mailto:lsr@ietf.org> ; Christian Hopps <chopps@chopps.org <mailto:chopps@chopps.org> >; aretana.ietf@gmail.com <mailto:aretana.ietf@gmail.com> ; chopps@chopps.org <mailto:chopps@chopps.org> 
Subject: Warren Kumari's No Record on draft-ietf-lsr-ospf-prefix-originator-09: (with COMMENT)

Warren Kumari has entered the following ballot position for
draft-ietf-lsr-ospf-prefix-originator-09: No Record

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The document, along with other ballot positions, can be found here:
https://datatracker.ietf.org/doc/draft-ietf-lsr-ospf-prefix-originator/



----------------------------------------------------------------------
COMMENT:
----------------------------------------------------------------------

I'm balloting No Objection, but I really would like a response...

1: I'm assuming I'm just missing something obvious here, but Section 2.2 sayeth:
"A received Prefix Source Router Address Sub-TLV that has an invalid length (i.e. not consistent with the prefix's address family) or a Router Address containing an invalid IPv4 or IPv6 address (dependent on address family of the associated prefix) MUST be considered invalid and ignored. "

What is an "invalid IPv4" address here? If the length is 4, and the route address is 00000001 or 0xc0a80001, how do you know that that's not what I'm using? Again, I suspect that there is something obvious that I'm missing here...
[KT] I did some digging around and was not really able to find a good reference to what would be "invalid IPv4" in this context. 0x00000001 would be invalid but 0xc0a80001 would be valid. A multicast or ClassE or 0xffffffff would also be invalid. Basically, any address that cannot be used as Router Address (i.e. https://tools.ietf.org/html/rfc3630#section-2.4.1) would be invalid. Not sure if we should just remove the "invalid" part here or to attempt to go about specifying it.

 

I'd suggest just removing it -- trying to specify what "invalid" means in this case will likely lead to madness. If you really want to keep it, I'd suggest just saying something along the lines of "A received Prefix Source Router Address Sub-TLV that has an invalid length (i.e. not consistent with the prefix's address family) or a Router Address containing any address that cannot be used as Router Address (i.e. https://tools.ietf.org/html/rfc3630#section-2.4.1) MUST be considered invalid and ignored." If it were me, I'd just delete the last bit, and back away slowly.... Actually, I'm not even sure that ignoring it *is* the right answer. If I look through $whatever and see a Router Address of 0xffffffff, it is "meaningless", but possibly it is evidence that something, somewhere, is horribly borked, and I should probably go investigate. 

 

 


2: This presumable has the side effect of increasing the size of the lsdb, possibly by a fairly large margin. It seems like it would have been nice to include an operational considerations section noting this, and, while you are at it, that this document will significantly aid in debugging....
[KT] Almost all of the protocol extensions do result in increase of the LSDB size. However, depending on the use-case, these extensions may be used for select prefixes (e.g. the leaf networks to which traffic/service flows are destined to). The Sec 3 does have the following text that touches upon mitigation for this scaling part:

   Implementations MAY support the selection of specific prefixes for
   which the originating node information needs to be included with
   their prefix advertisements.

   Implementations MAY provide control on ABRs to selectively disable
   the propagation of the originating node information across area
   boundaries.

 

Noted (and that all extensions do increase the LSDB size) -- this extension is *possibly* different in that it seems that it has larger scope. Whatever the case, a simple "This may provide information hiding, and also limit the increase of the LSDB size" or "Consideration should be given to the operational impact of the increase in LSDB size" somewhere would make me a happy bunny. Note that my ballot is a NoObjection (non-blocking), and I will not be overly sad if you ignore this... 

 

 


[KT] Regarding the debugging part - I agree. Should we add an operational considerations section here or just include this aspect in the introduction within the following text?

   The primary use case for the extensions proposed in this document is
   to be able to identify the originator of a prefix in the network.  In
   cases where multiple prefixes are advertised by a given router, it is
   also useful to be able to associate all these prefixes with a single
   router even when prefixes are advertised outside of the area in which
   they originated.  It also helps to determine when the same prefix is
   being originated by multiple routers across areas.

 

Either. I'd personally like an operational considerations section (hey, I'm an OpsAD, I *always* want an Operational Consideration section :-)), but I'm also fine with this just being stuffed elsewhere in the document. If you**do** add an operational consideration section it would be a perfect place for the above comment :-)

 


Thanks,
Ketan




 

-- 

The computing scientist’s main challenge is not to get confused by the
complexities of his own making. 
  -- E. W. Dijkstra




 

-- 

The computing scientist’s main challenge is not to get confused by the
complexities of his own making. 
  -- E. W. Dijkstra