It sounds like you're talking about networks defined to work by SE not by standards. I don't want to argue about this, so perhaps we can agree to disagree.
Thanks, Chris. [as wg-member] "Les Ginsberg (ginsberg)" <ginsb...@cisco.com> writes:
Chris ------Original Message----- From: Christian Hopps <cho...@chopps.org> Sent: Thursday, October 6, 2022 1:36 PM To: Peter Psenak (ppsenak) <ppse...@cisco.com> Cc: Christian Hopps <cho...@chopps.org>; Tony Li <tony...@tony.li>; Les Ginsberg (ginsberg) <ginsb...@cisco.com>; Robert Raszuk <rob...@raszuk.net>; Henk Smit <henk.i...@xs4all.nl>; lsr@ietf.org Subject: Re: [Lsr] New Version Notification for draft-pkaneria-lsr-multi-tlv- 01.txt Peter Psenak <ppsenak=40cisco....@dmarc.ietf.org> writes: > Chris, > > On 06/10/2022 18:34, Christian Hopps wrote: >> Peter Psenak <ppse...@cisco.com> writes: >> >>> Tony, Les, >>> >>> I believe we can all agree that we do not want to change the behavior of >>> existing implementations that support MP-TLVs based on the advertisements of the >>> MP-capability from other routers - it would break existing networks. Even the >>> text in the MP-TLV draft does not suggest that to be the case. >> Are people not looking at the spreadsheet Tony put together? >> Which implicit multi-part TLVs are these "existing implementations" >> advertising that keep getting referred to? Please let's work with real data -- >> the spreadsheet shows a grand total of *0* TLVs that could fall in this >> category. > > then the spreadsheet is incorrect. > > I know of implementation that can send and receive Multi part TLVs for IPv4/IPv6 > (MT) IP Reach, (MT) Extended IS reachability and IS-IS Router CAPABILITY TLV to > start with. Do you know all of the implementations, and all of those that don't? If we could publish that list then we presumably could explore more simple solutions. :) People keep talking about breaking deployed networks, but that assumes there are functional networks with implicit MP-TLVs in them. I am not sure I accept the assertion that these networks are truly functional. AFAICT these networks are *lucky* to be working. There's no document to point at, there's no bit to look at, there's literally nothing to help an operator or their routers know if all the routers correctly receive and process these implicit MP-TLVs. These networks are one network change (even as small as an interface up or down event) away from failing, or may even be failing already but not yet in a noticeable way. This is the case regardless of what type of bit or functionality this document provides.[LES:] I don't agree at all with your characterization. MP-TLVs (explicit or implicit) are not an extension of the protocol - they are completely consistent with the base operation of the protocol. I have always viewed lack of support for MP-TLVs as an implementation limitation - not a gap in the protocol. Until relatively recently, there was no need to send MP-TLVs for neighbors/prefixes and since it is far from trivial to implement MP-TLV support it is understandable why most(all?) implementations did not include such support initially. But this does not mean that the protocol itself lacks the support. Would it have been better if all RFCs were explicit about the possibility of MP-TLVs? Sure - but hindsight is always easier than foresight. And even in those cases where MP-TLV support was explicitly defined, this did not guarantee that all implementations had that support. Vendors make decisions based on business as to how they spend their development budget and I think we are both familiar with decisions to defer support for some aspects of the protocol until a stronger business case arises. Regarding existing networks, MP-TLVs are an aspect of scale and feature support. If your deployment includes many flex-algos or a large number of TE attributes or other features which add to the information needing to be advertised, then MP-TLVs are required. Implementations which do not support MP-TLVs cannot be deployed in such environments - and it isn’t because of interoperability issues - it is because they do not support the scale/features required. As my employer has implementations which do support MP-TLVs, I can say that we do not depend upon luck - but we do depend upon careful planning. We work with our customers to ensure that the design of the network - including the capabilities of the routers deployed - is considered. LesSo while looking for a solution here, I think less weight should be placed on these "lucky networks". I'm not saying we should intentionally break them, but they should also not count as "fully-functional" either. Thanks, Chris. [as wg-member] > > thanks, > Peter >> Thanks, >> Chris. >> >>> I find the discussion about advertising supported capabilities for management >>> purposes in IGPs interesting, but not specific, nor directly related to the >>> MP-TLV draft. Keeping the two separate would make a lot of sense. >>> >>> >>> my 2c, >>> Peter >>> >>> >>> >>> On 05/10/2022 22:18, Tony Li wrote: >>>> Les, >>>> >>>>> On Oct 5, 2022, at 1:14 PM, Les Ginsberg (ginsberg) >>>>> <ginsberg=40cisco....@dmarc.ietf.org >>>>> <mailto:ginsberg=40cisco....@dmarc.ietf.org>> wrote: >>>>> >>>>> */[LES:] It is clear that we have different opinions on this – and there are >>>>> multiple folks on both sides of this discussion./* >>>>> */What I would hope we can agree on is to separate the discussion of adding >>>>> advertisement of “feature supported” from the MP-TLV draft by writing a >>>>> separate draft on this proposal./* >>>>> */This would allow the two pieces of work to progress independently – as they >>>>> should./* >>>>> *//* >>>>> */This makes sense to me since the proposal to advertise feature support is >>>>> clearly not limited to MP-TLV and has no bearing on how MP-TLVs are >>>>> encoded./* >>>>> *//* >>>>> */Can we agree on this?/* >>>> Sorry, I’m not on board with this. The two functions would end up >>>> disconnected, all the way to the field. >>>> T >>>> >> > > _______________________________________________ > Lsr mailing list > Lsr@ietf.org > https://www.ietf.org/mailman/listinfo/lsr
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