Hi Les, What you call "an application" is simply counter intuitive and not what 99.9% of people understand by this term. Application to me is a web server running on the host waiting for user requests, SIP gateway providing VoIP connections, database instance running on some specific port and responding to SQL queries, multicast streaming etc ...
Each of these real applications may benefit from different network transport/forwarding class. Calling a network forwarding class as "an application" only generates huge confusion. Networks are servants to the user applications. Networks are not the applications itself. As each user application may benefit from different treatment it can be mapped to different network transport or network color. So again network color could be seen as a network behaviour constructed in an optimal way to the user application it is designed to carry. When you say "You also can – using the algo specific FAD – specify which colors are to be used by a given algo." to me means that you are also overloading the term "color" - at least from the notion of how CAR or CT proposal are defining it. And what CAR/CT proposals call a transport color is actually in line with network forwarding class and very intuitive. As you recall a few months back I defined an IP TE solution where we can steer packets between nodes without any stack of labels or segments imposed on them upfront on ingress. That would be in your terminology new application - as it does not use SPF, but constructs end to end waypoints using its own heuristic. Then when someone would like to reuse link metrics already advertised for flex-algo it would need to touch all the links in the network to add this new app. And this would continue every time someone invents a new network forwarding model while reusing physical metrics already advertised with each link. You mentioned that one of the reasons was to clearly separate RSVP-TE from SR running on a link. But as we discussed you could do that with the "include" notion using affinity bits - not with separate R vs S bits. So while I doubt that you will adjust the terminology used in flex-algo draft I continue to believe that there is value with advertising link attributes which can be used by any current and future network forwarding class or color. Best, Robert. On Sat, Mar 26, 2022 at 10:27 PM Les Ginsberg (ginsberg) <ginsberg= 40cisco....@dmarc.ietf.org> wrote: > Robert – > > > > The defined set of APPs can be seen here > <https://www.iana.org/assignments/igp-parameters/igp-parameters.xhtml#link-attribute-application-identifiers> > : > > > > Bit Name Reference > > 0 RSVP-TE (R-bit) [RFC8919] > > 1 Segment Routing Policy (S-bit) [RFC8919] > > 2 Loop Free Alternate (F-bit) [RFC8919] > > > > Note one additional APP – Flex-Algo – is not yet reflected in this > registry. > > > > Now, you can advertise delay and extended admin groups (EAG) for Flex-Algo. > > You also can – using the algo specific FAD – specify which colors are to > be used by a given algo. > > > > I don’t know of any SPF algorithm that supports specifying a range of > metric values as part of its constraints. It is possible to advertise a > number of user defined metrics using the Generic Metric sub-TLV defined in > https://datatracker.ietf.org/doc/draft-ietf-lsr-flex-algo-bw-con/ and use > the algo specific FAD to specify which of those metrics is to be used for > that algo. But in doing so, the App associated with each of the Generic > Metric advertisements will be Flex-Algo. > > > > Les > > > > *From:* Robert Raszuk <rob...@raszuk.net> > *Sent:* Saturday, March 26, 2022 9:10 AM > *To:* Les Ginsberg (ginsberg) <ginsb...@cisco.com> > *Cc:* Christian Hopps <cho...@chopps.org>; Shraddha Hegde < > shrad...@juniper.net>; Martin Horneffer <m...@lab.dtag.de>; lsr < > lsr@ietf.org> > *Subject:* Re: New Subject: Is Flex-Algo One App or Many (was “RE: [Lsr] > IETF13: Comments on The Application Specific Link Attribute (ASLA) Any > Application Bit”) > > > > Les, > > > > To me what corresponds to network application is effectively a forwarding > paradigm/topology build and used to forward corresponding traffic classe. > You can overload application name the way you like but it does not change > anything. > > > > So if this is going to make you more happy let's rename my > example accordingly and let's not get hang out on flex-algo name itself. > > > > Example: > > > > link attribute: delay > > > > applications: > > > > app_1 - build topology using SPF_algo_1 where max delay does not exceed 10 > ms - color: premium best effort > > app_2 - build topology using SPF_algo_2 where max delay does not exceed 8 > ms - color: black > > app_3 - build topology using SPF_algo_3 where max delay does not exceed 6 > ms - color: bronze > > app_4 - build topology using SPF_algo_4 where max delay does not exceed 4 > ms - color: blue > > app_5 - build topology using SPF_algo_5 where max delay does not exceed 3 > ms - color: silver > > app_6 - build topology using SPF_algo_6 where max delay does not exceed 1 > ms - color: gold > > > > etc ... > > > > Now tell me how does it make sense to enable each app on the link delay > attribute ? > > > > Thx, > > R. > > > > > > On Sat, Mar 26, 2022 at 4:56 PM Les Ginsberg (ginsberg) < > ginsb...@cisco.com> wrote: > > Robert – > > > > I changed the subject – because what you are talking about has nothing to > do w the discussion of ANY bit. > > > > You have mentioned this before – and been corrected before – but it seems > that did not alter your thinking. > > > > Flex-Algo is ONE APP. > > There is not a bit in the SABM assigned per algo – nor is there any intent > to do so. > > Nor does ANY bit introduce the notion of one bit per algo. > > > > All link attributes advertised with the Flex-Algo (X-bit) in the SABM are > usable by any algo. Same would be true if you used ALL encoding. Same would > be true if you used ANY encoding. > > Which ones are used and how they are used (e.g., which affinity bits apply > to a given algorithm) is determined by the Algorithm Specific FAD. > > > > Either you don’t understand Flex-Algo – or you do understand it and want > to do a major rewrite of it – I am not sure which. > > But either way, none of this has anything to do with the original thread. > > > > Les > > > > *From:* Robert Raszuk <rob...@raszuk.net> > *Sent:* Saturday, March 26, 2022 3:43 AM > *To:* Christian Hopps <cho...@chopps.org> > *Cc:* Les Ginsberg (ginsberg) <ginsb...@cisco.com>; Shraddha Hegde < > shrad...@juniper.net>; Martin Horneffer <m...@lab.dtag.de>; lsr < > lsr@ietf.org> > *Subject:* Re: [Lsr] IETF13: Comments on The Application Specific Link > Attribute (ASLA) Any Application Bit > > > > Hi Chris, > > > > It seems that there is a subtle but important element on which we may have > different opinion. > > > > You said: "has to deploy new software that contains the new Wizbang > feature, right?" > > > > IMO however we are dealing with case where software already supports all > required functions on a box. It is just not using it from day one. You buy > a router with OS features which allow you to build zoo of different > forwarding paradigms. > > > > Say day one you see a need to enable flex-algo_1 You enable day one links > to distribute link attributes required for this. > > > > Day two you want to define new FAD and flood this enabling new > flex-algo_2. You reuse already present link attributes entirely or > partially in flex-algo_2 computation. You do not need to touch 100000s of > links each time you enable new flex_algo. > > > > That's a selling point to me. > > > > If we would expect that folks will limit flex-algo to just a few maybe > this all does not matter. But if we see proposals with rainbow of colors > each mapped to different flex-algo and perhaps subtle forwarding difference > (same metric but just a different min threshold per each flex-algo) it > seems pretty bad idea to explicitly enable each app each time such new > threshold used to build different topology. > > > > Example: > > > > link attribute: delay > > > > applications: > > > > flex-algo_1 - build topology where max delay does not exceed 10 ms - > color: premium best effort > > flex-algo_2 - build topology where max delay does not exceed 8 ms - > color: black > > flex-algo_3 - build topology where max delay does not exceed 6 ms - color: > bronze > > flex-algo_4 - build topology where max delay does not exceed 4 ms - color: > blue > > flex-algo_5 - build topology where max delay does not exceed 3 ms - color: > silver > > flex-algo_6 - build topology where max delay does not exceed 3 ms - color: > gold > > > > etc ... > > > > Now tell me how does it make sense to enable each app on the link delay > attribute ? > > > > Cheers, > > Robert > > > > > > > > On Sat, Mar 26, 2022 at 6:42 AM Christian Hopps <cho...@chopps.org> wrote: > > > Robert Raszuk <rob...@raszuk.net> writes: > > > Les, > > > > I don't think this is noise. > > > > Your examples are missing key operational consideration .. Link > > attribute applicable to ANY application may be advertised well ahead > > of enabling such application in a network. > > > > So requesting operator to always advertise tuple of app + attr is not > > looking forward and makes unnecessary operational burden. > > [as wg-member] > > Hi Robert, > > Originally this was the argument that sort of put wind in the sails (for > me) for this any bit, but some more thinking about how things would really > work changed my mind. > > In order for some new feature, let's call it Wizbang, to take advantage of > existing any bit marked attributes, the operator still has to deploy new > software that contains the new Wizbang feature, right? So the addition of a > new Wizbang bit pretty much comes free for the operator. > > So, this draft really is just about making the encoding a bit more > efficient. > > I think if we were defining a new encoding, having this functionality > makes sense, but we aren't defining a new encoding. The proposal is to > change an existing published encoding, and the bar has to be higher for > that I think. > > Thanks, > Chris. > [as wg member] > > > > > > Thx. > > R. > > > > _______________________________________________ > Lsr mailing list > Lsr@ietf.org > https://www.ietf.org/mailman/listinfo/lsr >
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