Re: [IPFIX] basicList clarification
Gerald Naveen A <ageraldnaveen@gmail.com> Tue, 15 December 2015 15:04 UTC
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Date: Tue, 15 Dec 2015 20:34:17 +0530
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From: Gerald Naveen A <ageraldnaveen@gmail.com>
To: Paul Aitken <pjaitken@gmail.com>
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Subject: Re: [IPFIX] basicList clarification
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Hi Paul, Thanks for the responses. It clarifies for most part; while I would also like to clarify few things on my question. (tagged [Gerald] inline) So it appears we would need to define Y as IE and mark X as basicList of Y. Thanks again On Tue, Dec 15, 2015 at 6:44 PM, Paul Aitken <pjaitken@gmail.com> wrote: > Gerald, > > Hi all, > > It is my understanding from the RFCs that basicList type is an encoding > for list of IPFIX Information Elements. > > > Yes, where the list contains zero or more instances of a single IE. > > > To create the template much more strongly typed, we have defined a custom > (enterprise) Information Element with a new ID (say X), which is defined as > a basicList of specific items (eg., InterfaceName). > > My question to you all is: Is it mandatory that we have a separate > information element called InterfaceName (say ID Y) and define X as a > basicList of Y ? > > > Yes, that's how the protocol is defined. > > > For our need, it is enough for us, that we define X as a basicList of > string (as X is already strongly defined). But string is a type, not info > element. > > We would like to retain X (instead of defining a template directly with a > standard basicList). And we don't have any other need to define a new > Information Element Y. > > > Y defines the list elements which tells the Collector that the list > contains strings, and it defines the semantics of those strings - eg > whether they contain interface names, user names, a list of selectorNames, > or a list of Application names. Then a basicList of Y tells the Collector > that you're exporting zero or more of them. > [Gerald] This is definitely a choice. However, as I mentioned, this makes the template weakly typed (ie., the element is just #291 basicList). We would like to enforce stronger types at the template itself (this was the motive behind defining X) > > Perhaps you should define Y as a single instance of X (so Y is well > defined), then redefine X as a basicList of Y. Or if you don't want/need to > define both X and Y, then use the basicList IE #291 to export a basicList > of (strongly defined) Y. > [Gerald] Yes, this is also a choice; but we don't need Y for any other reason except to fit into the basicList detail. So wanted to know if that can be avoided. I got my answer: No (if strongly typed templates). > > I realize that the basicList encoding has a information-element ID of the > item in payload -- is this mandatory? > > > Yes. The encoding would not be interoperable without it. > > > Or for a strongly typed item X, we could expect the IPFIX parser to be > aware of contents (interface name) by contract? > > > No. Every collector which implements RFC 6313 (IPFIX Structured Data) > should be able to decode a basicList of Y. However, the mechanism which you > propose requires the collector to have special knowledge of the internals > of X, which is not scalable. In short, such an Exporter would not be > interoperable with all Collectors. > [Gerald] X is not a different encoding. X is a basicList (sort of more strongly typed. ie., X is a basicList of Y). So the encoding is just the same as #291 standard basicList. But when the template declares a element as X, it is clearly typed even without having to look into the data (or it also doesn't let the exporter send X of Z on the same template). > P. > > > Pls let me know if my question is unclear. > > Thanks in advance. > - Gerald Naveen > > > > The custom IE which you've defined must contain meta-data about the list > such as an element count, element lengths, delimiters or separators. It > creates a new way of encoding list information which the collector must > also understand in addtion to the basicList encoding, which is not useful. > In short, you should not create list type elements; instead, use the > basicList mechanism. > [Gerald] Agree. We aren't trying to redefine basicList encoding for sure. > > > > _______________________________________________ > IPFIX mailing listIPFIX@ietf.orghttps://www.ietf.org/mailman/listinfo/ipfix > > >
- [IPFIX] basicList clarification Gerald Naveen A
- Re: [IPFIX] basicList clarification Paul Aitken
- Re: [IPFIX] basicList clarification Gerald Naveen A
- Re: [IPFIX] basicList clarification Paul Aitken
- Re: [IPFIX] basicList clarification Andrew Feren