>From reading various docs, at some point (a few months ago) it did occur to me that lookups are implemented similar to CAM lookups... Not sure why I forgot that since then :( In any case, thanks for humoring me so far... :)
BTW, I have seen ASICs that use hash tables (with indices) for FDB tables.... For L3 I am aware of ASICs with TCAMs... With L3 there could be issues such as low TCAM space and having to move bulk of entries to make room for more specific/longer matches... Naturally wondering how CAM like lookups scale in software... Time to go dig deeper into the code... In any case, now I see why it did not make sense to you :) Given how lookups are implemented, now it does not make sense to me either :) Thanks... On Tue, Jan 6, 2015 at 3:01 PM, Ben Pfaff <[email protected]> wrote: > The OVS datapath extracts the packet headers then looks for a match in > its flow table. What part of that is the "flow index"? > > On Tue, Jan 06, 2015 at 02:01:51PM -0800, Ashok Chippa wrote: > > Okay. How does the OVS datapath know this is a new flow? i.e. there is no > > matching flow entry? Doesn't it derive some sort of an index (into the > flow > > table) from packet header fields? What am I missing? :) > > > > If this is explained in details somewhere, I would appreciate the > pointer. > > > > Thanks, > > ashok > > > > On Tue, Jan 6, 2015 at 1:43 PM, Ben Pfaff <[email protected]> wrote: > > > > > On Tue, Jan 06, 2015 at 11:01:08AM -0800, Ashok Chippa wrote: > > > > Perhaps once you understand, it will make sense? :) > > > > > > > > Call it whatever flow_id or cookie or xyz? Let me call it "flow > index" > > > for > > > > the sake of this discussion. The ovs datapath has some sort of a flow > > > index > > > > to look into the flow table when a packet arrives, right? Now, how > does > > > the > > > > ovs datapath arrive at this flow index (upon a packet arrival)? It > takes > > > > certain match parameters (from the packet header and perhaps some > > > > metadata) and hashes them, right? > > > > > > I don't think you understand how the OVS datapath works. > > > >
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