> 1) So FV does update its FlowTable Cache from OF Messages going Switch <-> > Controller. But when you say "at most every 30s, means that if it doesn't get > any update it asks the switch for its FlowTable? The FlowMod thing means that > the FlowVisor asks periodically for the switch for modified flows? >
So if no controller or user requests flowtable stats, FV does not store anything in its cache nor does it make any periodic requests. But if your controller asks for the flowtable then if it does not have a copy of the flowtable or if the cache is old, it will fetch the flowtable from the switch. Otherwise it will return the cached values. The reasoning behind this is: 1. There may be many controllers sitting on top of FV, therefore there may be many more flow table requests. 2. On some switch implementations, asking for the flowtable is an expensive operation (ie. forwarding may be delayed) For those two reasons, flowvisor caches the flowtable. Of course, you can change the refresh rate if you know your switches do not suffer from those issues. > 2) If a slice controller wants to install a flow that changes the VLAN tag > from A to B for a given flow, FV only approves it if the slice has Read/Write > permissions on flowspace with dl_vlan=A and dl_vlan=B? That's is correct. > If dl_vlan is wildcarded then everything is allowed, right? Yup that's right as well. > Finally, if its set to NONE it cannot install or mod flows that have (to > have) actions that change Vlan Tags? > And correct again ;) > > Sorry for asking so much but since these particular questions are very > important for our research I would lilke to understand it as accurately as > possible. > No worries, ask as many question as you can. > Thank you very much! > > Victor T. > > > > On 3 September 2013 13:04, Ali Al-Shabibi <ali.al-shab...@stanford.edu> wrote: > Hi Victor, > >> 1) Does FlowVisor updates its FlowDB as OF Messages pass through it? Or does >> it asks directly the switches for their Flow Tables? Reading the source code >> I'm inclined to think of the first option. > > You are mostly right. Flowvisor stores a cache of the flowtable which it > refreshes at most every 30s (this is configurable in versions 1+ of FV). One > important note is that flowmods are not stored when they are pushed down by a > controller, but rather they are periodically read from the datapath. > >> >> 2) I would like to be able to keep a certain controller from installing or >> modding Flows that change the VLAN Tag of a packet, for instance. Can you >> point out a direction to do this? I was investigating the source code, but >> I'm not sure if I should try to implement a new Callback type or something >> like that. > > FV will disallow a controller from pushing or modding a vlan tag if either > that vlan tag is not in the flowspace associated to that controller or if > dl_vlan is set to none. > >> >> If I get to any results I would gladly pull it in the future. >> > > That would be fantastic. Let me know if you need more help. > >> >> Big thanks! >> >> Victor T. >> >> >> On 30 August 2013 18:46, Ali Al-Shabibi <ali.al-shab...@stanford.edu> wrote: >> Hi Victor, >> >> Currently, you cannot specify which openflow actions are allowed on a per >> flowspace basis. This is clearly a desirable feature but unfortunately we >> have not addressed it yet. We would welcome any pull requests/contributions >> in this direction. >> >> Cheers. >> >> -- >> Ali >> >> On Aug 30, 2013, at 11:58 AM, Victor Torres <vit...@poli.ufrj.br> wrote: >> >> > Hello, >> > >> > Does anybody know if it is possible to define allowed/denied actions for >> > slices in FlowVisor? >> > >> > >> > Best regards, >> > >> > Victor T. >> > _______________________________________________ >> > openflow-discuss mailing list >> > openflow-discuss@lists.stanford.edu >> > https://mailman.stanford.edu/mailman/listinfo/openflow-discuss >> >> > _______________________________________________ openflow-discuss mailing list openflow-discuss@lists.stanford.edu https://mailman.stanford.edu/mailman/listinfo/openflow-discuss
