L3 routed network can support 1. broadcast/multicast 2. VRRP virtual MAC like technology
For example OpenContrail does support both of these in fully L3 routed networks. Regards -Harshad On Tue, Oct 28, 2014 at 4:59 PM, Angus Lees <[email protected]> wrote: > On Tue, 28 Oct 2014 09:07:03 PM Rohit Agarwalla wrote: > > Agreed. The way I'm thinking about this is that tenants shouldn't care > what > > the underlying implementation is - L2 or L3. As long as the connectivity > > requirements are met using the model/API, end users should be fine. The > > data center network design should be an administrators decision based on > > the implementation mechanism that has been configured for OpenStack. > > I don't know anything about Project Calico, but I have been involved with > running a large cloud network previously that made heavy use of L3 > overlays. > > Just because these points weren't raised earlier in this thread: In my > experience, a move to L3 involves losing: > > - broadcast/multicast. It's possible to do L3 multicast/IGMP/etc, but > that's > a whole can of worms - so perhaps best to just say up front that this is a > non-broadcast network. > > - support for other IP protocols. > > - various "L2 games" like virtual MAC addresses, etc that NFV/etc people > like. > > > We gain: > > - the ability to have proper hierarchical addressing underneath (which is a > big one for scaling a single "network"). This itself is a tradeoff > however - > an efficient/strict hierarchical addressing scheme means VMs can't choose > their > own IP addresses, and VM migration is messy/limited/impossible. > > - hardware support for dynamic L3 routing is generally universal, through a > small set of mostly-standard protocols (BGP, ISIS, etc). > > - can play various "L3 games" like BGP/anycast, which is super useful for > geographically diverse services. > > > It's certainly a useful tradeoff for many use cases. Users lose some > generality in return for more powerful cooperation with the provider around > particular features, so I sort of think of it like a step halfway up the > IaaS- > >PaaS stack - except for networking. > > - Gus > > > Thanks > > Rohit > > > > From: Kevin Benton <[email protected]<mailto:[email protected]>> > > Reply-To: "OpenStack Development Mailing List (not for usage questions)" > > <[email protected]<mailto: > [email protected] > > >> Date: Tuesday, October 28, 2014 1:01 PM > > To: "OpenStack Development Mailing List (not for usage questions)" > > <[email protected]<mailto: > [email protected] > > >> Subject: Re: [openstack-dev] [neutron][nova] New specs on routed > > networking > > >1. Every packet L3 FIB Lookup : Radix Tree Search, instead of current L2 > > >Hash/Index Lookup ? 2. Will there be Hierarchical network ? How > much > > >of the Routes will be imported from external world ? 3. Will there be > > >Separate routing domain for overlay network ? Or it will be mixed with > > >external/underlay network ? > > These are all implementation specific details. Different deployments and > > network backends can implement them however they want. What we need to > > discuss now is how this model will look to the end-user and API. > > >4. What will be the basic use case of this ? Thinking of L3 switching to > > >support BGP-MPLS L3 VPN Scenario right from compute node ? > > I think the simplest use case is just that a provider doesn't want to > deal > > with extending L2 domains all over their datacenter. > > > > On Tue, Oct 28, 2014 at 12:39 PM, A, Keshava > > <[email protected]<mailto:[email protected]>> wrote: Hi Cory, > > > > Yes that is the basic question I have. > > > > OpenStack cloud is ready to move away from Flat L2 network ? > > > > 1. Every packet L3 FIB Lookup : Radix Tree Search, instead of current L2 > > Hash/Index Lookup ? 2. Will there be Hierarchical network ? How much > > of the Routes will be imported from external world ? 3. Will there be > > Separate routing domain for overlay network ? Or it will be mixed with > > external/underlay network ? 4. What will be the basic use case of this ? > > Thinking of L3 switching to support BGP-MPLS L3 VPN Scenario right from > > compute node ? > > > > Others can give their opinion also. > > > > Thanks & Regards, > > keshava > > > > -----Original Message----- > > From: Cory Benfield > > [mailto:[email protected]<mailto:[email protected] > >] > > Sent: Tuesday, October 28, 2014 10:35 PM > > To: OpenStack Development Mailing List (not for usage questions) > > Subject: Re: [openstack-dev] [neutron][nova] New specs on routed > networking > > > > On Tue, Oct 28, 2014 at 07:44:48, A, Keshava wrote: > > > Hi, > > > > > > Current Open-stack was built as flat network. > > > > > > With the introduction of the L3 lookup (by inserting the routing table > > > in forwarding path) and separate 'VIF Route Type' interface: > > > > > > At what point of time in the packet processing decision will be made > > > to lookup FIB during ? For each packet there will additional FIB > > > lookup ? > > > > > > How about the impact on 'inter compute traffic', processed by DVR ? > > > Here thinking OpenStack cloud as hierarchical network instead of Flat > > > network ? > > > > Keshava, > > > > It's difficult for me to answer in general terms: the proposed specs are > > general enough to allow multiple approaches to building purely-routed > > networks in OpenStack, and they may all have slightly different answers > to > > some of these questions. I can, however, speak about how Project Calico > > intends to apply them. > > > > For Project Calico, the FIB lookup is performed for every packet emitted > by > > a VM and destined for a VM. Each compute host routes all the traffic > > to/from its guests. The DVR approach isn't necessary in this kind of > > network because it essentially already implements one: all packets are > > always routed, and no network node is ever required in the network. > > > > The routed network approach doesn't add any hierarchical nature to an > > OpenStack cloud. The difference between the routed approach and the > > standard OVS approach is that packet processing happens entirely at layer > > 3. Put another way, in Project Calico-based networks a Neutron subnet no > > longer maps to a layer 2 broadcast domain. > > > > I hope that clarifies: please shout if you'd like more detail. > > > > Cory > > > > _______________________________________________ > > OpenStack-dev mailing list > > [email protected]<mailto: > [email protected]> > > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > > > > _______________________________________________ > > OpenStack-dev mailing list > > [email protected]<mailto: > [email protected]> > > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > > > > > > > > -- > > Kevin Benton > > _______________________________________________ > OpenStack-dev mailing list > [email protected] > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev >
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