Re: [Engine-devel] network subnet

On 30/08/12 23:11, Alon Bar-Lev wrote: > > > ----- Original Message ----- >> From: "Livnat Peer" <lpeer(a)redhat.com&gt; >> To: "Alon Bar-Lev" <alonbl(a)redhat.com&gt; >> Cc: engine-devel(a)ovirt.org >> Sent: Thursday, August 30, 2012 10:16:05 PM >> Subject: Re: [Engine-devel] network subnet >> >> On 30/08/12 21:39, Alon Bar-Lev wrote: >>> >>> >>> ----- Original Message ----- >>>> From: "Livnat Peer" <lpeer(a)redhat.com&gt; >>>> To: engine-devel(a)ovirt.org >>>> Sent: Thursday, August 30, 2012 3:22:29 PM >>>> Subject: [Engine-devel] network subnet >>>> >>>> Hi All, >>>> >>>> Today when a user wants to define a network subnet mask, he does >>>> it >>>> when >>>> he attaches the network to a host NIC. >>>> >>>> I was wondering if there is a reason not to define the network >>>> subnet >>>> on >>>> the logical network entity (Data center level). >>>> >>>> Thanks, Livnat >>> >>> Hello, >>> >>> I am sorry, maybe I do not understand... the IP scheme enforces the >>> use of address mask in order to properly route packets. >> >> of course. My proposal is related to our user usage of the system. >> Today >> ovirt user, who wants to define a network subnet, has to type the >> subnet >> per host (per network), I think the user should only define it once >> on >> the logical network entity in the Data Center. >> Propagating the value to all hosts is needed but it should be our >> internal implementation detail. >> >>> >>> Network mask is used in any case, I guess it can be dropped from >>> configuration in favour of using the address class as mask, is >>> that what you suggest? >>> >> >> No, hope the above paragraph made it more clear. >> > > Hello, > > Then you assume that a logical network, which is actually layer 2 network in our implementation, has layer 3 characteristics, right? > > In our current implementation "data center logical network" is pure layer 2 segment aka layer 2 broadcast domain. > > One can use the same logical network for multiple layer 3 segments, which is totally valid and consistent with standard physical layer 2 setup. > > Unless I am missing something crucial, I would suggest to keep the consistent physical->virtual mapping, unless we emulate layer 3 switching. Layer 2 does not have layer 3 characteristics. > > Regards, > Alon. > Generally I agree with what you wrote. I would like to open for discussion the definition mentioned above that a logical network is a layer 2 broadcast domain. We have 2 types of logical networks, VM networks and 'other' (host functionality?) networks. When talking about VM networks, I think the definition above is accurate, the guests using the network should get a layer 2 broadcast domain. It can be implemented over a single (physical) layer 2 domain or it can be implemented over multiple (physical) layer 2 domains using technologies like tunneling or vxlan. When talking about other networks like storage, display, migration, etc. we are actually discussing a network which represent a common functionality the hosts are using but I am not sure guaranteeing a layer 2 broadcast domain is interesting for such network.

Going forward I expect we'll associate layer 3 services with logical networks. For example DHCP, DNS, LB etc. Any thoughts/comments on the above are welcomed. Thanks, Livnat _______________________________________________ Engine-devel mailing list Engine-devel(a)ovirt.org http://lists.ovirt.org/mailman/listinfo/engine-devel