9:21 a.m.
On 30/08/12 23:11, Alon Bar-Lev wrote:
----- Original Message -----
> From: "Livnat Peer" <lpeer(a)redhat.com>
> To: "Alon Bar-Lev" <alonbl(a)redhat.com>
> 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>
>>> 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