1.       How many Trunk ports can be created ? Will there be any Active-Standby 
concepts will be there ?

2.       Is it possible to configure multiple IP address configured on these 
ports ?

In case IPv6 there can be multiple primary address configured will this be 
supported ?

3.       If required can these ports can be aggregated into single one 
dynamically ?

4.       Will there be requirement to handle Nested tagged packet on such 
interfaces ?

Thanks & Regards,

From: Ian Wells [mailto:ijw.ubu...@cack.org.uk]
Sent: Monday, October 27, 2014 9:45 PM
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] [neutron] [nfv] VM-based VLAN trunking blueprints

On 25 October 2014 15:36, Erik Moe 
<erik....@ericsson.com<mailto:erik....@ericsson.com>> wrote:
Then I tried to just use the trunk network as a plain pipe to the L2-gateway 
and connect to normal Neutron networks. One issue is that the L2-gateway will 
bridge the networks, but the services in the network you bridge to is unaware 
of your existence. This IMO is ok then bridging Neutron network to some remote 
network, but if you have an Neutron VM and want to utilize various resources in 
another Neutron network (since the one you sit on does not have any resources), 
things gets, let’s say non streamlined.

Indeed.  However, non-streamlined is not the end of the world, and I wouldn't 
want to have to tag all VLANs a port is using on the port in advance of using 
it (this works for some use cases, and makes others difficult, particularly if 
you just want a native trunk and are happy for Openstack not to have insight 
into what's going on on the wire).

 Another issue with trunk network is that it puts new requirements on the 
infrastructure. It needs to be able to handle VLAN tagged frames. For a VLAN 
based network it would be QinQ.

Yes, and that's the point of the VLAN trunk spec, where we flag a network as 
passing VLAN tagged packets; if the operator-chosen network implementation 
doesn't support trunks, the API can refuse to make a trunk network.  Without it 
we're still in the situation that on some clouds passing VLANs works and on 
others it doesn't, and that the tenant can't actually tell in advance which 
sort of cloud they're working on.
Trunk networks are a requirement for some use cases independent of the port 
awareness of VLANs.  Based on the maxim, 'make the easy stuff easy and the hard 
stuff possible' we can't just say 'no Neutron network passes VLAN tagged 
packets'.  And even if we did, we're evading a problem that exists with exactly 
one sort of network infrastructure - VLAN tagging for network separation - 
while making it hard to use for all of the many other cases in which it would 
work just fine.

In summary, if we did port-based VLAN knowledge I would want to be able to use 
VLANs without having to use it (in much the same way that I would like, in 
certain circumstances, not to have to use Openstack's address allocation and 
DHCP - it's nice that I can, but I shouldn't be forced to).
My requirements were to have low/no extra cost for VMs using VLAN trunks 
compared to normal ports, no new bottlenecks/single point of failure. Due to 
this and previous issues I implemented the L2 gateway in a distributed fashion 
and since trunk network could not be realized in reality I only had them in the 
model and optimized them away.

Again, this is down to your choice of VLAN tagged networking and/or the OVS ML2 
driver; it doesn't apply to all deployments.

But the L2-gateway + trunk network has a flexible API, what if someone connects 
two VMs to one trunk network, well, hard to optimize away.

That's certainly true, but it wasn't really intended to be optimised away.
Anyway, due to these and other issues, I limited my scope and switched to the 
current trunk port/subport model.

The code that is for review is functional, you can boot a VM with a trunk port 
+ subports (each subport maps to a VLAN). The VM can send/receive VLAN traffic. 
You can add/remove subports on a running VM. You can specify IP address per 
subport and use DHCP to retrieve them etc.

I'm coming to realise that the two solutions address different needs - the VLAN 
port one is much more useful for cases where you know what's going on in the 
network and you want Openstack to help, but it's just not broad enough to solve 
every problem.  It may well be that we want both solutions, in which case we 
just need to agree that 'we shouldn't do trunk networking because VLAN aware 
ports solve this problem' is not a valid argument during spec review.
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