Open Stack

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.

Thanks
Rohit

From: Kevin Benton <blak111 at gmail.com<mailto:blak111 at gmail.com>>
Reply-To: "OpenStack Development Mailing List (not for usage questions)" <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>
Date: Tuesday, October 28, 2014 1:01 PM
To: "OpenStack Development Mailing List (not for usage questions)" <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>
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 <keshava.a at hp.com<mailto:keshava.a at hp.com>> 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:Cory.Benfield at metaswitch.com<mailto:Cory.Benfield at metaswitch.com>]
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

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--
Kevin Benton
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