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From Murali Reddy <>
Subject Re: [PROPOSAL] region level VPC and guest network spanning multiple zones
Date Wed, 22 Jan 2014 11:50:59 GMT

Please find the FS for this proposal at below link. I will be sending out
a different proposal covering the enhancements called out in the FS.

On 19/12/13 5:54 PM, "Murali Reddy" <> wrote:

>I would like to propose two networking models enhancements for ACS 4.4
>release that will enable building highly available applications. Currently
>VPC in CloudStack is a zone level entity. So tiers with in the VPC are
>confined to the zone to which VPC belongs. For an application deployed in
>current model of VPC failure of the zone is a single point of failure. It
>is desirable to make VPC a region level entity, where tiers in the VPC can
>be created in different zones of the region. When tiers can be created in
>different zones, application hosted in VPC can be architected to be highly
>available masking zone failures by having redundant tiers in different
>zones. While it may be seen as natural extension, there are fundamental
>limitations with VLAN/traditional L2 based networking due to which
>realizing it would be non-trivial or require special solutions [1].
>Overlay networks [2] in the context of SDN & network virtualization
>provides a way to build networks that are abstracted from
>physical/underlay network. An overlay network is typically built with
>tunnels across edge(vSwitch's in hypervisor) and core is plain L3 network.
>With requirement that L3 connectivity across zones and tunnels can be
>established across the zones, an overlay network that spans multiple zones
>is easily realized.
>Given the range of SDN controllers that are integrated with CS, goal of
>this proposal is to leverage advances in SDN & network virtualization
>introduce below generic notions into CS.
>- an advanced zone isolated network that can span multiple zones
>- a region level VPC where tiers belong to different zones.
>I have opened bugs [3],[4] to track these two enhancements. As part of the
>effort I would like to extend the current OVS plug-in (that builds overlay
>network with GRE tunnels) to realise these two use-cases. I have opened
>bug [5] to track this enhancement.
>As long as we establish tunnels across the zones, we can have overlay
>networks that are functional, but would be inefficient in handling
>east-west traffic [6] and BUM traffic. While the problems exist in the
>overlay networks that are confined to a zone as well, they are compounded
>when the network spans multiple zones resulting in high cross-zone
>east-west traffic. I would be sending out a complementary proposal to
>introduce distributed routing and ACL's for east-west traffic and ARP
>localisation that will allow only legitimate cross zone east-west traffic.
>I will send out a functional specification with detailed requirements,
>assumptions, limitation etc once I make progress with these enhancements.
>Please share any feedback and comments.

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