The Elastic Cloud Project - Architecture

This posts is the continuation of The Elastic Cloud Project post.

There is a team at Cisco, called System Development Unit, that creates reference architectures and CVD (Cisco Validated Design).

They work with the product Business Units to define the best way to approach common use cases with the best technology.

But at the time of this project, they hadn’t completed their job yet (some of the products were not even released).

So we had to invent the solution based on our understanding of the end to end architecture and integrate the technologies on the field.

As I explained before, the most important components were:

- servers - Cisco UCS blades and rack mount servers

- network - Cisco ACI fabric, including the APIC software controller

- virtualization - ESXi, Hyper-V, KVM

- cloud and orchestration software - Cisco PSC and CPO, Openstack (PSC and CPO, plus pre-built services, make up Cisco Intelligent Automation - IAC)

IAC can integrate different “element managers” in the datacenter, so that their resources are used to deliver the cloud services (e.g. single VM or Virtual Data Centers - VDC).

Element managers include vmware vCenter and Openstack, so a end user can get a VDC based on one of these platforms.

There is a autometed process in IAC, called CloudSync, that discovers all the resources available in the element managers and allow the admin to select those he wants to use to provision services (resource management and lifecycle management are amongst the features of the product).

The ACI architecture

I will cover it in detail in one of next posts, but essentially ACI (http://www.cisco.com/c/en/us/solutions/data-center-virtualization/application-centric-infrastructure/index.html), that stands for Application Centric Infrastructure, is a holistic architecture with centralized automation and policy-driven application profiles. ACI delivers software flexibility with the scalability of hardware performance. 

Cisco ACI consists of:

• The new Cisco Nexus 9000 Series Switches
• A centralized policy management and Cisco Application Policy Infrastructure Controller (APIC)
• A Cisco Application Virtual Switch (AVS) for the virtual network edge
• Software and hardware innovations
• Integrated physical and virtual infrastructure
• An open ecosystem of network, storage, management, and orchestration vendors
  
  
  

The policies that you create in the software controller (APIC) are enforced by the fabric, including physical and virtual networks.

You describe the behavior your application need from the network, non the configuration you need.

This is easier for the application designer, in the collaboration with network managers, because it can be graphically described by the Application Network Profile.

A profile contains End Point Groups (EPG, representing deployment units of the application: both physical and virtual servers) and Contracts (that define the way EPG can communicate).

A profile can be saved as a XML or JSON document, stored in a repository, participate in the Devops lifecycle, used to clone a environment and managed by any orchestrator.

ACI is integrated with the main virtualization platforms (ESXi, Hyper-V, KVM).

To deploy our 3 tier application on 3 different hypervisors, we had to manage vmware and Openstack separately - but in a single process, because everything should be provisioned with a single click.

Initially we based our custom implementation of the new service on the standard IAC services, using them as building blocks.

So we had not to implement the code to create a network, create a VDC, create a Virtual Server, trigger CloudSync, integrate the virtual network with the hardware fabric.

This sequence of operations was common to the Openstack environment and the vmware environment.

The main workflow was built with two parallel branches, the Openstack branch (creating 2 web servers on one network and 1 application server on anothernetwork) and the vmware branch (doing the same for the database tier).

The problem is that the integration of IAC with Openstack, in the 4.0 release that we used at that time, only deals with Nova - that, in turn, manages both KVM and Hyper-V servers.

No Neutron integration was available out of the box, hence no virtual networks for the Openstack based VDC.

So we built the Neutron integration form scratch (implementing direct REST calls to the Neutron API) to create the networks.

The ACI plugin for Neutron does the rest: it talks to the APIC controller to create the corresponding EPG (End Point Group).

This implementation has been fed back to IAC 4.1 by the Cisco engineering, so in the current release it is available out of the box.

Solution for Openstack

A plugin distributed by Cisco ACI was installed in Openstack Neutron, to allow it to integrate into the APIC controller.

This is transparent to the Openstack user, that goes on working in the usual way: create network, create router, create VM instances.

Instructions are sent by Openstack to APIC, so that the corresponding constructs are deployed in the APIC data model (Application Profiles, End Point Groups, Contracts).

The orchestrator can then use these objects to create a specific application logic, spanning the heterogeneous server farms and allowing networks in KVM to connect to networks in ESXi and Hyper-V.

So the workflow that we built only needed to work with the native API in Openstack.

Logical flow:

— web tier --

create a virtual network for the web tier via Neutron API

     the Neutron plugin for ACI calls - implicitly - the APIC controller and creates a corresponding EPG.

     the Neutron plugin for OVS creates a virtual network in the hypervisor's virtual switch

trigger the CloudSync process, so that the new network is discovered and attached to the VDC

create a VM for the web server and attach it to the network created for the web tier

     this was initially done by reusing the existing IAC service “Provision a new VM"

— application server tier — 

create a virtual network for the app tier via Neutron API

     the Neutron plugin for ACI calls - implicitly - the APIC controller and creates a corresponding EPG.

     the Neutron plugin for OVS creates a virtual network in the hypervisor's virtual switch

trigger the CloudSync process, so that the new network is discovered and attached to the VDC

create a VM for the application server and attach it to the network created for the app tier

     this was initially done by reusing the existing IAC service “Provision a new VM"

— connect the tiers via the controller —  

connect the two EPG with a Contract, that specifies the business rules of the application to be deployed

     this is done via the APIC Controller’s API, creating the Application Profile for the new application in the right Tenant

Solution for vmware

The APIC controller has a direct integration with vmware vCenter, so the integration is slightly different from the Openstack case:

The operations are performed directly against the APIC API and, when you create a EPG there, APIC uses the vCenter integration to create a corresponding virtual network (a Port Group) in the Distributed Virtual Switch.

So we added a branch to the main process to operate on APIC and vCenter, to complete the deployment of the 3 tier application with the database tier. 

Logical flow:

— database server tier — 

call the APIC REST interface, implementing the right sequence (authentication, create Tenant, Bridge Domain, End Point Group, Application Network Profile).

     specifically a EPG for the database tier is created in the APIC data model, and this triggers the creation of a port group in vCenter.

trigger the CloudSync process, so that the new network is discovered and attached to the VDC

create a VM for the database server and attach it to the network created for the app tier

     this was initially done by reusing the existing IAC service “Provision a new VM"

Service Chaining

The communication between End Point Groups can be enriched by adding network services: load balancing, firewalling, etc.

L4-L7 services are managed by APIC by calling external devices, that could be either physical or virtual.

This automation is based on the availability of device packages (set of scripts for the target device), and a protocol (Opflex) has been defined to allow the declarative model supported by ACI being adopted by all 3rd party L4-L7devices. 

Cisco and its partners are working through the IETF and open source community to standardize OpFlex and provide a reference implementation.


In next post, I will describe the methodology we used to integrate the single pieces of the architecture, how we learned to use the API exposed by the target systems (APIC and Openstack) and to insert these calls into the orchestration flow.

Link to next post: The Elastic Cloud Project - Methodology

The Elastic Cloud Project

The Elastic Cloud was a pilot project that I led as a software architect for a customer.

They wanted to evaluate the complexity and the overal quality of a end to end solution provided by Cisco for Cloud Computing.

So we built a complete infrastructure, including hardware and software, for a public cloud.

The number of use case was limited, and I will tell you about the most curious one.

When I was told about the requirement, I thought it didn’t make sense in the real world… but later I understood the rationale  :-)

The request was to deploy a three tier application, with a single click, provisioning also all the needed infrastructure at the same time: (virtual) servers, network and storage.

So this is an example of software defined datacenter, not only SDN but the entire stack: from hardware to the sw application. 

The strange aspect of this requirement is that every tier of the application should run on a different virtualization platform: web servers on KVM, application servers on Hyper-V, database server on ESXi.

It was a technical demonstration, sure, but it also reflected a real world use case. They have some customers that, for legacy applications, have certification constraints that mandate a specific hypervisor for at least one part of the application. So the deployment cannot be standardized on a single platform.

Our customer wanted to verify that Cisco is able to orchestrate a multi vendor infrastructure and that the advantages of stateless computing (I will explain it in a different post, but essentially it is joining SDN with the quality of a hardware infrastructure) are not compromised by the etherogeneity of the virtualization layer.

They said that no other vendor was able to implement the entire use case on the 3 major hypervisors together.

This is a very high level description of the use case:

We decided to implement the self service process in the portal provided by Cisco Prime Service Catalog.

The orchestration layer was Cisco Process Orchestrator, interfacing with Openstack and vmware vCenter directly.

Openstack had compute nodes running KVM and Hyper-V.

Virtual networks were created, on demand, in the virtual switches in each hypervisor and then joined by the physical network connecting the virtualized servers.

The configuration of the network was done through the APIC software controller, that is part of the Cisco ACI architecture (Application Centric Infrastructure).

 

There is a solution, offered by Cisco, that provides cloud services out of the box.

It is called Intelligent Automation for Cloud (IAC) and it is based on the Prime Service Catalog (PSC) as a front end, the Cisco Process Orchestrator (CPO) and prebuilt services created by the Cisco engineering.

IAC integrates your infrastructure by interfacing with vCenter, vCD, Openstack and other so called “element managers” and has all the tools to manage the resources lifecycle.

We decided to reuse some of the existing services as building blocks, wrapping them in a custom process implementing the logic of the specific use case.

So we created a workflow in the visual editor of CPO that invokes the existing atomic services: create a virtual network, create a VDC (virtual data center), create a virtual server.

Then we added explicit calls to the API of the target systems that were not integrated in IAC: the APIC Controller for the ACI fabric, Neutron as the manager of the networking in Openstack (the 4.0 release of IAC only managed Nova for provisioning VMs in Openstack, now also Neutron is integrated in IAC 4.1).

So the effort in this project was only dedicated to understanding the overall logic of the use case and implementing the needed API calls.

It was not particularly difficult, because the target API are all based on a REST interface (both for APIC and Neutron) so invoking them from CPO was a kids’ play.

We created a process with 3 branches, one for each tier of the application, creating all the needed networks and virtual machines, then “plumbing” all together with the ACI fabric through the API of the APIC controller.

We were forerunners, trying to implement a exotic use case before the Business Units looked at it… now everything is available out of the box    ;-)

So we faced the following issues:

• Lack of reference architecture and some products features.
• Dispersed team (time zones and location) made the coordination difficult.
• Fragmented skills: none of us had the complete knowledge of all the products and technologies, due to the amount of innovation involved. 
• Multitasking: many of us were working part time, engaged on different projects.
• Generous support from individuals and organizations in the company, but limited governance
• Products limitations discovered in progress (and solved with... fantasy)
• Usage of beta code and daily builds for some of the products
• Limited documentation available  

In next post I will tell the entire story and how we were able to demonstrate the main concepts:

• Cisco ACI is one of the best solutions for SDN and is not limited to software overlay only
• Cisco has a end to end solution for cloud, including sw and hw and people that can design the architecture
• Open source solutions can be easily integrated into a commercial architecture, providing additional value
• The contribution Cisco provided to Openstack allows customers to manage our network fabric from Neutron seamless

Link to next post: The Elastic Cloud Project - Architecture