[openstack-dev] [all] [tc] [PTL] Cascading vs. Cells – summit recap and move forward

joehuang joehuang at huawei.com
Thu Dec 11 09:02:37 UTC 2014

Hello, Russell,

Many thanks for your reply. See inline comments.

-----Original Message-----
From: Russell Bryant [mailto:rbryant at redhat.com] 
Sent: Thursday, December 11, 2014 5:22 AM
To: openstack-dev at lists.openstack.org
Subject: Re: [openstack-dev] [all] [tc] [PTL] Cascading vs. Cells – summit recap and move forward

>> On Fri, Dec 5, 2014 at 8:23 AM, joehuang <joehuang at huawei.com> wrote:
>>> Dear all & TC & PTL,
>>> In the 40 minutes cross-project summit session “Approaches for 
>>> scaling out”[1], almost 100 peoples attended the meeting, and the 
>>> conclusion is that cells can not cover the use cases and 
>>> requirements which the OpenStack cascading solution[2] aim to 
>>> address, the background including use cases and requirements is also 
>>> described in the mail.

>I must admit that this was not the reaction I came away with the discussion with.  
>There was a lot of confusion, and as we started looking closer, many (or perhaps most) 
>people speaking up in the room did not agree that the requirements being stated are 
>things we want to try to satisfy.

[joehuang] Could you pls. confirm your opinion: 1) cells can not cover the use cases and requirements which the OpenStack cascading solution aim to address. 2) Need further discussion whether to satisfy the use cases and requirements.

On 12/05/2014 06:47 PM, joehuang wrote:
>>> Hello, Davanum,
>>> Thanks for your reply.
>>> Cells can't meet the demand for the use cases and requirements described in the mail. 

>You're right that cells doesn't solve all of the requirements you're discussing.  
>Cells addresses scale in a region.  My impression from the summit session 
> and other discussions is that the scale issues addressed by cells are considered 
> a priority, while the "global API" bits are not.

[joehuang] Agree cells is in the first class priority.

>>> 1. Use cases
>>> a). Vodafone use case[4](OpenStack summit speech video from 9'02"
>>> to 12'30" ), establishing globally addressable tenants which result 
>>> in efficient services deployment.

> Keystone has been working on federated identity.  
>That part makes sense, and is already well under way.

[joehuang] The major challenge for VDF use case is cross OpenStack networking for tenants. The tenant's VM/Volume may be allocated in different data centers geographically, but virtual network (L2/L3/FW/VPN/LB) should be built for each tenant automatically and isolated between tenants. Keystone federation can help authorization automation, but the cross OpenStack network automation challenge is still there.
Using prosperity orchestration layer can solve the automation issue, but VDF don't like prosperity API in the north-bound, because no ecosystem is available. And other issues, for example, how to distribute image, also cannot be solved by Keystone federation.

>>> b). Telefonica use case[5], create virtual DC( data center) cross 
>>> multiple physical DCs with seamless experience.

>If we're talking about multiple DCs that are effectively local to each other 
>with high bandwidth and low latency, that's one conversation.  
>My impression is that you want to provide a single OpenStack API on top of 
>globally distributed DCs.  I honestly don't see that as a problem we should 
>be trying to tackle.  I'd rather continue to focus on making OpenStack work
>*really* well split into regions.
> I think some people are trying to use cells in a geographically distributed way, 
> as well.  I'm not sure that's a well understood or supported thing, though.  
> Perhaps the folks working on the new version of cells can comment further.

[joehuang] 1) Splited region way cannot provide cross OpenStack networking automation for tenant. 2) exactly, the motivation for cascading is "single OpenStack API on top of globally distributed DCs". Of course, cascading can also be used for DCs close to each other with high bandwidth and low latency. 3) Folks comment from cells are welcome.

>>> c). ETSI NFV use cases[6], especially use case #1, #2, #3, #5, #6, 
>>> 8#. For NFV cloud, it’s in nature the cloud will be distributed but 
>>> inter-connected in many data centers.

>I'm afraid I don't understand this one.  In many conversations about NFV, I haven't heard this before.

[joehuang] This is the ETSI requirement and use cases specification for NFV. ETSI is the home of the Industry Specification Group for NFV. In Figure 14 (virtualization of EPC) of this document, you can see that the operator's  cloud including many data centers to provide connection service to end user by inter-connected VNFs. The requirements listed in (https://wiki.openstack.org/wiki/TelcoWorkingGroup) is mainly about the requirements from specific VNF(like IMS, SBC, MME, HSS, S/P GW etc) to run over cloud, eg. migrate the traditional telco. APP from prosperity hardware to cloud. Not all NFV requirements have been covered yet. Forgive me there are so many telco terms here.

>>> 2.requirements
>>> a). The operator has multiple sites cloud; each site can use one or 
>>> multiple vendor’s OpenStack distributions.

>Is this a technical problem, or is a business problem of vendors not 
>wanting to support a mixed environment that you're trying to work 
>around with a technical solution?

[joehuang] Pls. refer to VDF use case, the multi-vendor policy has been stated very clearly: 1) Local relationships: Operating Companies also have long standing relationships to their own choice of vendors; 2) Multi-Vendor :Each site can use one or multiple vendors which leads to better use of local resources and capabilities. Technical solution must be provided for multi-vendor integration and verification, It's usually ETSI standard in the past for mobile network. But how to do that in multi-vendor's cloud infrastructure? Cascading provide a way to use OpenStack API as the integration interface. 

>> b). Each site with its own requirements and upgrade schedule while 
>> maintaining standard OpenStack API c). The multi-site cloud must 
>> provide unified resource management with global Open API exposed, for 
>> example create virtual DC cross multiple physical DCs with seamless 
>> experience.

>> Although a prosperity orchestration layer could be developed for the 
>> multi-site cloud, but it's prosperity API in the north bound 
>> interface. The cloud operators want the ecosystem friendly global 
>> open API for the mutli-site cloud for global access.

>I guess the question is, do we see a "global API" as something we want 
>to accomplish.  What you're talking about is huge, and I'm not even sure 
>how you would expect it to work in some cases (like networking).

[joehuang] Yes, the most challenge part is networking. In the PoC, L2 networking cross OpenStack is to leverage the L2 population mechanism.The L2proxy for DC1 in the cascading layer will detect the new VM1(in DC1)'s port is up, and then ML2 L2 population will be activated, the VM1's tunneling endpoint- host IP or L2GW IP in DC1, will be populated to L2proxy for DC2, and L2proxy for DC2 will create a external port in the DC2 Neutron with the VM1's tunneling endpoint- host IP or L2GW IP in DC1. The external port will be attached to the L2GW or only external port created, L2 population(if not L2GW used) inside DC2 can be activated to notify all VMs located in DC2 for the same L2 network. For L3 networking finished in the PoC is to use extra route over GRE to serve local VLAN/VxLAN networks located in different DCs. Of course, other L3 networking method can be developed, for example, through VPN service. There are 4 or 5 BPs talking about edge network gateway to connect OpenStack tenant network to outside network, all these technologies can be leveraged to do cross OpenStack networking for different scenario. To experience the cross OpenStack networking, please try PoC source code: https://github.com/stackforge/tricircle

>In any case, to be as clear as possible, I'm not convinced this is something
>we should be working on.  I'm going to need to see much more 
>overwhelming support for the idea before helping to figure out any further steps.

[joehuang] If you or any other have any doubts, please feel free to ignite a discussion thread. For time difference reason, we (working in China) are not able to join most of IRC meeting, so mail-list is a good way for discussion.

Russell Bryant

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OpenStack-dev at lists.openstack.org

Best Regards

Chaoyi Huang ( joehuang )

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