On 12/11/2014 04:02 AM, joehuang wrote:
Hello, Russell,

Many thanks for your reply. See inline comments.

-----Original Message-----
From: Russell Bryant [mailto:rbry...@redhat.com]
Sent: Thursday, December 11, 2014 5:22 AM
To: openstack-dev@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 <joehu...@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 
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 
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.

Correct, cells does not cover all of the use cases that cascading aims to address. But it was expressed that the use cases that are not covered may not be cases that we want addressed.

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 
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.

Cells can handle a single API on top of globally distributed DCs. I have spoken with a group that is doing exactly that. But it requires that the API is a trusted part of the OpenStack deployments in those distributed DCs.

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.

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 

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
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: 

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 
[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

OpenStack-dev mailing list

Best Regards

Chaoyi Huang ( joehuang )

OpenStack-dev mailing list

OpenStack-dev mailing list

Reply via email to