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

Joe Gordon joe.gordon0 at gmail.com
Fri Dec 12 00:17:20 UTC 2014

On Thu, Dec 11, 2014 at 1:02 AM, joehuang <joehuang at huawei.com> wrote:

> 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.

How would something like flavors work across multiple vendors. The
OpenStack API doesn't have any hard coded names and sizes for flavors. So a
flavor such as m1.tiny may actually be very different vendor to vendor.

> >> 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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> Best Regards
> Chaoyi Huang ( joehuang )
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