Subject: [dc] DCREQ Section 4 Outline

From: Linda Dunbar <[email-masked]>
Date: Fri, 6 Jan 2012 22:33:36 +0000

Section 4: "Data Center Characteristics" should at least add the following sub-sections:
	- Types of data centers: homogeneous content provider data centers, multi-tenant data centers (small/medium sized data centers, and mega sized data centers), Network service providers' data centers, etc.  
	Each of them has different characteristics. E.g. homogeneous content provider data center might not address fragmentation issues, but may have other issues.  

	-  A section on how location of load-balancing, firewall, and other middleware boxes determine where VMs/hosts in different segments can be aggregated/exchanged.

	- A section on how applications are instantiated in data center. Applications servers (e.g. Oracle's middleware WebLogicServer) instantiate multiple instances of one application, assign them the IP addresses, and VM/server managers place them onto a server rack. 

	- A section to describe how backend data/storage are separated from the front end service networks.    

Linda

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From: "Ashish Dalela (adalela)" <[email-masked]>
Date: Sat, 7 Jan 2012 09:37:42 +0530

Linda, Please see inline. Thanks, Ashish

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Linda Dunbar
Sent: Saturday, January 07, 2012 4:04 AM
To: [email-masked]
Cc: Ronald Bonica
Subject: [dc] DCREQ Section 4 Outline

Section 4: "Data Center Characteristics" should at least add the
following sub-sections:
	- Types of data centers: homogeneous content provider data
centers, multi-tenant data centers (small/medium sized data centers, and
mega sized data centers), Network service providers' data centers, etc.

[AD] What is the difference between a multi-tenant DC and a NSP's DC?
How about including enterprise datacenters as part of hybrid scenarios?

	Each of them has different characteristics. E.g. homogeneous
content provider data center might not address fragmentation issues, but
may have other issues.  

[AD] Do web/content providers need to have VM's? If not, how does the
scale and mobility problem change for them?

	-  A section on how location of load-balancing, firewall, and
other middleware boxes determine where VMs/hosts in different segments
can be aggregated/exchanged.

[AD] You are talking about a L2-L3 boundary? Or something else? What
happens when the firewall is in the Hypervisor?

	- A section on how applications are instantiated in data center.
Applications servers (e.g. Oracle's middleware WebLogicServer)
instantiate multiple instances of one application, assign them the IP
addresses, and VM/server managers place them onto a server rack. 

[AD] How does that affect what problems we are discussing? E.g. isn't
this a form of orchestration?

	- A section to describe how backend data/storage are separated
from the front end service networks.    

[AD] Isn't this adequately covered by the "Data is Immobile" section?
What additions do you propose?

Linda
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From: Linda Dunbar <[email-masked]>
Date: Mon, 9 Jan 2012 04:30:09 +0000

Ashish, 

Answers to your questions/comments are inserted below: 

Linda

> From: Ashish Dalela (adalela) [mailto:[email-masked]]
> Sent: Friday, January 06, 2012 10:08 PM
> To: Linda Dunbar; [email-masked]
> Cc: Ronald Bonica
> Subject: RE: [dc] DCREQ Section 4 Outline
> 
> 

> scale and mobility problem change for them?

[Linda] VMs allows the same number of physical servers to host much greater number of applications. A Data Center with VMs may not need to face mobility issue if they can re-assign IP addresses when a VM is moved from Loc-A to Loc-B.   A Data Center without VMs could face address mobility issue if they need to instantiated an application with IP address in Subnet-A to a physical server on the rack which was under Subnet-B. 

> happens when the firewall is in the Hypervisor?

[Linda] the issue is that majority of servers (or hypervisors) in Data Center don't support the needed security features. Not many low cost TORs are equipped with the features either.  Under those circumstances, the traffic has to be funneled to the switches/routers where the needed security features can be enforced. 

> this a form of orchestration?

[Linda] Those middleware are a big part of data centers. Instances created by one application server may need to be on a short reach to each other. Network may need to provide input to orchestration system on optimal locations where those instances (VMs) can be placed. 
 
> What additions do you propose?

[Linda] Not really. Most servers are using different network (even different physical ports) to reach the backend data storage. VMs can't be instantiated to a server which is not connected to the backend storage network.

---

From: "Ashish Dalela (adalela)" <[email-masked]>
Date: Mon, 9 Jan 2012 10:31:28 +0530

Hi Linda,

>> A Data Center without VMs could face address mobility issue if they
need to instantiated an application with IP address in Subnet-A to a
physical server on the rack which was under Subnet-B.

So, you are saying there is application mobility without VM mobility?
Yes, that's a possibility where you recreate an application with the
same network address without moving state (i.e. the VM). All
hardware/software failures are going to be recovered in this way,
because you can't move a dead server/VM/application. That's not a small
thing either and related to the reliability problem.

>> Under those circumstances, the traffic has to be funneled to the
switches/routers where the needed security features can be enforced.

I understand the problem. There is also the problem to multi-path. If
everything has to funnel through a firewall which is not placed at the
access, then you are basically breaking multi-paths. Mobility
constraints is only one part of the problem. 

>> Network may need to provide input to orchestration system on optimal
locations where those instances (VMs) can be placed

This is exactly right. This is described in the Cloud orchestration
problem, on why the cloud control plane has to interact with the network
control plane. You might have missed this. 

>> Not really. Most servers are using different network (even different
physical ports) to reach the backend data storage. VMs can't be
instantiated to a server which is not connected to the backend storage
network.

Yeah, this presents a greater number of challenges for SAN than for
Ethernet/TCP/IP networks. But, it falls into the general problem of
determining the VM move decision, which needs to know the network
topology, for a variety of things of which storage is one of them.

Thanks, Ashish

-----Original Message-----
From: Linda Dunbar [mailto:[email-masked]] 
Sent: Monday, January 09, 2012 10:00 AM
To: Ashish Dalela (adalela); [email-masked]
Cc: Ronald Bonica
Subject: RE: [dc] DCREQ Section 4 Outline

Ashish, 

Linda

> scale and mobility problem change for them?

[Linda] VMs allows the same number of physical servers to host much
greater number of applications. A Data Center with VMs may not need to
face mobility issue if they can re-assign IP addresses when a VM is
moved from Loc-A to Loc-B.   A Data Center without VMs could face
address mobility issue if they need to instantiated an application with
IP address in Subnet-A to a physical server on the rack which was under
Subnet-B. 

> happens when the firewall is in the Hypervisor?

[Linda] the issue is that majority of servers (or hypervisors) in Data
Center don't support the needed security features. Not many low cost
TORs are equipped with the features either.  Under those circumstances,
the traffic has to be funneled to the switches/routers where the needed
security features can be enforced. 

> this a form of orchestration?

[Linda] Those middleware are a big part of data centers. Instances
created by one application server may need to be on a short reach to
each other. Network may need to provide input to orchestration system on
optimal locations where those instances (VMs) can be placed. 
 
> What additions do you propose?

[Linda] Not really. Most servers are using different network (even
different physical ports) to reach the backend data storage. VMs can't
be instantiated to a server which is not connected to the backend
storage network.