Implementation suggestion for LBs to use in Virtual Data Center (VDC)

Virtual Data Center (VDC) uses virtualization technologies in the
data centers. Virtualization platforms like Xen, vmware, HyperV
from Microsoft are used in the VDCs. With increasing number of
subscribers, and many relying on the cloud data centers, there
will be IP address exhaustion for internal servers allocation.

Fortunately, the VDCs with the help of virtualization platforms
can have overlapping IP addresses. The subscribers are given
freedom to choose their own set of IP addresses. In such
setups, the network devices should be programmed such a way
that they identify the server not just by IP address ,its based
on subscriber id too.

Lets take an example. The data center has two subscribers.
There is a load balancer before the real servers. Subscriber A
has VIP1 and the subscriber B has VIP2. But they chose to
have real servers in 10.x.x.x network and chose same IPs
for their real servers.


-------------10.1.1.1(Real 1)
-------------10.1.1.2(Real 2)
VIP1 ------------10.1.1.3(Real 3)

VIP2-------------10.1.1.1(Real 4)
_________10.1.1.2(Real 5
_________10.1.1.3(Real 6)


In the above setup, the load balancer has to distinguish
between real servers based on the subscriber. Traffic
coming to VIP1 must be load balanced between real 1,
real 2 and real 3. While the traffic to VIP2 must be sent
among real 4, real 5 and real 6.

In order to achieve the above setup, the load balancers
must have intelligence to classify the traffic between
subscribers. This can be achieved by allocating a different
vlan id per subscriber. Subscriber A will be allocated a
vlan-a and the other subscriber B should be given a different
vlan, vlan-b. The load balancer after taking a lb decission ,will
tag the packets with respective vlanid. Thus, the packet will
make to its destination.



/--------10.1.1.1(Real 1)
/---------10.1.1.2(Real 2) --vlan a
VIP1 ----------10.1.1.3(Real 3)

VIP2-------------10.1.1.1(Real 4)
\_______10.1.1.2(Real 5) --vlan b
\______10.1.1.3(Real 6)

- Should have different VLANs per subscriber. VLAN will be the
identification parameter for the subscribers.
- LB should be able to take same IP for different real servers and
associate with vlanid
- A different routing table per subscriber. The routing table should
consider vlanid for the route lookups or maintain a different
routing table per subscriber.


The load balancers should implement the above mentioned to
tune to the Virtual Data center and solve future problems.