Network Virtualization

Network virtualization is the latest buzzword to hit the IT

circles. It's meant to ease the task of managing a large heterogeneous network

by providing you a single point of control. In network virtualization, all

services and servers are treated as a single pool of resources which can be

rearranged and redeployed in real-time to meet changing user requirements. This

would help reduce network complexity, thereby lowering system downtime and

reducing the cost of network management.

A lot of tasks that were done manually by network managers

can be handled automatically after network virtualization. Currently, there's

no predefined standard for this new trend, due to which different vendors have

interpreted it differently. Here, we delve into some of those interpretations.

Virtual IP address 



Virtual IP Address (VIPA) is a technology used in failover and load

balancing of a network connection. It adds a protection layer to a network

connection. It assigns a virtual IP address to an existing interface, so if the

system is unavailable, then the virtual IP address takes over the network

connection and automatically restores the connections between different servers.

VIPA is configured on a TCP/IP stack rather than a physical

adapter, and is therefore not linked with any particular endpoint device. A

virtual IP address is configure designated with multiple paths on the TCP/IP

stack, as a result it automatically switches to alternate path in case of

connection failure.

This eliminates hardware and communication media from

becoming points of failure for many connections. VIPA automatically takes over

and allows a Virtual IP address to automatically move to a stack where an

existing suitable application instance is already active and allows the

application to serve the users.

Further still, you can even configure a Dynamic Virtual IP

Address (DVIPA) for an application server. This can allow applications to create

and activate virtual IP, so that it can switch from one Logical Partitioning (LPAR)

to another one in case of failure. 

Hipersockets 



This is a technology that's specific to IBM's zSeries servers. Instead of
having multiple servers running their own applications for web, database

transactions, application, etc, everything is consolidated into a single zSeries

server and run in a virtual environment.

Prior to consolidation, all servers would have their own

physical network connections and you would need multiple routers and switches to

connect them together.

After consolidation, this external infrastructure of

network cards, cables, switches, and routers is not required. All communication

between the various virtual servers happens inside the zSeries server itself.

There are several advantages to this approach. One, since the zSeries server's

internal bus is used, there's literally zero latency, so the communication

between various virtual machines is much faster.

Since all the network connections are virtual, there can be

automatic failover between them. So if your business application's network

interface fails, it would automatically failover to another virtual connection.

All this leads to a more simplified infrastructure.

Virtual Ethernet 



A virtual Ethernet interface is a fake Ethernet device, which is a replica

of a physical Ethernet device. This will respond like a normal Ethernet for

another IP address than the normal IP address of the physical Ethernet interface

of a machine. Therefore, it can have several IP addresses for single physical

Ethernet interface.

For example, these days Ethernet interfaces come with

integrated VLAN. This allows you to create a virtual LAN on virtual Ethernet

interfaces. This technology is also used to connect branch offices to their

corporate office.

Nortel's virtual Ethernet solution allows organizations to

cost-effectively scale and transparently extend their Ethernet LANs across a

wide area network (WAN), making the WAN and LAN appear as a single Ethernet

network.

As you can see, there are several interpretations of

network virtualization, largely due to a lack of open standards. It therefore

becomes quite difficult to determine what to choose. Some work is happening on

this front, and hopefully we should have something very soon.

Virtual LAN



This is another network virtualization technology, which acts like a normal

LAN and devices connected on it can be segregated into groups of different

logical LAN networks. However, all the devices are connected physically on a

same segment.

This allows administrator to divide LAN into virtual

segment without using a separate switch.  Here, clients and servers may be

placed anywhere on a network, but they are grouped together using VLAN

technology. This also prevents broadcast traffic as it sends broadcast data to

devices within the VLAN. 

VLANs are configured using Media Access Control (MAC)

addresses of the device. If a device is moved from one port to another on the

switch, the VLAN management software recognizes it and automatically

reconfigures it into its appropriate VLAN without changing the MAC address or

the IP address of the node.

It uses 802.1Q specification method for adding VLAN group

information into ethernet frames. Some VLAN softwares not only manage all the

VLAN groups but also allow you to create virtual routers with in the VLANs. So

that you can interconnect different VLANs together.

For example, the   various servers and clients

can be  added to separate groups which in turn can communicate with each

other through virtual routers. This technology is now available with all managed

switches.

Virtual Private Network  



This is another virtualization technology, which allows you to interconnect

your branch offices over a public network, with your existing infrastructure. A

VPN ensures that data that is sent between the two endpoints of a connection

remains secure.

In this setup, people outside your network can be part of

your network from a public network such as Internet and one can access any

service running on your network from anywhere.

These days VPN appliances are available, which connect you

to  a corporate network via public IP and the users can access that network

by logging in using a VPN client. It may be slow for the client depending on the

connectivity speed, but the client can avail all the services from the corporate

network.

Sanjay Majumder