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The Virtual Ethernet Port Aggregator Any Port in a Storm By Johan Ragmo, Data Business Development Manager for the Northern Region, Alcatel-Lucent

One of the major innovations in switching technology is that of

the Virtual Ethernet Port Aggregator. The VEPA is designed to reduce the complexities associated with highly virtualised deployments. Here, Johan Ragmo explains how a VEPA can enable true

virtualisation in an open switching environment.

According to Gartner, the number of virtual machines in corporate data centres increased by more than 50% between 2009 and 2010. Despite this, the traditional data centre network is not optimally designed for server and desktop virtualisation. From the now mainstream and widespread adoption of server virtualisation, companies are taking the first steps towards deploying a next-generation data centre switching network, one that is more agile and adaptable to changing needs. Many organisations have not been

able to reap all of the benefits of server virtualisation because virtual machine (VM) movement requires manual intervention to modify network provisioning. Dealing with this is the next step towards a virtualised network infrastructure.

VM movement

When a network is made up of multiple VMs, each consisting of an individual operating system and applications, the VMs communicate with each other and to the outside world using a virtual switch. This virtual switch moves networking into the server realm, bringing with it the need to re-deploy traditional network-based tools and solutions for the virtualised environment. A true data centre fabric will automatically adapt to VM movement to relieve IT of the burden of manually provisioning the network. This way, data centre networks can adapt to the higher bandwidth requirements

of media-rich applications such as video while supporting server and desktop virtualisation. Monitoring inter-VM

communications can be a huge challenge, due to lack of visibility of inter-VM traffic in the network. And as the number of virtual machines on a single server can be scaled from 8-12 VMs today to say 32-64 in the near future, the need to secure virtual machines from external threats becomes a serious consideration.

The solution

One of the key solutions proposed to address some of these challenges is a Virtual Ethernet Port Aggregator. The VEPA is becoming a real alternative to the virtual switch, and is integral to moving the switching fabric for the data centre into the switch, rather than the server. A VEPA effectively takes all

the traffic generated from virtual machines on a server and moves it out to an external network switch. The external network switch in turn provides connectivity between the virtual machines on the same physical server as well as to the rest of the network infrastructure. The VEPA therefore makes all VM

traffic visible to the external network switch. By moving VM switching back into the physical network, a VEPA based approach makes existing network tools and processes work consistently across both virtualised and non-virtualised environments.

Application fluency

To enable VEPA within the switching fabric, the network has to have the concept of Application Fluency to support Virtual Machine motion. The following three pre-requisites within the switching fabric can support applications fluency. A low latency and a lossless Ethernet

data centre fabric to make sure the virtual machine motion is transparent between the switching layer and the application server/virtual machine. Open interworking between the

virtual machine hypervisor and the switching management platform to transparently match the network profile within the switch and the server in terms of switching priority level, security control, VLAN and access control lists. Centralised provisioning and

management to automatically provision the virtual network profile to support the virtual machine movement across the entire data centre switching fabric from a single management platform. A VEPA brings network administrative control back to the network administrator, providing a single point of control for provisioning, monitoring, and troubleshooting. Offloading the network functions from the server to the network switch also has the benefit of freeing up server resources and making them available for applications such as video across the entire enterprise. As a consequence, the VEPA-based

approach has the promise of being able to scale up virtualisation deployments, reduce complexity and cost, and speed up the adoption of virtualisation. With server virtualisation gaining

A VEPA effectively takes all the traffic generated from virtual machines on a server and moves it out to an external network switch.

40 NETCOMMS europe Volume II, Issue 1 2011

broad adoption, complexities of switching traffic between virtual machines both within a server and across servers are increasing. A VEPA based approach to inter-VM switching provides a compelling alternative to the traditional virtual-switch based approach. Standards efforts are now underway to provide the capabilities needed in the network and server infrastructure to support VEPA.

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