Data Center LAN Migration Guide - Juniper Networks

Data Center LAN Migration Guide
Network Challenge and Solutions for Virtual Servers
Server virtualization has introduced a new layer of software to the data center called the hypervisor. This layer
allows multiple dissimilar operating systems, and the applications running within them, to share the server’s physical
resources such as CPU, memory, and I/O using entities called virtual machines (VMs). A Virtual Ethernet Bridge (VEB)
within the physical server switches traffic between the VMs and applications running within the same server, as well
as between VMs and external network resources. Instead of interfacing directly to the physical NICs, the applications
now talk to “virtual ports” on the internal VEB (or vSwitch). This creates virtual network endpoints, each with its own
virtual IP and MAC addresses. Unique to server virtualization, a virtual switch (vSwitch) is a Layer 2 switch with limited
function and security. Physical switches (or pSwitches) like the EX Series Ethernet Switches are actual pieces of
network equipment.
The network design for server virtualization requires an organization to consider the connections between the
vSwitch and the pSwitch, including network functionality such as VLAN tagging and link aggregation (LAG) between
network nodes. As VM to physical server ratios increase, server-based networking becomes more complex and
may require multiple virtual switches, different VLANs, QoS tags, security zones, and more. Adding this amount of
network processing to physical server infrastructures adds a great deal of overhead to their loads. It also requires
more networking functionality to be added into hypervisors. To reduce this overhead and simplify operations, an
alternative approach, strategically, is to use a Virtual Ethernet Port Aggregator (VEPA), where servers remain focused
on application processing, and the hypervisor has visibility into the network, delegating switching tasks to collaborating
physical switches. Networking for a large number of physical and logical servers can be simplified by attaching many of
them to the wide configuration of a single Juniper Virtual Chassis switch. As previously described, EX Series switches,
initially, the EX4200, can be logically combined into a single switch spanning over 400 physical server access ports and
supporting several thousand virtual machines using Virtual Chassis technology.
It is important to note that vSwitches and pSwitches are not competing technologies. The IEEE standards body is
working on solving vSwitch issues within its VEPA standards working group. VEPA proposes to offload all switching
activities from hypervisor-based vSwitches to the actual physical switches. In addition, VEPA proposes to ease
management issues. The IEEE 802.1Qbg (Edge Virtual Bridging) and 802.1Qbh (Bridge Port Extension) VEPA standards
specify how to move networking from virtual servers to dedicated physical Ethernet switches. This will help by
concentrating networking functions into equipment that is purpose-built for tasks, enhancing performance, security,
and management within the data centers. It will also help reduce computing overhead on virtual servers, allowing the
CPU cycles to be spent on application processing as opposed to networking tasks. Offloading switching activities from
hypervisor-based vSwitches will also result in an increase in the supported number of VMs. Most importantly, a ratified
VEPA standard will be universal as opposed to a vendor-specific, proprietary solution. For more information on VEPA,
please see: www.ieee802.org/1/files/public/docs2008/new-congdon-vepa-1108-v01.pdf.
In addition to Virtual Chassis and VEPA-based forwarding, a management application such as Junos Space Virtual
Control allows users to monitor, manage, and control the virtual network environments that support virtualized servers
deployed in the data center. Virtual Control provides a consolidated solution for network administrators to gain end-toend
visibility into, and control over, both virtual and physical networks from a single management screen.
Network Automation and Orchestration
Automation is a crucial tool for running a scalable and resilient data center at all levels. When developing an
automation plan, it often works well to partition functions to be covered by the automation platforms and detail how
these functions map into operations teams and data center domains. Within these boundaries, an open architecture
should be selected that addresses the functions across the respective equipment suppliers’ platforms and maps them
to the appropriate applications. In a multivendor infrastructure, a difference typically exists in the level at which vendor
integration occurs—sometimes integration is possible in a multivendor application, and in other cases the integration
is less complete and some number of each vendor’s specific tools needs to be kept in service to accomplish the
necessary tasks.
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