Special Coverage Series

Network Computing

Special Coverage Series

Commentary

Brent Salisbury
Brent Salisbury

Inside VMware NSX

From VTEPs to OVSDB, VMware's NSX introduces unfamiliar protocols and technologies to the data center network. Check out this overview to get up to speed.

At VMworld 2013, VMware released its much-anticipated NSX network virtualization platform. A growing number of virtual ports have appeared in the data center due to server virtualization, and NSX takes advantage of these virtual switches to create an overlay that runs over the physical network.

NSX uses SDN concepts to implement network virtualization. It uses flow-based forwarding via OpenFlow to instantiate the network flows. Flow forwarding exposes various L2-L4 header fields, along with Layer 1 logical and physical interfaces. Flow forwarding is an important concept because that combination of header attributes describes application traffic, not just two addresses in a network.

More Insights

Webcasts

More >>

White Papers

More >>

Reports

More >>

By unifying business logic and network headers, network control applications can install a simple forwarding policy or complex forwarding and service insertions.

Nested inside of the ESX hypervisor is a virtual switch (vSwitch). The vSwitch can operate as a typical flood-and-learn switch, or attach to the NSX controller. NSX builds tunnels between vSwitches using the VXLAN protocol (among others). These tunnels originate and terminate in VXLAN Tunnel Endpoints (VTEPs).

[VMware lined up an impressive number of partners for its NSX launch--except one. Find out where Cisco and VMware disagree in "Cisco Skips VMware's NSX Coming Out Party."]

A VTEP can be instantiated in servers or in a hardware switch, if it is supported in the switch's firmware and silicon. This creates a data path connecting two data planes over an L2 or L3 network. One vSwitch gives the appearance of being directly connected to another. Each vSwitch is now a VTEP in that particular virtual topology.

Underlying physical ethernet fabric
Source: Brent Salisbury

The overlay approach provides two important benefits for developers.

First, overlays bypass the constraints presented in the native physical network such as VLAN IDs, discontiguous networks or disjointed administrative network domains.

Second, tunnels remove the need for developers to extract and validate all the network paths, health and performance of the underlying network. That is, developers would, without tunnels, have to program applications to go and find out network state of each autonomous network system, which is an impractical requirement.

Flow programming is not a trivial implementation, even if focusing only on the edge. With point-to-point tunnels between every vSwitch, all network elements appears directly connected to one another.

Instead of focusing on each node in the network, network applications can focus on business logic and the task of classifying application traffic--and in turn applying policy. It begins to create a modular environment.

VTEP Edge appears directly connected
Source: Brent Salisbury

The use of VXLAN enables a greater degree of segmentation in the data center network. Traditionally, tenants are segmented from one another using VLAN IDs (VID). However, the 12-bit data structure of the VLAN ID means that a data center network is limited to 4,094 VLANs. By contrast, VXLAN includes a 24-bit VNI (VXLAN Network Identifier), which providers over 16 million available IDs.

Currently most switching hardware is constrained by the VLAN field processor embedded in the silicon. Generally speaking, the current generation of switches can process 250 to 500 VLAN IDs in hardware without affecting performance.

Don't expect hardware vendors to support millions of VXLAN VNIs right way. Vendors are presumably using the same VLAN field processors and silicon resources to process VXLAN as they would VIDs.

NSX Forwarding

In the NSX architecture, a VM boots and the host registers with the NSX controller. The controller consults a table that identifies the tenant and returns the topology the host should participate in to the vSwitch. The key identifier for virtual isolation is the VNI, which maps to a tenant's VXLAN-segmented topology.

Layer 3 forwarding between broadcast domains is supported at the edge of the NSX network in the vSwitch. This is performed by ARPs being punted to the controller and looking up the location of the destination MAC and destination VTEP in a host table in the controller.

If the host is not found, the traffic can be dropped or forwarded to a BUM traffic service node. Host discovery is forwarded to the VTEPs in the tenant tunnel overlay with multicast. VMware says it will soon support unicast, as well. Unicast is always attractive, particularly for interconnects relying on provider networks or the Internet.

Next page: Integrating Overlays

 1 | 2  | Next Page »


Related Reading



Network Computing encourages readers to engage in spirited, healthy debate, including taking us to task. However, Network Computing moderates all comments posted to our site, and reserves the right to modify or remove any content that it determines to be derogatory, offensive, inflammatory, vulgar, irrelevant/off-topic, racist or obvious marketing/SPAM. Network Computing further reserves the right to disable the profile of any commenter participating in said activities.

 
Disqus Tips To upload an avatar photo, first complete your Disqus profile. | Please read our commenting policy.
 

Editor's Choice

Research: 2014 State of Server Technology

Research: 2014 State of Server Technology

Buying power and influence are rapidly shifting to service providers. Where does that leave enterprise IT? Not at the cutting edge, thatís for sure: Only 19% are increasing both the number and capability of servers, budgets are level or down for 60% and just 12% are using new micro technology.
Get full survey results now! »

Vendor Turf Wars

Vendor Turf Wars

The enterprise tech market used to be an orderly place, where vendors had clearly defined markets. No more. Driven both by increasing complexity and Wall Street demands for growth, big vendors are duking it out for primacy -- and refusing to work together for IT's benefit. Must we now pick a side, or is neutrality an option?
Get the Digital Issue »

WEBCAST: Software Defined Networking (SDN) First Steps

WEBCAST: Software Defined Networking (SDN) First Steps


Software defined networking encompasses several emerging technologies that bring programmable interfaces to data center networks and promise to make networks more observable and automated, as well as better suited to the specific needs of large virtualized data centers. Attend this webcast to learn the overall concept of SDN and its benefits, describe the different conceptual approaches to SDN, and examine the various technologies, both proprietary and open source, that are emerging.
Register Today »

Related Content

From Our Sponsor

How Data Center Infrastructure Management Software Improves Planning and Cuts Operational Cost

How Data Center Infrastructure Management Software Improves Planning and Cuts Operational Cost

Business executives are challenging their IT staffs to convert data centers from cost centers into producers of business value. Data centers can make a significant impact to the bottom line by enabling the business to respond more quickly to market demands. This paper demonstrates, through a series of examples, how data center infrastructure management software tools can simplify operational processes, cut costs, and speed up information delivery.

Impact of Hot and Cold Aisle Containment on Data Center Temperature and Efficiency

Impact of Hot and Cold Aisle Containment on Data Center Temperature and Efficiency

Both hot-air and cold-air containment can improve the predictability and efficiency of traditional data center cooling systems. While both approaches minimize the mixing of hot and cold air, there are practical differences in implementation and operation that have significant consequences on work environment conditions, PUE, and economizer mode hours. The choice of hot-aisle containment over cold-aisle containment can save 43% in annual cooling system energy cost, corresponding to a 15% reduction in annualized PUE. This paper examines both methodologies and highlights the reasons why hot-aisle containment emerges as the preferred best practice for new data centers.

Monitoring Physical Threats in the Data Center

Monitoring Physical Threats in the Data Center

Traditional methodologies for monitoring the data center environment are no longer sufficient. With technologies such as blade servers driving up cooling demands and regulations such as Sarbanes-Oxley driving up data security requirements, the physical environment in the data center must be watched more closely. While well understood protocols exist for monitoring physical devices such as UPS systems, computer room air conditioners, and fire suppression systems, there is a class of distributed monitoring points that is often ignored. This paper describes this class of threats, suggests approaches to deploying monitoring devices, and provides best practices in leveraging the collected data to reduce downtime.

Cooling Strategies for Ultra-High Density Racks and Blade Servers

Cooling Strategies for Ultra-High Density Racks and Blade Servers

Rack power of 10 kW per rack or more can result from the deployment of high density information technology equipment such as blade servers. This creates difficult cooling challenges in a data center environment where the industry average rack power consumption is under 2 kW. Five strategies for deploying ultra-high power racks are described, covering practical solutions for both new and existing data centers.

Power and Cooling Capacity Management for Data Centers

Power and Cooling Capacity Management for Data Centers

High density IT equipment stresses the power density capability of modern data centers. Installation and unmanaged proliferation of this equipment can lead to unexpected problems with power and cooling infrastructure including overheating, overloads, and loss of redundancy. The ability to measure and predict power and cooling capability at the rack enclosure level is required to ensure predictable performance and optimize use of the physical infrastructure resource. This paper describes the principles for achieving power and cooling capacity management.