Web sites with distributed audiences are forced to add additional mirrored locations around the world, for better availability and performance. As a result, a new generation of products has evolved—capable of distributed global load balancing between the different mirrored sites.

At the most basic level, global traffic balancers route traffic between the multiple, geographically dispersed locations, hence making up a distributed web site.

The global traffic balancers typically resolve the domain name into an optimal IP address, after considering several factors:

• Network Health: The network health can be determined using multiple criteria like:

• Network latency: measures the delay in probing local DNS clients from target locations

• Network proximity: measures the number of router hops between the local DNS clients and target locations

• Packet loss: measures the quality of the network connection between the local DNS clients and several target locations.

• Server load: The server load can be determined using multiple criteria like:

1. Server health: is the server up or down?

2. Server metrics: such as the CPU load, I/O load and memory usage.

• Application metrics: Some global load balancers also test specific service loads, such as HTTP, HTTPS and streaming media on the servers.

• Limitations of Product-based Solutions: The solutions in the global traffic management space have tended to focus on a limited part of the overall problem. These solutions are characterized by up-front capital expenditure, complex installation and configuration and IT personnel to support and maintain the boxes. Across the board, these products have not addressed global scalability and availability, nor have they addressed the need for a fully managed and fully out-sourced carrier class service.

• Service-based solutions: A service based solution uses an integrated global traffic management system employed by all of its services. The system uses a global network of traffic directors to route traffic and data collection agents to collect network intelligence. This type of global network can only be economically built, managed and supported by a service provider. Compared to product-based solutions, service-based solutions offer faster ROI, no up-front capital investment, superior availability, better network intelligence and performance, rapid and simplified deployment, and 24x7 management.

Content Delivery Network (CDN)

A CDN improves the download performance of web sites by moving web content to the edge of the Internet, thus closer to the users.

A CDN adds hundreds of caching and streaming servers to the traffic management system. The caching servers store graphical content from the customer’s web site. The traffic director loads balanced web content requests for graphical content among the caching and/or streaming server, using the intelligence gathered by the probes. The traffic directors route the request to the optimal cache located closest to the end-user.

Requirements

The customers evaluate content delivery networks using the following key criteria:

• Performance: CDNs can improve web site downloads by two to ten times. The networks are well suited to deal with flash crowds.

• Availability: CDNs work around network congestion and network failure

• Ease of implementation: Some content delivery solutions take a long time to implement and utilize complex tagging schemes to mark the graphical elements that need to be cached at the edge.

• Content support: The CDN should provide robust and secure support to deliver all types of content.

• Ease of management: The content delivery solutions should enable customers to easily update and manage their content.

• Price: The content delivery vendors should offer discounts to high volume customers.

Availability and performance can be achieved by increasing the number of servers and POPs deployed in the field and/or by using sophisticated traffic management technology to direct traffic within the CDN. Generally, the larger the number of POPs, the better the performance of the CDN. However, a CDN with a more sophisticated traffic management system and fewer POPs can exceed the performance of a CDN that has more POPs, but a less capable traffic management system.

Streaming Delivery Network (SDN)

Streaming is a method of transmitting broadband video, audio and other multimedia files, in "real-time", to a given user over the Internet.

The SDNs are made up of a global network of streaming servers and high capacity storage appliances. The intelligence of the network resides in the global traffic management system that routes requests to the optimal streaming server for the highest performance.

The rapidly increasing demand for streaming media has outstripped the service providers’ ability to deliver a high quality experience that depends on proximity to the end-user and also network congestion, packet loss and server load. Speedera Networks pre-populates all the global edge servers on the network with media content, thus bringing content closest to the viewer, enabling high-quality and real-time delivery of the rich media. Other companies cache the content at the edge servers that increase latency and reduce performance. Data collection agents periodically assess the health and load of the network, in order to maintain 100 percent availability.