Enterprises with mission critical applications are exploring the benefits of disaster recovery sites for their data centers to ensure business continuity. Special network technology is needed to ensure that site failover and failback occurs reliably and predictably. An ideal solution should provide reliable network connections, manage inbound and outbound traffic over multiple WAN links, failover to a secondary data center if all links at the primary data center are down, and eliminate deployment barriers and costs of multi-homing with BGP (Border Gateway Protocol).
Disaster Recovery Using the PowerLink
ProSeries for Site RedundancyA Tool for Business Continuity Overview Enterprises with mission critical applications are exploring the benefits of disaster recovery sites for their data centers to ensure business continuity. Special network technology is needed to ensure that site failover and failback occurs reliably and predictably. The PowerLink ProSeries has the capability to do this and more. The PowerLink ProSeries is the comprehensive solution to:. Provide reliable network connections.. M anage inbound and outbound traffic over multiple WAN links.. Send traffic over the best performing WAN link.. Increase scalability and throughput of WAN connectivity.. Failover to a secondary data center if all links at the primary data center are down.. Eliminate deployment barriers and costs of multi-homing with BGP (Border Gateway Protocol).The Challenge: Maximize site availability using multi-homing and failover to a remote site.High availability and scalability are major concerns for any company providing services accessed by users outside of the company's local network. The Astrocom PowerLink ProSeries solution for WAN load-balancing provides this functionality with the benefit of both cost and performance advantages over BGP (See the white paper PowerLink and Authoritative DNS for more information).Figure 1 details how the PowerLink ProSeries was used in this first application.
. Primary Authoritative DNS for the domain. Provides inbound load-balancing, responding with multiple IP addresses for inbound hosts. Provides inbound failover, directing inbound traffic towards the WAN line that is still up and available in the event of a single WAN line failure.In addition to WAN link redundancy at a single site, the PowerLink solution can also provide site redundancy for mission critical hosted applications should a catastrophic occurrence bring down the entire primary site . The PowerLink ProSeries can simultaneously provide both WAN link high availability and site failover.WAN link redundancy can be achieved by using the Authoritative DNS functionality on the PowerLink ProSeries to direct inbound traffic (such as web, FTP, mail) to the best WAN link at the primary data center. It is a natural next step to extend the features of the PowerLink to allow inbound traffic re-direction to a remote backup site.The Solution: Using multiple PowerLink ProSeries units for multi-homing at each site and failover to a backup site.
Installing a PowerLink at the backup site and adding the backup site's WAN IP addresses to the DNS nameserver registration as additional authoritative nameservers achieves the site failover. The backup PowerLink is configured with IP addresses on its WAN networks for the various inbound hosts, and is given the nameserver addresses on the primary PowerLink (see Figure 2).
The backup PowerLink will then regularly attempt to test DNS resolution to the primary PowerLink's nameserver addresses. As long as the primary PowerLink responds, the backup PowerLink will ignore any DNS resolution queries (which would then try the Primary addresses). If the primary site does not respond, the backup PowerLink will begin responding to queries, giving out its addresses, resulting in inbound user traffic being directed to the backup site. The PowerLink at the backup site will continue to monitor the primary site, and will quit responding to queries when the primary site comes back on line.This approach simply requires a change in the DNS registration (adding the backup site addresses as nameservers) and setting up the backup PowerLink. The primary PowerLink is not reconfigured and is not aware of the existence of the backup PowerLink. Each PowerLink responds to queries with addresses pointing to its own respective site. The switchover to the backup site and back to the primary site happens automatically as the Time to Live (TTL) expires in the records at the caching servers and by the fact that the other Authoritative server does not respond to queries.ConclusionFor companies requiring WAN link redundancy and disaster recovery site redundancy for their data centers, the Astrocom PowerLink ProSeries is the simple, integrated, low cost alternative to BGP routing and global server load-balancers.... [download for more]
