A CCESS GATEWAYIntroduction 33Load Balancing and Link FailoverThe NSE supports individual configuration of multiple WANs on an Access Gateway(supported on AG2400, AG5600, and AG5800 hardware). Hotels can use this capability in anumber of ways, including load balancing, failure protection, and subscriber allocation.This section provides use cases and scenarios to help you consider the full advantage of thesecapabilities.Definitions and ConceptsLoad BalancingLoad balancing refers to the general process of balancing user traffic across multiple ISPconnections. All load-balancing appliances, as well as the Nomadix NSE, support loadbalancing.Link AggregationLink aggregation refers to the process of connecting multiple ISP connections to an applianceand having the sum of all of the ISP bandwidth available to be shared across all users.However, one individual connection is limited to the speed of the ISP connection that iscurrently being used. For example, a hotel may aggregate 5 x 1.5Mbps DSL connectionstogether. This means that a total of 7.5Mbps of bandwidth is available to be shared across allusers, but a single user can receive a maximum of 1.5Mbps. All load-balancing appliances, aswell as the Nomadix NSE, support link aggregation. In most cases, link aggregation and loadbalancing is effectively the same thing.Link FailoverLink failover (sometimes referred to ISP redundancy) is the process of providing a second (oroccasionally a third or more) ISP link as a back up to the primary ISP link. In the event that theprimary link fails, all traffic is re-routed to the backup link, until such time as the primary linkbecomes available.Combined Load Balancing and Link FailoverThis is the process where both load balancing and link failover are combined together. Itrepresents the best of both worlds. Where multiple ISP links are used in load balancing mode,in the event that one or more links fail, all traffic is automatically rerouted to the remainingsurviving links. When the failed links recover, new connections are routed toward these untilthe normal balanced configuration is reached.
