D-Link DSR-250 Product Manual - Page 44

Unified Services Router User Manual  Auto-Rollover using WAN port  Primary WAN: Selected WAN is the primary link (WAN1/WAN2/WAN3)  Secondary WAN: Selected WAN is the secondary link. Failover Detection Settings: To check connectivity of the primary internet link, one of the following failure detection methods can be selected:  DNS lookup using WAN DNS Servers: DNS Lookup of the DNS Servers of the primary link are used to detect primary WAN connectivity.  DNS lookup using DNS Servers: DNS Lookup of the custom DNS Servers can be specified to check the connectivity of the primary link.  Ping these IP addresses: These IP's will be pinged at regular intervals to check the connectivity of the primary link.  Retry Interval is: The number tells the router how often it should run the above configured failure detection method.  Failover after: This sets the number of retries after which failover is initiated. 3.4.2 Load Balancing This feature allows you to use multiple WAN links (and presumably multiple ISP's) simultaneously. After configuring more than one WAN port, the load balancing option is available to carry traffic over more than one link. Protocol bindings are used to segregate and assign services over one WAN port in order to manage internet flow. The configured failure detection method is used at regular intervals on all configured WAN ports when in Load Balancing mode. DSR currently support three algorithms for Load Balancing: Round Robin: This algorithm is particularly useful when the connection speed of one WAN port greatly differs from another. In this case you can define protocol bindings to route low-latency services (such as VOIP) over the higher-speed link and let low-volume background traffic (such as SMTP) go over the lower speed link. Protocol binding is explained in next section. Spill Over: If Spill Over method is selected, WAN1 acts as a dedicated link till a threshold is reached. After this, WAN2 will be used for new connections. You can configure spill-over mode by using folloing options:  Load Tolerance: It is the percentage of bandwidth after which the router switches to secondary WAN.  Max Bandwidth: This sets the maximum bandwidth tolerable by the primary WAN. If the link bandwidth goes above the load tolerance value of max bandwidth, the router will spill-over the next connections to secondary WAN. For example, if the maximum bandwidth of primary WAN is 1 Kbps and the load tolerance is set to 70. Now every time a new connection is established the bandwidth increases. After a certain number of connections say bandwidth reached 70% of 1Kbps, the new connections will be spilled-over to secondary WAN. The maximum value of load tolerance is 80 and the least is 20. Protocol Bindings: Refer Section 3.4.3 for details 42