BROCADE IP PRIMER

Co ns ol ePwrCC U1 PU 2 PU 3TxActRxActActi ve1 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 6J-F16GCJ-F16GCServerIron 850J-F16GCJ-F16GCJ-F16GCJ-F16GCJ-F16GCCo ns ol ePwrCC U1 PU 2 PU 3TxActRxActActi ve1 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 6J-F16GCJ -F16GCServerIron 850J -F16GCJ-F16GCJ -F16GCJ -F16GCJ-F16GCChapter 5: Load Balancing BasicsHTTP GET image.jpgHTTP GET image.jpg1 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 61 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 61 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 61 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 61 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 61 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 6ImageServersHTTP GET index.htm2 M M S WGETindex.htmWeb ServersAgain, the idea is that the load balancer chooses which server to forward thepacket to based on its Layer 7 data. This process provides for ultimateflexibility.Server Load Balancing (SLB)This is the most common method for load balancing. For SLB to function, all ofthe servers being load balanced must be physically connected to the load balancer,or the network must be engineered in such a way that all traffic going toor coming from the real servers passes through the load balancer. It employsLayer 4 switching or Layer 7 switching to make its decision. Once the decisionis made, the load balancer changes the destination IP address and destinationMAC address of the packet and forwards it to the server it has chosen. Allreturn traffic must travel through the load balancer. This gives the load balancerthe opportunity to intercept the reply, substitute the VIP's IP address andMAC address for the source address fields in the packet, and forward thepacket back to the client.Sourceclient IPclient MACDestinationVIPVIP MAC1 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 61 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 61 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 61 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 61 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 61 2 3 4 5 6 7 8 9 1 0 1 1 12 1 3 14 1 5 1 6Sourceclient IPclient MACDestinationserver IPserver MACDestinationclient IPclient MACSourceVIPVIP MAC2 M M S WDestinationclient IPclient MACSourceserver IPserver MACAs all traffic passes through the load balancer, this also allows the load balancerto make very intelligent decisions based on the number of sessionsbeing processed on each server, the amount of data being passed, etc. SLBacts as a middleman, but it's a middleman that knows its servers intimately.100 Brocade IP Primer