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 -F16GCLoad Balancing MethodsLayer 4 SwitchingWith pure Layer 4 switching, a load balancer looks at the segment header(TCP/UDP). This tells the load balancer which server or groups of servers to forwardthe packet to. For example, you could configure a load balancer to handoff to a group of web servers if the incoming destination port to the VIP is TCP80 (HTTP). You could have the same load balancer forward to a different groupof servers (mail servers) if the incoming destination port is TCP 25 (SMTP).The point of Layer 4 switching is that the decision is based on the destinationport in the Layer 4 header. This will tell the load balancer which actual serversit should be forwarding the packet to.destinationTCP 25destinationTCP 251 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 6destinationTCP 802 M M S WdestinationTCP 80MailServersWeb ServersLayer 7 SwitchingLayer 7 switching is a little more sophisticated. Here, the decision is made bylooking at information in the data portion of the received frame. This is mostcommonly used with web servers, though it could be used with any Layer 7protocol. For example, a client makes a request for the file “index.html.” Theload balancer receives that request, and chooses a specific server. When itreceives the next request asking for the file “sales.html,” the load balancermay be configured to hand that off to another specific server (or pool ofservers).Brocade IP Primer 99