Direct-Path Routing is SysMaster's optimal routing technique. It takes advantage of the asymmetrical inbound and outbound Internet traffic. The client to server traffic, flows through SysMaster to the real server. The outbound traffic, which typically consumes more bandwidth, because it contains the requested information, goes directly to the client. By avoiding the SysMaster, Direct-Path Routing provides greater outbound performance and latency improvement.

When network solutions use Direct-Path Routing, SysMaster and all the real servers that provide a given virtual service have an interface configured with the Virtual IP, but only the SysMaster interface is configured to be accessible from the Internet. This way only SysMaster receives the incoming packets and re-routes them to the most available real server. As the real server has an interface with the same IP address, it accepts the packet and processes it. In order for Direct Path Routing to work, SysMaster and the real servers must have a direct physical connection.

When a client sends a request to a service managed by SysMaster, the request packet arrives at SysMaster. The device checks the destination IP and port number of the packet and if they are recognized as the address of one of SysMaster's services, a real server that will process this request is assigned according to the configured loadbalancing technique. SysMaster adds a record for this new connection into its hash table and directly forwards the packet to the chosen server. All subsequent packets for this connection will be sent to the same real server as long as the connection record exists in the hash table. When the server receives the packet, it finds that there is an interface that can take the packet, so the server processes the request. The result of the request is sent directly to the client. When the connection terminates or expires, its record is removed from the hash table.

How it works?

Let us take a closer look at the Direct Path Routing technique:

The real servers in a cluster using the Direct Path routing techniques have at least two IP addresses.

The first is the IP address they use to connect to the network (RIP) and the second is the IP address of the virtual service (VIP) they provide. SysMaster identifies the real servers by their RIP addresses. When SysMaster chooses a real server for a connection, it asks for the MAC address of the server using its RIP address. Then the packet is sent to that MAC address without any changes. When the packet reaches the real server, the service listening on the VIP address recognizes the packet and processes it. The reply is sent directly to the client bypassing the loadbalancer.

Increased Performance and Speed

Using this method, SysMaster can process much more traffic compared to NAT. SysMaster simply changes the destination MAC address of the data packets and retransmits them on the local network. That is why the SysMaster device and the real servers should be connected to one uninterrupted LAN segment.

Another reason for the increased potential of network solutions using the Direct Path Routing technique is the SysMaster processes only the in-bound traffic. The response packets are sent directly to the users and can follow separate network routes bypassing the loadbalancing device. This increases considerably the scalability SysMaster implementations using Direct Path Routing allowing over 100 real servers to be managed by only one device.