DSR 구성을 통한 네트워크 아웃바운드 트래픽 감소

Reducing outbound traffic by using DSR configuration

Let's look at how to reduce outbound traffic by configuration DSR, Direct Server Return.

Popular websites generally face massive traffic on daily bases, so it's well known fact that they are using DSR.

Packet flow for ordinary setup vs the flow for DSR setup

The biggest difference is the name itself, Direct Server Return !!

The notable difference is the position of L4 Switch. The L4 switch is directly connected to the upper switch on DSR. And the packet flow is significantly different. While the inbound packet and outbound packet get through the L4 switch all together, but on DSR, only the incoming packet goes by the L4 switch and the other doesn't. That's why it's called Direct Server Return.

Advantage of DSR

In most cases, there'll be much higher traffic on response than request in web server, although it depends on the service tendency. If inbound traffic needs 50Mbps and outbound traffic takes up 140Mbps in L4 switch with 100BASE-T capability, there will be another 50Mbps left for the inbound traffic, but outbound will be short of 40Mbps. It's time to consider upgrading the switch unto 1000BASE-T.

But you can balance those two traffic type by configuration DSR. L4 switch availability for request traffic can be increased by dropping outbound traffic itself to the inbound level. Moreover, It's very cost efficient to use just one L4 switch port, which is very expensive, and DSR makes your network topology simpler and fault-tolerance because you can configure L4 switch to anywhere and as a result, the advantage of distributed loading can be obtained.