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How a host does this internally when a client sends traffic
for configured port rule
Let’s take an example: A client running Windows 2000 or
XP open up a browser and type the www.csc.com.
1. Request is forwarded to the
cluster IP Address (10.0.0.1).
2. Cluster receives the traffic at
Network Layer where the NLB driver service sits and watches for an incoming
packet.
3. All hosts simultaneously
receive this packet and look in its statistical mapping to see if the traffic is
covered in the port rules defined or not.
4. If traffic is covered in the
port rule then it checks whether this host has already served or not. The Flag
column indicates the status of host whether this host served the last traffic or
not. The Flag will be incremented by 1 if this host had served the last traffic.
For example: if Host 1 receives the traffic, it will serve the client and then
increment the Flag by 1.
5. In this example, Host 1
receives the packet/traffic and other hosts discard the packet.
6. If the traffic is not covered
by the port rule then the only host will receive the traffic which has been
designated as the Default Host. This is identified by the Host ID in
statistical mapping.
7. After Host 1 has served the
request the statistical mapping on that host will look like below:
Statistical mapping on Host 1
after serving client Counter = 2
|
Host Name |
Port Range |
Protocol |
Host ID |
Filtering Mode
|
Load Weight |
Virtual IP |
Flag |
|
Host 2 |
80 To 80 |
TCP |
2 |
Multiple |
30 |
10.0.0.1 |
1 |
|
Host 1 |
80 To 80 |
TCP |
1 |
Multiple |
70 |
10.0.0.1 |
2 |
You notice that Flag value has been incremented by 1 to
make sure this host doesn’t receive the next traffic for the configured port
rules. This host will service the next traffic only when the Host 2 has served
the second request after Host 1.
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