Progress
Installation and Configuration Guide
Version 9
for Windows
Using NameServer Replication
UDP broadcasting supports NameServer replication by allowing a client or Unified Broker request to be received by multiple NameServers listening on the same UDP port and configured on different machines within the same subnet. Because every host on a subnet receives every broadcast request, one or more of these hosts can support a NameServer that receives and handles the same messages. This provides fault tolerance for both a client connection request and a Unified Broker registration request.
Thus, to configure and use replicated NameServers, you must:
- Run each NameServer instance on a separate host located within the same subnet.
- Configure each NameServer instance to listen on the same UDP port.
- Configure each client application to send its connection request and each Unified Broker to send its registration request using the subnet UDP broadcast address instead of the NameServer host address.
There is one broadcast address for each subnet. Using this address and the specified UDP port number, a client or Unified Broker sends a single request that is recognized by every NameServer listening on that port in the subnet.
Figure 7–6 shows a client, a Unified Broker, and two replicated NameServers. The NameServer configurations shown for NameServer NS1 (above the dotted line) appear as they might in the
ubroker.properties
file for each host.Figure 7–6: NameServer Replication
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In Figure 7–6, one NameServer is located on a machine with the IP address 172.20.0.7 and another is located on a machine with the IP address 172.20.16.12. Both NameServers listen on UDP port 5162. The UDP broadcast address for these NameServers is 172.20.255.255. The Unified Broker is configured to register with a controlling NameServer remote from the Unified Broker machine using the UDP broadcast address 172.20.255.255 as the hostName. When the Unified Broker registers with its controlling NameServer using the UDP broadcast, it registers with both replicated NameServers. Similarly, when the client broadcasts its connection request using 172.20.255.255 as the NameServer host name, both replicated NameServers receive the request. The client uses the Unified Broker connection returned by the first NameServer that responds.
Note that if the NameServer at IP address 172.20.0.7 moves to a different host on the subnet, for example, with IP address 172.20.16.5, neither the client application nor the Unified Broker configuration has to change.
Implementing NameServer Replication
To configure and use NameServer replication, follow these steps:
- Install the NameServer on each host within a single subnet where you want to replicate a NameServer configuration.
- Configure each replicated NameServer to listen on the same UDP port number.
- Determine the UDP broadcast address for the subnet where the NameServer hosts reside. For more information, see the "Determining the Broadcast Address" section.
- Configure each Unified Broker instance (AppServer, SonicMQ Adapter Broker, WebSpeed Transaction Server, or DataServer) to use a controlling NameServer as follows:
- Provide connection parameters to the client (AppServer, DataServer, or WebSpeed) that specify the required Application Service name, the broadcast address from Step 3, and the UDP port number that you specified in Step 2.
Determining the Broadcast Address
You can determine the broadcast address of a UNIX machine by using the
netstat
andifconfig
commands, as in this example:
This example shows that the IP address for bali is 172.20.0.7, and its broadcast address is 172.20.255.255.
On NT, you can determine the broadcast address following these steps:
- Enter the
ipconfig
command in the console, as shown in this example:- For each bit in the Subnet Mask that has a value of 0, convert the corresponding bit in the IP Address to 1.
Note that the IP Address and Subnet Mask are composed of four dot-separated decimal numbers and each decimal number represents an 8-bit binary number. Also note that the decimal number 255 is 11111111 in binary.
In this example, the last two decimal digits of the Subnet Mask are zeros. Since the corresponding bits in the IP Address must be converted to 1, the last two decimal numbers of the IP Address should be 255. Therefore the broadcast address is 172.18.255.255. (For more information on determining broadcast addresses, consult with you network administrator.)
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