3.2.1 Unicast distribution and multicast distribution
In JP1/IT Desktop Management 2, there are two ways to distribute jobs: unicast distribution and multicast distribution. You can specify a different distribution method for each job.
A method of job distribution in which packets are sent from a higher system to each computer individually is called unicast distribution. Because the higher system has to send each job packet to each target computer, the number of times a packet is sent increases in proportion to the number of computers in the system.
In contrast, multicast distribution uses the IP multicast protocol to send packets to many specific computers from a higher system. In multicast distribution, the higher system distributes packets to a conceptual group called a multicast group. The packets are then distributed to each computer in that group. This method uses less traffic because the higher system only needs to send the job packet to one multicast group, regardless of how many computers belong to the group.
Each multicast group has its own unique IP address called a multicast address. During multicast distribution, packets are sent to this address. You can specify a multicast address when setting up the agent software on a managed computer. This registers the computer in the multicast group. Packets sent to a multicast address are distributed to all computers registered in that multicast group. Because a packet travels the common parts of the routes to the computers only once, jobs can be distributed efficiently without overloading the network.
The following figure illustrates the concept of unicast and multicast distribution:
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![[Figure]](GRAPHICS/KAN0300.GIF)
- Organization of this subsection
(1) Jobs distributed using multicast distribution
In JP1/IT Desktop Management 2, only Install package jobs can be distributed by multicast distribution. You can reduce the amount of traffic on the network considerably by using multicast distribution for the following types of jobs:
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Jobs with a large number of destinations
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Jobs requiring distribution of large packages
If a job has only a few destinations, or the associated package is small, multicast distribution can actually be less efficient. For jobs of this nature, specify unicast distribution when you create the job.
Note that whether you select multicast or unicast distribution when you create a job governs only the method of job distribution. It does not affect the destinations of the job. Regardless of whether the destination is an individual host, host group, or ID group, the job is distributed to the specified destinations using multicast distribution. If a computer specified as a destination is not registered in a multicast group, the job is distributed to that computer using the unicast method.
(2) Routes used by multicast distribution
When you specify multicast distribution for a job in JP1/IT Desktop Management 2, the packets are sent by multicast distribution only between the higher system and the managed computers directly connected to it. Unicast distribution is used between the system that executes the job and the higher system to which the managed computers are directly connected.