System Center Configuration Manager 2007 : Configuration Manager Network Communications (part 3) - Site-to-Site Communications - Configuring Senders, Configuring Sender Addresses

Site-to-Site Communications

Sites in a ConfigMgr hierarchy must share configuration information, client data such as inventory and discovery data, status information, and so on. All data exchanges between sites are transmitted by means of senders. Senders use the SMB protocol to transfer files between sites.

Configuring Senders

Configuration Manager sites are configured to use networks for site-to-site communications by creating a sender corresponding to the underlying network. By default, each Configuration Manager site has one sender installed—a standard sender. In most cases, the standard sender is the only one you will use. A standard sender uses your primary network for communications.

To add, delete, or change the properties of senders from the Configuration Manager console, navigate to System Center Configuration Manager -> Site Database -> Site Management -> <Site Code> <Site Name> -> Site Settings -> Senders. If you have sites connected by any of the Remote Access Services (RAS) connection types shown in Figure 8, you can add senders to use those connections.

Figure 8. Selecting the sender type for a new sender

Each sender can have the following settings configured:

• Maximum Concurrent Sendings (All Sites)— Senders can use multiple threads to send more than one job at a time. This setting controls the maximum number of sendings (from 1 to 999) that the sender can execute simultaneously. Increasing this number speeds up site-to-site communications but can potentially consume more bandwidth.

• Maximum Concurrent Sendings (Per Site)— This is the number of sendings (from 1 to 999) that can execute simultaneously to a single site.

  This setting should always be set to a lower value than Maximum Concurrent Sendings (All Sites) to avoid the possibility that all of a sender’s threads will be occupied sending to a site that is unavailable. RAS senders are limited to one thread per site.

• Number of Retries— Specifies the number of times (from 1 to 99) that the sender will retry a failed sending.

• Delay Before Retrying (minutes)— Specifies the delay (from 1 minute to 99 minutes) before retrying a failed sending attempt.

Note: About Bandwidth Throttling Between Sites

If you implement bandwidth throttling between sites, the sender will send all data serially between those sites, regardless of the number of concurrent sendings you have configured on the sender. 

Figure 9 displays the default values for the standard sender configuration. If you have sufficient server resources and available network bandwidth, you may want to increase the number of threads allowed by the Maximum Concurrent Sendings setting from the default value. Before increasing this setting, you should obtain a baseline of network utilization and server performance data for key server resources such as the processor and network interface to verify that additional capacity is available. You should closely monitor the change to ensure that server and network performance are not adversely affected.

Figure 9. The Standard Sender Properties sheet showing the default values

About Courier Sender Another way of sending data between sites is through the courier sender. The courier sender is a virtual sender that does not actually transfer data between sites, but rather accounts for packages transferred using Out of Band (OOB) mechanisms. Courier sender is used only for software distribution, and like other senders, it requires that you configure an address at the source site for the target site. Microsoft designed the courier sender capability to allow package distribution between sites using physical media such as tape, DVD, and external hard drives. You can also use courier sender to manage packages copied by third-party replication technologies, such as SAN replication. To manage courier sender, you use the ConfigMgr Courier Sender program in the Configuration Manager 2007 program group. This application allows you to create outgoing parcels, which creates a compressed version of the package and instruction files, and then mark them as received at the destination site. Courier sender was a relatively unused feature in earlier versions of SMS. This capability would be more valuable as a tool with console integration and a scripting interface, which are not currently available.

Configuring Sender Addresses

In order to join two sites together as part of a Configuration Manager hierarchy, each of the sites must have at least one sender address configured for the other site. All information sent between sites will use these addresses and their corresponding senders. An address specifies a sender type and the site server for the destination site. You can configure additional parameters to control the behavior of sender addresses. To add, delete, or change the properties of addresses from the Configuration Manager console, perform the following steps:

1.	Navigate to System Center Configuration Manager -> Site Database -> Site Management -> <Site Code> <Site Name> -> Site Settings -> Addresses.
2.	To create a new address, right-click the Addresses node and choose New.
3.	Select the appropriate sender type. Figure 10 shows the initial dialog box for creating a new standard sender address. Figure 10. Entering the destination server for a new address Note that the relative address priority will be set to 1 for the first sender you create for a destination site. If you subsequently create additional addresses for the same site, their relative priorities will be 2, 3, and so on. The address with the lowest relative priority is always tried first. By default, the sender will use the security context of the computer account of the local site server. You can change the relative priority after the address is created by right-clicking the higher priority address and choosing decrement priority.
4.	In the next dialog box, shown in Figure 11, you can set a schedule for the address. The schedule specifies what types of traffic are allowed to use the address during a given period. During certain hours, you may choose to limit use of the address to medium- or high-priority traffic or to high-priority data only, or you may not want to use the address at all. Figure 11. Setting the schedule for a new address
5.	The final screen for creating a sender address allows you to specify rate limits for the address. As shown in Figure 12, you can specify the rate limits for a given time interval. The available values are limited to 0%, 10%, 25%, 50%, 75%, 90%, or 100%. Specifying a rate limit prevents the sender from using multiple threads, even if the maximum concurrent sendings settings (refer to Figure 5.9) allow multiple threads. Figure 12. Specifying the maximum bandwidth utilization for a new address

When sending limits are in effect, the sending site will time how long it takes to send each block of data and pause before sending the next block for an interval determined by the sending limit. In general, this results in the sender using all available bandwidth the designated percentage of time, which is roughly equivalent to using the allowed percentage of overall bandwidth. In some cases, factors other than bandwidth availability may cause a delay in receiving acknowledgements, resulting in calculations of available bandwidth that may be unrealistically low. As an example, if the destination site system is heavily loaded or if network latency is a factor, the elapsed time before an acknowledgement is received may be high even though ample bandwidth is available. In cases of networks having very low bandwidth or those that may frequently be near saturation with other traffic, you may find the pulse mode option to be more useful in limiting network utilization by the sender. As shown in Figure 13, pulse mode sends blocks of data of a specific size at fixed intervals. The default for pulse mode is 3KB blocks at 5-second intervals.

Figure 13. Limiting bandwidth utilization through pulse mode

You can choose to create more than one address to the same site. This allows you to provide different policies for different data priorities and multiple sender types.

Note: About Latency Between Sites

Restrictions on sending between sites during certain hours can introduce substantial latency in replicating objects and data throughout the hierarchy. It is important to keep this in mind when working with software packages. If updates are made to a package before a child site has received previous updates to the same package, redundant files may be sent between sites. Binary differential replication also does not work between sites until all targeted sites have received at least one version of the package.