This topic explains how to use Windows Deployment Services to create multicast transmissions.

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When to Implement Multicasting

Multicasting enables you to deploy an image to a large number of client computers without overburdening the network. When you create a multicast transmission for an image, the data is sent over the network only once, which can drastically reduce the amount of network bandwidth that is used.

Consider implementing multicasting if your organization: Multicasting might not optimize your installations if your organization:
  • Has network routers that support multicasting.

  • Is a large company that requires many concurrent client installations.

  • Wants to use network bandwidth efficiently. This is because with this feature, images are sent over the network only once, and you can specify limitations (for example, to only use 10 percent of your bandwidth).

  • Has enough disk space on client computers for the image to be downloaded.

  • Meets the requirements listed in the following section.
  • Has network routers that do not support multicasting.

  • Does not have bandwidth overload problems.

  • Deploys images to only a small number of client computers simultaneously.

  • Has disk space limitations on the client computers. (This is because the image is downloaded to client computers instead of being installed from a server.)

Prerequisites for Creating a Multicast Transmission

To implement this feature in your organization, you must have all of the following:

  • Routers that support multicasting. In particular, your network infrastructure needs to support the Internet Group Management Protocol (IGMP) to properly forward multicast traffic. Without the IGMP, multicast packets are treated as broadcast packets, which can lead to network flooding.

  • At least one install image that you want to transmit on the server

  • The Boot.wim file from the Windows Server 2008 media (located in the \Sources folder). Do not use the Boot.wim from the Windows Vista media unless your version of Windows Vista has SP1 integrated into the DVD.

  • Internet Group Membership Protocol (IGMP) snooping should be enabled on all devices. This will cause your network hardware to forward multicast packets only to those devices that are requesting data. If IGMP snooping is turned off, multicast packets are treated as broadcast packets, and will be sent to every device in the subnet.

Known Issues in Creating a Multicast Transmission

You may encounter the following issues when implementing multicasting:

  • If you use the Windows Vista Boot.wim file for multicast transmissions, you will be able to create the transmission, but people who boot into it will not be able to join it.

  • If multiple servers are using multicast functionality on a network (Transport Server, Deployment Server, or another solution), it is important that each server is configured so that the multicast IP addresses do not collide. Otherwise, you may encounter excessive traffic when you enable multicasting. Note that each Windows Deployment Services server will have the same default range. To work around this issue, specify static ranges that do not overlap to ensure that each server is using a unique IP address or Multicast Address Dynamic Client Allocation Protocol (MADCAP). To specify this option, right-click the server in the MMC snap-in, click Properties, and then click the Network Settings tab.

  • Each transmission can be run only as fast as the slowest client. That is, the entire transmission will be slow if there is one slow client. To resolve this issue, first determine the client that is holding back the transmission (this is called the master client). To do this, view the output of the following command: WDSUTIL /Get-MulticastTransmission /Show-clients. Next, disconnect the master client. This will force the master client to run the transmission by using the Server Message Block (SMB) protocol, and the other clients' multicast performance should speed up. If they do not speed up, there is a problem with the client's hardware (for example, a slow hard disk) or a network problem.

Transmission Types

There are two types of multicast transmissions. Note that content is transferred over the network only if clients request data. If no clients are connected (that is, the transmission is idle), data will not be sent over the network.

  • Auto-Cast. This option indicates that as soon as an applicable client requests an install image, a multicast transmission of the selected image begins. Then, as other clients request the same image, they too are joined to the transmission that is already started.

  • Scheduled-Cast. This option sets the start criteria for the transmission based on the number of clients that are requesting an image and/or a specific day and time. If you do not select either of these check boxes, the transmission will not start until you manually start it. Note that in addition to these criteria, you can start a transmission manually at any time by right-clicking it and then clicking Start.

Consider using Auto-Cast if: Consider using Scheduled-Cast if:
  • You work for a large corporation or an organization with high bandwidth that can handle installations at any time.

  • You do not want customers to have to wait for the installation to begin.
  • You work for a smaller organization or an organization where network traffic is an issue during the day. This way, you can set installations to occur during nonpeak hours or at night.

  • To reduce the total time of the transmission. Because you can set multiple clients to start at the same time, the time will be reduced because Windows Deployment Services will not have to resend a part of the image to clients that started after the first client.

  • You do not want the transmission to start until you manually start it (to do this, clear both check boxes when you create the transmission).

To create a multicast transmission with Deployment Server

Using the MMC Using WDSUTIL

Do one of the following:

  • Right-click the Multicast Transmission node, and then click Create Multicast Transmission.

  • Right-click an image, and then click Create Multicast Transmission.
  1. Click Start, right-click Command Prompt, and click Run as administrator.

  2. Do one of the following:

    1. To create an Auto-Cast transmission

      Syntax: WDSUTIL /New-MulticastTransmission /Image:<image name> /FriendlyName:<friendly name> /ImageType:Install /ImageGroup:<Image group name> /TransmissionType:AutoCast

    2. To create a Scheduled-Cast transmission

      Syntax: WDSUTIL /New-MulticastTransmission /Image:<image name> /FriendlyName:<friendly name> /ImageType:Install /ImageGroup:<Image group name> /TransmissionType:ScheduledCast [/Time:<yyyy/mm/dd:hh:mm>][/Clients:<no of clients>]

To manage transmissions

Using the MMC Using WDSUTIL
  • Start the transmission. If the transmission is the Scheduled-Cast type, there is at least one client, and the transmission has not started yet, you can right-click the transmission and then click Start.

  • Delete the transmission. If you right-click the transmission and click Delete, the multicast transmission stops and each client installation will fall back to using unicast transmission. That is, the client installations will not be deleted or stopped, but they will not use the multicast transmission to complete the installation.

  • Deactivate the transmission. If you right-click the transmission and then click Deactivate, each client that is currently installing will continue, but no new clients will be joined to the transmission. After each current client installation is completed, the transmission will be deleted. If there are no clients when you click this option, the transmission will be deleted instantly.

  • View the transmission's properties. To view the properties, right-click the transmission and then click Properties. Note that you cannot edit the properties of a transmission after it is created. To make a change after you have created a transmission, you need to delete it and then recreate it.

  • Refresh the transmissions and data. To do this, right-click a transmission and then click Refresh. You can also refresh the data by pressing F5.
  • To start the transmission

    Syntax: WDSUTIL /Start-MulticastTransmission /Image:<image name> /ImageType:Install /ImageGroup:<image group name>

    Note

    You can start the transmission only if it is the Scheduled-Cast type, there is at least one client, and the transmission is not already started.
  • To delete the transmission

    Syntax: WDSUTIL /Remove-MulticastTransmission /Image:<image name> /ImageType:Install /ImageGroup:<image group name> /Force

  • To deactivate the transmission

    Syntax: WDSUTIL /Remove-MulticastTransmission /Image:<image name> /ImageType:Install /ImageGroup:<image group name>

  • To view the transmission's properties

    Syntax: WDSUTIL /Get-MulticastTransmission /Image:<image name> /ImageType:Install /ImageGroup:<image group name>

To manage clients in a transmission

Using the MMC Using WDSUTIL
  • View clients and see progress. To view any connected clients, expand the Multicast Transmissions node and then click the image. The connected clients (including the current installation time and the percentage complete) are shown in the right pane.

  • Stop a client installation. To stop the installation completely, right-click a client and then click Disconnect. You should use this option with caution because the installation will fail and the computer could be left in an unusable state.

  • Disconnect a client from a multicast transmission. To discontinue the transmission for a particular client but continue to transfer the image through unicasting, right-click the client, and then click Bypass multicast.
  • To view clients and see progress

    Syntax: WDSUTIL /Get-MulticastTransmission /Image:<image name> /ImageType:Install /ImageGroup:<image group name> /show:clients

  • To stop a client installation completely

    Syntax: WDSUTIL /Disconnect-Client /ClientID:<id> /Force.

    Note

    You should use this option with caution because the installation will fail and the computer could be left in an unusable state.
  • To disconnect a client from a multicast transmission but continue to transfer the image by using unicasting

    Syntax: WDSUTIL /Disconnect-Client /ClientID:<id>

  • To view the client <id> for each transmission

    Syntax: WDSUTIL /Get-MulticastTransmission /Image:<image name> /ImageType:Install /ImageGroup:<image group name> /show:clients

To configure the UDP port range for multicasting

This setting specifies the range of UDP ports to use for multicasting and other components, such as the Trivial File Transfer Protocol (TFTP) provider. Before you change this range, you need to have at least as many ports as you have sessions and concurrent clients accessing the server. In terms of multicasting, a session is a network interface on your server. To calculate the number of sessions, multiply the number of network adapters on your server by the number of images that could be concurrently transferred using multicasting. For example, if you have two network adapters, and clients are connected on both interfaces, the content will be sent on the network twice (once from each interface). So in this case, you would need at least two ports. Because this range is also used by the TFTP provider, you will need as many available ports as you have concurrent clients accessing the server.

Using the MMC Using WDSUTIL
  1. Right-click the server, and then click Properties.

  2. On the Network Settings tab, specify the UDP port range.

  3. You must restart the service before the changes will take effect. To do this, right-click the server in the MMC snap-in, click All Tasks, and then click Restart.
  1. Click Start, right-click Command Prompt, and click Run as administrator.

  2. Run WDSUTIL /Set-Server [/Server:<name>] /Transport /StartPort:x /EndPort:y.

  3. You must restart the service before the changes will take effect. To do this, run wdsutil /stop-server and then run wdsutil /start-server.

To configure how the server will obtain IP addresses for multicasting

The server allocates a multicast IP address to each multicast session, and all connected clients listen in on that address. It's important that all IP addresses be unique on the network to ensure that each client receives the correct data. If you have a complex network, you should consider using DHCP to select the addresses. In more basic environments, you can configure a range and have the Windows Deployment Services server select the address.

Using the MMC Using WDSUTIL
  1. Right-click the server, and then click Properties.

  2. On the Network Settings tab under Multicast IP Address, select one of the following:

    • Obtain IP address from DHCP. You can select this option only if your DHCP server supports it. The IP address for each namespace will be obtained by using MADCAP (RFC 2730, Multicast).

    • Use IP address from the following range. You will need to enter a range.

  3. You must restart the service before the changes will take effect. To do this, right-click the server in the MMC snap-in, click All Tasks, and then click Restart.
  1. Click Start, right-click Command Prompt, and click Run as administrator.

  2. Do one of the following:

    • To use MADCAP to obtain the IP address for each namespace, run WDSUTIL /Set-Server [/Server:<name>] /Transport /ObtainIPFrom:DHCP.

    • To configure a preset range of IP addresses, run WDSUTIL /Set-Server [/Server:<name>] /Transport /ObtainIPv4From:Range /Start:x.x.x.x /End:y.y.y.y.

  3. You must restart the service before the changes will take effect. To do this, run WDSUTIL /stop-server and then run WDSUTIL /start-server.