Citrix Provisioning Services Boot Process

The PVS target device acquires an IP address using the DORA Process (Discover, Offer, Request and Acknowledge)

1. The Target Device broadcasts DHCP Discover packets.

2. The DHCP Server sends a DHCP offer packet to the Target Device with the IP address, Subnet Mask, lease time, Default Gateway, DNS Server and Domain Name information to the Target Device.

3. The Target Device sends a unicast message to the DHCP Server requesting the offered IP address. A Transaction ID is used to track the accepted offer. The Target Device will send a broadcast message notifying other DHCP Servers that the offer from another DHCP Server was accepted.

4. The DHCP server sends a DHCPACK packet to the Target Device.

Download the bootstrap file from the TFTP server to the Target Device

These are the two popular methods for getting Target Device boot information.

A. Network Booting – with DHCP options (no PXE Service)

1. The TFTP server name and Boot file name (ardbp32.bin) is provided using options 66 & 67. From the TFTP server the bootstrap file is downloaded to the Target Device using the TFTP server name from the DHCP option 66 and filename (ardbp32.bin) from DHCP option 67.

B. Network Booting – with PXE Service (no DHCP options)

1. The firmware of the Target Device adds option 60 to the DHCP Discover packet being broadcast.

2. DHCP server responds with IP Address, Gateway and Subnet information.

3. The PXE server replies with the TFTP server address and bootstrap file name.

4. The Target Device sends a request to the TFTP server for the bootstrap file.

5. The TFTP server replies with the bootstrap file name.

Logon process

After the Target Device gets the IP address and downloads the bootstrap file it proceeds to login to the PVS server to start streaming the vDisk image.

1. The Target device contacts the PVS server specified in the bootstrap file using the default UDP port 6910.

2. The PVS server responds with the IP address and the port number to continue the login process.

3. The Target device contacts and identifies itself by its MAC address to the PVS server.

4. The PVS server replies with all disks, client and policy information needed and sent ot the Target Device.

5. The Target device requests the IP address and information on which vDisk to use.

6. The PVS server grants access for I/O operation and the Target device requests which vDisk will be streamed.

7. The PVS server sends the all the vDisk information including write cache location if the Target Device is in standard mode.

Load Balancing

All PVS servers are capable for acting as both a login server (booting and load balancing) and I/O server (streaming vDisk). A PVS login server normally attempts to load balance devices between all PVS servers that have access to the given vDisk when the Target device initially logs in.

Streaming vDisk (BNISTACK / MIO)

The Target Device and the PVS server continue to communicate exchanging the vDisk data until the Operating system starts loading drivers and the BNISTACK is successfully loaded.

Once the BNISTACK driver is loaded and PVS server and Target Device start handshake and multiple I/O communication begins. At this point the following information is exchanged and the Target device is operation and R/W request continues.

1. vDisk name

2. Image mode

3. Active Directory Password Management Option

4. Write Cache Type and Size

5. Client Name

6. Licensing

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About Murugan B Iyyappan

Working as a Technical Specialist - Citrix solutions architect with 13 years of experience in the IT industry. Expertise in Citrix XenApp and VMware in Windows platform.
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