Kernel Protocol

The Kernel Protocol value specifies the method used for booting the IP-STB. The IP-STB is capable of downloading and booting boot images received from a variety of sources. If the IP-STB has a flash memory, then the boot image can also be stored and booted from that location. This speeds up the boot sequence by eliminating the time taken to download an image over the network.

The Kernel Protocol value is most commonly transmitted to the IP-STB by the DHCP server. When requesting an IP address during boot-up, the IP-STB also receives the Kernel Protocol it should use. A Splash Protocol value allows similar configuration of the Splash Screen behaviour.

The Kernel Protocol is a string composed of one or more of the following boot protocols:

• 1 = Bootcast (using the Infocast server)
• 2 = TFTP
• 3 = Local Storage (Flash Memory/Hard Drive) (if available)
• 4 = SAP (Session Announcement Protocol)
• 5 = Reserved
• 6 = HTTP (available from boot loader version 3.03)
• 7 = USB (available from boot loader version 5.4.x)

The desired protocols are specified in a comma-separated list in the desired order of preference (most desirable first). For instance, "3,1" means that if an image is found in the flash memory then that should be used first. Otherwise, the image available from the Infocast server should be used.

But, how do you get a new boot image to load once an image is available in the IP-STB flash memory? The process works as follows:

The "3" in the first position indicates that the flash memory is the preferred first choice. If no image is available then the IP-STB advances to the next specified protocol and attempts to boot with that. If, however, a boot image is found in the flash memory, then the next protocol is still examined. The Kernel Version string being broadcast from Infocast is compared with that stored locally in the flash memory. If the versions are different, then the IP-STB will proceed to download the image from the Infocast server.

All boot methods, apart from TFTP, use the Kernel Version to determine if the boot image being broadcast shall replace the boot image already stored in the IP-STB flash memory.

Other details

Should the value "3" appear anywhere in the Kernel Protocol string, then the boot image will be saved to the flash memory (overwriting an existing boot image there if the Kernel Version is different).

The most common Kernel Protocol string to use is "3,1,3", which is the default protocol list built into the IP-STB and used if nothing else is specified. The IP-STB first checks it's local storage to see if an image is available there. If none is found it proceeds to the next protocol. If an image is found, it proceeds to the next protocol and checks the Kernel Version. If it is different, then that boot image will be downloaded (and saved). Should that download fail, the final protocol, "3", indicates that the stored image shall be used. Otherwise the IP-STB would reboot and attempt the download again and again, despite the fact that it may have a valid image already stored in the local storage.

Two Stage Boot

If two stage boot mode is enabled (also known as fast boot mode), then the STB will boot from the image stored in flash memory, without checking or downloading software, and without checking the Kernel Protocol being sent via DHCP. It waits until it has completed booting before checking the version sent by Infocast and if they do not match, two stage boot mode will be temporary disabled. On the next reboot, the Kernel Protocol will be checked and responded to as described above.