In IP based networks, there are basically three types of IP packets: unicase, broadcast, and multicast.
Unicast packets are sent from one host, with a valid sender IP address (except for very special things like DHCP discovery), to exactly one other host, specified by another valid IP address.
Broadcast packets are sent from one host to all hosts on the same physical network, by using the broadcast address of that network. For example, on
192.168.0.0/255.255.255.0, which means exactly the same), the network address would be
192.168.0.0 and the broadcast address would be
192.168.0.255. Broadcasts are used e.g. for discovery functions (IIRC for Windows file share name discovery; for some time protocol host discovery; you get the point).
Multicast packets are kind of a mixture between those two concepts. Those are sent from a host to a so-called “multicast group”, which hosts can subscribe to. Multicast groups can span several physical networks, theoretically even across the entire internet. Multicast-aware routers manage packet forwarding etc., just think of it as “magic” for now.
The interesting part of multicast is that in an example setup of 200 computing nodes on system boot, the kernel/initrd package needs only to be sent once to the wire, with all the nodes picking the file “from the wire”, as opposed to sending the same 5 Meg file 200 times.
This is of course not completely true, but for those intelligent multicast file transfer protocols supported by etherboot, the number of necessary transmissions of the boot file can be significantly reduced, with hosts booting a little later (milliseconds or seconds) jumping onto the running packet train and asking the server for retransmission of lacking packets after the first client has been catered for.
There are two multicast file transfer protocols supported by Etherboot as of now.
atftp stands for Advanced Trivial File Transfer Protocol. It supports RFC 1350, RFC 2090, RFC 2347, RFC 2348 and RFC 2349. atftp is intended for serving boot files to large clusters. It is multi-threaded and supports multicast.
tar xvzf atftp_0.6.2.tar.gz)
./configure; make; make install
/etc/servicesfile (or the appropriate files on your distribution) do not reference the port number that you will be running atftpd on, else atftpd will not work.
src/Configin your Etherboot source repository and add the following compile flags:
# Enable Multicast Support CFLAGS+= -DALLMULTI -DMULTICAST_LEVEL1 -DMULTICAST_LEVEL2 # Download files via Multicast tftp (RFC 2090) CFLAGS+= -DDOWNLOAD_PROTO_TFTM
/etc/dhcpd.confon many distributions): Set the filename to:
(adapt to your local storage location).
cd /etherboot/etherboot-5.1/contrib/mini-slamd make
filename "x-slam:///"; filename "x-slam://192.168.0.253:10000/18.104.22.168:10000";
mini-slamdwith the filename to be delivered as the parameter:
So those packets are non-routable.
There is no documentation available currently.
If multicast does not seem to work for you, you might have to set an IP route to the appropriate network interface on the server.
|3c595||5.2||Untested, please confirm to tlegge at rogers Dot com|
|3c90x||5.2||Eric Biederman and Tim Legge|
|eepro100||5.2||Eric Biederman and Tim Legge|
|ns8390||5.2||Tim Legge (Includes ne, ne2k-pci, possibly others)|