From: gah@ugcs.caltech.edu   
      
   Barry Margolin  wrote:   
      
   (snip, I wrote)   
   >> Yes, and I always note when someone mentions TCP/IP in the context   
   >> of UDP. The assumption is that you always have to implement TCP,   
   >> but that isn't true.   
      
   >> If it has to fit in a small ROM (such as diskless booting) or in   
   >> hardware (FPGA) then UDP is much easier.   
      
   > Technically true. Although only really practical if you only make fairly   
   > limited use of the network, e.g. just for diskless booting or   
   > configuration with DHCP.  If you do anything more complex, like   
   > providing a web-based UI or terminal interface for configuring the   
   > device, you'll need TCP.   
      
   > So the boot ROM might only need UDP, but whatever it loads in will   
   > almost certainly include TCP.   
      
   Some years ago, I was installing and configuring diskless Suns,   
   and got pretty used to how they worked. That included using   
   etherfind to debug problems with hex dumps of the packets.   
   Mostly from memory:   
      
   First a Sun machine uses RARP to find its own address.   
      
   Then UDP based TFTP to download the first level boot program,   
   presumably using a broadcast address as it doesn't know the   
   server address. Actually, I think they changed somewhere along   
   the line to use the address of the server replying to the RARP   
   request.   
      
   Then RPC based BOOTPARAMD to find the name and IP address   
   of the server, and some other such data.   
      
   I believe after that, most is done through NFS, which was UDP   
   based in those days. I am less sure now, but I believe it loads   
   the second level boot program and runs that, which again uses   
   RARP and BOOTPARAMD to determine the server and root file system,   
   which it then NFS mounts and loads.   
      
   At that point, it is executing the kernel from the root file system,   
   which includes most everything else it needs to know, including   
   other partitions to mount.   
      
   I didn't do any diskless Sun work since the change to NFS/TCP,   
   but it seems likely that is what more recent systems would do.   
      
   -- glen   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)