Welcome, Guest. Please Login
 
  HomeHelpSearchLogin FAQ Radified Ghost.Classic Ghost.New Bootable CD Blog  
 
Page Index Toggle Pages: 1
Send Topic Print
Ghostcasting and OASIS servers (Read 2076 times)
troutstudio
Ex Member




Back to top
Ghostcasting and OASIS servers
Dec 19th, 2006 at 6:31pm
 
Apart from USB ghosting with Ghost 2003; I need to use Ghostcasting from Ghost 7.5 on Windows 2003 server. I am new to this.

Last time I set up a session, I used the default settings in the GhostCast session settings, and subsequently the session crashed a server at the school running OASIS (a Novell-based schools accounts system). I wasn't very popular! My guess is that there is a session setting which would prevent this kind of flodding of the network, as I know it can be used safely.

Has anyone experienced this and if so - any tips would be welcome as I can't really experiment with it during school hours; and after school is very difficult security-wise.

Thanks for your time.
 
 
IP Logged
 

nbree
Ex Member




Back to top
Re: Ghostcasting and OASIS servers
Reply #1 - Dec 20th, 2006 at 6:08am
 
Quote:
Last time I set up a session, I used the default settings in the GhostCast session settings, and subsequently the session crashed a server at the school running OASIS (a Novell-based schools accounts system). I wasn't very popular! My guess is that there is a session setting which would prevent this kind of flodding of the network, as I know it can be used safely.


That's not good, although it's hard to see how a spike in network traffic would crash a server. GhostCast itself doesn't really "flood", by the way - a good description of what IP multicast does is here at the cisco site http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/ipmulti.htm#wp1020555

IP multicast is only processed by systems that have subscribed to it, so it's not like plain broadcast, and if you have a Layer3 switch or a multicast-aware router the multicast traffic is only sent to the parts of the network that have signed up to receive the traffic. Even if you have only a layer2 switch the switch will fall back to sending traffic out to all the switch ports, but normal hosts will have the multicast traffic filtered by their NICs - classic Ethernet is by design a broadcast network, and part of what the NICs do is listen to all the traffic going by for some that is specifically tagged for the NIC to grab and send on to the CPU to process.

So, that's the theory. In practice, older routers can get choked by GhostCast, which by default goes as fast the slowest receiver in the GhostCast session can actually write the image data to disk. Routers typically listen to every packet sent on the network regardless of who it's actually for, and since it tries to go as fast as the slowest machine in the session that can still take up a lot of the available network bandwidth - more than a slow router can process with its CPU.

To deal with this you can manually limit GhostCast to slow it down. There are some advanced options under the "File" menu "Options..." to set the data rate limit in units of Megabytes per minute (an odd choice of unit, but for historical reasons that's what the DOS Ghost cloning client has always used).

Since there's no logical reason why this other server would fail at all (unless it's also configured as a router, which forces it to process every packet on the network - if it is, and the hardware isn't speced to keep up, that's not good) you will have to experiment by trial and error to find a "safe" throughput limit, so you'll have to coordinate with the OASIS admins to find a suitable time to experiment - start slow, and work up until you have problems, and then back off a notch.

Alternatively, you should be able to configure GhostCast to use "Unicast" mode instead of multicast mode. Unicasting means that instead of sending out one packet that the network distributes to all the clients, the server sends out one individually addressed network packet to each Ghost client (so the traffic load is actually vastly bigger, but it's traffic of a simpler kind).

Although it's vastly less efficient, if have a Layer2 switch, it will mean that the switch should be able to recognise the packets as not being intended for the OASIS server and thus won't impact it.

If you still have problems, another good place to ask for help is at http://forums.symantec.com/discussions/forum.jspa?forumID=109 ; which is for the network version of Ghost specifically. To help diagnose further it'd be good to know more about the structure of your network - especially what kind of switches you have.
 
 
IP Logged
 
Page Index Toggle Pages: 1
Send Topic Print