On Sun, 29 Aug 1999, Cathryn Mataga wrote:
> I'm still not exactly clear how netrom is supposed to work. At least
> it seems to be doing something. That is my nr_nodes list has grown to
> over 110 lines in just a few minutes. And I see my call popping up on
> neighboring node lists. But, I think with verbose on, when it sends
> the node packet it blows out the packet length because I get a
> 'mkiss:ax3:truncating oversized transmit packet! message when verbose
> is on. So, I turned off verbose, and I changed all my packet lengths
> to 1024, except for my HF port. (I'm still not clear on how the
> packet length entry in axports works. I thought that was just for
> connected packets. It seems to me like unconnected packets should
> just go through no matter what, though I'm just guessing here.)
> After making both those changes, I've had netromd running for awhile,
> and having send the 'truncating oversized transmit packet!' message
> once.
Hmm. I guess you have something wrong in those paclen (or MTU) settings.
The NET/ROM MTU should be 20 bytes less than AX.25 MTU. Common values for
slow packet (1k2...9k6) would be 256 in axports and 236 in nrports.
> At this point I'm not exactly sure what the point of the node broadcasts
> is. Like with all the lists in the nr_nodes file.
They are routing broadcasts. Something vaguely similar to RIP broadcasts
in internet protocols. And the /proc/net/nr_neigh and nr_nodes files
comprise the kernel NET/ROM routing table. Nr_neigh has the known
NET/ROM neighbours and nr_nodes the actual routes with references to the
neighbours that should be used to reach a node (there can be up to three
routes (neighbours) for each node, they have different qualities and are
used in quality order).
> Just for fun, I stuck
> a 'netrom' entry in my FBB bbs, though, I'm not exactly clear myself how
> that works. For example, should I be able to just
> do a 'call netrom luxnet' for example, and have it figure out where to
> go? Right now I seem to be able to call the nr_neigh stations, but
> I haven't had much luck going out any farther.
Yes you should be able to do that.
> Is the netrom software useless without the 'node' program to
> go with it? Or is routing able to occur without connecting through
> the nodes manually.
No and yes. Node doesn't have anything to do with the actual NET/ROM
networking in Linux. It is just an application level front end.
As to the routing, a small clarification might be in order.
The NET/ROM protocol can be seen as having three separate protocols: The
L3 or network layer protocol that deals with routing the incoming NET/ROM
frames to their destinations, similar to IP. Then there is the L4 or
transport layer protocol that handles the end-to-end communications,
establishing virtual circuits, ordering of data etc. This is somewhat
similar to what TCP does. Then there is the routing protocol that handles
propagating new routes over the network.
All these of course run over AX.25. The network and transport protocols
over connected mode AX.25 links and the routing broadcasts over
unconnected mode.
The network and transport layer protocols are all done in the kernel. User
only sees the appropriate headers in each NET/ROM frame while watching
"listen" output. The routing updates, both listening to other broadcasts
and sending your own, are done by netromd. Netromd updates the kernel
NET/ROM routing tables according to what it hears and kernel does the
actual routing.
--
Tomi Manninen Internet: [EMAIL PROTECTED]
OH2BNS AX.25: [EMAIL PROTECTED]
KP20ME Amprnet: [EMAIL PROTECTED]
