<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<br>
<div class="moz-cite-prefix">On 2014-04-27 22:59, Bart Kus wrote:<br>
</div>
<blockquote cite="mid:535DEE30.8030802@bartk.us" type="cite">
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
All that routing stuff is at a layer higher than I was meaning to
ask about.<br>
<br>
PtMP is just short hand for Point to Multi-Point communication.<br>
<br>
In the two modes of operation you outlined, it seems to me it's
possible for 2 mobile stations to communicate with 1 common fixed
station by simply transmitting packets that bear either a common
2-digit code, or contain the fixed station's callsign.</blockquote>
<br>
Yes.<br>
<br>
<blockquote cite="mid:535DEE30.8030802@bartk.us" type="cite">Is the
fixed station capable of sending responses addressed distinctly to
each of the 2 mobile stations?</blockquote>
<br>
Yes, but not programmatically. While the control head and the
Windows software can change the addressing, that's done through the
USB port, not over the Ethernet port. I believe the USB control
interface is documented, so one could write software to do that, but
that's too much nuisance for me.<br>
<br>
<blockquote cite="mid:535DEE30.8030802@bartk.us" type="cite">Is the
addressing doable on a per-packet basis, or would the fixed radio
need to be re-programmed with a new destination address (callsign)
or something?</blockquote>
<br>
No, and yes (see above).<br>
<br>
<blockquote cite="mid:535DEE30.8030802@bartk.us" type="cite">Can it
simply transmit a frame bearing the common 2-digit code and all
stations in earshot will receive it?<br>
</blockquote>
<br>
Yes. It's totally up to the receiving radio as to whether use the
2-digit code or callsign for filtering. If it doesn't, it receives
everything it hears.<br>
<br>
<blockquote cite="mid:535DEE30.8030802@bartk.us" type="cite"> In
terms of multiplexing, how does any station know when it is OK to
transmit?</blockquote>
<br>
Later D-Star voice (+ low speed data) radios had a "busy lockout"
option. The ID-1 has no such visible option, so I don't know the
answer to your question.<br>
<br>
<blockquote cite="mid:535DEE30.8030802@bartk.us" type="cite">Is
there a CSMA scheme or is it just an immediate transmission when
data comes in? Is there something more advanced, like ARQ?<br>
</blockquote>
<br>
No, yes, no.<br>
<br>
<blockquote cite="mid:535DEE30.8030802@bartk.us" type="cite"> In the
above scenario, are the 2 mobile stations able to communicate
directly between each other? (assuming all nodes can hear each
other here)<br>
</blockquote>
<br>
Absolutely. Unless a receiving radio filters on the 2-digit code or
callsign, it receives everything. By extension, when it transmits,
everyone else hears it. The sender (absent a protocol) has no way
of knowing what receiver is hearing (or filtering) it.<br>
<br>
About ten years ago I wrote a program to send (serial) data (@ 1200
bps) between multiple D-Star voice radios (which all have the 1200
bps data "subchannel"). Those radios had "busy lockout", but the
software had no way of knowing if the frequency was in use. I used
a simple "ACK" protocol, and in the absence of receiving an ACK,
used a semi-exponential random backoff if no ACK was received. In
other words, I used the absence of an ACK as a probable indication
of a collision.<br>
<br>
The ID-1 is two orders of magnitude faster and encapsulates and
sends arbitrary Ethernet frames, but not much else is different (the
2-digit code and callsign filtering is also applicable to voice
usage). Of course, in TCP/IP, the packet originator will do any
necessary retries.<br>
<br>
The whole thing is suitable for multiple stations on a frequency,
only in a low-traffic environment. Of course, this is perfectly
suited to typical Amateur Radio repeater usage [Dean's sarcasm is
showing].<br>
<br>
Note that in original D-Star design, it was thought (John Hays,
correct me if I'm wrong) that a D-Star DD-mode repeater module would
receive each Ethernet packet, lookup the target callsign in the
callsign "roaming" database to see where (which repeater) the target
callsign was last heard*, and send the encapsulated packet over the
Internet to a destination dd-mode repeater, where the packet would
be sent out over the air, hopefully to a listening ID-1 radio. I
believe (again, John knows this better than I for DD-mode) it's only
after the packet has been de-encapsulated by the receiving radio,
that the destination IP address in the Ethernet packet is even
examined, and that only by the host or router connected to the
radio. This is called "callsign routing", and it works in exactly
the same way for voice (DV-mode). Unfortunately, this mechanism is
way too complicated for the average Amateur Radio operator to
understand, so it is rarely used for voice, having been effectively
replaced (oops, supplanted) by "reflectors" linking repeaters in an
EchoLink-like scenario.<br>
<br>
So, you may wonder, why do I want to even screw around with the ID-1
radios in DD-mode? Because there are so few of them, and I have one
on the air, and the SnoCo DEM has one on the air. I think John Hays
has one (or maybe he has the Icom 9100 ???). I think Scott has one
at home (in the box). Gary Fiber (a former Icom employee) has one
in his vehicle.<br>
<br>
<blockquote cite="mid:535DEE30.8030802@bartk.us" type="cite"> <br>
<div class="moz-cite-prefix">On 4/27/2014 6:48 PM, Dean Gibson
AE7Q wrote:<br>
</div>
<blockquote cite="mid:535DB372.5040607@ae7q.com" type="cite">
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
I had to Google to find out what P2MP was, but in my VERY brief
Google education on the subject, I don't think it applies.<br>
<br>
The radio doesn't multiplex anything.<br>
<br>
The consumer-grade routers I own (Linksys BEFSR41, Netgear
WGT624v2) seem to have no way to turn off NAT. dd-wrt is not
possible with the BEFSR41; it is "work-in-progress" for the
WGT624v2. NAT seems to make routing issues a little more
complex to think through. Both routers have the ability to
specify a "DMZ host", but I think that just turns on universal
NAT to that host. Both routers have the capability of manually
adding entries to a static routing table, but I don't know if
that skips over the NAT. If we have to have NAT, it seems to me
that the best way to set up the router is with the radio
connected to the LAN side (with whatever private IP address we
want), and have the WAN side connected to the 44.x.x.x network.
That allows incoming (ie, via the radio) packets to go wherever
they can and responses to come back; whereas orienting the
router the other way (unless we use the "DMZ host" feature)
doesn't. I suppose I could donate one of my (very) elderly
(2005) Dell PowerEdge 1650 1U servers to the effort, but that
seems like a bit of overkill ...<br>
<br>
What I think would be a good idea is to meet and discuss this
face-to-face (pretty much anytime) with diagrams, rather than
shoveling eMails back and forth. Scott, if your schedule
permits, you are more than welcome.<br>
<br>
-- Dean<br>
<br>
ps: Scott, I plan to come to the DEM on Tuesday to start on
this, unless you're not going to be there, or other conditions
(like ongoing slide work) make it a bad idea.<br>
<br>
<div class="moz-cite-prefix">On 2014-04-27 12:06, Bart Kus
wrote:<br>
</div>
<blockquote cite="mid:535D5521.1010204@bartk.us" type="cite">
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
<div class="moz-cite-prefix">OK, we can slap some extra
security on there. Shouldn't need an extra router for that.<br>
<br>
What about the PtMP story? One of the advantages you
mentioned (Dean) was mobile access. Can it multiplex access
somehow?<br>
<br>
--Bart<br>
<br>
<br>
On 4/27/2014 9:53 AM, Dean Gibson AE7Q wrote:<br>
</div>
<blockquote cite="mid:535D3627.7030003@ae7q.com" type="cite">
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
Exactly (or the equivalent).<br>
<br>
<div class="moz-cite-prefix">On 2014-04-27 09:34, John Hays
wrote:<br>
</div>
<blockquote
cite="mid:EBCFEB6E-E247-42FB-98E9-FB69315B6DB1@hays.org"
type="cite">
<meta http-equiv="content-type" content="text/html;
charset=ISO-8859-1">
<div>It should be on a dedicated router on its own
segment. <br>
<br>
Sent from my iPhone</div>
<div><br>
On Apr 27, 2014, at 9:27 AM, Dean Gibson AE7Q <<a
moz-do-not-send="true" href="mailto:hamwan@ae7q.com">hamwan@ae7q.com</a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
The only "authentication" the radio has, are the
following:<br>
<ol>
<li>The radio can be set to only receive remote
transmissions that include a two-digit decimal
code; <b>or</b></li>
<li>The radio can be set to only receive remote
transmissions that are addressed to the callsign
programmed into the receiving radio (I would
recommend this setting).<br>
</li>
</ol>
Any other authentication would have to be provided by
a router or firewall.<br>
<br>
<div class="moz-cite-prefix">On 2014-04-26 22:39, Bart
Kus wrote:<br>
</div>
<blockquote cite="mid:535C980B.6090504@bartk.us"
type="cite">Any packets on that LAN are considered
trusted since they passed authentication. What's
the auth story on the 23cm modems? <br>
<br>
--Bart <br>
<br>
On 4/26/2014 10:37 PM, Tom Hayward wrote: <br>
<blockquote type="cite">On Sat, Apr 26, 2014 at 9:26
PM, Dean Gibson AE7Q <a moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:hamwan@ae7q.com"><hamwan@ae7q.com></a>
wrote: <br>
<blockquote type="cite">At the Snohomish County
DEM, place a router (or bridge) between the ID-1
and the 44.24.240.x network. <br>
In this scenario, the ID-1 located at my house
would also be connected to a router that acts as
though it were directly connected to the
44.24.240.x (or any other) network at the DEM. <br>
</blockquote>
We have a router at Snohomish County DEM with an
extra port that could be used for this. The subnet
there is 44.24.240.128/28. We have another subnet
of address pairs set aside for router-to-router
links. So as far as networking goes, we could
execute your plan. I can't commend about the
feasibility of any of the other bits. <br>
<br>
Tom </blockquote>
</blockquote>
</div>
</blockquote>
</blockquote>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
PSDR mailing list
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:PSDR@hamwan.org">PSDR@hamwan.org</a>
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://mail.hamwan.org/mailman/listinfo/psdr_hamwan.org">http://mail.hamwan.org/mailman/listinfo/psdr_hamwan.org</a>
</pre>
</blockquote>
<br>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
PSDR mailing list
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:PSDR@hamwan.org">PSDR@hamwan.org</a>
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://mail.hamwan.org/mailman/listinfo/psdr_hamwan.org">http://mail.hamwan.org/mailman/listinfo/psdr_hamwan.org</a>
</pre>
</blockquote>
<br>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
PSDR mailing list
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:PSDR@hamwan.org">PSDR@hamwan.org</a>
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://mail.hamwan.org/mailman/listinfo/psdr_hamwan.org">http://mail.hamwan.org/mailman/listinfo/psdr_hamwan.org</a>
</pre>
</blockquote>
<br>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
PSDR mailing list
<a class="moz-txt-link-abbreviated" href="mailto:PSDR@hamwan.org">PSDR@hamwan.org</a>
<a class="moz-txt-link-freetext" href="http://mail.hamwan.org/mailman/listinfo/psdr_hamwan.org">http://mail.hamwan.org/mailman/listinfo/psdr_hamwan.org</a>
</pre>
</blockquote>
<br>
</body>
</html>