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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Scott,</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Yes, I agree that the third alternative
seems best. </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Tim</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
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<p class=MsoNormal><b><font size=2 color=black face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma;color:windowtext;font-weight:bold'>From:</span></font></b><font
size=2 color=black face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;
color:windowtext'> sis-ams-bounces@mailman.ccsds.org
[mailto:sis-ams-bounces@mailman.ccsds.org] <b><span style='font-weight:bold'>On
Behalf Of </span></b>Scott Burleigh<br>
<b><span style='font-weight:bold'>Sent:</span></b> Thursday, July 10, 2008
12:53 PM<br>
<b><span style='font-weight:bold'>To:</span></b> sis-ams@mailman.ccsds.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [Sis-ams] minor
heartbeat-related issue</span></font></p>
</div>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'>Edell, David J. wrote: </span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>I ran into a similar issue when finishing
my implementation. </span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>I believe the intent was for the reply
method to be inferred from the transport service in that case--meaning that
this is a piece of data missing in the AMS content itself. In my case, I
think the node-id was included which I used in the absence of TS specified
context to infer the reply address in the APL implementation for unregistered
nodes (which uses a direct mapping). I don't remember if/how I had addressed
this for an unregistered registrar.</span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'>David's answer is right, and I realize this may not be
wholly satisfactory. There's an implicit expectation that the receiving
entity can figure out the MAMS endpoint name of the sender in a
transport-specific way that is left as an implementation issue. For
example, if you're using UDP as the transport for MAMS traffic then when you receive
the heartbeat you can get the IP address and port number of the sending socket
from the recvfrom() parameters and send the you_are_dead message back to that
socket. You'd have similar information if you used, say, the DTN Bundle
Protocol as your MAMS transport protocol. This is one of the main reasons
that TCP, for example, is not a particularly good choice as a MAMS transport
protocol: the asymmetry of connect/accept makes this kind of echoing complex to
implement.<br>
<br>
At minimum (I now realize), this implementation responsibility ought to be made
explicit somewhere -- probably in 4.2.7.4.4 and 4.2.7.4.5, although I guess a
case could be made for documenting it in the Green Book instead.<br>
<br>
Alternatively, we could modify the heartbeat message to carry MAMS endpoint
name. I am not real comfortable with this, as I think it would be
perceived as adding a lot of bandwidth consumption that would be needed only in
two edge cases.<br>
<br>
A third alternative, though, might be simply to ditch the transmission of
you_are_dead messages in these cases, i.e., just ignore the heartbeats.
The only downside of this would be that the unregistered entity wouldn't
receive such prompt notification that it is not currently registered. But
eventually it would drop back into imputed termination logic and go through the
relevant re-registration procedure, so there's no real harm done.<br>
<br>
On reflection, I like this third alternative pretty well. What do you all
think?<br>
<br>
Scott<br>
<br>
</span></font></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><b><font size=2 color=black
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;font-weight:bold'>From:</span></font></b><font
size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> <a
href="mailto:sis-ams-bounces@mailman.ccsds.org">sis-ams-bounces@mailman.ccsds.org</a>
[<a href="mailto:sis-ams-bounces@mailman.ccsds.org">mailto:sis-ams-bounces@mailman.ccsds.org</a>]
<b><span style='font-weight:bold'>On Behalf Of </span></b>Ray, Timothy J.
(GSFC-583.0)<br>
<b><span style='font-weight:bold'>Sent:</span></b> Wednesday, July 09, 2008
2:51 PM<br>
<b><span style='font-weight:bold'>To:</span></b> <a
href="mailto:sis-ams@mailman.ccsds.org">sis-ams@mailman.ccsds.org</a><br>
<b><span style='font-weight:bold'>Subject:</span></b> [Sis-ams] minor
heartbeat-related issue</span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'>Dear WG members,</span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'>(Scott: thanks for posting the latest specs,
and for keeping them up-to-date.)</span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'>Here’s another issue that I’ve run
into. Perhaps I am missing something?</span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'>4.2.7.4.4 - If a server receives a
‘heartbeat’ from an unregistered registrar, it is supposed to send
back a ‘you-are-dead’. In order to do that, it will need to
know how to contact the registrar (i.e. its mams-endpoint-name). That
name is not included in the ‘heartbeat’. How can a server
send an MPDU to an unregistered registrar?</span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'>4.2.7.4.5 - Same as previous, but registrar receives a
heartbeat from an unregistered node.</span></font></p>
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