[dahdi-commits] tzafrir: linux/trunk r5738 - /linux/trunk/README

[SVN commits to the DAHDI project]

Author: tzafrir
Date: Mon Jan 19 11:17:38 2009
New Revision: 5738

URL: http://svn.digium.com/svn-view/dahdi?view=rev&rev=5738
Log:
Document alarm types, based on jsmith's post on asterisk-users.

Modified:
    linux/trunk/README

Modified: linux/trunk/README
URL: http://svn.digium.com/svn-view/dahdi/linux/trunk/README?view=diff&rev=5738&r1=5737&r2=5738
==============================================================================
--- linux/trunk/README (original)
+++ linux/trunk/README Mon Jan 19 11:17:38 2009
@@ -445,6 +445,72 @@
 slightly confusing in the code, but it is useful for writing code that works
 with all versions of DAHDI. 
 
+
+Alarm Types
+~~~~~~~~~~~
+An alarm indicates that a port is not available for some reason. Thus it
+is probably not a good idea to try to call out through it.
+
+Red Alarm
+^^^^^^^^^
+Your T1/E1 port will go into red alarm when it maintain synchronization
+with the remote switch.  A red alarm typically indicates either a
+physical wiring problem, loss of connectivity, or a framing and/or
+line-coding mismatch with the remote switch.  When your T1/E1 port loses
+sync, it will transmit a yellow alarm to the remote switch to indicate
+that it's having a problem receiving signal from the remore switch.
+
+The easy way to remember this is that the R in red stands for "right
+here" and "receive"... indicating that we're having a problem right here
+receiving the signal from the remote switch.
+
+
+Yellow Alarm 
+^^^^^^^^^^^^
+(RAI -- Remote Alarm Indication)
+
+Your T1/E1 port will go into yellow alarm when it receives a signal from
+the remote switch that the port on that remote switch is in red alarm.
+This essentially means that the remote switch is not able to maintain
+sync with you, or is not receiving your transmission.  
+
+The easy way to remember this is that the Y in yellow stands for 
+"yonder"... indicating that the remote switch (over yonder) isn't able 
+to see what you're sending.
+
+
+Blue Alarm
+^^^^^^^^^^
+(AIS -- Alarm Indication Signal)
+
+Your T1/E1 port will go into blue alarm when it receives all unframed 1s
+on all timeslots from the remote switch.  This is a special signal to
+indicate that the remote switch is having problems with it's upstream
+connection.  As far as I know, dahdi_tool/zttool and Asterisk don't
+correctly indicate a blue alarm (at least I've never seen them indicate
+one).  The easy way to remember this is that streams are blue, so a blue
+alarm indicates a problem upstream from the switch you're connected to.
+
+
+Recovering from Alarm
+^^^^^^^^^^^^^^^^^^^^^
+TODO: explain.
+
+
+Loopback
+^^^^^^^^
+Not really an alarm. Indicates that a span is not available, as the port 
+is in either a local or remote loopback mode.
+
+
+Not Open
+^^^^^^^^
+Something is not connected. Used by e.g. the drivers of the Astribank to
+indicate a span that belongs to a device that has been disconnected 
+but is still being used by userspace programs and thus can't e
+destroyed.
+
+
 License
 -------
 This package is distributed under the terms of the GNU General Public License