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diff --git a/nchan.ms b/nchan.ms
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+.TL
+OpenSSH Channel Close Protocol 1.5 Implementation
+.SH
+Channel Input State Diagram
+.PS
+reset
+l=1
+s=1.2
+ellipsewid=s*ellipsewid
+boxwid=s*boxwid
+ellipseht=s*ellipseht
+S1: ellipse "INPUT" "OPEN"
+move right 2*l from last ellipse.e
+S4: ellipse "INPUT" "CLOSED"
+move down l from last ellipse.s
+S3: ellipse "INPUT" "WAIT" "OCLOSED"
+move down l from 1st ellipse.s
+S2: ellipse "INPUT" "WAIT" "DRAIN"
+arrow "" "rcvd OCLOSE/" "shutdown_read" "send IEOF" from S1.e to S4.w
+arrow "ibuf_empty/" "send IEOF" from S2.e to S3.w
+arrow from S1.s to S2.n
+box invis "read_failed/" "shutdown_read" with .e at last arrow.c
+arrow  from S3.n to S4.s
+box invis "rcvd OCLOSE/" "-" with .w at last arrow.c
+ellipse wid .9*ellipsewid ht .9*ellipseht at S4
+arrow "start" "" from S1.w+(-0.5,0) to S1.w
+.PE
+.SH
+Channel Output State Diagram
+.PS
+S1: ellipse "OUTPUT" "OPEN"
+move right 2*l from last ellipse.e
+S3: ellipse "OUTPUT" "WAIT" "IEOF"
+move down l from last ellipse.s
+S4: ellipse "OUTPUT" "CLOSED"
+move down l from 1st ellipse.s
+S2: ellipse "OUTPUT" "WAIT" "DRAIN"
+arrow "" "write_failed/" "shutdown_write" "send OCLOSE" from S1.e to S3.w
+arrow "obuf_empty ||" "write_failed/" "shutdown_write" "send OCLOSE" from S2.e to S4.w
+arrow from S1.s to S2.n
+box invis "rcvd IEOF/" "-" with .e at last arrow.c
+arrow from S3.s to S4.n
+box invis "rcvd IEOF/" "-" with .w at last arrow.c
+ellipse wid .9*ellipsewid ht .9*ellipseht at S4
+arrow "start" "" from S1.w+(-0.5,0) to S1.w
+.PE
+.SH
+Notes
+.PP
+The input buffer is filled with data from the socket
+(the socket represents the local comsumer/producer of the
+forwarded channel).
+The data is then sent over the INPUT-end of the channel to the
+remote peer.
+Data sent by the peer is received on the OUTPUT-end,
+saved in the output buffer and written to the socket.
+.PP
+If the local protocol instance has forwarded all data on the
+INPUT-end of the channel, it sends an IEOF message to the peer.
+If the peer receives the IEOF and has comsumed all
+data he replies with an OCLOSE.
+When the local instance receives the OCLOSE
+he considers the INPUT-half of the channel closed.
+The peer has his OUTOUT-half closed.
+.PP
+A channel can be deallocated by a protocol instance
+if both the INPUT- and the OUTOUT-half on his
+side of the channel are closed.
+Note that when an instance is unable to comsume the
+received data, he is permitted to send an OCLOSE
+before the matching IEOF is received.