Rename HPN-README to the openssh normal README.hpn form and bring in

bz's rework of the document.

README.hpn

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+Notes:
+
+NONE CIPHER:
+  To use the NONE option you must have the NoneEnabled switch set on the server
+  and you MUST have *both* NoneEnabled and NoneSwitch set to yes on the client.
+  The NONE feature works with ALL ssh subsystems (as far as we can tell)
+  as long as there is no tty allocated.
+  If a user uses the -T switch to prevent a tty being created the NONE cipher
+  will be disabled. 
+
+
+PERFORMANCE:
+  The performance increase will only be as good as the network and TCP stack
+  tuning on the reciever side of the connection allows.  As a rule of thumb a
+  user will need at least 10Mb/s connection with a 100ms RTT to see a doubling
+  of performance.
+  The HPN-SSH home page  http://www.psc.edu/networking/projects/hpn-ssh
+  describes this in greater detail. 
+
+
+BUFFER SIZES:
+- if HPN is disabled the receive buffer size will be set to the OpenSSH default
+  of 64K.
+
+- if a HPN system connects to a non-HPN system the receive buffer will
+  be set to the HPNBufferSize value. The default is 2MB but user adjustable.
+
+- If a HPN to HPN connection is established a number of different things might
+  happen based on the user options and conditions. 
+
+  Conditions: HPNBufferSize NOT Set, TCPRcvBufPoll enabled, TCPRcvBuf NOT Set 
+  Result: HPN Buffer Size = up to 64MB 
+    This is the default state.  The HPN buffer size will grow to a maximum of
+    64MB as the TCP receive buffer grows.  The maximum HPN Buffer size of 64MB
+    is geared towards 10GigE transcontinental connections. 
+
+  Conditions: HPNBufferSize NOT Set, TCPRcvBufPoll disabled, TCPRcvBuf NOT Set
+  Result: HPN Buffer Size = TCP receive buffer value. 
+    Users on non-autotuning systesm should disable TCPRcvBufPoll in the 
+    ssh_cofig and sshd_config
+
+  Conditions: HPNBufferSize SET, TCPRcvBufPoll disabled, TCPRcvBuf NOT Set
+  Result: HPN Buffer Size = minmum of TCP receive buffer and HPNBufferSize. 
+    This would be the system defined TCP receive buffer (RWIN).
+
+  Conditions: HPNBufferSize SET, TCPRcvBufPoll disabled, TCPRcvBuf SET
+  Result: HPN Buffer Size = minmum of TCPRcvBuf and HPNBufferSize. 
+    Generally there is no need to set both.
+
+  Conditions: HPNBufferSize SET, TCPRcvBufPoll enabled, TCPRcvBuf NOT Set
+  Result: HPN Buffer Size = grows to HPNBufferSize
+    The buffer will grow up to the maximum size specified here. 
+
+  Conditions: HPNBufferSize SET, TCPRcvBufPoll enabled, TCPRcvBuf SET
+  Result: HPN Buffer Size = minmum of TCPRcvBuf and HPNBufferSize. 
+    Generally there is no need to set both of these, especially on autotuning 
+    systems. However, if the users wishes to override the autotuning this would
+    be one way to do it.
+
+  Conditions: HPNBufferSize NOT Set, TCPRcvBufPoll enabled, TCPRcvBuf SET
+  Result: HPN Buffer Size = TCPRcvBuf. 
+   This will override autotuning and set the TCP recieve buffer to the user
+   defined value.
+
+
+HPN SPECIFIC CONFIGURATION OPTIONS:
+
+- HPNEnabled=[yes/no] client/server
+  In some situations, such as transfers on a local area network, the impact 
+  of the HPN code produces a net decrease in performance.  In these cases it is 
+  helpful to disable the HPN functionality. By default HPNEnabled is set to yes. 
+
+- HPNBufferSize=[int]KB client/server
+  This is the default buffer size the HPN functionality uses when interacting
+  with non-HPN SSH installations.  Conceptually this is similar to the TcpRcvBuf
+  option as applied to the internal SSH flow control.  This value can range from 
+  1KB to 64MB (1-65536).  Use of oversized or undersized buffers can cause
+  performance problems depending on the roud trip time of the network path.
+  The default size of this buffer is 2MB.
+
+- TcpRcvBufPoll=[yes/no] client/server
+  Enable or disable the polling of the TCP receive buffer through the life 
+  of the connection.  You would want to make sure that this option is enabled 
+  for systems making use of autotuning kernels (linux 2.4.24+, 2.6, MS Vista,
+  FreeBSD 7.x and later). Default is yes.
+
+- TcpRcvBuf=[int]KB client
+  Set the TCP socket receive buffer to n Kilobytes.  It can be set up to the 
+  maximum socket size allowed by the system.  This is useful in situations where 
+  the TCP receive window is set low but the maximum buffer size is set higher
+  (as is typical).  This works on a per TCP connection basis.  You can also use
+  this to artifically limit the transfer rate of the connection.  In these cases
+  the throughput will be no more than n/RTT.  The minimum buffer size is 1KB. 
+  Default is the current system wide TCP receive buffer size.
+
+- NoneEnabled=[yes/no] client/server
+  Enable or disable the use of the None cipher.  Care must always be used when
+  enabling this as it will allow users to send data in the clear.  However, it
+  is important to note that authentication information remains encrypted even
+  if this option is enabled.  Set to no by default.
+
+- NoneSwitch=[yes/no] client
+  Switch the encryption cipher being used to the None cipher after
+  authentication takes place.  NoneEnabled must be enabled on both the client
+  and server side of the connection.  When the connection switches to the NONE
+  cipher a warning is sent to STDERR.  The connection attempt will fail with an
+  error if a client requests a NoneSwitch from the server that does not
+  explicitly have NoneEnabled set to yes.
+  Note: The NONE cipher cannot be used in interactive (shell) sessions and it
+  will fail silently.  Set to no by default.
+
+
+CREDITS:
+
+  This patch was conceived, designed, and led by Chris Rapier (rapier@psc.edu)
+  The majority of the actual coding for versions up to HPN12v1 was performed
+  by Michael Stevens (mstevens@andrew.cmu.edu).
+  The MT-AES-CTR cipher was implemented by Ben Bennet (ben@psc.edu).
+  This work was financed, in part, by Cisco System, Inc., the National Library
+  of Medicine, and the National Science Foundation.