1Notes: 2 3NONE CIPHER: 4 To use the NONE option you must have the NoneEnabled switch set on the server 5 and you MUST have *both* NoneEnabled and NoneSwitch set to yes on the client. 6 The NONE feature works with ALL ssh subsystems (as far as we can tell) 7 as long as there is no tty allocated. 8 If a user uses the -T switch to prevent a tty being created the NONE cipher 9 will be disabled. 10 11 12PERFORMANCE: 13 The performance increase will only be as good as the network and TCP stack 14 tuning on the reciever side of the connection allows. As a rule of thumb a 15 user will need at least 10Mb/s connection with a 100ms RTT to see a doubling 16 of performance. 17 The HPN-SSH home page http://www.psc.edu/networking/projects/hpn-ssh 18 describes this in greater detail. 19 20 21BUFFER SIZES: 22- if HPN is disabled the receive buffer size will be set to the OpenSSH default 23 of 64K. 24 25- if a HPN system connects to a non-HPN system the receive buffer will 26 be set to the HPNBufferSize value. The default is 2MB but user adjustable. 27 28- If a HPN to HPN connection is established a number of different things might 29 happen based on the user options and conditions. 30 31 Conditions: HPNBufferSize NOT Set, TCPRcvBufPoll enabled, TCPRcvBuf NOT Set 32 Result: HPN Buffer Size = up to 64MB 33 This is the default state. The HPN buffer size will grow to a maximum of 34 64MB as the TCP receive buffer grows. The maximum HPN Buffer size of 64MB 35 is geared towards 10GigE transcontinental connections. 36 37 Conditions: HPNBufferSize NOT Set, TCPRcvBufPoll disabled, TCPRcvBuf NOT Set 38 Result: HPN Buffer Size = TCP receive buffer value. 39 Users on non-autotuning systesm should disable TCPRcvBufPoll in the 40 ssh_cofig and sshd_config 41 42 Conditions: HPNBufferSize SET, TCPRcvBufPoll disabled, TCPRcvBuf NOT Set 43 Result: HPN Buffer Size = minmum of TCP receive buffer and HPNBufferSize. 44 This would be the system defined TCP receive buffer (RWIN). 45 46 Conditions: HPNBufferSize SET, TCPRcvBufPoll disabled, TCPRcvBuf SET 47 Result: HPN Buffer Size = minmum of TCPRcvBuf and HPNBufferSize. 48 Generally there is no need to set both. 49 50 Conditions: HPNBufferSize SET, TCPRcvBufPoll enabled, TCPRcvBuf NOT Set 51 Result: HPN Buffer Size = grows to HPNBufferSize 52 The buffer will grow up to the maximum size specified here. 53 54 Conditions: HPNBufferSize SET, TCPRcvBufPoll enabled, TCPRcvBuf SET 55 Result: HPN Buffer Size = minmum of TCPRcvBuf and HPNBufferSize. 56 Generally there is no need to set both of these, especially on autotuning 57 systems. However, if the users wishes to override the autotuning this would 58 be one way to do it. 59 60 Conditions: HPNBufferSize NOT Set, TCPRcvBufPoll enabled, TCPRcvBuf SET 61 Result: HPN Buffer Size = TCPRcvBuf. 62 This will override autotuning and set the TCP recieve buffer to the user 63 defined value. 64 65 66HPN SPECIFIC CONFIGURATION OPTIONS: 67 68- HPNDisabled=[yes/no] client/server 69 In some situations, such as transfers on a local area network, the impact 70 of the HPN code produces a net decrease in performance. In these cases it is 71 helpful to disable the HPN functionality. By default HPNDisabled is set to no. 72 73- HPNBufferSize=[int]KB client/server 74 This is the default buffer size the HPN functionality uses when interacting 75 with non-HPN SSH installations. Conceptually this is similar to the TcpRcvBuf 76 option as applied to the internal SSH flow control. This value can range from 77 1KB to 64MB (1-65536). Use of oversized or undersized buffers can cause 78 performance problems depending on the roud trip time of the network path. 79 The default size of this buffer is 2MB. 80 81- TcpRcvBufPoll=[yes/no] client/server 82 Enable or disable the polling of the TCP receive buffer through the life 83 of the connection. You would want to make sure that this option is enabled 84 for systems making use of autotuning kernels (linux 2.4.24+, 2.6, MS Vista, 85 FreeBSD 7.x and later). Default is yes. 86 87- TcpRcvBuf=[int]KB client 88 Set the TCP socket receive buffer to n Kilobytes. It can be set up to the 89 maximum socket size allowed by the system. This is useful in situations where 90 the TCP receive window is set low but the maximum buffer size is set higher 91 (as is typical). This works on a per TCP connection basis. You can also use 92 this to artifically limit the transfer rate of the connection. In these cases 93 the throughput will be no more than n/RTT. The minimum buffer size is 1KB. 94 Default is the current system wide TCP receive buffer size. 95 96- NoneEnabled=[yes/no] client/server 97 Enable or disable the use of the None cipher. Care must always be used when 98 enabling this as it will allow users to send data in the clear. However, it 99 is important to note that authentication information remains encrypted even 100 if this option is enabled. Set to no by default. 101 102- NoneSwitch=[yes/no] client 103 Switch the encryption cipher being used to the None cipher after 104 authentication takes place. NoneEnabled must be enabled on both the client 105 and server side of the connection. When the connection switches to the NONE 106 cipher a warning is sent to STDERR. The connection attempt will fail with an 107 error if a client requests a NoneSwitch from the server that does not 108 explicitly have NoneEnabled set to yes. 109 Note: The NONE cipher cannot be used in interactive (shell) sessions and it 110 will fail silently. Set to no by default. 111 112 113CREDITS: 114 115 This patch was conceived, designed, and led by Chris Rapier (rapier@psc.edu) 116 The majority of the actual coding for versions up to HPN12v1 was performed 117 by Michael Stevens (mstevens@andrew.cmu.edu). 118 The MT-AES-CTR cipher was implemented by Ben Bennet (ben@psc.edu). 119 This work was financed, in part, by Cisco System, Inc., the National Library 120 of Medicine, and the National Science Foundation. 121