1Notes: 2 3PERFORMANCE: 4 The performance increase will only be as good as the network and TCP stack 5 tuning on the reciever side of the connection allows. As a rule of thumb a 6 user will need at least 10Mb/s connection with a 100ms RTT to see a doubling 7 of performance. 8 The HPN-SSH home page http://www.psc.edu/networking/projects/hpn-ssh 9 describes this in greater detail. 10 11 12BUFFER SIZES: 13- if HPN is disabled the receive buffer size will be set to the OpenSSH default 14 of 64K. 15 16- if a HPN system connects to a non-HPN system the receive buffer will 17 be set to the HPNBufferSize value. The default is 2MB but user adjustable. 18 19- If a HPN to HPN connection is established a number of different things might 20 happen based on the user options and conditions. 21 22 Conditions: HPNBufferSize NOT Set, TCPRcvBufPoll enabled, TCPRcvBuf NOT Set 23 Result: HPN Buffer Size = up to 64MB 24 This is the default state. The HPN buffer size will grow to a maximum of 25 64MB as the TCP receive buffer grows. The maximum HPN Buffer size of 64MB 26 is geared towards 10GigE transcontinental connections. 27 28 Conditions: HPNBufferSize NOT Set, TCPRcvBufPoll disabled, TCPRcvBuf NOT Set 29 Result: HPN Buffer Size = TCP receive buffer value. 30 Users on non-autotuning systesm should disable TCPRcvBufPoll in the 31 ssh_cofig and sshd_config 32 33 Conditions: HPNBufferSize SET, TCPRcvBufPoll disabled, TCPRcvBuf NOT Set 34 Result: HPN Buffer Size = minmum of TCP receive buffer and HPNBufferSize. 35 This would be the system defined TCP receive buffer (RWIN). 36 37 Conditions: HPNBufferSize SET, TCPRcvBufPoll disabled, TCPRcvBuf SET 38 Result: HPN Buffer Size = minmum of TCPRcvBuf and HPNBufferSize. 39 Generally there is no need to set both. 40 41 Conditions: HPNBufferSize SET, TCPRcvBufPoll enabled, TCPRcvBuf NOT Set 42 Result: HPN Buffer Size = grows to HPNBufferSize 43 The buffer will grow up to the maximum size specified here. 44 45 Conditions: HPNBufferSize SET, TCPRcvBufPoll enabled, TCPRcvBuf SET 46 Result: HPN Buffer Size = minmum of TCPRcvBuf and HPNBufferSize. 47 Generally there is no need to set both of these, especially on autotuning 48 systems. However, if the users wishes to override the autotuning this would 49 be one way to do it. 50 51 Conditions: HPNBufferSize NOT Set, TCPRcvBufPoll enabled, TCPRcvBuf SET 52 Result: HPN Buffer Size = TCPRcvBuf. 53 This will override autotuning and set the TCP recieve buffer to the user 54 defined value. 55 56 57HPN SPECIFIC CONFIGURATION OPTIONS: 58 59- HPNDisabled=[yes/no] client/server 60 In some situations, such as transfers on a local area network, the impact 61 of the HPN code produces a net decrease in performance. In these cases it is 62 helpful to disable the HPN functionality. By default HPNDisabled is set to no. 63 64- HPNBufferSize=[int]KB client/server 65 This is the default buffer size the HPN functionality uses when interacting 66 with non-HPN SSH installations. Conceptually this is similar to the TcpRcvBuf 67 option as applied to the internal SSH flow control. This value can range from 68 1KB to 64MB (1-65536). Use of oversized or undersized buffers can cause 69 performance problems depending on the roud trip time of the network path. 70 The default size of this buffer is 2MB. 71 72- TcpRcvBufPoll=[yes/no] client/server 73 Enable or disable the polling of the TCP receive buffer through the life 74 of the connection. You would want to make sure that this option is enabled 75 for systems making use of autotuning kernels (linux 2.4.24+, 2.6, MS Vista, 76 FreeBSD 7.x and later). Default is yes. 77 78- TcpRcvBuf=[int]KB client 79 Set the TCP socket receive buffer to n Kilobytes. It can be set up to the 80 maximum socket size allowed by the system. This is useful in situations where 81 the TCP receive window is set low but the maximum buffer size is set higher 82 (as is typical). This works on a per TCP connection basis. You can also use 83 this to artifically limit the transfer rate of the connection. In these cases 84 the throughput will be no more than n/RTT. The minimum buffer size is 1KB. 85 Default is the current system wide TCP receive buffer size. 86 87 88CREDITS: 89 90 This patch was conceived, designed, and led by Chris Rapier (rapier@psc.edu) 91 The majority of the actual coding for versions up to HPN12v1 was performed 92 by Michael Stevens (mstevens@andrew.cmu.edu). 93 The MT-AES-CTR cipher was implemented by Ben Bennet (ben@psc.edu). 94 This work was financed, in part, by Cisco System, Inc., the National Library 95 of Medicine, and the National Science Foundation. 96