To: T. Milligan CC: N. Housley Date: April 29, 1983 Abstract: This report yields the results of testing the KERMIT file transfer protocol between the SCS Vax, and the DEC-10. The testing of the protocol involved o varying the size of the files transmitted, o varying the line speed {300/1200}, o varying the quality of the line {null modem/telephone}. The transfers were analyzed on the basis of o effective baud rate, o line utilization, o errors in transferred files. - 2 - Introduction : Kermit ("KL-10 Error-free Reciprocol Microcomputer InterChange over TTY-Lines") as the acronym implies, is a means for allowing error-free transfer of files between computers over normal terminal communication lines. The protocol was originally designed for Digitial Equipment's DECSYSTEM-20 KL 10 machines, but within recent years has been extended to work on a variety of other processors; both mainframes, (Vax, IBM/VM, etc.) and micros (CP/M systems, Apples, ...). Kermit is a simple, portable, half-duplex file transfer protocol. The transfer algorithm does not rely on fancy scheduling schemes, multiplexed physical links, multichannel logical links, data compression, routing, etc. A kermit packet can range in size from 8 bytes, to 94 bytes (data packets run from 9 - 94 bytes, while ACK/NAK/BAD packets are 8 bytes in length). Results : The testing of Kermit was performed over two days, during periods of moderate to high system load on both the SCS Vax, and the DEC-10. In total over twenty files were transfered; ten files were transmitted at 300 baud, and the other ten at 1200 baud. The file sizes ranged from 3,000 to 25,000 bytes. A brief summary of the results follow: i) 300 Baud Transfers : * 1. Average Line Utilization : a) null modem line (VAX-DEC10) - 72.3 %, (DEC10-VAX) - 73.0 %, b) telephone line (VAX-DEC10) - 72.1 %. 2. Average Effective Baud Rate : a) null modem line (VAX-DEC10) - 216 baud (DEC10-VAX) - 219 " b) telephone line (VAX-DEC10) - 216 " ** 3. Percentage of Machine consumed during transfer : a) VAX/VMS - 3.0 % to 5.0 % b) DEC10 - 0.5 % to 1.0 % 4. Flawless transmission during all test cases. ---------------------- * - The variation between the null modem and the telephone line could be the result of turn-around time in line, distance, etc. ** - The VAX does not have a front-end for DH/DZ terminal lines; hence the CPU utilization is bogged down fielding byte interrupts. - 3 - ii) 1200 Baud Transfers : 1. Average Line Utilization : a) null modem line (VAX-DEC10) - 65.8 %, (DEC10-VAX) - 64.2 %, b) telephone line (VAX-DEC10) - 64.5 %. 2. Average Effective Baud Rate : a) null modem line (VAX-DEC10) - 789 baud (DEC10-VAX) - 770 " b) telephone line (VAX-DEC10) - 774 " 3. Percentage of Machine consumed during transfer : a) VAX/VMS - 4.0 % to 5.0 % b) DEC10 - 0.5 % to 1.0 % 4. Flawless transmission during all test cases. (Please examine Table's 1 through 4 for a more detailed analysis of each file transfer). Columbia University (implementors of Kermit) indicated that the Kermit protocol would yield line utilizations of 70 % or less at twelve hundred baud. The statistics derived from our testing apparently verify this observation. - 4 - TABLE 1 Kermit Setup Parameters: kermit packet size = 94 bytes send/receive timeout = 20 seconds line speed = 300 baud Files Transferred: file no. file size 1 46 blocks 2 49 blocks 3 9 blocks 4 6 blocks Transfer Data Statistics (VAX to DEC-10): File 1 File 2 File 3 File 4 Packets Sent = 315 325 57 40 ACK's = 315 325 57 40 NAK's = 0 0 0 0 BAD = 0 0 0 0 Chars. Data Sent = 22510 23437 3962 2541 Total Chars Sent = 28079 26940 4819 3274 Overhead on Send = 24 % 23 % 21 % 28 % Packets Received = 314 325 57 40 Chars. Data Recvd = 0 0 0 0 Total Chars Recvd = 1581 1631 291 206 Overhead on Recv. = 100 % 100 % 100 % 100 % Run Time (seconds) Null Modem = 1032 1065 179 121 Telephone = 1037 1067 179 122 Effective Baud Rate Null Modem = 218 220 219 210 Telephone = 217 219 221 208 Line Utilization Null Modem = 72.7 % 73.3 % 73.0 % 70.0 % Telephone = 72.3 % 73.0 % 73.6 % 69.3 % Time of day Null Modem = 4:39 PM 4:00 PM 5:03 PM 4:59 PM Telephone = 1:40 PM 1:55 PM 1:25 PM 1:15 PM - 5 - TABLE 2 Kermit Setup Parameters: kermit packet size = 94 bytes send/receive timeout = 20 seconds line speed = 300 baud Files Transferred: file no. file size 1 46 blocks 2 49 blocks 3 9 blocks 4 6 blocks Transfer Data Statistics (DEC-10 to VAX): File 1 File 2 File 3 File 4 Packets Sent = 302 311 55 39 ACK's = 302 311 55 39 NAK's = 0 0 0 0 BAD = 0 0 0 0 Chars. Data Sent = 0 0 0 0 Total Chars Sent = 1516 1561 281 201 Overhead on Send = 100 % 100 % 100 % 100 % Packets Received = 302 311 55 39 Chars. Data Recvd = 23470 24404 4084 2668 Total Chars Recvd = 28022 28872 4809 3272 Overhead on Recv. = 19 % 18 % 17 % 22 % Run Time (seconds) Null Modem = 1048 1073 185 129 Effective Baud Rate Null Modem = 223 227 220 206 Line Utilization Null Modem = 74.3 % 75.7 % 73.3 % 68.6 % Time of day Null Modem = 3:05 PM 3:20 PM 3:00 PM 2:55 PM - 6 - TABLE 3 Kermit Setup Parameters: kermit packet size = 94 bytes send/receive timeout = 20 seconds line speed = 1200 baud Files Transferred: file no. file size 1 46 blocks 2 49 blocks 3 9 blocks 4 6 blocks Transfer Data Statistics (VAX to DEC-10): File 1 File 2 File 3 File 4 Packets Sent = 315 325 57 40 ACK's = 315 325 57 40 NAK's = 0 0 0 0 BAD = 0 0 0 0 Chars. Data Sent = 22510 23437 3962 2541 Total Chars Sent = 28079 28940 4819 3274 Overhead on Send = 24 % 23 % 21 % 20 % Packets Received = 315 325 57 40 Chars. Data Recvd = 0 0 0 0 Total Chars Recvd = 1581 1633 291 206 Overhead on Recv. = 100 % 100 % 100 % 100 % Run Time (seconds) Null Modem = 283 292 50 33 Telephone = 294 301 51 34 Effective Baud Rate Null Modem = 795 802 792 770 Telephone = 766 778 776 777 Line Utilization Null Modem = 66.3 % 66.8 % 66.0 % 64.2 % Telephone = 63.8 % 64.8 % 64.6 % 64.7 % Time of day Null Modem = 3:35 PM 3:40 PM 3:53 PM 3:56 PM Telephone = 4:45 PM 5:10 PM 5:25 PM 5:30 PM - 7 - TABLE 4 Kermit Setup Parameters: kermit packet size = 94 bytes send/receive timeout = 20 seconds line speed = 1200 baud Files Transferred: file no. file size 1 46 blocks 2 49 blocks 3 9 blocks 4 6 blocks Transfer Data Statistics (DEC-10 to VAX): File 1 File 2 File 3 File 4 Packets Sent = 302 311 55 39 ACK's = 302 311 55 39 NAK's = 0 0 0 0 BAD = 0 0 0 0 Chars. Data Sent = 0 0 0 0 Total Chars Sent = 1516 1561 281 201 Overhead on Send = 100 % 100 % 100 % 100 % Packets Received = 302 311 55 39 Chars. Data Recvd = 23470 24404 4084 2668 Total Chars Recvd = 28022 28872 4809 3272 Overhead on Recv. = 19 % 18 % 17 % 22 % Run Time (seconds) Null Modem = 286 296 53 40 Effective Baud Rate Null Modem = 820 824 770 667 Line Utilization Null Modem = 68.3 % 68.6 % 64.2 % 55.6 % Time of day Null Modem = 4:08 PM 4:00 PM 4:15 PM 4:05 PM