📄 rfc1030.txt
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As far as future directions of research into NETBLT, one important area needs to be explored. A series of algorithms need to be developed to allow dynamic selection and control of NETBLT's transmission parameters (burst size, burst interval, and number of outstanding buffers). Ideally, this dynamic control will not require any information from outside sources such as gateways; instead, NETBLT processes will use end-to-end information in order to make transmission rate decisions in the face of noisy channels and network congestion. Some research on dynamic rate control is taking place now, but much more work needs done before the results can be integrated into NETBLT.M. Lambert [Page 11] RFC 1030 Testing the NETBLT Protocol November 1987I. Wideband Bandwidth Analysis Although the raw bandwidth of the Wideband Network is 3 megabits per second, currently only about 1 megabit per second of it is available to transmit data. The large amount of overhead is due to the channel control strategy (which uses a fixed-width control subframe based on the maximum number of stations sharing the channel) and the low- performance BIO interface between BBN's BSAT (Butterfly Satellite Interface) and Linkabit's ESI (Earth Station Interface). Higher- performance BSMI interfaces are soon to be installed in all Wideband sites, which should improve the amount of available bandwidth. Bandwidth on the Wideband network is divided up into frames, each of which has multiple subframes. A frame is 32768 channel symbols, at 2 bits per symbol. One frame is available for transmission every 21.22 milliseconds, giving a raw bandwidth of 65536 bits / 21.22 ms, or 3.081 megabits per second. Each frame contains two subframes, a control subframe and a data subframe. The control subframe is subdivided into ten slots, one per earth station. Control information takes up 200 symbols per station. Because the communications interface between BSAT and ESI only runs at 2 megabits per second, there must be a padding interval of 1263 symbols between each slot of information, bringing the total control subframe size up to 1463 symbols x 10 stations, or 14630 symbols. The data subframe then has 18138 symbols available. The maximum datagram size is currently expressed as a 14-bit quantity, further dropping the maximum amount of data in a frame to 16384 symbols. After header information is taken into account, this value drops to 16,036 symbols. At 2 bits per symbol, using a 3/4 coding rate, the actual amount of usable data in a frame is 24,054 bits, or approximately 3006 bytes. Thus the theoretical usable bandwidth is 24,054 bits every 21.22 milliseconds, or 1.13 megabits per second. Since the NETBLT implementations are running on Ethernet LANs gatewayed to the Wideband network, the 3006 bytes per channel frame of usable bandwidth translates to two maximum-sized (1500 bytes) Ethernet packets per channel frame, or 1.045 megabits per second.M. Lambert [Page 12] RFC 1030 Testing the NETBLT Protocol November 1987II. Detailed Proteon Ring LAN Test Results Following is a table of some of the test results gathered from testing NETBLT between two IBM PC/ATs on a Proteon Token Ring LAN. The table headers have the following definitions: BS/BI burst size in packets and burst interval in milliseconds PSZ number of bytes in DATA/LDATA packet data segment BFSZ number of bytes in NETBLT buffer XFSZ number of kilobytes in transfer NBUFS number of outstanding buffers #LOSS number of data packets lost #RXM number of data packets retransmitted DTMOS number of data timeouts on receiving end SPEED steady-state throughput in megabits per secondM. Lambert [Page 13] RFC 1030 Testing the NETBLT Protocol November 1987 BS/BI PSZ BFSZ XFSZ NBUFS #LOSS #RXM DTMOS SPEED 5/25 1438 14380 1438 1 0 0 0 1.45 5/25 1438 14380 1438 1 0 0 0 1.45 5/30 1438 14380 1438 1 0 0 0 1.45 5/30 1438 14380 1438 1 0 0 0 1.45 5/35 1438 14380 1438 1 0 0 0 1.40 5/35 1438 14380 1438 1 0 0 0 1.41 5/40 1438 14380 1438 1 0 0 0 1.33 5/40 1438 14380 1438 1 0 0 0 1.33 5/25 1438 14380 1438 2 0 0 0 1.62 5/25 1438 14380 1438 2 0 0 0 1.61 5/30 1438 14380 1438 2 0 0 0 1.60 5/30 1438 14380 1438 2 0 0 0 1.61 5/34 1438 14380 1438 2 0 0 0 1.59 5/35 1438 14380 1438 2 0 0 0 1.58 5/25 1990 19900 1990 1 0 0 0 1.48 5/25 1990 19900 1990 1 0 0 0 1.49 5/30 1990 19900 1990 1 0 0 0 1.48 5/30 1990 19900 1990 1 0 0 0 1.48 5/35 1990 19900 1990 1 0 0 0 1.49 5/35 1990 19900 1990 1 0 0 0 1.48 5/40 1990 19900 1990 1 0 0 0 1.49 5/40 1990 19900 1990 1 0 0 0 1.49 5/45 1990 19900 1990 1 0 0 0 1.45 5/45 1990 19900 1990 1 0 0 0 1.46 5/25 1990 19900 1990 2 0 0 0 1.75 5/25 1990 19900 1990 2 0 0 0 1.75 5/30 1990 19900 1990 2 0 0 0 1.74 5/30 1990 19900 1990 2 0 0 0 1.75 5/35 1990 19900 1990 2 0 0 0 1.74 5/35 1990 19900 1990 2 0 0 0 1.74 5/40 1990 19900 1990 2 0 0 0 1.75 5/40 1990 19900 1990 2 0 0 0 1.74 5/43 1990 19900 1990 2 0 0 0 1.75 5/43 1990 19900 1990 2 0 0 0 1.74 5/43 1990 19900 1990 2 0 0 0 1.75 5/44 1990 19900 1990 2 0 0 0 1.73 5/44 1990 19900 1990 2 0 0 0 1.72 5/45 1990 19900 1990 2 0 0 0 1.70 5/45 1990 19900 1990 2 0 0 0 1.72M. Lambert [Page 14] RFC 1030 Testing the NETBLT Protocol November 1987III. Detailed Ethernet LAN Testing Results Following is a table of some of the test results gathered from testing NETBLT between two IBM PC/ATs on an Ethernet LAN. See previous appendix for table header definitions. BS/BI PSZ BFSZ XFSZ NBUFS #LOSS #RXM DTMOS SPEED 5/30 1438 14380 1438 1 9 9 6 1.42 5/30 1438 14380 1438 1 2 2 2 1.45 5/30 1438 14380 1438 1 5 5 4 1.44 5/35 1438 14380 1438 1 7 7 7 1.38 5/35 1438 14380 1438 1 6 6 5 1.38 5/40 1438 14380 1438 1 48 48 44 1.15 5/40 1438 14380 1438 1 50 50 38 1.17 5/40 1438 14380 1438 1 13 13 11 1.28 5/40 1438 14380 1438 1 7 7 5 1.30 5/30 1438 14380 1438 2 206 206 198 0.995 5/30 1438 14380 1438 2 213 213 198 0.994 5/40 1438 14380 1438 2 117 121 129 1.05 5/40 1438 14380 1438 2 178 181 166 0.892 5/40 1438 14380 1438 2 135 138 130 1.03 5/45 1438 14380 1438 2 57 57 52 1.12 5/45 1438 14380 1438 2 97 97 99 1.02 5/45 1438 14380 1438 2 62 62 51 1.09 5/15 512 10240 2048 1 6 6 4 0.909 5/15 512 10240 2048 1 10 11 7 0.907 5/18 512 10240 2048 1 11 11 8 0.891 5/18 512 10240 2048 1 5 5 9 0.906 5/19 512 10240 2048 1 3 3 3 0.905 5/19 512 10240 2048 1 8 8 7 0.898 5/20 512 10240 2048 1 7 7 4 0.876 5/20 512 10240 2048 1 11 12 5 0.871 5/20 512 10240 2048 1 8 9 5 0.874 5/30 512 10240 2048 2 113 116 84 0.599 5/30 512 10240 2048 2 20 20 14 0.661 5/30 512 10240 2048 2 49 50 40 0.638M. Lambert [Page 15] RFC 1030 Testing the NETBLT Protocol November 1987IV. Detailed Wideband Network Testing Results Following is a table of some of the test results gathered from testing NETBLT between an IBM PC/AT and a SUN-3 using the Wideband satellite network. See previous appendix for table header definitions. BS/BI PSZ BFSZ XFSZ NBUFS #LOSS #RXM SPEED 5/90 1400 14000 500 22 9 10 0.584 5/90 1400 14000 500 22 12 12 0.576 5/90 1400 14000 500 22 3 3 0.591 5/90 1420 14200 500 22 12 12 0.591 5/90 1420 14200 500 22 6 6 0.600 5/90 1430 14300 500 22 9 10 0.600 5/90 1430 14300 500 22 15 15 0.591 5/90 1430 14300 500 22 12 12 0.590 5/90 1432 14320 716 22 13 16 0.591 5/90 1434 14340 717 22 33 147 0.483 5/90 1436 14360 718 22 25 122 0.500 5/90 1436 14360 718 22 25 109 0.512 5/90 1436 14360 718 22 28 153 0.476 5/90 1438 14380 719 22 6 109 0.533 5/80 1432 14320 716 22 56 68 0.673 5/80 1432 14320 716 22 14 14 0.666 5/80 1432 14320 716 22 15 16 0.661 5/60 1432 14320 716 22 19 22 0.856 5/60 1432 14320 716 22 84 95 0.699 5/60 1432 14320 716 22 18 21 0.871 5/60 1432 14320 716 30 38 40 0.837 5/60 1432 14320 716 30 25 26 0.869 5/55 1432 14320 716 22 13 13 0.935 5/55 1432 14320 716 22 25 25 0.926 5/55 1432 14320 716 22 25 25 0.926 5/55 1432 14320 716 22 20 20 0.932 5/55 1432 14320 716 22 17 19 0.934 5/55 1432 14320 716 22 13 14 0.942M. 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