Edinburgh Regional Computing Centre For the attention of the E. C. U. C. Report on Communications SWITCHES The major changes in the network, to achieve a greater level of reliability as described in the last report, have been carried out over the summer vacation. The four main switches are now fully interlinked with 48kb/s links. The major changes involved in this reconfiguration have caused a fair amount of disruption to the service but this was restricted to the vacation period. The detailed performance figures are as follows:- a) GEC Switches S/W crashes H/W crashes Environmental Total MTBF KB GEC 4190 6 2 2 362 hours AT GEC 4190 0 5 1 604 hours AT GEC 4160 0 0 1 >1000 hours The KB switch's reliability has declined significantly because of 3 identical software crashes in the last three weeks. GEC have now supplied a patch to overcome this problem. b) TelePAC Switches A second TelePAC is now operational at KB and a third has just been installed at the Bush estate. The MTBF figures follow. S/W crashes H/W crashes Environmental Total MTBF TelePAC 1 0 2 1 1208 hours TelePAC 2 0 0 0 >1400 hours As can be seen from the figures above, the TelePACs are already behaving more reliably the the GEC switches. TelePAC 1 has 29 active lines with a load that is greater than the AT GEC 4190 although less than the KB GEC. PADS A general conversion program to switch all terminals from TCPs to PADs is now underway with the aim of phasing out most TCPs by the end of the XMAS vacation. Users are being given as much warning as possible of the exact date of the conversion. There are currently 58 PADs installed. During the summer most PADs have been upgraded allowing more addresses to be used along with the insertion of a number of patches to cure known causes of PAD crashes. In addition there has been a systematic installation of automatic backup addresses for the major hosts to minimise the effect of a line or front end failure. FRONT ENDS A total of 4 Front Ends are being brought into use on EMAS and BUSH to help spread the extra load caused by the conversion to PADs and to accomodate the extra Glasgow users. Two service Front Ends are in use on EMAS-A and work is progressing significantly to increase the network connection speed of the EMAS-A front ends. XCALL The XCALL machine has had a series of Disc faults, the effect of this on users has been minimal as the service is switched to another machine although it has been difficult to keep the address tables up to date. PSSE The service has been reasonable, although there have been a number of crashes. The cause has been identified and should be fixed in the near future. B. Gilmore 13th Oct 1986