tpmsph@ecsvax.UUCP (Thomas P. Morris) (02/09/88)
Our site is looking into the purchase of some TCP-IP terminal servers, to be connected to our VAX VMS 8530, using the Wollongong TCP-IP (if we cannot find any IVECS-type BI-bus processor board). We have heard from other sites that there is `some' overhead in running TCP-IP terminal server connections using the TWG software. Claims about CPU overhead have varied wildly. Can anyone who is actually using TWG TCP-IP and VMS with BRIDGE or Micom or XYPLEX or DEVELNET servers please comment? "Hard" data would be much preferred. Something like "The cpu overhead is x%/connected process" or "we find that xx connections use yy% cpu just for communications via TCP-IP". Thanx in advance. Please reply via mail. I'll summarize and post back to the net. Tom Morris UNC School of Public Health BITNET: TOM@UNCSPHVX USENET: ...!mcnc!ecsvax!tpmsph
lamaster@ames.arpa (Hugh LaMaster) (02/10/88)
In article <4582@ecsvax.UUCP> tpmsph@ecsvax.UUCP (Thomas P. Morris) writes: >Our site is looking into the purchase of some TCP-IP >terminal servers, to be connected to our VAX VMS 8530, >using the Wollongong TCP-IP (if we cannot find any >IVECS-type BI-bus processor board). I'm not sure what an IVECS board is. The following tests were done on an 8650, VMS 4.5, recent Wollongong (Not sure of version, but it is much improved over the earlier, much maligned, versions.) I'm not sure which DEC Ethernet board we are using either. BUT ... > >We have heard from other sites that there is `some' >overhead in running TCP-IP terminal server connections >using the TWG software. Claims about CPU overhead have >varied wildly. Can anyone who is actually using TWG >TCP-IP and VMS with BRIDGE or Micom or XYPLEX or DEVELNET >servers please comment? > > "Hard" data would be much preferred. Something like >"The cpu overhead is x%/connected process" or "we find that >xx connections use yy% cpu just for communications via TCP-IP". I have measured CPU overhead to: Ultrix, SunOS 3.2, and Annex Terminal Servers (X2.1.8). Unlike in the past, before TWG was so much improved, I am now unable to discern ANY difference in CPU overhead between a TWG Telnet Connection and a DM- type connection. Recent measurements showed that a TYPE of a large file on a machine with few interactive users and some idle time (batch jobs off and on, which didn't seem to have an effect on the test) produced about the same total usage whether going to the network or to a terminal. (Speed scaled appropriately). I haven't observed horrendous overheads due to terminals since we got rid of our DZ-11's (I think that is what the interrupt per character boards were). If you have many many low CPU usage terminals connected, and every last CPU cycle counts, you should probably do a formal study. If, on the other hand, you just want to make sure that you won't lose half the machine because of terminal servers, it doesn't look like an issue anymore (yes, it was in the past). The total throughput of an 8650 appears to be about 12-14KBytes/sec from TYPE, which may be doing line at a time output - 2KBytes/sec/MIPS. In either case, there is substantial overhead from doing terminal output, but it is about the same in either case. If most of your usage is in EDT (or its successors) there may be special efficiency issues- the Annex is supposed to put multiple characters from cursor control in one packet. Does a DMZ produce only one interrupt in that case? I suspect you get three, so potentially the terminal server could be more efficient. etc. etc. (By the way, the Annex has been up for 112 days -probably our last power outage. It has been reliable.)