From: SMTP%"brydon@dsn.SINet.slb.com" 9-SEP-1993 11:38:08.39 To: EVERHART CC: Subj: Re: ethermon From: brydon@ASLVX1.SUGAR-LAND.ANA.SLB.COM (Harvey Brydon (918)250-4312) X-Newsgroups: comp.os.vms Subject: Re: ethermon Date: 8 Sep 1993 12:50:58 GMT Organization: Dowell Schlumberger, Tulsa, Oklahoma Lines: 40 Message-ID: <26kkfi$l93@sndsu1.sinet.slb.com> Reply-To: brydon@dsn.SINet.slb.com NNTP-Posting-Host: 163.185.21.11 To: Info-VAX@KL.SRI.COM X-Gateway-Source-Info: USENET In article <930903094138.a2@arisia.gce.com>, "Glenn C. Everhart" writes: >[...] >There is however a circumstance one should be aware of: the DEC >ethernet driver has a limit on the number of types of packages >it can handle at a time. Some years ago this got more fully discussed >by people running decnet, tcp/ip, lat, and several other networks >and running out of these "slots". The number 5 sticks in my mind as >the most protocols the driver can take, but the details have become >fuzzy. It may be though that running ethermon in a case where one >has "used up" the driver could cause one of the other connections >to become inoperative. (Maybe someone will recall more about this, >too. I don't have the last 5 years of info-vax notes handy anymore >to search through...) I think the detail you are thinking of is the maximum number of multicast addresses the ethernet controller can handle. Whenever you add an ethernet based communications package to a vax, it typically uses one or more multicast (or broadcast) addresses (package = DECnet end node, DECnet routing, LAT, LAVC, TCP/IP, ...). The ethernet controller can be set up to capture packets of that multicast address and interrupt the CPU for servicing. There are a certain number of slots available that (I think) varies from controller type to controller type. One of the slots must contain the ethernet physical address for the controller. I have in front of me the manual for the DELQA, which says that it has 14 slots (therefore 13 available for multicast addresses). If you have so many packages on your system that you are watching for the more than the number of slots allotted, the controller does not watch for any multicast packets of particular type, but instead interrupts the CPU on every multicast/broadcast packet and lets the CPU throw away what it doesn't want. If you have a lot of ethernet networking gizmos on your system and exceed this number, your CPU can spend a lot of time in Interrupt and Kernel modes. There is an unsupported undocumented command in SDA "Show decnet/datalink" that will tell you a number of details about DECnet on your system, including which multicast addresses the system is watching for. _______________________________________________________________ Harvey Brydon | Internet: brydon@dsn.SINet.slb.com Dowell Schlumberger | P.O.T.S.: (918)250-4312 Most of my grey wall is orange and blue.