matt@zeus.sbi.com (Matthew Gutherz ISG) (03/22/91)
Hello, Is there anyone out there willing to share their experiences, good or bad, with the Telebit NetBlazer. I am particularly interested in the IP connectivity on demand function. Is it able to establish a connection before a host times out the attempt? How well does it buffer packets while it is establishing the connection? Does it keep track of open connections through it so that does not cut them after a period of inactivity? Thanks Matt Gutherz Networking Mercenary
brian@telebit.com (Brian Lloyd) (04/06/91)
Well perhaps I am a bit biased but I can answer the question about how the NetBlazer works (I designed it) and I am posting this message from my home running rlogin through a NetBlazer connection. The typical time to establish a connection is 25-35 seconds. The hosts requirements RFC requires hosts to wait 1 minute before timing out. This is usually not a problem but if you have a host that does not wait the requisite period of time, just restart the operation. The line will certainly be up in time for the command to operate the second time around. As for buffering, each outbound interface has a queue. As system administrator you get to select the number of datagrams that may be queued at any one time. The default value is 8 datagrams on the queue. If the link is not up all incoming packets are queued up to the maximum number of packets. Any additional packets are discarded. The NetBlazer is an IP-based device so it has no way of knowing how many sessions are passing through it (with IP it is possible for datagrams to take different paths through the network). What the NetBlazer does do is keep track of packet activity. A timer is reset every time a d'gram passes through an interface. If the timer times out the NetBlazer commands the modem to hang up. The timer may be set to anything from 1 second to 65535 seconds but the default value is 180 seconds. Since my connection to our network at work is a local call, I keep my timeout set to 600 seconds (10 minutes). What happens if the link times out while you are still "connected" (you got up for a cup of coffee)? Nothing really. If you are doing TELNET or rlogin, your next keystroke will generate a d'gram and the NetBlazer will dial and reconnect. You simply have to wait for about 25 seconds while the NB reconnects. One last feature that comes in handy if you are in a hurry to get something done. The NetBlazer support inverse multiplexing. If you have more than one modem you may elect to have the NetBlazer bring up more than one connection to the destination NetBlazer. In that case you get the throughput of two (or more!) modems. And while we are on the subject of throughput, I typically see a throughput of 1.6K bytes/second per modem when sending binary files with FTP. Text files benefit greatly from the V.42bis compression in the modem and I usually see 2.5 KB/s to 3 KB/s throughput. The NetBlazer also supports Van Jacobson's IP/TCP header prediction/compresion algorithms when running SLIP or PPP. This greatly reduces latency and makes interactive activities (TELNET, rlogin, rsh, etc.) more palatable. Well, I hope I have answered your questions to your satisfaction. Feel free to write or call. Brian Lloyd, WB6RQN Telebit Corporation Network Systems Architect 1315 Chesapeake Terrace brian@napa.telebit.com Sunnyvale, CA 94089-1100 voice (408) 745-3103 FAX (408) 734-3333 -- Brian Lloyd, WB6RQN Telebit Corporation Network Systems Architect 1315 Chesapeake Terrace brian@napa.telebit.com Sunnyvale, CA 94089-1100 voice (408) 745-3103 FAX (408) 734-3333
sob@tmc.edu (Stan Barber) (05/28/91)
In article <1991Apr6.073416.21710@telebit.com> brian@telebit.com (Brian Lloyd) writes: >The NetBlazer also supports Van Jacobson's IP/TCP header >prediction/compresion algorithms when running SLIP or PPP. This >greatly reduces latency and makes interactive activities (TELNET, >rlogin, rsh, etc.) more palatable. The documentation on this option does not say it works for PPP. I have not tested it on PPP, though. Quote from Page 6-38 "The ip vj command controls whether or not Van Jacobson TCP header compression willbe uses for a specified slip interface." -- Stan internet: sob@bcm.tmc.edu Director, Networking Olan uucp: rutgers!bcm!sob and Systems Support Barber Opinions expressed are only mine. Baylor College of Medicine
sob@tmc.edu (Stan Barber) (05/28/91)
In article <5731@gazette.bcm.tmc.edu> sob@tmc.edu (Stan Barber) writes: >In article <1991Apr6.073416.21710@telebit.com> brian@telebit.com (Brian Lloyd) writes: >>The NetBlazer also supports Van Jacobson's IP/TCP header >>prediction/compresion algorithms when running SLIP or PPP. This >>greatly reduces latency and makes interactive activities (TELNET, >>rlogin, rsh, etc.) more palatable. > >The documentation on this option does not say it works for PPP. I have not >tested it on PPP, though. > >Quote from Page 6-38 > >"The ip vj command controls whether or not Van Jacobson TCP header >compression will be used for a specified slip interface." Here is what happens when you try to enter it manually: netblazer:Top>Configure>IP> vj pppinterface pppinterface is a PPP interface, the vj command is for SLIP Oh well. Maybe this is a feature is some later version of the software. The version I have is 1.00x0. I will try it under slip in a bit and let folks know what I find. [I guess I really should just make one big article of everything I figure out. I don't know if this blow by blow bit is helpful... If you have a contructive opinion, drop me a line. Send flames to /dev/null.] -- Stan internet: sob@bcm.tmc.edu Director, Networking Olan uucp: rutgers!bcm!sob and Systems Support Barber Opinions expressed are only mine. Baylor College of Medicine
brian@telebit.com (Brian Lloyd) (05/31/91)
sob@tmc.edu (Stan Barber) writes: >In article <1991Apr6.073416.21710@telebit.com> brian@telebit.com (Brian Lloyd) writes: >>The NetBlazer also supports Van Jacobson's IP/TCP header >>prediction/compresion algorithms when running SLIP or PPP. This >>greatly reduces latency and makes interactive activities (TELNET, >>rlogin, rsh, etc.) more palatable. >The documentation on this option does not say it works for PPP. I have not >tested it on PPP, though. >Quote from Page 6-38 >"The ip vj command controls whether or not Van Jacobson TCP header >compression willbe uses for a specified slip interface." VJ header compression does work on PPP. PPP automatically negotiates VJ header compression support. Unfortunately the negotiation used by the the NetBlazer conforms to the earlier form specified in RFC1172. The mechanism for this negotiation has been changed but the NetBlazer has not yet been brought up to date. This will be corrected in a future release (sorry I can't give you a time frame yet). If you are using PPP to connect between two NetBlazers you will get VJ header compression by default. -- Brian Lloyd, WB6RQN Telebit Corporation Network Systems Architect 1315 Chesapeake Terrace brian@napa.telebit.com Sunnyvale, CA 94089-1100 voice (408) 745-3103 FAX (408) 734-3333