robert@cantuar.UUCP (Robert Biddle) (05/07/87)
We run 4.3BSD on our Vax 750 and also have a Sun and expect to get more
Suns. The Sun and Vax are ethernetted and use TCP/IP. For terminal
access at the moment we use concentrators on a Cambridge Ring.
However, we now also want to get a Terminal Server for the ethernet.
This gives us a fall-back to the flaky Ring hardware, and might also
yield useful compatability with a campus-wide ethernet being introduced.
So, what terminal server should we consider getting? It must be TCP/IP,
but as the campus-wide ethernet will be predominately DECnet, some nod
in that direction would be useful.
We don't have much money to spend, but on the other hand are irritated by
the Ring hardware letting us down and don't want to see that again.
We're a bit new to ethernet gadgets, and I suspect this question is old hat,
so *mail* any advice, please; I'll post a summary if anything particularly
interesting turns up.
Thanks very much,
--
Robert Biddle Office: +64 3 482 009 x8352 Home: +64 3 64741; +64 21 76205
robert@cantuar.{nz,uccp} ...!{watmath,munnari,mcvax,vuwcomp}!cantuar!robert
Computer Science, University Of Canterbury, Christchurch, Aotearoa/New Zealandhedrick@topaz.UUCP (05/13/87)
I don't know of anyone making a terminal server that speaks both TCP and DECnet. If you are primarily TCP, I suggest handling your DECnet machines by using a terminal server backwards to front end your DECnet-only machines. Bridge even makes a terminal server with hardware that simulates some standard controller card (DZ11?) for this purpose. The manufacturers of terminals servers that I know are Bridge, Cisco, Encore, Interlan, and Ungermann-Bass. We have used Bridge and Cisco, and one beta-test U-B. Of those, I would choose Cisco, except that for using them as front ends, Bridge might have a slight advantage. Cisco's advantage is that their software people seem to know TCP/IP a lot better, and so they support all the current standards. Bridge doesn't yet use domain servers for name lookups (Cisco supports both the old IEN116 and domain servers), they don't response to ICMP echo, etc. But they are both reliable products that would do the job. Our U-B isn't quite ready to be given a public evaluation. (However this might suggest that it isn't quite ready to be purchased, unless you have some specific reason to want to use U-B. U-B has some reasonable people, so eventually their product will probably be fine.) I haven't used an Interlan, except for 2 minutes at a show. Lots of people have good things to say about Encore. They support rlogin as well as telnet, and they have a modification to Gnu Emacs to move character echoing into the terminal server. We haven't ever had a chance to try them. Some questions to ask vendors: - how do you configure your box? Local floppy, load config info from their own server, from any Unix system, type commands locally and save in EEPROM? I prefer loading config files from a Unix system, but it can be easier to set up if you just type commands to the box and it save them. (Bridge uses local floppy or one of their own servers. Cisco uses commands saved in battery-backedup RAM or loading config from any host via TFTP.) - does it support all the options you need? Padding (probably need this if you use VT100-compatible terminals), modem control, auto-baud, the right speeds, killing idle sessions after a certain length of time? (Bridge and Cisco both have most of this, but Bridge tends to have a few more options in setting up parity.) - what sort of system admin tools does it have? Cisco lets you telnet to the box and type a password, so you can do things from anywhere on the network. Bridge has a similar facility (though without the password) that requires a very simple program that any Unix system will support. You'd like to see statistics on port use (including some measure of garbage on lines so you can detect bad modems and lines), network traffic, CPU loading, etc. You'd like to have the ability to kill sessions and reset parameters. Cisco has more statistics, though Bridge will show you load by time of day, which can be very useful. I don't think Bridge will let you kill sessions, and some paramters can only be set by taking the box down and doing sysgen. - how does it get host names? local table, use of one box as a server, use of standard server protocol (IEN116 or domain server). (Bridge uses IEN116, but you can use one of their boxes as an IEN116 server if you don't have it on any of your hosts. Cisco uses either IEN116 or domain server, though if necessary you can specify all the host names in the configuration file.) - how many network services do you have to support to get the things to work? (On some machines you need to have something to tell the box its Internet address, such as RARP or bootp, and a server to load configuration info.) (Bridge is either completely independent -- using floppy -- or just needs one of its ownn servers. Cisco is either completely independent -- using battery backedup RAM -- or depends upon a host on your network. It needs (RARP or bootp) and TFTP. - how complete is its TCP/IP? Does it support ICMP options, particularly redirect and echo? Subnets? Does it support telnet sync (important to get output to stop when you type ^C or ^O)? Does it send any extraneous packet types? Does it support the encapsulations you use? (ARP, HP probe, IEEE 802.3?) (Cisco supports all ICMP, subnets, telnet sync, ARP, HP probe, and the proposed IEEE 802.3 kludge. It does not send any wierd packet types. Bridge supports ICMP redirect but not echo [BOOOOO!!!!!!], subnets, telnet sync, ARP, and sends some odd broadcast packets as part of its system administration. This is not necessarily a problem unless you have some machine on your network with a really substandard network implementation.) - How does it get its routing information? The most common is to set a default gateway and depend upon ICMP redirect. Some may listen to routing protocols. (Cisco and Bridge both let you set default gateway and use ICMP redirect. I think they both let you set gateways for specific networks. Cisco lets you listen to routing using routed, or some other protocols.) - Is its use of broadcasts compatible with your network? (We have one network where using 255.255.255.255 as a broadcast address causes chaos.) Can the broadcast address be set? (I believe Bridge and Cisco both let you set the address.) - If you are going to use a box to front-end a machine without TCP/IP, make sure you know how you will configure it. The big issue is whether the box can be configued so you just telnet to a host name representing the machine. Bridge does this fairly well. With Cisco you have to telnet to both the box name and a specific port number, except that if a given box frontends only one machine, you can set things up to default the port number. Make sure flow control really works. This is hairy enough that I'd probably insist on trying it before buying. One good way to evaluate things is to get whatever documentation the system admin would have and go through a dry run with the documentation, trying to see how you would set things up. Ideally, actually get one to try. Another way to evaluate things is to ask some of these questions of your salesman. If he is unable to find anyone in the organization who knows what telnet sync is, you might look for another company.