telnet compare with set host confused me ??

[S.C Lee]

Dear all:

I have a question about what's the difference between telnet and DCL command "set host"

Followings is the version of each machines I use

A: TCP/IP ver4.2 Openvms 6.2
B: TCP/IP ver5.1 Openvms 7.2-2
C: TCP/IP ver5.1 Openvms 7.2-2

I am used to use "set host A" to connect other system but I feel the response becomes more and more slow.
So I have a test with telnet and "set host"

Using Set host to connect to each system
the order is A->B->C->B->A
Using telnet to connect to each system
the order is A->B->C->B->A

Using "Set host" to connect do make me feel a little delay .Could anyone tell me why??

[Kris Clippeleyr]

Hi, and welcome to the forum.

You are using two different network protocols. SET HOST uses DECnet, and Telnet is an application using TCP/IP.
Since TCP/IP only implements 4 layers of the OSI model, and DECnet all of them, I think that a SET HOST incurs a little bit more overhead than a Telnet connection, hence you can "feel" that a Telnet connection is a little bit faster than a SET HOST.

You could also experiment with a SET HOST/LAT, if the LAT protocol is enabled on your systems. LAT is also pretty light-weight.

Hope this helps,

Kris

[Antoniov.]

Hi Lee,
telnet use telnet protocol over tcp/ip transport; set host use cterm over decnet.
You have not posted what decnet version you are using (decnet IV or decnet V).

I'm agree with Kris (if you are using decnet V).

Antonio Vigliotti

[Volker Halle]

With DECnet Phase V, things get even more interesting, as you can also do DECnet-over-IP

$ SET HOST node.domain
$ SET host a.b.c.d

This will allow you to run native DECnet applications transparently via a TCP/IP only network.

DECnet (e.g. SET HOST) might therefore try different transports depending on name resolution setup, so the initial connect may be more complicated and therefore taking more time.

When do you experience the 'delay' ? Initial connection until receiving Username: prompt. Or when logged in and hitting characters and having to wait for the 'echo' ? (note that SET HOST does local echoing !).

Volker.

[S.C Lee]

Thanks for the help
But I still get confused.

LAT is the protocol over DECnet.
Following URL shows that protocol is on the Application Layer
http://www.protocols.com/pbook/decnet.htm#LAT

Page5-1 in the book "TCP/IP Networking on OpenVMS Systems" also indicate "set host" could invoke the telnet or rlogin

I DO have a test for Using DCL command "set host/telnet A" to invoke TELNET.The result is indeed the same as TELNET.

But using "set host" without any qualifier really make me feel a little delay.

The question is why using "set host/lat" will make the response time faster than "set host", I think both of them using the protocol over Decnet , right?

[Volker Halle · Accepted solution]

SET HOST/LAT does NOT use DECnet. It's completely separate protocol (60-04), which runs on your local network adapter (no routing).

Volker.

[Ian Miller.]

the delay may be due to name resolution issues on the host to which you are connecting. As you connect the receiving host attempts to backtranslate the network address from which the connection is recieved. Check for a backtranslation failure opcom message.

[Bojan Nemec]

Hi,

In the link you posted LAT and some other protocols (LAVC,MOP...) are listed as DECnet protocols. This is not realy true. If you look at the picture at the top of the page you see that LAT (and other mentioned before) have only the physical layer in common. The physical layer means cabling and devices (ethernet I supose in yours case, but can be a telephone line or something else).

So LAT is a separate protocol which uses the same physical layer as DECnet and TCP/IP.

Regarding set host. In OpenVMS you create a command with Command Language Definition (CLD), all the DCL commands use this mechanism. In CLD you define that a command runs a program, but you can also define that if a specified qualifier (or parameter) is present this command runs another program. Set host define that the program is sys$system:rtpad.exe which is the DECnet "telnet". When you add the /lat qualifier it runs sys$system:ltpad.exe which is the LAT version. If you add /telnet qualifier the program is sys$system:tcpip$telnet.exe which is the same as with the command telnet.

Bojan

[labadie_1]

Lat and Decnet are completely distincts.

if you do
$ ana/sys
sh lan

you will see, among other things, lines such as the following

EWA13 81642A80 Eth 60-04 LAT 0015 STRTN,UNIQ,STRTD

EWA5 815AEF40 Eth 60-03 DECNET 0017 STRTN,LEN,UNIQ,STRTD

and at
http://www.iana.org/assignments/ethernet-numbers

you will find
24579 6003 - - DEC DECNET Phase IV Route[XEROX]
24580 6004 - - DEC LAT [XEROX]

By the way, I like a lot LAT. It is the first protocol to "give up" when network problems come, so I know it quickly

[Antoniov.]

SET HOST may use some different protocols.
Without any qualifier, use CTERM (over decnet); you use /LAT for LAT transport that's indipendent by decnet; /TELNET that's the same of TELNET command; /DTE to access directly to a device (for exampe to TTA0: serial port); /RLOGIN to call remote shell; /TN3270 to open a 3270 terminal on IBM host.
See HELP SET HOST for details.

Antonio Vigliotti

[Wim Van den Wyngaert]

Check the login.com too : there might be something in it that delays the sesssion only for tcpip.

There might be a message in the operator.log file.

There might be a routing problem in decnet. We had and have a routing problem that all traffic went via a 10 Mbit line. And since the network team only knows IP, IP will be managed better than decnet. Or decnet uses more hops to reach the destination or ...

In any case, TCP is faster than decnet.

Wim

[Wim Van den Wyngaert]

If your network is very saturated, decnet has a much higher retransmission delay than tcp.

If your network card is badly configured, decnet may perform "strange" too (10/100/duplex).


Wim

[labadie_1]

if you think your telnet command is slow and you want to see what is going on after you typed
$ telnet node
just do

$ def tcpip$bind_res_options "debug"

funny to see all the dialog !

and of course, a traceroute
$ @sys$startup:tcpip$define_commands
$ traceroute node

[Antoniov.]

Hi,
for Decnet IV may delay factor;
$ MC NCP
NCP>SH EXEC CHAR
....
Delay factor = 80
....
You could modify delay factor
$ MC NCP SET EXEC DELAY FACTOR nn
where nn may any value form 24 to 80; with 24 Decnet is more aggressive.
If value set works fine you can store in permanet storage
$ MC NCP DEF EXEC DELAY FACTOR nn
Delay factor is decnet latency to retrasmission.

Antonio Vigliotti

[Antoniov.]

For decnet (I don't yet know well) you can read related documentation.
http://h71000.www7.hp.com/doc/72final/6499/6499PRO.HTML

Antonio Vigliotti

[labadie_1]

sorry for the typo, of course, you must first define the logical and then do the telnet

it is really week-end time

:-)