TCP Keepalives for MultiNet Telnet

[Jeremy Begg]

Hi,

Process Software MultiNet V5.1 Rev A-X, COMPAQ AlphaServer DS20E 666 MHz,
OpenVMS AXP V7.3-2

I am investigating an intermittent problem whereby remote telnet sessions to
this system are "killed" without any action by the user. I suspect a timeout
of some sort but not sure where. The problem can't be directly reproduced
but it occurs frequently enough to be annoying.

The Telnet service is configured as follows:

Service "TELNET":
TCP socket (AF_INET,SOCK_STREAM), Port 23
Socket Options = SO_KEEPALIVE
INIT() = Merge_Image
LISTEN() = TCP_Listen
CONNECTED() = TCP_Connected
SERVICE() = Internal_Telnet
Program = "MULTINET:LOADABLE_KERBEROS_TELNET"

and as far as I can tell the following keepalive settings are in place:

$ mu set /kernel tcp_keepidle
Parameter tcp_keepidle (0x8626F3C0), Value = 14400
$ mu set /kernel tcp_keepintvl
Parameter tcp_keepintvl (0x8626F3D0), Value = 150
$ mu set /kernel tcp_keepcnt
Parameter tcp_keepcnt (0x8626F3B0), Value = 8

which I believe are the usual default values. If I understand this
correctly, the MultiNet kernel will send a "keepalive" ping to the remote
device after 4 hours (14400 seconds) and if it gets no response, will try 8
more times at 150-second intervals. If all 9 keepalives fail it kills the
session. (Is this correct?)

I don't think this really matches what the users have reported so I was
wondering if it's possible to set separate keepalive timers for the Telnet
service, and if so, how might I change them and see what values are in
place?

Thanks,

Jeremy Begg

+---------------------------------------------------------+
| VSM Software Services Pty. Ltd. |
| http://www.vsm.com.au/ |
| "OpenVMS Systems Management & Programming" |
|---------------------------------------------------------|
| P.O.Box 402, Walkerville, | E-Mail: ***@vsm.com.au |
| South Australia 5081 | Phone: [phone] |
|---------------------------| Mobile: [phone] |
| A.C.N. 068 409 156 | FAX: [phone] |
+---------------------------------------------------------+

[Jim Mehlhop]

I would change the keepalive to a smaller value. some of the Firewalls
are pretty short to timeout a connection

Jim

Post by Jeremy Begg
Hi,
Process Software MultiNet V5.1 Rev A-X, COMPAQ AlphaServer DS20E 666 MHz,
OpenVMS AXP V7.3-2
I am investigating an intermittent problem whereby remote telnet sessions to
this system are "killed" without any action by the user. I suspect a timeout
of some sort but not sure where. The problem can't be directly reproduced
but it occurs frequently enough to be annoying.
TCP socket (AF_INET,SOCK_STREAM), Port 23
Socket Options = SO_KEEPALIVE
INIT() = Merge_Image
LISTEN() = TCP_Listen
CONNECTED() = TCP_Connected
SERVICE() = Internal_Telnet
Program = "MULTINET:LOADABLE_KERBEROS_TELNET"
$ mu set /kernel tcp_keepidle
Parameter tcp_keepidle (0x8626F3C0), Value = 14400
$ mu set /kernel tcp_keepintvl
Parameter tcp_keepintvl (0x8626F3D0), Value = 150
$ mu set /kernel tcp_keepcnt
Parameter tcp_keepcnt (0x8626F3B0), Value = 8
which I believe are the usual default values. If I understand this
correctly, the MultiNet kernel will send a "keepalive" ping to the remote
device after 4 hours (14400 seconds) and if it gets no response, will try 8
more times at 150-second intervals. If all 9 keepalives fail it kills the
session. (Is this correct?)
I don't think this really matches what the users have reported so I was
wondering if it's possible to set separate keepalive timers for the Telnet
service, and if so, how might I change them and see what values are in
place?
Thanks,
Jeremy Begg
+---------------------------------------------------------+
| VSM Software Services Pty. Ltd. |
| http://www.vsm.com.au/ |
| "OpenVMS Systems Management & Programming" |
|---------------------------------------------------------|
| South Australia 5081 | Phone: [phone] |
|---------------------------| Mobile: [phone] |
| A.C.N. 068 409 156 | FAX: [phone] |
+---------------------------------------------------------+

[Jeff Schreiber]

Post by Jim Mehlhop
I would change the keepalive to a smaller value. some of the Firewalls
are pretty short to timeout a connection

Likewise, some have issues when the keepalive comes from the outside
(I recall an issue I had with a linksys router). The connection is
fine, but without anything being initated from the client side, the
firewall times out and blocks the keepalive from the remote side.

Turning on keepalives from the -client- side keeps the firewall
routing open. I imagine a blinking cursor would be frequent enough
to "keep-alive" from the server side.

-Jeff

--
Jeff Schreiber Principal Software Engineer Process Software LLC
***@process.com http://www.process.com
TCPware, MultiNet & PMDF: Stronger than Ever