Environment
Novell GroupWise 8
Novell Open Enterprise Server 1 (OES 1) LinuxSUSE Linux Enterprise Server 11
SUSE Linux Enterprise Server 10
Novell Open Enterprise Server 2 (OES 2) Linux
Situation
Messages are transferring slow between GroupWise agents (POA, MTA, GWIA) on the same Linux server. The data transfer rate appears to be about 200 kbps. Messages that travel between GroupWise agents use MTP (Message Transfer Protocl). Messages going to different servers travel at normal rates.
Resolution
When GroupWise agents are on the same server the TCP/IP stack recognizes this and uses the loopback interface. The default MTU size for the Local Loopback is 16436. For eth0 it's 1500. Changing the MTU size to 1500 for the loopback allows the GroupWise agents to tranfer messages at normal speeds.
To check the current MTU size for the loopback interface type in ifconfig from a terminal window.
To check the current MTU size for the loopback interface type in ifconfig from a terminal window.
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:15428 errors:0 dropped:0 overruns:0 frame:0
TX packets:15428 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:28466074 (27.1 Mb) TX bytes:28466074 (27.1 Mb)
To change it add "MTU=1500" to /etc/sysconfig/network/ifcfg-lo and reboot the server.
This change of the Local Loopback MTU size is No Longer needed when using GroupWise code version 802 HP3 or later. Our GroupWise code now issues a TCP/IP call of 'No Delay' when writing the packets.
After the reboot you should see the MTU size as 1500 when you check ifconfig.