topic Re: lan0 buffer setting in Operating System - HP-UX

lan0 buffer setting

Steven Buschman — Thu, 14 Mar 2002 23:19:22 GMT

J6000 running 11.0 having network issues with older IBM systems Current thought is that the IBM's max buffer size is 2048.
Where can this parameter be found on HP, I've looked in SAM and in etc/config, but maybe I overlooked it.
Thanks

Re: lan0 buffer setting

Scott Van Kalken — Fri, 15 Mar 2002 00:56:03 GMT

use ndd to tune it.

I'm not sure what the exact parameter is though.

ndd -h sup will give you a list

to change it permanently use the file

/etc/rc.config.d/nddconf

Scott.

Re: lan0 buffer setting

Ron Kinner — Fri, 15 Mar 2002 02:48:13 GMT

Since you are talking networking I assume you mean the mtu or pmtu (depends on which system you are talking about.). I worked with an AIX system once and it's default was only 6xx bytes. (don't remember the exact number just that it was in the 600's)

Symptom was that small packets went through OK but larger FTP transfers failed.

You can change it tho which is a cleaner solution than hamstringing the HP.

MTU is 1500 on an Ethernet interface by default. You can see it with netstat -r
and change it with

route add blah blah -p NewMTU

To make it permanent you have to add it in
/etc/rc.config.d/netconf. I think with a ROUTE_ARGS:

Believe you use ifconfig to set it on an AIX. Found this:

Additional Options for ifconfig and netstat Commands
The AIX ifconfig command has the following additional options:

mtu The mtu variable specifies the maximum transmission unit (MTU) used on the local network (and local subnets) and the MTU used for remote networks. To maximize compatibility with Ethernet and other networks, set both the Token-Ring and Ethernet default mtu value to 1500.

11.0 has its own interesting gotcha. All broadcast traffic is sent out with a TTL of 1. This means that it won't pass the router even if you want it to. Default was 64 on 10.20.

Ron

Re: lan0 buffer setting

rick jones — Fri, 15 Mar 2002 19:48:56 GMT

please more completely describe the problme - 2048 being the max buffer side on the IBM for what?

the tcp under UX will honor the IBM's 2048 byte window is that is what it is using for a window size