Many times when working an issue I ask people to send me a network trace. A network trace often points to the root cause of the problem. At a minimum, it reduces the problem space to something that is manageable.
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I recently was asked to do some analysis of a trace file, it was only 161 seconds in duration and contained a little more than 2.6 million frames. I was amazed to discover that approximately 75% of those frames where either ping requests or ping replies.
Paul covered CPU utilization and code paths but there is another very important aspect of many applications – network utilization.
Having two interfaces in a module on the same subnet does not give you two interfaces into and out of the module.
First a little background, TCP has a concept called maximum segment size (MSS). This is the largest segment (of data) that the TCP stack will accept.
A multihomed system is a system with multiple IP interfaces. These interfaces can be on the same or on different subnets. Today I want to consider protocols like FTP and NDMP.
As the system administrator for a VOS system you typically could care less about what other hosts are on the local subnet.
FTP transfer times painfully high, interactive login response time way too long, getting 1 mbps out of your 100 mbps network. While I always prefer to blame the network I have to admit that sometimes it is not the network.
Someone sent me the following trace and asked if it represented retransmissions because the “packet numbers” were duplicated.
I was recently asked if it was OK to not run the snmpd process. The answer is yes. If you are not using an SNMP manager to monitor the availability of the system there is no reason to run the snmpd process.