The transport layer varies with network protocol in use. For TCP/IP, use the TCP object counters to monitor network activity at the transport layer:

• Segments Received/sec
• Segments Retransmitted/sec
• Segments/sec
• Segments Sent/sec

If the retransmission rate is high, this may indicate a hardware problem. The Internet Control Message Protocol (ICMP) and User Data Protocol (UDP) object counters are useful for more extensive monitoring of TCP/IP network transmissions.

The ICMP performance object consists of counters that measure the rates at which ICMP messages are sent and received by using the ICMP protocol. It also includes counters that monitor ICMP protocol errors. The UDP performance object consists of counters that measure the rates at which UDP datagrams are sent and received using the UDP. It includes counters that monitor UDP errors.