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Expert Features
Transport Layer
10
TCP Retransmissions
Counter
TCP Retransmissions is a counter of all TCP Retransmissions over a period of time
per segment. This variable counts the number of retransmitted packets to measure
excessive retransmission in TCP/IP. A count of all TCP Retransmissions displays in
the
Overview counters of Expert View. A threshold for this counter can be set in
Expert Alarms.
Retransmissions are determined by sweeping the capture data periodically to catch
connections that retransmitted within an interval.
Expert Symptom
TCP Retransmissions are automatically logged as expert symptoms. The
Symptom
Summary
field provides information about the well-known ports (WKP) involved,
including the port number and the IP address. For example:
Between [206.250.228.69]/[TCP/IP WKP:1988] and
[206.250.228.11]/[TCP/IP WKP:197]
Diagnostic Details
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Problem Description:
A TCP/IP packet has been retransmitted. There was no ACK from the receiver,
causing the sender to retransmit the packet.
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Probable Cause(s):
1. An ACK sent by the receiver was lost.
2. The network is overloaded.
3. The path to the receiving station has long delays.
4. There may be a problem with the receiver’s TCP/IP stack.
5. There may be an overloaded switch or router.
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Recommended Action(s):
1. Load balance your network.
2. If you see repeated delays and too many retransmissions, your router or switch may
need upgrading.