Conversations

n/a

A network conversation is traffic between two specific endpoints. In this case, a TCP conversation is all the traffic between two IP addresses on the same TCP ports. In most cases, the TCP server port will persist, but the TCP client will be ephemeral (will be different for each new connection from that IP address to a given TCP server). 

The total number of TCP conversations observed at the Visibility Point is calculated and recorded every 10 seconds. 

Packets per second (pkt/s)

Tx or Rx

The rate at which TCP packets are being observed at the Visibility Point.

The rate is calculated and recorded every 10 seconds. 

Bandwidth

Tx or Rx

The rate at which data containing TCP segments is being observed at the Visibility Point.

The figure will include network processing overhead (network protocol headers, retransmissions, etc).

Microburst

Tx or Rx

The rate at which data containing TCP segments is being received (Rx) or transmitted (Tx), by this Dedicated Server, including network processing overhead (network protocol headers, retransmissions, etc). The rate is calculated using a 1 millisecond window, and the maximum rate seen over each 10 second period is measured and recorded. 

Loss %

Tx or Rx

The percentage of TCP data which is not successfully acknowledged (and so which is assumed to be lost). 

TCP out of sequence bandwidth

Tx or Rx

TCP data which is observed to be out of order, measured as bandwidth.

TCP retransmission bandwidth

Tx or Rx

TCP retransmissions, measured as bandwidth.

TCP round-trip time (RTT)

Tx or Rx

TCP round trip is a calculation of the latency between the Visibility Point and the External or Internal Entity, measured as a round trip. VMX-Capture calculates this measurement by observing the delays taken to acknowledge data during the conversation. Sometimes if a TCP conversation is heavily asymmetric (i.e. a lot more data in one direction than the other direction), it may be hard to calculate the TCP round-trip time for the sparse side of the conversation, and the resulting measurement will be less accurate.

TCP Zero Window

Tx or Rx

Each side of a TCP conversation advertises (at the start of the connection) their TCP receive window. This is the size of the data buffer that temporarily holds incoming data (before it is passed to the receiving application on the same host). If the sending side of a conversation sends enough data to fill the receiving side’s TCP receive buffer, it has to wait for an acknowledgment back from the host before it can send any more data.

Each host can adjust this window during the course of the TCP conversation. When a TCP receiver gets overwhelmed with data being received on a particular connection, it can reduce its receiver window. In extreme circumstances, it will advertise a zero window size. This prevents the host from sending any further data, until it receives further acknowledgements from the receiving host.

TCP Zero Window counts indicate that one of the hosts in the conversation is struggling to process the volume of data sent by the host. This will result in application delays. It should be resolved by application changes. Splitting the data across more TCP connections may resolve the issue, or application changes may be necessary to speed up the receiving application’s performance.

Missed bandwidth

Tx or Rx

This measurement captures where traffic is not seen and resequenced by the TCP decoder within VMX-Capture during the TCP window, but which the VMX-Capture can see is seen and acknowledged by the other side of the TCP conversation. This indicates that there is a problem with the packet mirroring configuration, or with the VMX-Capture server being overloaded. It indicates that the other TCP statistics cannot be relied upon during this time period.

It can potentially also (in rare circumstances) indicate a problem with the TCP window configuration setting for the VMX-Capture TCP decoder. Checking to see which aggregator levels, as well as looking at Beeks Analytics and packet mirroring internal diagnostics, will identify where the issue is occurring.

Gaps

Tx or Rx

Similar to missed bandwidth, but as opposed to measuring the data that is missed, this statistic counts the number of gaps (i.e. how many times we get missed bytes, from above, with received bytes in betweeen). See ‘Missed bandwidth’ for further details.

Packets per second
Bandwidth
Microburst
Loss %

Conversations
TCP out of sequence bandwidth
TCP retransmission bandwidth
TCP round-trip time
TCP Zero Window
Missed bandwidth
Gaps

TCP Stats

/VP/ExtGroup/Int Entity

TCP DS Stats

/VP/Int Entity

TCP GW Stats

/VP/ExtGroup/Int Entity/TCP Gateway

TCP ExtGrp GW Stats

/VP/ExtGroup/TCP Gateway