Sniffer® Portable Professional User's Guide - NetScout
Sniffer® Portable Professional User's Guide - NetScout
Sniffer® Portable Professional User's Guide - NetScout
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Application Response Time (ART)<br />
Monitoring Your Network<br />
The Application Response Time (ART) monitor application measures and<br />
reports response times for application layer connections between<br />
servers and clients on known TCP/UDP ports in real time (for example,<br />
HTTP, Telnet, SNMP, and so on). Response times are measured as the<br />
time between when a request was sent and when the corresponding<br />
response was observed by Sniffer <strong>Portable</strong> <strong>Professional</strong>.<br />
When ART first appears, the Tabular view is displayed. However, you<br />
can also view response times for different application connections as<br />
either a client-server response time bar chart or a server response<br />
time bar chart by clicking the appropriate button at the left of the<br />
ART window. See the following sections for details on these views:<br />
ART – The Tabular View on page 98<br />
ART – The Server-Client Response Time Bar Chart on page 100<br />
ART – The Server Response Time Bar Chart on page 100<br />
About ART Monitor Alarms<br />
In addition to measuring and reporting application response times, ART<br />
also generates alarms for detected application response times that are<br />
slower than the thresholds in the App Threshold tab of the Options<br />
dialog box. See the ART Alarms on page 105 for information on how to<br />
change these thresholds.<br />
How ART Calculates Response Times<br />
In general, the ART application calculates response times by measuring<br />
the interval between when a packet is sent and when the corresponding<br />
response is seen. However, in practice, this is slightly different for<br />
connection-oriented protocols (like TCP) and connectionless protocols<br />
(like UDP).<br />
TCP – For each socket, ART stores the sequence numbers for<br />
packets sent by the client and waits for the corresponding ACK<br />
packets from the server. It then measures the time difference<br />
between the packet with the stored sequence number and the<br />
packet with the ACK to arrive at the response time.<br />
UDP – For each socket, ART measures the time between packets<br />
going from a client to a server and the next packet going from the<br />
server to the client.<br />
User’s <strong>Guide</strong> 97
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