FAQ: Test Traffic Measurements
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What is the purpose of the Test Traffic Measurements service (TTM)?
TTM's main purpose is to provide standardized metrics for one-way delay and one-way packet loss between measurement devices in a format, which is easily understood by users. One-way measurements are vital, since more and more of Internet routing is becoming asymetrical,
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What are TTM Test Boxes?
Test Boxes are measurement devices with GPS (Global Positioning System) antennas connected to them for synchronization and increased time accuracy (approx. 100 ns). They generate test-traffic, receive test-traffic and perform trace routes to determine path vectors betwee
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How does TTM work?
One-way measurements imply that information for calculating metrics and plotting data will scattered over any two measurement devices. Consequently, central servers at the RIPE NCC must regularly collect the information, make calculations and generate the plots in order
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What is IP Packet Delay Variation (IPDV), also called "jitter"?
IPDV measures the variation in delay of uni-directional, consecutive packets (packet 1 and 2, 2 and 3 etc.) which flow between between two hosts over an IP path. Low IPDV is especially important for applications requiring timely delivery of packets, e.g. multimedia appl
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What are "valid packets"?
Valid packets are packets that have good timestamps and can therefore be used for TTM statistics. Bad packets are usally sent during unreliable GPS conditions, meaning that their timestamps are inaccurate. Bad packets are discarded when calculating TTM metrics.
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Why is it important plotting the 2.5th and 97.5th percentiles for delay measurements?
The 2.5th and 97.5th percentiles represent the one-way delay between two Test Boxes in a best-case and worst-case scenario respectively, just as the median (50th percentile) would indicate a normal value between two measurement points. In many cases, the so-calle
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What does "RMS" mean?
Physical scientists often use the term "root-mean-square" as a synonym for "standard deviation" when referring to the square root of the mean squared deviation of a signal from a given baseline. In our case, high values could be caused either by frequent path vector
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How much traffic do Test Boxes generate?
By default, approximately 300 kB per day to every destination Test Box. The defaults can be changed on series C/D. Defaults per Destination Test Box: Test-Traffic Packet Payload Size: 100 bytes Test-Traffic Packet Tx Rate: 2 packets/min
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We received and installed our Test Box, but why does it not give a login prompt?
It occasionally happens that a connector came lose during transport. Please, open the cover of the Test Box ( 4 screws) and press all connectors firmly into their sockets, in particular the flat ribbon cables for the disks and the cards on the motherboard. Also make sur
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How can the IP address of a Test Box be changed?
Please send us the new IP address, netmask & default router at least two working days before the renumbering should be effective. TT-ops will notify you when the change has been configured. When your new addressing schema is ready, press the reset button to reboot the machine. After rebooting, ping
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