FAQ: Test Traffic Measurements

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,

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

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

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

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.

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

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

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

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

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