What no one tells you about Timestamping
Additional features are typically used in any industry as a means to give a product more apparent value but, of course, for a much higher price.
Example: A base-model car has 5 speakers, but you can upgrade to 8 or even 12 speakers. Did you really need them though? In a car, it is a question of the luxury feeling whether to pay a premium on top.
A network packet broker is a tool, it should do its job well and in the background. Timestamping has become popular these days and several network visibility vendors claim to support this feature.
Network packet brokers can timestamp packets with high precision which is essential to understanding what is going on in the network at a packet-by-packet level. This feature, offered by several vendors, allows you to measure the network latency and network performance.
Timestamping is not useless if it is actually working, but it is very complicated to do it correctly.
We will tell you why:
1) Timestamping must be done in hardware on Ingress, CPU-based timestamping is not very good
2) You need a very good clock source to give every packet a unique timestamp
In the worst case situation, 164 Mio packets per second must be tagged. The table shows the minimum timing between frames.
- 96 ns for Gigabit Ethernet,
- 38.4 ns for 2.5 Gigabit Ethernet,
- 19.2 ns for 5 Gigabit Ethernet,
- 9.6 ns for 10 Gigabit Ethernet,
- 2.4 ns for 40 Gigabit Ethernet,
- 0.96 ns for 100 Gigabit Ethernet.
To timestamp a 100 Gbit interface a clock source with a resolution from sub 1 ns, in this case, a cäsium normal "atomic clock", would be needed to generate a timestamp with this resolution.
3) There is no standard describing where the time stamp information is added to the packet. In any case, the packet is then, technically, malformed and the monitoring tool must know which timestamp method is being used.
4) There are only a few applications where hardware timestamping is a real advantage.
5) Typically all of the offered timestamp solutions on the market are CPU based, which means they cannot achieve this performance at all.
Need more information about timestamping? Contact us today!