The network industry is becoming more aware of accountability, typically measured in performance terms against service level agreements and backed with service level guarantees and financial penalties. In the past, these SLAs have typically only been used for low speed customer facing services where accuracy to sub millisecond has not been a requirement. However, network service providers are now looking to measure network performance within their core and metro networks where the typical delay can be this small and where accuracy becomes critical. Furthermore, as the networks carry more unidirectional traffic, such as video on demand, the delay may only be meaningful if it is also measured in one direction. This paper examines the requirements for measuring very low delay using active probes by looking at time synchronisation between probes and the time-stamping mechanism for the measurement packets. Test results from three proprietary measurement solutions are then compared and their ability to measure one-way delay investigated.
展开▼
