# What is Packet Loss Rate?

I am confused on the definition of Packet Loss Rate.

Is it the number of packets lost per unit of time?

or

Is is the number of packets lost per number of packets sent?

Both are possible. If no units are mentioned, I would assume it means

`(# packets lost)/(# packet sent)`.

Often, this ratio will be given as a percentage.

When 'packet loss rate' is meant as a rate per unit of time, that unit of time should be specified.

• No units were mentioned and the context of this question was very vague. I asked my professor to clarify the problem and he stated the above as what the problem was asking. However my professor also wrote the book the problem came from so I can't say if this is always the case. Apr 17, 2014 at 6:02

On its own packet loss per second is a relatively meaningless metric. 2 packets lost per second could be devastating to a flow of 2 packets per second, but to something sending 100pps, like a 10ms packetised VoIP call, that might be survivable. Notice how the impact of Loss Per Second has to be defined in conjunction with the traffic flow in Packets Per Second?

Moving to a relevant RFC, 2330 contains the following statement:

So, for example, rather than defining a metric about a "packet loss probability between A and B", we would define a metric about a "packet loss rate between A and B". (A measurement given by the first definition might be "0.73", and by the second "73 packets out of 100".)"