thinQmaster Virtual testing partner Adaptive practice exams that find your weak spots and drill them. Every answer explained. From $69
Enroll

thinQmaster

Find your exam

Five questions free, before you decide.

Step 1 · choose a vendor

In one of our camps? Your practice exams come with the tuition — they are on your study page already.

Networking Fundamentals · Foundational

Packet Loss

The percentage of packets that fail to reach their destination.

Definition

Loss can be caused by congestion and queue drops, faulty cables or optics, duplex mismatches, interface errors, wireless interference or policing. TCP responds with retransmission and reduced sending rate, while real-time UDP applications suffer audible or visible gaps. Tools such as ping, pathping and mtr measure loss per hop.

Example

ping -n 100 reporting "Lost = 5 (5% loss)" indicates 5 percent packet loss.

Exam tip

Loss at one intermediate traceroute hop but not beyond it is usually ICMP rate limiting, not real loss.

Don't confuse it with

Related terms