QUALITY OF SERVICE (QOS) EXAM
2025 QUESTIONS AND ANSWERS
Why is Quality of Service important? - ....ANSWER ...-When looking to provision
Real Time communications across a network that is being shared w/ data.
How does Quality of Service help? - ....ANSWER ...-All elements in the network (
& WAN provider network) are configured to recognize Real Time communications
streams & give them the treatment or 'priority' they need in order to get to their
destination on time.
W/in the LAN & WAN Voice quality is dependent on? - ....ANSWER ...-Delay,
Jitter, Packet loss & Bandwidth.
For best Voice quality Delay should be? - ....ANSWER ...-One way end-to-end
should be no more than 150ms. AKA latency.
For best Voice quality Jitter should be? - ....ANSWER ...-No more the 30ms.
How to test for Delay & Jitter? - ....ANSWER ...-Ping tests ( -l or -s linx/unix
parameter loads the ping packets to a more realistic size).
In a fully switched Ethernet environment will Delay be a problem? -
....ANSWER ...-Delay will not be problem, but routers will insert move delay into a
network.
...©️ 2025, ALL RIGHTS RESERVED 1
, What are Network Delay types? - ....ANSWER ...-1. Hardware Delay through the
network.
2. Variable Delay e.g Router queues.
3. Transit Delay (the time to traverse networks)
4. Processing Delay in the end devices.
Measuring Delay example? - ....ANSWER ...-Pinging w/ 238 bytes of data to
simulate a G.711 voice frame.
ping -l 238 x.x.x.x
Replay x.x.x.x bytes=238 time=40ms TTL=64
Replay x.x.x.x bytes=238 time=40ms TTL=64
What is Jitter? - ....ANSWER ...-The variation in delay from the expected value.
What can cause Jitter? - ....ANSWER ...-1. Router queues
2. Over utilized devices
3. Poor cabling
(Network problems that cause delay)
How does a IP phone cope with Jitter? - ....ANSWER ...-Jitter buffer at the
receiving end copes w/ irregularities of the network. This buffer holds each packet just
...©️ 2025, ALL RIGHTS RESERVED 2
2025 QUESTIONS AND ANSWERS
Why is Quality of Service important? - ....ANSWER ...-When looking to provision
Real Time communications across a network that is being shared w/ data.
How does Quality of Service help? - ....ANSWER ...-All elements in the network (
& WAN provider network) are configured to recognize Real Time communications
streams & give them the treatment or 'priority' they need in order to get to their
destination on time.
W/in the LAN & WAN Voice quality is dependent on? - ....ANSWER ...-Delay,
Jitter, Packet loss & Bandwidth.
For best Voice quality Delay should be? - ....ANSWER ...-One way end-to-end
should be no more than 150ms. AKA latency.
For best Voice quality Jitter should be? - ....ANSWER ...-No more the 30ms.
How to test for Delay & Jitter? - ....ANSWER ...-Ping tests ( -l or -s linx/unix
parameter loads the ping packets to a more realistic size).
In a fully switched Ethernet environment will Delay be a problem? -
....ANSWER ...-Delay will not be problem, but routers will insert move delay into a
network.
...©️ 2025, ALL RIGHTS RESERVED 1
, What are Network Delay types? - ....ANSWER ...-1. Hardware Delay through the
network.
2. Variable Delay e.g Router queues.
3. Transit Delay (the time to traverse networks)
4. Processing Delay in the end devices.
Measuring Delay example? - ....ANSWER ...-Pinging w/ 238 bytes of data to
simulate a G.711 voice frame.
ping -l 238 x.x.x.x
Replay x.x.x.x bytes=238 time=40ms TTL=64
Replay x.x.x.x bytes=238 time=40ms TTL=64
What is Jitter? - ....ANSWER ...-The variation in delay from the expected value.
What can cause Jitter? - ....ANSWER ...-1. Router queues
2. Over utilized devices
3. Poor cabling
(Network problems that cause delay)
How does a IP phone cope with Jitter? - ....ANSWER ...-Jitter buffer at the
receiving end copes w/ irregularities of the network. This buffer holds each packet just
...©️ 2025, ALL RIGHTS RESERVED 2
