Explanation/Reference:
Simply said, the time difference in packet inter-arrival time to their destination can be called jitter. Jitter is specific issue that normally exists in packet switched networks and this phenomenon is usually not causing any communication problems.TCP/IP is responsible for dealing with the jitter impact on communication.
On the other hand, in VoIP network environment, or better say in any bigger environment today where we use IP phones on our network this can be a bigger problem. When someone is sending VoIP communication at a normal interval (let's say one frame every 10 ms) those packets can stuck somewhere in between inside the packet network and not arrive at expected regular peace to the destined station.
That's the whole jitter phenomenon all about so we can say that the anomaly in tempo with which packet is expected and when it is in reality received is jitter.
jitter
Image from: http://howdoesinternetwork.com/wp-content/uploads/2013/05/jitter.gif In this image above, you can notice that the time it takes for packets to be send is not the same as the period in which the will arrive on the receiver side. One of the packets encounters some delay on his way and it is received little later than it was asumed. Here are the jitter buffers entering the story. They will mitigate packet delay if required. VoIP packets in networks have very changeable packet inter-arrival intervals because they are usually smaller than normal data packets and are therefore more numerous with bigger chance to get some delay along the way.
For your exam you should know below information about Network performance:
Network performance refers to measurement of service quality of a telecommunications product as seen by the customer.
The following list gives examples of network performance measures for a circuit-switched network and one type of packet-switched network (ATM):
Circuit-switched networks: In circuit switched networks, network performance is synonymous with the grade of service. The number of rejected calls is a measure of how well the network is performing under heavy traffic loads. Other types of performance measures can include noise, echo and so on.
ATM: In an Asynchronous Transfer Mode (ATM) network, performance can be measured by line rate, quality of service (QoS), data throughput, connect time, stability, technology, modulation technique and modem enhancements.
There are many different ways to measure the performance of a network, as each network is different in nature and design. Performance can also be modeled instead of measured; one example of this is using state transition diagrams to model queuing performance in a circuit-switched network. These diagrams allow the network planner to analyze how the network will perform in each state, ensuring that the network will be optimally designed.
The following measures are often considered important:
Bandwidth - Bandwidth is commonly measured in bits/second is the maximum rate that information can be transferred Throughput - Throughput is the actual rate that information is transferred Latency - Latency is the delay between the sender and the receiver decoding it, this is mainly a function of the signals travel time, and processing time at any nodes the information traverses Jitter - Jitter is the variation in the time of arrival at the receiver of the information Error Rate - Error rate is the number of corrupted bits expressed as a percentage or fraction of the total sen The following answers are incorrect:
Bandwidth - Bandwidth is commonly measured in bits/second is the maximum rate that information can be transferred Throughput - Throughput is the actual rate that information is transferred Latency - Latency is the delay between the sender and the receiver decoding it, this is mainly a function of the signals travel time, and processing time at any nodes the information traverses The following reference(s) were/was used to create this question:
CISA review manual 2014 page number 275
and
http://howdoesinternetwork.com/2013/jitter
