You deploy VoIP on an existing LAN without implementing QoS.
Which of the following issues is least likely to occur as a result?
- packet delays
- packet drops
- VoIP hopping
Of the available choices, Voice over IP (VoIP) hopping is least likely to occur as a result of a failure to implement Quality of Service (QoS) on the LAN. VoIP hopping is a form of virtual LAN (VLAN) hopping; it is a data security risk associated with VoIP devices and data devices that are connected to the same physical port on a switch. Many IP phones contain switching technology that enables an administrator to daisy chain a workstation to the phone, causing both the workstation and the IP phone to use the same physical connection to the switch.
Jitter, packet delays, and packet drops could all result from deploying VoIP on an existing LAN without implementing QoS. Jitter is a variation in delay, which can cause packets to arrive out of sequence or at a different rate than they were sent. As a result, the end user might experience choppiness in the audio connection. Thus shorter packet roundtrip times contribute to better voice quality. The effects of VoIP issues like jitter and latency on a network can be analyzed by using data analysis techniques such as Mean Opinion Score (MOS) or R-Factor.
Congested networks often cause dropped packets. Dropped packets can cause clips, or breaks, in the audio stream. However, voice traffic is more tolerant of dropped packets than of delayed packets, because a small amount of packet loss is not noticeable to the human ear. Packet loss can be mitigated by implementing QoS and congestion avoidance mechanisms, increasing bandwidth, and increasing buffer space. In addition, some codecs can correct small amounts of packet loss.
Bandwidth is also crucial to the successful deployment of a VoIP network. A lack of bandwidth can lead to issues such as serialization delay. Serialization delay is the time required to place a packet onto a medium, such as a copper or fiber-optic cable. Serialization delay is directly related to the clocking method and the bandwidth of the line.