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4.4.4 Event Notification
SMTP
SMTP (Simple Mail Transport Protocol) is for e-mail transmission. With SMTP, e-mail can be transmitted from the
client to the mail server.
FTP
FTP (File Transfer Protocol) is for file transmission. FTP allows you to upload and download files to and from a
server. Via FTP, the user can upload information from a network camera such as snapshots or video clips to a FTP
server when an event occurs.
4.4.5 Timing Correction
NTP
NTP (Network Time Protocol) synchronizes the system time of a network device on the Internet to a reference time.
After a network device sends a request to a NTP server for time synchronization, it will receive a Greenwich Mean
Time returned from the server. NTP can solve the time difference between network cameras and other network
devices.
4.4.6 Video Quality Control
QoS
For bandwidth limitation applications, it is important to manage bandwidth allocation carefully. As part of the IEEE
802.1p standard, QoS (Quality of Service) aims to optimize bandwidth usage. QoS ensures streaming performance
at a steady level by transmitting data according to its priority and by the requests of the applications. With QoS,
bandwidth resources are used more efficiently and real-time multimedia streams can be transmitted constantly.
VIVOTEK products support QoS to allow for optimized bandwidth efficiency.
In a non-QoS environment, bandwidth is likely to be occupied by data stream, leading to jittering of other video
streams (Figure 4.6.a). In a QoS environment, since bandwidth allocation is optimized, every video stream can be
transmitted smoothly in priority (Figure 4.6.b).
FTP Data
Video /Audio
FTP Data
Video /Audio
Internet
Switch
Switch
Figure 4.6 Bandwidth allocation for (a) non-QoS, (b) QoS
Internet Packer
Data
Video/Audio
FTP Data
Download Data
Video /Audio
(a)
Viewing Video/Audio
Internet Packer
Data
Video/Audio
FTP Data
Download Data
Internet
Video /Audio
(b)
Viewing Video/Audio
Chap.4 IP Network
31
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