Data Transport Methods IP Addresses
An IP address (Internet Protocol address) is a unique number that devices use in order to identify and communicate with each other on a network utilizing the Internet Protocol standard. An IP address consists of four numbers separated by a dot “.”, each number is in the range 0-255. For example, the address could be “220.127.116.11”.
The IP address is further split up into a network part and a host part. The boundary between the two parts is decided by a netmask or a prefix length. A netmask of 255.255.255.0 means that the first 3 bytes will be the network address and the last byte the host address. A prefix length is a different way of providing the boundary, for example the same address as the previous example has a prefix length of 24 bits (i.e, 18.104.22.168/24).
Certain blocks of addresses have been reserved for private use:
These addresses are intended for private internets. They may not be routed out on the public Internet.
IPv6, or Internet Protocol version 6, is designed as an evolutionary upgrade to the Internet Protocol and will, in fact, coexist with the older IPv4 for some time. IPv6 is designed to allow the Internet to grow steadily, both in terms of the number of hosts connected and the total amount of data traffic transmitted. The most obvious improvement in IPv6 over the IPv4 is that IP addresses are lengthened from 32 bits to 128 bits. This extension anticipates considerable future growth of the Internet, providing for an unlimited (for all intents and purposes) number of networks and systems. For instance, IPv6 is intended to provide each cell phone and mobile electronic device its own address.
Data transport protocols for network video
The most common protocol for transmitting data on computer networks today is the TCP/IP Protocol suite. TCP/IP acts as a "carrier" for many other protocols; a good example is HTTP (Hyper Text Transfer Protocol), which is used to browse Web pages on servers around the world using the Internet.
TCP/IP protocols and ports used for network video
Common protocols and their port numbers used for the transfer of network video include:
Network Video Usage
FTP File Transfer Protocol
Transfer of files over the Internet/intranets
Transfer of images or video from network camera/video server to an FTP server or to an application
SMTP Send Mail Transfer Protocol
Protocol for sending e-mail messages
A network camera/video server can send images or alarm notifications using its built-in e-mail client
HTTP Hyper Text Transfer Protocol
Used to browse the web, i.e. to retrieve web pages from Web Servers
The most common way to transfer video from a network camera/video server where the network video device essentially works as a Web Server, making the video available for the requesting user or application server
HTTPS Hypertext Transfer Protocol over Secure Socket Layer
Used to access Web pages securely using encryption technology
Secure transmission of video from network cameras/video servers can also be used to authenticate the sending camera using X.509 digital certificates
RTP Real Time Protocol
RTP standardized packet format for delivering audio and video over the Internet. Often used in streaming media systems or videoconferencing
A common way of transmitting MPEG-based network video. Transmission can be either unicast (one to one) or multicast (one to many)
RTS PReal Time Streaming Protocol
Used to set up and control multimedia sessions over RTP
Used to set up and control multimedia sessions over RTP
IP uses two transport protocols: Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). TCP provides a reliable, connection-based transmission channel; it handles the process of breaking large chunks of data into smaller packets, suitable for the physical network being used, and ensures that data sent from one end is received on the other. UDP, on the other hand, is a connectionless protocol and does not guarantee the delivery of data sent, thus leaving the whole control mechanism and error-checking to the application itself.
In general TCP is used when reliable communication is preferred over transport latency. TCP's reliability through retransmission may introduce significant delays. UDP on the other hand provides no retransmissions of lost data and therefore does not introduce further delays.
Transmission methods for network video: Unicasting, Multicasting, and Broadcasting
There are different methods for transmitting data on a computer network:
Unicast - the sender and the recipient communicate on a point-to-point basis. Data packets are sent addressed solely to one recipient and no other computers on the network will need to process this information.
Multicast - communication between a single sender and multiple receivers on a network. Multicast technologies are used to reduce network traffic when many receivers want to view the same source simultaneously by delivering a single stream of information to hundreds of recipients. The biggest difference compared with unicasting is that the video stream only needs to be sent once. Multicasting (i.e IP-Multicasting) is commonly used in conjunction with RTP transmissions.
Broadcast - a one-to-everybody transmission. On a LAN, broadcasts are normally restricted to a specific network segment and are not in practical use for network video transmissions.
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