IPv6

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 “192.36.253.80”. 

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, 192.36.253.80/24).

Certain blocks of addresses have been reserved for private use:

10.0.0.0/8 (netmask 255.0.0.0)
172.16.0.0/12 (netmask 255.240.0.0)
192.168.0.0/16 (netmask 255.255.0.0)

These addresses are intended for private internets. They may not be routed out on the public Internet.

IPv6

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:

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.

QoS (Quality of Service)

Nowadays, fundamentally different networks are merging into one IP network. For example, telephone and video (CCTV) networks are migrating towards IP. In these networks, you will need to control the way to share network resources to fulfill the requirements of each service. One solution is to let the network routers and switches behave differently on different kinds of services (voice, data, video) as the traffic passes through the network. This technique is called Differentiated Services (DiffServ). By using QoS, different network applications can co-exist on the same network, without consuming each other’s bandwidth.

Definition

The term Quality of Service refers to a number of technologies to guarantee a certain quality to different services on the network. Quality can be, for instance, a maintained level of bandwidth, low latency, no packet losses, etc. The main benefits of a QoS-aware network can be summarized as:

• The ability to prioritize traffic and thus allow critical flows to be served before flows with lesser priority.

• Greater reliability in the network, thanks to the control of the amount of bandwidth an application may use, and thus control over bandwidth races between applications.

QoS and network video: Requirements

To use QoS in a network with network video products, the following requirements must be met:

• All network switches and routers must include support for QoS. This is important to achieve end-to-end QoS functionality.

• The network video products used must be QoS-enabled.

QoS scenarios

Ordinary (non-QoS aware) network

In this example, PC1 is watching two video streams from cameras Cam1 and Cam2, with each camera streaming at 2.5 Mbps. Suddenly, PC2 starts a file transfer from PC3. In this scenario, the file transfer will try to use the full 10 Mbps capacity between the routers R1 and R 2, whilst the video streams will try to maintain their total of 5 Mbps. The amount of bandwidth given to the surveillance system can no longer be guaranteed and the video frame rate will probably be reduced. At worst, the FTP traffic will consume all the available bandwidth.

QoS aware network

The router R1 has been configured to devote up to 5 Mbps of the available 10 Mbps for streaming video. FTP traffic is allowed to use 2 Mbps, and HTTP and all other traffic can use a maximum of 3 Mbps. Using this division, video streams will always have the necessary bandwidth available. File transfers are considered less important and get less bandwidth, but there will still be bandwidth available for web browsing and other traffic. Note that these maximums only apply when there is congestion on the network. If there is unused bandwidth available, this can be used by any type of traffic.

About Pan Tilt Zoom (PTZ) traffic

PTZ traffic is often regarded as critical and requires low latency to guarantee fast responses to movement requests. This is a typical case in which QoS can be used to provide the necessary guarantees. The QoS control of PTZ traffic in Axis network video products is handled by the ActiveX viewer AXIS Media Control (AMC), which is automatically installed the first time the Axis product is accessed from Microsoft Internet Explorer.