The video surveillance network is a core concept that must be understood before deploying an IP video surveillance system on the network.
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IP addresses are one of the key points people must master when learning Internet Protocol (IP). In addition, since most IP video surveillance cameras include a Linux-based implementation of the underlying IP protocol stack, an IP address is as important as the laptops and servers on the network. Therefore, the IP address naturally becomes an indispensable part when deploying IP video surveillance cameras on the LAN. IP video surveillance cameras usually have only one Ethernet interface, which is different from routers (routers have multiple interfaces on different IP networks).
IP address (IPv4/IPv6)
The IP address is a generic name for the IP camera to assign a unique address to the network layer (the third layer of the OSI model). The IP address here can be either IPv4 or IPv6. As we all know, IPv6 is gradually replacing IPv4 networks, and many vendors have now provided IPv6 support in their cameras. However, most enterprise networks are still using IPv4, and it seems that they will use IPv4 for a while. Before the popularity of IPv6, it is still necessary to master IPv4. Therefore, this article is mainly about IPv4. Unless otherwise noted, the "IP address" in the text refers to the IPv4 address.
The IP address occupies a field of 4 bytes in the IP header, which contains two specified IP address fields - the source IP address and the destination IP address. As the name implies, the source address is the origin of the packet, and the destination address is where the packet is to be delivered. To record a video signal transmitted over the network, the IP camera needs to store its IP address in the source address field and store the IP address of the server or network digital video recorder (NDVR), which is the NVR, in the destination address field.
The following image is a screenshot of a packet capture from a high-definition IP camera to a piece of media streaming on the server:
From the above figure we can see that the source IP address is 192.0.2.144 and the destination IP address is 192.0.2.137, and this H.264 stream is encapsulated in the UDP/RTP protocol, ie user packet protocol/real-time transmission. protocol.
Subnetting (mask)
A 4-byte IP address is usually written in dotted decimal notation, such as 192.0.2.137. These 4 bytes are divided by a point, which is convenient for our reading and writing. In order to divide the network level, the IP address is divided into a network part and a host part.
The router identifies the network part and the host part by a combination of the IP address itself and the subnet mask. The mask is also written in dotted decimal notation, such as 255.255.255.224, which is also represented by the number of bits in the mask with a binary bit of 1. This is done after a slash followed by a bit. The number, such as /27. In fact, the masks represented by 255.255.255.224 and /27 are the same. The mask is first configured on the routed interface so that it can be connected to other subnets on the IP network, and the host on this subnet must set the mask to be the same as the route. However, the mask does not belong to or can be part of an IP packet.
If we tell the network administrator to deploy 20 video surveillance cameras in the same location, it may assign a network address of 192.0.2.128/27 and set the interface address of the router to 192.0.2.129. There are 32 host addresses, which can be assigned addresses for cameras and servers in this subnet. The lowest and highest addresses 192.0.2.128 and 192.0.2.159 are reserved. Therefore, the first IP camera address becomes 192.0.2.130, the second is 192.0.2.131, and so on. All IP cameras use the same subnet mask - 225.225.225.224.
Public IP address VS private IP address
There are three IP address spaces that are dedicated to the internal enterprise or service provider. These blocks of addresses are not transmitted over the Internet. They are called private IP addresses and are also considered RFC1918 addresses (defined by file number). These addresses are:
10.0.0.0 - 10.255.255.255 (10/8 prefix)
172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
192.168.0.0 - 192.168.255.255 (192.168/16 prefix)
If a device equipped with a private IP address is to be transmitted over the Internet, then this private address must be converted to a public address. Routers and firewalls implement this translation through network address translation (NAT/pNAT).
In many cases, it may not be necessary to access the camera directly on the public Internet, so private addresses are ideal for IP video surveillance deployments. In fact, most surveillance management systems will first stream the video signal captured by the camera to the NDVR, then use the NDVR as a proxy for the camera to watch the live or archived video stream through the NDVR. The NDVR here will be assigned a public IP address, and the camera can be equipped with a dedicated IP address. The viewing point on the Internet can access the video directly through the public IP address of the NDVR.
to sum up
This article explains how an IP camera can transmit video signals from a camera to a server over an IP network via an IP address. The router and host determine which part identifies the network and which part identifies the address in the network by the given subnet mask and IP address. Since the camera does not need to be directly connected to the outside of the corporate network in most cases, the dedicated IP address is ideal for the camera.
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