What is a Broadcast?

Packets in IT networks can be sent to all par­tic­i­pants via broadcast without the recipient addresses being known. For this purpose, each network has a reserved broadcast address to which a limited or directed broadcast can be sent.

A broadcast in a computer network is a message that is trans­mit­ted to all par­tic­i­pants in a network and does not require a response. A computer in a network sends a data packet si­mul­ta­ne­ous­ly to all other par­tic­i­pants in the network. The sender does not have to specify any recipient addresses — this dis­tin­guish­es the broadcast method from unicast, in which only a single, known recipient is addressed.

The general advantage of a broadcast is that in­for­ma­tion can be widely dis­trib­uted and does not have to be trans­mit­ted multiple times. To implement the procedure, a special address is required that replaces the re­spec­tive recipient addresses. This broadcast IP is mainly used when the addresses of the in­di­vid­ual network par­tic­i­pants are unknown.

Ad­dress­ing is used to transfer data for com­mu­ni­ca­tion in a network via the Internet protocol from one system to another. The IP address enables the unique for­ward­ing and delivery of data packets from the source to the des­ti­na­tion. Like a telephone number, this address can be sub­di­vid­ed into a prefix and a call number - except that IP addresses are named network and host parts. This sub­di­vi­sion is done with the help of the netmask, which is placed over the IP address like a template. A netmask is just as long as an IPv4 address. It describes which bit positions within the IP address function as the network or host part.

An IP address is a numerical des­ig­na­tion. Each device connected to a computer network based on Internet tech­nol­o­gy is assigned an IP address. This IP address uses the Internet protocol for com­mu­ni­ca­tion. An IP address performs two main tasks: Iden­ti­fy­ing host or network in­ter­faces and ad­dress­ing location.

For wired data networks, software and hardware are in­ter­con­nect­ed using Ethernet tech­nol­o­gy. This tech­nol­o­gy enables data exchange between locally connected sub­scribers. The Ethernet network is the wired network’s most wide­spread tech­nol­o­gy, es­pe­cial­ly in company networks and home networks. Fur­ther­more, the Ethernet often forms the basis for intranets.

The MAC address is the address of a network device. It is usually written as a hexa­dec­i­mal number, such as 08-00-20-ae-fd-7e or 08:00:20:ae:fd:7e (or also: 080020aefd7e).

The broadcast address sends the data and in­for­ma­tion to all devices in a network. The network com­po­nents are re­spon­si­ble for receiving and pro­cess­ing the data. The task of the broadcast IP address is to connect all network devices with each other. We provide more in­for­ma­tion on this in our detailed article on the broadcast address.

A dis­tinc­tion is also made between limited and directed broad­casts:

With the limited broadcast, an IP address is specified as the des­ti­na­tion. This IP address is always 255.255.255.255. Tech­ni­cal­ly, this broadcast targets all existing IP addresses. In fact, however, the specified IP is un­der­stood to be the address for the broadcast in this network. This des­ti­na­tion is always in the user’s own network and can therefore be im­ple­ment­ed with the help of an Ethernet broadcast. A router does not forward packets like this.

With a directed broadcast, all re­cip­i­ents within the target network are always addressed. In this case, a com­bi­na­tion of the number of the des­ti­na­tion network and setting all host bits to 1 results in the broadcast address. If the des­ti­na­tion is not in its own (sub)network, a router will forward the data packet.