Broadcast radiation
A broadcast storm is the strong accumulation of broadcast and multicast traffic in a computer network.
In the final stage of a broadcast storm no new network connections can be established, and existing connections may be interrupted. Especially in large broadcast domains can be increased by various causes in a broadcast storm, the response time of the network by a snowball dramatically.
Causes
The most common cause is the redundant cabling with two or more uplinks between two switches. In such a case, broadcast and multicast messages are forwarded to all ports except the port from which came the traffic. Thus, a loop is created, and the switches forward the broadcasts of the other switches on. In addition, a broadcast storm, for example, be triggered by a faulty network card by denial-of -service attacks ( such as the Smurf attack or Fraggle attack) or.
Countermeasures
- The Spanning Tree Protocol is suitable to manage loops between switches sense. In metropolitan networks broadcast storms by Ethernet Automatic Protection Switching ( EAPS ) can be prevented.
- Filtering of broadcasts by Layer 3 devices, normally by routers in part by brouter.
- Physical segmentation of a broadcast domain by routers or Layer 3 switches.
- Logical segmentation of a broadcast domain through the use of VLANs.
- Routers and firewalls can be configured to recognize malicious or above average number of broadcasts and block.
Misinterpretations
- A common misinterpretation is that routing loops have something to do with it. Routers that operate at Layer 3 of the OSI model, but no Layer 2 broadcasts take, as do switches.
- Another false statement is that the router can not forward Layer 3 broadcasts. However, there are routing protocols forward the broadcasts to other networks.
- It is also a misconception that only routers define a broadcast domain and thus can limit broadcast storms. As mentioned in the counter-measures, this can also switch with VLANs or Layer 3 features ( which, however, still a router for forwarding need ).
- In addition, a broadcast can not be answered with a broadcast. However, a broadcast can be used to work out, may be how to respond to a received broadcast. In a redundant topology can be such a second broadcast reach that of the network interface that sent the initial broadcast.
MANET broadcast storms
In a mobile ad hoc network ( MANET ) packets to request routing information ( RREQ ) are usually sent via broadcast to find new routes. This RREQ packets may cause broadcast storms. One approach to reduce this, is to block some hosts for re- broadcasts.