In networking, a protocol is a set of rules for formatting and processing data. Network protocols are like a common language for computers. The computers within a network may use vastly different software and hardware; however, the use of protocols enables them to communicate with each other regardless.
Standardized protocols are like a common language that computers can use, similar to how two people from different parts of the world may not understand each other's native languages, but they can communicate using a shared third language. If one computer uses the
and a second computer does as well, they will be able to communicate — just as the United Nations relies on its 6 official languages to communicate amongst representatives from all over the globe. But if one computer uses IP and the other does not know this protocol, they will be unable to communicate.
On the Internet, there are different protocols for different types of processes. Protocols are often discussed in terms of which OSI model layer they belong to.
The Internet Control Message Protocol (ICMP) reports errors and provides status updates. For example, if a router is unable to deliver a packet, it will send an ICMP message back to the packet's source.
IGMP: The Internet Group Management Protocol (IGMP) sets up one-to-many network connections. IGMP helps set up multicasting, meaning multiple computers can receive data packets directed at one
, because it puts data into a format that applications (e.g. a browser) can use directly, without further interpretation. The lower layers of the OSI model are handled by a computer's operating system, not applications.
is a faster but less reliable alternative to TCP at the transport layer. It is often used in services like video streaming and gaming, where fast data delivery is paramount.
What protocols do routers use?
Network routers use certain protocols to discover the most efficient network paths to other routers. These protocols are not used for transferring user data. Important network routing protocols include:
is an application layer protocol networks use to broadcast which IP addresses they control. This information allows routers to decide which networks data packets should pass through on the way to their destinations.
EIGRP: The Enhanced Interior Gateway Routing Protocol (EIGRP) identifies distances between routers. EIGRP automatically updates each router's record of the best routes (called a routing table) and broadcasts those updates to other routers within the network.
OSPF: The Open Shortest Path First (OSPF) protocol calculates the most efficient network routes based on a variety of factors, including distance and bandwidth.
RIP: The Routing Information Protocol (RIP) is an older routing protocol that identifies distances between routers. RIP is an application layer protocol.
How are protocols used in cyber attacks?
Just as with any aspect of computing, attackers can exploit the way networking protocols function to compromise or overwhelm systems. Many of these protocols are used in distributed denial-of-service (DDoS) attacks. For example, in a
is able to mitigate attacks at layers 3, 4, and 7 of the OSI model. In the example case of a SYN flood attack, Cloudflare handles the TCP handshake process on the server's behalf so that the server's resources never become overwhelmed by open TCP connections.
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