Hop (network technology)
Hop [ hɔp ] ( engl. "Hopser", "leg") is called in computer networks an intermediate step on the way of a network segment or subnet to the next. In general, the term hop is also used synonymously for the intermediate station itself, i.e. the router or gateway . The sender (e.g. a computer or router) defines the so-called "next hop" as the device that grants access to the next network segment / subnet.
In a computer network, the binary information is divided into data packets which are passed on from intermediate station to intermediate station (see router ) until they have reached the addressee. The transition from one network segment to the next is called a hop because, figuratively speaking, the packet “hops” one step further.
A distinction is made between single-hop connections, in which there is exactly one hop between the sender and recipient, and multi-hop connections, in which the packets are passed on via several intermediate stations. In multi-hop networks, one speaks of the n -hop neighborhood of a node, where n is a natural number; the n- hop neighborhood includes all network nodes that can be reached from the node under consideration via at most n hops.
The hop count is the number of intermediate stations that a packet has to overcome on the way from the sender to the addressee. Usually this number corresponds to the number of routers, gateways or level 3 ( OSI model ) switches on the way to the target device. The hop count can be determined, for example, with the traceroute diagnostic tool . Simple routing protocols such as RIPv 1 / v2 determine the shortest route to the target device ( host ) using the number of hops .
The Time to Live (TTL) approach is based on hops , in which a counter variable in the data packet itself is reduced by one with each hop. If the counter variable reaches the value zero, the packet is discarded, i.e. no longer forwarded and deleted. In this way, data packets can be prevented from endlessly wandering through the network and wasting resources if circular routes are formed due to incorrect routing.
literature
- Jeff Doyle, Jennifer Carroll: Routing TCP / IP . ISBN 978-1-58705-202-6
Web links
- https://www.techopedia.com/definition/26127/hop-count
- https://www.sciencedirect.com/topics/computer-science/routing-information-protocol
- https://web.stanford.edu/class/cs101/network-3-internet.html
Individual evidence
- ↑ Justin Menga: CCNP Practical Studies: Layer 3 switching> Introduction to Layer 3 switching. In: CiscoPress.com. November 26, 2003, accessed July 5, 2019 .