Hop (networking)
In wired
Since store and forward and other latencies are incurred through each hop, a large number of hops between source and destination implies lower real-time performance.
Hop count
In wired networks, the hop count refers to the number of networks or network devices through which data passes between source and destination (depending on routing protocol, this may include the source/destination, that is, the first hop is counted as hop 0 or hop 1[1]). Thus, hop count is a rough measure of distance between two hosts. For a routing protocol using 1-origin hop counts[1] (such as RIP), a hop count of n means that n networks separate the source host from the destination host.[1][2] Other protocols such as DHCP use the term "hop" to refer to the number of times a message has been forwarded.[3]
On a
Each time a router receives a packet, it modifies the packet, decrementing the time to live (TTL). The router discards any packets received with a zero TTL value. This prevents packets from endlessly bouncing around the network in the event of routing errors. Routers are capable of managing hop counts, but other types of network devices (e.g. Ethernet hubs and bridges) are not.
Hop limit
Known as
Next hop
When configuring network devices the hop may refer to next hop.[5] Next hop is the next gateway to which packets should be forwarded along the path to their final destination. A routing table usually contains the IP address of a destination network and the IP address of the next gateway along the path to the final network destination. By only storing next-hop information, next-hop routing or next-hop forwarding reduces the size of routing tables. A given gateway only knows one step along the path, not the complete path to a destination. It is also key to know that the next hops listed in a routing table are on networks to which the gateway is directly connected .
Diagnostics
The traceroute command can be used to measure the number of router hops from one host to another. Hop counts are often useful to find faults in a network or to discover if routing is indeed correct.
Wireless ad hoc networking
In a wireless ad hoc network, commonly, every participating node is also acting as a router. This means that the terms "hop" and "hop count" are often the subject of confusion. Often, the sending node is simply counted as the first hop, thus yielding the same number for "hops" for both interpretations of "hop" as "traversed routers" and "jumps from node to node". For example, RFC 6130 defines a "1-hop neighbor" as any other node that is directly reachable via the wireless interface.
See also
References
- ^ )
- )
- )
- ^ RFC 1058, Routing Information Protocol, C. Hendrik, The Internet Society (June 1988)
- ^ "CCNP Practical Studies: Layer 3 Switching > Introduction to Layer 3 Switching". www.ciscopress.com. Retrieved 2019-07-05.