IP Routing is the Internet Protocol (IP) packet routing methodology (IP) routing within and across IP networks. It involves not only protocols and technologies but also organizational policies and Internet infrastructure configurations around the world. In each IP network node, IP routing involves determining the appropriate path for network packets from source to destination within the IP network. This process uses statically configured rules or dynamically acquired status information to select a particular packet delivery method to drive traffic to the next available intermediate network node hop closer to the desired end destination, the total potential path includes many networked computers.
Networks are separated from each other by special hosts, called gateways or routers with special software support that is optimized for routing. In routers, packets arriving at any interface are checked for source and destination addresses and queued to the corresponding out interface according to their destination address and a set of performance rules and metrics. Rules are encoded in the routing table containing entries for all interfaces and their connected networks. If there are no rules that meet the requirements for the network packet, then forwarded to the default route. The routing tables are managed either manually by the network administrator, or are dynamically updated with the routing protocol. The routing rules may contain parameters other than source and destination, such as limitations on available bandwidth, expected packet loss rate, and specific technology requirements.
The IP forwarding algorithm takes into account the size of each packet, the service type specified in the header, as well as the characteristics of available links to other routers on the network, such as link capacity, utilization rate and maximum datagram size supported on the link. In general, most routing software determines the route through the shortest path algorithm. However, other routing protocols may use other metrics to determine the best path. Based on the necessary and existing metrics for each link, each path has a corresponding link . The routing algorithm tries to minimize cost when selecting the next hop.
Routing protocols are software mechanisms by which routers communicate and share information about network topology, and the capabilities of each routing node. Thus applying global-network rules that traffic is directed in the network and across multiple networks. Different protocols are often used for different topologies or different application areas. For example, the Open Shortest Path First (OSPF) protocol is commonly used for routing packets between subnetworks within an enterprise and the Border Gateway Protocol (BGP) used on a global scale. BGP, in particular, is the de facto standard of Internet routing around the world.
Video IP routing
Routing algorithm
IP forwarding algorithm is a specific implementation of routing for IP networks. To achieve a successful data transfer, the algorithm uses the routing table to select the next-hop router as the next destination for the datagram. The selected IP address is known as the next-hop address.
When multiple destinations match, the route with the longest subnet mask is selected (the most specific). There is only one default route.
The IP forwarding algorithm states:
Provided destination IP address, D , and network prefix, N :
When no route is available, an ICMP error message is sent to the originator of the packet, to inform the host that the packet can not be sent, and to avoid unnecessary retransmission to avoid network congestion. The sending host must stop sending, or choose another address or route.
Maps IP routing
Routing table
The following presents a typical routing table in Unix-like operating systems:
IP Kernel routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 71.46.14.1 0.0.0.0 UG 0 0 0 ppp0 10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth0 71.46.14.1 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0 172.16.0.0 0.0.0.0 255.240.0.0 U 0 0 0 eth0 192.168.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0 192.168.1.0 192.168.96.1 255.255.255.0 UG 0 0 0 eth0 192.168.96.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
The host has several network interfaces. eth0 is the interface name of the network interface card representing the Ethernet port. ppp0 is the PPPoE interface, which is configured as the default route in this example.
The default route is recognized by the destination 0.0.0.0 and the flag G . A network router is identified by the network mask 255.255.255.255 and the H flag.
Routing protocol
Examples of routing protocols are Routing Information Protocol (RIP) implemented in BSD's routed software, External Gateway Protocol (EGP), and Border Gateway Protocol (BGP), which is the dominant route distribution protocol. used on the Internet.
See also
- Multipath routing
References
Source of the article : Wikipedia
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