Hierarchical routing
Encyclopedia
Hierarchical routing is method of routing
in networks that is based on hierarchical addressing.
/Internet Protocol
(TCP/IP
) routing is based on a two-level hierarchical routing in which an IP address
is divided into a network
portion and a host
portion. Gateways use only the network portion until an IP datagram
reaches a gateway that can deliver it directly. Additional levels of hierarchical routing are introduced by the addition of subnetworks.
. Most corporate intranets consist of a high speed backbone network
. Connected to this backbone are routers which are in turn connected to a particular workgroup. These workgroups occupy a unique LAN
. The reason this is a good arrangement is because even though there might be dozens of different workgroups, the span of this particular description is only 2. The span of a network is the maximum hop count
to get from one host to any other host on the network. Even if the workgroups divided their LAN network into smaller partitions, the span could only increase to 4 in this particular example.
Considering alternative solutions with every router connected to every other router, or if every router was connected to 2 routers, shows the convenience of hierarchical routing. It decreases the complexity of network topology
, increases routing efficiency, and causes much less congestion because of fewer routing advertisements. With hierarchical routing, only core routers connected to the backbone are aware of all routes. Routers that lie within a LAN only know about routes in the LAN. Unrecognized destinations are passed to the default route.
Routing
Routing is the process of selecting paths in a network along which to send network traffic. Routing is performed for many kinds of networks, including the telephone network , electronic data networks , and transportation networks...
in networks that is based on hierarchical addressing.
Background
Most Transmission Control ProtocolTransmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
/Internet Protocol
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
(TCP/IP
Internet protocol suite
The Internet protocol suite is the set of communications protocols used for the Internet and other similar networks. It is commonly known as TCP/IP from its most important protocols: Transmission Control Protocol and Internet Protocol , which were the first networking protocols defined in this...
) routing is based on a two-level hierarchical routing in which an IP address
Network address
Network address may refer to:*Base address*Classful address*IP address*IPX address*Logical address*Network layer address,*X.25/X.21 address*MAC address-See also:*Autonomous system *Host address*Link layer*Subnet mask...
is divided into a network
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
portion and a host
Server (computing)
In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...
portion. Gateways use only the network portion until an IP datagram
Datagram
A datagram is a basic transfer unit associated with a packet-switched network in which the delivery, arrival time, and order are not guaranteed....
reaches a gateway that can deliver it directly. Additional levels of hierarchical routing are introduced by the addition of subnetworks.
Description
Hierarchical routing is the procedure of arranging routers in a hierarchical manner. A good example would be to consider a corporate intranetIntranet
An intranet is a computer network that uses Internet Protocol technology to securely share any part of an organization's information or network operating system within that organization. The term is used in contrast to internet, a network between organizations, and instead refers to a network...
. Most corporate intranets consist of a high speed backbone network
Backbone network
A backbone network or network backbone is a part of computer network infrastructure that interconnects various pieces of network, providing a path for the exchange of information between different LANs or subnetworks. A backbone can tie together diverse networks in the same building, in different...
. Connected to this backbone are routers which are in turn connected to a particular workgroup. These workgroups occupy a unique LAN
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
. The reason this is a good arrangement is because even though there might be dozens of different workgroups, the span of this particular description is only 2. The span of a network is the maximum hop count
Hop count
In computer networking, hop count refers to the number of routers through which data must pass between source and destination. Each router along the data path constitutes a hop, as the data is moved from one Layer 3 network to another...
to get from one host to any other host on the network. Even if the workgroups divided their LAN network into smaller partitions, the span could only increase to 4 in this particular example.
Considering alternative solutions with every router connected to every other router, or if every router was connected to 2 routers, shows the convenience of hierarchical routing. It decreases the complexity of network topology
Network topology
Network topology is the layout pattern of interconnections of the various elements of a computer or biological network....
, increases routing efficiency, and causes much less congestion because of fewer routing advertisements. With hierarchical routing, only core routers connected to the backbone are aware of all routes. Routers that lie within a LAN only know about routes in the LAN. Unrecognized destinations are passed to the default route.