Network
Topology
The specific physical, i.e.,
real, or logical, i.e., virtual, arrangement of the elements of a network. Note 1:
Two networks have the same topology if the connection configuration is
the same, although the networks may differ in physical interconnections,
distances between nodes, transmission rates,
and/or signal types. Note
2: The common types of network topology are illustrated [refer to the
figure on this page] and defined in alphabetical order below:
·
bus
topology: A network topology in
which all nodes, i.e., stations, are connected together by a single bus.
·
fully connected topology: A network topology in
which there is a direct path (branch) between any
two nodes. Note: In a fully connected network with n nodes, there are n(n-1)/2 direct paths, i.e., branches. Synonym
fully connected mesh network.
·
hybrid
topology: A
combination of any two or more network topologies.
Note 1: Instances can occur where two basic network topologies, when
connected together, can still retain the basic network character, and
therefore not be a hybrid network. For example, a tree network connected to a
tree network is still a tree network. Therefore, a hybrid network accrues only
when two basic networks are connected and the resulting network topology fails
to meet one of the basic topology definitions. For example, two star networks
connected together exhibit hybrid network topologies. Note 2: A hybrid
topology always accrues when two different basic network topologies are
connected.
·
linear
topology: See
bus topology.
·
mesh
topology: A network topology in
which there are at least two nodes with two or more paths between them.
·
ring topology: A network topology in
which every node has exactly
two branches connected to it.
·
star
topology: A network topology in
which peripheral nodes are connected to a central node, which
rebroadcasts all transmissions received from any peripheral node to all
peripheral nodes on the network, including the originating node. Note 1:
All peripheral nodes may thus communicate with all others by transmitting to,
and receiving from, the central node only. Note 2: The failure of a transmission line, i.e.,
channel, linking
any peripheral node to the central node will result in the isolation of that
peripheral node from all others. Note 3: If the star central node is
passive, the originating node must be able to tolerate the reception of an echo of its own
transmission, delayed by the two-way transmission time, i.e.,
to and from the central node, plus any delay generated in
the central node. An active star network has an active central node that
usually has the means to prevent echo-related problems. (188)
·
tree topology: A network topology
that, from a purely topologic viewpoint, resembles an interconnection of
star networks in that individual peripheral nodes are required to transmit to
and receive from one other node only, toward a
central node, and are not required to act as repeaters or regenerators. (188) Note 1:
The function of the central node may be distributed. Note 2: As in the
conventional star network, individual nodes may thus still be isolated from the
network by a single-point failure of a transmission path to the node. Note
3: A single-point failure of a transmission path within a distributed node
will result in partitioning two or more stations from the rest of the network.