A non-broadcast multiple access network (NBMA) is a
computer network
A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...
to which multiple hosts are attached, but data is transmitted only directly from one computer to another single host over a
virtual circuit
A virtual circuit (VC) is a means of transporting data over a data network, based on packet switching and in which a connection is established within the network between two endpoints. The network, rather than having a fixed data rate reservation ...
or across a
switched fabric.
Examples of non broadcast technologies
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Asynchronous Transfer Mode
Asynchronous Transfer Mode (ATM) is a telecommunications standard defined by American National Standards Institute (ANSI) and ITU-T (formerly CCITT) for digital transmission of multiple types of traffic. ATM was developed to meet the needs of ...
(ATM)
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Frame Relay
Frame Relay is a standardized wide area network (WAN) technology that specifies the physical and data link layers of digital telecommunications channels using a packet switching methodology. Originally designed for transport across Integrated Se ...
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X.25
X.25 is an ITU-T standard protocol suite for packet-switched data communication in wide area networks (WAN). It was originally defined by the International Telegraph and Telephone Consultative Committee (CCITT, now ITU-T) in a series of drafts ...
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home power line networking
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Wireguard
Replication broadcasts
Some NBMA network devices support
multicast
In computer networking, multicast is group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution. Multicast should not be confused with ...
and
broadcast traffic replication (pseudo-broadcasts).
This is done by send multiple copies of a broadcast packet, one through virtual circuit, so that the broadcast gets to all intended recipients.
Power line networks
The
ITU-T
The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunications and Information Commu ...
G.hn
G.hn is a specification for home networking with data rates up to 2 Gbit/s and operation over four types of legacy wires: telephone wiring, coaxial cables, power lines and plastic optical fiber. A single G.hn semiconductor device is able to n ...
standard provides a specification for creating a high-speed (up to 1 Gigabit/s)
local area network
A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger ...
using existing home
power lines
Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. The interconnected lines that facilitate this movement form a ''transmission network''. This is d ...
, phone lines and
coaxial cables
Coaxial cable, or coax (pronounced ) is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric ( insulating material); many coaxial cables also have a ...
.
Because of
multipath propagation
In radio communication, multipath is the propagation phenomenon that results in radio signals reaching the receiving antenna by two or more paths. Causes of multipath include atmospheric ducting, ionospheric reflection and refraction, and reflec ...
, power lines use frequency-selective channels. Channel frequency response is different for each pair of transmitter and receiver, so modulation parameters are unique for each transmitter and receiver pair. Since each pair of devices uses a different modulation scheme for communication, other devices may not be able to demodulate the information sent between them.
Split horizon route advertisement
In NBMA networks a special technique called
split horizon route advertisement
In computer networking, split-horizon route advertisement is a method of preventing routing loops in distance-vector routing protocols by prohibiting a router from advertising a route back onto the interface from which it was learned.
The concep ...
must be disabled by
distance-vector routing protocol
A distance-vector routing protocol in data networks determines the best route for data packets based on distance. Distance-vector routing protocols measure the distance by the number of routers a packet has to pass; one router counts as one hop. ...
s in order to route traffic in a hub and spoke topology. The reason being is that split horizon dictates that a router cannot send a routing table update out of the same interface from which it received it. Thus eliminating the proper propagation from one location to another. This family of protocols relies on
link layer broadcasting for route advertisement propagation, so when this feature is absent, it has to be emulated with a series of
unicast
Unicast is data transmission from a single sender (red) to a single receiver (green). Other devices on the network (yellow) do not participate in the communication.
In computer networking, unicast is a one-to-one transmission from one point in ...
transmissions, which may result in a receiver node sending a route advertisement back to the node it has just received it from.
See also
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Open Shortest Path First
Open Shortest Path First (OSPF) is a routing protocol for Internet Protocol (IP) networks. It uses a link state routing (LSR) algorithm and falls into the group of interior gateway protocols (IGPs), operating within a single autonomous sys ...
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Routing protocol
A routing protocol specifies how routers communicate with each other to distribute information that enables them to select routes between nodes on a computer network. Routers perform the traffic directing functions on the Internet; data packets ...
References
{{DEFAULTSORT:Non-Broadcast Multiple-Access Network
Network protocols