Network architecture refers to the physical layout of the computer connection and the logical method of their communication. the first part is known as topology or physical connection. the second part is known as protocols.
Topology is the arrangement of a network. the topology can refer to the physical layout of the network (10BASE2, 10BASE-T) or the logical layout of the network. logical topology lays out the rules of the road for data transmission. in data networking, only one computer can transmit on one wire segment at any given time.
The network architecture can be one of the following forms:
- Ethernet
- FDDI
- ATM
- Token Ring
Ethernet
Ethernet, invented in 1973 by Bob Metcalf (who later formed a new company called 3 Com, one of the most successful networking companies), was a way to circumvent the limitations of earlier networks. it was based on an IEEE (Institute of Electronic and Electric Engineers) standard called 802.3 CSMA/CD, and it provided ways to manage the crazy situation that occurred when many computers tried to transmit on one wire simultaneously.
In terms of networking, Collision happens when two computers attempt to transmit data on the same network wire at the same time. this creates a conflict. both computers sense the collision, stop transmitting, and wait a random amount of time before retransmitting. each computer can transmit data only when no other computer is currently transmitting. the larger the collision domain, the more likely it is that collision will occur. that is why Ethernet designers try to keep the number of computers in a segment as low as possible.
Collision domain
It is a group of computers that communicate on a single network wire. each computer in a collision domain listens to every other computer in the collision domain.
CSMA/CD
CSMA/CD stands for Carrier Sense Multiple Access/Collision Detection. in an Ethernet network, all the computers share a single network segment, called a collision domain. when two computers transmit packets at the same time, a condition called a collision occurs. the larger the collision domain, the more likely it is that collision will occur, which is why Ethernet designers try to keep the number of computers in a segment as low as possible.
In CSMA/CD, each computer listens for a quiet time on the wire. When the network wire is quiet, a computer that has packets of data to transmit sends them out over the network wire.
If a second computer has the need to transmit at the same tie as the first computer, both computers sense the other’s presence. both then cease transmitting data, wait a random number of milliseconds, and transmit again. the collision problem is thus solved.
Member of Ethernet’s Nuclear Family
Ethernet topology is described in IEEE standard 802.3. the members of the nuclear family are listed as follows:
- 10BASE2 or Coaxial networking: The maximum segment length of 10BASE2 is 185 meters.
- 10BASE5 or Thicknet: Thicknet is also called AUI (Attached User Interface). AUI networks are intermediate steps between 10BASE2 and 10BASE-T. 10BASE5 is a bus interface with lightly more redundancy than 10BASE2. the maximum length of a 10BASE5 segment is 500 meters.
- 10BASE-T: which runs over two of the four-wire pairs of unshielded twisted-pair wire. In 10BASE-T, the maximum cable length from the hub to a workstation is 100 meters.
The newer members of the Ethernet family are described in IEEE Standard 802.3 u, and include the following:
- 100BASE-T, also called Fast Ethernet, in which data travels at 100 megabits per second over two pairs of unshielded twisted-pair copper wire. the maximum cable length between the concentrator and the workstation for Fast Ethernet is 20 meters.
- 100BASE-FX, which is Fast Ethernet running on optical fibers. because optical fibers can carry data much further than copper wire, 100BASE-FX does not have a maximum cable length.
- 100BASE-T4, which is 100BASE-T running over four pairs of unshielded twisted-pair wire. Like 100BASE-T, 100BASE-T4 has a maximum cable length of 20 meters between the concentrator and the workstation.
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