Network Topologies

Network Topologies

Mesh Topology provides each node in a network with a dedicated connection to every other node.

Advantages:

* Improves reliability through redundancy and fault tolerance - the ability of the network to continue operation despite the presence of hardware or software faults.

* Mesh networks work well when the nodes are located at scattered points that do not lie near a common line.

* The Internet was deliberately designed using a mesh topology to allow sites to communicate during a nuclear war.

Disadvantages:

* Expensive because of the large number of cables and connections required.

* Reconfiguration of the network or the addition of another node impacts all of the other nodes.

Bus Topology - All nodes are connected to a central cable called the bus or backbone. A node wanting to communicate with another node sends a broadcast message onto the central cable, but only the intended recipient actually accepts and processes the message.

Advantages:

* Less expensive because it requires less cable and hardware than other topologies because all of the nodes are in a line and lie near the bus.

* Bus networks are simple and reliable.

* Failure of one node does not affect others.

Disadvantages:

* Entire network shuts down if there is a break in the main cable.

* Performance degrades as additional nodes are added.

* Heavy traffic slows down the network.

* Limited cable length and number of nodes.

* Problems can be difficult to isolate.

* Outdated - coaxial network interface cards (NIC) are more difficult to find.

* Terminators are required at both ends of the backbone cable.

* There can be collisions when two nodes want to communicate at the same time on the same bus.

Ring Topology - All devices are connected to one another in the shape of a closed loop or ring, so that each node is connected directly to two other nodes, one on either side of it.

Advantages:

* Requires less wire than a star topology.

* All computers have equal access to the rest of the network.

* Even with many users, network performance is steady.

* Growth of the system has minimal impact on performance.

* Each node on the ring acts as a repeater, allowing ring networks to span greater distances than other physical topologies.

* Because data travels in one direction, high speeds of transmission of data are possible.

* When using a coaxial cable to create a ring network the service becomes much faster.

Disadvantages:

* A failure in any cable or device breaks the loop and can take down the entire network.

* Response time is determined by the number of nodes on the ring - the more there are, the slower it works.

* Isolating problems can be difficult.

* Adding or removing nodes disrupts network operations.

Star Topology - Designed with each node (file server, workstations, and peripherals) connected directly to a central network hub or concentrator.

Advantages:

* Easy to add and remove nodes.

* Centralization enhances network management.

* Most concentrators contain the ability to amplify the electrical signal they receive.

* The failure of a non central node will not impact the functionality of the network.

Disadvantages:

* If the hub or concentrator fails (central device) then the network goes down.

* Expensive because of the cost of the concentrators.

* Requires more cabling.

* One virus in the network can affect all nodes.

* Limited cable length and number of nodes.

Ethernet - a frame-based computer networking technology for local area networks (LANs). It defines wiring and signaling for the physical layer, and frame formats and protocols for the media access control (MAC)/data link layer of the OSI model. Ethernet is mostly standardized as IEEEs 802.3. It has become the most widespread LAN technology in use during the 1990s to the present, and has largely replaced all other LAN standards such as token ring, FDDI, and ARCNET.

Advantages:

* High speeds - 10Mbs, 100Mbs, 1000Mbs.

* The whole network does not go down when one NIC is bad or a cable is broken.

* Ethernet is more widely supported and therefore is easier to support.

* Easy to broadcast a message to everyone.

Disadvantages:

* Complicated architecture.

Token Ring - a type of local area network where all nodes are connected in a star or ring topology. A token travels around the ring, a node catches the token, attaches its message if it has one to send, and then lets the token go to continue around the ring. The Token Ring protocol resides