Physical & Logical Topologies Physical Topologies define the actual layout of the wire (media). For example, this classroom’s wiring is laid out in an extended star Logical Topologies define how the media is accessed by the hosts. For example, in this classroom hosts access the media on a first come, first served basis
Physical Topologies Bus Ring Star Extended Star Hierarchical Mesh
Bus Topology Single backbone All hosts directly connected to backbone Each end of the bus must be properly terminated
Ring Topology No backbone A host is directly connected to each of its neighbors Used for token passing logical topologies
Star Topology All devices connected to a central point Center of star is usually a hub or a switch Used for Ethernet technologies
Extended Star Topology Connects individual star topologies together. At the center of the star is a hub or a switch. Extends the length and size of the network. This is the topology we are using in our lab!
Hierarchical Topology Like the extended star except a computer controls traffic—not a hub or a switch. Server
Mesh Topology Each host has its own connection to every other host Used in situations where communication must not be interrupted.
Logical Topologies Broadcast Topology Each host on the LAN sends its data (or broadcasts its data) to every other host. Access to media is based of “first-come, first-serve.” (Ethernet works this way) Token Passing Topology Access to media is controlled by an electronic token. Possession of the token gives the host the right to pass data to its destination.
LAN Media Symbols Token Ring FDDI Ring Ethernet Line Serial Line
LAN Device Symbols—Layer 1 Transceiver Hub Repeater
LAYER 1—Repeater Cleans up (regenerates) and repeats the signal. Used when a network’s cabling extends beyond its capability.
LAYER 1—Transceiver Transmitter and Receiver of electronic signals—specialized repeater. Connects different media technologies Also called a MAU (Media Attachment Unit) Fiber Cat 5 UTP
LAYER 1—Hub Simply a multi-port repeater. Used to connect multiple devices to the same network drop. The Cloud
LAYER 3—Router Can be used to connect different Layer 2 devices and different topologies. Makes decisions based on network addresses (IP Addresses). What are the routers two main functions? The Cloud
Router’s Two Main Functions Path Determination Packet Switching
Router’s Two Main Functions Path Determination is the process of evaluating a packet’s destination IP address so that the router can decide which port to send out the packet.
Router’s Two Main Functions In Packet Switching, the router re- encapsulates the packet in the protocol needed for the specified port and then switches the packet out that port.
The Cloud The cloud is a collection of devices that operate at all levels (7-1) of the OSI model. The cloud is used to represent a large group of details that are not pertinent to a situation or description, at a given time. The cloud helps remind us that our discussions are about various parts of a larger interconnected network—The Internet! The Cloud