1. Topology, refers to the physical and logical diagrams which summarize network connections and information flow

2. Topology defines the structure of the network. There are two parts to the topology definition, the physical topology, which is the actual layout of the wire (media), and the logical topology, which defines how the media is accessed by the hosts.

4. The logical topology of a network is how the hosts communicate across the medium. The two most common types of logical topologies are Broadcast and Token-passing.

5. Broadcast topology simply means that each host sends its data to all other hosts on the network medium. There is no order the stations follow to use the network, it is first come, first serve. This is the way that Ethernet works and you will learn much more about this later in the semester.

6. The second type is token-passing. Token-passing controls network access by passing an electronic token sequentially to each host. When a host receives the token, that means that that host can send data on the network. If the host has no data to send, it passes the token to the next host and the process repeats itself.

7. Devices that connect directly to a network segment are referred to as hosts. These hosts include computers, both clients and servers, printers, scanners, and many other user devices. These devices provide the users with connection to the network, with which the users share, create, and obtain information. The host devices can exist without a network, but without the network we have greatly limited the hosts capabilities.

8. Host devices operate at all 7 layers of the OSI model. They perform the entire process of encapsulation and decapsulation to do their job of sending e-mails, printing reports, scanning pictures, or accessing databases. The PC itself may be thought of as a tiny network. It is considered a Layer 1-7 Device.

11. NICs are considered Layer 2 devices because each individual NIC throughout the world carries a unique code, called a Media Access Control (MAC) address. This address is used to control data communication for the host on the network. You will learn more about the MAC address later

12. The NIC provides the host's access to the medium.

13. In some cases the type of connector on the NIC does not match the type of media that you need to connect to. A good example is your Cisco 2500 router. On the router you will see AUI (Attachment Unit Interface) connectors and you need to connect the router to a UTP Cat5 Ethernet cable. To do this a transceiver (transmitter/receiver) is used. A transceiver converts one type of signal or connector to another. It is considered a Layer 1device, because it only looks at bits, and not at any address information or higher level protocols.

14. recognizing different media on a logical topology The basic functions of media are to carry a flow of information, in the form of bits and bytes, through a LAN networking media confine network signals to a wire, cable, or fiber. Networking media are considered Layer 1 components of LANs. Coaxial cable, optical fiber, and even free space can carry network signals, however, the principal medium you will study is called Category 5 unshielded twisted-pair cable (CAT 5 UTP).

17. there are many types of media, and each one has advantages and disadvantages. One of the disadvantages of the type of cable that we primarily use (CAT5 UTP) is cable length. The maximum length for UTP cable in a network, is 100 meters (approximately 333 feet). If we need to extend our network beyond that limit, we must add a device to our network. This device is called a repeater.

18. The purpose of a repeater is regenerate and retime network signals at the bit level to allow them to travel a longer distance. Watch out for the Five Repeater Rule, also know as the 5-4-3 Rule, when extending LAN segments. This rule states that you can connect five network segments end-to-end using four repeaters but only three segments can have hosts (computers) on them. Important later in the course

20. a hub is also known as a multi-port repeater. The difference is the number of cables that connect to the device. The reasons for using hubs is to create a central connection point for the wiring media, and an increase in the reliability of the network. Hubs are considered Layer 1 devices because they only regenerate the signal and broadcast it out all of their ports (network connections).

23. A bridge is a layer 2 device designed to connect two LAN segments. The purpose of a bridge is to filter traffic on a LAN, to keep local traffic local, yet allow connectivity to other parts (segments) of the LAN for traffic that has been directed there. A Bridge looks at the local address. Every networking device has a unique MAC address on the NIC, the bridge keeps track of which MAC addresses are on each side of the bridge and makes its decisions based on this MAC address list.

24. LOOKS LIKE A HUB

25. A switch is a layer 2 device just as a bridge is. In fact a switch is called a multi-port bridge, just like a hub is called a multi-port repeater. The difference between the hub and switch is that switches make decisions based on MAC addresses and hubs don't make decisions at all.

26. SWITCHES make a LAN much more efficient. They do this by"switching" data only out the port to which the proper host is connected. The purpose of a switch is to concentrate connectivity, while making data transmission more efficient. For now, think of the switch as something that is able to combine the connectivity of a hub with the traffic regulation of a bridge on each port. It switches packets from incoming ports (interfaces) to outgoing ports, while providing each port with full bandwidth (the transmission speed of data on the network backbone).

27. The router is at the OSI network layer,or otherwise known as layer 3. Routers make decisions based on groups of network addresses (Classes) as opposed to the individual MAC addresses like is done on layer 2. The purpose of a router is to make packet forwarding decisions based on logical addresses. Routers are the most important traffic-regulating devices on large networks.

28. shows a serial port which is a WAN connection. The graphic also shows the console port connection which allows direct connection to the router to be able to configure it. The type shown is an Ethernet port which is a LAN connection. This particular router has both a 10baseT and AUI connector for the Ethernet connection.