What are some network devices that operate at the data link layer?
Bridges and switches are network devices that operate at the data link layer. Both devices filter traffic by MAC addresses.
What is the function of the OSI model's physical layer (Layer 1)? Give some examples of physical layer implementations.
The physical layer defines the physical medium. It defines the media type, the connector type, and the signaling type (baseband versus broadband). This includes voltage levels, physical data rates, and maximum cable lengths. The physical layer is responsible for converting frames into electronic bits of data, which are then sent or received across the physical medium. Twisted pair, coaxial cable, and fiber-optic cable operate at this level. Other implementations at this layer are repeaters/hubs, RJ-45.
The Ethernet and IEEE 802.3 standards define what three physical wiring standards that operate at 10 Mbps?
These physical wiring standards operate at 10 Mbps:
10Base2
10Base5
10BaseT
What are collision domains?
In Ethernet segments, devices connect to the same physical medium. Because of this, all devices receive all signals sent across the wire. If two devices send a packet at the same time, a collision occurs. In the event of a collision, the two devices run a backoff algorithm and resend the packet. The devices retransmit up to 15 times. The first station to detect a collision issues a jam signal. When a jam signal is sent from a workstation, it affects all of the machines on the segment, not just the two that collided; when the jam signal is on the wire, no workstations can transmit data. The more collisions that occur in a network, the slower it will be, because the devices will have to resend the packet. A collision domain defines a group of devices connected to the same physical medium.
What are broadcast domains?
A broadcast domain defines a group of devices that receive each others' broadcast messages. As with collisions, the more broadcasts that occur on the network, the slower your network will be. This is because every device that receives a broadcast must process it to see if the broadcast is intended for it.
What devices are used to break up collision and broadcast domains?
Switches and bridges are used to break up collision domains. They create more collision domains and fewer collisions. Routers are used to break up broadcast domains. They create more broadcast domains and smaller broadcast areas.
How do the different layers of the OSI model communicate with each other?
Each layer of the OSI model can communicate only with the layer above it, below it, and parallel to it (a peer layer). For example, the presentation layer can communicate with only the application layer, session layer, and presentation layer on the machine it is communicating with. These layers communicate with each other using protocol data units (PDUs). These PDUs control information that is added to the user data at each layer of the model. This information resides in fields called headers (the front of the data field) and trailers (the end of the data field).
What is data encapsulation?
A PDU can include different information as it goes up or down the OSI model. It is given a different name according to the information it is carrying (the layer it is at). When the transport layer receives upper layer data, it adds a TCP header to the data; this is called a segment. The segment is then passed to the network layer, and an IP header is added; thus, the data becomes a packet. The packet is passed to the data link layer, thus becoming a frame. This frame is then converted into bits and is passed across the network medium. This is data encapsulation Application layer -- Data
Transport layer -- Segment
Network layer -- Packet
Data link layer -- Frame
There is also the Physical Layer -- Bits
What is the difference between a routing protocol and a routed protocol?
Routing protocols determine how to route traffic to the best location of a routed protocol. Examples of routing protocols are RIP, EIGRP, OSFP, and BGP. Examples of routed protocols are IP and IPX.
What 3 devices are used to segment a LAN?
Router
Switch
Bridge