What are the differences between CSMA/CD and CSMA/CA?

CSMA/CD (Carrier Sense, Multiple Access/ Collision Detection) is used to determine which computer should use the shared media at any given moment. Carrier Sense means that each machine (also called a node) that is on the network, checks the cable before sending a data packet. If one node is using the network and another node wants to send something, then is will listen to for any traffic on the cable. If it hears any traffic on the cable then it will wait until the cable is free, when there is no more traffic then the node sends the packet on through.
CSMA/CA (Carrier Sense, Multiple Access/ Collision Avoidance) is used for wireless networks has a feature that CSMA/CD doesn’t have. If the node has checked the media (which is the radio frequency it will use since it is wireless and is not using cables) to see if it were available it will send out a packet as a warning to the other nodes to tell them that it is about to send some data out. If the receiving nod receives that first packet, then it will send a confirmation packet saying it received the first packet. After this the first node will forward the actual data packet.
So CSMA/CD is used for a network that is hard wired using an Ethernet cable and the CSMA/CA is used for a network that is operating wirelessly.

LAN, WAN, and MAN

LAN


WAN


MAN

Degaussing a CRT monitor

1) Attach the CRT to a working computer system and power on the monitor.
2) Press the Menu button on the front of the CRT cabinet (this is the button on the far right of the picture).





3) Use the up and down buttons on the CRT monitor to select the Extra Controls.
4) Press the Menu button on the front panel to select the Extra Controls submenu.


5) Press the Menu button on the front of the monitor because the Degauss menu item is already selected. If degaussing was required you should have heard a distinctive sound that is the sound for degaussing and the image on the screen would be distorted.

The parts of a Bubble-Jet printer

1)Unplug the bubble-jet printer from the power source and the computer.
2)Open the top cover to expose the inner print mechanism.
3)Locate and identify the paper tray.

4) Locate and identify the paper-feed sensor.












5)Locate and identify the pickup roller(s).












6)Locate and identify the separator pad(s).






7)Locate and identify the printhead.











8)Locate and identify the carriage assembly.

Hubs, Routers, Switches, and Bridges

A hub is a networking device used to connect the drops in a physical star topology network into a logical bus topology, most hubs today are replaced with switches.


The router is also a networking device that connects multiple networks that use the same protocol.


The switch is another networking device used to sort through and forward traffic based on specific criteria. Unlike a hub, switches forward packets to only the correct port based on MAC addresses.


A bridge (yes, another one) divides a logical bus network into subnets. Bridges examine the MAC address of each packet and forward packets only as necessary.

Network + class 1/27/10

Today we recapped on our previous class and talked a little more in depth about the OSI model. To see some information about this please scroll down through my blog to see what I said about the OSI model. After we finished with this we started to talk about Topology. Topology is basically a diagram about how computers are connected. We talked about 4 types:

First one is a bus topology,

Second is a ring topology,

The third was a star topology.

The last that we discussed was a hybrid. A hybrid is a mix of the three. There is a box and on the inside there will be a bus or ring connection with cables coming out of it like the star (think about a game console).

After we talked about this started to move onto cabling, were we were to that there are three types of cables and they are coaxial, twisted pair, and fiber-optic. Shortly after this we stated our lab.

Network + Lab 1

Today for our first lab we created a Peer -to-Peer (P2P) connection. We took two computers and connected them to a switch. Once we connected everything we had to set which computer was going to be the primary. From there we needed to test to see if we could share a file. The connection looked like the diagram above.

Network + class 1/20/10

Today we discussed the OSI model. This model consists of 7 layers and it depicts how information is processed and sent out by the user through a network. When the information is first being sent out it is going from layer 7 to layer 1, this is called decapsulation. When the data is being received then it goes from layer 1 to layer 7, this process is called incapsulation. The layers of the OSI model are Layer 7: Application, Layer 6: Presentation, Layer 5: Session, Layer 4: Transport, Layer 3: Network, Layer 2: Data Link, and Layer 1: Physical. Layers 1-3 are the layers that consist of the Hub and cables, NIC card, and router (in this order).