Computer Networks Notes PDF

# (Lec. 8) ## Computer Networks - Consist of two or more computers linked together to exchange data and share resources. ## Types of Computer Networks - **Local area network (LAN)**: Links computers within a building, uses direct cables, radio, and infrared signals. - **Metropolitan area network...

# (Lec. 8) ## Computer Networks - Consist of two or more computers linked together to exchange data and share resources. ## Types of Computer Networks - **Local area network (LAN)**: Links computers within a building, uses direct cables, radio, and infrared signals. - **Metropolitan area network (MAN)**: Links computers within a group of buildings, uses fiber-optic cables. - **Wide area network (WAN)**: Links computers separated by a few miles or thousands of miles, uses long-distance transmission media. ## Networking Importance: 1. **Reduced hardware costs:** Users share equipment. 2. **Connected people:** People can work together without being in the same location. 3. **Shared applications:** Users share software. File servers enable all users to work with the same application program. 4. **Building information resources:** Users create common pools of data that can be accessed by employees. ## Network Fundamentals: 1. **Cables**: Telephone lines, coaxial cables, microwaves, satellites, wireless, and fiber optic. 2. **Connects tables:** Computers 3. **Routers**: Devices that examine the data transmitted and send it to its destination. 4. **Switches:** High-speed electronic switches maintain connections between computers. 5. **Protocols:** Standards that specify how network components communicate with each other. ## Local Area Networks (LANs): - Connect computers and peripherals within a building. Users can access software, data, and peripherals. - LANs require special hardware and software. Computers connected to a LAN are called workstations or nodes. ## Different Types of LANs: 1. **Peer-to-peer** 2. **Client-server** ## Bandwidth: - Refers to the data transfer capacity of a transmission medium. ### Measured in: 1. Kilobits per second (kbps) 2. Megabits per second (Mbps) 3. Gigabits per second (Gbps) - PSTN twisted pair bandwidth: 56kbps - ISDN bandwidth: 128kbps - TV cable bandwidth: 1 to 10Mbps ## Network Topology: - Star, Ring, Bus ### Bus: - Least expensive, easiest to set up. - Uses coax cable. - Computers are daisy-chained together in a linear bus. - Data packets are sent along the coax cable. - All computers hear data sent out. ### Ring: - Uses different hardware. - More expensive. - Complex to install. - Data is passed around the ring until it reaches its destination. - Best at passing data with less collisions. ### Star: - Uses Category 5 cable (Cat 6 is used). - Cat 5 cable uses an RJ-45 connector for the NIC Card. - Easy to install and not that expensive. - Computers are concentrated into a star pattern. - Uses hubs or switches. - Hubs broadcast data to all devices. - Switches can be used instead of hubs. - If there is a break in the cable, it does not disturb the other computers. ## Types of Telephone Transmission Media - **Twisted pair copper wire** - **Fiber optics** - **Microwave** - **Satellites** ## Peer-to-peer networks: 1. All computers on the network are treated as equals. 2. There are no file servers. 3. Users decide which files and peripherals to share. 4. They aren't suited for networks with many computers. 5. They are easy to set up. For example: Home networks. ## Client-server networks: 1. Typical corporate networks are client-server. 2. They use various topologies or physical layouts. 3. The network requires file servers, networked computers (clients), and a network operating system (NOS). 4. Clients send requests to servers for programs and data, and to access peripherals. ## Network media: 1. **Twisted pair:** Two insulated wires twisted around each other. The same type of wire used for telephones. 2. **Coaxial cable:** Consists of an insulated center wire surrounded by a layer of braided wire, used for cable TV. 3. **Fiber-optic cable:** A type of fiber-glass cable that transmits data in the form of light impulses. It can carry more data for longer distances than other wires. 4. **Infrared:** A wireless system that includes a transmitter and receiver for sending and receiving signals. 5. **Radio:** A wireless system that uses radio signals to send and receive data.