Computer Network Components

Fundamentals of Communication Networks: Part 4/5

• Components of a computer network are examined.
• A classification of transmission media is provided.
• Cabling and connectors and interconnection elements are explained.
• Network cards and MAC addressing information is included.
• Switches, routers, and intrusion detection systems (IDS) are explained

Components of a Computer Network

• A network includes computers with operating systems, hardware, and software that enable network functionality.
• Network components include network cabling, connectors for signal transmission, racks for electronic and IT equipment, patch panels for cable termination and organization, and network cards for wired or wireless computer connections.
• Additional components are switches for connecting computers and network segments, routers for connecting different networks and access points for wireless device interconnection.
• Firewalls can be hardware or software designed to block unauthorized network access.
• Servers function as computers with specific operating systems.
• Computers on a network are referred to as work stations
• Devices such as printers, network hard drives, and peripherals connected to a network computer are termed network nodes.

Media Classification and Transmission

• Transmission medium constitutes the channel for information transmission between two terminals.
• Transmissions commonly use electromagnetic waves propagating through the channel.
• A physical medium may or may not be the channel because electromagnetic waves can transmit through a vacuum.
• Guided media conducts electromagnetic waves through a physical path.
• Unguided media supports wave transmission without directing them.
• Guided media includes different types of cables- twisted pair, coaxial, and fiber optic which can be utilized for this purpose.
• Unguided media enable wireless networks and telecommunications without cables such as mobile internet connections.

Cabling and Connectors

• The commonly used cable in local area networks is Ethernet cable, comprised of eight differently colored wires twisted and used in computer networks under the IEEE 802.3.
• Wire colors are white-orange, orange, white-green, green, white-blue, blue, white-brown, and brown with standardized connector connections.
• The RJ-45 connector is used and is available with male and female ends.
• Coaxial cable contains a conducting wire core, an external mesh, and a dielectric insulation.
• BNC and Type N connectors are typically used, and several standards exits based on usage.
• Coaxial cable is now rarely used in computer networks, it's used for TV, Cable Internet distribution.
• RG6 is a type of cable is deployed to connect Internet distribution to homes and supports configurations for telephone and data transmission.
• Fiber optic cables are thin strands of transparent material like glass or plastic that transmits data through light pulses.
• Lasers or LEDs are used as the light source; lasers are more frequent in computer networks.
• Fiber optic cables transmit large data volumes across long distances at high speeds and are immune to electromagnetic interference.
• Fiber optic cables are utilized in telecommunication signal distribution over long reaches and in local networks as a signal distribution backbone.
• Multimode and monomode are two types of fiber optic cable. The core difference lies in how they transmit light, affecting transmission distance and speed.
• Connectors like FC and FDDI can be used

Fiber Optic Cables: Monomode vs. Multimode

• Monomode fiber supports long distances, multimode supports short distances.
• Monomode reduces signal distortion, enabling long distance data transmission at high speed, multimode experiences increased signal dispersion/weakening over longer distances.
• Fiber optic multimode cables are more suited to short distance, whereas the monomode are suited for long networks.

Structured Cabling

• A telecommunications infrastructure that connects a building. Includes cables, raceways, cabinets, and specific spaces.
• Structured cabling is composed of defined subsystems to organize the installation
• The different Subsystems are: campus cabling or building interconnection, the point where outside cables connect to interior ones, the room where all building connections are distributed, or equipment room.
• Backbone cabling is vertical distribution cabling between floors.
• Distribution cabinets are where cables converge and interconnection equipment is set-up, using racks and patch panels.
• Horizontal cabling is the cabling on each floor of a building in the work area.

Structured Cabling Standards

• Standards exist for structured cabling and specify the type of cable, connectors, the maximum segment lengths, layout of devices etc.
• The recommendation for horizontal cabling is a maximum of 100 meters from the distribution cabinet or rack.
• The ANSI/EIA/TIA 568 A and B standard defines color distribution when connecting twisted pair cables to RJ-45 connectors.
• Network connections should direct cables meaning both ends follow same 568 standard (568B recommended).
• Use 568A on one end and 568B on the other for a cross-over cable.
• Cross-over cables are used to connect devices of the same type.

Interconnection Elements

• Interconnection elements are those that allow you to connect equipment on the network.
• At the physical level: network cards, wired or wireless, connect equipment to the network; hubs send data to multiple computers; repeaters regenerate and/or amplify signal.
• At the data link level: switches connect network segments and computers more efficiently than a hub, sending information only to the necessary computer; bridges connect sub-networks, transferring only the non-local traffic; access points connect wireless and wired elements and allow wireless devices to connect to wired networks.
• At the network level: routers connect different networks.
• Routers connect networks and their primary utility is providing Internet connections, enabling local networks to connect.
• Routers use the IP protocol and thus need at least two IP addresses for the Internet and the local networks.
• Routers are also able to provide wireless access point services

Higher Level Elements and Gateways

• Gateways are interconnection equipment that work at the higher levels of the OSI model.
• Gateways can connect networks of differing technologies, facilitate network admittance, handle access control, and act as servers or firewalls.

Network Cards and MAC addressing

• NIC (Network Interface Card/Adaptor) allows communication and resource sharing between connected devices.
• Function: allows connection of computer to network. Protocols required for this are stored on the card.
• Every network card has a unique, built-in 48-bit MAC address, which is the physical address at the data link level.
• The cards connect to equipment using internal buses like PCI or external buses like USBs. They can also be integrated in the motherboard.
• The network card must know the transmission speed, amount of info to transmit, what protocols to use, the physical parameters, and transform the info which arrives via the connection, by converting it into a serial bit sequence, conveniently coded, in order to form an appropriate signal.
• Common components consist of the main processor a transceiver to access media , a wake on LAN connector, a status indicator and a connection for cabled/in-cabled networks.

Card Installation

• Installation and configuration depend on the operating system, but generally need an IP address.
• The network mask and gateway must also be configured.
• The MAC and IP addresses allow a computer to be identified on the network.

Switches

• A switch is an interconnection element that operates at layer 2 (data link level).
• It lets you connect two or more network segments, letting the user hook-up different computers so that they can connect with each other and access other network segments
• The switch functions by storing the MAC addresses of computers connected to it and devices in each segment.
• The switch connects computers effectively without sending the information across the whole network.

Advantages/disadvantages of switches

• High connection speeds and simultaneous transmissions occur, allowing more than two computers to be connected at the same time.
• The limitations of switches restrict connecting to devices, network, or computers with the same topology but they may work at differing speeds.
• Layer 3 switches combine speed with the ability to choose optimal paths between devices and may define virtual LANs which are logically independent within a physical network.

Routers

• A router connects two different networks.
• The router operates at level 3, directing network traffic to find the best path to its destination.
• It works by using packets which contain data for the original and destination IP addresses as well as the message's proper data.
• Each router port or interface connects to a different computer with at least two IP addresses.

Router Capabilities

• Routers connect different networks with filtering, address translation, and conmutating functions.
• A router stores information about accessible networks in the routing table, which shows how to move from one network to another using an interface.
• Windows allows the use of "route print" or "netstat -r" commands to view the host’s routing table.

Intrusion Detection Systems (IDS)

• An IDS is an application to detect unauthorized computer/network access.
• Security measures are needed to prevent unauthorized operation or data acquisition, which an IDS delivers.
• There exists two types of security measures and they are: N-IDS is the system to detect unauthorized access to networks and the H-IDS works to detect unauthorized computer/host access.
• N-IDS need hardware to check for traffics for networks and an example of their solutions is integrating N-IDS for the firewalls. H-IDS has integrated to the operation system.

Intrusion Detection Systems vs Intrusion Prevention Systems

• While IDS detect network intrusions, they don't prevent them, while firewalls limit intrusions but don't detect them. Combining the two can be a great option for maximum network security.
• The newer trend is the Intrusion Prevention System (IPS) approach. Which not only detects an intrusion but also prevents it from occurring.
• Intrusion detection and prevention are available as both software.