Computer Network Components and Protocols: A Comprehensive Guide
Computer Network Components
Hub
Collects all connections so that the failure of one does not affect the entire network. Two connection types: one for connecting stations and another for connecting with other hubs. Operates at the physical level of the OSI model. Does not analyze information, divide traffic, or disseminate information.
Bridge
Interconnects networks with different topologies and sub-network protocols. Operates at the link level of the OSI model with two different connectors, one for each network it interconnects. Transparent networks require no modifications. No changes are needed in the networks. Local and remote (allow physically remote network connection).
Switch
Operates at Level 2 (Datalink) of the OSI model. Connects computers per network. Performance is superior to bridges in network connections and superior to hubs in computer connections. Used in network segmentation to enhance performance and design virtual private networks.
Router
Hardware or software device that routes packets between network ports. Operates at level 3 (IP) and has one for each network it joins. Features include: 1) Packet filtering security (firewall), 2) Integration of physical technologies, enabling the connection of different networks, 3) Scalability of the network. The default path is used when no known route is found.
Gateway
Interconnects networks using different architectures. Operates at level 4 of the OSI model. Resolves: Incompatibility, error handling, connection type, and message size.
VLAN
Groups nodes connected to switches and manages them as a logical router. Separates users sharing the same medium. Advantages: Increased network speed, bandwidth, and security. Set up by: MAC addresses, ports, or virtual addressing. Standard 802.1q.
Wireless Networks
Signal transmission occurs over the air. Lower bandwidth and security. Standard IEEE 802.11. Wi-Fi networks have an unorganized topology, while WiMAX networks are based on the IEEE 802.16 standard, serving metropolitan networks and enabling Wi-Fi network interconnection.
Routing Table
Every network node has one. The default path is used if others don’t respond. ‘Route’ command adds, deletes, and prints. Composed of two columns: destination and next hop. Three address types: IP, network, or default route. Two IP address types: 0.0.0.0 (broadcast) or an IP address the router will join.
Network Protocols
Joint Protocol
Standards ensuring both parties understand communication. Structured in layers.
OSI Model
Defines a structured modern network architecture. Seven layers divided into three blocks: Application (application, presentation, session), Transport (transport), and Transmission (network, link, physical).
Application Layer
Handles network requests from applications and passes them to the presentation layer (e.g., DNS or FTP).
Presentation Layer
Addresses data format, compression, encoding, and encryption.
Session Layer
Establishes sessions between communication endpoints.
Transport Layer
Controls data flow between communication endpoints (e.g., TCP or UDP).
Network Layer
Channels data to its destination. Determines priorities, chooses the best route (e.g., IP).
Link Layer
Controls data flow between adjacent nodes, speed, and error control.
Physical Layer
Converts bytes to the physical environment and vice versa. Operates with signals.
TCP/IP Protocols
Enables seamless communication with any device globally, regardless of physical characteristics. A de facto standard with four layers.
ARP (Address Resolution Protocol)
Resolves IP addresses to MAC addresses.
RARP (Reverse Address Resolution Protocol)
Obsolete. Obtained IP addresses from MAC addresses. Unnoticed by the user.
ICMP (Internet Control Message Protocol)
Manages control messages between networks. Reports errors.
IP (Internet Protocol)
Enables data communication through a packet-switched network without prior connection. Connectionless and uses datagrams (up to 64kb) as the basic transfer unit. Current version: IPv6 (extended IPv4).
TCP (Transmission Control Protocol)
Provides secure communication through a reliable, connection-oriented service.
UDP (User Datagram Protocol)
Unreliable, connectionless transport protocol. Used for speed in communication.
IP Address
Identifies each computer within a network (local, global, or internet). Public or private. Static or dynamic. Private address ranges: A (10.0.0.0), B (172.16.0.0 – 172.31.0.0), C (192.168.0.0 – 192.168.255.0).
Subnet Mask
Defines how many bits of an IP address are used for the network and how to identify the host. Network bits are represented by 1s, host bits by 0s (not interleaved). Examples: A (255.0.0.0), B (255.255.0.0), C (255.255.255.0).
Network Troubleshooting Commands
PING
Diagnoses the connection between the network and a remote IP.
TRACERT
Displays all intermediate IP addresses a packet passes through between the local computer and the specified IP address.
IPCONFIG
Displays or updates the TCP/IP configuration.
NETSTAT
Displays the status of TCP/IP on the local computer.
ROUTE
Displays or modifies the routing table.
ARP
Displays and updates the IP-to-MAC address resolution cache.
NBTSTAT
Displays Lmhosts file content, protocol statistics, and TCP/IP knowledge using NBT (NetBIOS over TCP/IP).
TELNET
Allows terminal mode access to a remote host.
HOSTNAME
Displays the client machine name.
FTP
Downloads files.