Networking Basics What is Computer Networking • Computer Network is an interconnection between computers, or we can say computer network is group of computers linked to each other which enables one computer to communicate with another computer. It acts as basis of communication in Information Technology (IT). It is system of connected computing devices and shares information and resources between them. The devices in network are connected by communication links (wired/wireless) and share data by Data Communication System. Network Types LAN(Local Area Network) • Local Area Network is a group of computers connected to each other in a small area such as building, office. • LAN is used for connecting two or more personal computers through a communication medium such as twisted pair, coaxial cable, etc. • It is less costly as it is built with inexpensive hardware such as hubs, network adapters, and ethernet cables. • The data is transferred at an extremely faster rate in Local Area Network. • Local Area Network provides higher security. PAN(Personal Area Network) • Personal Area Network is a network arranged within an individual person, typically within a range of 10 meters. • Personal Area Network is used for connecting the computer devices of personal use is known as Personal Area Network. • Personal computer devices that are used to develop the personal area network are the laptop, cell phones, media player and play stations MAN(Metropolitan Area Network) • A metropolitan area network is a network that covers a larger geographic area by interconnecting a different LAN to form a larger network. • Government agencies use MAN to connect to the citizens and private industries. WAN(Wide Area Network) • A Wide Area Network is a network that extends over a large geographical area such as states or countries. • A Wide Area Network is quite bigger network than the LAN. • A Wide Area Network is not limited to a single location, but it spans over a large geographical area through a telephone line, fiber optic cable or satellite links. • A Wide Area Network is widely used in the field of Business, government, and education. Virtual Networking • Network virtualization is the transformation of a network that was once hardware-dependent into a network that is softwarebased. • The goal of virtualization is to emulate physical environments and devices without actually having those physical elements. Wired and Wireless Network Topologies • A topology refers to a network’s physical and logical layout. A network’s physical topology refers to the actual layout of the computer cables and other network devices. • A network’s logical topology refers to the way in which the network appears to the devices that use it. Several topologies are in use on networks today. Some of the more common topologies are the bus, ring, star, mesh, and wireless. The following sections provide an overview of each. Bus Topology • A bus topology uses a trunk or backbone to connect all the computers on the network, as shown below. • Systems connect to this backbone using T connectors or taps (known as a vampire tap, if you must pierce the wire). To avoid signal reflection, a physical bus topology requires that each end of the physical bus be terminated, with one end also being grounded. Note that a hub or switch is not needed in this installation. Ring Topology • The ring topology is a logical ring, meaning that the data travels in a circular fashion from one computer to another on the network. Star Topology • In the star topology, all computers and other network devices connect to a central device called a hub or switch and, for that reason, is sometimes called a hub-and-spoke network. Each connected device requires a single cable to be connected to the hub or switch, creating a point-to-point connection between the device and the hub or switch. Mesh Topology • The wired mesh topology incorporates a unique network design in which each computer on the network connects to every other, creating a point-topoint connection between every device on the network. The OSI Networking Model Physical Layer (Layer 1) • Physical Layer (Layer 1) The physical layer of the OSI model identifies the network’s physical characteristics, including the following specifications: Hardware: The type of media used on the network, such as type of cable, type of connector, and pinout format for cables. Data Link Layer (Layer 2) • The data link layer is responsible for getting data to the physical layer so that it can transmit over the network. The data link layer is also responsible for error detection, error correction, and hardware addressing. Network Layer (Layer 3) • The primary responsibility of the network layer is routing— providing mechanisms by which data can be passed from one network system to another. Transport Layer (Layer 4) • The basic function of the transport layer is to provide mechanisms to transport data between network devices. • Primarily, it does this in three ways: • Error checking: Protocols at the transport layer ensure that data is correctly sent or received. • Service addressing: A number of protocols support many network services. The transport layer ensures that data is passed to the right service at the upper layers of the OSI model. • Segmentation: To traverse the network, blocks of data need to be broken into packets of a manageable size for the lower layers to handle. This process, called segmentation, is the responsibility of the transport layer. Session Layer (Layer 5) • The session layer is responsible for managing and controlling the synchronization of data between applications on two devices. It does this by establishing, maintaining, and breaking sessions. Presentation Layer (Layer 6) • The presentation layer’s basic function is to convert the data intended for or received from the application layer into another format. Such conversion is necessary because of how data is formatted so that it can be transported across the network. • Graphics files: JPEG, TIFF, GIF, and so on are graphics file formats that require the data to be formatted in a certain way. Text and data: The presentation layer can translate data into different formats, such as American Standard Code for Information Interchange (ASCII) and Extended Binary Coded Decimal Interchange Code (EBCDIC).sported across the network. • Sound/video: MPEG, MP3, and MIDI files all have their own data formats to and from which data must be converted. Application Layer (Layer 7) • Provides access to the network for applications • Incoming information is passed to the application layer, which then displays the information to the users. • Some of the most basic application layer services include file and print capabilities. What is the Difference Between TCP and UDP? Common Network Ports Domain Name System (DNS) Domain Name Service—resolves hostnames, such as www.pearsonitcertification.com, to IP addresses, such as 168.146.67.180. By default, DNS operates on port 53 Dynamic Host Configuration Protocol (DHCP) On an IP network, each device connected to the Internet must be assigned a unique IP address. DHCP helps network administrators to monitor and assign IP addresses in a centralized manner. It can automatically assign a new IP address to a computer when it is moved to another location. Simple Network Management Protocol(SNMP) The Simple Network Management Protocol (SNMP) uses port 161 to send data and port 162 to receive it. It enables network devices to communicate information about their state to a central system. It also enables the central system to pass configuration parameters to the devices. POP3/IMAP4 POP3 and IMAP4 are popular, and many people access email through applications that are POP3 and IMAP4 clients. The default port for POP3 is 110, and for IMAP4, the default port is 143. Simple Mail Transfer Protocol (SMTP) SMTP can be used to both send and receive mail. Post Office Protocol version 3 (POP3) and Internet Message Access Protocol version 4 (IMAP4) can be used only to receive mail. The default port used by SMTP is 25. SSH (Secure Shell) The SSH protocol uses encryption to secure the connection between a client and a server. All user authentication, commands, output, and file transfers are encrypted to protect against attacks in the network. The SSH port is 22 Telnet Telnet is a protocol that allows you to connect to remote computers (called hosts) over a TCP/IP network (such as the internet). Using telnet client software on your computer, you can make a connection to a telnet server (that is, the remote host). Once your telnet client establishes a connection to the remote host, your client becomes a virtual terminal, allowing you to communicate with the remote host from your computer. The default SSH port is 22. Main difference Understanding Port Functions • Each TCP/IP or application has at least one default port associated with it. When a communication is received, the target port number is checked to determine which protocol or service it is destined for. The request is then forwarded to that protocol or service. For example, consider HTTPS, whose assigned port number is 443. When a web browser forms a request for a secure web page, that request is sent to port 443 on the target system. When the target system receives the request, it examines the port number. When it sees that the port is 443, it forwards the request to the web server application. • TCP/IP has 65,535 ports available, with 0 to 1023 labeled as the well-known ports. Although a detailed understanding of the 65,535 ports is not necessary for the Network+ exam, you need to understand the numbers of some well-known ports. Network administration often requires you to specify port assignments when you work with applications and configure services. Addressing, Routing, and Switching IP Addressing To communicate on a network using TCP/IP, each system must be assigned a unique address. The address defines both the number of the network to which the device is attached and the number of the node on that network. In other words, the IP address provides two pieces of information. It’s a bit like a street name and house number in a person’s home address. ping • Ping (or ping) is the most known network troubleshooting command and is available for all operating systems with networking capabilities. • Ping sends an ICMP echo request to a host computer over an IP network. If the host is reachable, it sends back an ICMP echo reply, and reports the time it took to reach the host and other data such as errors or packet loss. • To use the ping command, go to the command prompt and enter ‘ping’ followed by the IP address or the URL. For example: • ping www.facebook.com tracert/traceroute • As the name suggests, tracert or traceroute traces the route between a source and the destination. It reports back the IP addresses of all the routers involved. • In Windows systems, type tracert followed by hostname. • For example: tracert www.wikipedia.com ipconfig • ipconfig is a tools used to determine the TCP/IP network configuration of Windows or macOS systems and Linux systems, respectively. The command displays the IP address, subnet mask, and the default gateway bound to each adapter. • To use the command on a Windows system, head to the command prompt and type ipconfig nslookup • nslookup is a network administration tool used to diagnose DNS issues. The tool looks up DNS records and how they map to IP addresses. It also has further options to look up the domain admin's email address, serial number, and other information. The tool is available for Windows, Linux, and ReactOS systems. • To use the tool, simply type nslookup followed by the domain name. For example: • nslookup www.google.com netstat • netstat is another command-line tool to find the network statistics for your entire infrastructure. It displays the network connections for TCP, routing tables, and the network protocols used. The tool is available on almost all systems, including Windows, macOS, Linux, and IBM OS. • To use the protocol, go to the command prompt and type netstat Common Networking Devices Firewall A firewall is a networking device, either hardware or software based, that controls access to your organization’s network. This controlled access is designed to protect data and resources from an outside threat. To provide this protection, firewalls typically are placed at a network’s entry/exit points—for example, between an internal network and the Internet. After it is in place, a firewall can control access into and out of that point. IDS/IPS An intrusion detection system (IDS) is a passive detection system. The IDS can detect the presence of an attack and then log that information. It also can alert an administrator to the potential threat. The administrator then analyzes the situation and takes corrective measures if needed A variation on the IDS is the intrusion prevention system (IPS), which is an active detection system. With IPS, the device continually scans the network, looking for inappropriate activity. It can shut down any potential threats. The IPS looks for any known signatures of common attacks and automatically tries to prevent those attacks. Router In a common configuration, routers create larger networks by joining two network segments. A small office/home office (SOHO) router connects a user to the Internet. A SOHO router typically serves 1 to 10 users on the system. A router can be a dedicated hardware device or a computer system with more than one network interface and the appropriate routing software Switch A network switch forwards data packets between devices. Switches send packets directly to devices, rather than sending them to networks like a router does. In practice, what this means is that routers are necessary for an Internet connection, while switches are only used for interconnecting devices. Bridge The primary responsibility of a switch is to examine the incoming traffic and determine whether to filter or forward it. Access Point In computer networking, a wireless access point, or more generally just access point, is a networking hardware device that allows other Wi-Fi devices to connect to a wired network. . Repeater/Wi-Fi Extender In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Load Balancer Load balancing is a technique in which the workload is distributed among several servers. This feature can take networks to the next level; it increases network performance, reliability, and availability Types of Network Media Types of Network Media Whatever type of network is used, some type of network medium is needed to carry signals between computers. Two types of media are used in networks: cablebased media, such as twisted-pair, and the media types associated with wireless networking, such as radio waves. Twisted-Pair Cabling (Copper) Coaxial Cables Coaxial cable, or coax as it is commonly called, has been around for a long time. Coax found success in both TV signal transmission and network implementations. Fiber-Optic Cables Fiber-optic cable, although still more expensive than other types of cable, is well suited for high-speed data communications. It eliminates the problems associated with copper-based media, such as near-end crosstalk, EMI, and signal tampering. Troubleshooting Tools A large part of network administration involves having the right tools for the job and knowing when and how to use them. Selecting the correct tool for a networking job sounds like an easy task, but network administrators can choose from a mind-boggling number of tools and utilities. Punchdown Tools Punchdown tools are used to attach twisted-pair network cable to connectors within a patch panel. Tone Generator As you might expect, the purpose of the tone probe is to generate a signal that is transmitted on the wire you are attempting to locate. Loopback Adapter The loopback adapter is a dummy network card that is used as a testing tool for virtual network environments where network access is not available or when you want to isolate your testing network from your main network. OTDR An Optical Time Domain Reflectometer (OTDR) is a device that tests the integrity of a fiber cable and is used for the building, certifying, maintaining, and troubleshooting fiber optic systems. Multimeter A basic multimeter combines several electrical meters into a single unit that can measure voltage, current, and resistance. Advanced models can also measure temperature. Tap A network tap is a system that monitors events on a local network. A tap is typically a dedicated hardware device, which provides a way to access the data flowing across a computer network. Wireless Channels and Frequencies Wireless Channels and Frequencies It is recommended that nonoverlapping channels be used for communication. In the United States, 802.11b/g standards use 11 channels for data communication, as mentioned; three of these— channels 1, 6, and 11—are nonoverlapping. Most manufacturers set their default channel to one of the nonoverlapping channels to avoid transmission conflicts. With wireless devices you can select which channel your WLAN operates on to avoid interference from other wireless devices that operate in the 2.4 GHz frequency range. Cloud Computing Software as a Service • Software as a service (SaaS) allows users to connect to and use cloudbased apps over the Internet. Common examples are email, calendaring, and office tools (such as Microsoft Office 365). • SaaS provides a complete software solution that you purchase on a payas-you-go basis from a cloud service provider. You rent the use of an app for your organization, and your users connect to it over the Internet, usually with a web browser. Platform as a Service Platform as a Service (PaaS) provides a runtime environment. It allows programmers to easily create, test, run, and deploy web applications. You can purchase these applications from a cloud service provider on a pay-as-per use basis and access them using the Internet connection. In PaaS, back-end scalability is managed by the cloud service provider, so end- users do not need to worry about managing the infrastructure. Examples: • • • • • • • Google Cloud Microsoft Azure AWS IBM Cloud Red Hat OpenShift VMware (Pivotal) Cloud Foundry Oracle Cloud Platform (OCP) Infrastructure as a Service Infrastructure as a service (IaaS) is a type of cloud computing service that offers essential compute, storage, and networking resources on demand, on a pay-as-you-go basis. Private Cloud • The private cloud is defined as computing services offered either over the Internet or a private internal network and only to select users instead of the general public. • Under most circumstances, a private cloud is owned by the organization, and it acts as both the provider and the consumer. It has a security-related advantage in not needing to put its data on the Internet. Public Cloud The cloud resources (like servers and storage) are owned and operated by a third-party cloud service provider and delivered over the internet. With a public cloud, all hardware, software and other supporting infrastructure are owned and managed by the cloud provider. Microsoft Azure is an example of a public cloud. Hybrid cloud • Hybrid cloud refers to a mixed computing, storage, and services environment made up of on-premises infrastructure, private cloud services, and a public cloud—such as Amazon Web Services (AWS) or Microsoft Azure—with orchestration among the various platforms. Using a combination of public clouds, onpremises computing, and private clouds in your data center means that you have a hybrid cloud infrastructure.
