WHAT IS A NETWORK OR IP ADDRESS?

An Internet Protocol address (IP address) is a numerical label assigned to each device connected to a computer networkAn Internet Protocol address (IP address) is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.An IP address serves two main functions: host or network interface identification and location addressing.

The IP address space is managed globally by the Internet Assigned Numbers Authority (IANA), and by five regional Internet registries (RIRs) responsible in their designated territories for assignment to local Internet registries, such as Internet service providers, and other end users. IPv4 addresses were distributed by IANA to the RIRs in blocks of approximately 16.8 million addresses each, but have been exhausted at the IANA level since 2011. Only one of the RIRs still has a supply for local assignments in Africa. Some IPv4 addresses are reserved for private networks and are not globally unique.

IP addresses are written and displayed in human-readable notations, such as 172.16.254.1 in IPv4, and 2001:db8:0:1234:0:567:8:1 in IPv6. The size of the routing prefix of the address is designated in CIDR notation by suffixing the address with the number of significant bits, e.g., 192.168.1.15/24, which is equivalent to the historically used subnet mask 255.255.255.0.

Each network that runs TCP/IP must have a unique network number. Every machine on the network must have a unique IP address. You must understand how IP addresses are constructed before you register your network and obtain its network number. This section describes IPv4 addresses. For information on IPv6 addresses, see IPv6 Addressing. The IPv4 address is a 32-bit number that uniquely identifies a network interface on a machine. An IPv4 address is typically written in decimal digits, formatted as four 8-bit fields that are separated by periods. Each 8-bit field represents a byte of the IPv4 address. This form of representing the bytes of an IPv4 address is often referred to as the dotted-decimal format.

Network administrators assign an IP address to each device connected to a network. Such assignments may be on a static (fixed or permanent) or dynamic basis, depending on network practices and software features.

2 TYPES OF IP VERSIONS

Internet Protocol version 4 (IPv4) defines an IP address as a 32-bit number. However, because of the growth of the Internet and the depletion of available IPv4 addresses, a new version of IP (IPv6), using 128 bits for the IP address, was standardized in 1998. IPv6 deployment has been ongoing since the mid-2000s.

The bytes of the IPv4 address are further classified into two parts: the network part and the host part. The following figure shows the component parts of a typical IPv4 address, 129.144.50.56.

Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. IPv6 was developed by the Internet Engineering Task Force (IETF) to deal with the long-anticipated problem of IPv4 address exhaustion. IPv6 is intended to replace IPv4. In December 1998, IPv6 became a Draft Standard for the IETF who subsequently ratified it as an Internet Standard on 14 July 2017.

Devices on the Internet are assigned a unique IP address for identification and location definition. With the rapid growth of the Internet after commercialization in the 1990s, it became evident that far more addresses would be needed to connect devices than the IPv4 address space had available. By 1998, the Internet Engineering Task Force (IETF) had formalized the successor protocol. IPv6 uses a 128-bit address, theoretically allowing 2128, or approximately 3.4×1038 addresses. The actual number is slightly smaller, as multiple ranges are reserved for special use or completely excluded from use. The two protocols are not designed to be interoperable, and thus direct communication between them is impossible, complicating the move to IPv6. However, several transition mechanisms have been devised to rectify this.

IPv6 provides other technical benefits in addition to a larger addressing space.In particular, it permits hierarchical address allocation methods that facilitate route aggregation across the Internet, and thus limit the expansion of routing tables. The use of multicast addressing is expanded and simplified, and provides additional optimization for the delivery of services. Device mobility, security, and configuration aspects have been considered in the design of the protocol.

IPv6 addresses are represented as eight groups, separated by colons, of four hexadecimal digits. The full representation may be simplified by several methods of notation; for example, 2001:0db8:0000:0000:0000:8a2e:0370:7334 becomes 2001:db8::8a2e:370:7334.

Classes of IP Address

TCP/IP defines five classes of IP addresses: class A, B, C, D, and E. Each class has a range of valid IP addresses. The value of the first octet determines the class. IP addresses from the first three classes (A, B and C) can be used for host addresses. The other two classes are used for other purposes – class D for multicast and class E for experimental purposes.

The system of IP address classes was developed for the purpose of Internet IP addresses assignment. The classes created were based on the network size. For example, for the small number of networks with a very large number of hosts, the Class A was created.The Class C was created for numerous networks with small number of hosts.

Classes of IP addresses are:

For the IP addresses from Class A, the first 8 bits (the first decimal number) represent the network part, while the remaining 24 bits represent the host part. For Class B, the first 16 bits (the first two numbers) represent the network part, while the remaining 16 bits represent the host part. For Class C, the first 24 bits represent the network part, while the remaining 8 bits represent the host part.

Sources: https://en.wikipedia.org/wiki/IP_address
               https://en.wikipedia.org/wiki/IPv4
               https://en.wikipedia.org/wiki/IPv6
               https://study-ccna.com/classes-of-ip-addresses/

WHAT IS THE DIFFERENCE BETWEEN STRAIGHT-THROUGH AND CROSSOVER CABLE?

Straight-through Cable

Is a type of twisted pair copper wire cable for local area network (LAN) use for which the RJ-45 connectors at each end have the same pinout (i.e., arrangement of conductors). It is identical to crossover cable, except that in the latter the wires on the cable are crossed over so that the receive signal pins on the connector on one end are connected to the transmit signal pins on the connector on the other end. Straight-through cable is also commonly referred to as patch cable. However, this might be confusing in some situations because patch cable also has a broader definition that emphasizes the fact that there is a connector on each end rather than the equality (or lack thereof) of the pinouts. Straight-through cable is used to connect computers and other end-user devices (e.g., printers) to networking devices such as hubs and switches. It can also be used to directly connect like devices (e.g., two hubs or two switches) if the cable is plugged into an uplink port on one (but not both) of the devices. Crossover cable is used to connect two like devices without the use of an uplink port.

Crossover Cable

Is a crossover cable for Ethernet used to connect computing devices together directly. It is most often used to connect two devices of the same type, e.g. two computers (via their network interface controllers) or two switches to each other. By contrast, patch cables or straight through cables are used to connect devices of different types, such as a computer to a network switch or Ethernet hub.

Intentionally crossed wiring in the crossover cable connects the transmit signals at one end to the receive signals at the other end.


Many devices today support auto MDI-X capability, wherein a patch cable can be used in place of a crossover cable, or vice versa, and the receive and transmit signals are reconfigured automatically within the devices to yield a working connection.

WHAT ARE THE TYPES OF CABLE?

Twisted Pair - is the ordinary copper wire that connects home and many business computers to the telephone company. To reduce crosstalk or electromagnetic induction between pairs of two wires, two insulated copper wires are twisted around each other.

TWO TYPES OF TWISTED PAIR:

 1. Shielded Twisted Pair - was originally designed by IBM for token ring networks that include two individual wires covered with a foil shielding, which prevents electromagnetic interference, thereby transporting data faster.

2. Unshielded Twisted Pair -  one of the least expensive wires and works for basic needs of phone systems, so it is one of the commonly installed in residential industries.

Coaxial Cable - is a type of copper cable specially built with a metal shield and other components engineered to block signal interference. It is primarily used by cable TV companies to connect their satellite antenna facilities to customer home and businesses.

Fiber Optic Cable - also known as optical fiber cable, is an assembly similar to an electrical cable, but containing one or more optical fibers that are used to carry light. The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube suitable for the environment where the cable will be deployed.