Paper on computer networks

1. What is a networking model?
The networking model describes the architecture, components, and design used to establish
communication between the source and destination systems. Aliases for network models include
protocol stacks, protocol suites, network stacks, and network protocols.
What Is the OSI Model?
The Open Systems Interconnection (OSI) model describes seven layers that computer systems use to
communicate over a network. It was the first standard model for network communications, adopted by
all major computer and telecommunication companies in the early 1980s The modern Internet is not
based on OSI, but on the simpler TCP/IP model. However, the OSI 7-layer model is still widely used,
as it helps visualize and communicate how networks operate, and helps isolate and troubleshoot
networking problems
TCP/IP Reference Model is a four-layered suite of communication protocols. It was developed by the
DoD (Department of Defence) in the 1960s. It is named after the two main protocols that are used in
the model, namely, TCP and IP. TCP stands for Transmission Control Protocol and IP stands for
Internet Protocol.
The four layers in the TCP/IP protocol suite are −
• Host-to- Network Layer −It is the lowest layer that is concerned with the physical transmission of
data. TCP/IP does not specifically define any protocol here but supports all the standard protocols.

2. • Internet Layer −It defines the protocols for logical transmission of data over the network. The main
protocol in this layer is Internet Protocol (IP) and it is supported by the protocols ICMP, IGMP, RARP,
and ARP.
• Transport Layer − It is responsible for error-free end-to-end delivery of data. The protocols defined
here are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).
• Application Layer − This is the topmost layer and defines the interface of host programs with the
transport layer services. This layer includes all high-level protocols like Telnet, DNS, HTTP, FTP,
SMTP, etc.
The following diagram shows the layers and the protocols in each of the layers –
A LAN (local area network) is a group of computers and network devices connected together, usually
within the same building. By definition, the connections must be high speed and relatively inexpensive
(e.g., token ring or Ethernet). Most Indiana University Bloomington departments are on LANs.
A MAN (metropolitan area network) is a larger network that usually spans several buildings in the same
city or town. The IUB network is an example of a MAN.
A WAN (wide area network), in comparison to a MAN, is not restricted to a geographical location,
although it might be confined within the bounds of a state or country. A WAN connects several LANs,
and may be limited to an enterprise (a corporation or an organization) or accessible to the public. The
technology is high speed and relatively expensive. The Internet is an example of a worldwide public
WAN.

3. The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol
suite for relaying datagrams across network boundaries. Its routing function enables internetworking,
and essentially establishes the Internet.
IP has the task of delivering packets from the source host to the destination host solely based on the IP
addresses in the packet headers. For this purpose, IP defines packet structures that encapsulate the
data to be delivered. It also defines addressing methods that are used to label the datagram with source
and destination information.
Address Resolution Protocol (ARP) is a protocol or procedure that connects an ever-changing
Internet Protocol (IP) address to a fixed physical machine address, also known as a media access
control (MAC) address, in a local-area network (LAN).
This mapping procedure is important because the lengths of the IP and MAC addresses differ, and a
translation is needed so that the systems can recognize one another. The most used IP today is IP
version 4 (IPv4). An IP address is 32 bits long. However, MAC addresses are 48 bits long. ARP
translates the 32-bit address to 48 and vice versa.
Reverse Address Resolution Protocol (RARP) is a network-specific standard protocol. It is described
in RFC 903. Some network hosts, such as a diskless workstation, do not know their own IP address
when they are booted. To determine their own IP address, they use a mechanism similar to ARP, but
now the hardware address of the host is the known parameter, and the IP address is the queried
parameter.
The reverse address resolution is performed the same way as the ARP address resolution. The same
packet format is used for the ARP.
An exception is the operation code field that now takes the following values−
• 3 for RARP request
• 4 for RARP reply
The physical header of the frame will now indicate RARP as the higher-level protocol (8035 hex) instead
of ARP (0806 hex) or IP-(0800 hex) in the Ether type field.
The User Datagram Protocol, or UDP, is a communication protocol used across the Internet for
especially time-sensitive transmissions such as video playback or DNS lookups. It speeds up
communications by not formally establishing a connection before data is transferred. This allows data
to be transferred very quickly, but it can also cause packets to become lost in transit — and create
opportunities for exploitation in the form of DDoS attacks.
TCP stands for Transmission Control Protocol a communications standard that enables application
programs and computing devices to exchange messages over a network. It is designed to send packets
across the internet and ensure the successful delivery of data and messages over networks. TCP is
one of the basic standards that define the rules of the internet and is included within the standards
defined by the Internet Engineering Task Force (IETF). It is one of the most commonly used protocols
within digital network communications and ensures end-to-end data delivery.

4. Stream Control Transmission Protocol With the peer connection, we have the ability to send quickly
video and audio data. The SCTP protocol is used today to send blob data on top of our currently setup
peer connection when using the RTCDataChannel object. SCTP is built on top of the DTLS (Datagram
Transport Layer Security) protocol that is implemented for each WebRTC connection. It provides an
API for the data channel to bind to. All of this sit on top of the UDP protocol which is the base transport
protocol for all WebRTC applications.
In layered architecture of Network Model, one whole network process is divided into small tasks.
Each small task is then assigned to a particular layer which works dedicatedly to process the task only.
Every layer does only specific work.
Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions
tasks or workloads between peers. Peers are equally privileged, equipotent participants in the
application. They are said to form a peer-to-peer network of nodes.[1]
Peers make a portion of their resources, such as processing power, disk storage or network bandwidth,
directly available to other network participants, without the need for central coordination by servers or
stable hosts.[2] Peers are both suppliers and consumers of resources, in contrast to the
traditional client–server model in which the consumption and supply of resources is divided.
Uni Polar: Unipolar
o Digital transmission system sends the voltage pulses over the medium link such as wire or cable.
o In most types of encoding, one voltage level represents 0, and another voltage level represents 1.
o The polarity of each pulse determines whether it is positive or negative.
Polar
o Polar encoding is an encoding scheme that uses two voltage levels: one is positive, and another is
negative.
o By using two voltage levels, an average voltage level is reduced, and the DC component problem of
unipolar encoding scheme is alleviated.

5. NRZ-L: In NRZ-L encoding, the level of the signal depends on the type of the bit that it represents. If a bit is 0 or
1, then their voltages will be positive and negative respectively. Therefore, we can say that the level of the signal
is dependent on the state of the bit.
NRZ-I: NRZ-I is an inversion of the voltage level that represents 1 bit. In the NRZ-I encoding scheme, a transition
occurs between the positive and negative voltage that represents 1 bit. In this scheme, 0 bit represents no
change and 1 bit represents a change in voltage level.
RZ
o RZ stands for Return to zero.
o There must be a signal change for each bit to achieve synchronization. However, to change with every
bit, we need to have three values: positive, negative and zero.

6. o RZ is an encoding scheme that provides three values, positive voltage represents 1, the negative
voltage represents 0, and zero voltage represents none.
Manchester
o It changes the signal at the middle of the bit interval but does not return to zero for synchronization.
o In Manchester encoding, a negative-to-positive transition represents binary 1, and positive-to-negative
transition represents 0.
o Manchester has the same level of synchronization as RZ scheme except that it has two levels of
amplitude.
Differential Manchester
o It changes the signal at the middle of the bit interval for synchronization, but the presence or absence of
the transition at the beginning of the interval determines the bit. A transition means binary 0 and no
transition means binary 1.
o In Manchester Encoding scheme, two signal changes represent 0 and one signal change represent 1.