Topic C02-Network Protocols

Network protocol can be defined as a set of rules that determine how data is transmitted between different devices in the same network.

Network protocols are the main reasons why we can easily communicate with people all over the world, and thus play a critical role in modern digital communications.

Application layer:

  • It is used by end-user software such as web browsers and email clients.
  • Provides protocols that allow software to send and receive information and present meaningful data to users.
Application layer Protocol: HTTP
  • HTTP stands for hypertext transfer protocol.
  • Hypertext means there are documents or files involved.
  • Transfer means the files can move over the world wide web from one networked device to another.
  • Protocol means the set of rules governing communication in networks.
  • Communication between client computers and web servers is done by sending HTTP requests and receiving HTTP Responses.
  • Hyper Transfer Protocol Secure (https) is a combination of the Hypertext Transfer Protocol (HTTP) with the Secure Socket Layer (SSL)/ Transport Layer Security (TLS) protocol.
Application Layer Protocol: FTP
  • FTP stands for "File Transfer Protocol" and refers to a group of rules that governs how computers transfer files from one system to another over the internet.
  • Businesses uses FTP to send files between computers while websites use it for uploading and downloading of file from their website's transfer.
  • During an FTP transmission, there are four commands used by the computers, servers, or proxy servers that are communicating. These are "sent", "get", "change directory", and "transfer".
Application Layer Protocol: DNS
  • DNS stands for Domain Name System
  • It is the phonebook of the internet. Humans access information online through domain names such as github.com or espn.com.
  • Web browsers interact through Internet Protocol addresses. DNS translates domain names to IP addresses so that browsers can load internet resources.
  • Each device connected to the internet has got a unique IP address.
  • DNS servers eliminates the need to memorize IP addresses such as 192.168.1.1.
Application Layer Protocol: SMTP
  • SMTP stands for Simple Mail Transfer Protocol.
  • Is a set of communication guidelines that allow software to transmit an electronic mail over the internet.
  • Is a program based on sending messages to other computers users based on e-mail addresses.
  • Its main purpose is to set up communication rules between servers.
  • Also has a way of handling the errors such as incorrect email address.
Application Layer Protocol: POP
  • It stands for Post Office Protocol.
  • It helps in retrieving messages from recipient server with the help of Message Access Agent.
  • The message Access Agent contains two types of protocols, i.e., POP3 and IMAP.
Application Layer Protocol: TELNET
  • Used for Terminal-to-terminal communication and inter-process communication.
  • Also used by other protocols (for example, FTP) for establishing a protocol control channel.
Transport Layer Protocol: TCP
  • Is better than UDP but due to it, it has an additional overhead.
  • Is used by application protocols like HTTP and FTP.
  • It relies on a three-way handshake (synchronization, synchronization acknowledgement, and final acknowledgement).
Transport Layer Protocol: UDP
  • Does not provide acknowledgement of sent packets like TCP.
  • It is not reliable and hence depends on the higher layer protocols.
  • It is simple, scalable and comes with lesser overhead as compared to TCP.
Network Layer Protocol: ARP
  • Stands for Address Resolution Protocol.
  • Used to associate IP address with the MAC address.
  • We need a MAC address for communication on a local area network.
  • MAC addresses are easily changeable.
Network Layer Protocol: RARP
  • Stands for Resolution Address Resolution Protocol
  • It helps in obtaining the IP address from a server.
  • The message format is sent from one machine to another encapsulated in the data portion of a frame.
Network Layer Protocol: ICMP
  • Stands for Internet Control Message Protocol.
  • Uses echo test/reply to check whether the destination is reachable and responding.
  • Its main function is to report the error but not to correct them.
  • It can send the messages only to the source, but not to the immediate routers.
Network Layer Protocol: IP
  • Data traversing the internet is divided into smaller pieces, called packets.
  • IP information is attached to each packet, and this information help routers to send packets to the right place.
  • Every device or domain that connect to the internet is assigned an IP address.
Network Access Layer Protocol: Ethernet
  • Used to create local area networks.
  • Transmits and receives data through cables.

IP Address
It is a unique identifier assigned to a device or domain that connects to the internet.

There are four different types of IP address:
Public, private, static, and dynamic.

  • Public and Private IP addresses are indicative of the location of the network-private for inside a network while a public for outside a network-static and dynamic indicates permanency.
  • A static IP address is manually created rather than being assigned and it does not change.
  • A dynamic IP address is assigned by a Dynamic Host Configuration Protocol (DHCP) server and is subject to change.
  • Dynamic IP addresses are only active for a certain period of time.

Versions of IP addresses:
IPv4
  • 32-bit IP address.
  • 4.3 billion addresses
  • Addresses must be reused and masked.
  • Numeric dot-decimal notation 192.168.1.1
  • DHCP or manual configuration
IPv6
  • 128-bit IP address.
  • 7.9*10^28 IP address.
  • Every device can have a unique IP address.
  • Alphanumeric hexadecimal notation 50b2:6400:0000:0000:6c3a:b17d:0000:10a9
  • Supports autoconfiguration.
Classes of IP addresses:
  • The value of the first octet determines the class.
  • There are five classes which includes (A, B, C, D, and E).
  • IP address 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.
Classes of IP addresses:
Class A: starts from 0 and ends at 127.
Class B: starts from 128 and ends and 191.
Class C: starts from 192 and ends at 223.
Class D: starts from 224 and ends at 239.
Class E: starts from 240 and ends at 255.

In order for devices to be on the same network, the first number of their IP address has to be the same for both devices.

Subnetting
Is a technique for logically partitioning a single physical network into multiple smaller sub-networks or subnets.
Every device has an IP address with two pieces: the client or host address and the server or network address.
The device called a gateway, or a default gateway connects local devices to other networks.

Subnet Mask
A 32-bit IP address uniquely identifies a single device on an IP network.
The 32 binary bits are divided into the host and network sections by the subnet mask, but they are also broken into four 8-bit octets.
The 255 address is always assigned to a broadcast address, while the 0 to network address.
Neither of them can be assigned to hosts as they are reserved for these special purposes.

Classful Routing
It does not import subnet mask.
It is an IP address allocation method that allocates IP addresses according to five major classes.
In classful routing, subnet mask is same throughout, does not vary for all devices.

Classless Routing
It is an IP address allocation method that is designed to replace classful addressing to minimize the rapid exhaustion of IP address.
It imports subnet mask.
Hello messages are used for checking status.
It is not same throughout; it may vary for all devices.



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