Unit 3 : PROTOCOLS

Unit 3: PROTOCOLS

INTERNET Related PROTOCOLS: Need of IP address, Classes of IP Address.,Unicast, broad cast, multicast IP Addresses., Subnet Mask., Electronic mail, FTP, TFTP, SNMP,HTTP. ,Introduction to IPV4, IPV6 and its features. 

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INTERNET Related PROTOCOLS:

When most people talk about "the Internet" what they are really referring to is the World Wide Web. The Internet is actually composed of many different components. Some of the components are widely known, such as FTP, while others are not so familiar, such as Gopher and Telnet.

Several protocols are used on the Internet, including Electronic Mail (e-mail), File Transfer Protocol (FTP), HTTP (World Wide Web), News (or Usenet) etc. Each of these has its own standard and usage.

Electronic Mail

Included in the email protocol are three distinct protocols. SMTP (Simple Mail Transfer Protocol), IMAP (Internet Message Access Protocol) and POP3 (Post Office Protocol 3).

SMTP is a protocol used for sending mail, while IMAP and POP3 are used for receiving. Almost all Internet service providers support all three protocols. However the most popular setup for most providers is to use SMTP for sending mail while using POP3 for receiving.

File Transfer Protocol

File Transfer Protocol, or FTP, is a means of transferring a file from one computer to another. FTP is commonly used for uploading a web page to a web server so that it may be seen on the World Wide Web. A special program, called a client, is usually needed to use FTP.

Trivial File Transfer Protocol (TFTP):

Trivial File Transfer Protocol is very simple in design and has limited features as compared to File Transfer Protocol (FTP). TFTP provides no authentication and security while transferring files. As a result, it is usually used for transferring boot files or configuration files between machines in a local setup. Because of its simple design, it is rarely used interactively by users in a computer network. Its lack of security also makes it dangerous for use over the Internet.

TFTP is very useful for boot computers and devices that do not have hard disk drives or storage devices because it can easily be implemented using a small amount of memory. This characteristic of TFTP makes it one of the core elements of network boot protocol, or preboot execution environment (PXE).

HTTP (World Wide Web)

HyperText Transfer Protocol, or HTTP, is the protocol used by web server to allow web pages to be shown in a web browser. If you look up into the address bar of your web browser, the place where you type in the address that you want to visit, it has the prefix "http://" in front of the address. Because most web browsers are capable of FTP as well as viewing web pages, the http tells the browser what kind of information to expect.

Simple Network Management Protocol (SNMP):

Simple Network Management Protocol (SNMP) is an application-layer protocol used to manage and monitor network devices and their functions. SNMP provides a common language for network devices to relay management information within single- and multivendor environments in a local area network (LAN) or wide area network (WAN). The most recent iteration of SNMP, version 3, includes security enhancements that authenticate and encrypt SNMP messages as well as protect packets during transit.

One of the most widely used protocols, SNMP is supported on an extensive range of hardware -- from conventional network equipment like routers, switches and wireless access points to endpoints like printers, scanners and internet of things (IoT) devices. In addition to hardware, SNMP can be used to monitor services such as Dynamic Host Configuration Protocol (DHCP). Software agents on these devices and services communicate with a network management system (NMS), also referred to as an SNMP manager, via SNMP to relay status information and configuration changes.

While SNMP can be used in a network of any size, its greatest value is evident in large networks.

News (or Usenet)

Network News Transfer Protocol (NNTP) is used for serving Usenet posts Usenet is similar to the forums that many web sites have. Usenet has forums that are dedicated to specific companies as well as forums that have a wide range of topics. Usenet is divided into several areas. Some of the forums that are included in Usenet are comp. for discussion of computer-related topics, sci. for discussion of scientific subjects, rec. for discussion of recreational activities (e.g. games and hobbies) and talk. for discussion of contentious issues such as religion and politics.

Introduction to IP Address:

An IP address consists of four numbers; each can contain one to three digits. These numbers are separated with a single dot (.). These four numbers can range from 0 to 255.

Types of IP addresses

The IP addresses can be classified into two. They are listed below.

1) Static IP addresses

2) Dynamic IP addresses

Static IP Addresses

As the name indicates, the static IP addresses usually never change but they may be changed as a result of network administration. They serve as a permanent Internet address and provide a simple and reliable way for the communication. From the static IP address of a system, we can get many details such as the continent, country, region and city in which a computer is located, The Internet Service Provider (ISP) that serves that particular computer and non-technical information such as precise latitude and longitude of the country,  and the locale of the computer. There are many websites providing IP address lookups. You can find out your IP addresses at http://whatismyip.org/.

Dynamic IP Addresses

Dynamic IP address are the second category. These are temporary IP addresses. These IP addresses are assigned to a computer when they get connected to the Internet each time. They are actually borrowed from a pool of IP addresses, shared over various computers. Since limited number of static IP addresses are available, ISPs usually reserve the portion of their assigned addresses for sharing among their subscribers in this way.

Static IP addresses are considered as less secure than dynamic IP addresses because they are easier to track.

IP address and classes

The IP hierarchy contains many classes of the IP addresses. Broadly, the IPv4 addressing system is divided into five classes of IP address. All the five classes are identified by the first octet of the IP address.

The classes of IPv4 addresses

The different classes of the IPv4 address are the following:

1) Class A address

2) Class B address

3) Class C address

4) Class D address

5) Class E address

Class A Address

The first bit of the first octet is always set to zero. So that the first octet ranges from 1 – 127. The class A address only include IP starting from 1.x.x.x to 126.x.x.x. The IP range 127.x.x.x is reserved for loop back IP addresses. The default subnet mask for class A IP address is 255.0.0.0. This means it can have 126 networks (27-2) and 16777214 hosts (224-2).

Class A IP address format is thus: 0NNNNNNN.HHHHHHHH.HHHHHHHH.HHHHHHHH.

Class B Address

Here the first two bits in the first two bits is set to zero. Class B IP Addresses range from 128.0.x.x to 191.255.x.x. The default subnet mask for Class B is 255.255.x.x. Class B has 16384 (214) Network addresses and 65534 (216-2) Host addresses.

Class B IP address format is: 10NNNNNN.NNNNNNNN.HHHHHHHH.HHHHHHHH

Class C Address

The first octet of this class has its first 3 bits set to 110. Class C IP addresses range from 192.0.0.x to 223.255.255.x. The default subnet mask for Class C is 255.255.255.x. Class C gives 2097152 (221) Network addresses and 254 (28-2) Host addresses. 
Class C IP address format is: 110NNNNN.NNNNNNNN.NNNNNNNN.HHHHHHHH

Class D Address

The first four bits of the first octet in class D IP address are set to 1110. Class D has IP address rage from 224.0.0.0 to 239.255.255.255. Class D is reserved for Multicasting. In multicasting data is not intended for a particular host, but multiple ones. That is why there is no need to extract host address from the class D IP addresses. 
The Class D does not have any subnet mask.

Class E Address

The class E IP addresses are reserved for experimental purpose only for R&D or study. IP addresses in the class E ranges from 240.0.0.0 to 255.255.255.254. This class too is not equipped with any subnet mask.

Need of IP address:

An 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.

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.

In TCP/IP networks (eg. The Internet) routing of packets is done using the IP address. Basically in moving a packet from source to destination, a series to decisions need to be made so as the packet reaches where it was intended. These decisions are made seeing the IP address of destination. So to receive or send any packet in TCP/IP networks we need an IP address. Although there are alternate protocol stacks (other than TCP/IP) used, there domain is limited.

IP Version 4 and IP Version 6:

The two versions of IP addresses currently running are IP versions 4 (IPv4) and IP versions 6 (IPv6). There are many features with these two versions.

IP Version 6

The IPv6 is the most recent version of Internet Protocol. As the Internet is growing rapidly, there is a global shortage for IPv4. IPv6 was developed by the Internet Engineering Task Force (IETF). IPv6 is intended to replace the IPv4. IPv6 uses a 128-bit address and it allows 2128 i.e. approximately 3.4×1038 addresses. The actual number is slightly smaller as some ranges are reserved for special use or not used. The IPv6 addresses are represented by 8 groups of four hexadecimal digits with the groups being supported by colons. An example is given below:

Eg: 2001:0db8:0000:0042:0000:8a2e:0370:7334

The features of IPv6

The main features of the IPv6 are listed below.

1) IPv6 provides better end-to-end connectivity than IPv4.

2) Comparatively faster routing.

3) IPv6 offers ease of administration than IPv4.

4) More security for applications and networks.

5) It provides better Multicast and Anycast abilities.

6) Better mobility features than IPv4.

7) IPv6 follows the key design principles of IPv4 and so that the transition from IPv4 to IPv6 is smoother.

These are the key features of the IPv6 when compared to the IPv4. However, IPv6 has not become popular as IPv4.

IP Version 4

IP Version 4 (IPv4) was defined in 1981. It has not undergone much changes from that time. Unfortunately, there is a need of IP addresses more than IPv4 could supply.

IPv4 uses 32-bit IP address. So the maximum number of IP address is 232—or 4,294,967,296.

This is a little more than four billion IP addresses. An IPv4 address is typically formatted as four 8-bit fields. Each 8-bit field represents a byte of the IPv4 address. As we have seen earlier, each fields will be separated with dots. This method of representing the byte of an IPv4 address is referred to as the dotted-decimal format. The bytes of the IPv4 is further classified into two parts. The network part and the host part.

Network Part

This part specifies the unique number assigned to your network. It also identifies the class of network assigned. The network part takes two bytes of the IPv4 address.

Host Part

This is the part of the IPv4 address that you can assign to each host. It uniquely identifies this machine on your network. For all hosts on your network, the network part of the IP address will be the same and host part will be changing.

Unicast, broad cast, multicast IP Addresses:

The cast term here signifies some data(stream of packets) is being transmitted to the recipient(s) from client(s) side over the communication channel that help them to communicate.

Unicast:

This type of information transfer is useful when there is a participation of single sender and single recipient. So, in short you can term it as a one-to-one transmission. For example, a device having IP address 10.1.2.0 in a network wants to send the traffic stream(data packets) to the device with IP address 20.12.4.2 in the other network, then unicast comes into picture. This is the most common form of data transfer over the networks.

Broadcast:

Broadcasting transfer (one-to-all) techniques can be classified into two types :

Limited Broadcasting:

Suppose you have to send stream of packets to all the devices over the network that you reside, this broadcasting comes handy. For this to achieve,it will append 255.255.255.255 (all the 32 bits of IP address set to 1) called as Limited Broadcast Address in the destination address of the datagram (packet) header which is reserved for information tranfer to all the recipients from a single client (sender) over the network.

Direct Broadcasting:

This is useful when a device in one network wants to transfer packet stream to all the devices over the other network. This is achieved by translating all the Host ID part bits of the destination address to 1,referred as Direct Broadcast Address in the datagram header for information transfer.

This mode is mainly utilized by television networks for video and audio distribution.

One important protocol of this class in Computer Networks is Address Resolution Protocol (ARP) that is used for resolving IP address into physical address which is necessary for underlying communication.

Multicast:

In multicasting, one/more senders and one/more recipients participate in data transfer traffic. In this method traffic recline between the boundaries of unicast (one-to-one) and broadcast (one-to-all). Multicast lets server’s direct single copies of data streams that are then simulated and routed to hosts that request it. IP multicast requires support of some other protocols like IGMP (Internet Group Management Protocol), Multicast routing for its working. Also in Classful IP addressing Class D is reserved for multicast groups.

Subnet Mask:

A subnet mask is a number that defines a range of IP addresses available within a network. A single subnet mask limits the number of valid IPs for a specific network. Multiple subnet masks can organize a single network into smaller networks (called subnetworks or subnets). Systems within the same subnet can communicate directly with each other, while systems on different subnets must communicate through a router.

A subnet mask hides (or masks) the network part of a system's IP address and leaves only the host part as the machine identifier. It uses the same format as an IPv4 address — four sections of one to three numbers, separated by dots. Each section of the subnet mask can contain a number from 0 to 255, just like an IP address. For example, a typical subnet mask for a Class C IP address is:

255.255.255.0

In the example above, the first three sections are full (255 out of 255), meaning the IP addresses of devices within the subnet mask must be identical in the first three sections. The last section of each computer's IP address can be anything from 0 to 255. If the subnet mask is defined as 255.255.255.0, the IP addresses 10.0.1.99 and 10.0.1.100 are in the same subnet, but 10.0.2.100 is not.

A subnet mask of 255.255.255.0 allows for close to 256 unique hosts within the network (since not all 256 IP addresses can be used).