Classification of Network Protocols

This article provides an overview of the classification of network protocols. It covers application layer protocols like DHCP, DNS, FTP, HTTP, IMAP, POP, SMTP, and Telnet, as well as presentation layer protocols, session layer protocols, transport layer protocols, network layer protocols, and data link layer protocols. The advantages and disadvantages of each protocol are discussed.

Classification of network protocols
Now that you know how the OSI model works, you can dive straight into the classification of protocols.
The following are some of the most prominent protocols used in network communication.
Application layer network protocols
1. DHCP: Dynamic Host Configuration Protocol
DHCP is a communication protocol that enables network administrators to automate the assignment of IP
addresses in a network. In an IP network, every device connecting to the internet requires a unique IP.
DHCP lets network admins distribute IP addresses from a central point and automatically send a new IP
address when a device is plugged in from a different place in the network. DHCP works on a client-server
model.
Advantages of using DHCP
 Centralized management of IP addresses.
 Seamless addition of new clients into a network.
 Reuse of IP addresses, reducing the total number of IP addresses required.
Disadvantages of using DHCP
 Tracking internet activity becomes tedious, as the same device can have multiple IP addresses
over a period of time.
 Computers with DHCP cannot be used as servers, as their IPs change over time.
2. DNS: Domain Name System protocol
The DNS protocol helps in translating or mapping host names to IP addresses. DNS works on a client-
server model, and uses a distributed database over a hierarchy of name servers.
Hosts are identified based on their IP addresses, but memorizing an IP address is difficult due to its
complexity. IPs are also dynamic, making it all the more necessary to map domain names to IP addresses.
DNS helps resolve this issue by converting the domain names of websites into numerical IP addresses.
Advantages
 DNS facilitates internet access.
 Eliminates the need to memorize IP addresses.
Disadvantages
 DNS queries don't carry information pertaining to the client who initiated it. This is because the
DNS server only sees the IP from where the query came from, making the server susceptible to
manipulation from hackers.
 DNS root servers, if compromised, could enable hackers to redirect to other pages for phishing
data.
3. FTP: File Transfer Protocol
File Transfer Protocol enables file sharing between hosts, both local and remote, and runs on top of TCP.
For file transfer, FTP creates two TCP connections: control and data connection. The control connection is
used to transfer control information like passwords, commands to retrieve and store files, etc., and the data

connection is used to transfer the actual file. Both of these connections run in parallel during the entire file
transfer process.
Advantages
 Enables sharing large files and multiple directories at the same time.
 Lets you resume file sharing if it was interrupted.
 Lets you recover lost data, and schedule a file transfer.
Disadvantages
 FTP lacks security. Data, usernames, and passwords are transferred in plain text, making them
vulnerable to malicious actors.
 FTP lacks encryption capabilities, making it non-compliant with industry standards.
4. HTTP: Hyper Text Transfer Protocol
HTTP is an application layer protocol used for distributed, collaborative, and hypermedia information
systems. It works on a client-server model, where the web browser acts as the client. Data such as text,
images, and other multimedia files are shared over the World Wide Web using HTTP. As a request and
response type protocol, the client sends a request to the server, which is then processed by the server before
sending a response back to the client.
HTTP is a stateless protocol, meaning the client and server are only aware of each other while the
connection between them is intact. After that, both the client and server forget about each other's existence.
Due to this phenomenon, the client and server can't both retain information between requests.
Advantages
 Memory usage and CPU usage are low because of lesser concurrent connections.
 Errors can be reported without closing connections.
 Owing to lesser TCP connections, network congestion is reduced.
Disadvantages
 HTTP lacks encryption capabilities, making it less secure.
 HTTP requires more power to establish communication and transfer data.
5. IMAP and IMAP4: Internet Message Access Protocol (version 4)
IMAP is an email protocol that lets end users access and manipulate messages stored on a mail server from
their email client as if they were present locally on their remote device. IMAP follows a client-server
model, and lets multiple clients access messages on a common mail server concurrently. IMAP includes
operations for creating, deleting, and renaming mailboxes; checking for new messages; permanently
removing messages; setting and removing flags; and much more. The current version of IMAP is version 4
revision 1.
Advantages
 As the emails are stored on the mail server, local storage utilization is minimal.
 In case of accidental deletion of emails or data, it is always possible to retrieve them as they are
stored on the mail server.
Disadvantages
 Emails won't work without an active internet connection.
 High utilization of emails by end users requires more mailbox storage, thereby augmenting costs.
6. POP and POP3: Post Office Protocol (version 3)
The Post Office Protocol is also an email protocol. Using this protocol, the end user can download emails
from the mail server to their own email client. Once the emails are downloaded locally, they can be read

without an internet connection. Also, once the emails are moved locally, they get deleted from the mail
server, freeing up space. POP3 is not designed to perform extensive manipulations with the messages on
the mail server, unlike IMAP4. POP3 is the latest version of the Post Office Protocol.
Advantages
 Read emails on local devices without internet connection.
 The mail server need not have high storage capacity, as the emails get deleted when they're moved
locally.
Disadvantages
 If the local device on which the emails were downloaded crashes or gets stolen, the emails are
lost.
7. SMTP: Simple Mail Transfer Protocol
SMTP is a protocol designed to transfer electronic mail reliably and efficiently. SMTP is a push protocol
and is used to send the email, whereas POP and IMAP are used to retrieve emails on the end user's side.
SMTP transfers emails between systems, and notifies on incoming emails. Using SMTP, a client can
transfer an email to another client on the same network or another network through a relay or gateway
access available to both networks.
Advantages
 Ease of installation.
 Connects to any system without any restriction.
 It doesn't need any development from your side.
Disadvantages
 Back and forth conversations between servers can delay sending a message, and also increases the
chance of the message not being delivered.
 Certain firewalls can block the ports used with SMTP.
8. Telnet: Terminal emulation protocol
Telnet is an application layer protocol that enables a user to communicate with a remote device. A Telnet
client is installed on the user's machine, which accesses the command line interface of another remote
machine that runs a Telnet server program.
Telnet is mostly used by network administrators to access and manage remote devices. To access a remote
device, a network admin needs to enter the IP or host name of the remote device, after which they will be
presented with a virtual terminal that can interact with the host.
Advantages
 Compatible with multiple operating systems.
 Saves a lot of time due to its swift connectivity with remote devices.
Disadvantages
 Telnet lacks encryption capabilities and sends across critical information in clear text, making it
easier for malicious actors.
 Expensive due to slow typing speeds.
9. SNMP: Simple Network Management Protocol
SNMP is an application layer protocol used to manage nodes, like servers, workstations, routers, switches,
etc., on an IP network. SNMP enables network admins to monitor network performance, identify network
glitches, and troubleshoot them. SNMP protocol is comprised of three components: a managed device, an
SNMP agent, and an SNMP manager.

The SNMP agent resides on the managed device. The agent is a software module that has local knowledge
of management information, and translates that information into a form compatible with the SNMP
manager. The SNMP manager presents the data obtained from the SNMP agent, helping network admins
manage nodes effectively.
Currently, there are three versions of SNMP: SNMP v1, SNMP v2, and SNMP v3. Both versions 1 and 2
have many features in common, but SNMP v2 offers enhancements such as additional protocol operations.
SNMP version 3 (SNMP v3) adds security and remote configuration capabilities to the previous versions.
Presentation layer network protocols
LPP: Lightweight Presentation Protocol
The Lightweight Presentation Protocol helps provide streamlined support for OSI application services in
networks running on TCP/IP protocols for some constrained environments. LPP is designed for a particular
class of OSI applications, namely those entities whose application context contains only an Association
Control Service Element (ACSE) and a Remote Operations Service Element (ROSE). LPP is not
applicable to entities whose application context is more extensive, i.e., contains a Reliable Transfer Service
Element.
Session layer network protocols
RPC: Remote Procedure Call protocol
RPC is a protocol for requesting a service from a program in a remote computer through a network, and
can be used without having to understand the underlying network technologies. RPC uses TCP or UDP for
carrying the messages between communicating programs. RPC also works on client-server model. The
requesting program is the client, and the service providing program is the server.
Advantages
 RPC omits many protocol layers to improve performance.
 With RPC, code rewriting or redeveloping efforts are minimized.
Disadvantages
 Not yet proven to work effectively over wide-area networks.
 Apart from TCP/IP, RPC does not support other transport protocols.
Transport layer network protocols
1. TCP: Transmission Control Protocol
TCP is a transport layer protocol that provides a reliable stream delivery and virtual connection service to
applications through the use of sequenced acknowledgement. TCP is a connection-oriented protocol, as it
requires a connection to be established between applications before data transfer. Through flow control and
acknowledgement of data, TCP provides extensive error checking. TCP ensures sequencing of data,
meaning the data packets arrive in order at the receiving end. Retransmission of lost data packets is also
feasible with TCP.
Advantages

 TCP ensures three things: data reaches the destination, reaches it on time, and reaches it without
duplication.
 TCP automatically breaks data into packets before transmission.
Disadvantages
 TCP cannot be used for broadcast and multicast connections.
2. UDP: User Datagram Protocol
UDP is a connection-less transport layer protocol that provides a simple but unreliable message service.
Unlike TCP, UDP adds no reliability, flow control, or error recovery functions. UDP is useful in situations
where the reliability mechanisms of TCP are not necessary. Retransmission of lost data packets isn't
possible with UDP.
Advantages
 Broadcast and multicast connections are possible with UDP.
 UDP is faster than TCP.
Disadvantages
 In UDP, it's possible that a packet may not be delivered, be delivered twice, or not be delivered at
all.
 Manual disintegration of data packets is needed.
Network layer protocols
1. IP: Internet Protocol (IPv4)
IPv4 is a network layer protocol that contains addressing and control information, which helps packets be
routed in a network. IP works in tandem with TCP to deliver data packets across the network. Under IP,
each host is assigned a 32-bit address comprised of two major parts: the network number and host number.
The network number identifies a network and is assigned by the internet, while the host number identifies
a host on the network and is assigned by a network admin. The IP is only responsible for delivering the
packets, and TCP helps puts them back in the right order.
Advantages
 IPv4 encrypts data to ensure privacy and security.
 With IP, routing data becomes more scalable and economical.
Disadvantages
 IPv4 is labor intensive, complex, and prone to errors.
2. IPv6: Internet Protocol version 6
IPv6 is the latest version of the Internet Protocol, a network layer protocol that possesses addressing and
control information for enabling packets to be routed in the network. IPv6 was created to deal with IPv4
exhaustion. It increases the IP address size from 32 bits to 128 bits to support more levels of addressing.
Advantages
 More efficient routing and packet processing compared to IPv4.
 Better security compared to IPv4.
Disadvantages
 IPv6 is not compatible with machines that run on IPv4.
 Challenge in upgrading the devices to IPv6.

3. ICMP: Internet Control Message Protocol
ICMP is a network layer supporting protocol used by network devices to send error messages and
operational information. ICMP messages delivered in IP packets are used for out-of-band messages related
to network operation or misoperation. ICMP is used to announce network errors, congestion, and timeouts,
as well assist in troubleshooting.
Advantages
 ICMP is used to diagnose network issues.
Disadvantages
 Sending a lot of ICMP messages increases network traffic.
 End users are affected if malicious users send many ICMP destination unreachable packets.
Data link layer network protocols
1. ARP: Address Resolution Protocol
The Address Resolution Protocol helps map IP addresses to physical machine addresses (or a MAC
address for Ethernet) recognized in the local network. A table called an ARP cache is used to maintain a
correlation between each IP address and its corresponding MAC address. ARP offers the rules to make
these correlations, and helps convert addresses in both directions.
Advantages
 MAC addresses need not be known or memorized, as the ARP cache contains all the MAC
addresses and maps them automatically with IPs.
Disadvantages
 ARP is susceptible to security attacks called ARP spoofing attacks.
 When using ARP, sometimes a hacker might be able to stop the traffic altogether. This is also
known as ARP denial-of-services.
2. SLIP: Serial Line IP
SLIP is used for point-to-point serial connections using TCP/IP. SLIP is used on dedicated serial links, and
sometimes for dial-up purposes. SLIP is useful for allowing mixes of hosts and routers to communicate
with one another; for example, host-host, host-router, and router-router are all common SLIP network
configurations. SLIP is merely a packet framing protocol: It defines a sequence of characters that frame IP
packets on a serial line. It does not provide addressing, packet type identification, error detection or
correction, or compression mechanisms.
Advantages
 Since it has a small overhead, it is suitable for usage in microcontrollers.
 It reuses existing dial-up connections and telephone lines.
 It's easy to deploy since it's based on the Internet Protocol.
DIsadvantages
 SLIP doesn't support automatic setup of network connections in multiple OSI layers at the same
time.
 SLIP does not support synchronous connections, such as a connection created through the internet
from a modem to an internet service provider (ISP).