Transmission Control Protocol / Internet Protocol (TCP/IP) is a not just a model used to describe network functions, but a suite of protocols that define how various operations are carried out in the different layers of the TCP/IP model, as data flows through a network.
Let's check out some of these protocols below:
Bear in mind that these protocols also apply to the OSI model, but since the TCP/IP model is the most popular and commonly used, we could easily make reference to it as we explore these protocols briefly.
1. TELNET
Let's assume you want to configure a network device (say, a switch or router), and you happen to be far away, you obviously need a way to connect to this device so you can go ahead and configure it.
TELNET makes it possible for a user to establish a remote connection to a network device, usually for the purpose of configuring it.
The only problem with TELNET is that once the remote connection is established, everything is sent via plain text (no encryption), and could be visible to anyone tapping into that session with say, a sniffing tool.
You would want to use TELNET when security is not really an issue; for example, in a classroom setting or in a personal home network.
2. Secure Shell (SSH)
To solve the problem of TELNET (plain text transmission), Secure Shell (SSH) was developed.
SSH does the same thing as TELNET (establish remote connections with a device), but the difference is that SSH does this securely.
This means that upon using SSH to establish a remote connection, everything sent within that session is encrypted, making is safe from prying eyes.
We can confidently say that SSH is a secure form of TELNET.
3. File Transfer Protocol (FTP)
FTP is a protocol that is used by requesting devices to retrieve files from an FTP server.
File Transfer Protocol is reliable, meaning that there is a connection-oriented session established between the requesting device and the FTP server.
4. Trivial File Transfer Protocol (TFTP)
Just like FTP, Trivial File Transfer Protocol is also used to retrieve files from a TFTP server.
The major difference between FTP and TFTP is that TFTP is not reliable, meaning that there is NO connection-oriented session established between the requesting device and the TFTP server.
The only concern in a TFTP transmission is the need to get the files from the server down to the client; not mainly the connection between the two devices. This makes TFTP transmissions faster than FTP transmissions.
5. Simple Network Management Protocol (SNMP)
Simple Network Management Protocol is a protocol that helps to collect information about devices connected on a network. The kind of information collected by SNMP ranges from device temperature, logging messages, etc.
The information collected via SNMP are stored on an SNMP server, and an administrator can log in to the SNMP server to view this information.
SNMP goes a long way to keep track of what's happening in your network, and helps particularly in a large network where an administrator cannot possibly physically monitor all network devices.
6. HyperText Transfer Protocol (HTTP)
HTTP is a very popular protocol and it defines a standard for communication across webpages.
It dictates how operations are carried out in interacting with web pages, and websites as a whole.
7. Network Time Protocol (NTP)
You wouldn't agree more that keeping the correct time is important.
Most businesses run real-time applications, and the job of the Network Time Protocol is to make sure that the time across all connected network devices are synchronized.
Typically, an NTP server exists on a network, and all devices contact it to get the correct time at every point in time.
8. Domain Name Service (DNS)
Domain Name Service acts like a translator by translating the text you type in a web browser to the equivalent IP address needed to complete the connection.
Usually when you type in "www.netcue.blogspot.com", there is a DNS server that converts that web address to an IP address, so that you can receive the correct web page you requested for. Really cool protocol if you ask me...
9. Dynamic Host Configuration Protocol (DHCP)
The Dynamic Host Configuration Protocol is used to help us with a part of our IP addressing problems.
Imagine you had to manually configure say, 500 computers each with its own IP address information! Sounds stressful!
DHCP helps to avoid this stress by handing out IP addresses to computers that are in need of it.
This means that you have less work configuring IP addresses on computers, since only the very important devices would need to be configured statically, while others would get their IP address information from the DHCP server.
DHCP uses what we call a DORA process (Discover, Offer, Request, Acknowledgment).
The Discover and Request messages are sent by the requesting devices, while the Offer and Acknowledgement messages are sent by the DHCP server.
10. Transmission Control Protocol (TCP)
Transmission Control Protocol is the protocol that resides in the host-to-host layer of the TCP/IP model (Transport layer in the OSI model), and makes sure that data is transmitted reliably.
11. Unified Datagram Protocol (UDP)
UDP also resides in the host-to-host layer of the TCP/IP model, but differs from TCP in the sense that it works with unreliable transmission.
12. Internet Control Message Protocol (ICMP)
The Internet Control Message Protocol is used by communicating devices to tell each other if a destination is reachable or unreachable. Routers for example, would send ICMP packets to a requesting device (say, a computer) to inform it that the destination is unreachable.
13. Address Resolution Protocol (ARP)
The Address Resolution Protocol is used at the network access layer of the TCP/IP model (usually by switches) to request for the MAC address of a destination device.
Since the destination MAC addresses is needed in order to successfully complete a transmission, it has to be included in the frame.
When a switch has the destination IP address and not the destination MAC address, it uses ARP to request that the destination device sends its MAC address.
The Address Resolution Protocol is actually a broadcast message, and only the concerned device (in this case the destination device) will respond by sending its MAC address.
Once this is done, the transmission can be successfully done.
......and that is it! (at least for now).
Knowledge of TCP/IP in easy-to-grasp bullets.
When it is required of you to have an understanding of TCP/IP, what is really required is that you have good understanding of the protocols that reside in the TCP/IP model; as this would go a long way in helping you to successfully configure and troubleshoot networks.
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