What are Network Communications Protocols?
- 0.1 What are Network Communications Protocols?
- 0.2 Network Protocols
- 0.3 The TCP/IP Protocol Suite
- 0.4 Web and Web Service
- 0.5 Transport layer
- 0.6 Internet Layer
- 0.7 Routing Protocols
- 0.8 Network Access Layer
- 0.9 Message Formatting and Encapsulation
- 0.10 Message Size
- 0.11 Message Timing
- 1 Unicast, Multicast, and Broadcast
- 2 The Benefits of Using a Layered Model
- 3 The OSI Reference Model
- 4 Typical Sessions
- 5 Tracing the Path
For example, consider two people communicating face-to-face. Prior to communicating, they must agree on how to communicate. If the communication is using voice, they must first agree on the language. Next, when they have a message to share, they must be able to format that message in a way that is understandable. For example, if someone uses the English language, but has poor sentence structure, the message can easily be misunderstood.
Similarly, network protocols specify many features of network communication, as shown in the figure.
Note: IP in this course refers to both the IPv4 and IPv6 protocols. IPv6 is the most recent version of IP and will eventually replace the more common IPv4.
The TCP/IP Protocol Suite
- DNS – Domain Name System. Translates domain names such as cisco.com, into IP addresses.
- DHCPv4 – Dynamic Host Configuration Protocol for IPv4. A DHCPv4 server dynamically assigns IPv4 addressing information to DHCPv4 clients at start-up and allows the addresses to be re-used when no longer needed.
- DHCPv6 – Dynamic Host Configuration Protocol for IPv6. DHCPv6 is similar to DHCPv4. A DHCPv6 server dynamically assigns IPv6 addressing information to DHCPv6 clients at start-up.
- SLAAC – Stateless Address Autoconfiguration. A method that allows a device to obtain its IPv6 addressing information without using a DHCPv6 server.
- SMTP – Simple Mail Transfer Protocol. Enables clients to send email to a mail server and enables servers to send email to other servers.
- POP3 – Post Office Protocol version 3. Enables clients to retrieve email from a mail server and download the email to the client’s local mail application.
- IMAP – Internet Message Access Protocol. Enables clients to access email stored on a mail server as well as maintaining email on the server.
- FTP – File Transfer Protocol. Sets the rules that enable a user on one host to access and transfer files to and from another host over a network. FTP is a reliable, connection-oriented, and acknowledged file delivery protocol.
- SFTP – SSH File Transfer Protocol. As an extension to Secure Shell (SSH) protocol, SFTP can be used to establish a secure file transfer session in which the file transfer is encrypted. SSH is a method for secure remote login that is typically used for accessing the command line of a device.
- TFTP – Trivial File Transfer Protocol. A simple, connectionless file transfer protocol with best-effort, unacknowledged file delivery. It uses less overhead than FTP.
Web and Web Service
- HTTP – Hypertext Transfer Protocol. A set of rules for exchanging text, graphic images, sound, video, and other multimedia files on the World Wide Web.
- HTTPS – HTTP Secure. A secure form of HTTP that encrypts the data that is exchanged over the World Wide Web.
- REST – Representational State Transfer. A web service that uses application programming interfaces (APIs) and HTTP requests to create web applications.
Message Formatting and Encapsulation
A common example of requiring the correct format in human communications is when sending a letter. Click Play in the figure to view an animation of formatting and encapsulating a letter.
An envelope has the address of the sender and receiver, each located at the proper place on the envelope. If the destination address and formatting are not correct, the letter is not delivered.
The process of placing one message format (the letter) inside another message format (the envelope) is called encapsulation. De-encapsulation occurs when the process is reversed by the recipient and the letter is removed from the envelope.
The animation shows an envelope with a stamp, a sender of 4085 SE Pine Street, Ocala, Florida 34471 and a recipient at 1400 Main Street, Canton, Ohio 44203. The envelope opens and shows a letter: dear Jane, I just returned from my trip. I thought you might like to see my pictures. John. A breakout table appears with the following headings: Recipient (destination) location address, sender (source) location address, salutation (start of message indicator), recipient (destination) identifier, the content of letter (encapsulated data) sender (source) identifier, end of frame (end of message indicator).
The next row has an envelope addressing under the first 2 sections, then encapsulated letter under the next 4 sections. The 1400 Main Street Canton, Ohio 44203 goes in a new row under the recipient (destination) and envelope addressing sections. The 4085 SE Pine Street Ocala, Florida 34471 goes under the sender (source) and envelope addressing sections.
The dear goes under the salutation (start of message indicator) and encapsulated letter sections. Jane goes under the recipient (destination) identifier and encapsulated letter sections. The words I just returned from my trip. I thought you might like to see my pictures. Goes under the content of the letter (encapsulated data) and encapsulated letter sections. The word John goes under the sender (source) identifier and encapsulated letter sections. The stamp on the letter goes under the end of the frame (end of message indicator) section.
Click Play in the figure to view an animation of message size in face-to-face communications.
When people communicate with each other, the messages that they send are usually broken into smaller parts or sentences. These sentences are limited in size to what the receiving person can process at one time, as shown in the figure. It also makes it easier for the receiver to read and comprehend.
Message timing is also very important in network communications. Message timing includes the following:
- Flow Control – This is the process of managing the rate of data transmission. Flow control defines how much information can be sent and the speed at which it can be delivered. For example, if one person speaks too quickly, it may be difficult for the receiver to hear and understand the message. In network communication, there are network protocols used by the source and destination devices to negotiate and manage the flow of information.
- Response Timeout – If a person asks a question and does not hear a response within an acceptable amount of time, the person assumes that no answer is coming and reacts accordingly. The person may repeat the question or instead, may go on with the conversation. Hosts on the network use network protocols that specify how long to wait for responses and what action to take if a response timeout occurs.
- Access method – This determines when someone can send a message. Click Play in the figure to see an animation of two people talking at the same time, then a “collision of information” occurs, and it is necessary for the two to back off and start again. Likewise, when a device wants to transmit on a wireless LAN, it is necessary for the WLAN network interface card (NIC) to determine whether the wireless medium is available.
Unicast, Multicast, and Broadcast
Hosts on a network use similar delivery options to communicate. These methods of communication are called unicast, multicast, and broadcast.
The Benefits of Using a Layered Model
Complex concepts such as how a network operates can be difficult to explain and understand. For this reason, a layered model is used to modularize the operations of a network into manageable layers.
These are the benefits of using a layered model to describe network protocols and operations:
- Assisting in protocol design because protocols that operate at a specific layer have defined information that they act upon and a defined interface to the layers above and below
- Fostering competition because products from different vendors can work together
- Preventing technology or capability changes in one layer from affecting other layers above and below
- Providing a common language to describe networking functions and capabilities
As shown in the figure, there are two-layered models that are used to describe network operations:
- Open System Interconnection (OSI) Reference Model
- TCP/IP Reference Model
The OSI Reference Model
It also describes the interaction of each layer with the layers directly above and below.
|OSI Model Layer||Description|
|7 – Application||The application layer contains protocols used for process-to-process communications.|
|6 – Presentation||The presentation layer provides for common representation of the data transferred between application layer services.|
|5 – Session||The session layer provides services to the presentation layer to organize its dialogue and to manage data exchange.|
|4 – Transport||The transport layer defines services to segment, transfer, and reassemble the data for individual communications between the end devices.|
|3 – Network||The network layer provides services to exchange the individual pieces of data over the network between identified end devices.|
|2 – Data Link||The data link layer protocols describe methods for exchanging data frames between devices over a common media|
|1 – Physical||The physical layer protocols describe the mechanical, electrical, functional, and procedural means to activate, maintain, and de-activate physical connections for a bit transmission to and from a network device.|
The TCP/IP Protocol Model
|TCP/IP Model Layer||Description|
|4 – Application||Represents data to the user, plus encoding and dialog control.|
|3 – Transport||Supports communication between various devices across diverse networks.|
|2 – Internet||Determines the best path through the network.|
|1 – Network Access||Controls the hardware devices and media that make up the network.|
Facts About Network Communication Process
Networks of Many Sizes
First and foremost, networks come in all sizes. They range from simple networks that consist of two computers to networks connecting millions of devices. Simple home networks let you share resources, such as printers, documents, pictures, and music, among a few local end devices. In this article, I want to discuss some facts about a network communication process.
Small office and home office (SOHO) networks allow people to work from home or a remote office. Many self-employed workers use these types of networks to advertise and sell products, order supplies and communicate with customers.
Businesses and large organizations use networks to provide consolidation, storage, and access to information on network servers. Networks provide email, instant messaging, and collaboration among employees. Many organizations use their network’s connection to the internet to provide products and services to customers.
The internet is the largest network in existence. In fact, the term internet means a “network of networks”. It is a collection of interconnected private and public networks.
In small businesses and homes, many computers function as both servers and clients on the network. This type of network is called a peer-to-peer network.
Small Home Networks
Small home networks connect a few computers to each other and to the internet.
Client computers have software installed, such as web browsers, email clients, and file transfers applications. This software enables them to request and display the information obtained from the server. A single computer can also run multiple types of client software. For example, a user can check email and view a web page while listening to the internet radio.
- File Server – The file server stores corporate and user files in a central location.
- Web Server – The web server runs web server software that allows many computers to access web pages.
- Email Server – The email server runs email server software that enables emails to be sent and received.
All of these transitions and connections happen in a fraction of a second, and Terry has started on her path to learning about her subject.
Michelle loves computer games. She has a powerful gaming console that she uses to play games against other players, watch movies, and play music. Michelle connects her game console directly to her network with a copper network cable.
Michelle’s network, like many home networks, connects to an ISP using a router and a cable modem. These devices allow Michelle’s home network to connect to a cable TV network that belongs to Michelle’s ISP. The cable wires for Michelle’s neighbourhood all connect to a central point on a telephone pole and then connect to a fibre-optic network. This fibre-optic network connects many neighbourhoods that are served by Michelle’s ISP.
All those fibre-optic cables connect to telecommunications services that provide access to high-capacity connections. These connections allow thousands of users in homes, government offices, and businesses to connect to internet destinations around the world.
Michelle has connected her game console to a company that hosts a very popular online game. Michelle is registered with the company, and its servers keep track of Michelle’s scores, experiences, and game assets. Michelle’s actions in her game become data that is sent to the gamer network. Michelle’s moves are broken up into groups of binary data that each consists of a string of zeros and ones. Information that identifies Michelle, the game she is playing, and Michelle’s network location are added to the game data. The pieces of data that represent Michelle’s gameplay are sent at high speed to the game provider’s network. The results are returned to Michelle in the form of graphics and sounds.
All of this happens so quickly that Michelle can compete with hundreds of other gamers in real-time.
Dr Ismael Awad is an oncologist who performs surgery on cancer patients. He frequently needs to consult with radiologists and other specialists on patient cases. The hospital that Dr Awad works for subscribes to a special service called a cloud. The cloud allows medical data, including patient x-rays and MRIs to be stored in a central location that is accessed over the internet. In this way, the hospital does not need to manage paper patient records and X-ray films.
When a patient has an X-ray taken, the image is digitized as computer data. The X-ray is then prepared by hospital computers to be sent to the medical cloud service. Because security is very important when working with medical data, the hospital uses network services that encrypt the image data and patient information. This encrypted data cannot be intercepted and read as it travels across the internet to the cloud service provider’s data centres. The data is addressed so that it can be routed to the cloud provider’s data centre to reach the correct services that provide storage and retrieval of high-resolution digital images.
Tracing the Path
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