A Network is basically connecting two or more devices though a wired or wireless channel to share & exchange the information electronically. These devices can be computers, scanners, printers, routers, storage systems and applications etc. Based on the type of devices used in the network, they are referred as Compute Network, mobile network and a Storage Network etc. The devices in any kind of network are expected to share the information from the other resources in the network in a secure and reliable way. The devices in a network are connected through cables, telephone lines, radio waves and infra light beams etc.

Previously we learned the fundamentals of Storage Infrastructure and and its key concepts. In this post, we will explore the types of  networks and its features which are used in traditional and cloud datacenters.

  1. Network Considerations and Advantages
  2. Different Types of Networks
  3. Network Protocol (Open Systems Interconnection OSI Model)
  4. Types of Network Devices and Network Ports
  5. Commonly used Network ports in Cloud Computing
  6. Types of network Service Protocols
  7. Network Configurations and Operational Techniques
  8. Network Optimization Techniques
  9. Troubleshooting Basic Network Connectivity Issues

 

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Network Protocol Overview

What is a Network Protocol ?

A network protocol is a set of rules that governs the communications between the devices on a single or multiple networks. In order for two devices to talk to each other, they must be speaking the same language. Many different types of network protocols and standards are defined over the years to ensure the devices can communicate with each other whether they are located in the same room or in another country.

What is Open Systems Interconnection (OSI) Model ?

The OSI (Open Systems Interconnection) reference Model is the popular and widely followed model by many private and public organizations. The OSI model is one of the key fundamentals of networking. It defines seven layers of networking protocols which specifies the aspects of a network’s operation that can be addressed by various network standards. The 7 layers of Open Systems Interconnection model are

  • 7 Application Layer (HTTP, FTP, SMTP, DNS, Telnet)
  • 6 Presentation Layer
  • 5 Session Layer
  • 4 Transport Layer (TCP, SPX)
  • 3 Network Layer (IP, IPX)
  • 2 Data Link or Ethernet Layer
  • 1 Physical Layer

*Note that the numbering is from bottom to top

OSI Reference Model
OSI Reference Model

The first three layers defines protocols on how information is sent from one device to another over a network. Layers 4 to 7 defines protocols on how applications relate to the network through application programming interfaces. Lets look at  each layer at the high level.

Layer 1: The Physical Layer

  • Physical Layer is the first layer and it is at the bottom of the OSI model. This layer defines the physical characteristics of the network such as cables and network devices which form the physical network.
  • It defines the types of cables & connectors and the length of the cables that can be used to form a network.
  • It also specifies the electrical characteristics of the signals that are used to transmit data over network cables from one device to another device in a network.
  • Ethernet cables, switches and NICs are the good examples of physical layer.
  • The job of these physical components is to just transfer the signals through them but they don’t examine the contents of the signals that they regenerate. This is done at the Data Link Layer, not at the Physical Layer.

 

Layer 2: The Data Link Layer

  • The Data Link Layer is the 2nd layer of the OSI model and it addresses the way that data packets are sent from one network device to another.
  • Data-link layer protocols address things, such as the size of each packet of data to be sent, a means of addressing each packet so that it’s delivered to the correct recipient. It also ensure that two or more devices in the network don’t try to transmit data on the network at the same time.
  • This Layer also provides basic error detection and correction techniques to ensure that the data sent is the same as the data received. If an error occurs, the data-link standard specifies how the node is to be informed of the error so it can re-transmit the data.
  • At this layer, every device on the network has an address known as the MAC address (Media Access Control). This is the actual unique hardware address, assigned to the device from the device manufacturer


Layer 3: The Network Layer

  • The Network Layer handles the task of routing network messages from one device to another in the network.
  • The two most popular Layer-3 protocols are IP which is usually paired with TCP and generally referred as TCP/IP protocol. Anther popular protocols such as IPX or SPX are used for Novell and Windows networks.
  • One important function of the Network Layer is logical addressing such as IP addressing. Every network device has a unique physical address called a MAC address and it cannot be changed.  Where as a logical address is assigned to the network device so that it can be accessed on the network using the logical address that is assigned.
  • Logical addresses such as IP addresses are created and used by Network Layer protocols, such as IP or IPX. The Network Layer protocol translates logical addresses to MAC addresses because the IP protocol must use a Data Link Layer protocol to actually send packets to devices.
  • Physical and Data layer works closely together in order translate the IP address of a device into the correct MAC address for the device so that it can send the data to correct destination.
  • Another important function of the Network layer is routing, which is to find an appropriate path through the network where hundreds or thousands of devices are connected in a multiple networks. Routing is needed for a computer on one network needs to send a packet to a computer on another network.
  • Router is one of the common network device which forwards the packet to the destination network. Routers can be used to connect networks that use different protocols. For example, router can connect a LAN network to a WAN network that runs on a different level of protocols.

 

Layer 4: The Transport Layer

  • The Transport Layer is the 4th layer of OSI model at which one network device communicates with another network device or a computer. TCP protocol is the example of the Transport layer.
  • The main purpose of this layer is to ensure that packets that are transmitted over the network are sent reliably and without errors.
  • The Transport Layer establish connections between network devices, acknowledging the receipt of packets, and resending packets that are not received.
  • Transport Layer protocol also divides large messages into smaller packets that can be sent over the network efficiently. It also reassembles the message on the receiving end to ensure that all packets contained in a single transmission are received and there is no loss of data.

 

Layer 5: The Session Layer

  • The Session Layer establishes sessions between the network devices for data exchange.
  • A session must be established between the devices in a network before data can be transmitted.
  • It makes sure that these sessions are properly established and maintained.

 

Layer 6: The Presentation Layer

  • The Presentation Layer converts the data sent over the network from one type of representation to another.
  • This layer can apply techniques like compression & encryption before the data is sent over the network. At the other end of the transmission, it then uncompresses and decrypts the data.

 

Layer 7: The Application Layer

  • The 7th layer and the top most layer of the OSI model is the Application Layer which deals with the techniques that application programs use to communicate with the network.
  • It represents the level at which application programs interact with the network, using programming interfaces (APIs) to request network services.
  • One of the most commonly used application layer protocols are HTTP and HTTPS, which is the basis of the World Wide Web or internet.

See: What are Storage Area Network (SAN) Protocols

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Cloud Solutions Architect with more than 10 years of experience in designing & deploying application in multiple cloud platforms. Owner of Mycloudwiki.com and tsmtutorials.com tech blogs. Email me if you are interested in writing tech articles.

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