Network Protocols and Standards

• Protocols define how data is sent, received, and processed.
• Standards ensure that various technologies are compatible with each other.
• Network protocols are a set of rules and conventions.
• Protocols are a set of rules governing communications between computers on a network.

Network protocols

• Outlines how connected devices communicate across a network to exchange information easily and safely.
• Serves as a common language for devices to enable communication irrespective of differences in software, hardware, or internal processes.
• Defines the precise format of all data that is exchanged in a network.
• Internet Protocol (IP) defines the format of IP addresses.
• IP addresses are four eight-bit numbers called octets.
• Octet decimal values range from 0 to 255, as in 10.0.101.155.

Network standards

• Detailed definitions of protocols established by standards organizations.
• Vendors follow these standards when creating products.
• Networking standards are documents that have developed to provide technical requirements, specifications, and guidelines.
• Technical requirements, specifications, and guidelines must be employed consistently to ensure devices, equipment, and software which govern networking are fit for their intended purpose.
• Standards make it possible to use products from different vendors.

OSI Reference Model

• Network standards are organized into a framework called the Open Systems Interconnection (OSI) Reference Model.
• Establishes a hierarchy for protocols.
• Each protocol can deal with just one part of the overall task of data communications.
• Created in 1984 by ISO.
• Is a reference framework that explains the process of transmitting data between computers.
• Sender to receiver data exchange is done through a number of layers

Seven Layers of OSI Model

• Layer 7: Application Layer.
• Layer 6: Presentation Layer.
• Layer 5: Session Layer.
• Layer 4: Transport Layer.
• Layer 3: Network Layer.
• Layer 2: Data Link Layer.
• Layer 1: Physical Layer.
• The Application, Presentation and Session Layers are the Software Layers
• The Network, Data link and Physical Layers are the Hardware layers
• The Transport Layer is the Heart of OSI

Physical layer

• First and lowest layer of the OSI communications model.
• Its function is to transport data using electrical, mechanical or procedural interfaces like cables, connectors, and network interfaces.
• Responsible for sending computer bits from one device to another along the network.
• Determines how physical connections to the network are set up.
• Determines how bits are represented into predictable signals; as they are transmitted either electrically, optically or by radio waves.

Data link layer

• Describes the basic techniques that networks use to uniquely identify devices on the network (typically via a MAC address).
• Describes the means for one device to send information over the physical layer to another device, in the form of data packets.
• Switches operate at the data link layer, which manage the efficient transmission of data packets.
• The Data link layer is the protocol layer in a program that handles how data moves in and out of a physical link in a network.
• The Data link layer is the second layer from the bottom in the OSI network architecture model.
• Provides physical transmission of the data.
• Ensures that messages are delivered to the proper device on a LAN using hardware addresses.
• MAC (Media Access Control) address is a basic fundamental addressing on networks, enabling traffic to be sent from one device to another.
• Translates messages from the Network layer into bits for the Physical layer.
• The "switching" layer

Network Layer

• Responsible for packet forwarding including routing through intermediate routers.
• Routers operate at the network layer.

Transport layer

• Responsible for ensuring that data packets arrive accurately and reliably between sender and receiver.
• Most often uses TCP or UDP as the data transport protocol.

Session layer

• Establishes sessions between network applications.
• Manages connections between client and server.

Presentation layer

• Ensures that data transferred from one system's Application layer can be read by the Application layer on another one.
• Acts as the translator and formatter.
• Example: English Characters, Chinese Characters, etc.
• Application encryption.

Application Layer

• Layer that ensures effective communication with another application program on a network.
• An abstraction layer that specifies the shared communication protocols and interface methods used by hosts in a communications network.

Twisted-pair cable

• The most common type of cable.
• Inside the outer sheath of the cable are four pairs of small insulated wires twisted together.

RJ45 Connectors

• Twisted-pair cable is attached to network to devices using special connectors called RJ45.
• RJ45 are small block of plastic with eight metal contacts.
• RJ45 connectors resemble a telephone connector but are larger; telephone connectors have four electrical contacts.

Patch panels and patch cables.

• Patch panels are used to bring cables run from individual computer locations to a single location where they can then be patched to other equipment using patch cables.
• A patch cable is simply a short length of twisted-pair cable with an RJ45 plug on both ends.

Repeaters

• A layer-1 device designed to circumvent the maximum length limitation of twisted-pair network cables.
• Repeater contains two RJ45 ports, which are connected internally by an amplifier
• An electronic device that receives a signal and retransmits it.
• Used to extend transmissions so that the signal can cover longer

Hub

• A repeater with more than two ports.
• May have four or eight ports
• An older technology that interconnects network components.
• Does not make forwarding decisions.
• Receives bits in on one port then retransmits those bits out all other ports

Switch

• Layer-2 device that is like a hub.
• It allows you to connect more than one device.
• A switch can examine the actual contents of the data that it receives.
• Data is sent in units called packets that contain a destination address.
• Looks at the destination address in the packets and repeats the incoming packet on the port that can deliver the packet to the intended destination.