CENG304 COMPUTER NETWORKS Asst. Prof. Mustafa YENIAD myeniad@ybu.edu.tr
Networking Devices Networking Protocol
OSI Reference Model Introducting to TCP/IP Protocol Suite
Networking Devices Networking devices are products used to connect networks. As computer networks grow in size and complexity, so do the networking devices used to connect them. • Allow a greater number of nodes to be connected to the network. • Extend the distance over which a network can extend. • Localize traffic on the network. • Can merge existing networks. • Isolate network problems so that they can be diagnosed more easily
Networking Devices NIC A network interface controller (NIC, also known as a network interface card, network adapter, LAN adapter or physical network interface, and by similar terms) is a computer hardware component that connects a computer to a computer network.
Networking Devices HUB Hub is a component of a network, a high- degree node. It refers to a node that has significantly bigger number of links in comparison with other nodes in the network. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.
Networking Devices HUB
Networking Devices SWITCH A network switch is a computer networking device that connects devices together on a computer network, by using packet switching to receive, process and forward data to the destination device. Unlike less advanced network hubs, a network switch forwards data only to one or multiple devices that need to receive it, rather than broadcasting the same data out of each of its ports.
Networking Devices SWITCH
Networking Devices ROUTER A router is a networking device that forwards data packets between computer networks. Routers perform the "traffic directing" functions on the Internet. When a data packet comes in on one of the lines, the router reads the address information in the packet to determine its ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey.
Networking Devices ROUTER
Networking Devices REPEATER A repeater is an electronic device that receives a signal and retransmits it at a higher level or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances. It is a generic term that refers to several different types of devices; a telephone repeater is an amplifier in a telephone line, an optical repeater is an optoelectronic circuit that amplifies the light beam in a optical fiber cable; and a radio repeater is a radio receiver and transmitter that retransmits a radio signal.
Networking Devices REPEATER
Networking Devices MODEM A modem (modulator-demodulator) is a network hardware device that modulates one or more carrier wave signals to encode digital information for transmission and demodulates signals to decode the transmitted information. Modems can be used with any means of transmitting analog signals, from light emitting diodes to radio. A common type of modem is one that turns the digital data of a computer into modulated electrical signal for transmission over telephone lines and demodulated by another modem at the receiver side to recover the digital data.
Networking Devices MODEM
Networking Devices BRIDGE A network bridge is networking hardware that connects multiple network segments. In the OSI model, bridging is performed in the first two layers, below the network layer.
Networking Devices WIRELESS ACCESS POINT (WAP) A Wireless Access Point (WAP) is a networking hardware device that allows wireless devices to connect to a wired network using Wi-Fi, or related standards. The AP usually connects to a router (via a wired network) as a standalone device, but it can also be an integral component of the router itself.
Networking Devices WIRELESS ACCESS POINT (WAP)
Protocol
Protocol A protocol is a set of rules that governs communication. Communication between two people or two devices needs to follow some protocol. For example, in a face-to-face communication between two persons, there is a set of implicit rules in each culture that define how two persons should start the communication, how to continue the communication, and how to end the communication. Similarly, in a telephone conversation, there are a set of rules that we need to follow: • How to make connection (dialing the telephone number), • How to respond to the call (picking up the receiver), • How to greet, • How to let the communication flow smoothly by listening when the other is talking, • Finally how to end the communication (hanging up).
Protocol A protocol is a set of rules that governs communication.
Protocol In computer networks, communication occurs between entities in different systems. • An entity is anything capable of sending or receiving information. • Two entities cannot simply send bit streams to each other and expect to be understood. • For communication to occur, the entities must agree on a protocol. • A protocol defines what is communicated, how it is communicated, and when it is communicated.
OSI Reference Model The layered model that dominated data communication and networking literature before 1990 was the Open Systems Interconnection (OSI) model. The purpose of the OSI model is to show how to facilitate communication between different systems without requiring changes to the logic of the underlying hardware and software. The OSI model is not a protocol; it is a model for understanding and designing a network architecture that is flexible, robust, and interoperable.
OSI Reference Model The OSI model is a layered framework for the design of network systems that allows communication between all types of computer systems. It consists of seven separate but related layers, each of which defines a part of the process of moving information across a network.
OSI Reference Model
Layers in the OSI Model Physical Layer: Coordinates the functions required to carry a bit stream over a physical medium. It deals with the mechanical and electrical specifications of the interface and transmission media. The physical layer data consists of a stream of bits (sequence of 0s or 1s) with no interpretation. To be transmitted, bits must be encoded into signals - electrical or optical. The physical layer defines the type of encoding.
Layers in the OSI Model Data Link Layer: The data link layer transforms the physical layer, a raw transmission facility, to a reliable link. It makes the physical layer appear error-free to the upper layer (network layer). Other responsibilities of the data link layer include the following: • Framing: The data link layer divides the stream of bits received from the network layer into manageable data units called frames. • Physical addressing: If frames are to be distributed to different systems on the network, the data link layer adds a header to the frame to define the sender and/or receiver of the frame. If the frame is intended for a system outside the sender’s network, the receiver address.
Layers in the OSI Model Network Layer The network layer is responsible for the source-to-destination delivery of a packet, possibly across multiple networks (links). Whereas the data link layer oversees the delivery of the packet between two systems on the same network (link), the network layer ensures that each packet gets from its point of origin to its final destination. Other responsibilities of the network layer include the following: • Logical addressing (Adds a header to the packet coming from the upper layer that, among other things, includes the logical addresses of the sender and receiver.) • Routing (When independent networks or links are connected together route or switch the packets to their final destination. )
Layers in the OSI Model Transport Layer The transport layer is responsible for delivery of the entire message. Transmission Control Protocol (TCP) or User Datagram Protocol (UDP)?
Unicast (one single recipient), Multicast (a group of recipients), Broadcast (to be received by all systems in the network)
Layers in the OSI Model Session Layer The services provided by the first four layers (physical, data link, network and transport) are not sufficient for some processes. The session layer is the network dialog controller. It establishes, maintains, and synchronizes the interaction between communicating systems.
Presentation Layer The presentation layer is concerned with the syntax and semantics of the information exchanged between two systems. Specific responsibilities of the presentation layer include the following: Translation, Encryption, and Compression.)
Layers in the OSI Model Application Layer The application layer enables the user, whether human or software, to access the network. It provides user interfaces and support for services such as electronic mail, remote file access and transfer, shared database management, and other types of distributed information services.
Layers in the OSI Model Summary of OSI Layers
TCP/IP PROTOCOL SUITE The TCP/IP protocol suite was developed prior to the OSI model. Therefore, the layers in the TCP/IP protocol suite do not match exactly with those in the OSI model. TCP/IP is thought of as a five-layer model with the layers named similarly to the ones in the OSI model.
Next Topics: TCP / IP Protocol Suite Addressing IP Address and Classes