Questions 2
Which protocol uses physical layer?
Ethernet (Physical/Data Link Layers) IP/IPX (Network Layer) TCP/SPX (Transport Layer) HTTP, FTP, Telnet, SMTP, and DNS(combined Session/Presentation/Application Layers)
What is the purpose of the physical layer?
It provides a means to transfer the bits that make up the encapsulated data. This layer encodes the frames and creates the electrical, optical, or radio wave signals that represent the bits.
What is latency and throughput?
Latency is the time required to perform some action or to produce some result. Latency is measured in units of time -- hours, minutes, seconds, nanoseconds or clock periods. Throughput is the number of such actions executed or results produced per unit of time.
Lucent connector (LC) simplex connectors
A smaller version of the fiber-optic SC connector. It is sometimes called a little or local connector and is quickly growing in popularity due to its smaller size.
What is bus topology advantages and disadvantages?
Advantages of a Linear Bus Topology Easy to connect a computer or peripheral to a linear bus. Requires less cable length than a star topology. Disadvantages of a Linear Bus Topology Entire network shuts down if there is a break in the main cable. Terminators are required at both ends of the backbone cable. Difficult to identify the problem if the entire network shuts down. Not meant to be used as a stand-alone solution in a large building.
Advantages and disadvantages of a Mesh Topology
Advantages of a mesh topology Manages high amounts of traffic, because multiple devices can transmit data simultaneously. A failure of one device does not cause a break in the network or transmission of data. Adding additional devices does not disrupt data transmission between other devices. Disadvantages of a mesh topology The cost to implement is higher than other network topologies, making it a less desirable option. Building and maintaining the topology is difficult and time consuming. The chance of redundant connections is high, which adds to the high costs and potential for reduced efficiency.
Fiber Optic Connectors
An optical fiber connector terminates the end of an optical fiber. A variety of optical fiber connectors are available. The main differences among the types of connectors are dimensions and methods of coupling. Businesses decide on the types of connectors that will be used, based on their equipment.
Disadvantages of Wireless Communication
An unauthorized person can easily capture the wireless signals which spread through the air. It is very important to secure the wireless network so that the information cannot be misused by unauthorized users
What are the advantages of Bluetooth over WiFi?
Bluetooth have very short range when compared to WiFi. With the help of Bluetooth you could send data and voice but in WiFi you can't. Bluetooth is secure because it uses two step authentication process and it is point to point connection and you can connect only one device with Bluetooth .
Layer 2 Addressing vs Layer 3 Addressing
Layer 2: -Data Link Layer -MAC Address Layer 3: -Network/Internet Layer -IP Address
Physical Point-to-Point Topology
Physical point-to-point topologies directly connect two nodes. In this arrangement, two nodes do not have to share the media with other hosts. Additionally, a node does not have to make any determination about whether an incoming frame is destined for it or another node. Therefore, the logical data link protocols can be very simple, as all frames on the media can only travel to or from the two nodes. The frames are placed on the media by the node at one end and taken from the media by the node at the other end of the point-to-point circuit.
What is difference between half duplex and full duplex?
The Difference Between Half and Full Duplex Explained. "Duplex" simply means you're able to send and receive data (most often the human voice) from the same device whether that be with your phone, 2-way radio, or PC. Half-duplex devices let you send and receive, but only one-way at a time.
Why does the OSI model have 7 layers?
The Open System Interconnection (OSI) model defines a networking framework to implement protocols in seven layers. ... The Open System Interconnection (OSI) model defines a networking framework to implement protocols in seven layers. There is really nothing to the OSI model. In fact, it's not even tangible.
What does a logical topology depend on?
A logical topology is a concept in networking that defines the architecture of the communication mechanism for all nodes in a network. Using network equipment such as routers and switches, the logical topology of a network can be dynamically maintained and reconfigured.
What is the example of half duplex?
An example of a half-duplex system is a two-party system such as a walkie-talkie, wherein one must use "over" or another previously designated keyword to indicate the end of transmission, and ensure that only one party transmits at a time, because both parties transmit and receive on the same frequency.
Contention-Based Access - CSMA/CA
Another form of CSMA that is used by IEEE 802.11 WLANs is Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA). CMSA/CA uses a method similar to CSMA/CD to detect if the media is clear. CMSA/CA also uses additional techniques. CMSA/CA does not detect collisions but attempts to avoid them by waiting before transmitting. Each device that transmits includes the time duration that it needs for the transmission. All other wireless devices receive this information and know how long the medium will be unavailable. After a wireless device sends an 802.11 frame, the receiver returns an acknowledgment so that the sender knows the frame arrived. Whether it is an Ethernet LAN using hubs, or a WLAN, contention-based systems do not scale well under heavy media use. It is important to note that Ethernet LANs using switches do not use a contention-based system because the switch and the host NIC operate in full-duplex mode.
What happens at the physical layer?
At the physical layer, binary expressions (that is, a series of 1s and 0s) represent data. A binary expression is made up of bits, where a bit is a single 1 or a single 0. How bits are represented on the medium Wiring standards for connectors and jacks Physical topology Synchronizing bits Bandwidth usage Multiplexing strategy
What is the difference between a physical and logical topology?
A logical topology is how devices appear connected to the user. A physical topology is how they are actually interconnected with wires and cables. ... However, its physical topology is a star, in which every node on the network connects to a central hub. See Ethernet and logical vs. physical.
Advantages and disadvantages of a Star Topology
Advantages of a Star Topology Easy to install and wire. No disruptions to the network when connecting or removing devices. Easy to detect faults and to remove parts. Disadvantages of a Star Topology Requires more cable length than a linear topology. If the hub, switch, or concentrator fails, nodes attached are disabled. More expensive than linear bus topologies because of the cost of the hubs, etc. Tree or Expanded Star
Advantages and disadvantages of a Tree Topology
Advantages of a Tree Topology Point-to-point wiring for individual segments. Supported by several hardware and software venders. Disadvantages of a Tree Topology Overall length of each segment is limited by the type of cabling used. If the backbone line breaks, the entire segment goes down. More difficult to configure and wire than other topologies.
Advantages and disadvantages of a Ring Topology
Advantages of ring topology All data flows in one direction, reducing the chance of packet collisions. A network server is not needed to control network connectivity between each workstation. Data can transfer between workstations at high speeds. Additional workstations can be added without impacting performance of the network. Disadvantages of ring topology All data being transferred over the network must pass through each workstation on the network, which can make it slower than a star topology. The entire network will be impacted if one workstation shuts down. The hardware needed to connect each workstation to the network is more expensive than Ethernet cards and hubs/switches.
Full Duplex
Communication that happens in two directions at the same time. Any device that can send and receive data simultaneously. ull-duplex communication - Both devices can transmit and receive on the media at the same time. The data link layer assumes that the media is available for transmission for both nodes at any time. Ethernet switches operate in full-duplex mode by default, but can operate in half-duplex if connecting to a device such as an Ethernet hub. is important that two interconnected interfaces, such as a host's NIC and an interface on an Ethernet switch operate using the same duplex mode. Otherwise, there will be a duplex mismatch creating inefficiency and latency on the link.
What are the five main types of physical network topologies?
Mesh Topology. Mesh Topology: In a mesh network, devices are connected with many redundant interconnections between network nodes. ... Star Topology. Star Topology: In a star network devices are connected to a central computer, called a hub. ... Bus Topology. ... Ring Topology. ... Tree Topology.
Physical LAN Topologies
Star - End devices are connected to a central intermediate device. Early star topologies interconnected end devices using Ethernet hubs. However, star topologies now use Ethernet switches. The star topology is easy to install, very scalable (easy to add and remove end devices), and easy to troubleshoot. Extended Star - In an extended star topology, additional Ethernet switches interconnect other star topologies. An extended star is an example of a hybrid topology. Bus - All end systems are chained to each other and terminated in some form on each end. Infrastructure devices such as switches are not required to interconnect the end devices. Bus topologies using coax cables were used in legacy Ethernet networks because it was inexpensive and easy to set up. Ring - End systems are connected to their respective neighbor forming a ring. Unlike the bus topology, the ring does not need to be terminated. Ring topologies were used in legacy Fiber Distributed Data Interface (FDDI) and Token Ring networks.
frame
The data link layer prepares a packet for transport across the local media by encapsulating it with a header and a trailer to create a frame. The description of a frame is a key element of each data link layer protocol. Although there are many different data link layer protocols that describe data link layer frames, each frame type has three basic parts: Header Data Trailer All data link layer protocols encapsulate the Layer 3 PDU within the data field of the frame. However, the structure of the frame and the fields contained in the header and trailer vary according to the protocol. There is no one frame structure that meets the needs of all data transportation across all types of media. Depending on the environment, the amount of control information needed in the frame varies to match the access control requirements of the media and logical topology.
What are physical topologies?
The physical topology is the way you physically lay out the network, like a map, and the logical topology is the way the information flows on the network. Usually, the physical and logical topology is the same, but sometimes they can differ, such as in a physical star/logical ring topology.
What are the three primary logical topologies?
There are really three basic types of topologies. They are Star, Bus, and Ring. Let me explain them to you. Star - All computers and devices are connected to a centrally located hub or switch.
Layer 2 Address
he data link layer provides addressing that is used in transporting a frame across a shared local media. Device addresses at this layer are referred to as physical addresses. Data link layer addressing is contained within the frame header and specifies the frame destination node on the local network. The frame header may also contain the source address of the frame. Unlike Layer 3 logical addresses, which are hierarchical, physical addresses do not indicate on what network the device is located. Rather, the physical address is unique to the specific device. If the device is moved to another network or subnet, it will still function with the same Layer 2 physical address. function of the Layer 2 and Layer 3 addresses. As the IP packet travels from host-to-router, router-to-router, and finally router-to-host, at each point along the way the IP packet is encapsulated in a new data link frame. Each data link frame contains the source data link address of the NIC card sending the frame, and the destination data link address of the NIC card receiving the frame. An address that is device-specific and non-hierarchical cannot be used to locate a device on large networks or the Internet. This would be like trying to find a single house within the entire world, with nothing more than a house number and street name. The physical address, however, can be used to locate a device within a limited area. For this reason, the data link layer address is only used for local delivery. Addresses at this layer have no meaning beyond the local network. Compare this to Layer 3, where addresses in the packet header are carried from the source host to the destination host, regardless of the number of network hops along the route. If the data must pass onto another network segment, an intermediate device, such as a router, is necessary. The router must accept the frame based on the physical address and de-encapsulate the frame in order to examine the hierarchical address, or IP address. Using the IP address, the router is able to determine the network location of the destination device and the best path to reach it. When it knows where to forward the packet, the router then creates a new frame for the packet, and the new frame is sent on to the next network segment toward its final destination.
What is physical layer security?
Compared to cryptographic approaches, physical layer security is a fundamentally different paradigm where secrecy is achieved by exploiting the physical layer properties of the communication system, such as thermal noise, interference, and the time-varying nature of fading channels.
Frame Fields
Framing breaks the stream into decipherable groupings, with control information inserted in the header and trailer as values in different fields. This format gives the physical signals a structure that can be received by nodes and decoded into packets at the destination. frame field types include: Frame start and stop indicator flags - Used to identify the beginning and end limits of the frame. Addressing - Indicates the source and destination nodes on the media. Type - Identifies the Layer 3 protocol in the data field. Control - Identifies special flow control services such as quality of service (QoS). QoS is used to give forwarding priority to certain types of messages. Data link frames carrying voice over IP (VoIP) packets normally receive priority because they are sensitive to delay. Data - Contains the frame payload (i.e., packet header, segment header, and the data). Error Detection - These frame fields are used for error detection and are included after the data to form the trailer. Not all protocols include all of these fields. The standards for a specific data link protocol define the actual frame format. Data link layer protocols add a trailer to the end of each frame. The trailer is used to determine if the frame arrived without error. This process is called error detection and is accomplished by placing a logical or mathematical summary of the bits that comprise the frame in the trailer. Error detection is added at the data link layer because the signals on the media could be subject to interference, distortion, or loss that would substantially change the bit values that those signals represent. A transmitting node creates a logical summary of the contents of the frame, known as the cyclic redundancy check (CRC) value. This value is placed in the Frame Check Sequence (FCS) field to represent the contents of the frame. In the Ethernet trailer, the FCS provides a method for the receiving node to determine whether the frame experienced transmission errors.
LAN and WAN Frames
In a TCP/IP network, all OSI Layer 2 protocols work with IP at OSI Layer 3. However, the Layer 2 protocol used depends on the logical topology and the physical media. Each protocol performs media access control for specified Layer 2 logical topologies. This means that a number of different network devices can act as nodes that operate at the data link layer when implementing these protocols. These devices include the NICs on computers as well as the interfaces on routers and Layer 2 switches. The Layer 2 protocol used for a particular network topology is determined by the technology used to implement that topology. The technology is, in turn, determined by the size of the network - in terms of the number of hosts and the geographic scope - and the services to be provided over the network. A LAN typically uses a high bandwidth technology that is capable of supporting large numbers of hosts. A LAN's relatively small geographic area (a single building or a multi-building campus) and its high density of users, make this technology cost-effective. However, using a high bandwidth technology is usually not cost-effective for WANs that cover large geographic areas (cities or multiple cities, for example). The cost of the long distance physical links and the technology used to carry the signals over those distances typically results in lower bandwidth capacity. The difference in bandwidth normally results in the use of different protocols for LANs and WANs. Data link layer protocols include: Ethernet 802.11 Wireless Point-to-Point Protocol (PPP) HDLC Frame Relay
What are the types of logical topology?
Logical topologies are bound to the network protocols that direct how the data moves across a network. ... For example, twisted pairEthernet is a logical bus topology in a physical star topology layout. While IBM's Token Ring is a logical ring topology, it is physically set up in a star topology.
Which topology is logical topology?
Logical topology is the arrangement of devices on a computer network and how they communicate with one another. ... Early twisted pair Ethernet with a single hub is a logical bus topology with a physical star topology. While token ring is a logical ring topology with a physical star topology.
Common Physical WAN Topologies
Point-to-Point: Hub and Spoke: Mesh: WANs are commonly interconnected using the following physical topologies: Point-to-Point - This is the simplest topology that consists of a permanent link between two endpoints. For this reason, this is a very popular WAN topology. Hub and Spoke - A WAN version of the star topology in which a central site interconnects branch sites using point-to-point links. Mesh - This topology provides high availability, but requires that every end system be interconnected to every other system. Therefore, the administrative and physical costs can be significant. Each link is essentially a point-to-point link to the other node. A hybrid is a variation or combination of any of the above topologies. For example, a partial mesh is a hybrid topology in which some, but not all, end devices are interconnected.
What is half duplex mode?
Refers to the transmission of data in just one direction at a time. For example, a walkie-talkie is a half-duplex device because only one party can talk at a time. In contrast, a telephone is a full-duplex device because both parties can talk simultaneously.
Which of the following devices is full duplex?
Refers to the transmission of data in two directions simultaneously. For example, a telephone is a full-duplex device because both parties can talk at once. In contrast, a walkie-talkie is a half-duplex device because only one party can transmit at a time.
What is the most commonly used physical topology?
Star topology is the most popular network topology in businesses today. It consists of nodes connected to a central switch or hub. If you have a home network, you are probably using the star topology. Bus topology is one which consists of all of the workstations connected to a single cable.
Logical Point-to-Point Topology
The end nodes communicating in a point-to-point network can be physically connected via a number of intermediate devices. However, the use of physical devices in the network does not affect the logical topology. the source and destination node may be indirectly connected to each other over some geographical distance. In some cases, the logical connection between nodes forms what is called a virtual circuit. A virtual circuit is a logical connection created within a network between two network devices. The two nodes on either end of the virtual circuit exchange the frames with each other. This occurs even if the frames are directed through intermediary devices. Virtual circuits are important logical communication constructs used by some Layer 2 technologies. The media access method used by the data link protocol is determined by the logical point-to-point topology, not the physical topology. This means that the logical point-to-point connection between two nodes may not necessarily be between two physical nodes at each end of a single physical link.
Contention-Based Access - CSMA/CD
WLANs, Ethernet LANs with hubs, and legacy Ethernet bus networks are all examples of contention-based access networks. All of these networks operate in half-duplex mode. This requires a process to govern when a device can send and what happens when multiple devices send at the same time. The Carrier Sense Multiple Access/Collision Detection (CSMA/CD) process is used in half-duplex Ethernet LANs. The CSMA process is as follows: 1. PC1 has an Ethernet frame to send to PC3. 2. PC1's NIC needs to determine if anyone is transmitting on the medium. If it does not detect a carrier signal, in other words, it is not receiving transmissions from another device, it will assume the network is available to send. 3. PC1's NIC sends the Ethernet Frame. 4. The Ethernet hub receives the frame. An Ethernet hub is also known as a multiport repeater. Any bits received on an incoming port are regenerated and sent out all other ports. 5. If another device, such as PC2, wants to transmit, but is currently receiving a frame, it must wait until the channel is clear. 6. All devices attached to the hub will receive the frame. Because the frame has a destination data link address for PC3, only that device will accept and copy in the entire frame. All other devices' NICs will ignore the frame. If two devices transmit at the same time, a collision will occur. Both devices will detect the collision on the network, this is the collision detection (CD). This is done by the NIC comparing data transmitted with data received, or by recognizing the signal amplitude is higher than normal on the media. The data sent by both devices will be corrupted and will need to be resent.
How long does fiber optic cable last?
25 years last as long as or longer than such times. There are numerous fiber optic cables in operation around the world for these applications longer than those times. Tax depreciation schedules for fiber optic cable are often 15 years or more. Operators installing optical cable typically presume a service life of 25 years.
Wireless LAN (WLAN)
A type of LAN that does not use wires or cables to create connections, but instead transmits data over radio or infrared waves. Radio signals are transmitted and received over distances of a few hundred feet.
What is WLAN used for?
A wireless local area network (WLAN) is a wireless distribution method for two or more devices that use high-frequency radio waves and often include an access point to the Internet. A WLAN allows users to move around the coverage area, often a home or small office, while maintaining a network connection.
How does a wireless LAN work?
A wireless network allows devices to stay connected to the network but roam untethered to any wires. Access points amplify Wi-Fi signals, so a device can be far from a router but still be connected to the network. A wired network has some disadvantages when compared to a wireless network.
Advantages of Wireless Communication
Any data or information can be transmitted faster and with a high speed Maintenance and installation is less cost for these networks. The internet can be accessed from anywhere wirelessly It is very helpful for workers, doctors working in remote areas as they can be in touch with medical centers.
What are the 7 layers of the OSI model?
Application, Presentation, Session, Transport, Network, Data Link, Physical
Is WiMAX used today?
Back in the early 2000s, the WiMAX Forum developed a new wireless technology known as WiMAX —short for Worldwide Interoperability for Microwave Access. The new technology was standardized by the IEEE as 802.16. ... Yet, WiMAX is still around. It is still widely used for wireless Internet access especially outside the U.S.
What is bandwidth?
Bandwidth describes the maximum data transfer rate of a network or Internet connection. It measures how much data can be sent over a specific connection in a given amount of time. For example, a gigabit Ethernet connection has a bandwidth of 1,000 Mbps, (125 megabytes per second).
What is difference between bandwidth and throughput?
Bandwidth is the maximum throughput you can ever achieve while the actual speed that we experience while surfing is the throughput. Bandwidth is the theoretical maximum amount of data that you can send per unit of time. Throughput is how much actually gets through in the real world at any given instant.
What is the difference between bandwidth and latency?
Bandwidth vs Latency. ... Latency is the amount of time it takes for data to travel from one point to another. It is dependent on the physical distance that data must travel through cords, networks and the like to reach its destination. Bandwidth is the rate of data transfer for a fixed period of time.3
Types of cable Categories
CAT3: Rarely used today, CAT3 is usually deployed in phone lines. It supports 10 Mbps for up to 100 meters. CAT4: Typically used in token ring networks, CAT4 supports 16 Mbps for up to 100 meters. CAT5: Used in Ethernet-based LANs, CAT5 contains two twisted pairs. It supports 100 Mbps for up to 100 meters. CAT5e: Used in Ethernet-based LANs, CAT5e contains four twisted pairs. It supports 1 Gbps for 100 meters. CAT6: Used in Ethernet-based LANs and data center networks, CAT6 contains four tightly wound twisted pairs. It supports 1 Gbps for up to 100 meters and 10 Gbps for up to 50 meters. The most common connector used with UTP cable is an RJ-45. The following are the main cable types that are obtained by using specific wiring conventions: Ethernet Straight-through: The most common type of networking cable. It is commonly used to interconnect a host to a switch and a switch to a router. Ethernet Crossover: A cable used to interconnect similar devices. For example to connect a switch to a switch, a host to a host, or a router to a router. Rollover: A Cisco proprietary cable used to connect a workstation to a router or switch console port.
What are the devices used in physical layer?
Devices that operate at the physical layer include repeaters, hubs, network interface cards (NICs), cables and connectors. Repeaters are used to regenerate electrical signals that have attenuated (i.e., weakened) as a result of distance.
How does crosstalk degrade signals on copper media?
EMI occurs when electrical signals from the local environment outside of the binder are picked up by the copper pairs in a cable and introduce noise. Crosstalk occurs when a signal transmitted on one copper twisted pair in a bundle radiates and potentially interferes with and degrades the transmission on another pair.
What is a data link address?
Each device on a network has a unique number, usually called a hardware address or MAC address, that is used by the data link layer protocol to ensure that data intended for a specific machine gets to it properly.
What is the maximum bandwidth of fiber optic cable?
It is mostly used for short distance communication, such as within a building or on a campus. Typically, the multimode fiber optic cable speed and the transmitting distance limits are 100 Mbit/s for distance up to 2 km (100BASE-FX), Gbit/s up to 1000m, and 10 Gbit/s up to 550 m.
What is WiMAX and how does it work?
It's called WiMax. Along with a competing standard called "LTE," WiMax, short for Worldwide Interoperability for Microwave Access, represents 4G or the "fourth generation" of wireless Internet. The new technology is similar to Wi-Fi in that it allows users to connect to the Internet without wires.
What is LC SC connectors in fiber?
LC is a small form factor connector that uses a 1.25 mm ferrule, half the size of the SC. Otherwise, it's a standard ceramic ferrule connector, easily terminated with any adhesive. Good performance, highly favored for singlemode. The LC, MU and LX-5 use the same ferrule but cross-mating adapters are not easy to find.
Media Access Control (MAC)
Layer 2 protocols specify the encapsulation of a packet into a frame and the techniques for getting the encapsulated packet on and off each medium. The technique used for getting the frame on and off the media is called the media access control method. As packets travel from the source host to the destination host, they typically traverse over different physical networks. These physical networks can consist of different types of physical media such as copper wires, optical fibers, and wireless consisting of electromagnetic signals, radio and microwave frequencies, and satellite links. Without the data link layer, network layer protocols such as IP, would have to make provisions for connecting to every type of media that could exist along a delivery path. Moreover, IP would have to adapt every time a new network technology or medium was developed. This process would hamper protocol and network media innovation and development. This is a key reason for using a layered approach to networking.
Types of fiber media
Light pulses representing the transmitted data as bits on the media are generated by either: Lasers Light emitting diodes (LEDs) Electronic semiconductor devices called photodiodes detect the light pulses and convert them to voltages. The laser light transmitted over fiber-optic cabling can damage the human eye. Care must be taken to avoid looking into the end of an active optical fiber. Fiber-optic cables are broadly classified into two types: SMF (single-mode fiber) - Consists of a very small core and uses expensive laser technology to send a single ray of light, as shown in Figure 1. Popular in long-distance situations spanning hundreds of kilometers, such as those required in long haul telephony and cable TV applications. MMF (multimode fiber) - Consists of a larger core and uses LED emitters to send light pulses. Specifically, light from an LED enters the multimode fiber at different angles. Popular in LANs because they can be powered by low-cost LEDs. It provides bandwidth up to 10 Gb/s over link lengths of up to 550 meters. One of the highlighted differences between multimode and single-mode fiber is the amount of dispersion. Dispersion refers to the spreading out of a light pulse over time. The more dispersion there is, the greater the loss of signal strength.
Fiber Optics Terminology
Multimode can help data travel approximately 1.24 miles or 2km or 2000m Uses light emitting diodes (LEDS) as light source transmitter. Used within a campus network. Single Mode Uses lasers in a single stream as a light source transmitter. used to connect long distance telephony cable tv applications. Can travel approximately 62.5 miles or 100km or 10,000 meters.
What is multimode fiber used for?
Multimode fiber transmission is used for relatively short distances because the modes tend to disperse over longer lengths (this is called modal dispersion) . For longer distances, single mode fiber (sometimes called monomode) fiber is used. Multimode fiber has a larger core than single mode.
Why do networks use copper media?
Networks use copper media because it is inexpensive, easy to install, and has low resistance to electrical current. However, copper media is limited by distance and signal interference. Data is transmitted on copper cables as electrical pulses.
What is OSI model explain in detail?
OSI (Open Systems Interconnection) is a reference model for how applications communicate over a network. A reference model is a conceptual framework for understanding relationships. ... The TCP/IP protocol suite, which defines the internet, does not map cleanly to the OSI model.
Data Link Layer (Layer 2)
OSI Layer: gets data to physical layer so it can transmit over network. Responsible for error detection, error correction, and hardware addressing. Frame describes a logical grouping of data at this layer. Two Sublayers: Media Access Control (MAC) layer and Logical Link Control Layer (LLC - for errors and flow control).
Properties of Fiber-Optic Cabling
Optical fiber cable transmits data over longer distances and at higher bandwidths than any other networking media. Unlike copper wires, fiber-optic cable can transmit signals with less attenuation and is completely immune to EMI and RFI. Optical fiber is commonly used to interconnect network devices. Optical fiber is a flexible, but extremely thin, transparent strand of very pure glass, not much bigger than a human hair. Bits are encoded on the fiber as light impulses. The fiber-optic cable acts as a waveguide, or "light pipe," to transmit light between the two ends with minimal loss of signal. As an analogy, consider an empty paper towel roll with the inside coated like a mirror. It is a thousand meters in length, and a small laser pointer is used to send Morse code signals at the speed of light. Essentially that is how a fiber-optic cable operates, except that it is smaller in diameter and uses sophisticated light technologies. Fiber-optic cabling is now being used in four types of industry: Enterprise Networks: Used for backbone cabling applications and interconnecting infrastructure devices. Fiber-to-the-Home (FTTH): Used to provide always-on broadband services to homes and small businesses. Long-Haul Networks: Used by service providers to connect countries and cities. Submarine Cable Networks: Used to provide reliable high-speed, high-capacity solutions capable of surviving in harsh undersea environments up to transoceanic distances.
Where is fiber optic cable most commonly used?
Optical fibers are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths (data rates) than electrical cables.
What is process to process communication?
Process to Process Communication: UDP and TCP/IP. So far we have seen how arbitrary hosts communicate with each other. ... The unit of transfer in this layer is the UDP datagram, and the destination is an input port within a host. Thus, the destination of a message is specified as the pair (host, port).
What is shielded Twisted Pair (STP)?
Shielded twisted-pair (STP) provides better noise protection than UTP cabling. However, compared to UTP cable, STP cable is significantly more expensive and difficult to install. Like UTP cable, STP uses an RJ-45 connector. STP cables combine the techniques of shielding to counter EMI and RFI, and wire twisting to counter crosstalk. To gain the full benefit of the shielding, STP cables are terminated with special shielded STP data connectors. If the cable is improperly grounded, the shield may act as an antenna and pick up unwanted signals. uses four pairs of wires, each wrapped in a foil shield, which are then wrapped in an overall metallic braid or foil.
What is difference between single mode and multimode fiber?
Single Mode and Multimode Fiber Overview. Single mode means the fiber enables one type of light mode to be propagated at a time. While multimode means the fiber can propagate multiple modes. The difference between single mode and multimode fiber mainly lies in fiber core diameter, wavelength, light source and bandwidth .
Which is faster Bluetooth or WiFi?
So no, Bluetooth is not faster than Wi-Fi. Not even vaguely close. Bluetooth version 3 and version 4 have higher data rates, but the actual data transfer in those implementations happens over Wi-Fi; Bluetooth is only used to set up and negotiate the connection.
What is the difference between TCP IP model and OSI model?
TCP/IP model is a protocol-oriented standard. OSI model distinguishes the three concepts, namely, services, interfaces, and protocols. TCP/IP does not have a clear distinction between these three. ... In OSI, the model was developed first and then the protocols in each layer were developed.
What is difference between WLAN and WiFi?
Technically, WLAN means any wireless local area network no matter what technology is used and Wi-Fi is a type of WLAN that follows the IEEE 802.11 standards which most WLANs in use today do, that's why they are commonly used interchangeably. Wi-Fi as a name for the standard is a trademark of the Wi-Fi Alliance.
WiMAX
Technology that allows wireless Internet access over a wide area that can deliver maximum speeds of up to 7 Mbps to your cell phone, home computer, or car. Stands for Worldwide Interoperability for Microwave Access.
What connector does fiber optic cable use?
The ST connector was one of the first connector types widely implemented in fiber optic networking applications. Originally developed by AT&T, it stands for Straight Tip connector. ST connections use a 2.5mm ferrule with a round plastic or metal body.
What is the difference between shielded and unshielded twisted pair cable?
The basic difference between UTP and STP is UTP (Unshielded twisted pair) is a cable with wires that are twisted together to reduce noise and crosstalk. On the contrary, STP (Shielded twisted pair) is a twisted pair cable confined in foil or mesh shield that guards the cable against electromagnetic interference.
What are the main components of a wireless network?
The basic wireless, peer-to-peer network consists of these components: Wireless router: The heart of the wireless network is the wireless router. ... Wire-based connections: Almost every wireless router I've seen has one or more standard, wire-based Ethernet port.
What is a function of the data link layer?
The data link layer is divided into two sublayers: Logical Link Control (LLC) - This upper sublayer communicates with the network layer. It places information in the frame that identifies which network layer protocol is being used for the frame. This information allows multiple Layer 3 protocols, such as IPv4 and IPv6, to utilize the same network interface and media. Media Access Control (MAC) - This lower sublayer defines the media access processes performed by the hardware. It provides data link layer addressing and access to various network technologies.
Which device works on which layer of OSI model?
The devices that typically operate at the Internet layer are routers. The Internet layer of the TCP/IP model corresponds to the Network layer (Layer 3) of the OSI model.
What is end to end transmission?
The end-to-end principle is a design framework in computer networking. In networks designed according to this principle, application-specific features reside in the communicating end nodes of the network, rather than in intermediary nodes, such as gateways and routers, that exist to establish the network.
Which protocol works on which layer?
The following are the OSI protocols used in the seven layers of the OSI Model: Layer 1, the Physical Layer: This layer deals with the hardware of networks such as cabling. The major protocols used by this layer include Bluetooth, PON, OTN, DSL, IEEE.802.11, IEEE.802.3, L431 and TIA 449. Layer 2, the Data Link Layer: This layer receives data from the physical layer and compiles it into a transform form called framing or frame. The protocols are used by the Data Link Layer include: ARP, CSLIP, HDLC, IEEE.802.3, PPP, X-25, SLIP, ATM, SDLS and PLIP. Layer 3, the Network Layer: This is the most important layer of the OSI model, which performs real time processing and transfers data from nodes to nodes. Routers and switches are the devices used for this layer. The network layer assists the following protocols: Internet Protocol (IPv4), Internet Protocol (IPv6), IPX, AppleTalk, ICMP, IPSec and IGMP. Layer 4, the Transport Layer: The transport layer works on two determined communication modes: Connection oriented and connectionless. This layer transmits data from source to destination node. It uses the most important protocols of OSI protocol family, which are: Transmission Control Protocol (TCP), UDP, SPX, DCCP and SCTP. Layer 5, the Session Layer: The session layer creates a session between the source and the destination nodes and terminates sessions on completion of the communication process. The protocols used are: PPTP, SAP, L2TP and NetBIOS. Layer 6, the Presentation Layer: The functions of encryption and decryption are defined on this layer. It converts data formats into a format readable by the application layer. The following are the presentation layer protocols: XDR, TLS, SSL and MIME. Layer 7, the Application Layer: This layer works at the user end to interact with user applications. QoS (quality of service), file transfer and email are the major popular services of the application layer. This layer uses following protocols: HTTP, SMTP, DHCP, FTP, Telnet, SNMP and SMPP.
What is the difference between WIFI and Bluetooth?
The main difference is that Bluetooth is primarily used to connect devices without using cables, while Wi-Fi provides high-speed access to the internet. Bluetooth is a wireless technology standard that is used to exchange data over short distances (less than 30 feet), usually between personal mobile devices.
What are the functions of physical layer?
The main functions of the physical layer are as follows: It defines the physical characteristics and functions of the physical devices and interfaces so that transmission can occur. It states the number of pins in each of the devices as well as the purpose of each pin. It lays out the transmission medium and type of signal for transmitting the bits, i.e., electrical pulses, optical pulses or radio signals. It defines the procedure of encoding of the bits, for example, how many volts should represent a 0 bit and 1 bit in case of electrical signals. It states the data transmission rate, i.e., number of bits transmitted per second; and the duration of a bit, i.e., how long a bit stays. It defines the topology, i.e., physical layout, of the network devices. It also states the direction of transmission, i.e., whether the transmission is in simplex mode, half-duplex mode or full-duplex mode.
What is the use of physical layer in OSI model?
The physical layer is the lowest layer in the OSI Model (Open Systems Interconnection Model) and is used for transmitting data in its basic form: bit-level. Transmission medium can either be wired or wireless.
What is the difference between copper and fiber cable?
The reason fiber optic cable is faster is because of the extremely high frequency ranges it is able to carry, whereas signal strength diminishes at high frequencies with copper wire. Fiber optic cable can carry more than a thousand times the bandwidth of copper cable and go more than one hundred times further as well.
How fast does data travel on fiber optic cable?
The speed of light in a vacuum is 299,792,458 meters per second, or 186,282 miles per second. In any other medium, though, it's generally a lot slower. In normal optical fibers (silica glass), light travels a full 31% slower.
/what are Characteristics of Copper Cabling?
The timing and voltage values of the electrical pulses are also susceptible to interference from two sources: Electromagnetic interference (EMI) or radio frequency interference (RFI) - EMI and RFI signals can distort and corrupt the data signals being carried by copper media. Potential sources of EMI and RFI include radio waves and electromagnetic devices, such as fluorescent lights or electric motors. Crosstalk - Crosstalk is a disturbance caused by the electric or magnetic fields of a signal on one wire to the signal in an adjacent wire. In telephone circuits, crosstalk can result in hearing part of another voice conversation from an adjacent circuit. Specifically, when an electrical current flows through a wire, it creates a small, circular magnetic field around the wire, which can be picked up by an adjacent wire. To counter the negative effects of EMI and RFI, some types of copper cables are wrapped in metallic shielding and require proper grounding connections. To counter the negative effects of crosstalk, some types of copper cables have opposing circuit wire pairs twisted together, which effectively cancels the crosstalk. The susceptibility of copper cables to electronic noise can also be limited by: Selecting the cable type or category most suited to a given networking environment. Designing a cable infrastructure to avoid known and potential sources of interference in the building structure. Using cabling techniques that include the proper handling and termination of the cables.
What are the Characteristics of Copper Cabling
The timing and voltage values of the electrical pulses are also susceptible to interference from two sources: Electromagnetic interference (EMI) or radio frequency interference (RFI) - EMI and RFI signals can distort and corrupt the data signals being carried by copper media. Potential sources of EMI and RFI include radio waves and electromagnetic devices such as fluorescent lights or electric motors. Crosstalk - Crosstalk is a disturbance caused by the electric or magnetic fields of a signal on one wire to the signal in an adjacent wire. In telephone circuits, crosstalk can result in hearing part of another voice conversation from an adjacent circuit. Specifically, when electrical current flows through a wire, it creates a small, circular magnetic field around the wire which can be picked up by an adjacent wire.
Physical and Logical Topologies
The topology of a network is the arrangement or relationship of the network devices and the interconnections between them. LAN and WAN topologies can be viewed in two ways: Physical topology - Refers to the physical connections and identifies how end devices and infrastructure devices such as routers, switches, and wireless access points are interconnected. Physical topologies are usually point-to-point or star. Logical topology - Refers to the way a network transfers frames from one node to the next. This arrangement consists of virtual connections between the nodes of a network. These logical signal paths are defined by data link layer protocols. The logical topology of point-to-point links is relatively simple while shared media offers different access control methods. The data link layer "sees" the logical topology of a network when controlling data access to the media. It is the logical topology that influences the type of network framing and media access control used.
What are 3 types of wireless connections?
There are basically three different types of wireless networks - WAN, LAN and PAN: Wireless Wide Area Networks (WWAN): WWANs are created through the use of mobile phone signals typically provided and maintained by specific mobile phone (cellular) service providers.
Fiber versus Copper
There are many advantages to using fiber-optic cable compared to copper cables. The figure highlights some of these differences. Given that the fibers used in fiber-optic media are not electrical conductors, the media is immune to electromagnetic interference and will not conduct unwanted electrical currents due to grounding issues. Optical fibers are thin and have a relatively low signal loss and can be operated at much greater lengths than copper media. Some optical fiber physical layer specifications allow lengths that can reach multiple kilometers. At present, in most enterprise environments, optical fiber is primarily used as backbone cabling for high-traffic point-to-point connections between data distribution facilities and for the interconnection of buildings in multi-building campuses. Because optical fiber does not conduct electricity and has a low signal loss, it is well suited for these uses. bandwidth Copper - 10mb/s to 10GB/s Fiber Optic - 10 mb/s to 100gb/s Distance Copper - 1 to 500 meters Fiber Optic - 1 to 100,000 metters immunity To EMI To FRI Copper - Low Fiber Optic - High immunity To Electric Hazzards Copper - low Fiber Optic - High media and connector costs Copper - Lowest Fiber Optic - Highest installation skill required Copper - Lowest Fiber Optic - Highest safety Precautions Copper - Lowest Fiber Optic - Highest
What is Bluetooth advantages and disadvantages?
There are some important disadvantages of Bluetooth are given below, It can lose connection in certain conditions. It has low bandwidth as compared to Wi-Fi. It allows only short range communication between devices. Security is a very key aspect as it +can be hacked
Physical Layer Media
There are three basic forms of network media. The physical layer produces the representation and groupings of bits for each type of media as: Copper cable: The signals are patterns of electrical pulses. Fiber-optic cable: The signals are patterns of light. Wireless: The signals are patterns of microwave transmissions.
What is TCP and UDP?
There are two types of Internet Protocol (IP) traffic. They are TCP or Transmission Control Protocol and UDP or User Datagram Protocol. TCP is connection oriented - once a connection is established, data can be sent bidirectional. UDP is a simpler, connectionless Internet protocol.
What is throughput formula?
Throughput (also known as the flow rate) is a measure of the business process flow rate. ... The cycle plays a major role in determining the efficiency of a business. The formula is: Operating Cycle = Inventory Period + Accounts Receivable Period. It is an important metric in the operations management of a company.
What is switch throughput?
Throughput is the amount of data moved from one place to another in a given time period. Usually this is measured in bits per second (bps). ... So throughput is how much data can actually pass through a switch; switch capacity is how much data the switch can be handling at one time.
What are the types of wireless media?
Types of Wireless Communciation. Satellite Communciaiton. Infrared Communication. Broadcast Radio. Radio. Microwave Communication. Wi-Fi Communication. Mobile Communication Systems.
UTP Connectors
UTP cable is usually terminated with an RJ-45 connector. This connector is used for a range of physical layer specifications, one of which is Ethernet. The TIA/EIA-568 standard describes the wire color codes to pin assignments (pinouts) for Ethernet cables. male component, crimped at the end of the cable. The socket is the female component of a network device, wall, cubicle partition outlet, or patch panel. Each time copper cabling is terminated; there is the possibility of signal loss and the introduction of noise into the communication circuit. When terminated improperly, each cable is a potential source of physical layer performance degradation. It is essential that all copper media terminations be of high quality to ensure optimum performance with current and future network technologies.
UTP Cabling Standards
UTP cabling conforms to the standards established jointly by the TIA/EIA. Specifically, TIA/EIA-568 stipulates the commercial cabling standards for LAN installations and is the standard most commonly used in LAN cabling environments. Some of the elements defined are: Cable types Cable lengths Connectors Cable termination Methods of testing cable The electrical characteristics of copper cabling are defined by the Institute of Electrical and Electronics Engineers (IEEE). IEEE rates UTP cabling according to its performance. Cables are placed into categories based on their ability to carry higher bandwidth rates. For example, Category 5 (Cat5) cable is used commonly in 100BASE-TX Fast Ethernet installations. Other categories include Enhanced Category 5 (Cat5e) cable, Category 6 (Cat6), and Category 6a. Cables in higher categories are designed and constructed to support higher data rates. As new gigabit speed Ethernet technologies are being developed and adopted, Cat5e is now the minimally acceptable cable type, with Cat6 being the recommended type for new building installations.
What is Unshielded Twisted Pair (UTP)?
Unshielded twisted-pair (UTP) cabling is the most common networking media. UTP cabling, terminated with RJ-45 connectors, is used for interconnecting network hosts with intermediate networking devices, such as switches and routers.
Which layer is responsible for process to process delivery?
Very Important Point: The transport layer is responsible for the process to process delivery of the entire message. A process is an application program running on a system. The transport layer ensures that the whole message arrives at the receiver intact and in order.
What is the difference between single mode and multimode fiber?
What is the difference between multimode and single mode fiber? Multimode fiber has a relatively large light carrying core, usually 62.5 microns or larger in diameter. ... Single-mode fiber has a small light carrying core of 8 to 10 microns in diameter.
What is difference between WiFi and WiMAX?
Whereas WiFi is for local hotspots, WiMax has medium bandwidth as well as ten Mgs of bandwidth for a local LAN connection. ... Basically, WiFi is access to a LAN, and while WiMax can be used for that, one of its most beneficial uses is as a fixed wireless solution.
What is WiMAX service?
WiMAX (Worldwide Interoperability for Microwave Access) is a family of wireless broadband communication standards based on the IEEE 802.16 set of standards, which provide multiple physical layer (PHY) and Media Access Control (MAC) options.
Bluetooth (WPAN)
Wireless Personal Area Network (PAN) technology that transmits signals over short distances between cell phones, computers, and other devices
What is a wireless media?
Wireless is an encompassing term that describes numerous communication technologies that rely on a wireless signal to send data rather than using a physical medium (often a wire). In wireless transmission, the medium used is the air, through electromagnetic, radio and microwave signals.
Properties of Wireless Media
Wireless media carry electromagnetic signals that represent the binary digits of data communications using radio or microwave frequencies. Wireless media provides the greatest mobility options of all media, and the number of wireless-enabled devices continues to increase. As network bandwidth options increase, wireless is quickly gaining in popularity in enterprise networks. Wireless does have some areas of concern, including: Coverage area: Wireless data communication technologies work well in open environments. However, certain construction materials used in buildings and structures, and the local terrain, will limit the effective coverage. Interference: Wireless is susceptible to interference and can be disrupted by such common devices as household cordless phones, some types of fluorescent lights, microwave ovens, and other wireless communications. Security: Wireless communication coverage requires no access to a physical strand of media. Therefore, devices and users, not authorized for access to the network, can gain access to the transmission. Network security is a major component of wireless network administration. Shared medium: WLANs operate in half-duplex, which means only one device can send or receive at a time. The wireless medium is shared amongst all wireless users. The more users needing to access the WLAN simultaneously, results in less bandwidth for each user. wireless is increasing in popularity for desktop connectivity, copper and fiber are the most popular physical layer media for network deployments.
What is the range of WiMAX?
about 100 feet The biggest difference isn't speed; it's distance. WiMAX outdistances WiFi by miles. WiFi's range is about 100 feet (30 m). WiMAX will blanket a radius of 30 miles (50 km) with wireless access.
Wireless LAN (WLAN)
common wireless data implementation is enabling devices to connect wirelessly via a LAN. In general, a wireless LAN requires the following network devices: Wireless Access Point (AP): Concentrates the wireless signals from users and connects to the existing copper-based network infrastructure, such as Ethernet. Home and small business wireless routers integrate the functions of a router, switch, and access point into one device as shown in the figure. Wireless NIC adapters: Provide wireless communication capability to each network host. As the technology has developed, a number of WLAN Ethernet-based standards have emerged. Care needs to be taken in purchasing wireless devices to ensure compatibility and interoperability. The benefits of wireless data communications technologies are evident, especially the savings on costly premises wiring and the convenience of host mobility. Network administrators need to develop and apply stringent security policies and processes to protect wireless LANs from unauthorized access and damage.
Data Link Layer Standards
nlike the protocols of the upper layers of the TCP/IP suite, data link layer protocols are generally not defined by Request for Comments (RFCs). Although the Internet Engineering Task Force (IETF) maintains the functional protocols and services for the TCP/IP protocol suite in the upper layers, the IETF does not define the functions and operation of that model's network access layer. Engineering organizations that define open standards and protocols that apply to the network access layer include: Institute of Electrical and Electronics Engineers (IEEE) International Telecommunication Union (ITU) International Organization for Standardization (ISO) American National Standards Institute (ANSI)
straight trip connector (ST)
the connector locks securely with a twist on/off bayonet style magnetism.
why do we test a UTP cable?
to test for the following parameters: Wire map Cable length Signal loss due to attenuation Crosstalk
Physical Layer Terminology
wireless - media that uses pattens of microwaves to represent bits. Bandwidth - the capacity of medium of carry data. fiber optic - media that uses pattens of light to represent bits. thoughput - a measure of transfer of bits across the media. copper - media that uses electrical pulses to represent bits.
Fiber-optic cabling
Uses glass or plastic fiber to carry information as light pulses
What are the features of Bluetooth?
Features of Bluetooth Technology. Bluetooth allows two devices to be connected to each other wirelessly. The most common use of Bluetooth technology is in hands-free devices such as headsets used with mobile phones.
What is a good throughput?
In general terms, throughput is the maximum rate of production or the maximum rate at which something can be processed. When used in the context of communication networks, such as Ethernet or packet radio, throughput or network throughput is the rate of successful message delivery over a communication channel.
What are the issues of data link layer?
Issues in Data Link Layer. The main job of the data link layer is to make the communication on the physical link reliable & efficient. Issues, - Provide interface to the network layer services. - Framing - Flow Control - Error Control - Synchronization - Link Configuration Control.
What is a UTP connector?
It is a type of cable that is used for networking communication. They are fast in transmitting data, but susceptible to electro magnetic interference. RJ45 connectors accept UTP cables. UTP stands for unshielded twisted pair cable ,the connector use for UTP is RJ 45 (RJ stands for registered jack).
What are the 2 types of fiber optic cable?
Uses glass or plastic fiber to carry information as light pulses
What's Bluetooth used for?
A Bluetooth® device works by using radio waves instead of wires or cables to connect with your cell phone, smartphone or computer. Bluetooth is a wireless short-range communications technology standard found in millions of products we use every day - including headsets, smartphones, laptops and portable speakers.
How do you measure throughput?
A benchmark can be used to measure throughput. In data transmission, network throughput is the amount of data moved successfully from one place to another in a given time period, and typically measured in bits per second (bps), as in megabits per second (Mbps) or gigabits per second (Gbps).
What causes crosstalk?
Crosstalk is a disturbance caused by the electric or magnetic fields of one telecommunication signal affecting a signal in an adjacent circuit. In an telephone circuit, crosstalk can result in your hearing part of a voice conversation from another circuit.
Who invented fiber optics?
Narinder Singh Kapany In 1952, UK based physicist Narinder Singh Kapany invented the first actual fiber optical cable based on John Tyndall's experiments three decades earlier.
What is the difference between ST and SC fiber optic connectors?
SC stands for subscriber connector and is a standard-duplex fiber-optic connector with a square molded plastic body and push-pull locking features. ... ST connectors are more common than SC connectors. You can generally use SC and ST connectors with either single-mode or multimode fiber-optic cabling.
What are the sublayers of data link layer?
The data link layer (Layer 2) of the OSI model actually consists of two sublayers: the Media Access Control (MAC) sublayer and the Logical Link Control (LLC) sublayer. ... Physical addressing for network connections exists at the data link layer. The data link layer combines data bits into entities called frames.
What are two advantages of wireless communication?
Wireless - Advantages. Wireless communication involves transfer of information without any physical connection between two or more points. Because of this absence of any 'physical infrastructure', wireless communication has certain advantages. This would often include collapsing distance or space.
How is data transmitted wirelessly?
Wireless Network Infrastructure Required to Transmit Data. The process of sending and receiving radio signals through wireless networks involves two devices, the transmitter and the receiver.
Duplex multimode LC connectors
like a LC) simplex conductor but uses a duplex connector
subscriber connectors (SC)
often referred to square connector or standard conductor. the conductor is widely adapable to LAN and WAN connector that push-pulls magnetism to ensure positive insertion. it is used with both multimode and single mode fiber.
What is crosstalk and how does it affect performance?
rosstalk is a disturbance caused by the electric or magnetic fields of one telecommunication signal affecting a signal in an adjacent circuit . In an telephone circuit, crosstalk can result in your hearing part of a voice conversation from another circuit.
